Symposium Organizers
Rein V. Ulijn University of Strathclyde
Molly M. Stevens Imperial College London
Rajesh R. Naik Air Force Research Laboratory
Phillip B. Messersmith Northwestern University
PP1: Biointerfaces
Session Chairs
Tuesday PM, April 06, 2010
Room 3022 (Moscone West)
9:30 AM - **PP1.1
Biomimetic Functionality of PEG-gated Nanopores Derived from Binding Interactions With Associated Antibodies.
Janne Hyoetylae 1 , Jie Deng 2 , Roderick Lim 1
1 Biozentrum and the Swiss Nanoscience Institute, University of Basel, Basel Switzerland, 2 , Institute of Materials Research and Engineering, Singapore Singapore
Show AbstractCellular nanomachines are touted to offer novel technological strategies provided that their mechanisms can be replicated outside the cell. This provides the driving impetus in our lab to resolve the modus operandi of the nuclear pore complex (NPC), which regulates macromolecular traffic between the nucleus and the cytoplasm. As a physical pore ∼50 nm in diameter, the biological marvel of the NPC lies in its ability to restrict or promote cargo translocation via biochemical selectivity and not size exclusion per se. Moreover, unlike synthetic nanopores, the NPC does not clog in vivo - in spite of the molecular complexity of the cellular environment. Towards this goal, we have tethered the key NPC proteins (i.e., natively unfolded phenylalanine-glycine (FG)-rich domains) to nanostructured pores so as to mimic the size and topography of the NPC. In doing so, we have correlated the nanomechanical responses of the FG-domains to the biochemical interactions governing nuclear transport using a combined fluorescence/atomic force microscope (AFM). Our results - heuristically validated within individual NPCs in situ - show that the FG-domains resemble a polymer brush (i.e., barrier) which reversibly collapses during (un)binding interactions with transport receptors that ferry cargo in and out of the nucleus.To test the generality of such a mechanism, we have substituted the FG-domains and transport receptors with polyethylene glycol (PEG) and PEG-associated IgG antibodies (anti-PEG), respectively. Here, our selection of PEG is based on its non-fouling properties and relative molecular inertness. True to form, the PEG gives rise to a brush-like barrier that repels non-specific molecules from the pore periphery. In the presence of other non-specific molecules, we find that only the anti-PEG is able to access the pore via specific binding interactions with the PEG chains. Our finding is underscored by observing that the anti-PEG can act as cargo-specific molecular chaperones able to ferry secondary antibodies into the pore. In closing, our results highlight possible functionalities in which polymer brushes can be used as non-fouling, selective gates in nanoporous membranes. On a technical note, the combination of nanofabrication, AFM and fluorescence allows for the direct correlation of local nanomechanical effects which result from biochemical interactions at the nanoscale.1.Lim R.Y.H and J. Deng, Interaction forces and reversible collapse of a polymer brush-gated nanopore, ACS Nano 3 2911 (2009) 2.Lim R.Y.H., et al., Nanomechanical basis of selective gating by the nuclear pore complex, Science, 2007. 318, 640. 3.Lim R.Y.H., et al., Flexible phenylalanine-glycine nucleoporins as entropic barriers to nucleocytoplasmic transport. Proc. Natl. Acad. Sci. U.S.A., 2006. 103(25): p. 9512-9517
10:00 AM - PP1.2
Two-way Communication Across Biotic-abiotic Interfaces Using Liquid Crystals.
Nicholas Abbott 1
1 Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States
Show AbstractThis presentation will describe the organization and functional properties of biological molecules (lipids and enzymes) assembled at aqueous interfaces to (water-immiscible) liquid crystals. Whereas several past investigations have established that surface-driven ordering transitions in liquid crystalline materials can be triggered by biomolecular interactions, we have recently discovered that the nematic order of a liquid crystal can also direct the organization of interfacial biomolecular adsorbates. Specifically, experimental measurements and a thermodynamic model reveal that nematic elasticity can be used to direct the lateral organization of phospho- and glycol-lipids assembled at interfaces between thermotropic liquid crystals and immiscible aqueous phases. The morphologies of the domains of the lipids induced by nematic elasticity are shown to be strongly dependent on the nature of the deformation of the liquid crystal. This study provides important insight into the physics that controls the ordering of molecules at interfaces of soft anisotropic materials, and identifies a new mechanism that can lead to two-way communication between biological molecules and soft, synthetic materials.
10:15 AM - PP1.3
Nanometer-scale Structure Effects on Interfacial Energy.
Jeffrey Kuna 1 , Kislon Voitchovsky 1 , Chetana Singh 2 , Hao Jiang 2 , Steve Mwenifumbo 4 , Pradip Ghorai 2 , Molly Stevens 4 , Sharon Glotzer 2 3 , Francesco Stellacci 1
1 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 4 Department of Materials and Institute for Biomedical Engineering, Imperial College London, London United Kingdom, 3 Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractInterfacial energy remains one of the most commonly reported and most accessible surface properties. Many surfaces of interest, namely those encountered in biological systems, are composed of multiple components each having different interfacial energies. Classically, the overall interfacial energy is treated as the compositionally weighted average of the components’ interfacial energies. This approach only considers the surface composition and, to the best of our knowledge, no formulation exists which incorporates a structural component in the expression for surface energy.Here we report evidence of a structural effect on interfacial energy observed via contact angle measurements on a series of nanoparticle films. The nanoparticles were coated with a mixture of hydrophilic and hydrophobic ligands that spontaneously phase-separate into striped domains as narrow as a single molecule. In this specific system, the structural contribution to interfacial energy can cause a deviation as large as 20% from the classically-expected linear trend. Additionally, the trend in interfacial energy is non-monotonic with respect to composition. Furthermore, the interfacial energy of the nanoparticle films was measured with a novel atomic force microscopic technique capable of evaluating interfacial energies of nanometer-scale areas. The data using this latter technique agree with the macroscopic contact angle measurements, proving that the observed deviations are due to nanoscale effects, and not simply to contact angle pinning or surface roughness contributions. Surfaces composed of the same molecules distributed in large domains demonstrated the classically expected linear relationship between composition and interfacial energy.We propose two competing effects to explain this behavior. The proposed mechanisms are based on the molecular-level behavior of liquids in contact with domains commensurate in size to the solvent molecule. The first effect draws from the theory of solubility of small hydrophobic solutes and the second from the theory of confined liquids. These effects, termed cavitation and confinement, account for size-dependent interfacial energies for hydrophobic and hydrophilic domains, respectively, when the domain size is commensurate to the solvent molecule size. We experimentally demonstrate the coexistence of these competing effects with additional contact angle measurements using aqueous salt solutions to shift the prevalence of each effect. Finally, we support the proposed effects with computer simulation results. Both effects are observed using molecular dynamics simulations and show to be closely linked to the domain size of the hydrophilic and hydrophobic patches present on the monolayer of the nanoparticle.Reference:J. J. Kuna, K. Voitchovsky, C. Singh, H. Jiang, S. Mwenifumbo, P. K. Ghorai, M. M. Stevens, S. C. Glotzer, F. Stellacci, Nature Materials 8 (10), 837-842 (2009).
10:30 AM - **PP1.4
Cell Sheet Engineering for Regenerative Medicine: Current Status of Clinical Applications.
Masayuki Yamato 1
1 Institute of Advanced Biomedical Engineering and Science, Tokyo Women's Medical University, Tokyo Japan
Show AbstractWe have developed a novel strategy for regenerative medicine to recover tissue functions by using temperature-responsive cell culture surfaces on which temperature-responsive polymer is covalently grafted by electron beam irradiation or other chemical reactions. These surfaces achieve temperature-responsive cell adhesion and detachment with no need for proteolytic enzyme such as trypsin and dispase. To overcome the limits of conventional tissue engineering methods such as the use of single-cell suspension injection and the use of biodegradable polymer scaffolds, we have applied transplantable cell sheets fabricated with temperature-responsive culture surfaces for cell delivery. Only by reducing temperature around room temperature, all the cells are harvested from the dish as a single contiguous cell sheet. Since these cell sheets retain extracellular matrix deposited during culture below them, integration to tissue or other cell sheets is observed immediately after the transplantation. Here, we show the pipelines and current status of clinical applications of regenerative medicine using cell sheet engineering. Skin and corneal defects have been treated with transplantable cell sheets fabricated on the surfaces. In bilateral cases, patients’ own oral mucosal epithelial cells are utilized as the cell source, since both eyes are damaged and no epithelial stem cells are obtained from the patients. Now, we have performed the clinical trial under EMEA (European Medicines Agency) of the corneal regenerative medicine in Europe. We expect that we will obtain the approval in 2011. Severe heart failure was also treated with cell sheets fabricated from patient’s own skeletal myoblasts. Esophageal defects after endoscopic tumor dissection have been treated by cell sheet engineering. In these cases, we also utilize patients’ own oral mucosal epithelial cells as the cell source. We expect further improvements of stimuli-responsive culture surfaces will realize the reconstruction of more complex tissues to potentially treat a wide range of diseases.References1. J. Yang, M. Yamato, T. Shimizu, H. Sekine, K. Ohashi, M. Kanzaki, T. Ohki, K. Nishida, T. Okano, Reconstruction of functional tissues with cell sheet engineering. Biomaterials. 2007;28:5033-43. 2. K. Nishida, M. Yamato, Y. Hayashida, K. Watanabe, K. Yamamoto, E. Adachi, S. Nagai, A. Kikuchi, N. Maeda, H. Watanabe, T. Okano, Y. Tano, Corneal reconstruction with tissue-engineered cell sheets composed of autologous oral mucosal epithelium. N Engl J Med. 2004;351:1187-96.3. T. Ohki, M. Yamato, D. Murakami, R. Takagi, J. Yang, H. Namiki, T. Okano, K. Takasaki, Treatment of oesophageal ulcerations using endoscopic transplantation of tissue-engineered autologous oral mucosal epithelial cell sheets in a canine model. Gut. 2006;55:1704-1710.4. T. Shimizu, H. Sekine, M. Yamato, T. Okano, Cell sheet-based myocardial tissue engineering: new hope for damaged heart rescue. Curr Pharm Des. 2009;15:2807-2814.
11:30 AM - **PP1.5
Targeted Delivery of Lipid Agents and Nanoparticles to Cancer Cells: How to Combine Chemical Reaction Equilibrium and Physical Interactions for Biological Activity.
Igal Szleifer 1 , Rikkert Nap 1
1 Biomedical Engineering, Northwestern University, Evanston,, Illinois, United States
Show AbstractOne of the major challenges in drug delivery is the ability to target exclusively sick cells without interacting with healthy cells. This is particularly important for cancer drug delivery. In this presentation we show how we can take advantage of the modifications that occur on the plasma membrane of cancer cells to target surface modified nanoparticles. The basic idea is to take advantage of the over-expressed receptors and the different lipid composition of the plasma membrane in (some) cancer cells. To this end we show, as a proof of concept, how modifying the surface of the nanoparticles with binary mixtures of short polymers can increase the binding to the cells by orders of magnitude. One of the polymers in the mixture is aimed at protecting the nanoparticle and the other is a polybase with a functional ligand as its end-group that specific targets the overexpressed receptors in the cancer cell. We show how the combination of electrostatic interactions, specific binding, acid-base equilibrium and molecular organization in the nanoparticle and on the lipid layer provides for a non-trivial synergetic effect with highly improved binding capabilities. We will show how the approach of the nanoparticle to the lipid layer results in a highly inhomogeneous segregation of lipids in the cell membrane and of polymers in the nanoparticle. The molecular segregation can be used as a tool not only for drug delivery but also for molecular recognition of surface domains. The complex non-additive interplay between chemical reactions and physical interactions in highly inhomogeneous environments that we predict points out to the need to develop novel intuition for these strongly coupled systems. The relevance for the fundamental understanding of processes in cell biology as well as in the design of responsive materials will be discussed.
12:00 PM - PP1.6
AFM Force Spectroscopy on TAT Membrane Penetration.
Elizabeth Hager-Barnard 1 , Benjamin Almquist 1 , Nicholas Melosh 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States
Show AbstractWe present a study of the interactions between cell-penetrating peptides (CPPs) and lipid stacks using Atomic Force Microscopy (AFM). Understanding how CPPs can pass through cell membranes is critical for designing optimal drug delivery agents. While CPPs like HIV-TAT, a positively charged 9-mer with six arginine groups, have been widely studied, their precise penetration mechanisms are still not well understood. New experimental methods are needed to characterize CPP behavior and determine whether TAT can penetrate bilayers directly. Direct measurement of TAT-lipid mechanics during the actual translocation event is an ideal method to elucidate the interaction forces, mechanisms and timescales of membrane penetration. We used AFM force spectroscopy on lipid bilayer stacks with TAT ‘δ-functionalized’ probes to monitor both the TAT position within a single bilayer and the associated force with microsecond resolution. To our knowledge these results present the first direct quantification of the mechanics of TAT penetration and the first demonstration that the different regimes identified in dynamic force spectroscopy correspond to distinct mechanisms. The AFM results show that TAT by itself does indeed alter the membrane structure. Additional results from lysine oligomer probes indicate that TAT’s arginine groups are key to these TAT-lipid interactions, since probes functionalized with a lysine oligomer did not induce bilayer thinning. Though TAT strongly interacts with the lipid bilayer, the energy barrier for TAT penetration is actually 38kT higher than for probes functionalized with 11-mercaptoundecanoic acid. These results corroborate many of the conclusions from molecular dynamics simulations on TAT-lipid systems, which indicate that TAT does not penetrate bilayers directly.
12:15 PM - PP1.7
Biohesion – Coupling Nanomaterials and Biologicals Using GEPI.
Mehmet Sarikaya 1 , E.Emre Oren 1 , Candan Tamerler 1 2
1 Materials Science & Engineering, University of Washington, Seattle, Washington, United States, 2 Molecular Biology & Genetics, Istanbul Technical University, Istanbul Turkey
Show AbstractIn biology, molecular recognition is the basis of all interactions including those between antigen-antibody, anyzme-substrate, and protein-lipid membrane, in which proteins play the central role. As molecular and ionic transporters, functional scaffolds, cell signalers, and transcription factors regulating genes, proteins are the workhorses of life. With the recent developments of nanoscale engineering in physical sciences and the advances in molecular biology, we are combining genetic tools with synthetic nanoscale constructs in creating a hybrid methodology, molecular biomimetics. Here, using biology as a guide and adapting bioschemes including combinatorial mutagenesis, bioinformatics, and recombinant DNA technologies, we select, design and tailor short peptides (7-60 amino acids) with specific binding to and assembly on functional solid materials and use them a building blocks in technology and medicine. GEPI, genetically engineered peptides for inorganics, are a new class of molecules whose properties could be enhanced through engineered evolution. Based on the fundamental principles of genome-based design, molecular recognition, and self-assembly, we can now engineer peptides with specific sequences to control adhesion of biological entities to solids (biohesion) and use them as nucleators, catalyzers, growth modifiers, molecular linkers and erector sets, simply as fundamental utilities for nano- and bionano-technology. We will review the recent developments in our collaborative research groups in this rapidly developing polydisciplinary field, focusing on the utility of solid-binding peptides in: i. Functional biomaterialization for nanotechnology (nanoparticles and thin films) and regenerative medicine (scaffolds towards tissue regeneration), ii. Bi-functional genetic fusion constructs (enzymes and cell signalers); iii. Molecular erectors for directed and targeted self assembly of biomolecular/nanoparticle multicomponent entities towards imaging and sensing for nanophotonics and diagnostics nanodevices. The research is supported mainly, by, NSF-MRSEC, and also by NSF-BioMat, NSF-IRES, and NIH programs.
12:30 PM - PP1.8
Enhanced Photogenerated Carrier Collection in Hybrid CdSe/Gold Films Using Phage-templated Nanowires.
Elaine Haberer 1 3 , John Joo 2 4 , Juan Hodelin 1 5 , Evelyn Hu 1 4
1 California NanoSystems Institute, Unversity of California, Santa Barbara, Santa Barbara, California, United States, 3 Electrical Engineering Department, University of California, Riverside, Riverside, California, United States, 2 Materials Department, Unversity of California, Santa Barbara, Santa Barbara, California, United States, 4 School of Engineering and Applied Sciences , Harvard University, Cambridge, Massachusetts, United States, 5 Physical Optics Corporation, Physical Optics Corporation, Torrance, California, United States
Show AbstractSemiconductor nanocrystalline materials are attractive materials for the next generation of photovoltaic devices. These nano-scale materials exhibit size-tunable quantum-confinement effects which offer a unique ability to control the material absorption wavelength. Furthermore, unlike epitaxial semiconductor materials, semiconductor nanocrystalline films are not limited by substrate lattice-matching requirements and they can be solution-synthesized at a lower cost. Nanocrystalline materials have demonstrated efficient photon absorption and carrier generation; however extraction of the photogenerated carriers is frustrated by the low material conductivity. Hybrid semiconductor nanocrystal-nanowire or nanotube materials are one approach to improving carrier collection in quantum-confined materials. In these materials, 1-D nanostructures such as nanowires or nanotubes (semiconducting or metallic) which have measurable conductivity are decorated with 0-D semiconductor nanocrystals. The intimate contact of the nanocrystals with the conductive nanowire or nanotube allows carriers to be more readily separated and collected along the length of the nanowire or nanotube thus improving quasi-1D transport. In this work, we explore the effect of the nanowire conductivity on photogenerated carrier extraction in films of bio-templated gold nanowires coated with nanocrystalline CdSe using chemical bath deposition (CBD). We are able to vary the conductivity of the gold nanowires over several orders of magnitude, resulting in very different photoconductive signatures from the hybrid films. M13 bacteriophages, genetically modified to bind to Au, were deposited on SiO2/Si substrates pre-patterned with contact pads and incubated in a gold colloid solution. The Au NPs selectively bound to the bacteriophages and were subsequently used as seeds for electroless deposition of gold. The resulting nanowires ranged in diameter from 20 to 60 nm and conductivity from 10-3 S/m to 10 S/m. Using CBD, a nanocrystalline CdSe film was selectively deposited on the nanowires to create hybrid CdSe/gold films. Photocurrent measurements were performed on the hybrid CdSe/gold films as well as on control samples of CBD CdSe films. Photocurrent action spectra were used to confirm that the photocurrent within the films resulted predominantly from the CdSe band edge absorption. Broad band photoconductivity measurements revealed that the introduction of gold nanowires into the CdSe film resulted in as much as a 500x increase in photocurrent collection. The observed increase in collected photocurrent could be varied by two orders of magnitude by controlling the resistance of the underlying gold nanowires. The ratio of photocurrent to dark current was similarly modified. These studies are a first step to understanding the optimization of carrier extraction from the semiconductor-metal nanostructures.
12:45 PM - PP1.9
The Generation of the Antibodies With High Affinity for Inorganic Nanomaterials by Peptide-grafting and Molecular Evolutionary Methods.
Mitsuo Umetsu 1 2 3 , Takamitsu Hattori 1 , Satoshi Ohara 4 , Takeshi Nakanishi 1 , Izumi Kumagai 1
1 Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai Japan, 2 Center of Interdisciplinary Research, Tohoku University, Sendai Japan, 3 PRESTO, JST, Tokyo Japan, 4 Joining and Welding Research Institute, Osaka University, Ibaraki Japan
Show AbstractRecent advance in biotechnology enables us to apply the technology in various fields based on organic and inorganic materials. In the field of material engineering, gene and protein engineering is coupled with the technology of downsizing materials to nano-sized particles for the innovation of sensor and therapeutic devices, and bio-mineralization are attractive for hybrid materials because strictly shape-controlled inorganic materials are synthesized at room temperature in /on cell. We have innovated the peptide and antibodies as integrated interface molecules for hybrid organic-inorganic-biomolecules materials. In this study, we describe how to innovate the antibodies with high affinity for the surface of bulk materials, and we show the potential of their molecules in the field of bionanotechnology.
In general, antibody have high affinity at the dissociate constant of ~nM, so that its function can be superior to that of a low-molecular weight peptide showing relatively low affinity to its target surface; however, poor immunogenic potential of solid materials and limited library diversity make selecting antibodies difficult by general in vivo and in vitro selection methods, respectively. Here, we fabricate the antibody fragment with high affinity for inorganic materials by the combination of grafting and molecular evolution techniques. We show that this bottom-up antibodies evolution method is a convenient and reliable mean to obtain an antibody fragment with high affinity for inorganic materials.
PP2: Biomaterials
Session Chairs
Tuesday PM, April 06, 2010
Room 3022 (Moscone West)
2:30 PM - **PP2.1
Synthetic Viruses for Novel Tissue Regenerating Materials.
Seung-Wuk Lee 1
1 Bioengineering , University of California, Berkeley, Berkeley, California, United States
Show AbstractA fundamental challenge in bio-nanoscience is to identify an active building block that can perform highly selective functions with remarkable precision based on specific recognition, programmable self-assembly, and non-toxic biocompatibility. We have developed radically novel synthetic viruses which can control and guide cell behavior for tissue engineering materials using genetically engineered M13 bacteriophage (viruses). Filamentous M13 phage have several qualities that make them attractive candidates for use as building blocks in tissue engineering scaffolds. The M13 phage has a monodisperse, long-rod shape that enables its self-assembly into directionally ordered liquid crystalline structures. Through genetic engineering, a high-density array of peptide-based signaling molecules and therapeutic materials can simultaneously be displayed on its major and minor coat proteins. We have engineered M13 bacteriophage to display various eptides that promote cell interaction (IKVAV, RGD) on all 2700 copies of major coat proteins. We have verified that these viruses are biocompatible to neuronal cells using viability assays. We have shown that neural progenitor cells can both proliferate and ifferentiate when grown on viral surfaces and that there is a preference of specific cell interaction with the RGD- and IKVAV-peptide engineered phages over wildtype phage. Utilizing SEM and fluorescent-immunostaining microscopy we have demonstrated that such engineered phage can self assemble into directionally organized structures, which in turn dictate the alignment and direction of cell growth in 2D and 3D tissue engineering matrices. These smart and novel engineered virus-based materials can be used as promising novel substrates for neural cell growth. The success of these radically novel materials will enable to manipulate cell behavior at the molecular level and regenerating various tissues, and possibly lead to the discovery of cures for challenging diseases such as spinal cord injuries.
3:00 PM - PP2.2
Growth and Differentiation of Retinal Progenitor Cells on Micro- and Nano-structured Polycaprolactone Thin Films.
Mark Steedman 1 2 , Marc Yago 1 2 3 , Daniel Bernards 1 2 , Tejal Desai 1 2
1 Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, California, United States, 2 Physiology, University of California San Francisco, San Francisco, California, United States, 3 Biophysics, University of California San Francisco, San Francisco, California, United States
Show AbstractMicro- and nano-structured surfaces have been shown to influence stem and progenitor cell fates and are increasingly being studied for tissue engineering applications. Here, we investigate the growth and differentiation of retinal progenitor cells (RPCs) on polycaprolactone (PCL) thin films with micro- and nano-topographical features. Due to the retina’s inability to replace photoreceptors lost during retinal degeneration, significant interest has been placed in methods to implant replacement cells. Polymer scaffolds are increasingly being studied as vehicles for cellular delivery to degenerated retinas. Previously, we fabricated poly(methyl methacrylate) thin film scaffolds that increased survival and integration of implanted RPCs. These scaffolds also minimized the trauma and cellular response associated with implantation of foreign bodies into mouse eyes, but they were made from a non-degradable material. Ideally, a scaffold would not require removal and instead would degrade, resulting in a regenerated healthy retina.The growth and differentiation of RPCs grown on PCL thin films is investigated. Through a combination of techniques including scanning electron microscopy, real-time quantitative polymerase chain reaction, and western blotting, cellular differentiation is demonstrated, including enhanced differentiation due to scaffold topography. We believe retinal tissue engineering using RPCs and PCL is a promising approach to treating degenerative diseases of the retina.
3:15 PM - PP2.3
Highly Conductive, Biomimetic Gel Electrodes by Co-electrodeposition of Conducting Polymer and Hydrogel for Chronic Neural Interfacing.
Sarah Richardson-Burns 1 , Jeffrey Hendricks 1 , Andrew Sereno 1 2 , Zachary King 1 3 , David Martin 1 4
1 , Biotectix LLC, Ann Arbor, Michigan, United States, 2 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 4 Materials Science & Engineering, University of Delaware, Newark, Delaware, United States
Show AbstractImplantable bio-interfacing devices that mimic the mechanical and electrical properties of tissues are expected to provide the greatest potential for future motor prostheses, visual prostheses, auditory prostheses, and targeted treatment of neurological disorders. Using co-electrodeposition of conducting polymer and hydrogels onto metal substrates, we have developed low impedance, biomimetic gel electrodes that are extremely soft and porous with high effective surface areas. The multi-functional conductive gels facilitate both ionic and electronic charge transfer, provide a scaffold for cell and tissue attachment, buffer the tissue from the rigid components of the device, and can extend the electrode bringing it physically closer to target cells. The novel gel electrodes we describe here are comprised of combinations of poly 3,4-ethylene dioxythiophene (PEDOT) and hydrogels (alginate, poly ethyleneglycol, and/or poly 2-hydroxyethyl methacrylate) with biocompatible surfactants. These gel electrodes have been deployed on clinical-grade multi-electrode array cochlear implants and peripheral nerve cuff electrodes. Application of the gel electrode material on the surface of the platinum electrode sites of clinical devices decreased the in vitro electrode impedance by over 90% at frequencies of 1 – 1,000 Hz. Particularly important for in vivo charge delivery and tissue-interfacing applications, the PEDOT gel electrodes provided significantly lower voltage transients during biphasic pulsatile stimulation, reducing voltage excursions by more than 80 %, rendering the electrodes more efficient and safer for tissues. The charge storage capacity, related to the amount of charge that can be delivered for a given time period and voltage range was increased by 100-1000 %, usually delivering 25-50 mC/cm2 or more. The elastic moduli of the new PEDOT gel electrodes was 1.7 – 2.3 GPa when dehydrated, less than 1 % of the typical metal modulus. In addition, due in part to its inherent hydrophilicity and surface charge, the hydrogel of the gel electrode provides a substrate that resists non-specific protein adsorption which is one of the first steps toward problematic biofouling and formation of high impedance scar tissue. If desired, the gel electrodes can also be used to deliver growth factors, adhesion molecules, or anti-inflammatory steroids to direct the tissue response near the implanted electrode. In summary, the biomimetic conducting polymer-hydrogel electrodes that we present here provide the ability to more safely and effectively interface clinical biomedical devices with nervous system tissues for chronic neuromodulation and neural prosthetics applications through their superior electrical, mechanical, and biological properties.
3:30 PM - PP2.4
Bioinstructive Hydrogels for Applications in Neural Cell Engineering.
Tobias Wolfram 1 , Ilia Louban 2 3 , Sebastian Kruss 2 3 , Joachim Spatz 2 3
1 Research Group Biomedical Applications of Engineered Interfaces, Max-Planck-Institute Stuttgart, Stuttgart Germany, 2 New Materials and Biosystems, Max-Planck-Institute Stuttgart, Stuttgart Germany, 3 Biophysical Chemistry, University of Heidelberg, Heidelberg Germany
Show AbstractThe development of bioinstructive materials for research and clinical applications in biology and medicine holds great promise to extend our understanding of cellular interactions with biomedical surfaces.In the present study, we used nanoengineered gold particle arrays on substrates with different physical properties. Elastic polyethylene glycol (PEG) hydrogels were used as a platform with tunable stiffness properties and compared to glass substrates. Gold particles were functionalized either directly with peptides containing a thiol group or indirectly with protein domains via a Nitrilotriacetic acid (NTA)-linker system. This experimental setup was used to investigate neural cell adhesion, migration, neurite outgrowth, and cell binding in co-culture systems.Nanostructured hydrogels were generated with interparticle distances of approximately 50 nm and 100 nm measured by cryo-SEM. In order to quantify the mechanical properties of PEG-DA hydrogels (Young’s modulus EY) we performed AFM indentation measurements based on the Hertz model. PEG-hydrogels were used in this work with EY ≈0.6, 1, 2, 7, 10, 12, and 14 kPa as well as 6 MPa.Cell adhesion on nanostructured gels were visualized and analyzed with cryo-SEM and static adhesion assays. On substrates with 50 nm interparticle distances, cell adhesion was observed for up to two weeks for neural cell lines as well as for fibroblasts. Fibroblast cell lines adhere around two times better to RGD functionalized PEG-hydrogels in mono-cell cultures when compared to neuroblastoma cell lines. For IKVAV decorated PEG-hydrogels neuroblastoma cell adhesion was increased to a comparable level of fibroblast adhesion on similar substrates. In co-culture systems a significant lower amount of fibroblast cells adhere to IKVAV substrates and vice versa a higher number of N2a cells (2,5fold) were detected on the surface. Lower elasticity (<1kPa) increased the neural cell number to around 5fold over fibroblasts. Neurite length was increased on substrates with lower elasticity independently from functionalization. Neurite initiation was independent from substrate elasticity but 4fold more cells with neurites were observed on IKVAV functionalized hydrogels. In conclusion, neural cell adhesion and neurite formation depends on substrate elasticity as well as biofunctionalization and particle density. Substrates can be tuned to direct the adhesion of neural cell types from co-culture systems. Hydrogels deployed in this study might be useful in the future for the development of novel bio-mimetic surfaces for the prolongation of specific cell types in defined implants.
3:45 PM - PP2.5
Microgel Mechanics in Biological Nano-environments.
Grant Hendrickson 1 , L. Lyon 1
1 Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractBiomaterial applications such as drug delivery, contrast agent design, and tissue engineering depend on both chemical and physical interactions with the biological environments. Often design of the material is based on its ability to interact chemically with proteins or cells of interest by incorporating targeting ligands or peptides for cell recruitment. Here we present the results of experiments been designed to study the mechanical interactions of a biomaterial with the surrounding environment. As a specific example, the nano-sized pores in the Bowman’s capsule in a mammalian kidney act as a gateway to excretion of material from the blood stream. It is our goal to understand the critical parameters for passage though these small (~ 8 nm) pores under small pressure differentials (~ 40 mmHg). This has been well studied for rigid macromolecules (e.g. proteins), however, the strict dimensions of these biological nanoenvironments may not apply to polymeric species with relatively low connectivity. In fact our studies show that hydrogel microparticles (microgels) with dilute solution diameters of 10-fold larger than the size of the pore are deformable enough to pass through the pore under physiological relevant pressures. The influence of microgel cross-link density, swelling degree, size, and concentration on pore passage will be discussed. These studies potentially shed light on the role of molecule cooperatively in renal filtration as well as the design of biomaterials for efficient clearance from the bloodstream without the need for biodegradation.
4:00 PM - PP2 Biomaterials
Break
4:15 PM - **PP2.6
Mechanically Robust Stimuli Responsive Macroporous Hydrogels.
Eun Seok Gil 1 , Sang Hyug Park 1 , Lee Tien 1 , David Kaplan 1
1 Biomedical Engineering, Tufts University, Medford, Massachusetts, United States
Show AbstractMechanically robust polymeric actuators were prepared with functionalized macroporous soft materials by combining silk protein and synthetic poly(N-isopropylacrylamide (PNIAPPm) to form semi-interpenetrating networks. The materials were prepared with pore diameters in the hundreds of micron scale. Features of both polymers related to dynamic materials and structures were utilized, with chemically cross-linked PNIPAAm networks providing stimuli-response and the silk the mechanical features. The silk interpenetrating network was formed by inducing protein β-sheet crystallinity in situ for physical crosslinks, improving expansion force. The macroporous hybrid hydrogels showed enhanced thermal-responsive properties in comparison to pure PNIPAAm hydrogels, nonporous silk/PNIPAAm hybrid hydrogels and previously reported macroporous PNIPAAm hydrogels. These new systems reach near equilibrium sizes in shrunken/swollen states in less than a minute, with the structural features providing improved actuation rates due to the macroporous transport and the mechanically robust silk network dominated by nanoscale crystalline crosslinks. Confocal images of the hydrated hydrogels around the lower critical solution temperature (LCST) revealed macropores that could be used to track changes in the real time morphology upon thermal stimulus. The material system transformed from a macroporous to a nonporous structure upon enzymatic degradation. To extend the utility of the system, an affinity platform for a switchable or tunable system was developed by immobilizing biotin and avidin on the macropore surfaces.
4:45 PM - PP2.7
Patterned Protein Functionalization Creates Defined Mono and Multi-layered Cell Clusters Towards the Development of a Bioengineered Artificial Pancreas.
Adam Mendelsohn 1 , Tejal Desai 1 2
1 Joint Graduate Group in Bioengineering, UCSF/UC Berkeley, San Francisco, California, United States, 2 Bioengineering and Therapeutic Sciences, UCSF, San Francisco, California, United States
Show AbstractIn the treatment of type I diabetes, there is significant effort towards development of a therapy that provides effective blood-glucose homeostasis without requiring frequent patient action. Current standard of care treatments all require frequent needle-pricks for blood-glucose detection or glucose sensor calibration in addition to precise insulin delivery to achieve effective disease management. Transplantation of insulin-secreting pancreatic β-cell clusters or islets promises to obviate the need for needle- pricks and insulin delivery devices to provide the patient with an effective cure. The majority of therapies under development attempt to transplant human cadaver islets which after removal from the dense network of blood vessels in a healthy pancreas are often too large to maintain cell viability on the inside of large clusters. As a result, control over the size of transplanted clusters has recently emerged as an important factor determining clinical efficacy. The goal of this work is to provide a method for creating cell clusters of precisely defined dimensions for transplantation and to evaluate the effect that cluster size has on function. In this work, we functionalized glass cover slips with an aldehyde through a step-by-step covalent attachment of self-assembled monolayers. Extracellular matrix proteins that facilitate cell adhesion were covalently attached in defined areas through microcontact printing. The remaining exposed aldehydes were then covalently attached to mPEG-amine which inhibits cell attachment. The surfaces were characterized with water contact angle measurements, x-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and semi-quantitative fluorescence microscopy. 20-120 µm square protein patterns directed the assembly of monolayer cell clusters confined to the same area at low cell seeding densities, and multi-layered cell clusters at higher cell seeding densities. Semi-quantitative immunocytochemistry after glucose-stimulated insulin secretion revealed greater normalized insulin production from larger 2D clusters as well as multi-layered vs. mono-layered clusters confined to the same 2D area. Cluster sizes which exhibit optimal insulin production and viability can be removed from the surface for transplantation. This work demonstrates that patterned protein functionalization results in precisely defined 2D and 3D cell clusters that may contribute towards the development of a clinically successful artificial pancreas for treating type I diabetes.
5:00 PM - PP2.8
Attachment of Functional ``Backpacks” for Cellular Aggregation.
Albert Swiston 1 , Darrell Irvine 1 3 , Robert Cohen 2 , Michael Rubner 1
1 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States, 3 Biological Engineering, MIT, Cambridge, Massachusetts, United States, 2 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractWe have demonstrated that multi-functional “backpacks” built from polyelectrolyte multilayers (PEM) films can be attached to living immune system cells. Fabricated using standard photolithographic techniques, 7 micron diameter backpacks are built on a glass surface and consists of 3 distinct regions. The first is a releasable region comprised of a poly(methacrylic acid)/poly(vinylpyrrolidone) hydrogen-bonded multilayer that will dissolve above pH 6.4 and release the backpack from the substrate. The next region is the payload and consists of a PLGA/hydrophobic dye strata and Fe3O4 nanoparticle/poly(allylamine hydrochloride) layer. This renders the backpacks magnetic, fluorescent, and partially hydrolysable at physiological conditions. Last, a cell-adhesive outer face is chosen to anchor the backpack to the membrane. We used hyaluronic acid (HA)-containing PEMs to anchor backpacks to B-lymphocytes, since HA is the ligand for CD44, a surface receptor found on these cells. When backpacks are released from the surface and injected into a cell solution, cells will form aggregates as they attach to one or more backpacks. The size of these aggregates is determined both by the size of the backpack and the ratio of backpacks to cells. We show that these aggregates can be forced through small pores (to mimic extravasation), which dissociates the aggregates but does not remove the backpacks from the surfaces of cells. Since these backpacks do not completely occlude the cellular surface from the environment, this technique allows payloads to be attached to a cell that is still free to perform its native functions requiring intimate environmental interaction. We will discuss how this approach has potential applications in bioimaging, single-cell functionalization, immune system and tissue engineering, and cell-based therapeutics.
5:15 PM - PP2.9
A Novel Family of Amphiphilic Glycopolymers Synthesized Based on Controlled Ring-opening Polymerization of Functionalized Cyclic Carbonates and Their Application in Drug Delivery.
