Symposium Organizers
Roger Narayan University of North Carolina
Suwan Jayasinghe University College London
Sungho Jin University of California-San Diego
William Mullins Office of Naval Research
Donglu Shi University of Cincinnati
VV1: Functional Materials and Devices
Session Chairs
Joanna McKittrick
Igor Zhitomirsky
Tuesday PM, December 01, 2009
Room 202 (Hynes)
9:00 AM - VV1.1
Improved Culture Conditions for Measuring T-Lymphocyte Responses for Cell Based Cancer Therapy.
Carole Perry 1 , Graham Hickman 1 , Akhilesh Rai 1 , Balwir Matharoo-Ball 1 , Robert Rees 1
1 School of Science and Technology, Nottingham Trent University, Nottingham United Kingdom
Show AbstractThe interactions between biological systems and biomaterials are of great importance to regenerative medicine. Key to this understanding is assessing how cells react when presented with materials of varying physical and chemical properties. ‘Omics’ technologies such as MALDI mass spectrometry are ideal methods to examine the interactions between cell and surface.To this end we have built upon existing methods for the manufacture of bio-mimetic silica film surfaces with novel chemical and physical properties. Our methods have been able to produce silica surfaces under mild chemical conditions on a range of substrates suitable for use in cell culture applications. These surfaces can be fabricated with characteristics such as wetting properties ranging from hydrophobic to hydrophilic or even super-hydrophilic, depending on the methods used.The initial silica surface produced was trialed as a cell culture surface with a melanoma cell line (FM3) on both a hydrophilic silica surface and conventional cell culture polystyrene. After a period of culturing the culture media and lysed cells were examined using current MALDI based proteomic techniques to generate a peptide mass fingerprint characteristic of the cells cultured on both of the surfaces.Through comparison of the proteomic studies we have determined that the cell culturing surface can have a dramatic effect on the cell proteome. The melanoma line cultured on a hydrophilic silica surface showed a radically altered peptide mass fingerprint as compared with the cells cultured on the traditional cell culture polystyrene surface, both in terms of the proteins expressed into the cell culture media and the proteome of the cell itself. Examination of the morphology of the melanoma cells via optical microscopy showed that while the cells cultured on the different surfaces demonstrated similar morphological characteristics they showed important variations in their expressed proteome.Further investigation with different cells, including different cell surface chemistries in relation to culturing materials with different surface properties should provide great insight into the interactions between biological systems and materials destined for biological applications.
9:15 AM - VV1.2
Cell-Based Detection of Synthetic Pathogens Using Cell Impedance Sensing.
Bhavana Mohanraj 1 , Nate Schiele 1 , Anne Hynes 1 , David Corr 1 , Cerasela Dinu 1 , Douglas Chrisey 1
1 Materials Science and Engineering Department, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractWe demonstrate a new approach to electrically sense pathogens using cells as the receptor-sensing element. Electrical Cell-substrate Impedance Sensing (ECIS) was used to monitor the confluent growth of human dermal fibroblasts and their exposure to an anthrax simulant namely Bacillus cereus. ECIS was conducted at frequencies between 4 – 64 kHz and it was found to be an excellent measure of cell growth, micro-motion, and their overall intracellular and intercellular morphological responses when challenged with various agents. When exposed to the digestive enzyme trypsin we observed an instantaneous and unambiguous change in the capacitance, of approximately 67% at 32 kHz almost instantaneously. When exposed to the anthrax simulant Bacillus cereus spores, we observed no response during germination and a very small response when the bacillus cells thrived in the fibroblast growth media. The ECIS response was consistent with a live-dead assay whereby it was found that no cells had died and no significant morphological change was observed. While Bacillus cereus is in the same genetic family as Bacillus anthracis, its pathological lethality on the cellular level for fibroblasts was negligible. Our work shows that the ECIS measurements were an extremely sensitive measure of fibroblast morphological response. In this presentation, we will challenge prototype biosensors with other biological warfare simulant pathogens such as B. Subtilis or B. Atrophaeus (simulant for smallpox) as well as with against chemical warfare agents dimethyl methyl phosphonate (nerve agent – sarin) and 1,5 dichloropentane (blister agent – mustard gas).
9:30 AM - VV1.3
Implantable BioMEMS for Localized Hyperthermia and Cancer Drug Release.
Yusuf Oni 1 2 , Guoguang Fu 1 2 , Christian Theriault 1 , Alex Van Hoek 1 , Rohith Chandrasekhar 3 , Emily Paetzell 1 2 , Wole Soboyejo 1 2
1 Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States, 2 Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey, United States, 3 Electrical Engineering, Cooper Union, New York, New York, United States
Show AbstractThis paper presents a novel implantable bio-micro-electro-mechanical system (Bio-MEMS) device for the localized treatment of cancer. The device uses a combination of heating (hyperthermia) and drug release to kill breast cancer cells. Cancer drug release is controlled by the use of modified poly(N-iso-propyl-acrylamide) (PNIPA) hydrogels with hydrophobic/hydrophilic copolymers and interpenetrating network structures. The gels are encapsulated in biocompatible poly-di-methyl-siloxane (PDMS) with micro-fluidic channels that convey the drug (paxlitaxel) to cancer cells/tissue. The thermo-sensitive properties (swelling) and fluid/drug release characteristics of the gels are elucidated along with the effects of localized heating with micro-wires. A synergistic killing of breast cancer cells is shown to occur as a result of the combined effects of localized cancer drug release and hyperthermia.