Jeremy P. K. Tan 1 , Fabian Suriano 2 , Nikken Wiradharma 1 , Alshakim Nelsonc 3 , Philippe Dubois 2 , James L. Hedrick 3 , Yi-Yan Yang 1
1 , Institute of Bioengineering and Nanotechnology, Singapore Singapore, 2 Center of Innovation and Research in Materials and Polymers (CIRMAP), Laboratory of Polymeric and Composite Materials, University of Mons, Mons Belgium, 3 , IBM Almaden Research Center, San Jose, California, United States
Show AbstractBiocompatible and biodegradable polymers which assemble into well-defined nanostructures such as micelles are of increasing interest as a means for drug transport and release. Nanoscale micellar carriers are particularly advantageous for passive drug targeting into solid tumors, as the hyperpermeable angiogenic vasculature of tumor tissues exhibits enhanced permeability and retention of carriers <100 nm. In contrast to passive drug delivery, active targeting based on specific ligand-receptor interactions has recently received significant attention. Block copolymers bearing the carbohydrates as the targeting groups are expected to have utility in receptor-mediated targeting of genes and drugs to specific tissues/cells. In this study, we report the synthesis of a novel family of amphiphilic block glycopolymers containing D-glucose, D-galactose and D-mannose via metal-free organocatalyzed ring-opening polymerization of functional cyclic carbonates, which generates narrowly dispersed products of controlled molecular weight and end-group fidelity, and their application in drug delivery. Glucose-, galactose- and mannose-coated micelles are designed for targeting cancer (as many types of cancer cells over-express glucose transporters), liver and dendritic cells respectively. These glycopolymers self-assemble into micelles having a high density of sugar molecules in the shell, a size less than 100 nm with narrow size distribution even after drug loading, and little cytotoxicity, which are important for drug delivery. Using galactose-coated micelles as an example, we demonstrate their strong targeting ability towards ASGP-R positive HepG2 liver cancer cells in comparison with ASGP-R negative HEK293 cells although the galactose is attached to the carbonate monomer at 6-position. The enhanced uptake of DOX-loaded galactose-coated micelles by HepG2 cells significantly increases cytotoxicity of DOX as compared to HEK293. This new family of amphiphilic block glycopolymers has great potential as carriers for targeted drug delivery.
5:30 PM - PP2.10
Anti-apoptotic Bioactive Coating for Endovascular Aneurysm Repair.
Cindy Charbonneau 1 , Benoit Liberelle 2 , Marie-Josee Hebert 1 , Gregory Decrescenzo 2 , Sophie Lerouge 3
1 CRCHUM, Université de Montréal, Montreal, Quebec, Canada, 2 Chemical engineering, École Polytechnique, Montreal, Quebec, Canada, 3 Mechanical engineering, ÉTS, Montreal, Quebec, Canada
Show AbstractIntroduction–The pathophysiology of abdominal aortic aneurysms (AAA) leads to a sustained increase in vascular cell apoptosis. The use of a stent-graft in endovascular aneurysm repair (EVAR) accentuates the pro-apoptotic environment of AAA by limiting the access of oxygen and growth factors. The use of EVAR is currently compromised by an inadequate healing of the tissues around the prostheses. We assume that a bioactive coating including anti-apoptotic mediators could improve the healing process. Previous work showed that chondroitin sulfate (CS) triggers key mechanisms implicated in vascular repair. Other studies showed that epidermal growth factor (EGF) could be anti-apoptotic to vascular cells. We are therefore working on the development of an anti-apoptotic coating, including CS and EGF, to improve vascular repair after EVAR. The objectives of the present study were to optimize the grafting of CS and EGF and evaluate the bioactivity of the coating using vascular smooth muscle cells (VSMC).Methodology–CS was covalently attached to amino-coated silicone wafers by means of a water soluble carbodiimide system (EDC/NHS). EGF was subsequently immobilized on the carboxylic groups of CS using the same reagents. Several CS concentrations and [EDC]/[CS] ratios were used for the optimization. The surface properties were characterized by ellipsometry, XPS, TOF-SIMS and contact angle measurements. The bioactivity of the surface was assessed by western blotting, through ERK½ phosphorylation of VSMC exposed to serum-free medium for 45 minutes, to induce cell apoptosis. To quantify cell resistance to apoptosis, VSMC were exposed to serum-free medium for 24 hours and the number of apoptotic, necrotic and normal cells was detected through fluorescence microscopy using Hoechst/propidium iodide staining.Results and Discussion–For the optimization conditions, the thickness of each coating was measured by ellipsometry. A plateau was obtained with [CS] of 1%w/v and EDC ratio of 1 with a thickness of approximately 0.68±0.04 nm. The optimized conditions were used to immobilize EGF. The water contact angles of the silicone wafer, CS and EGF layers were measured to be 60.3±1.6°, 37.8±2.2 ° and 45.2±1.5° respectively. The coupling of CS significantly increased the hydrophilicity of the surface, compared to the amino-coated wafers. Cell resistance to apoptosis on CS coating alone confirmed that the anti-apoptotic properties of CS are maintained after its immobilization on the surface with VSMC. The number of apoptotic VSMC on CS coating was significantly lower than our negative control. The western blot revealed significantly higher ERK½ phosphorylation on CS+EGF surfaces, compared to CS alone, with intensities reaching our positive control. These results show great potential for CS and EGF to create a bioactive coating on endovascular prosthesis to counter VSMC depletion and promote healing after EVAR. This project is supported by the FMCQ, NSERC, CIHR and FRSQ.
5:45 PM - PP2.11
Nanoporous Biodegradable Polymers for Delivery of Protein Therapeutics.
Daniel Bernards 1 , Mark Steedman 1 , Paula Wynn 2 , On-tat Lee 2 , Robert Bhisitkul 2 , Tejal Desai 1
1 Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, United States, 2 Ophthalmology, University of California, San Francisco, San Francisco, California, United States
Show AbstractThere is need for sustained drug release devices that are highly efficacious for protein-based therapeutics. Many contemporary delivery routes, such as injections, are hampered by patient compliance, discomfort, risk, and inconvenience, as well as limited bioavailability and frequent administration. Alternatively, a therapeutic device capable of delivering a constant rate of drug over time can circumvent these issues. One attractive platform for such a device is the use of nanoporous materials. In porous materials, constant-rate diffusion is possible when the size of a diffusing species is comparable to material pore size. A process often referred to as "single-file" diffusion, this situation can lead to zero-order constant-rate release. For macromolecule delivery this requires pores on the order of a few tens of nanometers. To this end, nanoporous biodegradable polymers have been fabricated for delivery of protein therapeutics. Utilizing a template-based approach, zinc oxide nanorods were used to produce nanoporous poly(caprolactone) (PCL) films. PCL is an excellent candidate material since it biodegrades yet maintains its structural integrity during the majority of the degradation time course: this allows structural degradation to follow the effective therapeutic lifetime of the device. To validate this approach, we characterize the release of Lucentis, an age-related macular degeneration therapeutic, from nanoporous PCL thin films over extended periods. Furthermore, micro- and nano-strucutured PCL films have been implanted or injected into rabbit eyes over 6 months to determine the long-term biocompatibility and structural integrity of these materials.
PP3: Poster Session: Biointerfaces and Bioinspiration
Session Chairs
Phillip Messersmith
Rajesh Naik
Tuesday PM, April 06, 2010
Exhibition Hall (Moscone West)
6:00 PM - PP3.10
Glucose/O2 Biofuel Cell With Enzyme-based Electrodes.
Takeo Miyake 1 2 , Makoto Oike 1 , Shuhei Yoshino 1 , Yohei Yatagawa 1 , Keigo Haneda 1 , Hirokazu Kaji 1 2 , Matsuhiko Nishizawa 1 2
1 , tohoku.univ, Sendai Japan, 2 , CREST, Tokyo Japan
Show Abstract Enzyme-based biofuel cells, which generate electric power from the oxidation of biological fuels such as glucose, fructose or alcohol, have attracted much attention because such cells operate under mild conditions. Recently, we have developed various biofuel cells using enzyme-modified electrodes [1-3]. However, because enzyme is immobilized on an electrode via various mediator molecules, multistep electron transfer between enzyme and electrode is needed. Therefore, electrical energy is loss during reaction process, indicating that current density of the cell decreases. To resolve this issue, we have developed simple enzymatic electrode and discussed the performance of the electrode [4]. We have used two-types of enzymes: (1) glucose dehydrogenase (GDH) and (2) bilirubin oxidase (BOD). In the anode process, glassy carbon (GC) electrode of 3.0 mm diameter is cleaned by cycling between the potential of +2.0 and -0.3 V in 0.5 M sulfuric acid. After wash in water, the ketjenblack (KB) is coated on GC. The electrode is immersed in a sulfuric acid/nitric acid/water (1:3:1) mixture to activate the surface of the KB. After wash in water, nicotinamide-adenine dinucleotide (NAD+) is immobilized on the KB surface by immersing the electrode in 9.6 mM 1-ethyl-3- (3-dimethylaminoproryl)carbodiimide hydrochloride (EDC) for 1 h. GDH is bound to the NAD+ by immersing the electrode in 0.4 mg ml-1 GDH in phosphate buffered saline (PBS) solution. In the cathode process, GC electrode surface is cleaned and modified with the KB as described above. BOD adsorbs physiologically on the KB surface by immersing the electrode in 10 mg ml-1 in PBS. Finally, the performance of both electrodes is measured by cyclic voltammetry. In the presentation, we will report the condition and experimental result in detail.[1] M. Togo et al, J. Power. Sources. 178 (2008) 53.[2] M. Togo et al, Electrochim Acta. 52 (2007) 4669.[3] F. Sato et al, Electrochem. Commun. 7 (2005) 643.[4] T. Miyake et al, Chem. Phys. Lett. 480 (2009) 123.
6:00 PM - PP3.11
Lipase Immobilized onto Novel Silica-based Hybrid Foams: Synthesis, Characterizations and Catalytic Properties.
Nicolas Brun 1 2 , Annick Babeau Garcia 1 , Victor Oestreicher 1 , Herve Deleuze 2 , Clement Sanchez 3 , Rénal Backov 1
1 , Centre de Recherche Paul Pascal - CNRS, Université de Bordeaux, Pessac France, 2 , Institut des Sciences Moléculaires - CNRS, Université de Bordeaux, Talence France, 3 , Laboratoire de Chimie de la Matière Condensée de Paris - CNRS, Université Pierre et Marie Curie, Paris France
Show AbstractImmobilization or entrapment of biocatalysts [1] onto or within porous materials by either physical adsorption [2], covalent attachment [3], inclusion or encapsulation by sol-gel route [4], represent an attractive and efficient approach to facilitate their use in continuous processes. Such systems are expected to enhance stability, activity and selectivity while allowing efficient separation, recycling and reuse of costly enzymes. Thus, design of new functional porous materials to immobilize active biomacromolecules is both of economic and ecologic interests.Recently, as emerged the novel concept of “integrative chemistry” [5], from the interface between bio-inspired approaches and hybrid organic-inorganic chemistry. Through the application of this concept, the assembling of a large variety of molecular precursors or nanobuilding blocks into engineered hierarchical structures should be strongly pre-dictated. Particularly, functional ordered macro-mesoporous materials are of interest for multiple applications in heterogeneous catalysis, separation techniques, purification of wastewaters, sensors, optics etc. With this aim, our research group has developed a way to obtain hybrid macrocellular silica-based monoliths, labeled “Organo-Si(HIPE)”, exhibiting a hierarchically structured porosity in view of reaching final polyfunctionalities [6]. With the same strategy, and using the concept of immobilized biocatalysts, we have just designed a new series of hybrid monoliths labelled Lipase@Organo-Si(HIPE) [7]. The covalent attachment of various lipases in such macroporous hybrid materials deals with a high stability over esterification of fatty acids, hydrolysis of triglycerides and biodiesel production by transesterification. Yields, turnover and cycling performances, both in batch process and continuous flow, will be discussed. The resulting materials have been thoroughly characterized via a large set of techniques such as SEM, TEM, SAXS, mercury intrusion porosimetry, nitrogen adsorption and solid-state NMR.References[1] A. M. Klibanov Science, 1983, 219, 722.[2] G. Zhou, Y. Chen, S. Yan Micro. Meso. Mater., 2009, 119, 223.[3] C. Mateo, G. Fernandez-Lorente, O. Abian, R. Fernandez-Lafuente, J. M. Guisan Biomacromolecules, 2000, 1, 739.[4] M. T. Reetz, A Zonta, J. Simpelkamp Biotechnology and Bioengineering, 1996, 49, 527.[5] a) R. Backov Soft Matter, 2006, 2, 452; b) E. Prouzet, S Ravaine, C. Sanchez, R. Backov New J. Chem., 2008, 32, 1284.[6] a) S. Ungureanu, H. Deleuze, C. Sanchez, M. I. Popa, R. Backov Chem. Mater., 2008, 20, 6494; b) N. Brun, B. Julian-Lopez, P. Hesemann, G. Laurent, H. Deleuze, C. Sanchez, M.-F. Achard, R. Backov Chem. Mater., 2008, 20, 7117.[7] N. Brun, A. Babeau-Garcia, C. Sanchez, R. Backov French Patent, 2009, FR0954634.
6:00 PM - PP3.12
Molecular Dynamics Simulation of Bombolitin II in the DPPC Bilayer.
Namsrai Javkhlantugs 1 , Kazuyoshi Ueda 1
1 Graduate School of Engineering, Yokohama National University, Yokohama Japan
Show AbstractBombolitins are the family with five structurally and functionally related heptadecapeptides originally isolated from the venom of the bumblebee. These peptides melt the membrane of the red blood cell and the liposome and so on. But the detailed mechanism is not known yet. In present research, the bombolitin II (BLT2) was chosen from bombolitin family and performed the molecular dynamics simulation how BLT2 inserted and oriented in the membrane. At first BLT2 structure was constructed and obtained the lowest energy conformation. Then, BLT2 was inserted in the DPPC bilayer and simulated the peptide/bilayer system.
6:00 PM - PP3.13
Biological Application of Organically Functionalized 2:1 Trioctahedral Phyllosilicates.
Hyun-Jae Shin 1
1 Chemical and Biochemical Engineering, Chosun University, Gwangju Korea (the Republic of)
Show AbstractSilicate minerals comprise the largest and most important class of rock-forming minerals. Phyllosilicates (clay) or sheet silicates form parallel sheets of Si2O5 (2:5) tetrahedral silicates. Layered inorganic-organic composite materials based on 2:1 trioctahedral phyllosilicates have been synthesized and characterized for a variety of applications, such as ion exchange, catalysis, and the construction of nanoscale assemblies. Recently, several reports on the synthesis and characterization of organically-modified derivatives of magnesium phyllosilicate have appeared because of their wide applicability in areas such as wrapping of biomolecules and drug delivery system. Clay-based lamella materials can be used in a range of delivery methods and enable drug loading and targeted delivery to be controlled for extended therapeutic effects. These hybrid materials are members of a family of 2:1 organo-modified trioctahedral phyllosilicates with structures similar to that of natural talc. Many reports have illustrated the potential of preparing a wide range of synthetic lamellar inorganic-organic hybrid materials, and as a consequence a wide range of metal salts and organotrialkoxysilane precursors have been used to synthesize numerous organophyllosilicate. Although research on the synthesis of organoclay hybrid materials has received considerable attention, there is little report on the biological application including interaction with bacteria, fungi and animal cells. In this work, recent works on the antibacterial, antifungal, and algicidal activities of organically functionalized 2:1 trioctahedral phyllosilicates as well as the cytotoxicity of the organic clays and their derivatives are discussed.
6:00 PM - PP3.14
Spatially Selective Deposition of Zwitterionic D-Cysteine and a P-Benzoquinonemonoimine Molecular System on Periodically Poled Lithium Niobate.
Zhengzheng Zhang 1 , Jie Xiao 1 , D. Wu 2 , Alexi Gruverman 1 , Lucie Routaboul 3 , Pierre Braunstein 3 , Bernard Doudin 3 , Peter Dowben 1
1 the Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska, United States, 2 Department of Physics and Astronomy, North Carolina State University, Raleigh, North Carolina, United States, 3 Institut de Physique,Applique de Physique et Chimie des Matériaux de Strasbourg, Université Louis Pasteur Strasbourg, Strasbourg France
Show AbstractWe have able to selectively deposit folate, D-cysteine and a zwitterion compound from the class of N-alkyldiaminoresorcinones (or 4,6-bis-dialkylaminobenzene-1,3-diones, C6H2(NHR)2(O)2), compounds, where R =C5H11. The latter p-benzoquinonemonoimine has the largest dipole as the zwitterion “core” a large charge separation, with a large electric dipole moment across the non-aromatic “benzene” like plane. All of these molecules have very strong local dipoles and appear to adopt spatial localization consistent with the ferroelectric domain structure of lithium niobate (LiNbO3). We have been able to demonstrate that folate, D-cysteine and one of this class of p-benzoquinonemonoimine zwitterion compounds will all selectively adsorb from solution on periodically poled lithium niobate substrates using infra-red spectra-microscopy. The IR spatial microscopy is aided by the strong molecular IR absorption modes in a region of the IR where LiNbO3 has little or no absorption, although the spatial resolution of IR microscopy is relatively porr compared to most scanning probe microscopies (the former having a resolution no better than several microns). The spatial localization of the folate, D-cysteine and the p-benzoquinonemonoimine zwitterionic compound on lithium niobate suggests that the ferroelectric poling of lithium niobate either alters the surface chemistry of lithium niobate or that there is some dipole-dipole interaction between the substrate and these adsorbates. The spatial zwitterion structure is consistent with the periodically poled lithium niobate structure. Crystals of periodically poled lithium niobate with a periodic domain structure (period of ~28 µm) were fabricated by depositing a photoresist mask on the +c sample face and by applying a voltage of 10 kV through a fixture with an electrolyte solution. The mask was removed after poling by means of chemical-mechanical polishing leaving behind a bare ferroelectric surface, prior to the exposure to the molecular solutions. The surface topography was mapped by atomic force microscopy (AFM) while the domain patterns were characterized by means of piezoresponse force microscopy (PFM).
6:00 PM - PP3.15
Engineered Interfacial Adsorption of Proteins on Meso-structured Inorganic Matrices for the Fabrication of Bio-catalytic Hybrids.
Jing He 1
1 State Key Laboratory of Chemical Resource Engineering, beijing university of chemical technology, Beijing China
Show AbstractThe interfacial assembly of bioactive molecules with inorganic particles has been figured to be a fascinating route to create novel bio-inorganic hybrids or mimetic materials combining the physical and chemical features of inorganic particles with bio-functionalities1. In any research pointed to practical applications, the main concern is no doubt whether the immobilization affects biological functioning. The covalent binding of proteins to solid surface, for example, usually causes the loss of bio-catalytic activity, although a good operational stability could be expected. In our approach, the enzyme was first adsorbed non-covalently in the nano-sized channels of mesoporous silica, the protein conformational and bio-activity being well retained. The leaching of proteins non-covalently adsorbed is then prevented via the shrinkage of channel openings following protein uptake. The solid-protein interfacial non-covalent interactions could be generated and tuned as hydrogen bonding, hydrophobic affinity, electrostatic interaction and additional π-π overlapping by designing the surface moieties. In our recent work, the lipase adsorption on bi-dimensional platelet surfaces by electrostatic recognition was investigated. The nanosheets of layered double hydroxides (LDHs) were applied as the bi-dimensional surfaces, which was prepared by exfoliating LDHs in aqueous medium. The protein orientation at interfaces was rationally controlled by altering the PPL loading. The bio-catalytic activity of bound protein was found to depend remarkably on its orientation. In comparison to the soluble counterpart, considerable enhancements of bio-activity and thermal resistance were observed for the bound protein. What is being in progress in our group is to fabricate a hierarchical interfacial architecture and perform the hierarchical protein immobilization. The hierarchical interfacial architecture enhances the interfacial charge transfer, which is extremely critical for bio-devices. By the hierarchical immobilization, the bio-activity of protein is well retained and good operational stability is achieved. Still, this immobilization approach provides immobilized proteins with the possibility to be applied in a continuous processing way. Reference[1] Katz, E., Willner, I. Angew. Chem. Int. Ed. 2004, 43, 6042-6108. Srivastava, S., Verma, A., Frankamp, B. L., Rotello, V. M. Adv. Mater. 2005, 17, 617-621.
6:00 PM - PP3.16
Atomic Layer Deposition on Biological (Nano)structures.
Mato Knez 1 , Seung-Mo Lee 1 , Hyunbin Kim 1 , Lianbing Zhang 1 , Eckhard Pippel 1 , Ulrich Goesele 1
1 , Max-Planck-Institute MSP, Halle Germany
Show AbstractBiology provides a large number of structures on the micro- and nanoscale. Frequently such structures are used as templates for the deposition of inorganic materials. Most of the common approaches rely on liquid phase chemistry, like electroless deposition (ELD), sol-gel strategies, etc. In our work, we concentrate on the application of gas phase deposition techniques to biological structures and the investigation of the functionalities of the resulting materials. In particular atomic layer deposition (ALD) appears to be a very interesting strategy to go beyond the possibilities which are offered from solution based chemistry. For example, the narrow, 4 nm wide channel of a tobacco mosaic virus (TMV) is accessible for deposition by both ELD of metals [1] as well as ALD. [2] In the latter case, however, the resulting structures are, in contrast to the ELD, nanotubes, as very thing coatings of the walls of the tubes can be obtained. In addition, the variety of materials can be extended to functional materials like TiO2 by ALD. Such coatings are even observed, if the channels are on the Angstrom-scale, like in the case of Apoferritin. [3]
Aside from the biotemplated nanofabrication, in this presentation we show various opportunities to produce novel bio-inorganic functional structures. On the one hand, the coating itself can provide certain functionalities, like photocatalytic effects, which could be shown after coating collagen-based microfiber membranes with TiO2 or ZnO. [4] On the other hand, the ALD can easily be tuned into an infiltration technique which, for example in the case of spider silk, leads to a modified internal protein structure resulting in a greatly enhanced mechanical toughness of the material. [5]
[1] M. Knez et al., Nano Lett. 2003, 3, 1079.
[2] M. Knez et al., Nano Lett. 2006, 6, 1172.
[3] H. Kim et al., Langmuir 2009, accepted.
[4] S.-M. Lee et al., Phys. Chem. Chem. Phys. 2009, 11, 3608.
[5] S.-M. Lee et al., Science 2009, 324, 488.
6:00 PM - PP3.17
Multifunctional Nanowire Systems for Drug Delivery and Controlled Cell Behavior.
Karla Brammer 1 , Chulmin Choi 1 , Sungho Jin 1
1 Materials Science and Engineering, UCSD, La Jolla, California, United States
Show AbstractNanostructured materials can play a key role in localization and controlled/sustained release of drugs within the body. We have prepared vertically aligned silicon nanowire (SiNW) arrays, with a 10-40 nm diameter, by chemical etching and utilized them as novel nanostructures for mediating drug delivery and stem cell differentiation. Here we report antibiotic drug release kinetics from Si nanowire (SiNW) array vehicles which are desirably anti-biofouling, as well as capable of storing a relatively large amount of drug which allows sustained, long-term drug release over a period of months[1]. Furthermore, the bio-degradable nature of these nanowires can eventually allow natural disintegration and removal of the drug delivery vehicles. Interestingly, minor chemical and microstructural modifications of Si nanowire tips endowed a surprising ability of the SiNWs to precisely control cell behavior such as guided stem cell differentiation to a specific lineage, solely based on physical science parameters. These structural features have spurred our interest in the use of this system as a host or “mothership” for biomedical applications. The effects of various materials parameters on biological behavior are also discussed.[1] Karla Brammer, Chulmin Choi, Seunghan Oh, Christine Cobb, Laura Connelly, Sungho Jin,“Anti-Biofouling, Sustained Antibiotic Release by Si Nanowire Templates”,Nano Lett. 9(9),3296–3301(2009).
6:00 PM - PP3.19
Modified Cellulose as Nano-additive for Sustainable Polymer Composites.
Mauro Zammarano 1 2 , Douglas Fox 1 2 , Eric Balsley 1 , Jeffrey Gilman 2 , Christoph Weder 3 , Kadhiravan Shanmuganathan 4 , Stuart Rowan 4
1 Department of Chemistry, American University, Washington DC, District of Columbia, United States, 2 Fire Research Division, Building & Fire Research Laboratory, National Institute of Standards & Technology, Gaithersburg, Maryland, United States, 3 Adolphe Merkle Institute, Polymer Chemistry and Materials University of Fribourg , Fribourg Switzerland, 4 Macromolecular Science and Engineering, Case Western Reserve University , Case Western Reserve University, Cleveland, Ohio, United States
Show AbstractThe development of renewable and biodegradable materials is a primary necessity for humanity in the 21st century. Cellulose is an abundant and underutilized natural resource with low toxicity and potential hazard. In combination with polymers such as polylactide (PLA) and natural rubber (NR), derived from renewable sources, cellulose allows the preparation of sustainable composites with improved mechanical properties, like stiffness and heat distortion temperature, and without affecting biodegradability.Cellulose can be used to prepare cellulose nanocrystals (CNCs) with a diameter of about 10 nm and a length between 100 nm up to several microns depending on the source material (e.g., cotton, tunicate cellulose, microcrystalline cellulose, softwood pulp and algae) and specific treatment. CNCs can be used for the preparation of colloidal suspensions or polymer nanocomposites if a proper surface modification of CNCs is achieved. Acid hydrolysis, preferably with sulfuric acid, is used for the preparation of CNCs stable aqueous colloids. The high hydrophility of this cellulose made it suitable for the preparation of composites with water soluble or colloidal polymers. More hydrophobic polymers, however, requires an organophilic modification of cellulose in order to get a homogeneous dispersion of cellulose in the polymeric matrix. Polyhedral Oligomeric SilSesquioxane (POSS) are extremely efficient reactive surface agents with low toxicity. In this study we exploited the preparation of two sustainable polymer nanocomposites systems:a.CNCs from tunicates, treated with sulfuric acid, in combination with NR colloid;b.Nanofibrillated cellulose modified with POSS, in PLA polymeric matrix.The effect of modification on the morphology and the thermal stability of cellulose is investigated by scanning electron microscopy, infrared spectroscopy, thermal gravimetric analysis and microcombustion calorimeter. The incorporation of POSS onto the cellulose fibers results in a 50 % reduction in the heat release capacity and 30 % – 40 % in the total heat release over the pure cellulose fibers.The structure and morphology of PLA and NR composites were investigated by means of X-ray diffraction, laser scattering and optical and/or confocal microscopy. The ability of cellulose to generate a percolated network in the two composite systems, capable to increase the elastic and viscous modulus, was assessed by dynamic mechanical thermal analysis.
6:00 PM - PP3.20
The Selective Deposition of Conducting Polymers Using the Assembly of Biomolecules-loaded Colloidal Particles.
Youngnam Cho 1 2 , Grace Kang 1 2
1 Basic Medical Science, Purdue University, West Lafayette, Indiana, United States, 2 Center for Paralysis Research, Purdue University, W. Lafayette, Indiana, United States
Show AbstractA novel self-assembly of particles has been enormously investigated in various areas as ideal templates for creating regular arrays. As fundamental building blocks for efficient bottom-up approachs, colloidal particles provide flexibility by simply controlling the behavior of the individual particle. Moreover, 2D or 3D structures constructed with heterogeneous functionality exhibit different coordination properties. In our preliminary studies we discovered that dense and homogeneous distribution of biomolecules was not achieved over the Ppy surfaces through the electrochemical deposition process. A way to solve this issue is to use the drugs-loaded colloidal particles as an ideal and flexible building block. Being able to control the density and spacing of biological species on the polypyrrole-coated electrode is essential for using theses surfaces in bioelectronics and tissue engineering platforms. On the other hand, MCM-41 type mesoporous silica nanoparticles (MSNs) provide extremely high surface areas (>1000 m2/g) and tunable pore diameter in the range of 2 ~ 10 nm. A large surface-to-volume ratio allows for effective entrapment of biological entities into the pores of MSNs while retaining its bioactivity. Despite these favorable features as a carrier, MSN-based delivery system often caused lower therapeutic efficacy due to the lack of a sustained release over more than a few days. However, this problem could be overcome by successive growth of polyelectrolytes, especially poly-l-lysine (PLL) and hyaluronic acid (HA) on the surface of MSNs and by realizing a pH-responsive “regulated on-off system” at the site of action. In this study, we will use 100 nm MSN with a large pore diameter (~ 10 nm), where biomolecules, such as NGF or dexamethasone (Dex), would be loaded inside mesopores by engineering the internal nanostructure of the sphere. Subsequently, we plan to deposit successive (PLL/Dex/HA)n layers through the interaction of oppositely charged molecules on functionalized silica surfaces, which is designated as a LbL-MSN.We plan to electrochemically deposit polypyrrole layers on the surface of ordered structure of LbL-MSNs and selectively dissolute silica matrix. The polypyrrole-deposited particle arrays will be characterized by SEM, TEM, FT-IR spectroscopy, four-point probe, XRD, and UV spectroscopy. Furthermore, biological tests will be conducted with several types of cells.
6:00 PM - PP3.23
Dynamic Surfaces for Studies of Cell Polarization and Cell Migration.
Muhammad Yousaf 1
1 chemistry, university of north carolina at chapel hill, chapel Hill, North Carolina, United States
Show AbstractActive migration in both healthy and malignant cells requires the integration of information derived from soluble signaling molecules with positional information gained from interactions with the extracellular matrix and with other cells. How a cell responds and moves involves complex signaling cascades that guide the directional functions of the cytoskeleton as well as the synthesis and release of proteases that facilitate movement through tissues. The biochemical events of the signaling cascades occur in a spatially and temporally coordinated manner then dynamically shape the cytoskeleton in specific subcellular regions. Therefore, cell migration and invasion involve a precise but constantly changing subcellular nano-architecture. A multidisciplinary effort that combines new surface chemistry and cell biological tools is required to understand the reorganization of cytoskeleton triggered by complex signaling during migration. Here we generate a class of model substrates that modulate the dynamic environment for a variety of cell adhesion and migration experiments. In particular, we use these dynamic substrates to probe in real-time how the interplay between the population of cells, the initial pattern geometry, ligand density, ligand affinity and integrin composition affects cell migration and growth. We further show the results for a novel hypothesis in which cells have a migration memory based on their initial position that dictates subsequent motility that supersedes the composition of the underlying surface chemistry. Whole genome microarray analysis indicates that several classes of genes ranging from signal transduction to cytoskeletal reorganization are differentially regulated depending on the nature of the surface conditions.
6:00 PM - PP3.24
Nanostructured Biofunctionalized Teflon for Enhanced Cell Adhesion.
Sebastian Kruss 1 2 , Tobias Wolfram 3 , Joachim Spatz 1 2
1 Biosystems and New Materials, MPI of Metals Research, Stuttgart Germany, 2 Institute of Biophysical Chemistry, Heidelberg University , Heidelberg Germany, 3 Biomedical Applications of Engineered Interfaces, MPI for Metals Research, Stuttgart Germany
Show AbstractFor many years polymeric materials have been used for different biomedical applications. One such material is Teflon (polytetrafluoroethylene) which is used for e.g. vascular grafts or artificial cardiac valves. Teflon has superior properties such as great chemical inertness or small friction. Vice versa this turned out to be simultaneously a big drawback of the material because it complicates biofunctionalization.We have developed a new method to decorate Teflon AF (amorphous Teflon) surfaces with gold nanoparticles. In brief, gold nanoparticle arrays were produced on glass by block copolymer nanolithography and transfernanolithography was used to deposit arrays on Teflon. Transfer and accessibility was characterized by SEM, TEM and AFM. This new nanoengineering method can circumvent different problems of standard Teflon biofunctionalization. By using nanoparticles, the beneficial Teflon surface properties are only slightly changed. On the other hand, gold nanoparticles can now serve as a platform for biofunctionalization since any thiol-group carrying compound can easily be coupled covalently to the nanoparticle. Hence nanoparticles serve as anchor points for biomolecules and by changing the particle density the surface concentration of biomolecules can be tuned within two orders of magnitude (10-1000 nanoparticles/µm2). As a biological system we investigated HUVEC (human umbilical vein endothelial cell) adhesion on nanostructured Teflon as HUVEC adhesion is a standard model system for vascular graft research. In vascular graft engineering the final goal is to promote stable adhesion of endothelial cells on the polymeric material. A stable monolayer of endothelial cells could solve current dangerous and challenging problems like thrombosis and restenosis of small vascular grafts. Teflon surfaces with gold nanoparticles (58nm interparticle spacing), functionalized with the RGD-motive, enhanced endothelial cell adhesion significantly compared to non-nanostructured Teflon surfaces. In conclusion we have shown increased endothelial cell adhesion on nanostructured Teflon after immobilization of RGD. Nanostructured teflon surfaces may be used as a platform to biofunctionalize teflon with different biomolecules depending on it’s biomedical application. This could be a promising alternative to current methods of biofunctionalization since practically any biomolecule or linker molecule carrying a thiol group can easily be bound to gold nanoparticles.
6:00 PM - PP3.27
Effect of Surface Morphology on Adsorption of Triacylglycerol Nano-droplet.
Wen-Dung Hsu 1 , Hong-Wei Chen 1
1 Materials Science and Engineering, National Cheng Kung University, Tainan City Taiwan
Show AbstractMolecules such as lipis or triacylglycerols provide a simple way in precisely modifying the surface properties of materials through direct surface adsorption. Controlling the adsorption behavior definitely thus become a very important technique in nano-scale surface modification. The behavior of adsorption mainly depends on the properties of triacylglycerols (TAGs) which are mostly determined by its functional group, and on the morphology of the surface. Experimentally, however, it is very hard to manipulate the surface morphology exactly in nano-scale, making the studies of surface adsorption of nano-droplet very difficult. In this study Molecular dynamics (MD) simulations were used to investigate the adsorption behavior of Triacylglycerol nano-droplets on diamond surface with two kinds of morphologies- perfect flat surfaces and island-like surfaces. The selected TAGs are Tributyrin (four carbon atoms in the functional group), Trioctanoin (eight carbon atoms in the functional group) and Tripalmitin (sixteen carbon atoms in the functional group). The effect of the length of functional group is investigated. The simulations indicate that longer functional group facilitates surface wetting. The results further predict that the surface morphology influence adsorption behavior profoundly.
6:00 PM - PP3.28
Investigating the Interface between Proteins and Metal Surfaces by Molecular Dynamics Simulations.
Magdalena Siwko 1 2 , Stefano Corni 1
1 , INFM-CNR National Research Center S3, Modena Italy, 2 Dept. of Physics, University of Modena and Reggio Emilia, Modena Italy
Show AbstractThe interface between metal electrodes and proteins is fundamental for several material oriented applications. On one side, the electronic communication that can be established at this interface is the key to control biological functions via external potential biases; on the other side, processes that produce electrons or holes on the protein require collecting such charge carriers by inorganic sink to be effectively exploitable (for, e.g., biofuel cells or biosensing). Moreover, electron transfer (ET) proteins have been also explored as active elements of electronic devices such as rectifiers and transistors [1]. Again, the interface between the protein and the metal contacts is pivotal for the working of the device.Based on recent computational developments [2], we have simulated by classical molecular dynamics simulations entire ET proteins immobilized over gold surfaces in explicit water. Thanks to these simulations, we could rationalize ET trends that have been measured for mutants of Cytochrome C on gold electrodes [3]. In particular, we show that structural rearrangements taking place for proteins at the interface can have profound effects on the protein ET ability, even when the folding of the protein is conserved.[1] G. Maruccio et al. Adv. Mater, 17, 816 (2005).[2] F. Iori, R. Di Felice, E. Molinari, and S. Corni, J. Comp. Chem., 30, 1465 (2009).[3] C.A. Bortolotti, M. Borsari, M. Sola, R. Chertkova, D. Dolgikh, A. Kotlyar and P. Facci, J. Phys. Chem. C 111, 12100 (2007).
6:00 PM - PP3.29
Plasma Surface Modification of Polystyrene for Inhibition of Staphylococcus Epidermis Adhesion.
Gabriel Soares 1 , Cristiano Krug 2 , Danielle Trentin 3 4 , Karine Zimmer 3 , Fernando Bonatto 2 , Suzimara Rovani 1 , Marcio Soares 1 , Fabiano Rodembush 5 , Tiana Tasca 4 , Alexandre Macedo 3 4 , Israel Baumvol 1 2
1 , Universidade de Caxias do Sul, Caxias do Sul, Rs, Brazil, 2 , Instituto de Fisica - UFRGS, Porto Alegre, RS, Brazil, 3 , Centro de Biotecnologia – UFRGS, Porto Alegre, RS, Brazil, 4 , Faculdade de Farmácia - UFRGS, Porto Alegre, RS, Brazil, 5 , Instituto de Quimica - UFRGS, Porto Alegre, RS, Brazil
Show AbstractThe initial response of a living tissue to a biomaterial is almost entirely determined by the interface properties between them. However, a biomaterial with desirable bulk properties may not present the same mandatory surface properties. In this way, many techniques have been used to modify materials surface, such as plasma surface modification (PSM) as well as the use of protective coatings. In many fields, the use of PSM has emerged in order to avoid adhesion issues related to the use of coatings. Plasma immersion ion implantation (PIII) is becoming a popular technique to modify the structure and composition of materials surfaces, especially in order to functionalize materials surface with specific functional groups. Medical polymers play an important role in the treatment of many diseases, but they can become a channel for bacteria adhesion and breeding, leading to different types of infection, and becoming a prevalent risk in intensive care units. Among then, polystyrene (PS) is one of the most widely used kinds of polymer, especially in medical packaging and intravenous catheters. In this way, the control of physicochemical interactions between bacteria and the medical polymer surface is mandatory to avoid infections, mortality and to increase the health care service quality. In the present work, we investigated the structural and physicochemical modifications of polystyrene surfaces submitted to PSM, as well as the antiadhesion performance, before and after treatment, against Staphylococcus epidermis, the most important bacteria related to nosocosmial medical devices infections. The plasma treatments were performed under a mixture of N2/H2 (3:1) under 1.2 mbar, using a radio-frequency power source with a constant power of 125 W, for 5, 15, 30, 60 and 120 minutes. Physicochemical characterization was accomplished with X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and ion beam analyses (IBA), while the bacteria antiadhesion performance was determined by the plate-couting technique. We observed a 20% reduction in the bacteria adhesion after plasma treatment for 30 min. This reduction is followed by nitrogen incorporation in the PS surface. However, after 60 and 120 min treatment, an 80 and 97% adhesion reduction is observed, as well as an enhanced N incorporation. Correlations between the surface physicochemical modifications after PSM and the antiadhesion performance will be presented.
6:00 PM - PP3.30
Light Transmittance Study on Nanometer-scale Surface Architecture for Cell Proliferation Imaging.
Daocharad Burana 1 , Chetarpa Yipyintum 1 , Anan Srikiatkhachorn 2 , Nipan Israsena 3 , Min Medhisuwakul 4 , Nirun Witit-anun 5 , Saknan Bongsebandhu-phubhakdi 2 , Boonrat Lohwongwatana 1 6
1 Nanoengineering program, International School of Engineering, Chulalongkorn University, Bangkok Thailand, 2 Department of Physiology, Faculty of Medicine, Chulalongkorn University, Bangkok Thailand, 3 Department of Pharmacology, Faculty of Medicine, Chulalongkorn University, Bangkok Thailand, 4 Plasma & Beam Physics Research Facility, Department of Physics, Faculty of Science, Chiangmai University, Chiangmai Thailand, 5 Vacuum Technology and Thin Films Research Laboratory, Department of Physics, Faculty of Science, Burapha University, Chonburi Thailand, 6 Department of Metallurgical Engineering, Chulalongkorn University, Bangkok Thailand
Show AbstractMetallic glasses have attracted great interests due to their amorphous structure, which results in remarkable properties over ordinary metals. They are multicomponent alloys, therefore the specific criteria for selection of alloy composition for bulk metallic glass is significant in order to obtain a high glass forming ability and desired properties which leads to a wide variety of applications. Because if their exceptional near-net-shape forming capability, metallic glasses have been used commercially in many electronic devices and sporting equipment. Another area of interest for many researchers is the biocompatibility property which suggests medical application possibility. As a result, this research concentrates on biocompatibility together with ease of formability and high corrosion resistance of Au-based metallic glasses. This family of metallic glasses consist mainly of gold, making it the outstanding candidate for specific medical tasks such as neurological applications. Different surface deposition techniques such as sputtering, cathode arc physical vapor deposition and flash evaporation are employed to synthesize Au-based metallic glass thin films. Research focuses on optimum thickness, process parameters and composition for cell imaging and biocompatibility. Quantitative analysis of light transmittance through synthesized thin films with various thicknesses, such as UV/Visible spectroscopy, is performed afterwards to study the light transmittance property, consequently, the optimum thickness is determined. Cell cultured method is then applied together with the light transmittance analysis to characterize for biocompatibility and allows the microscopic monitoring of cell proliferation under inverted optical microscopy, the standard for cell imaging, using variety of cell lines such as epithelial cell lines, nerve cells lines, and osteoblast. The goal of this analysis is to achieve biocompatible Au-based metallic glass with optimum properties and compositions for promoting cell growth and proliferation.
6:00 PM - PP3.32
Engineering the Hydroxyapatite-Protein Interface to Control Bone Cement Properties.
Eddie Wang 1 2 3 , Seung-Wuk Lee 1 3
1 Bioengineering, University of California, Berkeley, Berkeley, California, United States, 2 Bioengineering, University fo California, San Francisco, San Francisco, California, United States, 3 Physical Biosciences Division, Lawrence Berkeley Lab, Berkeley, California, United States
Show AbstractSelf-setting calcium phosphate cements (CPCs) provide a simple, rapid, and biocompatible means of filling bone defects. Unfortunately, brittleness limits their use to non-load-bearing sites. As a result, a number of off the shelf polymers have been explored as additives to improve CPC mechanical properties. However, few studies have addressed the importance of the interface between the polymer and crystalline phases. To explore this interface we are utlilizing bacterially synthesized elastin-like polypeptides (ELPs). Using genetic engineering and chemical modification we can precisely control molecular weight and charge distribution. In addition, we have incorporated various synthetic hydroxyapatite binding motifs derived from natural bone-associated proteins, phage display, and marine adhesive proteins. When incorporated into CPCs, the ELPs drastically alter the resulting mechanical properties in a binding sequence dependent manner.
6:00 PM - PP3.33
ToF-SIMS Study of Photo-oxidation of NH2 Self-assembled Monolayers on Gold Substrate.
Szu-Hsian Lee 1 2 , Wei-Chun Lin 1 , Che-Hung Kuo 1 2 , Bonnie Yu 1 , Wei-Lun Kao 1 2 , Guo-Ji Yen 1 2 , Chia-Yi Liu 1 , Yun-Wen You 1 , Hsun-Yun Chang 1 , Chi-Ping Liu 1 3 , Jing-Jong Shyue 1 2
1 , Academia Sinica, Taipei Taiwan, 2 , National Taiwan University, Taipei Taiwan, 3 , National Tsing Hua University, Hsinchu Taiwan
Show AbstractNH2-terminated self-assembled monolayer (SAMs) on gold substrates has been employed in many biological applications. Recently, it is found that amine group is not stable under ambient environment. The degradation of NH2-terminated SAMs on gold substrates was clearly observed by X-ray photoelectron spectrometry (XPS) and their zeta potential as a function of pH. However, the chemical structure of NH2-terminated SAMs after exposing to ambient environment needs to be determined. In this work, contact angle was used to detect surface energy in terms of polar and dispersion contribution of amine SAMs stored in different environments. A high-resolution time-of-flight secondary ion mass spectrometer (ToF-SIMS) was used to analyze the surface chemical structure of degraded amino-SAMs. It is found that the amine functional group is oxidized to and stops at nitro group. This result explained the observed change in XPS spectra and zeta potential. In addition, comparing with the amino-SAMs stored in ethanol and in darkness, the oxidation is suppressed hence photo-oxidation is proposed. In other words, by isolating oxygen or ambient light, the shelf-life of amino-SAMs modified substrate is prolonged
6:00 PM - PP3.34
Plasma Polymerization for Bio-assisted Fabrication of Nanostructures.
Rachel Jakubiak 1 , Kyle Anderson 3 , Joseph Slocik 1 2 , Michael McConney 3 , Jesse Enlow 1 2 , Timothy Bunning 1 , Rajesh Naik 1 , Vladimir Tsukruk 3
1 Materials & Manufacturing Directorate, US Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States, 3 School of Materials Science and Engineering and the School of Polymer, Textile, and Fiber Engineering , Georgia Institute of Technology, Atlanta, Georgia, United States, 2 , UES, Inc., Dayton, Ohio, United States
Show AbstractPlasma-enhanced chemical vapor deposition (PECVD) allows deposition of conformal, ultrathin, and uniform polymer coatings from gaseous, liquid or solid precursors onto a variety of materials. Our process uses a modified afterglow plasma reactor operated at room temperature where plasma polymerization occurs downstream from plasma generation. This allows controllable retention of the precursor’s functionality needed for surface-induced biomineralization on soft or delicate substrates that cannot withstand high temperature or multiple wet-chemistry treatments. Amine-functionalized substrates, derived from the plasma polymerization of L-tyrosine, enabled biomineralization of gold nanoparticles from a solution of gold chloride. Templated gold nanoparticle coatings were formed by the placement of a shadow mask on the substrate during plasma deposition creating a micropatterned plasma polymerized tyrosine film. Subsequent gold chloride exposure created a gold nanoparticle network replica of the initial micropattern. This method of templated biomineralization is adaptable to a variety of practical inorganic and organic substrates, such as silicon, glass, nitrocellulose, polytetrafluoroethylene, and woven silk fibers.
6:00 PM - PP3.35
Strategy for Micropatterning Protein Chain Conformation in Silk Fibroin Materials.
Maneesh Gupta 1 , Srikanth Singamaneni 1 , Michael McConney 2 , Lawrence Drummy 2 , Rajesh Naik 2 , Vladimir Tsukruk 1
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson AFB, Georgia, United States
Show AbstractSilk fibroin proteins isolated from the cocoon of the silkworm bombyx mori have been heavily researched for applications such as tissue engineering scaffolds, biosensors, bioelectronics, and structural materials. The mechanical and chemical properties of materials made from fibroin depend heavily on the secondary structure of the protein. Fibroin has been shown to readily transform from random coil to β-sheet conformation in response to external stimuli including heat, organic solvent, and mechanical stress. In this work, we present a novel strategy to selectively tune the chemical and mechanical properties of nanometer-scale silk fibroin materials by spatial micropatterning of the protein’s secondary structure with high resolution. The technique for patterning silk secondary structure presented here utilizes capillary transfer lithography (CTL) to deposit a mask on silk films. The mask is used to modulate the exposure of the silk film to methanol vapor resulting in selective conversion of the film to the β-sheet conformation. We show that the patterned silk material with alternating random coil and β-sheet regions retain their intrinsic chemical and mechanical characteristics and show well- developed modulation of localized properties. Using this strategy, we envision the ability to fabricate structured silk materials with properties tuned by the ratio of random coil to β-sheet structure, as well as micropatterned silk materials with highly localized regions tailored to suit particular functions. For example, in tissue engineering, patterned silk materials could be used to create scaffolds with uniform nominal surface chemistry and variable mechanical properties or biodegradation. This would allow researchers tremendous flexibility in the control of cell behavior. The ability to create tailored biocompatible materials with tunable properties in a straightforward and robust way without the use of toxic chemicals will provide additional versatility to the use of silk in biotechnology and micro-device applications.
6:00 PM - PP3.36
Design of Cell Culture Stable Peptide-nanoparticle Conjugates to Investigate Receptor-ligand Interactions.
Lisa Maus 1 2 , Oliver Dick 3 , Hilmar Bading 3 , Joachim Spatz 1 2 , Roberto Fiammengo 1 2
1 Department of New Materials and Biosystems, Max Planck Institute for Metals Research, Stuttgart Germany, 2 Department of Biophysical Chemistry, University of Heidelberg, Heidelberg Germany, 3 Department of Neurobiology, Interdisciplinary Center for Neurosciences, University of Heidelberg, Heidelberg Germany
Show AbstractWe are aiming at designing stable gold nanoparticles (AuNPs) functionalized with active peptides to study cell death pathways in primary hippocampal neurons.The AuNPs are synthesized via reduction of gold chloride and grown to the desired size using hydroxylamine hydrochloride as reducing agent in a seeded-growth reaction. Furthermore, the obtained particles are passivated with a mixed monolayer containing either PEG 3000 or Alkyl-PEG 600 based thiols to prevent aggregation in high ionic strength solutions such as cell culture media. The passivation layer is composed of a mixed monolayer of carboxylic acid- and amine-terminated thiols. The carboxylic acid groups essentially stabilize the particles due to electrostatic repulsion, whereas the amino groups allow for functionalization. We characterized the composition of the passivation layer via quantitative fluorescence analysis. Subsequently, cystein-terminated peptides are coupled to the passivated AuNPs utilizing a cross linker strategy. Conjugation of the peptides to the ligand shell of the AuNPs and not directly to the surface is an appealing strategy to preserve the biological activity of the peptides.In our case we coupled the peptide conantokin G to AuNPs, known to specifically block N-methyl-D-aspartate receptors (NMDA) which are crucial for calcium influx in postsynaptic neurons. Elevated intracellular calcium levels triggered by calcium entry through synaptic NMDA receptors promote cell survival. In contrast, calcium entry through extrasynaptic NMDA receptors seems to initiate cell death cascades. This concept of differential signalling by synaptic and extrasynaptic NMDA receptors is important for the understanding of neuronal diseases such as stroke in which brain damage may be caused by activation of extrasynaptic NMDA receptors. In order to prove this hypothesis, we designed a special antagonist for extrasynaptic NMDA receptors by coupling conantokin G to AuNPs. The sterically demanding peptide-coupled AuNPs should exclusively allow blockade of extrasynaptic NMDA receptors and thereby block cell death pathways leaving the synaptic NMDA Receptors unaffected. Neurons treated with these functionalized particles are expected to survive when exposed to high levels of glutamate.In this contribution we emphasize on the characterization of conantokin G functionalized AuNPs with a diameter of 30 nm that are too large to diffuse into the synaptic cleft. We determined the number of functionalizable amino groups in the ligand shell as well as the number of conjugated conantokin G molecules using a quantitative fluorescence-based assay.We have incubated the functionalized AuNPs with HEK 293 cells transiently transfected with NMDA receptor subunits NR1 and NR2B and we could clearly observe selective binding of the AuNPs to the cell membrane. Further studies on receptor-ligand interaction are currently underway.
6:00 PM - PP3.37
Measuring and Tuning Adhesive Properties of Mfp-1 Films by Shear and Tensile Strain.
Rebecca Schur 1 , Delphine Gourdon 1
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States
Show AbstractMussels adhere permanently to a variety of surfaces by depositing a highly specific ensemble of 3,4 dihydroxyphenyl-L-alanine (DOPA) containing proteins. Using an atomic force microscope (AFM) in buffer solution, we have investigated the adhesive properties of Mytilus edulis foot protein mfp-1 nano-films adsorbed onto stretchable silicone (PDMS) sheets. The mfp-1 films were subjected either to shear (with a bare AFM silica tip) or to tensile strain of the underlying substrate (using a home-made strain device), and the adhesion profiles were monitored as a function of time, shearing distance, shearing velocity, and percentage of strain of the PDMS sheet. Our results indicate that, although no adhesion was detected between the tip and the mfp-1 film in ‘relaxed’ conditions, both shearing the upper film layer and stretching the underlying substrate significantly alter (increase) the adhesion. Furthermore, using intermittent contact, AFM imaging of the mpf-1 film shows no damage of the surfaces even after several shearing cycles or strain application. The chemical (specific role of DOPA) and physical reasons for such ‘switchable’ adhesive properties as well as the potential use of mepf-1 stretchable films in biomedical applications (e.g. as surgical adhesives for wound healing) are discussed.
6:00 PM - PP3.4
The Effect of Surfactant Chemistry on the Self-assembly of Langmuir Monolayers and Subsequent Calcium Carbonate Crystallization.
Conrad Lendrum 1 2 3 , Bridget Ingham 1 3 , Michael Toney 4 , Kathryn McGrath 2 3
1 , Industrial Research Ltd, Lower Hutt New Zealand, 2 School of Chemical & Physical Sciences, Victoria University of Wellington, Wellington New Zealand, 3 , MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington New Zealand, 4 Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Menlo Park, California, United States
Show AbstractBiominerals have finely tuned physical characteristics that are matched to their final function. For example, in humans, sea urchins and brittlestars, calcium carbonate is used as gravity receptors, for structural integrity and as microlenses, respectively. Functionality this diverse, from a single composition, epitomises the hierarchical control achieved by Nature. The promise of biomineralization lies in the discovery of the mechanisms employed by nature to construct these complex structures, and in applying them to the fabrication of synthetic inorganic materials. However, to date our knowledge of the intermolecular interactions, both chemical and geometric, that occur at the organic/inorganic interface remains insufficient for the design and synthesis of new tailor-made materials. Using synchrotron-based GIXD and X-ray reflectivity we have recently shown in-situ real-time evidence of monolayer rearrangement during the inorganic nucleation event[1]. With a view to exploring this self assembly process further, we have investigated calcium carbonate nucleation and growth under substituted fatty acid Langmuir monolayers. Based on differences in head group electron density, and the proximity of the substituted functional group to the primary carboxylate group, a comparison of octadecylmalonic acid, 2-methyl, 2-bromo, 2- and 3-hydroxyloctadecanoic acids provides insights into the role surfactant head group chemistry plays in the soft templation/information transfer process across the organic/inorganic interface. Surface pressure, potential, BAM, GIXD and X-ray reflectivity analysis points to chemical substitution resulting in monolayer behaviour dominated by the bulky monopolar head groups. Similarly, the resulting calcium carbonate crystal orientation and morphology is dominated by the interaction with the specific head group chemistry, such that three different responses to monolayer substitution were observed. 2-hydroxy-octadecanoic acid and octadecylmalonic acid were found to exhibit strong calcium binding, which leads to an electrostatics-dominated interaction and {10.4}-oriented crystal growth. In contrast, 2-methyl- and 2-bromooctadecanoic acid exhibited preferential orientation to a level much greater than that observed in an octadecanoic acid Langmuir monolayer-based system. As for 3-hydroxyoctadecanoic acid, movement of the hydroxyl group by one position effectively negates the affect of substitution, displaying monolayer and crystal traits commensurate with octadecanoic acid. Consequently, face selective nucleation in Langmuir monolayer derived crystallisation is not favoured by strong cation binding and rigid templation, rather significant preferential orientation can be achieved in this highly dynamic system by allowing self assembly to dominate. [1] C. Lendrum, M. F. Toney, B. Ingham, B. Lin, M. Meron, and K. M. McGrath, Real time in-situ detection of crystallisation at a Langmuir monolayer, in preparation.
6:00 PM - PP3.5
Biomimetic Adhesive Nanostructures for Skin Diagnostics.
Jennifer Sample 1 , Julia Patrone 1 , Jennifer Breidenich 1 , Jason Benkoski 1 , Lisa Kelly 1 , Huong Le 1
1 , Johns Hopkins U Applied Physics Laboratory, Laurel, Maryland, United States
Show AbstractStreptococcus epidermidis is a bacterium that is generally non-pathogenic and ubiquitously found in skin. It exhibits remarkable adhesive properties both to skin and indwelling medical devices such as catheters, which can lead to biofilm formation. Its cellular surface has been studied and associated cellular adhesive components identified. This work seeks to exploit and mimic the remarkable adhesive properties of this organism, toward the ultimate goal of designing a novel drug delivery vehicle or biosensing platform. Large nanoparticles were selected to serve as a synthetic substitute for the bacteria, and coated with S. epidermidis adhesive biomolecules, including teichoic acid, to determine whether this molecule would lead to enhanced adhesion to cellular surfaces. Adhesion was characterized using a double cantilever beam adhesion technique, and cell/surface interactions were observed using confocal microscopy. This biomimetic hybrid synthetic/biological material could find applications as a long-lasting drug delivery vehicle, or in diagnostics as a rapid, non-invasive screening for inflammatory markers.
6:00 PM - PP3.6
Synthesis, Growth Procedure and Crystallographic Properties of Hierarchical-structured Vaterite.
Qiaona Hu 1 , Jiaming Zhang 1 , Fuxiang Zhang 1 , Henry Teng 2 , Rodney Ewing 1 , Udo Becker 1
1 geological sciences, U. of Michigan, Ann Arbor, Michigan, United States, 2 Department of Chemistry, the George Washington University, Washington DC, District of Columbia, United States
Show AbstractCalcium carbonate (CaCO3) occurs widely on the earth’s surface and represents the largest geochemical reservoir for carbon. Vaterite, a less stable polymorph of CaCO3, has been of great interest because its crystallization strongly associated with biogenic activities and itself an important precursor in several carbonate-forming processes. However, the mechanism of stabilization of vaterite, the procedure of the hierarchical structure formation, and the crystallographic data for vaterite crystals have been poorly documented. We have developed a method to produce vaterite by adding a common inorganic molecule, ammonia, instead of organic additives, into Ca-CO3 containing solutions. The SEM and TEM studies indicate that in the early stage of crystal formation, vaterite grains are aggregations of spherical nano-particles with random crystallographic orientations. Compared to the vulnerability of CaCO3 single crystals to electronic beams, the nano-strucutre vaterite in the early growth stage possesses a high resistance to the ionizing irradiation of the electron beam in the TEM. In the later growth stage, the nano-particles adjust their relative crystallographic orientations and grow into hexagonal sheets about one micron in diameter with (001) terminations. The cell parameters from XRD studies demonstrated that the vaterite crystallized in space group P63/mmc, with unit-cell parameters a = b = 4.1358(1) Å, c= 8.478(1) Å. The SEM and TEM images in high magnification further showed that the vaterite grains display a clear layered structure with a 6-fold symmetry, and each large layer, about 10-20 μm in diameter, was not a single crystal but composed of smaller hexagonal pieces of single crystal about 1 μm in diameter. The diffraction pattern of these small pieces illustrates that these pieces possess a hexagonal system, grow along (001) and terminate at {110} Miller plane.
6:00 PM - PP3.8
Single-crystal Composites: Gel-incorporated Single-crystals Grown From Hydrogel Media.
Hanying Li 1 , Huolin Xin 2 , David Muller 3 , Lara Estroff 1
1 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 Department of Physics, Cornell University, Ithaca, New York, United States, 3 School of Applied and Engineering Physics, Cornell University, Ithaca, New York, United States
Show AbstractIn Nature, organisms produce single-crystal composites of calcite crystals with incorporated biomacromolecular matrices. In order to understand this phenomenon, we have developed a model system of agarose-incorporated calcite single-crystals grown from agarose hydrogels (1, 2). Annular dark-field scanning transmission electron microscopy (ADF-STEM) and electron tomography reveal how random three-dimensional networks of agarose nano-fibers (diameter: 13 ± 5 nm) are incorporated into single-crystals of synthetic calcite by allowing both high- and low-energy fiber/crystal interface facets to satisfy network curvatures (3). The effects of gel concentration, gel strength, and the concentration of calcium ions on the amount of incorporated polymers have been investigated qualitatively by scanning electron microscopy (SEM) and quantitatively by thermogravimetry analysis (TGA) (4, 5). The results show that gel-grown calcite crystals have two states: with and without polymer incorporation. Crystals switch between these two states when gel strength and/or crystal growth rate change, suggesting that at the growth fronts there are two competitions: a force competition and a mass competition. The interplay between these two factors determines if the gel polymers are incorporated by the growing crystals.Two effects of gel-incorporation on the properties of the crystals have been studied. First, the presence of the agarose polymer inside of the crystals improves the toughness of the calcite crystals, as evidenced by non-angular features that were observed on fractured surfaces. Second, TEM observation shows that porous single-crystals have been obtained after removing the incorporated polymers from the agarose/calcite single-crystal composites by pyrolysis (5). The specific surface area (100 m2 g-1) measured by Brunauer, Emmett and Teller (BET) method is around 100 times higher than that of the non-porous calcite single-crystals with the same size.More recently, we prepared gel-grown glycine and calcium tartrate single-crystals and found that these two crystals also incorporated gel polymers under certain conditions (5). These results imply that gel-incorporation might be a general phenomenon for crystallization in gels.This work suggests an approach for modifying the internal structures of crystals and synthesizing single-crystal composites and porous single-crystals. Potential uses for the gel method include the preparation of materials that require both high crystallinity and high surface areas such as photovoltaic materials.References:1.H. Y. Li, L. A. Estroff, J. Am. Chem. Soc. 129, 5480 (2007).2.H. Y. Li, L. A. Estroff, Crystengcomm 9, 1153 (2007).3.H. Y. Li, H. L. Xin, D. A. Muller, L. A. Estroff, Science in press (2009).4.H. Y. Li, L. A. Estroff, Adv. Mater. 21, 470 (2009).5.H. Y. Li, L. A. Estroff, in preparation (2009).
6:00 PM - PP3: Bioint/insp
PP3.7 transferred to PP4.13
Show Abstract
Symposium Organizers
Rein V. Ulijn University of Strathclyde
Molly M. Stevens Imperial College London
Rajesh R. Naik Air Force Research Laboratory
Phillip B. Messersmith Northwestern University
PP4: Bioinspired
Session Chairs
Phillip Messersmith
Rajesh Naik
Wednesday AM, April 07, 2010
Room 3022 (Moscone West)
9:00 AM - **PP4.1
From 2D to 3D Peptide Assemblies Using Metal Nanoparticle Joints and Their Applications in Pathogen/Cancer Cell Chip Sensors.
Hiroshi Matsui 1
1 Dept. of Chemistry and Biochemistry, City University of New York-Hunter College, New York, New York, United States
Show Abstract Various 2D nano-structures and complex patterns have been fabricated by combining peptide self-assembly, biomineralization, and lithography. One strategy is to use antibody-functionalized peptide nanowires to assemble nanoscale building blocks at uniquely defined positions by molecular recognition. After configuring device geometries with these nanotubes, we turned on biomineralization function of peptides on the nanotube sidewall to develop metal/semiconductor coatings for electronics and sensor applications. Another strategy is to write mineralize peptides on substrates by lithography and metal/semiconductor patterns are generated in nanoscale via biomineralization on these peptides. Recently DNA bionanotechnology has been used to precisely assemble 3D shapes, but methodology to develop highly ordered macroscopic materials from these nanostructures remains limited and for practical use the production scale, the yield, and the size of the assembled materials need to be amplified. Peptides are another of nature’s building blocks with even more specificity, robustness, and versatility for assembly that can be exploited to design new 3D architectures. Here, nanoscale peptides and ligand-functionalized nanoparticle hubs were self-assembled into micron scale 3D cube-shaped crystals, creating a physical framework for the proposed biomimetic assembly strategy. In this approach we took advantage of the naturally robust assembly of collagen triple helix peptides and used them as nanowire building blocks for the 3D crystal generation. Using streptavidin-functionalized Au NPs and the type I wild type collagen specifically modified with a biotin moiety in vivo, we created micro-sized cubes with peptide nanowires as spokes and Au NPs as hubs. This simple, rapid fabrication protocol produces high yields of 3D materials in controlled shapes, dependent on the design of the NP junctions, with extremely high yields. The 2D peptide assemblies can be applied to biosensor chips for detecting pathogens and cancer cells. When the peptide nanotubes coated by the antibody of target pathogen were bridged between electrodes, the detection was made by the capacitance change via the binding events of viruses on the nanotube. The advantage of this chip sensor as compared to conventional nanoscale chip sensor is that the characteristic capacitance values for pathogens could be used to identify the stains of viruses in addition to the antibody recognition of the nanotube. The sensing with the peptide nanotube sensor chip was fairly robust and the detection limit was on the order of 100 virus or bacteria particles/mL. Cancer cells can also be detected sensitively by probing the difference in membrane mechanics; cancer cells are more elastic than normal cells. As these cells were swollen under hyposmotic pressure, elastic cancer cells swell and this change is detected by the impedimetric transducer. This sensing platform is reusable by simple washing process.
9:30 AM - PP4.2
Clathrin: A Modular Protein-based System for Directing Growth of Inorganic Nanostructures.
Alia Schoen 2 , Sarah Heilshorn 1 2
2 Geballe Laboratory for Advanced Materials, Department of Materials Science and Engineering, Stanford University, Stanford, California, United States, 1 Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California, United States
Show AbstractNature has evolved numerous methods for the self-assembly of nanoscale architectures with high levels of precision. Biomolecules such as DNA, bacterial membranes, viral particles, and proteins all exhibit stunning regularity and reproducibility in the structures they can achieve, making them ideal templates for the directed growth and assembly of inorganic nanostructures. While some success has been realized in patterning materials from these biological templates, they generally have been limited to simple 0-D or 1-D structures. In contrast, proteins have the ability to form 2-D and 3-D structures, and the immense library of naturally available proteins encourages the development of new techniques to reproducibly template complex functional nanoscale architectures using these materials. Using clathrin as a model protein, we are developing flexible biotemplating protocols to interface protein structures with a variety of inorganic materials.The intracellular transport protein clathrin is composed of three semi-flexible arms that form a pinwheel structure with three-fold symmetry. Clathrin provides a framework that offers access to a variety of architectures, both 2-D and 3-D. In a cell, clathrin, assisted by adaptor proteins, assembles into 2-D networks at the lipid membrane and pinches off to form 3-D spherical cages around lipid vesicles. We have achieved reconstitution of these architectures and others, such as barrels, tetrahedra, and cubes, in vitro without adaptor proteins by modulating environmental conditions (pH, concentration, buffer ionic strength) during assembly. Systematic study of these environmental conditions is leading to an understanding of the kinetic and thermodynamic principles of self-assembly and predictive, controllable structuring of clathrin.Within a cell, many adaptor proteins bind to clathrin via a consensus motif of amino acids. Borrowing this motif, we have designed bi-functional peptides that serve as molecular bridges between specific sites on the clathrin biotemplate and inorganic materials such as gold, titania, and cobalt oxide. Generating a family of these peptides enables flexibility to interface the protein template with a variety of inorganic materials without requiring any direct chemical or genetic modifications to the template. These engineered peptides demonstrate mineralization activity of the biotemplate at room temperature and pressure.The ability of this single protein to assemble into multiple 2-D and 3-D structures and to interface with multiple inorganic materials via designed peptides makes clathrin a flexible biotemplating platform. Using this system, the underlying structure of templated materials can be easily changed while using the same protein assembly unit for the template, resulting in the rapid development of multiple inorganic nanostructures and making this approach applicable to a broad range of applications.
9:45 AM - PP4.3
A Critical Assessment of Nucleic-mediated Materials Synthesis.
Stefan Franzen 1 , Donovan Leonard 2
1 Chemistry, North Carolina State University, Raleigh, North Carolina, United States, 2 Physics and Astronomy, Appalachian State University, Boone, North Carolina, United States
Show AbstractRNA- and DNA-mediation or templating of materials has been used to synthesize nanometer scale wires, and CdS nanoparticles. However, RNA and DNA have the potential to act as catalysts, which could be valuable tools in the search for new materials. RNA has the ability to catalyze splicing and cutting of other RNA molecules. Catalytic activity has been extended to more general classes of reactions for both RNA and DNA using in vitro selection methods. However, catalytic activity in materials synthesis is a more recent idea that has not yet found great application. The first example of RNA-mediated evolutionary materials synthesis is discussed with specific data examples that show the incompatibility of the reagents in the solvent system employed leads to spontaneous formation of nanostructures of the starting material Pd2(DBA)3 rather than formation of palladium nanoparticles, as originally thought. A case study of this example of materials synthesis is described using high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), electron energy loss spectroscopy (EELS) and optical microscopy (OM). It is shown that the spontaneous formation of aggregates of Pd2(DBA)3 with well-defined shape can be mistaken for mediated formation of nanoparticles. This example raises important questions regarding the extent to which non-aqueous solvents should be used in nucleic acid-mediated processes, the nature of selections in enzyme and materials development, and the requirement for chemical compatibility of the precursor molecules. The importance of good characterization tools at every stage of an experimental process is illustrated with concrete examples. In order to look at the way forward for nucleic acid-mediated materials synthesis, an examination of the chemical interaction of nucleic acids with various precursors is considered. Application of density functional theory calculations provides one means to predict reactivity and compatibility. The repertoire of chemical interactions in the nucleic acids is considered vis-à-vis common metals and metal chalcogenides. The case is made for the need for water-soluble syntheses and well-controlled kinetics in order to achieve the control that is theoretically possible using nucleic-acids as a synthetic tool.
10:00 AM - PP4.4
Exploring Bio-inspired Strategies for the Production of Noble Metal Nanocatalysts.
Marc Knecht 1 , Dennis Pacardo 1 , Ryan Coppage 1 , Rajesh Naik 2
1 Department of Chemistry, University of Kentucky, Lexington, Kentucky, United States, 2 Materials and Manufacturing Directorate, Air Force Research Lab, Wright-Patterson AFB, Ohio, United States
Show AbstractWith the threat of the exhaustion of fossil fuels and the deteriorating environment, new catalytic materials are required that are both energy and environmentally friendly. To that end, materials that are functional in water at room temperature at low concentrations are desirable; however, attaining all three characteristics from one species remains challenging. In contrast to traditional materials approaches, bio-inspired methods have been gaining strength as alternative techniques to produce functional materials that operate under biological conditions. Phage display has been used to isolate peptide sequences that can nucleate and grow nanomaterials of technologically interesting compositions. In this talk, our recent efforts to control the production of Pd nanocatalysts using peptides will be presented. Based upon the peptide’s surface structure, nanomaterials are achieved that are functional for C-coupling reactions in water at room temperature. The materials are active at Pd loadings ≥0.005 mol% for quantitative reaction yields.
10:15 AM - PP4.5
Harnessing Biological Machinery to Manufacture Functional Nanocomposite and Nanotube Assemblies.
Haiqing Liu 1 , Gabriel Montano 1 , Darryl Sasaki 2 , George Bachand 3 , Erik Spoerke 3 , Bruce Bunker 3
1 Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Albuquerque, New Mexico, United States, 2 , Sandia National Laboratories, Livermore, California, United States, 3 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractMolecular motors cooperate with filamentous microtubules in a dynamic fashion directing the transport and assembly of biological nanomaterials in cells. A dynamic process such as this addresses some major challenges constraining nanomaterial assembly today such as chemical equilibria and diffusional transport. Emulating nature’s process, we developed an ex vivo energy-consuming synthetic strategy combining chemical selectivity to assemble nanocomposite materials. The translational and rotational motion of the microtubules involved with motor proteins initiates the process. Assembly occurs in a highly parallel, nonlinear manner, leading to the formation of mechanically constrained three-dimensional ring structures. In this talk, I will present examples of organizing a range of technologically important nanomaterials such as semiconducting and metallic nanoparticles into functional device assemblies. Such a strategy can also drive liposomes to form secondary structures, such as lipid nanocircles and lipid nanotubular networks hundreds of microns in length. Inspired by and involved with biomolecular machinery, this synthetic system works as a nanomanufacturing factory enabling dynamic assembly of various types of nanostructured composites that are promising to become an integral part of the future hybrid materials and devices.
10:30 AM - PP4.6
Bioinspired Patterned Surfaces With Actuated Adhesion.
Marleen Kamperman 1 , Dadhichi Paretkar 1 , Eduard Arzt 1
1 , INM - Leibniz Institute for New Materials, Saarbruecken Germany
Show AbstractThe subject area of adhesion not only poses many interdisciplinary fundamental questions but is also of great interest in microfabrication, biomedicine, construction industry, sports equipment etc. Several materials strategies over the last years have been inspired by biological systems: the adhesion performance of flies, spiders and geckoes was investigated by nanomechanical techniques and traced back to a combination of van der Waals and capillary forces. A common feature is the miniaturisation of fibrillar contact elements, which in the case of the gecko reach nanoscopic dimensions [1-3].We developed microstructured model surfaces using patterning technologies to investigate the effect of material properties and geometry on macroscopic adhesive forces and energies. These geometry-property relationships were used to guide the design of novel bioinspired artificial adhesives. Here, we demonstrate that responsive polymer materials can be used to create microstructured surfaces with actuated adhesion. Application of an external field (e.g. thermal, magnetic, chemical or acoustic) causes changes in the topographical pattern and this influences the final adhesion performance. For example, shape memory polymers were used to show adhesion actuation using temperature [4]. Arrays of microfibers, with diameters between 0.5 and 50 μm and lengths between 10 and 100 μm, were patterned by soft moulding. Mechanical deformation at the shape-memory transition temperature, followed by cooling to room temperature in the deformed position yielded a temporary non-adhesive surface consisting of pillars in a tilted position. By reheating above the transition temperature, the patterned surface switched from the temporary non-adhesive state to a permanent adhesive surface with a large increase in adhesion. Such active structures may have interesting applications in responsive systems where adhesion or friction management is required. [1] E. Arzt, S. Gorb and R. Spolenak, “From micro to nano contacts in biological attachment devices”, PNAS 100 (19), 10603-10606 (2003)[2] S. Gorb, “Attachment Devices of Insect Cuticle”, Springer Netherland, 2001 [3] K. Autumn et al., “Adhesive force of a single gecko foot-hair”, Nature 405, 681-685 (2000)[4] S. Reddy, E. Arzt and A. del Campo, “Bioinspired surfaces with switchable adhesion made of shape memory polymers”, Adv. Mater. 19, 3833-3837 (2007)
10:45 AM - PP4: bioinsp
BREAK
11:00 AM - **PP4.7
Photonic Bio-inspiration: Biological Mechanisms for Manipulating Colour and Appearances.
Peter Vukusic 1
1 School of Physics, Exeter, Exeter United Kingdom
Show AbstractThe study of structural colour in brightly coloured animals is an exciting interdisciplinary area of research1. Complex photonic bandgap (PBG) structures in Colepotera2 and Lepidoptera3 suggest broad innovation in nature’s use of materials and its manipulation of light. In certain butterflies, ultra-long-range visibility of up to one half-mile is attributed to photonic structures that are formed by discrete multilayers of cuticle and air3. This contrasts, in other butterfly species, to photonic structures designed more for crypsis and which not only produce strong polarisation effects but can also create additive coloru mixing using highly adapted structures4. Optical systems also exist that employ remarkable 2D and 3D photonic crystals of cuticle to produce partial PBGs, with the effect that bright colour is reflected, or fluorescence emission is inhibited5, over specific angle ranges. From the perspective of modern optical technology, these structures arguably indicate a significant evolutionary step, since in principle, such 2D and 3D periodicities are potentially able to manipulate the flow of light more completely. This presentation will offer an overview of this emerging field of study, as well as several of the exciting recent discoveries that reflect nature’s optical design ingenuity, and some technological applications to which they are currently being applied.
11:30 AM - PP4.8
Metal-reducing Ultrathin Free-standing Membranes Based on Silk Fibroin.
Eugenia Kharlampieva 1 , David Kaplan 2 , Rajesh Naik 3 , Vladimir Tsukruk 1
1 Materials Science & Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Biomedical Engineering, Tufts University, Medford, Massachusetts, United States, 3 Air Force Research Laboratory, Materials and Manufacturing Directorate Wright-Patterson AFB, Dayton, Ohio, United States
Show AbstractAmong a variety of biomolecules, silk fibroin has been recognized as an attractive template for the synthesis of nano- and micro- inorganic structures due to a unique combination of biocompatibility, biodegradability, and excellent mechanical properties such as high tensile strength, high elasticity, and exceptional toughness. We report on an application of silk fibroin as an unltrathin redox-active template for one-step synthesis of gold nanoparticles via control over silk secondary structure. We found that both silk I (hydrated beta sheet and random coil structures) and silk II (beta-sheets) molecular layers can facilitate gold nanoparticle formation at ambient conditions, indicating that tyrosine groups are available for metal ion reduction in both conformations of silk. However, silk I generates gold nanoparticles with an average diameter of 17.5±5 nm which tend to form large coagulates up to 100 nm across, in contrast to individual nanoparticles of 6.7±1.4 nm grown on silk II films. We suggest that the presence of beta-sheets in silk II facilitate tyrosine ordering thereby resulting in well-dispersed and uniform nanoparticles. The mineralization does not result in transformation of the silk I secondary structure to silk II. In addition, the silk I structure in the presence of the gold particles is stabilized from further transformation into silk II even upon drying. These results are critical for developing a better understanding of silk interfacial behavior and offer an opportunity to design a new class of nanocomposites that combine the beneficial features of silk with those of the nanoparticles.
11:45 AM - PP4.9
Complementary Effects of Multi-protein Components on Biomineralization in vitro.
Elaine DiMasi 1 , Xiaolan Ba 2 , Yizhi Meng 2 , Sue Wirick 3 , Helga Furedi-Milhofer 4 , Miriam Rafailovich 2
1 National Synchrotron Light Source Dept., Brookhaven National Laboratory, Upton, New York, United States, 2 Department of Materials Science and Engineering, Stony Brook University, Stony Brook, New York, United States, 3 Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York, United States, 4 Chemistry Department, Hebrew University, Jerusalem Israel
Show AbstractThe extracellular matrix (ECM) is composed of mixed protein fibers whose precise composition affects biomineralization. We present a study on cooperative effects in fibronectin (FN) /elastin (EL) films, where pure proteins self-assemble into fiber networks similar to the ECM. The protein fibers undergo reorganization and changes to elastic modulus within hours of exposure to metastable calcifying solution, quantified by scanning probe techniques. Mineral particles are observed weeks later, first observed on the 10 nm length scale, and confirmed after 21 days' incubation to be the hydroxyapatite phase. Pure FN nucleates particles which are larger and appear earlier than a FN-EL mixture. Pure EL networks absorb Ca throughout the fiber length, as detected by synchrotron microspectroscopy and Ca L-edge XANES with 50 nm spatial resolution. Crystallite formation in EL is limited to particles contained within the protein fibers. Acting alone, EL therefore strongly suppresses mineralization but in concert with FN, its ability to collect Ca from solution enhances mineralization and results in higher coverage of particles than FN alone. Along with these results we will report on parallel studies of cultured osteoblasts under similar conditions and on micropatterned surfaces designed to affect ECM formation. Our aim is to elucidate how imposed micron-scale structures affect ECM formation, which in turn affects nanoscale structure and the mineralization behavior of cells.
12:00 PM - PP4.10
Bioinspired Nanocomposites of Resilin and Cellulose Whiskers and Novel Methods for Resilin Polymerization.
Shaul Lapidot 1 , Guokui Qin 2 , Sigal Meirovitch 1 , Amit Rivkin 1 , Itai Podoler 1 , Mara Dekel 1 , Xiao Hu 2 , Sigal Roth 3 , Hagit Amitai 3 , David Kaplan 2 , Oded Shoseyov 1
1 The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, the Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot Israel, 2 Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, United States, 3 , Collplant Ltd., Ness Ziona Israel
Show AbstractThe arthropod cuticle is a sophisticated multifunctional structure giving the animals mechanical support, shape, and complex locomotion. This function is achieved by the unique architecture of the cuticle composed of highly crystalline chitin scaffold embedded in polymeric proteins matrix, multilayered with a plywood-like structure. Among the arthropod kingdom insects have developed the most complex locomotion skills such as flying and high jumping due specialized organs composted of composites of chitin and a highly elastic protein, resilin. Plant cell walls also present durable composite structures made of cellulose, other polysaccharides, and structural proteins. Plant cell wall composite exhibit extraordinary strength exemplified by their ability to carry the huge mass of some forest trees. Inspired by the remarkable mechanical properties of insect cuticle and plant cell walls we hypothesized that novel composites of resilin and cellulose will display useful mechanical properties combining strength and elasticity. For that purpose we have genetically engineered E. coli bacteria to produce resilin with high affinity to chitin via its chitin binding domain[1]. In addition we produced a novel resilin protein with affinity to cellulose by genetically engineering a cellulose binding domain into the resilin.Methods have been developed that allow production of cellulose nano-whiskers (CW) displaying high mechanical strength. CW can be processed into gels, membranes and foams and were shown to be a useful reinforcing agent in the preparation of nano-composite materials.CW foams are usually stiff and brittle. We have recently produced composite resilin-CW foams which resulted in dramatic alteration in mechanical behavior including high elasticity, resilience and resistance to repeated cycles of mechanical stress. Current methods known to mimic resilin crosslinking in-vitro involve either the use of costly peroxidase crosslinking enzymes or by the use of toxic chemicals. Therefore we explored new low cost and low toxicity methods for resilin crosslinking based on a photo-Fenton reaction. This reaction leads to a highly elastic, rubber-like, hydrogels. One goal of this effort is to utilize resilin and cellulose composite systems for novel degradable scaffolds for medical and industrial applications.1. Qin G, Lapidot S, Numata K, Hu X, Meirovitch S, Dekel M, Podoler I, Shoseyov O, Kaplan DL. (2009) Biomacromolecules in press.
12:15 PM - PP4.11
Splicing Electron Transfer Pathways to Electrically Interface Microbes at the Nanoscale.
Caroline Ajo-Franklin 1 , Heather Jensen 1 2
1 Materials Science, Lawrence Berkeley Natl Lab, Berkeley, California, United States, 2 Chemistry, UC Berkeley, Berkeley, California, United States
Show AbstractOrganisms have honed precise synthesis and assembly of functional nanomaterials over billions of years. The explosion of knowledge in molecular and cellular biology should enable us to add the functionality of living systems to the materials science toolbox. However, the functional integration of hard nanomaterials and living soft materials remains a key problem for advanced applications which require increasingly sophisticated, well-defined and stable composites. Of particular interest, joining the living and nonliving worlds through cellular-electrical connections has the potential to combine the best of both worlds for applications in biosensing, energy production, and programming cellular behavior. Towards this goal, we are using both materials and genetic engineering to create a defined electronic interface between living microbial cells and inorganic materials. Microbes living in anoxic environments have already evolved sophisticated electron transport chains which allow them to transfer electrons to metal oxides located exterior to the cell. We have used these systems as inspiration to develop a general method to re-channel the flow of electrons across biological membranes in other organisms. Specifically we have reconstructed an extracellular electron transfer pathway in the model microbe Escherichia coli that enables E. coli to reduce aqueous and solid metals and metal oxides. I will discuss what this engineered pathway teaches us about the specificity of electron transfer and on-going efforts to wire these engineered cells to metal electrodes.
12:30 PM - PP4.12
Metal Oxide-biomolecule Hybrid Nanoarchitecture as Biomimetic Light Harvesting Complex for Photoelectrochemical Solar Hydrogen Generation.
Debajeet Bora 1 2 , Artur Braun 1 , Edwin Constable 2 , Thomas Graule 1
1 Lab for high performance ceramics, EMPA-DUBENDORF, Dubendorf, Zurich, Switzerland, 2 Department of Chemistry, Universitat Basel, Basel Switzerland
Show AbstractThe wonder of nature using visible light to synthesize countless organic compounds whose enthalpy of formation needs much higher energies than provided by sunlight partly has been unveiled when the structure of the so-called light harvesting complexes (LHCs) of some photosynthetic bacteria was solved by X-ray structural analysis in the nineties of the last century. Phycobiliproteins are a kind of LHC present in cyanobacteria and certain algae (rhodophytes, cryptomonads, glaucocystophytes) that capture light energy which is then passed on to chlorophylls during photosynthesis. The motivation of this study is to synthesize a metal oxide based hybrid nanoarchitectural system with phycocyanin pigment (Phycobilliproteins) to mimic the natural system found in cyanobacteria. Hereby phycocyanin will act as a photon harvestor and antennae molecule for efficient electron transfer process though the molecular linker attached to the metal oxide interface.For the same, Iron oxide nanoporous films (Hematite ) was synthesized by sol gel approach.. From XRD result it was found that the diffraction peaks arise mainly from the dense SnO2 coating on the glass substrate. There is only one strong peak due to heamatite, namely the (110) reflection (in hexagonal coordinates).FESEM further signifies the highly porous architecture of the films with a thickness of 630 nm. Also, from the dark and light I-V measurement in a three electrode cappuccino cell with 1 M NaOH, the photocurrent density was found out to be 400µA/cm2 which confirmed that the films deposited were photo active.For the fabrication of the hybrid nanoarchitecture; phycocyanin was adsorbed onto the surface of heamatite film by physisorption process. The morphology of the proposed system is completely different from that of pristine electrode as evidenced from FESEM image. The photocurrent density of the hybrid electrode was 600 µA/cm2.This might be attributed due to higher energy transfer from the phycocyanin to the electrode surface.
12:45 PM - PP4.13
Atomistic and Mesoscale Modeling of Mechanics of Hierarchical Metal-Matrix Composites.
Dipanjan Sen 1 2 , Markus Buehler 1
1 Laboratory for Atomistic and Molecular Mechanics, Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe nanostructural makeup and hierarchical assembly of natural composite materials such as bone or nacre are crucial for their superior mechanical properties over their constituent phases, providing high strength and toughness at high stiffness. However, the transfer of similar mechanical properties to functional metal-matrix composites remains challenging. Here we propose the design of a hierarchical biomimetic metal-matrix nanocomposite inspired by the structural motif found in biological materials. The deformation response to tensile loading of a biomimetic metal-matrix nanocomposite is firstly studied using molecular dynamics. Maximization of flow strength of the nanocomposite is observed through breakdown of dislocation-mediated plasticity at platelet dimensions of nanoscale. The response to tensile loading, of the nanocomposite with two levels of structural hierarchy, is next probed through atomistically-informed mesoscale particle-spring simulations. In particular, general design strategies to maximize material toughness through assembly at two or more levels of hierarchy are explored. We observe that geometric confinement at each structural level, maximizes strength and toughness of the material. We also present theoretical analyses based on a hierarchical transition state theory to predict the performance of hierarchical materials. Through a simple deformation-rate-temperature model, we show that structures with hierarchical assembly of deformation mechanisms show higher toughness than structures with mechanisms at the same length scale and hierarchy. The discussion concludes with an illustration of how hierarchical designs can be used to optimize the material behavior at different levels in a material’s organization, leading to superior performance.
PP5: Bio/Nano
Session Chairs
Wednesday PM, April 07, 2010
Room 3022 (Moscone West)
2:30 PM - **PP5.1
Harnessing the Optical Properties of Nanoparticles Using Biomolecular Interactions.
Duncan Graham 1 , Karen Faulds 1 , Fiona McKenzie 1 , David Thompson 1 , Ross Stevenson 1
1 WestCHEM, Pure and Applied Chemistry, University of Strathclyde, Glasgow United Kingdom
Show AbstractMetallic nanoparticles can be used as basic materials for a wide variety of purposes including building blocks for nanoassemblies, substrates for enhanced spectroscopies such as fluorescence and Raman and as labels for biomolecules. Here we report how silver and gold nanoparticles can be functionalised with specific biomolecular probes to interact in a specific manner with a target molecule to provide a change in the properties of the nanoparticles which can be measured to indicate the molecular recognition event. Examples of this approach that will be discussed include DNA hybridisation to switch on surface enhanced resonance Raman scattering (SERRS) when a specific target sequence is present, the use of nanoparticles for in vivo SERRS imaging and the first steps towards using nanoparticle assemblies and SERRS as a nanoruler. These examples indicate how nanoparticles can be used to provide highly sensitive and informative data from a variety of biological systems when used with SERRS.
3:00 PM - PP5.2
Biologically Functional Cationic Phospholipid-Gold Nanoplasmonic Switches for Gene Silencing.
Somin Lee 1 , Darryl Sasaki 2 , Luke Lee 1
1 Bioengineering, University of California, Berkeley, Berkeley, California, United States, 2 , Sandia National Laboratories, Livermore, California, United States
Show AbstractGold nanoparticles (GNPs) in the near infrared (NIR) spectral region, due to their size and core material, display unique optical properties that make them attractive candidates for gene silencing. Due to their large surface area, GNPs are ideal carriers of small interfering RNA (siRNA). When GNP carriers are specifically used to convert light into heat, otherwise known as photothermal conversion, these GNP carriers are referred to as nanoplasmonic carriers. In particular, the NIR wavelength regime is well suited for biomedical applications since tissues and cells are essentially transparent. It is possible to obtain very efficient photothermal conversion of energy when the NIR light is matched to the plasmon resonance wavelength of the GNP. Additionally, heat transfer from the surface of GNPs to the surrounding cellular environment is highly localized, and therefore is thought to have minimal adverse effects on cells. Among the GNPs, rod-shaped GNPs, known as nanorods, are of particular interest due to their large absorption cross-section, a narrow spectral width of the longitudinal plasmon resonance band, and tunability of the longitudinal plasmon resonance wavelength based on aspect ratio.Despite these unique optical properties, the combination of three key factors – carrier functionality, colloidal stability, and cytotoxicity - have hindered the widespread use of gold nanorods as carriers in biomedical applications. The cytotoxic effects of CTAB-coated nanorods can be minimized by reducing the CTAB concentration below the critical micellar concentration, but at the expense of the nanorod suspension stability, consequently compromising their unique optical properties in biological environments. Finally, in order for plasmon-resonant nanorods to function as biological carriers, siRNA must be able to adsorb on their surface. In the case of siRNA, chemical modifications may affect the functionality and efficacy of siRNA. Therefore, the attachment of siRNA without additional chemical modifications to the siRNA themselves is highly desirable. Since cationic lipid formulations have already been optimized for both in vitro and in vivo gene transfer over the past decade, validated cationic lipids make ideal candidates for modifying ordinary nanorods into biologically compatible nanorods. The positively charged surface can be used to adsorb negatively-charged siRNA.We present biologically functional cationic phospholipid-gold nanoplasmonic switches (bioGNPs) that exhibit carrier capabilities, demonstrate improved colloidal stability, and show no cytotoxicity under physiological conditions. We first demonstrate that bioGNPs are stable under physiological conditions. We then show that the positively charged surface can adsorb siRNA. We demonstrate the biocompatibility of bioGNPs via viability/cytotoxicity and cell proliferation studies. We finally demonstrate the photothermal release of siRNA from bioGNPs to silence gene expression in living cells.
3:15 PM - PP5.3
Controlled Cell Delivery of Gold Nanoparticles by Particle Size and Surface Properties.
Eunkeu Oh 1 , Kimihiro Susumu 1 , James Delehanty 2 , Hedi Mattoussi 3 , Igor Medintz 2
1 Division of Optical Sciences, U.S. Naval Research Laboratory, Washington DC, District of Columbia, United States, 2 Center for biomolecular science and engineering, U.S. Naval Research Laboratory, Washington DC, District of Columbia, United States, 3 Department of Chemistry and Biochemistry, Florida State University, Tellahassee, Florida, United States
Show AbstractCell delivery of Gold nanoparticles (AuNPs) becomes of great interest today in applications such as imaging, photo-thermal therapy and drug or gene delivery. These applications require a “control” over nanoparticle-cell interactions, which are mainly dictated by chemical and physical properties of AuNPs. Here we reported the controlled cell delivery of AuNPs by size and surface functional properties. The AuNPs were prepared by one step synthesis method in aqueous phase which was recently developed in our groups using bidentated poly(ethyleneglycol) ligand. The size effect of AuNPs on cell delivery was studied in the range of about 1 ~ 100 nm. The terminal surface groups of AuNPs was also varied from inert methoxy to carboxyl terminal group which was modified by cell penetrated peptides (CPP). The results showed that the effect of size destining for AuNPs to locate from nucleus to cell membrane and the surface functional groups to switch AuNPs-cell membrane interaction.
3:30 PM - PP5.4
Investigations of Enzymatic Mechanisms for the Biodegradation of Carbon Nanotubes.
Brett Allen 1 , Gregg Kotchey 1 , Yanan Chen 1 , Naveena Yanamala 2 3 , Judith Klein-Seetharaman 3 , Valerian Kagan 2 , Alexander Star 1
1 Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Department of Environmental and Occupational Health, University of Pittsburugh, Pittsburgh, Pennsylvania, United States, 3 Department of Structural Biology, University of Pittsburugh, Pittsburgh, Pennsylvania, United States
Show AbstractBecause of their unique properties, that is to say, high tensile strength, chemical stability, and electrical conductivity, carbon nanotubes are an ideal material for use in composite strengthening. As nanotube applications progress in number and variety, so do the altering environments in which they are implemented. Yet, no consensus regarding the environmental and human toxicity factors of these materials exists.We have investigated the enzymatic degradation of single-walled carbon nanotubes (SWNTs). Use of peroxidase enzymes such as horseradish peroxidase (a common plant enzyme) and human myeloperoxidase (secreted by physiological neutrophils) have shown oxidative capabilities to degrade carboxylated SWNTs. Low localized concentrations of H2O2 (~40 µM), in combination with either peroxidase, initiate the degradation of SWNTs in approximately 10 days at room temperature. Moreover, it has been demonstrated that completely degraded products (consisting primarily of CO2) elicit no toxicological response. Mechanistic investigations have attributed enzymatic degradation to surface oxygen functionalities of SWNTs interacting with positively charged amino acid residues of both enzymes, leading to close proximal contact with the active oxidizing heme sites contained therein. Our results indicate that SWNTs might have limited persistence in the environment and that there are may be physiological mechanisms exist for their biodegradation.
3:45 PM - PP5.5
Gold Nanoparticles, Peptides and Cells: The Dynamic Picture.
Raphael Levy 1
1 Liverpool Institute for Nanoscale Science, Engineering and Technology, The University of Liverpool, Liverpool United Kingdom
Show AbstractThe dynamic interactions and fate of nanomaterials in contact with living systems is thought to be controlled by the structure and chemical properties of its interface. In most cases, the interface is formed by a layer of organic molecules (polymers, proteins or small molecules). This layer is itself dynamic and can evolve due to ligand exchange, enzyme activity and non-specific binding. The layer encodes the specific recognition properties of the particle and also often carries active moieties. It is therefore critical for the progress of the field that the chemical integrity of the layer and the fate of the core materials can be followed independently in real time.Using a combination of photothermal (imaging of the core material) and fluorescence (imaging of the organic layer) we have shown that peptides and proteins attached to nanoparticles are degraded by the enzyme Cathepsin L upon cell entry (See et al, ACS Nano, 3, 2461). This process is generic: Cathepsin L is ubiquitous and is able to cut a third of the proteome. Such potential degradation has to be taken into account in the design of future bioconjugated nanomaterials. The degradation mentioned above occurs in the endosomal/lysosomal compartments of the cell. Finding intracellular delivery strategies which reach the cytosol and bypass these compartments is of primary importance for applications of nanomaterials in imaging and nanomedicine. I will present a range of approaches currently under investigation in our lab, including the use of targeting peptides, polymeric capsules, light actuation and permeabilizing toxins.Another major challenge in the field is the structural characterization of nanomaterials. This challenge is similar to the one faced by biologists in the early days of structural biology. I will report on recent progress on the structural characterization of peptide-capped nanoparticles.
4:00 PM - PP5: Bionano
BREAK
4:30 PM - **PP5.6
Virus Capsids as Scaffolds for Functional Materials and Reactors.
Jeroen Cornelissen 1
1 Laboratory for Biomolecular Nanotechnology, University of Twente, Enschede Netherlands
Show AbstractThe interface between biology, chemistry and materials science provides inspiration for novel approaches to the design of catalytic systems and (functional) materials. Following the historical order from molecules (Wöhler, 1820), to macromolecules (Staudinger, 1920) and further to supermolecules (Lehn, 1987) the current trend is to design molecular structures that have dimensions in the nanometer range (nanochemistry). While traditional synthetic and supramolecular chemistry are currently entering the nanometer domain from the bottom and nanofabrication (lithographic techniques, stamping) from the top, biology has already employed many architectures of this size to perform complex tasks and functions. Self-assembled protein cages are beautiful examples of such structures and are well within the nanometer range (i.e. 10 to 100 nm). Large icosahedral viruses such as the Cowpea Chlorotic Mottle Virus (CCMV, D = 28 nm) and the Cowpea Mosaic Virus (CPMV, D = 30 nm) have been studied as synthetic scaffolds and the CCMV, for example, was employed as a confined space for the pH-dependent formation of oxometallates. The specific pH dependent gating properties of the CCMV (at pH > 6.5 pores of D = 2 nm are formed in the protein mantle) allow the encapsulation of different molecules in the virus capsid. In the present contribution I will describe the assembly over different length scales of the CCMV capsid proteins in the presence of macromolecular guest compounds. Subtle changes in the composition or structure of this cargo results in pronounced differences in the resulting hierarchically organized protein architectures. On the other hand the protein capsule is used as a reactor for the formation of polymer and inorganic materials with different composition.
5:00 PM - PP5.7
Modeling the Interactions Between Amphiphilic Nanotubes and Lipid Bilayers.
Anna Balazs 1 , Meenakshi Dutt 1 , Olga Kuksenok 1 , Steven Little 1
1 Chemical Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show AbstractUsing Dissipative Particle Dynamics (DPD) simulations, we investigate the interactions between amphiphilic nanotubes and a lipid bilayer. Each nanotube encompasses a hydrophobic stalk and two hydrophilic ends, which are decorated with hydrophilic ligands. The lipids in the bilayer are composed of a hydrophilic head group and two hydrophobic tails. The DPD method is a coarse-grained molecular dynamics (MD) approach that can capture effectively the hydrodynamics of complex fluids while retaining essential information about the structural properties of the system’s components. Via this simulation approach, we begin with a stable lipid bilayer membrane immersed in a hydrophilic solvent, and introduce the nanotubes into the surrounding solution. The energetically unfavorable interaction between the solvent and the hydrophobic segment of the tube drives these nanotubes to penetrate the membrane, with the hydrophobic stalk being buried within the hydrophobic domains of the bilayer. Through these simulations, we isolate conditions that promote the insertion of the tubes into the membrane. Ultimately, these embedded nanotubes could be used to regulate the passage of molecules through synthetic membranes.
5:15 PM - PP5.8
Pi-conjugated Self-assembling Peptides: Bioelectronic Supramolecular Polymers Inspired by the B-Amyloid Paradigm.
Stephen Diegelmann 1 , Brian Wall 1 , Geeta Vadehra 1 , John Tovar 1 2
1 Chemistry, Johns Hopkins University, Baltimore, Maryland, United States, 2 Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractFields as disparate as photovoltaics and tissue engineering have witnessed exciting advances based upon biomimetic design. While humanity has become quite proficient in the construction of elegant and complex molecular structures, our ability to control supramolecular interactions within functional nanostructures remains in its infancy. This contribution will describe two approachs from our laboratory to exert supramolecular control over the orientation and ordering of synthetic organic electronic moieties in aqueous media, as a step to encourage communication between biotic environments and organic electronic materials. We developed pi-conjugated “amino acids” that allow us to incorporate electronic functionality directly into the backbones of oligopeptides, and we have recently employed pi-conjugated diacids to serve as crosslinks ultimately leading to on-resin dimerizations. The pi-systems may be varied to influence electronic properties, the peptide segments may be varied to control assembly or control the presentation of biological signals, and different environmental stimuli can trigger the self-assembly process. The self-assembly process leads to the formation of self-supporting hydrogels, and visualization of these materials via AFM reveals the presence of well-defined one-dimensional aggregates with features smaller than 10 nm. We will discuss the spectroscopic measurements employed to further characterize the self-assembly process, the design of new peptide/pi-conjugated self-assembling molecules, and the prospects for biomaterials applications that can exploit the optoelectronic properties of these nanostructures.
5:30 PM - PP5.9
Developing Raman-active Probes for Understanding Metal Nanoparticle – Biological Interactions In Vivo and In Vitro.
Sandra Bishnoi 1 , Yiming Huang 1 , Ting Li 1 , Vimal Swarup 1
1 BCPS Department, IIT, Chicago, Illinois, United States
Show AbstractOur group has developed surface enhanced Raman scattering (SERS)-based tools for tracking nanoparticle uptake within cell cultures and in vivo systems to broaden our understanding of nanoparticle toxicity. Our SERS tracking technique provides a fast and semi-quantitative method for following the localization of nanoparticles within a cell. Using Raman-active polyethylene glycol moieties, we have demonstrated that alveolar macrophage cells begin nanoparticle uptake within an hour of exposure and that the process begins to saturate within the second hour. In addition, with this technique we have demonstrated that nanoparticles are distributed to progeny cells upon cell division. Toxicity profiling with an MTT assay suggests that gold-silica nanoshell toxicity within macrophage cells is dependent on the nanoparticle surface coating and nanoparticle concentration. We have also recently developed a SERS-based method for tracking nanoparticle uptake within Daphnia magna, a freshwater crustacean commonly used in environmental toxicity studies. This method is extendable to gold, silver, and gold-silver alloyed nanoparticles. Finally, we will demonstrate the progress we have made in creating a nanoparticle-based probe for reactive oxygen species (ROS). Since ROS have been implicated in the mechanism for nanoparticle toxicity, these new probes may have significant applications in understanding nanoparticle toxicity. In addition, ROS are responsible for many disease-specific cell injuries and therefore these probes may find broader application within the general field of biomedical sensing.
5:45 PM - PP5.10
Oligonucleotide-modified Gold Nanoparticles in Biological Systems.
Pinal Patel 2 3 , David Giljohann 2 3 , Dwight Seferos 4 , Weston Daniel 1 2 , Chad Mirkin 1 2
2 International Institute for Nanotechnology, Northwestern University, Evanston, Illinois, United States, 3 Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois, United States, 4 Chemistry, Univeristy of Toronto, Toronto, Ontario, Canada, 1 Chemistry, Northwestern University, Evanston, Illinois, United States
Show AbstractOligonucleotide modified gold nanoparticles (DNA-Au NPs or siRNA-Au NPs) have demonstrated utility in biodetection and post transcriptional gene regulation. DNA-Au NPs have the remarkable ability to act as both a cellular transfection and genetic regulation entity. Specifically, they retain their oligonucleotide shell under cell culture conditions, bind their complements with high binding constants, are stable in physiological environments, resist nuclease degradation, enter a variety of cell types without the use of auxiliary reagents, and are easily modified through the use of other biological molecules (peptides) or designer oligonucleotides (LNA) to increase efficacy.These nanoconjugates overcome many of the challenges related to oligonucleotide transfection by taking advantage of cooperative properties conferred by immobilizing oligonucleotides into a dense monolayer on a gold nanoparticle surface. A hallmark of these densely functionalized nanoconjugates is their ability to enter a wide variety of cell types (over 40 to date) in high numbers, which has been qualitatively demonstrated using confocal microscopy and flow cytometry. This unusual property is surprising since DNA-Au NPs contain a densely packed monolayer of polyanionic DNA (19 pmol/cm2) on the surface of each 13 nm gold particle. Generally, oligonucleotides, such as DNA or siRNA, require positively charged transfection agents for cellular internalization.We have found that the uptake of these nanoconjugates is dependent on the density of the oligonucleotide on the surface of the particles, where higher densities lead to greater uptake. Densely functionalized nanoparticles also adsorb a large number of proteins on the nanoparticle surface. However, nanoparticle uptake is greatest when the least number of proteins are associated with the nanoconjugates. When serum proteins are strongly bound to DNA-Au NPs, their cellular uptake is reduced drastically. This work provides initial fundamental insight into the cellular internalization of oligonucleotide-modified nanoparticles, and further offers design considerations for those wishing to exploit the properties of these novel materials, as well as other agents, for genetic regulation, intracellular detection, and therapeutics.
PP6: Poster Session: Bionano and Biofunctionalised Nanoparticles
Session Chairs
Thursday AM, April 08, 2010
Salon Level (Marriott)
9:00 PM - PP6.1
Organocatalytic Ring-opening Polymerizations of Guanidinylated Carbonate Monomers for Nanomedicine.
James Hedrick 1 , Christina Cooley 2 , Brian Trantow 2 , Matthew Kiesewetter 2 , Fredrik Nederberg 1 , Robert Waymouth 2 , Paul Wender 2
1 , IBM Research, San Jose, California, United States, 2 , Stanford University, Stanford, California, United States
Show AbstractThe emerging field of nanomedicine offers tremendous promise for improving health, curing disease, or repairing damaged tissues by applying the tools of nanotechnology to create and control materials with molecular-level medical effects. We have a program on drug encapsulation, transport and delivery using designer polymers and copolymers. This program is based on a family of active and selective organic catalysts for the ring-opening polymerization of lactones and cyclic carbonates. The tolerance of these catalysts for a wide range of functional groups has enabled the ring-opening polymerization of functionalized monomers. A particularly useful synthon for functional biodegradable monomers, are a family of cyclic carbonate monomer derived from 2,2-bis(methylol)propionic acid (bis-MPA). For example, the ring-opening polymerization of cyclic carbonates bearing protected guanidinium groups provides a strategy to generate new families of well-defined guanidine-functionalized oligomers and polymers. These guanidinylated oligocarbonates constitute a new class of molecular transporters that readily traverse cell membranes. Fluorescent probes can be used as initiators to generate fluorescently labeled oligomers in one step. These new synthetic methods provide new strategies for generating highly functionalized biodegradable polycarbonates for cellular imaging and drug-delivery applications.
9:00 PM - PP6.10
Folate-functionalized Platinum Nanoparticles for Tumor Targeting.
Yiwei Teow 1 2 , Suresh Valiyaveettil 1 2
1 Chemistry, National University of Singapore, Singapore Singapore, 2 NUS Graduate School (NGS), National University of Singapore, Singapore Singapore
Show AbstractNanomedicine involves the use of materials such as liposomes, polymeric micelles, nanoparticles and dendrimers for improving solubility and bioavailability of drugs and also tumor-targeting in order to reduce side effects to the patient. We have been investigating the toxicity of silver, gold and platinum nanoparticles in human cell lines and also the impact of these nanomaterials on developing aquatic species (zebrafish). With this knowledge in hand, we have developed multi-functionalized platinum nanoparticles with high dispersivity in buffer and in water which has the potential to act as drug carriers due to high cellular uptake. Folate-conjugated nanoparticles (Pt-FA) were studied against platinum nanoparticles capped with poly(vinylpyrrolidone) (PVP) which is non-toxic, highly soluble in water and its resultant Pt-PVP nanoparticles reported to have antioxidant properties in the nematode C. elegans. The talk will focus on nanomedical applications of Pt-nanoparticles at low concentrations (25µg/ml).
9:00 PM - PP6.11
Heat-generated Drug Delivery Using Polycaprolactone and Iron Oxide Magnetic Particles.
Sirinrath Sirivisoot 1 , Benjamin Harrison 1
1 Wake Forest Institute of Regenerative Medicine, Wake Forest University, Winston Salem, North Carolina, United States
Show AbstractThe potential of magnetic particles possess extensively advantages in biomedical applications nowadays. Using magnetic particles can improve magnetic resonance imaging, allow the site-specific drug delivery, increase the drug availability in vivo, and generate heat by the application of energy excitation (such as for hyperthermia treatment). The heat released from iron oxide particles can degrade the temperature-sensitive polymer, which is coated around iron oxide particles, and release antibiotics embedded within polymer. After drug loaded particles is injected into body, drug can be released in a controlled manner from particles, which can improve pharmacokinetics. In this study, iron oxide particles were synthesized by co-precipitation of iron salts and spray dry method. Antibiotic (Ciprofloxacin) was embedded within polycarpotactone (PCL), which coated iron oxide particles, by oil-in-water emulsion. Core-shell structures of PCL and iron oxide particles were characterized by scanning/transmission electron microscopy and Attenuated Total Reflectance-Fourier transform infrared spectroscopy. Ciprofloxacin encapsulated within PCL were released by heat after laser excitation to iron oxide particles. The drug encapsulation and release profiles were analyzed by high performance liquid chromatography and fluorescent intensity, respectively. Bone marrow-derived macrophages were cultured to understand foreign body responses in vitro, which important when delivering PCL-iron oxide particles at septic muscular tissues. Fibroblast proliferation of drug encapsulated within PCL-iron oxide particles were studied for cytotoxicity, which is important when PCL-iron oxide particles injected intravenously into body. The preliminary data showed that ciprofloxacin was successfully encapsulated within PCL-iron oxide particles and effectively inhibiting the growth of Staphylococcus aureus (Gram-positive bacteria) after 24 hours of cultures. Particle size and magnetization are important for heat-generated drug delivery strategy, which were correlated with cellular and bacterial studies, and elucidated.
9:00 PM - PP6.12
Assembly of Ag@Au Nanoparticles Using Complementery Stranded DNA Molecules and Their Detection Using UV-Vis and RAMAN Spectroscopic Techniques.
Derrick Mott 1 , Nguyen Thuy 1 , Yoshiya Aoki 1 , Shinya Maenosono 1
1 School of Materials Chemistry, Japan Advanced Institute of Science and Technology, Nomi, Ishikawa, Japan
Show AbstractSilver nanoparticles coated by a layer of gold (Ag@Au) have received much attention because of their potential application as ultra sensitive probes for the detection of biologically relevant molecules such as DNA, proteins, amino acids and many others. However, the ability to control the size, shape, and monodispersity of the Ag@Au structure has met with limited success. In our own research we have addressed this challenge by creating an aqueous wet chemical synthesis technique towards size and shape controllable Ag@Au nanoparticles. These materials are highly interesting because of the tunable silver core size, and the tunable gold shell thickness, opening many avenues to the modification of the particle properties in terms of biomolecular sensing. The resulting nanoparticle probes were independently functionalized with two complementary stranded DNA oligonucleotides. When combined, the complementary strands hybridized, causing the Ag@Au nanoparticles to assemble into large nano-structures. The presence of the oligonucleotide was confirmed through a series of techniques including UV-Vis and RAMAN spectroscopy, as well as HR-TEM, XPS, DLS, and many others. The results reflect the role that the nanoparticle physical properties play in the detection of the biomolecules, as well as elucidate the characteristics of the biomolecule-nanoparticle interaction.
9:00 PM - PP6.13
Standardizing the NSET Ruler: Factors Controlling the Applicability of the Ruler.
Mani Singh 1 , Geoffrey Strouse 1
1 Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States
Show AbstractMetal nanoparticles have been known for many decades for their characteristic properties. Recently their advent in the field of structural studies has been immense and still a lot needs to be explored. When placed near an organic dye they quench the fluorescence as a function of R-4 where R is the distance of separation between the metal nanoparticle and the organic dye. This distance dependence allows for longer distance measurements. A study probing into the factors that would determine the limits of the NSET ruler would help to not only standardize the technology but will also guide the users for its applicability. In this study, the effect of the spectroscopic nature of dyes is probed along with a study of the effect of nature of gold nanoparticles on the interaction with the dye.
9:00 PM - PP6.14
Optimum Bactericidal Conditions of Nano-material Application in Water Treatment.
Xubin Pan 1 , Jingbo Liu 2
1 Environmental Engineering, Texas A&M University - Kingsville, Kingsville, Texas, United States, 2 Chemistry, Texas A & M University – Kingsville, Kingsville, Texas, United States
Show AbstractBacteria can be found in drinking water and ground water and can result in serious illness and death. Escherichi coli, Legionella spp., Camplylobacter jejuni, Cryptosporidium, Giardia and Noroviruses are the most common water contaminants. New photocatalyst, nanoscaled titania (TiO2) has been proven to be an excellent and efficient photocatalyst for the degradation and complete elimination of numerous toxic contaminants in water and air under ultraviolet. While silver's (Ag) importance as a bactericide has been documented and its use in purification of both water and air has been known throughout the ages. Another feasible application is to fabricate nano-structured composite of titania (TiO2) and silver (Ag), which will be used as disinfectant agent to provide high efficiency at eliminating bacteria. There are numerous studies on the properties and applications of Ag-TiO2 system used as photocatalyst, optical application and antibacterial treatment. However, it’s current usage is not as common due to the cost of noble metals. According to our previous research, it is found that Ag nanomaterials can be prepared in a cost-efficient and environment-friendly manner. The amount of Ag can be precisely controlled and its addition will induce the band gap decrease of TiO2 via alteration of inhibiting the combination of electron and holes created. This will allow the improvement of the photo-reactivity and bactericidal performance of the composite. In order to optimize the bactericidal condition, it is prudent to implement systematic investigation on the light intensity, treatment temperature, concentration of the nanoparticles, and concentration of bacterium. In this research, performances of Ag, TiO2 and Ag-TiO2 nanomaterials on inactivating Escherichia coli (E Coli) were investigated systematically. Three-factor designs, including water treatment temperatures (17 °C, 27 °C, 37 °C and 47 °C), light intensity (dark, visible light and ultraviolet (UV) light), and different amount of catalyst (0 mg, 0.05 mg, 0.10 mg, 0.15 mg, 0.20 mg) were constructed to treat water samples containing four concentrations of E. coli (102 cfu/ml, 104 cfu/ml, 106 cfu/ml, and 108 cfu/ml). Results indicate that both Ag and Ag-TiO2 nano-materials display rapid performance at eliminating the bacteria with 100% efficiency under visible condition during short time at the ambient temperature. The intrinsic band energy was determined using ultraviolet visible spectroscopy (Perkin Elmer, Lambda 35 UV-VIS). The size effect was evaluated using transmission electron microscopy (FEI, Tecnai F20 G2) and light dynamic scattering (Brookhaven Instruments Corporation, ZetaPALS) as complimentary approaches.
9:00 PM - PP6.15
Peptoids Stabilize Nanoparticles Under Biological Assembly Conditions.
David Robinson 1 , Mary Langham 1 , George Buffleben 1 , Ronald Zuckermann 2
1 , Sandia National Laboratories, Livermore, California, United States, 2 Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractSequence-specific polymers are proving to be a powerful approach to assembly and manipulation of matter on the nanometer scale. This has been most impressive in the case of DNA, and progress has been made toward templating inorganic nanoparticles using DNA nanostructures. One obstacle to this progress is that inorganic nanomaterials are often incompatible with DNA assembly conditions, which are aqueous solutions usually high in both monovalent and divalent salt. Synthetic peptide ligands have been shown to improve stability under high monovalent salt.Ligands that are peptoids, or sequence-specific N-functional glycine oligomers, allow precise and flexible control over the arrangement of binding groups, steric spacers, charge, and other functionality. We have synthesized peptoids that can control growth of gold nanoparticles, prevent their aggregation in high-salt environments including divalent salt, and allow coadsorption of DNA or inclusion of other functionality. This degree of precision and versatility is likely to prove essential in bottom-up assembly of nanostructures and in biomedical applications of nanomaterials.
9:00 PM - PP6.16
Interfacing DNAs With Nanoparticle Arrays for High Density Single Molecule Fluorescence Imaging.
Randall Stoltenberg 1 , Jerrod Schwartz 3 , Stephen Quake 3 4 , Zhenan Bao 2
1 Department of Chemistry, Stanford University, Stanford, California, United States, 3 Department of Bioenginnering, Stanford University, Stanford, California, United States, 4 Howard Hughes Medical Institute, Stanford University, Stanford, California, United States, 2 Department of Chemical Engineering, Stanford University, Stanford, California, United States
Show AbstractThe ability to probe arrays of single molecules in parallel is an enabling tool for applications such biosensing and DNA sequencing. We are developing a platform to localize single DNA molecules on block-copolymer templated nanoparticle arryas for optical interrogation. One of the specific aims of this work is to increase the surface density of optically resolvable single molecules beyond the limit imposed by random deposition. In addition to exploring the theoretical gain in surface density possible using our approach, I will present a variety of surface chemistries we have employed to realize this goal. I will also discuss material and geometric constraints for interfacing single molecules with surface- bound nanoparticles.
9:00 PM - PP6.18
Examining Multi-component, DNA Templated Nanostructures as Magnetic Resonance Imaging Agents.
Hamsa Jaganathan 1 , Albena Ivanisevic 1 2
1 Biomedical Engineering, Purdue University, West Lafayette, Indiana, United States, 2 Chemistry, Purdue University, West Lafayette, Indiana, United States
Show AbstractMagnetic resonance imaging (MRI) is the leading non-invasive tool for diagnosis in medical imaging. Since MRI displays qualitative information, it must produce well-defined images with high contrast resolution, accounting for differences among all types of tissues. Failure to do so may result in images that cause physicians to misinterpret or misdiagnose diseases. An inexpensive approach to improve contrast is to use imaging agents that aid to distinguish different tissues within images. First generation agent and second generation agent designs exhibit inefficient in vivo mechanisms to enhance contrast. In order to improve the utility of imaging agents, the challenge in structural design needs to be addressed.Herein, one-dimensional (1D) NP chains templated on DNA strands are examined as potential imaging agents. The multi-component nanostructure, or the segmental design of two different materials, is designed to improve tumor –targeting and –imaging for MRI applications. Chain-shaped nanostructures are constructed by the linear arrangement of NPs along DNA strands. DNA is an abundant material found in nature that can be used for 1D formation due to its high aspect ratio, charged nature and base recognition properties. Linear segments of ferric oxide and gold NPs self-assembled on DNA are connected by enzymes to form a chain-shaped, multi-component nanostructure. The segments of ferric oxide NPs aid to influence the local magnetic field and shorten proton relaxation in selective tissues, while segments of gold NPs serve as a drug carrier. A biocompatible encapsulation is achieved by the layer-by-layer (LBL) method, or the layering of anionic and cationic polyelectrolytes repeatedly, to stabilize the NP chains in vivo. Peptides attached on the outer surface of the nanostructure aid for in vivo tumor targeting.The material properties, such as proton relaxation times, as well as, in vitro properties, such as cellular toxicity, were evaluated. Nuclear magnetic resonance was used to measure the longitudinal and transverse proton relaxation times. The 1D alignment of NPs exhibited higher relaxation times than dispersed NPs alone. In addition, the LBL encapsulation demonstrated to enhance the relaxation times, suggesting that high MRI contrast can be achieved when using 1D NP chains templated on DNA. Experiments using a fluorescent viability assay demonstrated that LBL-coated DNA nanostructures were not toxic to colon cells for three days. Transmission electron microscopy was used to visualize the cellular response from the nanostructures and inductively coupled plasma mass spectrometry was used to quantatively measure cell internalization of the nanostructures. Preliminary results suggest that DNA templated nanostructures can serve as effective imaging agents for MRI applications.
9:00 PM - PP6.19
Thrombin-absorbing Perfluorocarbon Nanoparticles for Improved Treatment of Acute Thrombosis.
Jacob Myerson 1 , Li He 2 , Douglas Tollefsen 2 , Samuel Wickline 2 1
1 Biomedical Engineering, Washington University, Saint Louis, Missouri, United States, 2 Department of Medicine, Washington University, Saint Louis, Missouri, United States
Show AbstractLocalized thrombus formation as a consequence of cardiovascular disorders can lead to acute arterial or venous occlusions. Optimization of anticoagulants for mediation of acute thrombi remains a significant research challenge. Here, an antithrombotic soft nanoparticle was designed as a first-in-class anticoagulant with intrinsic magnetic resonance contrast properties for imaging, concentrated therapeutic impact conferred by a thrombin-absorbing particle surface, and well-defined pharmacokinetics controlled by the particle itself.Methods: Perfluorocarbon (PFC) nanoparticles (NPs) were functionalized via covalent attachment of the irreversible thrombin inhibitor, PPACK (Phe(D)-Pro-Arg-Chloromethylketone). Particle-PPACK coupling was verified through zeta potential measurement and HPLC quantification. Inhibition of thrombin cleavage of Tosyl-Gly-Pro-Arg-4 nitranilide acetate was assessed via optical assay to verify that PPACK activity against thrombin and selectivity for thrombin over plasmin was not diminished on attachment to the particles. PPACK NPs (n=7), PPACK (n=4), heparin (n=4), non-functionalized NPs (n=7), and saline (n=7) were used to treat C57BL6 mice immediately following laser injury of the carotid artery. Time to thrombotic occlusion of the injured artery was assessed via Doppler flow measurement. For selected mice receiving NPs, particle retention in extracted carotid arteries was assessed via 19F magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) at 11.7 T. Results: PPACK activity against and specificity for thrombin was verified before and after coupling to PFC NPs. In our mouse injury model, PPACK and non-functionalized NPs failed to significantly delay time to occlusion of the carotid artery. Heparin delayed occlusion to a degree predicted by previously published data. PPACK NPs significantly outperformed both heparin (p=.001) and PPACK (p=.0005) in delaying occlusion of the carotid artery. Quantitative 19F MRS indicated the presence of more PFC NPs in occluded arteries of animals treated with PPACK NPs than in injured arteries of mice treated with non-functionalized NPs. Uninjured arteries from the same animals produced no 19F signal.Conclusion: In our model, PPACK-functionalized PFC NPs surpassed heparin in treatment of acute thrombosis. The particles take advantage of PPACK’s high affinity and specificity for thrombin while utilizing the vascular confinement and long circulating half-life of the PFC NPs. 19F MRS and MRI indicate that PPACK NPs are retained in forming clots. As a potent antithrombotic that can be traced with 19F MRS and MRI, PPACK NPs have great therapeutic potential. Summary: Perfluorocarbon nanoparticles functionalized with the direct thrombin inhibitor PPACK outperformed heparin in stopping acute thrombosis in mice. The particles had high affinity and specificity for thrombin and were visible with 19F magnetic resonance spectroscopy and imaging.
9:00 PM - PP6.2
Synthesis of FePt Nanoparticles With Controllable Size and Conformation for Applications as MRI/CT Dual Contrast Agent.
Yu-Sang Yang 1 , Yu-Hong Hsiao 2 , Shang-Wei Chou 3 , Sheng-Po Shia 1 , Dar-Bin Shieh 2 , Chia-Ching Chen 3
1 Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu Taiwan, 2 Institute of Oral Medicine, National Cheng Kung University, Tainan Taiwan, 3 Department of Chemistry, National Taiwan Normal University, Taipei Taiwan
Show AbstractThe FePt alloy nanoparticle has been developed for density magnetic recordings. The stability, high election density and controllable small size as well as the supermagnetic property make them a potential candidate for MRI/CT dual imaging contrast agent. We characterized the physical and chemical properties of the nanoparticles using TEM, FTIR, XRD and SQUID. Three different sizes of the nanoparticles were synthesized and compared: 3~4nm, 5~6nm and 12~14nm. Surface of the nanoparticles were modified with polyethylene glycol to achieve biological stealth. The in vitro biocompatibility evaluation revealed no significant cytotoxicity and hemolysis for all three sizes of nanoparticles. The MRI and CT contrast enhancement characterized using a phantom containing concentration gradient of the nanoparticles. A concentration dependent contrast enhancement in both imaging modalities were observed. The biodistribution of all three different size nanoparticles were analyzed in mice using atomic absorption spectroscopy. Spleen is the organ that trap most of the injected nanoparticles in all three groups. A significant increase of the in bio-distribution of the nanoparticles in lung was observed in the 6nm group followed by 12nm then 3nm. Larger nanoparticle size confer to prolonged blood circulation time. The distribution of the 12nm nanoparticle reached plateau at 12hrs in most organs, while it was 48hrs for the 3nm and 6nm group. Conjugation of monoclonal antibody against Her-2 revealed improved tumor targeting and decrease non-specific uptake. In vivo study showed that the anti-Her2 monoclonal antibody conjugated FePt nanoparticle was able to present significant specific imaging contrast of the target cancer cells in both imaging modalities. For image contrast enhancement, 12 nm particles outperform the 3nm and 6nm particles in the same particle concentration. In conclusion, the as synthesized FePt nanoparticles present a promising potential for the development of multi-modal molecular imaging contrast agent for both MRI and CT.
9:00 PM - PP6.20
Synthesis of Multi-functional Gels Comprising of Nickel-nanoparticles Carbon Nanotubes Heterostructures for Chemical and Biological Separation.
Wenwu Shi 1 2 , Kristy Crews 2 3 , Nitin Chopra 1 2
1 Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, Alabama, United States, 2 Center for Materials for Information Technology (MINT), The University of Alabama, Tuscaloosa, Alabama, United States, 3 Department of Chemistry, The University of West Alabama, Livingston, Alabama, United States
Show AbstractMetal nanoparticles (NPs) with controlled size, composition and morphology possess unique properties and have potential applications in biological, magnetic, and optical devices. The foremost challenge in order to utilize such NPs is to achieve their controlled assembly with negligible aggregation. A possible and rewarding method is by loading NPs onto high surface area substrates. Towards this end, high surface area and multi-functional carbon nanotubes (CNTs) are considered as unique substrates. Herein, we report an in-situ synthesis of nickel NPs uniformly decorating CNTs by a simple one-step process. Nickel NPs (11.9±2.0 nm) from thermal decomposition of a nickel-complex are precipitated onto surfactant-wetted CNTs (45.8±16.4 nm) at high temperature. The results show that there is a threshold diameter (~30nm) for CNTs below which the nucleation of the NPs on the CNT surface is minimal. A series of characterization steps including Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HR-TEM), X-ray diffraction (XRD) are conducted to understand the morphology, phase, compositions, nucleation and growth of NPs on the CNT surface as well as the NP-CNT interfaces. Furthermore, a unique separation media is developed by encapsulating NP-CNT heterostructures in a hydrogel, and then selectively binding and trapping of biomolecules is demonstrated. Such a novel, multi-functional, and multi-component hydrogel membrane can efficiently separate as well as purify chemical and biological species from a solution.
9:00 PM - PP6.21
Controlling Force Dependent Conformational Transitions in Acidic Polysaccharides at the Single Molecule Level.
Sanjeevi Sivasankar 1 2 , Sabyasachi Rakshit 1 2
1 Physics and Astronomy, Iowa State University, Ames, Iowa, United States, 2 , Ames Laboratory, Ames, Iowa, United States
Show AbstractAcidic polysaccharides are a key component of the extracellular matrix where they play an essential mechanical role in controlling cell migration and cell adhesion. These molecules normally experience mechanical tension and it is likely that force-driven conformational changes in acidic polysaccharides are physiologically significant. Here we use single molecule force measurements with the Atomic Force Microscope (AFM) to identify the relative contribution of electrostatic and hydrogen bonding forces to the conformational properties of acidic polysaccharides. Using single molecule AFM stretching measurements we show that upon loading, the backbone of these polysaccharides change their conformation. The conformational change depends upon the linkages between the sugar rings. Since the persistence length of the polysaccharide polymer does not depend on ionic strength, we engineered a metal-ion chelating switch that can toggle the persistence length of these molecules.
9:00 PM - PP6.22
Array Platform for Ion Channel Reconstitution.
Michael Goryll 1 , Nipun Chaplot 1
1 Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona, United States
Show AbstractThe ability to genetically modify ion channel protein has led to an increased interest in ion channel electrophysiology. While the materials and methods for single-channel electrophysiology are well-established, characterizing the behavior of multiple ion channels in parallel is still a challenge. The ability to for example study the influence of channel blockers on a series of different ion channel proteins in parallel would lead to a tremendous reduction in assay time and variation between subsequent experiments. We demonstrate a microfabricated silicon platform for ion channel reconstitution into suspended lipid bilayer membranes. Apertures with diameters in the range between 20 µm and 50 µm were photolithographically patterned on silicon and etched using a deep reactive ion ICP etching process. The silicon was oxidized to electrically isolate the substrate and the surface was functionalized with a plasma-deposited fluorocarbon layer to create a hydrophobic layer and smoothen out the surface roughness that is inherent to the dry etching process. By placing apertures in an array, the formation of multiple bilayers is possible. Combining the bilayer suspension structures with microfluidic wells, an electrical isolation of the different measurement sites can be accomplished as well as a separation of the ionic solutions, enabling reconstitution of different ion channel proteins. To overcome the problem of the limited shelf life of PDMS in microfluidic applications, wells were made out of acrylic and bonded to the functionalized silicon chips via carbon-based adhesive. Since the back side of the silicon is already covered with SU-8 epoxy resin to reduce the chip capacitance, bonding of epoxy structures is possible to create fluidic reservoirs.Key to a parallel measurement is the availability of a multi-channel amplifier that allows the reliable recording of currents in the range of a few pA with a low noise floor. We developed a 4-channel amplifier that is capable of measuring ion channel activity in a 2x2 silicon micropore array. Results on the parallel measurement of ion channels in suspended bilayer membranes will be demonstrated.
9:00 PM - PP6.24
Carbon Nanotubes in Conjunction With Cationic Phospholipids Effectively Deliver siRNA into Human Embryonic Stem Cells to Induce Differentiation.
Eric Brunner 1 , Richard Sear 1 , Peter Donovan 2 , Alan Dalton 1
1 Department of Physics, University of Surrey, Guildford United Kingdom, 2 Biological Chemistry, University of California, Irvine, Irvine, California, United States
Show AbstractA cell’s genetic functions and corresponding protein expressions can be altered by transportation of polynucleotides across the plasma and nucleus membranes making such transfection methods applicable for clinical therapies and biological research. Commonly employed transfection methods include electroporation, viral transduction, and nanoparticle delivery; each of which can possess drawbacks in terms of toxicity, transfection efficiency, or other undesirable side effects. Among the commonly investigated nanoparticles for transfection, carbon nanotubes (CNTs) have demonstrated several advantages including high loading capabilities on account of their large surface areas and multipurpose functionalization schemes for targeted delivery and imaging. Human embryonic stem cells (hESCs) have been highly investigated for their potential applications in cloning, tissue regeneration, and fundamental understanding of embryonic development. Investigations into the interplay of genes and signaling proteins of hESCs seek to understand differentiation and self-renewal behaviors. We show here the use of single walled CNTs in conjunction with positively charged phospholipids and short interfering RNA (siRNA) to silence expression of a master pluripotent gene, Oct-4, leading to induced differentiation of hESCs. Varying the phospholipid features such as the positively charged head group and the lengths and saturation of the tail groups alters the degree of the internalization of the CNT-phospholipid complex which in turn affects the efficacy of the siRNA as shown by Raman spectroscopy and quantitative polymerase chain reaction (qPCR) analysis. Charge stabilization of the siRNA can be optimized by changing the amount and head group of the phospholipid agent present within the conjugate which also in turn affects the silencing efficiency of the siRNA. The combination of carbon nanotubes and cationic lipids for the delivery of polynucleotides and other biologically relevant cargos remains largely uninvestigated leaving several possibilities open for further optimization.
9:00 PM - PP6.25
Towards the Detection of Cocaine and Crack by a Single Molecule.
Claire Seillan 1 , Vincent Grand 2 , Olivier Siri 1
1 , Aix-Marseille University, Marseille France, 2 , Laboratory of the Scientific Police, Marseille France
Show AbstractObtained from the leafs of coca and being presented in the form of a white powder, cocaine is the most tested illicit substance if the cannabis is excluded. The crack is a form derived from the cocaine, obtained by bicarbonate addition. The diffusion of cocaine and crack does not cease widening for 10 years, that it is in festive space or urban space. Since it is not possible to distinguish visually sugar, salt, crack or cocaine, it appeared necessary to examine the presumptive drug substances in a laboratory. Thus, the development of a chemical test for cocaine and crack identification is of major interest in order to fight against the expansion of these drug-addictions.The basicity is a fundamental property of cocaine and crack so that specific acid-base reactions accompanied by a radical colour change could be a solution for their identication. Consequently, the molecular structure of these indicators should have two different acido-basic sites (protonation / deprotonation) conjugated with two independent pi subunits (colour change upon protonation / deprotonation). Herein, we wish to report the development of a new colorimetric test that should specifically identify cocaine and crack by acid-base reaction in a single molecule.
9:00 PM - PP6.26
Light Harvesting Photosynthetic-nanocrystal Assemblies.
Joseph Slocik 1 , Alexander Govorov 2 , Rajesh Naik 1
1 , AFRL, Dayton, Ohio, United States, 2 , Ohio University, Athens, Ohio, United States
Show AbstractThe production of biofuels using photosynthetic algae and bacteria is limited by the strikingly low conversion efficiencies of natural photosystems. One way to overcome the limitation of natural photosystems is to employ artificial nanomaterials (such as nanoparticles or quantum dots) to enhance the light-harvesting process for the natural photosynthetic components. In this complex, solar photons are absorbed by the nanomaterial and then transferred to PS-II where electron-hole pairs become rapidly and efficiently separated. Consequently, photosystem II from spinach was assembled with optically-active nanocrystals to form photosystem-quantum dot hybrid complexes with enhanced optical properties. We will present results in the assembly and characterization of the photosystem-quantum dot hybrid complexes. In addition we will include modeling results to describe the experimental data for absorption and photoluminescence observed for the complexes.
9:00 PM - PP6.27
Optical and Mechanical Characteristics of Nanofiber Gels With Arrayed DNA.
Shi Hyeong Kim 1 , Min Kyoon Shin 1 , Seon Jeong Kim 1
1 Center for Bio-Artificial Muscle and Department of Biomedical Engineering, Hanyang University, Hanyang University, Seoul Korea (the Republic of)
Show AbstractThe incorporation of deoxyribonucleic acid (DNA) molecules into polymers has attracted much interest for pharmaceutical and medical applications. Optical and mechanical investigations of DNA molecules isolated in nanofiber gels are very useful in understanding their molecular dynamics and developing single-molecule genomic analysis techniques. In this work, we have fabricated poly(vinyl alcohol) (PVA) nanofiber gels embedding DNA without chemical cross-linkers using electrospinning. We observe the DNA molecules arrayed in the nanofiber gel using fluorescence microscopy. We investigate mechanical properties of the PVA/DNA nanofiber gels in de-ionized water and analyze a viscoelastic model of the gels in order to elucidate bonding interactions between DNA and PVA chains.
9:00 PM - PP6.29
Aptamer Nano-flares for Molecular Detection in Living Cells.
Dan Zheng 1 2 , Dwight Seferos 2 , David Giljohann 1 2 , Pinal Patel 1 2 , Chad Mirkin* 2
1 Interdepartmental Biological Sciences Program, Northwestern University, Evanston, Illinois, United States, 2 Chemistry, Northwestern University, Evanston, Illinois, United States
Show AbstractWe demonstrate a composite nanomaterial, termed an aptamer nano-flare, that can directly quantify an intracellular analyte in a living cell. Aptamer nano-flares consist of a gold nanoparticle core functionalized with a dense monolayer of nucleic acid aptamers with a high affinity for adenosine triphosphate (ATP). The probes bind selectively to target molecules and release fluorescent reporters which indicate the presence of the analyte. Additionally, these nanoconjugates are readily taken up by cells where their signal intensity can be used to quantify intracellular analyte concentration. These nanoconjugates are a promising approach for the intracellular quantification of other small molecules or proteins, or as agents that use aptamer binding to elicit a biological response in living systems.
9:00 PM - PP6.3
Biopreparation of Highly Dispersed Pd Nanoparticles on Bacterial Cell and Their Catalytic Activity for Polymer Electrolyte Fuel Cell.
Takashi Ogi 1 , Ryuichi Honda 1 , Koshiro Tamaoki 1 , Norizo Saito 1 , Yasuhiro Konishi 1
1 chemical engineering, Osaka Prefecture University, sakai, 599-8531, Japan
Show AbstractSupported metal nanoparticles catalysts are used in a large number of commercially important applications, including hydrogenation, dehydrogenation, naphtha reforming, isomerization, hydrocracking, oxidation, automotive exhaust catalysts, and fuel cells. In this study, highly dispersed palladium nanoparticles on bacterial cell support were successfully prepared by microbial method using the metal ion reducing bacterium Shewanella oneidensis. Resting cells of S. oneidensis were able to reduce Pd ions into insoluble palladium at room temperature and neutral pH within 60 min when formate was provided as the electron donor. TEM analysis of thin section of S. oneidensis cells after exposure to PdCl2 solution revealed that palladium particles approximately 5-10 nm in size were deposited at the bacteria surface and in the periplasmic space. The concentrations of formate and initial Pd ions in the precursor solution strongly influence on the reduction rate of aqueous Pd ions, size and dispersity of the biogenic particles. The prepared biomass – supported Pd nanoparticles were characterized for their catalytic activity as anodes in polymer electric membrane fuel cell for power production. The maximum power generation of biogenic palladium nanoparticles was as high as 90% of that of the commercial palladium nanoparticles catalyst.
9:00 PM - PP6.30
Graphene-binding Peptides Identified By Phage Display.
Laurie Wissler 1 , Sharon Jones 1 , Rajesh Naik 1
1 , AFRL, WPAFB, Ohio, United States
Show AbstractGraphene is a two-dimensional planar arrangement of carbon atoms that has recently been identified as a promising nanomaterial and is considered for a variety of applications including biosensing and nanoelectronics. Similar to previous research exploring peptide interactions with other nanomaterials, including carbon nanotubes (CNTs), for surface functionalization and assembly, we screen for peptides that bind to graphite and graphene. We used combinatorial peptide-displaying phage libraries to identify peptides that bind to graphene. The amino acid sequences of the graphene-binding peptides will be compared to sequences that bind to other carbon nanomaterials. In addition, we will present studies on characterizing the interactions. Peptides identified in this study could have potential for the surface functionalization of graphene and its impact on electronic and mechanical properties.
9:00 PM - PP6.31
Biologically-inspired Selective Trinitrotoluene Sensors Using Polymerized Lipid Membrane Coated Carbon Nanotubes.
Tae Hyun Kim 1 2 , Justyn Jaworski 2 3 , Keisuke Yokoyama 4 , Woo-Jae Chung 1 2 , Seunghun Hong 9 , Arun Majumdar 5 6 7 , Seung-Wuk Lee 1 2 8
1 Bioengineering, University of California, Berkeley, Berkeley, California, United States, 2 Physical Biosciences Divisions, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Joint Graduate Group in Bioengineering, University of California, Berkeley, and University of California, San Francisco, California, Berkeley, California, United States, 4 , NSK Ltd, Tokyo Japan, 9 Physics and Astronomy, Seoul National University, Richland, Washington, United States, 5 Department of Mechanical Engineering, University of California, Berkeley, Berkeley, California, United States, 6 Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, California, United States, 7 Materials Sciences Divisions, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 8 , Berkeley Nanoscience and Nanoengineering Institute, Berkeley, California, United States
Show AbstractMiniaturized smart sensors which can perform sensitive, selective and real-time monitoring of target analytes are tremendously valuable in various sensing applications. We developed selective nanocoating materials by combining lipid-like polydiacetylene (PDA) polymers carrying tripeptide TNT receptors for single-walled carbon nanotube-field-effect transistors (SWNT-FET) based microelectronic devices. The TNT receptor was discovered through phage display. Selective binding events between the TNT receptors and the target TNT molecules were effectively transduced to sensitive SWNT-FET conductance sensors through the PDA coating layers. The resulting sensors exhibited an excellent selectivity with 1 fM sensitivity in real time. Our biomimetic receptor coating approaches might be useful for the development of selective micro- and nanoelectronic sensor devices for the various other target analytes with little loss of their sensitivity.
9:00 PM - PP6.32
Electrochemistry of ZnO Nanowire Bioelectronic Systems.
Aron Rachamim 1 , Justin Pahara 2 , R. Ranjith 1 , Tim Wilkinson 1 , Andrew Flewitt 1 , Elizabeth Hall 2
1 Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge United Kingdom, 2 Institute of Biotechnology, Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge United Kingdom
Show AbstractExploiting the electrochemical properties of biochemical systems in bioelectronic devices is a means for advanced environmental- and health-associated detection, as well as prospective generation of renewable energy. In order to optimize the accuracy and sensitivity of bioelectronic sensors and to increase the efficiency of electron capture in the electrode in renewable energy applications, electron transfer at the biomolecular-solid state interface must be fully understood. The composition of the electrode alters the nature of biomolecule-electrode interaction and based upon these physical interactions, electrochemical processes are either promoted or inhibited. Furthermore, properties such as conductivity, resistivity, electron density, and electron mobility alter the effectiveness of the bioelectronic devices. We present the components for a bioelectronics device based on zinc oxide nanowires (NWs). Zinc oxide is a suitable electrode material for light sensing/harvesting applications because it is transparent in the visible and near-UV light spectrum so it will not obstruct the transmission of sunlight to the protein. Also, high surface-to-volume structures such as nanowires (1:100 aspect ratio) can be grown cheaply from solution. This allows maximal area for binding of proteins to the surface where they can pass electrons. Because grown ZnO structures are naturally n-type, they have high conductivity for electrons. Most proteins that are of interest in bioelectronic applications contain redox cofactors such as flavin adenine dinucleotide (FAD). Therefore it is of strong relevance to investigate the transfer of charge from these motifs to nanostructures such as ZnO NWs and establish the nature of interactions.The device consisted of gold pixels onto which a ZnO seed layer (~7 nm) was deposited by RF sputter. Subsequent immersion in equimolar zinc nitrate hexahydrate/HMTA solutions (0.025 M) for 5 hours led to coverage of the surface with a dense layer of nanowires. The investigations utilized cyclic voltammetry, which has only recently been implemented for analyzing ZnO NW electrochemistry with biological systems. With FAD as the analyte, it was found that electron transfer occurs between the ZnO NW functionalized gold electrode and FAD. Preliminary data also demonstrates that the current density of FAD oxidation and reduction is not proportional to the root of the scan rate and thus rules out linear diffusion electrochemistry on a macroelectrode. Lastly, the peak anodic and cathodic currents are larger in the ZnO NW electrode compared to the flat gold electrode. This work provides evidence that inorganic ZnO NWs support charge transfer with FAD cofactor, which indicates their potential for integration into redox protein bioelectronics.
9:00 PM - PP6.34
Developing Optical Probes For The Cell Interior.
Chong Xie 1 , Lindsey Hanson 2 , Bianxiao Cui 2 , Yi Cui 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 Chemistry, Stanford University, Stanford, California, United States
Show AbstractAs knowledge of the bulk behavior of biological systems continues to grow, there is an increasing demand for investigation into cellular processes at the single-molecule level. This presents a unique challenge in the dynamic nature of the system and the inability to modulate the concentration of the target species. We have fabricated vertical silicon dioxide nanopillars at a height of up to 1 μm and a diameter of 150 nm on substrates. The sub-wavelength dimension of these nanopillars provides a local excitation source for single-molecule fluorescence imaging. When cells are cultured on the nanopillar substrate, the cells readily engulf the nanopillars and exhibit survival rates comparable to standard cell culture. The pillars can also be specifically functionalized with molecules of interest, either for delivery into the local environment or study while tethered in the observation volume. Due to their optical properties and close interaction with cells, the nanopillars serve as optical probes for single-molecule fluorescence in the cell environment where biologically relevant molecular processes occur.
9:00 PM - PP6.35
Nanoporous Membrane Based Electrochemical Immunoassays: Model System for Evaluating the Impact of Nanoscale Confinement on Protein Detection.
Srivatsa Aithal 1 , Shalini Prasad 1
1 Center for Solid State Electronics Research, Arizona State University, Tempe, Arizona, United States
Show AbstractThe term 'macromolecular crowding' in cellular biological systems refers to the non-specific influence of steric repulsions on specific reactions and processes that occur in highly volume-occupied media. Experimental and theoretical work over the past decade has demonstrated substantial (order-of-magnitude) effects of crowding on a broad range of biochemical, biophysical and physiological processes, including—but not limited to—nucleic acid and protein conformation and stability, protein–protein and protein–DNA association equilibria and kinetics (including protein crystallization, protein fibre formation and bundling), catalytic activity of enzymes and cell volume regulation. The aim of the project is understand the impact of mimicking the behavior of macromolecular crowding in enhancing the performance of label free electrochemical immunoassays for protein biomarker profiling and detection.Nanoporous alumina membranes of controlled dimensions are incorporated on to microscale platforms to generate a model diagnostic platform comprising of high density arrays of nanoscale confined spaces. The diameters, pore density as well as the pore depth of the membrane are varied to evaluate the role of nanoscale confinement of biomolecules on the detection sensitivity of the diagnostic platform. The mutual impenetrability of protein molecules, due to the Pauli exclusion principle, is arguably the most fundamental intermolecular interaction. In fact, its ubiquity cause steric repulsions to be taken for granted and their consequences to be overlooked. However, the activity of a protein molecules depends strongly on the volume that is available to the centre of mass of each molecular species. Hence we evaluate the impact of nanoscale confinement by using a standard inflammatory protein biomolecule system.
9:00 PM - PP6.36
Surface Modification of Magnetic Nanoparticles Using a Polypeptide Designed to Control Interactions With Cell Surfaces.
Tomoko Yoshino 1 , Masayuki Takahashi 1 , Tadashi Matsunaga 1
1 , Tokyo University of Agriculture and Technology, Tokyo Japan
Show AbstractMagnetic nanoparticles, which are now essential components in many cell-associated applications, have high surface area to volume ratios, and surface modification is a fundamental and important aspect of nanoparticle fabrication. Surface modification for use in cell-associated applications has been based on two concepts. First, magnetic nanoparticles with the capacity to recognize and bind target cells have been prepared by association of modified cell recognition molecules, such as antibody, with the particle surface. Second, to minimize nonspecific adsorption of magnetic nanoparticles to the surface of cells, various molecules, such as polyethylene glycol (PEG), have been attached to the particle surface. Previous reports have shown separately that the hydrophilicity or neutral charge of the particle surface is important to reduce nonspecific interactions between the magnetic nanoparticle and the cell surface. Here we have designed a novel polypeptide that is polar and uncharged and functions to minimize nonspecific adsorption of magnetic nanoparticles to cell surfaces. The polypeptide designed is composed of multiple units consisting of four asparagine (N) and one serine (S) residue and is referred to as the NS polypepeptide. NS polypeptide, which is 100 amino acids in length, was displayed on bacterial magnetic nanoparticles via genetic engineering (magnetic nanoparticles were synthesized in magnetotactic bacterium). Modification of the particle surface with the NS polypeptide results in reduction of particle-particle and particle-cell interactions. When NS polypeptide is used in single fusion protein as a linker to display protein G on magnetic nanoparticles, the particle acquires the capacity to specifically bind target cells and to avoid nonspecific adsorption of non-target cells. This technology, incorporating a functional polypeptide, may represent a completely new strategy for surface modification of magnetic nanoparticles for use in a variety of cell-associated applications.
9:00 PM - PP6.4
Solvent and Ligand Influence on the Energetics and Optical Transitions in Small Gold Clusters.
Satyender Goel 1 2 , Kirill Velizhanin 2 , Andrei Piryatinski 2 , Sergei Tretiak 3 , Sergei Ivanov 3
1 NanoScience Technology Center and Department of Chemistry, University of Central Florida, Orlando, Florida, United States, 2 Theoretical Division and Center for Non-Linear Studies, Los Alamos National Lab, Los Alamos, New Mexico, United States, 3 Center for Integrated Nano-Technologies, Los Alamos National Lab, Los Alamos, New Mexico, United States
Show AbstractSmall gold clusters hold promises for the great advances in materials science as they increasingly form the basis for assembly of nanoarchitectures having specific emergent properties. Their ability to guide, enhance, emit, and modify optical fields put them on center stage for applications like photonic crystals, bio-sensors and optical materials. In experimental studies assignment of the observed spectra is tedious without the knowledge of geometries and energy levels, and as such, theoretical studies can provide invaluable microscopic insight into the electronic structure and dynamics of these nanoclusters. This study provides the comprehensive analysis of how ligand and solvation affect the geometry and energetics of ten isomers of four small gold clusters with a systematic one-by-one attachment of surrounding ligand to the optimized bare gold cluster geometry. Our calculations were carried out using Density functional theory (DFT) implemented in Gaussian 03/09 software package. The structure optimization is performed with five generations of density functionals (SVWN5, PBEPBE, TPSSTPSS, B3LYP and CAM-B3LYP) combined with effective core potentials and corresponding valance basis set (LANL2DZ). The search for global minima of small clusters (Au2, Au4, Au6, Au8) provides an insight to correct the long standing discrepancy of non-ligated clusters through the ligand induced stability of otherwise less stable isomers. Our study reveals the 2D→3D transition happening at Au6 which is even lower than much debated size of Au8 and Au13. To make the direct comparison of this study with the experiments, we have also calculated the absorption spectra of these ligated small gold clusters.
9:00 PM - PP6.5
Biodegradable Multilayer Nanoshells of Poly(lactic acid) Nanoparticles.
Veronika Kozlovskaya 1 , Eugenia Kharlampieva 1 , Victor Orozco 3 , Betty Lopez 3 , Vladimir Tsukruk 1 2
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Groupo Ciencia de los Materiales, Universidad de Antioquia, Medellín, Antioquia, Colombia, 2 Textile and Fiber Engineering , Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractBiodegradable hollow nanoshells of poly(lactic acid) nanoparticles (PLA) were fabricated via layer-by-layer (LbL) assembly into ultrathin multilayer coatings on silica particles through hydrogen-bonding or ionic interactions. Chemical cross-linking of the produced LbL shell with a bifunctional amine crosslinker resulted in robust, raspberry-like PLA shells. Preparation of PLA nanoparticles in the presence of poly(ethylene imine) resulted in amine functionalization of the PLA nanoparticles surface favorable for multilayer formation with poly(carboxylic acid)s. The amine functionalities present in the shells were explored for the reduction of gold nanoparticles within the shells via either UV-initiated reduction or under mild environmental conditions without additional reducing agent for further modification of the PLA shells through thiol-based surface chemistry. We found that unlike the UV-based reduction, the later method is able to produce stable gold-containing PLA nanoshells with plasmonic properties. Finally, enzymatic degradation of PLA-Au multilayer films was studied in the presence of α-chymotrypsin using UV-visible and ATR-FTIR spectroscopy methods.
9:00 PM - PP6.6
Surface Modification Routes Towards Water Soluble Upconversion Nanoparticles.
Sounderya Nagarajan 1 , Zhengquan Li 1 , Victor Roullier 2 , Marian Amela Cortes 2 , Muthu kumar Gnanasamandham 1 , Fabien Grasset 2 , Valerie Artzner 2 , Yong Zhang 1
1 Division of Bioengineering, National University of Singapore, Singapore Singapore, 2 Sciences Chimiques de Rennes ,UMR 6226, Université de Rennes 1, Rennes, Brittany, France
Show AbstractUpconversion nanoparticles are nanocrystals doped with lanthanides that absorb near infrared light (NIR) and exhibit emission in the visible region. Their optical properties, such as excitation in NIR wavelength, narrow emission peak tunable with the type of lanthanide doping, low cytotoxicity make them a suitable candidate for biological imaging[1-2].Upconversion nanoparticles consisting of NaYF4 nanocrystal doped with Er3+ and Yb3+ ions were synthesized by a one-pot synthesis[3]. The obtained hydrophobic nanoparticles were well-defined in size (diameter:30nm) and shape.In view to apply these materials to biological systems,nanoparticles were solubilized in water by different chemical strategies: silica coating, ligand exchange and micellization.Their optical properties as well as the size and morphology were analyzed by UV-Vis spectrophotometry,fluorescence spectroscopy, light scattering and transmission electron microscopy. All of the employed modification strategies allow further chemical functionalization and conjugation of biomolecules. By silica coating, core/shell structures of size (diameter 50nm) were obtained and they were further conjugated with a specific antibody and tested on live cardiac cells[4].The micellization method used amphiphiles with amine and carboxylic functionality to encapsulate the nanoparticles[5].It was possible to introduce biotin functionality onto the micelles which enables conjugation of molecules to match specific needs. The obtained micellar structures had multiple particles encapsulated in them and the size was of the order of 100nm.Polydispersity was observed as the number of particles encapsulated in each micelle varied. The ligand exchange method involved the exchange of the oleic acid groups on the hydrophobic UCN with citrate groups to make them hydrophilic. This method was interesting as the size after modification would be comparable to the hydrophobic UCN size (30nm).Further biofunctionalization of these materials could make possible to apply them to biological systems.1 Shan, J. et al. (2009) NIR-to-visible upconversion nanoparticles for fluorescent labeling and targeted delivery of siRNA. Nanotechnology (15), 1551012 Chatterjee, D.K. et al. (2008) Upconversion fluorescence imaging of cells and small animals using lanthanide doped nanocrystals. Biomaterials 29 (7), 937-9433 Li, Z. and Zhang, Y. (2008) An efficient and user-friendly method for the synthesis of hexagonal-phase NaYF4:Yb, Er/Tm nanocrystals with controllable shape and upconversion fluorescence. Nanotechnology 19 (34), 3456064 Sounderya, N. and Zhang, Y. (2008) Use of core/shell structured nanoparticles for biomedical applications. Recent Patents on Biomedical Enigneering 1 (1), 34-425 Roullier, V. et al. (2008) Small Bioactivated Magnetic Quantum Dot Micelles. Chemistry of Materials 20 (21), 6657-6665
9:00 PM - PP6.7
The Cytotoxicity of Au Nanoparticales Modified With Self-assembled Monolayers With Mixed-functional Groups to Living Cells.
Hsun-Yun Chang 1 , Yun-Wen You 1 , Yu-Chin Lin 1 , Wei-Chun Lin 1 , Chia-Yi Liu 1 , Che-Hung Kuo 1 2 , Szu-Hsian Lee 1 2 , Wei-Lun Kao 1 2 , Guo-Ji Yen 1 2 , Chi-Ping Liu 1 3 , Jing-Jong Shyue 1 2
1 Research Center for Applied Sciences, Academia Sinica, Taipei Taiwan, 2 Materials Science and Engineering, National Taiwan University, Taipei Taiwan, 3 Materials Science and Engineering, National Tsing Hua University, Hsinchu Taiwan
Show AbstractNanoparticles are widely researched on cell therapy through attaching to cells and delivering interesting cargos. Gold nanoparticles (AuNPs) are known as good carriers for its easy of synthesis and conjugation to biochemistry. Self-assembled monolayers (SAMs) provide a tunable system to change the interfacial properties of AuNPs, so that SAM-modified AuNPs can be used to transport biological molecules including DNA and proteins. However, these molecules are usually covalently bounded to the surface of AuNPs and required to cleavage inside the living cells in order to release the cargo. It might be better to use electrostatic interactions to immoblilize molecules. In order to control the electrostatic interaction, AuNPs modified with SAMs with mixed carboxylic acid and amine functional groups and made in a series of surface potential and the iso-electric point (IEP) is presented in this work. By changing the environmental pH, molecules could be triggered to adsorb or desorb based on the flip of surface charge. Based on different pH inside and outside of living cells, we expect that molecules can be transported by electrostatic interactions with SAM-modified AuNPs. However, it is not clear whether SAM-modified AuNPs with mixed functional group have deleterious effect on living cells. Therefore, cellular uptake and cytotoxicity of SAM-modified AuNPs with mixed functional group is examined in this work.
Symposium Organizers
Rein V. Ulijn University of Strathclyde
Molly M. Stevens Imperial College London
Rajesh R. Naik Air Force Research Laboratory
Phillip B. Messersmith Northwestern University
PP7: Dynamic Systems
Session Chairs
Thursday AM, April 08, 2010
Room 3022 (Moscone West)
9:30 AM - **PP7.1
Orthogonal Chemoligations on Responsive Microgels.
Andrew Lyon 1 , Marshall Johnson 1 , Zhiyong Meng 1
1 School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractWe describe one-step and multi-step syntheses of “clickable” multi-responsive, core/shell microgels containing both carboxylic acid groups and azidohydrin or terminal alkyne groups. The clickable functional groups on the microgels were confirmed by FTIR and fluorescence labeling studies. These particles permit simultaneous “click” and acid-amine coupling reactions on microgels with fluorescent dyes, proteins, or biological ligands containing complementary functional groups. Epifluorescence microscopy was employed to confirm the coupling and bioactivity of those moieties to the microgels. Furthermore, these particles are excellent building blocks for the assembly of functional polymer thin films via self-assembly methods. The orthogonality of the click reaction to other functional groups, such as hydroxyl, carboxylic acid, and amino groups was confirmed, suggesting the potential utility of such microgels in applications where multifunctional colloidal particles and polymeric thin films are required.
10:00 AM - PP7.2
Magnetically-triggered Release from Hydrogel-supported Nanoparticle-vesicle Assemblies.
Kwan Ping Liem 1 , Robert Mart 3 , Felicity Leng 1 2 , Julie Gough 2 , Simon Webb 1
1 MIB and School of Chemistry, University of Manchester, Manchester United Kingdom, 3 School of Chemistry, Cardiff University, Cardiff United Kingdom, 2 School of Materials, University of Manchester, Manchester United Kingdom
Show AbstractThe creation of structurally defined assemblies of vesicles (simple cell mimics) that mimic the form and function of tissue is an elusive goal, as the resulting assemblies often lack the functionality and mechanical stability to be viable biomaterials. Structural reinforcement can be introduced by forming a hydrogel extravesicular matrix but to elaborate these “vesicle gels” into tissue-mimetic structures, cell-cell adhesion must be replicated, the resulting vesicle assemblies must be patterned and a mechanism for the controlled release of vesicle contents must be added.To address these issues we have developed magnetic vesicle gels, a new type of biomaterial that contains magnetic nanoparticle-vesicle assemblies embedded within a calcium alginate matrix. Crosslinking 10 nm diameter magnetite nanoparticles with 800 nm diameter adhesive vesicles provided vesicle assemblies up to 200 μm in diameter, which could be magnetophoretically manipulated. Application of external magnetic fields created patterns of vesicle assemblies, which could then be fixed by gelation of the surrounding alginate solution. Cryo-ESEM revealed the calcium alginate gel fibrils of the gel did not insert into or compromise the vesicle membranes, and at 20 °C these magnetic vesicle gels showed excellent retention of compounds stored in the vesicles. However these stored compounds could be released upon application of a 392 kHz alternating magnetic field, which “melted” the vesicle membranes and released their contents without heating of the bulk material.The non-destructive magnetic release of chemical messengers from these biocompatible vesicle gels can transform remote magnetic signals into cellular responses. These magnetic vesicle gels can support cell proliferation, for example 3T3 fibroblast growth was supported by calcium alginate vesicle gel doped with 0.1 % fibronectin. The cells were unaffected by co-location with the magnetic nanoparticle-vesicle assemblies, even when the assemblies contained toxins like Ni(II). However exposure to an alternating magnetic field released the Ni(II), inducing apoptosis in the 3T3 fibroblasts cultured in the gel. The combination of magnetic patterning and magnetically induced release gives these materials many potential applications, from smart scaffolds for stem cells to remotely triggered in vivo drug delivery systems.(1). R.J. Mart, K.P. Liem, S.J. Webb, Chem. Commun. 2009, 2287. (2) K.P. Liem, R.J. Mart, S.J. Webb, J. Am. Chem. Soc, 2007, 129, 12080.
10:15 AM - PP7.3
Coiled-coil Motifs Applied to Polymer Self-assembly.
Alexander Kros 1
1 LIC, Leiden University, Leiden Netherlands
Show AbstractThe formation of a non-covalent triblock copolymer based on a coiled-coil peptide motif is demonstrated in solution for two systems. In the first example a specific peptide pair (E and K) able to assemble into hetero coiled-coils was chosen as the middle block of the polymer and conjugated to poly(ethylene glycol) (PEG) and polystyrene (PS) as the outer blocks. Mixing PS-E with equimolar amounts of K-PEG resulted in the formation of coiled-coil complexes between the peptides and subsequently in the formation of an amphiphilic triblock copolymer (PS-E/K-PEG). It was shown that the non-covalent PS-E/K-PEG assembled into rod-like micelles while in all other cases spherical micelles were observed. In another example the coiled-coil motif was used to control the self-assembly properties of non-covalent PBLG-E/K-PEG triblock copolymers resulting in polymer vesicles or bicelles depending on the exact composition of the polymer. Possible applications will be discussed.
10:30 AM - PP7.4
Phosphopantetheinyl Transferase-mediated Formation of Bioactive Hydrogels.
Katarzyna Mosiewicz 1 , Kai Johnsson 1 , Matthias Lutolf 1
1 Ecole Polytechnique Federale de Lausanne (EPFL), Institute of Bioengineering, Lausanne Switzerland
Show AbstractMild and highly selective crosslinking chemistries are crucial for the performance of state-of-the-art hydrogel biomaterials. Since these materials often need to be crosslinked and functionalized in the presence of cells or biomolecules, the lack of selectivity in gel crosslinking invariably results in significant cell death or biomolecule inactivation. Consequently, a variety of chemical schemes have been exploited to overcome these complexities, including selective covalent chemical reactions or clever supramolecular crosslinking schemes.(Ref.1) Surprisingly, apart from transglutaminase-mediated crosslinking,(Ref.2,3) posttranslational modification reactions have been underexplored for the synthesis of synthetic biomaterials.Here we present an approach by which phosphopantetheinyl transferase (PPTase), a small (16.2 kDa) enzyme that plays a key role in the biosynthesis of many natural products, was employed to catalyze covalent cross-linking of poly(ethylene glycol) (PEG)-based hydrogels. Gels were formed within minutes under physiological conditions by mixing two aqueous precursors containing multiarm PEG macromers end-functionalized with the PPTase substrate Coenzyme A (CoA), and a genetically engineered dimer of a carrier protein (CP-CP). The physicochemical properties of this new class of biomaterials were characterized. Furthermore, bioactive hydrogels were produced by covalent incorporation of a CoA-functionalized cell adhesion peptide (RGDS), resulting in specific adhesion of primary human fibroblasts on the hydrogel surfaces. Therefore, PPTase is well suited to catalyze selective hydrogel formation and modification with bioactive molecules. We envision a wealth of useful applications of this new gel system in cell biology and tissue engineering.References: (1) Hennink, W. E. et al. Adv Drug Deliv Rev 2002; (2) Hu, B. H. et al. J. Am. Chem. Soc. 2003; (3)Ehrbar, M. et al. Biomaterials 2007
10:45 AM - PP7.5
Dynamic Constitutional Membranes: Toward an Adaptive Facilitated Transport.
Mihail Barboiu 1
1 , Institut Europeen des Membranes, Montpellier France
Show AbstractNumerous artificial transport systems utilizing carriers, channel-forming or self-organized polymeric superstructures able to orient, to select and to pump the ionic transport across membranes have been developed in the last decades. Artificial membrane materials are the subject of various investigations, offering great potentialities as well on the level of their chemical composition or organization as to that of the concerned applications. Of special interest is the structure-directed function of biomimetic and bioinspired membrane materials and control of their build-up from suitable units by self-organisation. The main interest focus on functional biomimetic membranes in which the recognition-driven transport properties could be ensured by a well-defined incorporation of receptors of specific molecular recognition and self-organization functions, incorporated in a hybrid dense or mesopourous materials.We are therefore proposing to review the membrane transport properties of such supramolecular membrane materials.The first part begins with a survey of different methods and processes which can be used for the generation of molecular recognition-based hybrid materials. Then basic working principles of self-organized membranes are provided in order to better understand the requirements in material design for the generation of functional membrane materials.These results describe the simple synthetic hybrid biomaterials which successfully formed molecular recognition devices, transport patterns so as to enable efficient translocation events. Finally actual and potential applications of such self-organized systems presenting combined features of structural adaptation in a specific nanospace will be presented. From the conceptual point of view these membranes express a synergistic adaptative behaviour: the addition of the fittest solute (ions, molecules and gaz, etc) drives a constitutional evolution of the membrane toward the selection and amplification of a specific transporting superstructure in the presence of the solute that promoted its generation in a first time. This is the interesting example of dynamic evolutive membranes, where a solute induces the upregulation of (prepares itself) its own selective membrane.1. M. Barboiu, S. Cerneaux, G. Vaughan, A. van der Lee, J. Am. Chem. Soc. 2004, 126 3545-3550.2. A. Cazacu, A. van der Lee, T.M. Fyles, M. Barboiu, J. Am. Chem. Soc. 2006, 128(29), 9541-9548. 3. C. Arnal-Herault, M. Michau, M. Barboiu, Angew. Chem. Int. Ed. 2007, 46, 8409-8413. 4. C. Arnal-Hérault, M. Barboiu, A. Pasc, M. Michau, A. van der Lee, Chem. Eur. J. 2007, 13, 67925. C. Arnal-Herault, A. Pasc-Banu, M. Barboiu Angew. Chem. Int. Ed. 2007, 46, 4268-4272.6. M. Barboiu, P. Aimar, J.-M. Lehn, J. Memb. Sci., 2008, 321, 1-2; (b) J. Memb. Sci., 2008, 321, Special issue : From simple molecules to complex membrane systems.7.Cazacu, A. et al. Proc. Natl. Acad. Sci., 2009, 106(20), 8117.
11:00 AM - PP7: Dynamic
BREAK
11:30 AM - PP7.6
Recognition-driven Actuation of Lipid Domains, Nano-tubules, and Self-assembled Networks.
Jeanne Stachowiak 1 , Carl Hayden 1 , Darryl Sasaki 1
1 , Sandia National Laboratories, Livermore, California, United States
Show AbstractCell membranes are dynamic substrates that achieve a diverse array of functions through multi-scale reconfigurations. Cells delicately orchestrate the size, location, number, and lifetime of diverse membrane structures. Greater understanding of how this extraordinary coordination is accomplished is needed not only to understand cellular processes but also to identify principles that could be used to assemble programmable soft-material structures and networks. Recently, adaptable membrane assemblies such as lipid domains, buds, and tubules have attracted interest as controllable nanomaterials including scaffolds for biological–synthetic hybrid materials and conduits to move species within nano-fluidic networks. However, well-controlled methods for the self-assembly of complex membrane structures and networks have yet to emerge. We explore a range of reversible lipid membrane morphological changes using metal-ion recognition and lipid-protein binding to supported lipid bilayers (SLBs) and giant unilamellar vesicles (GUVs). SLBs composed of an iminodiacetic acid functionalized lipid, DSIDA, in a POPC matrix exhibited switchable properties via Cu2+ recognition to rapidly assemble and disassemble sub-micron domains that act as high affinity sites for His-tagged protein binding. The enhanced protein affinity exhibited by these domains in comparison to homogeneous membranes highlights the important role that reversible domains could play in cellular signaling. Further, these domains could be used as reconfigurable substrates that actuate assembly and information transfer in biomolecular materials. When his-tagged proteins were bound to GUVs containing micron-scale domains, crowding of bound proteins on domain surfaces caused spontaneous deformation of the domains into stable lipid buds and tubules. Tubule formation relied upon the presence of lipids with high spontaneous curvature in the domain and required a high density of protein attachment that was facilitated by proteins of smaller molecular weight. Most domains yielded a single tubule, and tubules frequently consumed the entire protein-bound domain such that the domain size tightly defined the size scale of membrane deformation. A simple physical analysis showed that this coupling is consistent with a globally limited membrane tension defined by protein-lipid binding energy. This simple synthetic model system demonstrates that lipid domains and other confining structures such as protein lattices could aid protrusions and define protrusion length scales by concentrating the steric interactions between the lipid bilayer and proteins. Further, these findings suggest an approach for polarizing and ordering lipid-based materials by self-assembly. Towards this goal, stable lipid tubule connections between giant vesicles were formed, where vesicle size and composition controlled tubule length.
11:45 AM - **PP7.7
Controlling Cellular Morphology Using Engineered Dynamic Nanostructured Substrates.
Joanna Aizenberg 1 , Michael Bucaro 1 , Benjamin Hatton 1
1 SEAS, Harvard University, Cambridge, Massachusetts, United States
Show AbstractAttaining appropriate cell morphology is essential for cell therapy since cell form modulates the interpretation of extracellular cues, impacting both phenotype stability and lineage specification. We produced orthogonal arrays of high aspect ratio nanoposts with a range of nano and micro topographical features. These structures were further functionalized by biomolecules. Murine mesenchymal stem cells were cultured on the substrates for up to 2 weeks and cell morphology was evaluated by SEM and live cell optical microscopy during seeding. We identified significantly higher polarization of cells and cellular processes on nanoposts relative to cells on a flat surface. The results indicate that nanopost arrays with tailored size, spatial distribution, and chemistry can be used to produce distinct morphological characteristics in stem cells that resemble neuronal architectures. Further studies are underway to utilize the nanopost arrays in a reciprocal system that both illicits cellular responses via topographical, chemical, and mechanical actuation, and at the same time probes the cell-surface interactions by mapping cell-matrix forces. Production of ordered bioactive surfaces by nanolithographic methods enables ordered bioactive surfaces with tunable nanoscale topology, chemistry and mechanical properties and is compatible with semiconductor fabrication. This approach can be used as a platform to probe cell-matrix interactions as well as direct cell behavior, for example, to form complex cellular networks in neural chips, enhance phenotype purity in stem cell lineage specification or illicit tissue-specific cell behavior for other regenerative medicine and tissue engineering applications.
12:15 PM - PP7.8
Photo-responsive Protein Nanococoon Weaved With Enzymatically Degradable Polymeric Network.
Zhen Gu 1 2 3 , Anuradha Biswas 1 2 , Ming Yan 1 2 , Pin Wang 4 , Yunfeng Lu 1 2 , Yi Tang 1 2
1 Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, California, United States, 2 California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California, United States, 3 Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, Los Angeles, California, United States, 4 Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California, United States
Show AbstractProtein therapeutics, including antibodies, cytokines, transcription factors and enzymes, are indispensible in healthcare and biomedical applications. Most protein-based drugs and drug candidates suffer from poor thermal stability, serum proteolysis, and inability to penetrate cell membranes. Therefore, increasing the robustness and efficacy of proteins through hybrid carrier-protein materials is an important goal. Here we present an approach to reversibly encapsulate proteins using a cocoon-like, enzymatically degradable polymeric nanocapsule, formed by physical adsorption based interfacial polymerization. The protective shell is crosslinked with peptides that can be disassembled via the specific actions of proteases, while the degradation process can be controlled in a spatiotemporal fashion through functionalization of the crosslinker with photolabile groups. Using this approach, we demonstrate the synthesis and implementation of caspase-3 nanococoon as a highly potent apoptotic agent to various cancer cell lines. The ease of preparation, high cell penetration capability, long-term stability, low toxicity, photo-responsive and protease-modulated specific degradability make this new protein delivery strategy useful in the preparation and administration of protein drugs, vaccines and other macromolecular therapeutics.
12:30 PM - PP7.9
Engineering Dynamic Surfaces of Single Molecule DNA Structures.
Eric Josephs 1 , Cheetar Lee 2 , Jingru Shao 2 , Janice Lianne Cosio 2 , Tao Ye 2
1 School of Engineering, University of California, Merced, Merced, California, United States, 2 School of Natural Sciences, University of California, Merced, Merced, California, United States
Show AbstractDNA is generally thought of solely as a biological information carrier, but precise control of its topology has allowed for the engineering of DNA assemblies as structurally well-defined tools able to perform work at the nanoscale. Chemical patterning of these nanotechnologies would integrate DNA devices as active components on surfaces, and allow us to obtain unprecedented control of the chemical environment around these devices for both single-molecule biophysical studies and on-demand activation of biochemical reactions. Here we report our nanometer-resolution patterning, observation, and manipulation of single DNA molecules on a chemically well-defined electrode surface by combining electrochemical atomic force microscopy (EC-AFM) and nanolithography. We can control DNA location and density over micrometer areas by replacing select nanometer-scale regions in a neutral surface monolayer with a layer of single, negatively-charged DNA molecules that are covalently linked to the gold substrate and diluted with surface-bound, positively-charged molecules. We demonstrate electrochemical switching of the strong resulting surface confinement of the chemisorbed DNA, which allows us to modulate the activity of catalytic DNAzymes by controlling the electrode potential. These results suggest that we can combine lithographic techniques with compatible ‘bottom-up’ molecular self-assembly to create complex and dynamic biotechnological surfaces with control over multiple, biologically-relevant length-scales. We will also discuss our work placing these DNA onto ultra-flat, transparent gold microelectrodes that we have grown on indium tin oxide substrates, for the purpose of integrating AFM nanolithography, single-biomolecule AFM imaging, and confocal microscopy of DNA nanodevices on electrodes.
12:45 PM - PP7.10
Mechanotransductive Surfaces for Reversible Biocatalysis Activation.
Cedric Vogt 2 1 , Damien Mertz 2 1 , Philippe Lavalle 1 , Pierre Schaaf 3 2 , Jean-Claude Voegel 1 2
2 , University of Strasbourg, Strasbourg France, 1 UMR 977 Biomaterials & Tissue Engineering, INSERM, Strasbourg France, 3 UPR 22 Institut Charles Sadron, CNRS, Strasbourg France
Show AbstractFibronectin, like other proteins involved in mechanotransduction, has the ability to exhibit recognition sites under mechanical stretch1. Such cryptic sites are buried inside the protein structure in the native fold and become exposed under an applied force, thereby activating specific signalling pathways. Here, we report the design of new active polymeric nanoassembled surfaces that show some similarities to these cryptic sites2. These nanoassemblies consist of a first polyelectrolyte multilayer3 stratum loaded with enzymes and capped with a second polyelectrolyte multilayer acting as a mechanically sensitive nanobarrier. In contact with enzyme substrate solution, the biocatalytic activity of the film is switched on/off by mechanical stretching:i) In the absence of stretching, no enzymatic activity is detected.ii) Once the film is stretched over a critical stretching degree, the embedded enzymes are exhibited and the enzymatic reaction takes place, catalyzing products formation and their delivery in the solution.iii) When returning to the unstretched state, the enzymes are again buried inside the film structure and the catalysis is switched off. The whole exhibition mechanism proves to be reversible, allowing switching between an activated and deactivated state of the surface, similarly to mechanisms involved in proteins during mechanotransduction.This first example of a new class of biologically inspired surfaces should have great potential in the design of various devices aimed to trigger and modulate chemical reactions by mechanical action with applications in the field of biomaterials, microfluidic devices or mechanically controlled biopatches for example.This study has recently been published in Nature Materials2.
PP8: Biofunctionalized Nanoparticles
Session Chairs
Thursday PM, April 08, 2010
Room 3022 (Moscone West)
2:30 PM - **PP8.1
On the Role of Interfacial Energy in Bio-interfaces.
Francesco Stellacci 1
1 Department of Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractSolid-liquid interfaces are of central importance in controlling such processes as protein dynamics, heterogeneous catalysis, trans-membrane trafficking, self-assembly, and electron transfer. Soft matter surfaces often are structured with domains of varying nature. This is especially true in molecular biology, where folded proteins present surfaces with nanometer-scale domains of varying hydrophobicity and polarity. It is generally accepted that such structures determine interfacial interactions and influence protein function, but an accepted framework providing a quantitative understanding is lacking. The conventional continuum thermodynamic approach of capillary theory (CCT) treats interfacial energy (IE) solely as a function of average surface composition, ignoring structure. Here we will show that when surfaces have nanometer scale structures the CCT can severely mis-estimate the IE. We present a combined experimental and computational study contrasting surfaces coated with mixed self-assembled monolayers that spontaneously microphase-separate into either molecular scale stripes (MSS, 0.5 to 2 nm) -or larger scale domains (LSD, 5-50 nm) of alternating composition. We determined the dependence of IE on surface composition using both macroscopic contact angles and nanoscopic atomic force microscopy. LSD surfaces show the linear dependence expected from CCT. In contrast for MSS, we find a non-monotonic trend deviating from the linear behavior by as much as 20%, due to the existence of an unanticipated yet strong structure effect on IE. We hypothesize the controlling factors, and using molecular dynamics simulations, show how the liquid interface morphology is determined by the nano-structured surface, which in turn modifies the IE from the molecular to the macroscopic scale. Our findings present a more complete view of the role of interfaces in nanoscale processes occurring in liquids.
3:00 PM - PP8.2
The Effects of Nanoparticles on the Fibrillation of Human Albumin.
Charles Vannoy 1 , Roger Leblanc 1
1 , University of Miami, Coral Gables, Florida, United States
Show AbstractNanoparticles (NPs) are extremely small in size and possess very large surface areas, which gives them unique properties and applications distinct from those of bulk systems. Taking this factor in consideration with the fact that the dynamic nature of proteins allows for adsorption to the NPs’ surface, then there is a significant possibility of an enhanced rate of protein fibrillation by utilizing the NPs as nucleation centers and, thus, promoting fibril formation. Protein fibrillation is closely associated with many fatal human diseases, including neurodegenerative diseases, type II diabetes, and a variety of systemic amyloidoses. This topic of protein-NP interaction brings about many key issues and concerns, especially with respect to the potential risks to human health and the environment. Herein, we demonstrate the effects of specific NPs, semiconductor quantum dots (QDs), in the process of protein fibril formation from samples of human albumin. The protein-NP systems are analyzed by time-lapse microscopy methods, optical spectroscopy, and circular dichroism (CD). Our experimental results illustrate that an increased rate of fibrillation occurs following a thermally activated mechanism in conjunction with the addition of NPs into the system. These results give rise to the understanding and possibility of controlling biological self-assembly processes for use in bionanotechnology and nanomedicine.
3:15 PM - PP8.3
Comparative Proteome Analysis Toward the Identification of Shape Control Factor of Bullet-shaped Bacterial Magnetic Nanoparticles.
Michiko Nemoto 1 , Atsushi Arakaki 1 , Tadashi Matsunaga 1
1 , Tokyo University of Agriculture and Technology, Tokyo Japan
Show AbstractMagnetic nanoparticles are widely used in the development of medical and diagnostic applications such as magnetic resonance imaging (MRI), cell separation, biosensing and hyperthermia. Several procedures for the controlled formation of uniformly sized magnetic particles at the nanometer scale have been developed. However, these methods require the use of organic solvents or extremely high temperatures. Magnetotactic bacteria produce fine magnetite crystals under physiological conditions. The sizes and morphologies of the nano-sized magnetite crystals are highly consistent within bacterial species or strains, suggesting the presence of a biologically controlled mineralisation process at the genetic level. Much attention has been focused on proteins associated with the organic membrane that envelops bacterially produced magnetite in order to analyse these precisely regulated molecular mechanisms. An example of such a protein associated to this membrane is the small acidic protein, Mms6 that is tightly associated with bacterial magnetite in Magnetospirillum magneticum AMB-1. In vitro analysis showed that Mms6 regulates the shape of the magnetite crystals into cubo-octahedral structures. However, most factors involved in the various processes of magnetite crystal formation within magnetotactic bacteria still remains unclear, and majority of the analyses conducted thus far have been limited to α-proteobacterial magnetotactic bacteria that produces cubo-octahedral magnetic nanoparticles. Desulfovibrio magneticus strain RS-1 is the only isolate of magnetotactic bacteria classified under the δ-proteobacteria. This bacterium synthesizes bullet-shaped magnetite crystals suggesting the presence of a unique biological regulation system of crystal morphology. In order to identify the shape control factor of magnetite crystals in strain RS-1, comprehensive proteomic analysis of magnetic nanoparticles, based on completed whole genome was conducted. As a result, total 190 proteins were identified from magnetic nanoparticles in strain RS-1. The identified magnetic nanoparticle membrane proteins were then compared with that of Magnetospirillum. sp.. Three proteins showed significant similarities with magnetic nanoparticle membrane specific proteins previously found in Magnetospirillum sp.. Furthermore, genes encoding ten magnetic particle membrane proteins, including novel proteins, were assigned to a putative genomic island that contains subsets of genes essential for magnetic nanoparticle formation. In addition, genes encoding two homologous proteins of Magnetococcus MC-1 were assigned to a cryptic plasmid of strain RS-1.Several novel proteins were identified as specific proteins in strain RS-1. These novel proteins might attribute to the formation of unique bullet-shaped crystals in strain RS-1.
3:30 PM - PP8.4
Superparamagnetic Nanoparticles for MRI: Optimized Contrast Agents for T1, T2, and T2 Weighted Imaging.
Ulrich Tromsdorf 1 , Oliver Bruns 2 , Elmar Poeselt 1 , Harald Ittrich 3 , Gerhard Adam 3 , Ulrike Beisiegel 2 , Horst Weller 1
1 Institute of Physical Chemistry, University of Hamburg, Hamburg Germany, 2 IBM II: Molecular Cell Biology, University Medical Center Hamburg-Eppendorf, Hamburg Germany, 3 Department of Diagnostic and Interventional Radiology, University Medical Center Hamburg-Eppendorf, Hamburg Germany
Show AbstractMagnetic Resonance Imaging (MRI) is a sensitive, non-invasive diagnosis technique for the imaging of soft tissues with high resolution and contrast. It is based on the nuclear magnetic resonance (NMR) effect of water protons and their relaxation behaviour within the human body. MR Contrast agents are either applied to shorten the longitudinal T1 relaxation time (positive contrast) or the transversal relaxation times T2 and T2* (negative contrast) and will be increasingly used for targeted imaging in the future. We systematically developed optimized MR contrast agents based on iron oxide nanoparticles for T1, T2 as well as T2* weighted imaging. Sophisticated surface modifications were applied. For instance, the degree of nanoparticle aggregation could be highly controlled, thus allowing either positive or negative image generation. The contrast agents provide optimal physical properties, i.e. very high relaxivity coefficients r1, r2 and r2*. Moreover, they exhibit high stability under physiological conditions, low toxicity and high biological functionality. Particular applications for positive and negative imaging, e.g. the quantification of metabolic processes will be presented.ReferencesU.I. Tromsdorf et al. Nano Letters 2009, DOI: 10.1021/nl902715v.U.I. Tromsdorf et al. Nano Letters 2007, 7, 2422. O.T. Bruns et al. Nature Nanotechnology 2009, 4, 193.
4:15 PM - **PP8.5
Regulation of Cell Responses by Interaction With Their Environments.
Joachim Spatz 1
1 New Materials and Biosystems & Biophysical Chemistry, Max Planck Institute for Metals Research & University of Heidelberg, Stuttgart Germany
Show AbstractEngineering of cellular environments has become a valuable tool for guiding cellular activity such as differentiation, spreading, motility, proliferation or apoptosis which altogether regulates tissue development in a complex manner. The adhesion of cells to its environment is involved in nearly every cellular decision in vivo and in vitro. Its detailed understanding and defined control also opens new strategies for medical technologies with respect to, e.g., stem cell regulation, tissue scaffolds, cell selection due to their disease state, artificial blood vessels, or immunology. Our approach to engineer cellular environments is based on self-organizing spatial positioning of single signaling molecules attached to inorganic or polymeric supports, which offers the highest spatial resolution with respect to the position of single signaling molecules. This approach allows tuning cellular material with respect to its most relevant properties, i.e., viscoelasticity, peptide composition, nanotopography and spatial nanopatterning of signaling molecule. Such materials are defined as “nano-digital materials” since they enable the counting of individual signaling molecules, separated by a biologically inert background. Within these materials, the regulation of cellular responses is based on a biologically inert background which does not trigger any cell activation, which is then patterned with specific signaling molecules such as peptide ligands in well defined nanoscopic geometries. This approach is very powerful, since it enables the testing of cellular responses to individual, specific signaling molecules and their spatial ordering. Detailed consideration is also given to the fact that protein clusters such as those found at focal adhesion sites represent, to a large extent, hierarchically-organized cooperativity among various proteins. Moreover, “nano-digital supports” such as those described herein are clearly capable of involvement in such dynamic cellular processes as protein ordering at the cell’s periphery which in turn leads to programming cell responses.
4:45 PM - PP8.6
Single Protein Nanocapsules and Their Biomedical Applications.
Ming Yan 1 , Juanjuan Du 1 , Zhen Gu 2 , Min Liang 3 , Tatiana Segura 1 , Yi Tang 1 , Yunfeng Lu 1
1 Chemical and Biomolecular Engineering, University of California at Los Angeles, Los Angeles, California, United States, 2 Department of Mechanical and Aerospace Engineering, University of California at Los Angeles, Los Angeles, California, United States, 3 Department of Microbiology, Immunology and Molecular Genetics, University of California at Los Angeles, Los Angeles, California, United States
Show AbstractProtein intracellular delivery has been considered as a powerful and promising route for vaccination, cancer therapy, gene-free reprogramming of stem cells, and treatment of protein-deficient diseases. However, they are still rare seen in clinical applications partially due to low cellular permeability and poor stability against proteases in the cell that digest the protein. Although proteins has been translocated into cells by liposome and cell-penetrating peptides (CPPs), they may be entrapped within the endosomes and degraded in the lysosome rather than be released to the appropriate cellular compartment. Here we present a novel delivery platform based on nanocapsules consisting of only one protein core and a thin permeable polymeric shell that can be engineered to either stable or intracellularly degradable. Non-degradable capsules have long term stability while degradable ones break down their shells and maintain their activity once inside the cells. Multiple proteins can also be delivered to cells with high efficiency, activity and low toxicity for potential applications in imaging, therapy and cosmetics. This work demonstrates transductive single proteins nanocapsules with programmed stability while maintaining their biological functions, a step closer to customized protein therapies.
5:00 PM - PP8.7
Development of a Universal Nanoparticle-based Platform for Targeted Delivery of Multicomponent Cargos to Cancer.
Carlee Ashley 1 , David Padilla 2 , Page Brown 2 , Eric Carnes 1 , Bryce Chackerian 3 , Walker Wharton 3 , David Peabody 3 , C. Jeffrey Brinker 1 3 4
1 Chemical Engineering, University of New Mexico, Albuquerque, New Mexico, United States, 2 Chemistry, University of New Mexico, Albuquerque, New Mexico, United States, 3 Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, New Mexico, United States, 4 Self-Assembled Materials, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractTargeted delivery of imaging and therapeutic agents directly to a cancer cell or tumor faces numerous obstacles that engineered nanoparticles have the potential to overcome. We have developed a silica nanoparticle-supported lipid bilayer (the ‘protocell’) that simultaneously addresses multiple challenges associated with targeted delivery, including specificity, stability, cargo capacity, multicomponent delivery, and immune evasion. The protocell can be easily synthesized with dimensions ranging from 50-150 nm, which prevents clearance by the reticuloendothelial system, while enabling its concentration in solid tumors via the enhanced permeability and retention effect. Like liposomes, protocells can be modified with PEG to extend circulation times and with various ligands to achieve selective targeting. Unlike liposomes, however, the stability of the protocell is independent of lipid charge and degree of saturation, the percentage of cholesterol included in the bilayer, and the type of encapsulated cargo. Furthermore, the nanoporous core of the protocell has a high surface area that increases cargo capacity by 2-3 orders of magnitude over similarly-sized liposomes and enables the development of generic loading strategies applicable to a wide variety of disparate cargo. Using a peptide (SP94, H2N-SFSIILTPILPLGGC-COOH) identified by filamentous phage display to bind to human hepatocarcinoma, we have shown that SP94-modified protocells have sub-nanomolar affinity for Hep3B and HepG2. Impressively, protocells displaying the SP94 peptide have between a 1500-fold and a 4000-fold higher affinity for Hep3B than for human hepatocytes, endothelial cells, and immune cells (peripheral blood mononuclear cells and B- and T-lymphocytes), providing the specificity necessary for efficacious targeted delivery. Upon binding, protocells bearing the SP94 peptide are rapidly endocytosed by Hep3B but show minimal surface binding and absolutely no internalization by hepatocytes. We have loaded protocells with various types of imaging and therapeutic agents, including gold and iron oxide nanoparticles, quantum dots, chemotherapeutic agents, (doxorubicin (DOX), camptothecin, 5-fluorouracil, and cisplatin), protein toxins (A chains of ricin and diphtheria toxins), and cocktails of siRNA that silence expression of cyclin A2, B1, D1, and E1 and have demonstrated that SP94-modified protocells loaded with various therapeutic agents are cytotoxic to hepatocarcinoma but not to any of the control cells in vitro. Protocells deliver a sufficiently high concentration of DOX to decrease the concentration necessary to kill 50% of Hep3B cells (LC50) with induced multiple drug resistance (MDR) from 9.65 μM to 11.5 nM, a 200-fold improvement over ‘gold standard’ liposomal doxorubicin. We propose that protocells can be effectively engineered to possess the properties necessary for their use as universal, targeted carriers of multicomponent mixtures of therapeutic and/or imaging agents.
5:15 PM - PP8.8
Targeted Delivery of Therapeutic Proteins to Mitochondrial, an Approach Based on Single-protein Nanocapsules.
Juanjuan Du 1 , Ming Yan 1 , Zhen Gu 1 2 , Titiana Segura 1 , Yi Tang 1 , Yunfeng Lu 1
1 Department of Chemical and Biomolecular Engineering, UCLA, Los Angeles, California, United States, 2 Department of Mechanical and Aerospace Engineering, UCLA, Los Angeles, California, United States
Show AbstractMitochondria, “the cellular power plants”, are responsible for the production of most ATPs. In addition, mitochondria are also involved in other critical metabolic pathways, including citrate cycle, the oxidation of fatty acids, and the synthesis of steroid hormones and gluconeogenesis. Mitochondrial dysfunction can cause a variety of human diseases, ranging from neurodegerative disease, diabetes, and obesity to ischemia-perfusion injury and cancer. To alleviate diseases involving dysfunctional mitochondrial protein, therapeutic molecules need to be targeted to mitochondria. Compared with small-molecular drugs, which have less defined effect, macromolecular drugs, such as genes or proteins, have well defined therapeutic effect. However, targeted delivery of macromolecules to mitochondria remains challenging. Recently, we developed intracellular protein delivery platform based on single-protein nanocapsules, which had protein-polymer core-shell structure. Net-like polymer shell, which was covalently bonded on the core proteins, served as a protecting layer against various denaturing factors, such as thermal inactivation or proteolysis. This thin polymer layer did not place any obstacles in substrate transportation. In addition, the polymer layer was easily engineered to acquire desired functionalities, such as mitochondrial targeting ability, as illustrated in our research. The nanocapsules can be synthesized by two-step procedure with mild reaction conditions: conjugation with NHS-ester and in-situ polymerization. Mitochondrial targeting moiety can be introduced by involving mitochondrial-targeting monomer in the polymerization step. The resulting nanocapsules had greatly enhanced stability against protease digestion, plasma-membrane permeability, as well as mitochondrial targeting ability. Using superoxide dismutase (SOD) as an example, we also showed retained bioactivity of SOD nanocapsules inside cells. In summary, the single-protein nanocapsules may represent a novel approach as a potential mitochondrial protein therapy.
PP9: Poster Session: Biomaterials/Dynamic
Session Chairs
Phillip Messersmith
Molly Stevens
Friday AM, April 09, 2010
Salon Level (Marriott)
9:00 PM - PP9.1
Selective and Uncoupled Role of Substrate Elasticity in Replication and Transcription Regulation of Epithelial Cell.
Leyla Kocgozlu 1 2 , Dominique Vautier 1 2 , Philippe Lavalle 1 , Henri Tenenbaum 2 1 , Jean-Claude Voegel 1 2 , Pierre Schaaf 3
1 UMR 977 Biomaterials and tissue engineering, INSERM, Strasbourg France, 2 Faculté de Chirurgie Dentaire, University of Strasbourg, Strasbourg France, 3 UPR 22 Institut Charles Sadron, CNRS, Strasbourg France
Show AbstractActin cytoskeleton forms physical connection between ECM, adhesion complexes and nuclear architecture. Because tissue stiffness plays key roles in adhesion (1) and cytoskeletal organization (2), an important open question concerns influence of substrate elasticity onto replication and transcription. To answer this major question, polyelectrolyte multilayer films (3) were used as substrate models with apparent elastic Modulus ranging from 0 to 500 kPa. Sequential relationship between Rac1, vinculin adhesion assembly and replication is becoming efficient at above 200 kPa since activation of Rac1 leads to vinculin, actin fiber formation and subsequently initiation of replication. An optimal window of elasticity (200 kPa) is required for FAK Y397 activation. Transcription, including hnRNP A1 nuclear recruitment, occurred above 50 kPa. Actin fiber and focal adhesion signalling are not required for transcription. Above 50 kPa transcription was correlated with αv-integrins engagement together with histone H3 hyperacetylation and chromatin decondensation allowing little cell spreading. In contrast, soft substrate, below 50 kPa, promoted morphological changes characteristic of apoptosis, including cell rounding, nucleus condensation, loss of focal adhesions and outer cell surface exposed phosphatidyserine. Based on our data, we propose a selective and uncoupled contribution from the substrate elasticity to the regulation of replication and transcription activities for an epithelial cell model (4).
9:00 PM - PP9.10
Biomimetic PEG/RGD Hydrogel for Chondrogenic Differentiation of Human Mesenchymal Stem Cells.
Shaoqiong Liu 1 , Quan Tian 1 , Lei Wang 1 , James Hedrick 3 , Yi yan Yang 2 , Pui Lai Rachel Ee 1
1 Pharmacy, National University of Singapore, Singapore Singapore, 3 , IBM Almaden Research Center, San Jose, California, United States, 2 , Institute of Bioengineering and Nanotechnology, Singapore Singapore
Show AbstractIt has been demonstrated that Poly(ethylene glycol) based photopolymerized hydrogels can be used as scaffolds for chondrogenesis of mesenchymal stem cells. However, photopolymerization often results in materials with poorly controlled structure due to radical chemistry. Additionally, photopolymerization involves toxic initiator and UV light, which may damage the cells. This problem may be overcome by using hydrogels formed via Michael addition reaction that can be conducted under the physiological conditions. Another consideration is that PEG is biochemically inert in nature and lacks the ability to adhere to cells, which is important to maintain cell functions. Extensive efforts have been made to improve the interactions between the cells and PEG hydrogels by making use of cell adhesion peptides such as fibronectin derived RGD peptide and versatile functional PEG macromonomers. Although RGD is commonly acknowledged as a peptide that can enhance hMSC viability, its effect on cell differentiation is not clear. In this study, we have synthesized injectable biodegradable PEG-RGD hybrid hydrogels with tunable gelation properties via Michael addition chemistry. The presence of RGD improved cell viability. We have also demonstrated that hMSCs encapsulated in PEG-RGD hydrogels undergo chondrogenic differentiation in the presence of TGF-β3. More importantly, this effect has been found to be RGD-dose dependent. Our results have revealed that there is an optimal concentration of RGD (1 mM) present in PEG hydrogels, which improves cell viability and promotes chondrogenesis. Therefore, this RGD-containing PEG hydrogel can be a promising scaffold for chondrogenesis of hMSCs.
9:00 PM - PP9.11
Injectable Biodegradable PEG/Collagen Mimetic Peptide Hybrid Hydrogels for Expansion and Delivery of Human Mesenchymal Stem Cells in Cartilage Repair.
Shao Qiong Liu 1 , Quan Tian 1 , James L. Hedrick 2 , Pui Lai Rachel Ee 1 , Yi-Yan Yang 3 1
1 Department of Pharmacy, National University of Singapore, Singapore Singapore, 2 , IBM Almaden Research Center, San Jose, California, United States, 3 , Institute of Bioengineering and Nanotechnology, Singapore Singapore
Show AbstractCartilage defects resulting from injury, wear out, aging and illness can cause osteoarthritis, leading to joint pain. Recently, tissue engineering using a combination of scaffold, cells and signaling molecules has emerged as a promising strategy for cartilage repair because native cartilage tissue lacks the ability for self repair. hMSCs are increasingly considered as an attractive cell source for tissue engineering due to their self-renewal and multilineage differentiation capabilities. Collagen functions as an important component in tissues and associates with cell behaviors, including cell proliferation, cell-cell and cell-ECM communication, and differentiation. However, the use of animal derived collagen scaffold is often restricted because of the potential risk of infectious diseases. In this study, we aimed to synthesize a collagen mimetic peptide and chemically incorporate it into poly(ethylene glycol) (PEG) hydrogel. The PEG/collagen mimetic peptide hybrid hydrogel was used as a scaffold for encapsulation, proliferation and differentiation of human mesenchymal stem cells (hMSCs) into neocartilage/chondrocytes. The collagen mimetic peptide contains a GFOGER sequence flanked by GPO repeats (sequence: (GPO)4GFOGER(GPO)4GCG, CMP), which was synthesized through a Fmoc-based solid phase synthesis approach. The biophysical properties were examined via circular dichroism (CD). Tetra hydroxyl PEG was functionalized with acrylate and then reacted with the peptide. Gelation occurred within thirty minutes with the addition of cells and tetra sulfhydryl PEG via Michael addition. We demonstrated that PEG-CMP hydrogels provide a natural environment, promoting chondrogenesis of hMSCs and enhancing secretion of cartilage specific ECM as compared to hMSCs encapsulated in hydrogels without the peptide. This PEG/CMP hybrid hydrogel can be used as a scaffold to deliver hMSCs for the repair of cartilage defect.
9:00 PM - PP9.12
Epidermal Growth Factor Receptor Targeted Cancer Destruction by Combined Chemotherapeutic and Photothermal Therapy Using Single-walled Carbon Nanotubes.
Hye Kyung Moon 1 , Sang Ho Lee 2 , Hee Cheul Choi 1
1 Dept. of Chemistry, Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang Korea (the Republic of), 2 Department of Surgery, Kosin University College of Medicine, Busan Korea (the Republic of)
Show AbstractSelective targeting is one of the key requirements to overcome current challenges associated with effective cancer treatment and drug delivery. Recently, nanomedicine has been highly focused since it may play a pivotal role in cancer therapeutics by utilizing the improved electrical, optical, and magnetic properties of biocompatible nanomaterials, which could improve specific targeting to the cancer cells, and eventually increase the effectiveness of cancer therapeutics. We have developed single-walled carbon nanotube (SWNT)-based molecular platform as a cancer targeted therapeutic agentusing. Unique physicochemical properties and good biocompatibility properties of SWNT provide a great opportunity to serve as a good nanoscale vehicle for therapeutic purpose. For the selective targeting and destruction of cancer cells, we have functionalized SWNT with cetuximab as a targeting moiety, lapatinib as a anti-cancer drug, and Cy5.5 as a imaging agent. The Cy5.5-Cetuximab-SWNT conjugate has been synthesized by EDC/NHS coupling chemistry, and characterized by colorimetric, microscopic and spectroscopic method. The specific reactivity to epidermal growth factor receptor (EGFR) of this conjugate has been evaluated by flow cytometry and fluorescence microscopy. In vitro cytotoxicity efficiency of this conjugate has been achieved in combination with noninvasive exposure of near infrared light (NIR). The cellular incubation of this conjugate has shown very high affinity to EGFR positive cancer cell and significant inhibition of cell proliferation as well. This result implies that our SWNTconjugate system provides a powerful approach for selective therapeutic treatment of various type of EGFR overexp
9:00 PM - PP9.13
Organic Thin Film Transistors Fabricated on Resorbable Biomaterial Substrates.
Christopher Bettinger 1 , Zhenan Bao 1
1 Chemical Engineering, Stanford University, Stanford, California, United States
Show AbstractMicroelectronic systems utilizing organic materials afford many advantages over traditional silicon-based systems including the possibility of fabrication on polymeric substrates, which are suitable for a broad range of flexible electronics applications including conformal devices and displays. Recent concomitant advancements in organic electronics and biodegradable polymers processing suggest that there is the potential for the use of biodegradable polymeric systems for the development of biodegradable electronic devices for potential use in biomedical or environmental applications. We investigated the use of poly(L-lactide-co-glycolide) (PLGA) as a potential substrate material platform for organic electronic devices. We fabricated organic thin film transistors in top contact configuration using PLGA as the substrate, which composed 99.89% of the final device by mass. We used evaporated silver as the gate electrode, spin coated poly(vinyl alcohol) as the gate dielectric, evaporated 5,5′-bis-(7-dodecyl-9H-fluoren-2-yl)-2,2′-bithiophene (DDFTTF), a water stable p-channel semiconductor, as the active layer, and evaporated gold patterned using a shadow mask as the source-drain electrodes. Transistors fabricated in this manner exhibited average mobilities of approximately 0.21 cm^2-sec^(-1)-V^(-1) and Ion/Ioff up to 5.5x10^3 with threshold voltages of approximately -15.4 V. These structures performed stably under water, but failed upon exposure to phosphate buffered saline. Device degradation was simulated by submerging the device in citrate buffer at 37 degrees Celsius. Mass loss degradation kinetics showed that these devices underwent 50% mass loss at 8 weeks and near complete resorption at 10 weeks. The device functionality presented in this work is the first step towards realizing more complex biodegradable and compostable electronic devices. Subsequent design, fabrication, and integration of other simple electronic components fabricated from resorbable electronically active materials could be used in the realization of temporary electronic devices such as resorbable biomedical implants.
9:00 PM - PP9.14
Boundary Lubricant - Functionalized PVA Gels for Biotribological Applications.
Michelle Michalenko 1 , Timothy Ovaert 1
1 , University of Notre Dame, Notre Dame, Indiana, United States
Show AbstractPolymer gels are a promising option for use as an articulating cartilage substitute due to their viscoelastic mechanical response and good compressive properties. Considerable effort has gone into mechanical strengthening of hydrogels, but in order for a biomimetic material to be viable as a cartilage substitute it must also exhibit low friction, which will lead to higher wear resistance. To achieve low friction, it is necessary to significantly improve the boundary lubrication properties. The objective of this study was to functionalize polyvinyl alcohol (PVA) with carboxylic acid molecules, to fabricate biomimetic hydrogels, and to investigate the alteration of tribological and mechanical properties as compared to standard PVA material. PVA with an average molecular weight of 166,000 g/mol was functionalized with dodecanoic acid (C12) through a nucleophilic acyl substitution reaction. Varying molar concentrations of 1:1, 2:1, and 5:1 ratio PVA:C12 powders were produced. Verification of the reaction was performed via Fourier Transform Infrared Spectroscopy (FTIR). Mechanical and tribological testing was performed on standard and functionalized hydrogels fabricated via freezing and thawing methods. Tribological characterization was performed by nanofriction testing under boundary lubrication conditions using a Triboindenter™ (Hysitron, Minneapolis, MN). A 100um diameter diamond spherical tip was used as the sliding asperity. Constant normal loads N1 = 300 uN and N2 = 500 uN were applied at a constant sliding speed of 333 nm/s, and a contact length of 10 microns. Comparison of the coefficient of friction (μ) between gel batches reveals that increasing the concentration of dodecanoic acid leads to a decrease in μ observed during sliding. Standard PVA surfaces maintained reasonable values of μ = 0.16 ± 0.09 for N1 and μ = 0.15 ± 0.06 for N2 while gels with ratio PVA:C12 of 1:1 saw a decrease in μ = 0.05 ± 0.02 for N1 and μ = 0.049 ± 0.01 for N2. Mechanical characterization of the gels was performed via nanoindentation. The elastic modulus (E) of the fabricated gels was calculated using the Oliver-Pharr method with a 1 mm diameter flat cylindrical indenter with an applied load of 100uN. An examination of the influence of load revealed that an increase in the molar concentration of dodecanoic acid leads to a slight decrease in elastic modulus. Standard PVA gels exhibited E = 296.83 ± 72 kPa, while the gels with the highest carboxlic acid concentration (PVA:C12 1:1) were measured with E = 215.21 ± 30 kPa. This occurred because an increase in the concentration of functionalized bonds may hinder the polymer’s ability to crosslink due to the opposite charge nature of the PVA and dodecanoic acid.
9:00 PM - PP9.15
Double-sided, Nanotopographic, Biodegradable Polymer Films for Tissue Engineering Applications.
Anna Kobb 1 4 , Lichong Xu 1 , Logan Osgood-Jacobs 3 5 , Henry Donahue 3 2 , Christopher Siedlecki 1 2
1 Surgery, Penn State University, Hershey, Pennsylvania, United States, 4 Bioengineering, Penn State University, University Park, Pennsylvania, United States, 3 Orthopaedics and Rehabilitation, Penn State University, Hershey, Pennsylvania, United States, 5 , Swarthmore College, University Park, Pennsylvania, United States, 2 Bioengineering, Penn State University, Hershey, Pennsylvania, United States
Show AbstractNanometer-sized topographies have been shown to stimulate cells and proven to be useful in supporting cell growth for regenerative medicine and tissue engineering. However, most methods utilize technologies that modify only 1 side of a planar substrate, or require highly expensive and complicated methods that are not always easily available. In this work, we utilized a well-known phase-separation/spin coating technique that creates nanometer-scale pillars with heights of 10-12nm. These structures have been shown to influence the cellular response to polymer surfaces and leads to increased proliferation of cells such as feotal osteoblasts. We then adapted a sandwich replication technique to modify both sides of a degradable polymer scaffold. A polystyrene/poly(bromostyrene) (PS/PBrS) solution was spin-coated onto a glass cover slip, with phase segregation resulting in the formation of nanoscale islands on this film. The topography was transferred to PDMS films using replication molding techniques. Poly(L-lactic acid) and poly-l-lactide/glycolide were sandwiched between two of these PDMS negatives to form a double-sided nanotopographic film. Atomic force microscopy (AFM) analysis of these materials showed that the nanotopographies were faithfully reproduced in the degradable polymers. XPS analysis showed a small transfer of silicone to the degradable films, consistent with our previous results using PLLA and PLGA in chloroform. SEM characterization showed large scale consistency in the topographies. These films were subsequently sliced into ~500 micron strips, and at a thickness of 50 microns this results in greater than 90% of the film being covered by the nanotopography. The thin strips of polymer were packed into a short length of silicone tubing, and tested for their ability to support human Foetal Osteoblast (hFOB) cell adhesion in a perfusion chamber under oscillating fluid flow. Preliminary results suggest that hFOB cells adhere to both sides of the strips, with the topographically-modified films showing increased cell adhesion compared to smooth controls.
9:00 PM - PP9.16
Engineering Blue Light Curable Hydrogel Bioreactors for Cell Immobilization: Evaluating Cell Physiology.
Swati Mishra 1 , Paul Calvert 1
1 , University of Massachusetts Dartmouth, North Dartmouth, Massachusetts, United States
Show AbstractIn tissue engineering, it is highly recommended that seeded cells should be protected from sudden changes in external environmental conditions as well as from contamination during their growth and development phase. Moreover, cells should be provided with sufficient and continuous supply of nutrient and oxygen while they are growing and developing into a more organized tissue structure. Previously reported cell immobilization techniques incorporated toxic solvents and harsh processing conditions which limited their application for cell implantation and reduced effective cell loading after curing. Furthermore, cell immobilized constructs showed weak mechanical strength and failed to overcome mass transfer resistance imposed by carrier material. We propose a novel approach of immobilizing live cells in biocompatible hydrogels for cell implantation. We are aiming to develop hydrogel system with elastic properties that could mimic the spongy (soft and wet) morphology of tissues of avascular marine organisms (Specifically Cnidarians including sea anemones). As in avascular marine invertebrates diffusion of nutrients takes place by the fluid movement generated with the help of pulsatile contractions of the various cell layers to serve the transportation of nutrient and waste, similarly elastomeric nature of the hydrogel would facilitate the diffusion of nutrients to the immobilized cells on the application of pulsatile pressure. A Rapid prototyping (RP) technique was employed for the layer by layer deposition of cell loaded prepolymer gels, until it formed 3D construct with interconnected network of microfluidic channels. Cell friendly blue light curing was used to crosslink water-soluble monomers into cell immobilized hydrogels in order to improve the performance of functional bioreactor. This technique allows efficient and continuous supply of growth medium and dissolved oxygen to immobilized cells; it also protects them from undesirable environmental conditions and contamination caused by other micro organisms. Results of cell viability assay confirmed the non cytotoxic nature of blue light and prepolymer formulations before and after curing. Growth kinetics of entrapped cells and its dependence on degree of cross-linking were investigated, using optical and confocal microscopy. Cell immobilized constructs showed good cell storage capacity when stored at refrigerated conditions for extended time scale and good structural integrity in physiological buffer. Morphology of cell immobilized hydrogels was studied using scanning electron microscopy. Bioreactor was evaluated for its application to study various intracellular and extracellular activities.
9:00 PM - PP9.17
Investigation of Cell Growth on in-situ Alloyed Biocompatible Thin Film Media.
Hariti Yoshmetha 1 , Anan Srikiatkhachorn 2 , Nipan Israsena 3 , Min Medhisuwakul 4 , Nirun Witit-anun 5 , Saknan Bongsebandhu-phubhakdi 2 , Boonrat Lohwongwatana 1 6
1 Nanoengineering program, International School of Engineering, Chulalongkorn University, Bangkok Thailand, 2 Department of Physiology, Faculty of Medicine, Chulalongkorn University, Bangkok Thailand, 3 Department of Pharmacology, Faculty of Medicine, Chulalongkorn University, Bangkok Thailand, 4 Plasma & Beam Physics Research Facility, Department of Physics, Faculty of Science, Chiang Mai University, Chiang Mai Thailand, 5 Vacuum Technology and Thin Films Research Laboratory, Burapha University, Chonburi Thailand, 6 Department of Metallurgical Engineering, Chulalongkorn University, Bangkok Thailand
Show AbstractAdvanced metals and alloys are often used in medical tools and apparatus because of their high strength and corrosion resistance. However, many alloying elements, such as nickel, are known to cause allergy which is triggered by heavy metal release when they are exposed to biological and human fluids. This study aims to develop biocompatible thin film media based on in-situ synthesis of metal alloys. The bio-media will be tested for possible allergic reactions using different techniques such as chloride-ion solution release test, on-media cell growth effects, etc. The cell growth test use various cell lines including 3T3 mouse embryonic cells, normal basic cells, and Neuro2A cells, which are specific neuron cells. Alloys of different compositions will be synthesized by depositing each alloying species separately using magnetron sputtering technique and cathode arc vapor deposition technique. Various alloy families are deposited on the media and the compositional change is designed to correspond with variation in distances between the substrate and the two targets. Testing can be done faster and easier on several alloy compositions which could be intermetallic compounds, solid solutions, etc. Alloys of interest include the Ni-Ti system which allows the characterization of nitinol, shape memory alloy used as stents, and Cu-Zr system which is famous for its glass forming abilities in many specific compositions. Several operating conditions for thin film growth must be investigated and optimized for complete in-situ alloying. Assorted characterization techniques will be used to identify the compositions and the resulting microstructure of different alloy systems. The medias are then tested for cell proliferations and growth using different cell lines mentioned above. Objectives:1)To synthesize the biocompatible thin film media which can be apply to cell culture substrate.2)To provide appropriate and effective sputtered thin film for medical apparatus.3)To test the safety of novel thin film by a cell growth rate in biological conditionOutcomes:1)The method that can detect an allergenic potency by cell culture system.2)The novel in-situ alloyed biocompatible thin film media that can be applied in medical apparatus.
9:00 PM - PP9.18
Superhydrophobic Plasma Treated Polyurethane Membranes for Biomedical Applications.
Adriana Carvalo Natal de Moraes 1 , Daniel Baptista 1 , Cecilia Vilani 1 , Marcelo Maia da Costa 2 , Manoel Pires 1 , Lidia Sena 1
1 Divisão de Materiais, INMETRO, Xerém - Duque de Caxias, RJ, Brazil, 2 Departamento de Física, PUC-RIO, Rio de Janeiro, RJ, Brazil
Show AbstractPolyurethanes (PUs) have been attracting much interest due to their use as biomaterial for several medical devices. Furthermore, the possibility of modifying the surface properties through hydrophilic/hydrophobic balance as well as by biologically active species such anticoagulants or biorecognizable groups opens up the possibility of exploiting these materials in dynamic biomedical applications, such as Guide Tissue Regeneration. In this contribution, a detailed investigation of the surface properties of plasma-functionalized PU membranes and its behavior concerning cell-material interaction is presented.We report on the synthesis of super hydrophobic PU membranes treated by CF4 plasma. The PU membranes were prepared from a 15% solution of PU in Tetrahydrofuran (THF). Transparent, cloudy and white non-transparent membranes were produced via direct drying (transparent) or phase inversion method by immersion precipitation process using nonsolvents. The PU membranes were then subjected to a CF4 plasma for 10 min. It was used 4 sccm of CF4 and a self-bias voltage of -190 V, controlled by a low input power of ~4W. The chemical structure of the bulk and surface material was characterized by attenuated total reflection Fourier transform infrared spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS), respectively. The wettability of the PU surfaces was investigated through contact angle measurements. The surface roughness was monitored by atomic force microscopy (AFM). The results show a high improvement in the hydrophobicity of all PU membranes, reaching contact angle values of 130 degrees for the cloudy one. When compared with the transparent PU membrane, the cloudy and nontransparent ones presented both higher contact angle and RMS roughness, before and after the plasma treatment. The content of fluorine species attached to the surface after plasma treatment was analyzed through the C1s XPS spectrum. A theoretical model describing the role of the roughness and the functionalized surface on the wettability of the PU membranes is shown. Finally, an evaluation of cell culture on the treated PU membranes is presented.
9:00 PM - PP9.20
Porous Silicon Cytoadhesive Microparticles for Oral Drug Delivery.
Rachel Lowe 1 , Kristy Ainslie 2 , Tejal Desai 1
1 Bioengineering and Therapeutic Sciences, University of California-San Francisco, San Francisco, California, United States, 2 Division of Pharmaceutics, The Ohio State University, Columbus, Ohio, United States
Show AbstractMicrofabricated porous nanostructures are increasingly being developed and applied to new and existing biomedical therapies. In this work, we demonstrate the feasibility of porous silicon cytoadhesive microparticles as an oral delivery platform to administer small molecules via the gastrointestinal tract. To achieve, drug delivery a number of obstacles need to be overcome such as low drug permeability through the gastrointestinal epithelium and limited drug retention at the epithelial interface. The multi-dimensional tuning capabilities of porous silicon, where pore geometry and morphology are strongly dependent on silicon substrate characteristics and fabrication conditions, allows the fabrication of a highly engineered porous microparticle for drug delivery. Also, porous silicon offers a large surface area, increasing the materials loading capacity and surface sites available for surface functionalization, enables numerous binding entities to be incorporated in the microparticle of binding entities. We report the fabrication of defined porous silicon microparticles using microfabrication and electrochemical processes. These particles were then loaded with drug and functionalized for cytoadhesive attachment to in vitro caco-2 monolayers. The residence time and drug release over time is investigated in a novel diffusion flow chamber that allows the simultaneous study of microparticle binding and small molecule release under physiologically relevant flow conditions. We believe, that porous silicon cytoadhesive microparticles are a promising approach to achieve sustainable and controlled drug release via the gastrointestinal tract.
9:00 PM - PP9.21
Biomimetic Endothelial Glycocalyx via Dextran Photo-patterning.
M. Carme Coll Ferrer 1 , David Eckmann 2 , Russell Composto 3
1 Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 3 Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractImproved biocompatible materials may result from mimicking biology. For vascular applications, this includes the endothelial glycocalyx, a complex polysaccharide-based network that protects blood vessels from pathologic insults involving cell and protein adhesion. We utilized dextran photo-patterning in the production of a model biomimetic endothelial glycocalyx. Dextran was photo-activated by an esterification reaction with 4-azidobenzoic acid and characterized by UV, FT-IR and 1H-NMR. Dextrans having an azide content of 22, 3.2, 1.2 and 0.3 wt. % were synthesized. Low azidated dextran (1.2 wt. % azide content) was successfully grafted onto polystyrene (PS) and polyurethane (PU) surfaces, which were characterized using ellipsometry, contact angle and AFM. Dextranized surfaces were 11±3 nm thick and highly hydrophilic (contact angle <10°). Surfaces were overall smooth (RMS=1.3±2.63 nm) but included aggregates, which were observed to swell and turn into a more extended and homogeneous layer by wet AFM. Additionally, low azidated dextran was effectively photo-patterned on PS and PU surfaces and characterized by optical microscopy and AFM. Selective adsorption of FITC-labeled human serum albumin was limited to the non-dextranized areas of both PU and PS patterned surfaces, as observed by fluorescence microscopy.Supported by NIH grants R01 HL060230 and T32 HL007954
9:00 PM - PP9.22
Development of Novel Bone Tissue Engineering Materials Using Genetically Engineered Phage.
So Young Yoo 1 , Masae Kobayashi 1 , Seung-Wuk Lee 1
1 Bioengineering, UC Berkeley, Berkeley, California, United States
Show AbstractWe developed novel bone tissue engineering materials using genetically engineered phage modified with collagen type I motif, Asp-Gly-Glu-Ala (DGEA) peptide. In bone tissue, the adhesion of osteoblasts to bone extracellular matrix (ECM) can modulate diverse physiological aspects such as growth, differentiation and mineralization. The attachment and spreading of preosteoblast cells to ECM are dependent on the interaction between various cellular adhesion molecules and their consensus sequences present in ECM proteins. Previously, DGEA peptides have been known to be effective to stimulate the preosteoblast cells to regulate bone cell growth processes. M13 phage was genetically engineered to display high density of DGEA signal motif on their major coat proteins and constructed for two- and three-dimensional tissue scaffold nanostructures. The preosteoblastic cellular responses to the DGEA motif matrices made by M13 phage was investigated using MC3T3 E1 cells. Cell proliferation assays on two-dimensional surfaces of DGEA modified phages showed that the cells proliferated well on these phage matrices. Cells on three-dimensional DGEA-M13 phage matrices also exhibited normal morphology, whereas MC3T3 E1 cells showed different morphology on three dimensional control M13 phage (wildtype-phage with no insert peptide) matrices. The cellular surface areas cultured on DGEA-phage matrices was wider than those on the control M13 phages. DGEA motif on major coat proteins of the M13 were effective to stimulate the preobsteoblast cell growth and exhibited significant proliferation and differentiation effects of the cells to induce the formation the minerals in three-dimensional cultures than those of control.
9:00 PM - PP9.23
Design and Preparation of Metal-Adeninate Porous Materials for Environmental and Biomedical Applications.
Nathaniel Rosi 1 , Ji-Hyun An 1
1 Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show AbstractThe design, synthesis, and characterization of crystalline discrete and polymeric metal-adeninate porous materials will be presented. Specifically, the coordination chemistry of adeninate will be discussed and methods of controlling this coordination chemistry will be presented in order to target and access particular porous materials. Particular attention will be dedicated to describing how the structures and properties of these materials can be carefully tailored for drug storage and release and carbon dioxide capture and separation.
9:00 PM - PP9.24
Cardiomyocyte Activity Modulated via Microfabricated Scaffolds and Devices.
Robert Tucker 1 , Perla Ayala 1 , Tejal Desai 1
1 , University of California San Francisco - Mission Bay Campus, San Francisco, California, United States
Show AbstractIrreversible damage to contractile myocytes results in poor cardiac pumping and affects five million heart failure patients in the US. Subsequent to a myocardial infarction, fibroblasts initiate wound healing, resulting in the production of scar tissue. This scarring decreases the local elasticity of the cardiac tissue and the overall efficacy of the heart function. Decreasing or eliminating the scar tissue formation dramatically reduces the adverse impacts of a myocardial infarction. We recently showed fibroblast proliferation could be modulated via microtopographical structures (microrods) on planar polymer surfaces. Further work has shown microrods suspended within Matrigel create a three dimensional scaffold with microscale cues, limiting fibroblast proliferation and down-regulating the gene-expression of several extra-cellular proteins. Microrod physical and chemical properties can be tuned to produce a controlled response within the three dimensional scaffold.The effect of altering the physical and chemical characteristics of the microrods and their concentrations within the three dimensional scaffold were investigated. Here we show that temporal and spatial regulation of mechanical and chemical cues can be used to control the physiological response of cells within an engineered scaffold.
9:00 PM - PP9.25
Contractile C2C12 Myotubes Micropatterns Embedded in a Fibrin Gel.
Kuniaki Nagamine 1 3 , Takeaki Kawashima 1 , Takeshi Ishibashi 1 , Hirokazu Kaji 1 3 , Makoto Kanzaki 2 3 , Matsuhiko Nishizawa 1 3
1 Department of Bioengineering and Robotics, Graduate School of Engineering, Tohoku University, Sendai Japan, 3 , Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kawaguchi Japan, 2 Department of Biomedical Engineering, Graduate School of Biomedical Engineering, Tohoku University, Sendai Japan
Show Abstract In vitro bioassay systems that incorporate physiologically active cells have been developed to investigate biological processes as an alternative method of whole animal experiments. Specifically, a system incorporating skeletal muscle cells is required to characterize the molecular mechanisms involved in glucose homeostasis and insulin- and contraction-mediated glucose uptake and metabolism. Such a bioassay system could be used to reveal the complex mechanisms involved in the development and maintenance of type2 diabetes because type2 diabetes is closely associated with defection of glucose uptake in skeletal muscle cells. Besides, screening of candidate drugs against type2 diabetes could be also achieved using this system. In this study, we have developed the contractile C2C12 myotube line patterns embedded in a fibrin gel to afford a physiologically relevant and stable bioassay system. The C2C12 myotube/fibrin gel system was prepared by transferring line-patterned myotubes monolayer from a glass substrate to a fibrin gel while retaining their original patterns of myotubes. The myotube line patterns on the glass substrate were prepared by being confined within a rectangular (250 micro meter width) glass surface owing to surrounding regions of the cell-resistive 2-methacryloyloxyethyl phosphorylcholine polymer. To endow the myotubes in the gel with contractile activity, a series of electrical pulses (amplitude, 0.7 V mm-1; duration, 2.0 ms; frequency, 1.0 Hz) were applied overnight through a pair of carbon electrodes placed at either side of a fibrin gel separately. The overnight stimulation caused sarcomere assembly and contraction when the myotubes were subsequently electrically stimulated. The frequency and magnitude of myotubes contraction were functions of the pulse frequency and duration, respectively. The patterned C2C12 myotubes, supported by the elastic fibrin gel showed a 2.8-fold larger contractile displacement than did a myotube monolayer that was attached on a conventional culture dish. The myotubes/fibrin gel system also maintained their line pattern and contractile activity for a longer period of time (one week) than did the myotubes of the dish system, while the displacements increased 3.3-fold during that time period. Therefore, the myotube/fibrin gel system would be better suited, than did a dish-based system, to monitor glucose uptake and metabolism mediated by insulin or contraction over a period of days.
9:00 PM - PP9.26
Responsive Microcontainers Based on Hydrogen-bonded Multilayers of Tannic Acid.
Veronika Kozlovskaya 1 , Eugenia Kharlampieva 1 , Irina Drachuk 1 , Vladimir Tsukruk 1 2
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractWe explored responsive properties of hollow multilayer shells of tannic acid (TA) assembled with a neutral polymer, poly(N-vinylpyrrolidone) (PVPON), poly(N-vinylcaprolactam (PVCL) or poly(N-isopropylacrylamide) (PNIPAM), through hydrogen-bonding layer-by-layer (LbL) assembly. We found that bilayer thickness, nanoshell porosity and the elasticity of the membranes can be tuned by a combination of a molecular weight of the neutral polymer, by the strength of its association with tannic acid, and by a change in counterpart hydrophobicity. Unlike most hydrogen-bonded LbL films, the produced tannic acid-based multilayer shells were stable in the pH range from 2 to 10 and showed reversible pH-triggered changes in surface charge and permeability of the shells towards FITC-labeled polysaccharide molecules. We demonstrate that permeability of the TA-based containers can be switched between minimal to maximal by changing pH from 9 to 6, respectively, providing new opportunities for loading and release of a functional cargo. We also demonstrate that gold nanoparticles can be grown within tannic acid-based shell walls under mild environmental conditions paving the way for further modification of the capsule walls through thiol-based surface chemistry.
9:00 PM - PP9.27
On-demand Release of Cells and Hydrogel Constructs from ITO Surfaces.
Sunny Shah 1 , Mihye Kim 2 , Ji Youn Lee 1 , Giyoong Tae 2 , Alexander Revzin 1
1 Biomedical Engineering, University of California, Davis, Davis, California, United States, 2 Materials Science and Engineering, Gwangju Institute of Science and Technology, Buk-gu, Gwangju, Korea (the Republic of)
Show AbstractDeriving new sources of hepatocytes is critical for further advancement of liver-directed cell therapies and tissue engineering applications. The goal of this study was to develop a switchable surface that would allow collection of a specific cell type from micropatterned co-cultures. In this study, we micropatterned heparin-based hydrogels on glass substrates using UV photopolymerization. We showed patterning of stem cells, primary hepatocytes and fibroblasts inside and around micropatterned heparin-based hydrogels. To test the bioactivity of heparin hydrogel, we incorporated hepatocyte growth factor (HGF) in heparin hydrogel and PEG hydrogel and studied its release kinetics. Results showed long-term sustained release of HGF from heparin-based hydrogel. In addition, immunostaining showed greater albumin production by primary hepatocytes patterned adjacent to heparin hydrogel compared to cells patterned around PEG hydrogel. Finally, we incorporated fibroblasts into heparin-based hydrogels and patterned the cell-containing hydrogels on a conductive indium tin oxide (ITO) substrate. Heparin hydrogel structures were registered with individually addressable ITO electrodes and anchored to the surface via an acrylated silane layer. Importantly, applying reductive potential (-1.8V for 60 sec) to the desired electrode resulted in desorption of the silane coupling layer and detachment of the cell-containing hydrogels. The use of an array of individually addressable ITO electrodes permitted temporal control in detachment and collection of cell-containing constructs. Viability assays revealed that greater than 80% of cells were viable after the electrochemical desorption process. We also demonstrated release of micropatterned heparin-based hydrogels from ITO substrates. The novel electroactive biointerface described here will enable sampling and harvesting of cells residing on micropatterned surfaces.
9:00 PM - PP9.28
pH-responsive Nanogated Ensemble based on Gold-capped Mesoporous Silica through Acid-labile Acetal Linker.
Rui Liu 1 , Xiang Zhao 1 , Pingyun Feng 1
1 Chemistry, University of California, Riverside, Riverside, California, United States
Show AbstractA new pH-responsive hybrid nanogated ensemble has been developed by using acetal group linked gold nanoparticle capped mesoporous silica. The hydrolysis of acetal linker at acidic environment makes the gold nanoparticles work as gatekeeper to control the release of guest molecules from mesoporous silica under different pHs.
9:00 PM - PP9.29
Electronic Surface Switches Based on Conductive Polymers to Control and Regulate Cell Systems.
Kristin Persson 1 , Roger Karlsson 2 , Karl Svennersten 3 , Edwin Jager 1 , Agneta Richter-Dahlfors 3 , Peter Konradsson 2 , Magnus Berggren 1
1 Department of Science and Technology, Linköpings universitet, Norrköping Sweden, 2 Department of Physics, Chemistry and Biology, Linköpings universitet, Linköping Sweden, 3 Department of Neuroscience, Karolinska institutet, Stockholm Sweden
Show AbstractMany different types of cells adhere to solid surfaces while in culture, and it is therefore of great interest to be able to control and regulate among other things the adhesion, spreading and proliferation of cells by means of the surface they are attached to. Here we report electronic surface switches based on the conductive polymer poly(3,4-ethylenedioxythiophene), PEDOT. The polymer in question has been used in a number of applications involving cells and is known for its biocompatibility as well as for its electronic and ionic conductivity. We have previously reported electronic surface switches based on PEDOT for control of cell adhesion and proliferation (K. Svennersten et. al., Biomaterials 2009, 30), and have subsequently moved on towards more integrated cell culture systems. Our ultimate goal is being able to regulate and control all events during cell growth; adhesion, spreading, proliferation, differentiation and release of cell systems using conductive polymers. Thin films of PEDOT derivatives have been deposited by various means on surfaces dedicated for cell growth, and employed as electrodes during the cell culture period. We found that the voltage bias that was applied to the surface switches can dictate several of the key dynamic properties of the cells life cycle stages. These findings may blaze the trail for a future electronic Petri-dish or well-plate technology, possible to apply in numerous cell biology and diagnostics experiments and applications.
9:00 PM - PP9.3
Electrochemical Detection of Vascular Endothelial Growth Factors (VEGFs) Using VEGF Antibody Fragments-modified Au NPs/ITO Electrode.
Gang-Il Kim 1 , Kyung-Woo Kim 2 , Min-Kyu Oh 2 , Yun-Mo Sung 1
1 Materials Sci. & Eng., Korea University, Seoul Korea (the Republic of), 2 Chemical & Biological Eng., Korea University, Seoul Korea (the Republic of)
Show AbstractA new electrochemical technique for the detection of vascular endothelial growth factors (VEGFs) as a cancer-related biomarker is presented in this paper. Gold nanoparticles (Au NPs) were self-assembled onto an indium tin oxide (ITO) electrode to prepare a modified sandwich type electrochemical immunoassay platform. VEGF antibodies were cleaved into two half-fragments by 2-mercaptoethylamine-HCl (2-MEA) and the fragments were immobilized onto the Au NP substrates by their thiol groups. Through this strategy, randomly oriented attachment of antibodies was prevented which frequently occurs in a general use of whole antibody and reduces the number of available sites for the attachment of target molecules. VEGF target molecules were applied to the immunoelectrodes and they combined with the antibody fragments attached to the Au NP electrode. Then, ferrocene-tagged antibodies, which release electrons under a proper applied potential, were added to the system and they combined with the VEGF molecules pre-attached to the antibody fragments. The increase in the current from the differential pulse voltammetry (DPV) measurements is proportional to the number of ferrocene molecules which is in turn proportional to the concentration of VEGF target molecules. Using this modified sandwich immunoassay with the Au NP/ITO electrode, VEGFs as low as 100 pg/ml were detected with high specificity.
9:00 PM - PP9.30
Light Activated Immobilization of Dye-labeled Biomolecules on Polymer Substrates.
Anup Sharma 1 , Aschalew Kassu 1 , Jean-Michel Taguenang 1 , Redahegn Sileshi 1
1 Physics, Alabama A&M University, Normal, Alabama, United States
Show AbstractNBD (azo-dye)-labeled biomolecules in aqueous medium can be immobilized on a polybutadiene substrate when exposed to a low power (few milli-watt) 488 nm laser. This light-activated immobilization has been observed for phospholipids as well as a protein (avidin) labeled with NBD dye. The technique has been used to attach these biomolecules to polybutadiene substrate in a micro-array pattern using lithographic masks. This pattern is an exact replica of the light intensity distribution on substrate and so the technique can be used for holographic recording as well as for biomolecular applications. Attachment of biomolecules to the substrate in a grating pattern has also been accomplished using mask-less interferometric lithography in aqueous phase using 488 nm laser. By monitoring the growth-rate of bio-molecular gratings with diffraction of a weak He-Ne laser, it is seen that surface immobilization is saturated in a time of few minutes. Immobilized biomolecules are stable over a period of several days and so the laser-excited dye appears to result in a covalent bond with the polymer substrate. Polybutadiene substrate is synthetic rubber and biologically benign, making it attractive as a platform for biomolecular applications.
9:00 PM - PP9.31
Shape Memory DNA Hydrogel by Highly Entangled Network.
Jong Bum Lee 1 , Hisakage Funabash 1 , Young Hoon Roh 1 , Nokyoung Park 1 , Dan Luo 1
1 Biological Engineering, Cornell University, Ithaca, New York, United States
Show AbstractA remarkable hydrogel made entirely from entangled DNA strands was successfully synthesized. The gelling process was based on the physical interactions of long DNA strands as opposed to base pairing. This biocompatible and biodegradable DNA hydrogel behaved fluid-like outside water but remembered the permanent shape and maintained gel properties upon introduction of water. Due to its fluid-like property, the DNA hydrogel was easily transformed between different shapes depending on the mold. In addition, the hydrogels exhibited thermoplastic behavior, being able to take on a new permanent shape upon heating in a mold. Inspired by these characteristics of this shape memory DNA hydrogel, we have developed an injectable extracellular matrix for tissue engineering.
9:00 PM - PP9.32
Biomimetic Metallic Electrodes for Intracellular Electrical Measurements.
Piyush Verma 1 , Wei Cai 2 , Nick Melosh 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 Mechanical Engineering, Stanford University, Stanford, California, United States
Show AbstractElectrical interfaces represent a powerful approach for interrogating or perturbing biological systems, with applications in neural prostheses, the regulation of artificial neuronal networks and arrayed patch clamp diagnostics. A key step towards achieving this interface is the development of inorganic nanostructures that can specifically and non-destructively incorporate into biological membranes. Here, we report the development of nanoscale metallic posts that mimic transmembrane proteins, allowing their spontaneous insertion into lipid membranes. These electrode posts were formed by metal evaporation with a nanoscale gold band that can be functionalized with alkanethiols to be hydrophobic. We describe nanoscale electrical measurements with these post-electrodes on cells and demonstrate Giga-ohm seal formation at the electrode-membrane interface. Moreover, we use coarse-grained molecular dynamics simulations to elucidate the structure of the electrode-membrane interface.
9:00 PM - PP9.33
Functional Cyclic Carbonates for Thermoresponsive, Biodegradable Block Copolymer Nanocarriers.
James Hedrick 1 , Kazuki Fukushima 1 , Sung Ho Kim 1 , Jeremy P. K. Tan 2 , Yiyan Yang 2 , Robert Waymouth 3
1 , IBM Research, San Jose, California, United States, 2 , 3Institute of Bioengineering and Nanotechnology, Singapore Singapore, 3 , Stanford University, Stanford, California, United States
Show AbstractWater-soluble, thermoresponsive block copolymers based on a biodegradable platform were synthesized by the ring opening polymerization of cyclic carbonate monomers functionalized with hydrophilic or hydrophobic groups for application as nanocarriers in medicine. The approach based on cyclic carbonate monomers derived from a biocompatible precursor, 2,2-bis(methylol)propionic acid (bis-MPA), that allow a simple and versatile approach to functional monomers capable of undergoing ring opening polymerization (ROP). The resulting polymers have predictable molecular weights based on the molar ratio between monomers to initiators and the narrow molecular weight distributions. Transmittance measurement for aqueous polymers solutions showed evidence for temperature-responsiveness with lower critical solution temperature (LCST) in range of 30 °C to 60 °C, depending on the molecular weight of hydrophilic poly(ethylene glycol) (PEG) chains, compositions of copolymers, molar ratios of hydrophilic monomers to hydrophobic ones in corona, and hydrophobic core. This study showed synthetic advancement toward the design and preparation of thermoresponsive biocompatible polymers for injectable drug delivery systems.
9:00 PM - PP9.34
Thermally Responsive Tunable Multiphoton-fabricated Protein Hydrogels.
Eric Ritschdorff 1 , Jodi Connell 1 , Jason Shear 1
1 Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas, United States
Show AbstractThe design of responsive, tunable, bio-compatible smart materials would be of great value for the advancement of microfluidics, biosensors, tissue scaffolds, and single cell analysis. Combining tunable properties with high-resolution, three-dimensional physical features allows for greater control and manipulation of analytical systems. Here, we report studies on the development of tunable multiphoton-fabricated protein hydrogels with high-resolution (i.e., low- to sub-micrometer) three-dimensional topographical features that respond to changes in their local temperature in definable ways. When exposed to elevated temperatures, the materials undergo irreversible volume changes, where the size change of a protein hydrogel is dictated by its photofabrication routine. Microstructures composed of various proteins, including bovine serum albumin (BSA), lysozyme, avidin, and ovalbumin have been investigated and have shown to respond to increasing temperatures in varying ways. Of these proteins, for example, BSA hydrogels undergo a volume increase with increasing temperature, while avidin hydrogels undergo a volume decrease. Although the changes are thermally irreversible, the protein hydrogels can be returned to their original dimensions by altering the local chemical environment through a change in ionic strength or pH. The development of tunable, biocompatible hydrogels has been applied to the study of single cells, particularly for the study of isolated bacterium.
9:00 PM - PP9.35
Self-assembly of Phosphotriesterase Nanogels for Enhanced Bioactive Detoxification and Decontamination.
Qi Zhu 1 , Ming Yan 1 , Juanjuan Du 1 , Yunfeng Lu 1 , Yi Tang 1
1 Chemical & Biomolecular Engineering, University of California, Los Angeles, Los Angeles, California, United States
Show AbstractWe have been always pursuing an efficient nanobiomaterial for enhanced detoxification and decontamination of organophosphorus insecticides and chemical warfare agents. Phosphotriesterase (PTE) efficiently catalyzes a broad spectrum of organophosphates including insecticide paraoxon and lethal nerve agents, such as sarin, tabun, and soman. But the native enzyme would lose the activity and stability when applied under non-biological conditions. Nanostructured PTE nanogels have been developed as building block for further integration through surface modification and delicate in-situ polymerization at a single molecular enzyme level. These nanostructured PTE nanogels gained fabulous stability to temperature, maintaining 90% activity for at least 60min under 65 °C, where the native enzyme had been denatured completely. Nanogels disperse in either organic solvent or aqueous solutions because of their designable surface properties, with the average diameter in the range of 15-50nm. Not like its natural counterpart, synthesized PTE nanogels displayed great potential in both interfacial self-assembly and hybrid self-assembly. Nanogels aggregate into different nanostructures, such as honeycomb films and micro-networks, which could be directly fabricated into membrane, micro-particles and fiber for protective spray, barrier and filter without activity and stability compromising. These self-assembly nanostructures would lead to a cost efficient, reliable and robust bioactive detoxification technology.
9:00 PM - PP9.36
Print-molding of Multiscale Topography for Improved Alignment and Controlled Adhesion of Cardiomyocyte Sheets.
Rebecca Taylor 1 , Chen-rei Wan 2 , Roger Kamm 2 , Beth Pruitt 1
1 Mechanical Engineering, Stanford University, Stanford, California, United States, 2 Mechancial Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractMyocardial infarction (heart attack) results in local tissue death due to lack of oxygen, and this damage is irreversible due to limited regenerative capacity of the heart. However, engineered cardiac tissue grafts hold potential to aid and direct repair of the infarcted heart. Cardiomyocyte (CM) alignment and morphology are integral to its function, and in vitro structuring of tissue grafts presents a key hurdle facing cardiac tissue engineers. While current methods of applying surface topography [Bursac et al, Circulation Research 2002] and micropatterned proteins [Feinberg et al, Science 2007] have yielded highly anisotropic, ordered CM cultures, these 2D tissue constructs are not retrievable from their patterned substrate without a sacrificial layer such as the thermosensitive polymer Poly N-Isopropylacrylamide (PNIPAAm). [Hirose et al, Biomacromolecules 2000] [Shimizu et al, Circ Res 2002]We present a method for applying multiscale patterns of Poly N-Isopropylacrylamide (PNIPAAm) using microcontact printing techniques. Previous techniques demonstrated PNIPAAm surface coatings on grooved substrates are capable of driving cell alignment [Isenberg et al, Biomaterials 2008]. In this work, we demonstrate print-molding of viscous aqueous and solvent-based solutions of PNIPAAm onto wells of 48-well tissue culture plates to directly form the 10-100 micron-scale topographical patterns on flat substrates. This technique improves cell adhesion by creating a textured surface of prescribed thickness, yet that surface texture can still be dissolved away as needed, e.g. for cocultures or directed release. With multiple layers, wide (500μm) lines of PNIPAAm can be applied to define the shape of cell sheets while thinner lines (<20μm) can be applied to drive the precise alignment of cells. Furthermore, since polymer dissolution times ranging from 5 seconds to multiple hours can be tuned via concentration gradients, multiple printed patterns of PNIPAAm can be used as independently controlled release switches. These techniques were demonstrated with both stem-cell derived murine CM and primary neonatal rat CM cultures for directed organization, enhanced surface adhesion, and controlled retrieval of functional cell sheets.
9:00 PM - PP9.37
Ceria Nanoparticles Improve the Bio-mechanical Properties of PLGA Scaffolds for Regenerative Medicine.
Corrado Mandoli 1 , Francesca Pagliari 2 , Giancarlo Forte 2 , Silvia Licoccia 2 , Paolo Di Nardo 2 , Enrico Traversa 1 2
1 , National Institute for Material Science, Tsukuba Japan, 2 , University of Rome Tor Vergata, Rome Italy
Show AbstractThe possibility to design biocompatible hybrid systems having organic and inorganic components is a promising way to implement further functionalities in biomaterials for Tissue Engineering (TE) and to reach unprecedented bioactivity properties. Several ceramics, including calcium phosphate, titanium oxide and hydroxyapatite have been used in conjunction with different biopolymers, mainly for hard TE purposes, with the aim to improve the polymer strength, cell to bone attachment and bone in-growth. In particular, nanostructured cerium oxide (nCeO2) has been recently identified as a promising material for the therapeutic treatment of diseases caused by radical oxygen species (ROS), such as retinal damaging, cardiovascular pathologies, and neurodegenerative disorders. In nCeO2, cations can reversibly switch from the Ce4+ to the Ce3+ oxidation state, upon cyclic oxygen exchange with the surrounding. The presence of the Ce3+ / Ce4+ mixed valence states on the nCeO2 surface is responsible for ROS scavenging activity from the cellular system, and for imparting the capacity of a catalytic oxidative recovery (Ce4+ → Ce3+), thus acting as an ideally inexhaustible, self-regenerating antioxidant agent. Aim of this work is to investigate nCeO2 properties once embedded into a bio-polymeric matrix. The investigation of the synergistic effects that this interaction may induce on both mechanical and biological properties of the composite constituted the aim of this work. Hybrid 2D polymeric-ceramic supports were fabricated by mixing a nCeO2 powder with 85:15 poly (lactic-co-glycolic acid) (PLGA) / dichloromethane solutions at specific concentrations, followed by solvent casting onto pre-patterned moulds. Morphological and mechanical characterization of the hybrid supports was carried out using scanning electron microscopy (SEM) and tensile testing, respectively. The preparation of 3D scaffolds was tested using thermal phase separation method. The ability of the produced supports to host and address cell growth was evaluated by means of immunofluorescence (IF) and cell counting at various culturing times with murine derived cardiac and mesenchymal stem cells (CSCs and MSCs). Scaffold patterning was found to be effective in driving oriented cell growth only when coupled to oriented ceramic powder incorporation, while no significant orientation and lower cell attachment were detected for patterned ceramic-free supports. These effects were attributed to the nano-ceramic ability to modulate the roughness pitch, thus improving cell sensitivity towards the host surface features. In addition, higher proliferative activities were observed for both CSCs and MSCs cultures in the presence of nCeO2 with respect to pure PLGA. This evidence could be related to the nCeO2 antioxidative properties.
9:00 PM - PP9.38
Cells Response and Protein Adsorption on Bioinspired Substrates with Extreme Wettability Properties
Wenlong Song 1 , Catarina Custódio 1 , Joao Mano 1
1 Dept. Polymer Engineering, 3B's group, University of Minho, Guimarães Portugal
Show AbstractEngineering the surface wettability has attached great interest because of its applications in biology or biotechnology, including in cells or protein response on biomaterials either to be used in conventional therapies or in tissue engineering. In this context, it is very important to understand the correlation of the surface energy / wettability on cell attachment and protein absorption onto biomaterials substrates. However such studies are usually performed onto smooth substrates, where the surface wettability ranges from hydrophilic to hydrophobic. There are both fundamental and practical interest in extending such studies towards the superhydrophilic (contact angles below 5°) and superhydrophobic (contact angles greater than 150°) limits. Information in this context could bring new possibilities in areas such as biological diagnosis, antimicrobial or hemocompatible surfaces, and biomaterials for tissue engineering applications or microfluidics.Biomimetic superhydrophobic poly(L-lactic acid) substrates with hierarchical micro and nano scale structures were prepared using a simple phase-separation based method [1], inspired by the self-cleaning surfaces found in nature, such as in the lotus flower. The wettability of such kind of surfaces within extreme limits (superhydrophobic to superhydrophilic) can be controlled by argon (Ar) plasma treatment. The materials obtained were evaluated by scanning electron microscopy, water contact angles and X-ray photoelectron microscopy. We also evaluate the interaction of the developed surfaces with mammalian cells and proteins, in which a mouse lung fibroblast cell line (L929) and labeled human serum albumin (HSA-555) were used. Furthermore, the influence of the exposition time to Ar plasma on cell adhesion or proteins absorption on the developed surfaces was accessed. Finally, it was possible to control spatially the wettability of the surfaces, by using masks that allow to expose the plasma just on some regions of the substrates. The results obtained open new directions for the use of surfaces super-repellent to water, and we believe that potential applications will emerge in the biomedical and biotechnological fields.[1] W. Song, D.D. Veiga, C.A. Custódio, J.F. Mano, Adv. Mater., 21, 1830 (2009)
9:00 PM - PP9.4
Cell-surface Interaction Between Human Osteo-Sarcoma (HOS) Cell and Biomaterials.
Guoguang Fu 1 2 , Winston Soboyejo 1 2
1 Princeton Institute of Science and Technology of Materials, princeton university, Princeton, New Jersey, United States, 2 MAE, princeton university, Princeton, New Jersey, United States
Show AbstractThe adhesion of human osteo-sarcoma cells on surface is a key issue for the study of bone cancer transfer. Research work has been done on the measurements of adhesion strength and the cell spreading on micro-textured polydimethylsiloxane (PDMS). HOS cells were cultured in vitro on selected biomaterials surfaces that are relevant to implantable biomedical systems. The interfacial strengths between single cancer cells and biocompatible materials were measured under shear flow. Immuno-fluorescence staining revealed the sub-cellular adhesion between focal adhesion proteins and extra-cellular matrix (ECM) proteins. The spreading, alignment and integration of cells were also studied on micro-textured PDMS surfaces with systematic changes in groove height and spacing. The implications of the results were assessed for cell biophysics, and potential applications in implantable BioMEMS.
9:00 PM - PP9.5
Alginate Nano- and Microparticles as Carriers of Anticancer Drug Cyclophosphane.
Yerkesh Batyrbekov 1 , Dinara Rakhimbaeva 2 , Kuanyshbek Musabekov 2 , Bulat Zhubanov 1
1 , Institute of Chemical Sciences, Almaty Kazakhstan, 2 , Kazakh State University, Almaty Kazakhstan
Show AbstractThe aim of this work is the development of nano- and microparticles of alginate calcium gel loaded by anticancer drug cyclophosphane.The alginates is a natural copolymer composed of D-mannuronic acid (M) and L-guluronic acid (G) arranged in MM and GG blocks interrupted by regions of more random distribution of M and G units. Modified microparticles were obtained by syringed dropwise a solution of drugs in solution of sodium alginate was into a mixed solution of guar gum. We prepared drug-loaded alginate gel beads on the base of various sodium-alginate with three different M/G ratios, those imply on the difference in time of gel disintegration. The release of drugs from the modified alginate gel microparticles into a physiological solution with different thickness of a guar gum coating was studied. The effect of polymer concentration and the drug loading (1.0, 5.0 and 10%) on the release profile of cyclophosphane was investigated. All the release data show the typical pattern for a matrix controlled mechanism. The cumulative amount of drug released was linearly related to the square root of the time and the release rate decreased this time. The process is controlled by the diffusion of drugs through the polymeric coating. The anticancer action of modified alginate systems was determined at rats by injection a malignant Rhabdomyoma strain into tail vein of animals. Medical-biological tests of the anticancer Drug Delivery System on the basis of modified alginate nano- and microparticles have shown reduced toxic action of anticancer drugs compared with injection. The data shown a possibility of the regulation of the rate of anticancer drugs release from the modified alginate nano- and microparticles by way of alternation of thickness of the polymer coating.
9:00 PM - PP9.6
Design and Properties of Composite Protein – Quantum Dot Biomaterials.
Ravish Majithia 1 2 , Jan Patterson 3 , Sarah Bondos 3 , Kenith Meissner 2 1
1 Material Science and Engineering, Texas A&M University, College Station, Texas, United States, 2 Department of Biomedical Engineering, Texas A&M University , College Station, Texas, United States, 3 Department of Molecular and Cellular Medicine, Texas A&M Health Science Centre , College Station, Texas, United States
Show AbstractAs biomaterials, elastomeric protein-based materials, such as spider silk and elastin, have great potential for application in areas including biosensing and medical imaging. Recombinant versions of such protein molecules would enable efficient production and enhance desired material properties. However, synthesis of recombinant elastomeric proteins often requires long intervals of time, high temperatures, organic solvents or extreme pH thus limiting functionalization by genetic methods. The recombinant protein, Ultrabithorax (Ubx), a Drosophila melanogaster, has been found to self assemble in moderate conditions at the air-water interface into fibrils and films1. These self adhering nano sized structures allow the construction of more complex macro scaled architectures such as fibres, sheets and bundles by simply contacting the assembled material at the air-water interface and pullingAlong with the ability to express functional motifs such as EGFP within the primary protein structure, altering conditions during self assembly can augment mechanical, morphological and optical properties of the Ubx structures. The addition of nanoparticles such as quantum dots during the process allows the construction of novel nanocomposites. Quantum dots (QD) offer unique optical properties including size tunable photoluminescence and high photobleaching resistance. Fabrication of the Ubx-QD nanocomposites has been accomplished via numerous routes namely, I) Exposing Ubx protein to QD suspended in apolar solvents post self assembly on the air-water interface but prior to pulling ropes; II) By varying the surface chemistry of the QD suspended in water and introducing them to the Ubx protein pre and post self assembly.Transmission electron microscopy (TEM), Scanning electron microscopy (SEM) and confocal microscopy were employed to study the structure and QD distribution inside the nanocomposites. Exposing Ubx protein to apolar solvents containing QD drastically alters the morphology, as observed by SEM and confocal images, with multiple tubules inside a single rope. Such composites could find interest as chemically functionalizable optical fibers. Confocal and TEM images of nanocomposite ropes and films drawn by mixing protein buffer with QD, having a negative surface charge, prior to self assembly shows that they have a homogenous distribution of the QD inside the protein. Also they have higher stability and strength as compared to straight Ubx ropes . Confocal images of nanocomposite ropes drawn with positively charged QD, introduced post self assembly of the protein on the air-water interface, shows a tendency to form a ‘QD-core’ inside the rope. The synergistic system of QD-Ubx composite materials, which offers multiple control parameters, leads to a family of structurally and functionally distinct materials with a rich combination of options for various end applications.(1)Greer, A. M. & Huang, Z. et. al. Biomacromolecules.2009,10,829-837
9:00 PM - PP9.7
Sodium Caseinate Stabilized Zein Colloidal Particles.
Ashok Patel 1 , Krassimir Velikov 1
1 Structured Materials and Process Science, Unilever R&D, Vlaardingen Netherlands
Show AbstractZein, a group of proline rich (Prolamines), have being recently studied as potential biomaterial for the development of delivery systems. The insoluble characteristic of zein makes them a good candidate for development of water insoluble biopolymeric nanoparticles which can be used for controlled delivery of drugs or nutrients. However, use of zein colloids for oral delivery is questionable because zein has an isoelectric point at pH 6.8 and thus colloidal particles of zein start aggregating at neutral–basic pH thus loosing its colloidal structure and resulting in physical instability at physiological basic pH. The present work was carried out with an aim of stabilising zein colloids using an edible biopolymer (Sodium caseinate). Colloidal particles with size ranging from 120-150 nm and negative surface charge (-30 to -60mV) were obtained using 1- 2% w/v Sodium caseinate as stabilizer. The particles formed were spherical in shape with smooth surface, as confirmed by transmission electron microscopy. Using sodium caseinate as stabilizer, we could obtain discrete colloidal particles of zein which retained the property of redispersibility after drying. The presence of caseinate resulted in stabilizing the particles at neutral pH by preventing the aggregation of zein near its native isoelectric point. Colloidal dispersion was found to retain physical stability for over 2 month of storage at both 5°C and ambient temperature. Further, it was seen that caseinate stabilized zein colloidal particles also showed improved stability against ionic strength of 15mM to 1.5M NaCl. Solid state characterization was carried out using DSC, XRD and FTIR and results suggested absence of any chemical interactions. Protein hydrolysis study (OPA method & pH stat method) confirmed that the presence of caseinate did not alter the digestability of zein colloid. Given the fact that the colloids had lower digestibility in intestinal conditions, the formulation has the potential to be used as controlled delivery system for encapsulating/embedding bioactive molecules for oral delivery.
9:00 PM - PP9.8
Preparation of Supported Lipid Bilayers on a Permeable Nanofiltration Substrate for Selective Water Filtration.
Yair Kaufman 1 2 , Amir Berman 2 , Viatcheslav Freger 1 2
1 Zuckerberg Institute for Water Research, Ben-Gurion University, Sde-Boqer 84990 Israel, 2 Department of Biotechnology and Environmental Engineering, Ben-Gurion University, Beer-Sheva Israel
Show AbstractCells selectively pass water in and out owing to the combination of the low permeability of the plasma membrane and high permeability and selectivity of specialized trans-membrane proteins called water channels or aquaporins. The water permeability and selectivity of cell membranes is much higher than today’s commercial membranes for water desalination. On the other hand, biological membranes mostly utilize osmotic rather than mechanical pressure as the driving force for water transport, which is not as attractive from technical viewpoint. In this paper we explore the possibility of using an appropriate biomimetic membrane for pressure-driven water filtration. Towards this goal, we propose using a commercial polymeric nanofiltration (NF) membrane, whose permeability exceeds that of biological membranes, as a support for a lipid bilayer that will allow the use of a mechanical pressure for filtering water. We show for the first time that a supported phospholipid bilayers (SPB) can be prepared on a commercial NF membrane. This was achieved by using the method of vesicle fusion and tuning the interactions between the lipid heads and the polymeric surface through the choice of the solution conditions, lipid composition and substrate membrane. The presence of a continuous SPB on the surface and its morphology were verified and quantified by several spectroscopic and microscopic techniques. They showed that a continuous bilayer with very few defects and some proportion of unruptured vesicles could uniformly seal the substrate surface. Ultimately, the filtration tests showed that the hydraulic permeability of the SPB supported on the NF membrane (NTR7450) closely approached the value deduced from typical osmotic permeability of intact continuous bilayers, and also sustained repeated filtration cycles. In addition using a bilayer of the same composition on mica we found that it could reasonably well incorporate aquaporins. These results suggest that such SPBs may be used as a platform for preparing biomimetic filtration membranes with superior performance based on aquaporins. The concept of SPBs on permeable substrates of the present type may also be useful for studying transport of various molecules through trans-membrane proteins.
9:00 PM - PP9.9
Effects of Soluble Factors from Pseudowollastonite (beta-CaSiO3) Dissolution on In Vitro Activity of Human Mesenchymal Stem Cells.
Nianli Zhang 1 , Jim Molenda 2 , William Murphy 2 3 4 , John Fournelle 1 , Nita Sahai 1 5
1 Department of Geoscience, University of Wisconsin, Madison, Wisconsin, United States, 2 Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin, United States, 3 Department of Orthopedics and Rehabilitation, University of Wisconsin, Madison, Wisconsin, United States, 4 Department of Pharmacology, University of Wisconsin, Madison, Wisconsin, United States, 5 Material Science Program, University of Wisconsin, Madison, Wisconsin, United States
Show AbstractThe motivation of our study was to determine the effects of silicate bioceramic surface texture on the release of soluble factors, subsequent surface precipitates, and the resulting variations in the attachment, viability, proliferation, and differentiation of human Mesenchymal Stem Cells (hMSCs), for improved design of osteoinductive bioceramics in tissue engineering applications. Changes in solution composition, surface precipitates, and cell activities were monitored up to 28 days for fine- and coarse-grained pseudowollastonite (psW) pellets incubated with hMSCs in growth and induction media. The fine-grained psW dissolved faster than the coarse-grained surface, with higher initial Si concentrations and lower Ca and P concentrations due to precipitation of an amorphous calcium phosphate (Ca-P) phase and crystalline calcite (CaCO3). Cell attachment, viability, and differentiation as indicated by gene expression of osteocalcin (OCN), osteopontin (OPN), and core-binding factor-1(Cbfa1) by RT-PCR analysis, were initially lower for the fine-grained surface initially. The higher Si concentrations associated with the finer-grained surface, and the known cytotoxic effect of Si is inferred to be responsible for the observed reduced cell activities at initial time points. Intriguingly, however, proliferation rates over 28 days were greater on the fine-grained surface. In summary, surface texture affects the release rate, and concentrations of soluble factors and surface precipitates formed, which, in turn, affect both cellular (CaP nodule formation) and purely chemical (calcite precipitation) processes. A single soluble factor, such as Si, may have opposing effects on different stages of cell activity, such as proliferation versus viability, and factors acting in concert, such as Si and P, may affect cell activity in complex ways. Thus, optimization of biomaterials for tissue engineering applications will require tuning of multiple factors in concert.