9:45 AM - VV1.4
Micro and Nanopatterning Tools to Produce Biomimetic Chips Based on Molecularly Imprinted Polymers.
Cedric Ayela 1 , Helene Lalo 2 , Samuel Guillon 2 , Thierry Leichle 4 , Fanny Vandevelde 3 , Ana Valvanuz Linares 3 , Liviu Nicu 2 , Karsten Haupt 3
1 , Laboratoire de l'Intégration du Matériau au Système UMR 5218; University of Bordeaux, Talence France, 2 , LAAS-CNRS; University of Toulouse; 7, avenue du Colonel Roche F-31077, toulouse France, 4 , Institute of Physics, Academia Sinica, Taipei 115, Taipei Taiwan, 3 , Univeristé de Technologie de Compiègne, CNRS UMR 6022, Compiègne France
Show AbstractMicro and nanobiochips are of interest in biomedical applications like diagnostic, molecular screening and drug discovery. Recent advances in this field allow introducing technologies to create highly sensitive patterns. Classically, biochips are arrays of natural biomolecules locally immobilized on a surface. However, short life-time and poor stability of natural molecules when used out of their native conditions promotes introduction of alternative sensitive layers, particularly biomimetic polymers. Molecularly imprinted polymers (MIPs) represent a novel area of polymers capable of molecular recognition with the same affinity and selectivity as their natural counterparts. Their synthetic composition offers enhanced long-term stability compared to natural biomolecules. One other advantage of the polymeric matrix, characteristic of MIPs, is their powerful combination with micro and nanotechnologies to create biochips.Here, we present recent approaches developed in our groups to pattern MIPs at micro and nanoscale. First, Micropatterning tools were developed and referenced as contact and non-contact techniques. Contact method is based on array of silicon cantilevers fabricated by micromachining techniques and mounted on a three-stage automated spotter. This resulted in arrays of MIPs serially and precisely localized on a substrate, with resolution down to 20µm. Alternatively, a parallel approach was initiated by taking benefit of photopolymerization of MIPs to create patterns by photolithography. After spin-coating prepolymers, reticulation was initiated using a mask and resulting MIPs were in a wide variety of features with a resolution down to 1.5µm. By repeating sequentially deposition and local polymerization, a multi-array approach was also introduced. Final objective using these techniques is to compare performances of resulting MIPs in terms of sensitivity, integration, mass production and versatility.More recently, evolution of nanotechnologies made possible to engineer nanostructures. Main issues concern high throughput screening and testing with enhanced sensitivity by increasing the surface area of the MIP material. In this field, soft lithography and nanowires approaches are of major interest since they allow producing nanopatterns with high aspect ratio. Both methods succeeded to create MIPs nanofeatures. Nanofilaments were produced with elevated density, resulting in a factor 40 increase of the surface area compared to a flat surface. These conditions favored accessibility to binding sites and in molecular recognition assays, sensitive levels of detection were reached. A similar behavior was also observed when MIPs were patterned by soft lithography. Features were formed as a network of nanolines of 500nm wide and 400µm long with a pitch of 1µm, covering a large area of 400x400µm2. Thanks to developed techniques, we will conclude on perspectives on MIPs micro and nanopatterns as efficient alternatives to create advanced biochips.
10:00 AM - **VV1.5
Bioinspired Inorganic/polymer Thin Films.
G. Hirata 1 , S. Diaz 2 , P. Chen 2 , M. Meyers 2 , Joanna McKittrick 1
1 Mechanical and Aerospace Engineering Department, University of California, San Diego, La Jolla, California, United States, 2 , Center for Nanoscience and Nanotechnology-UNAM, Ensenada Mexico
Show AbstractStudies of hard biological materials such as marine shells, animal teeth, horns and bones have produced fascinating ideas for mimicking their micro/nanostructure in the lab. In this work we have analyzed the morphology ad mechanical properties of the nacreous portions of red abalone shells by SEM, TEM, XRD and the chemical compositions by EDS and ESCA. Bioinspired laminates were fabricated as multi-layers of several biocompatible materials: CaCO3 (aragonite)/polymer, ZrN/polymer and ZrO2/polymer for various polymer compositions, by using a combination of dc magnetron sputtering and pulsed laser deposition on glass, quartz and silicon substrates. Substrate temperatures for film deposition were varied in the range of 25-115°C. The films are composed of nanocrystalline or amorphous particles with different degrees of porosity as observed by TEM and AFM. High resolution TEM analysis at the inorganic/organic interface revealed well formed inorganic films which are separated by the polymeric layer (10-50 nm). The hardness values showed an increase for the inorganic film/polymer stacked system as compared with the single film. A more detailed analysis of the results together with AFM/nanoindentation measurements will be presented. This research is supported by ARO Grant W911F-08-1-0461 and NSF Grant DMR 0510138.
10:30 AM - VV1.6
Bio-electrospray Validation from Cells to Organism.
Suwan Jayasinghe 1
1 Mechanical Engineering, University College London, London United Kingdom
Show AbstractTissue engineering is a field of interdisciplinary sciences being extensively researched as it is a promising and possible solution for organ transplantation. Various biomaterials and cell-seeding techniques have been developed to construct 3-D tissue in the laboratory. However, many problems of seeding cells in 3-D scaffolds pose several challengers. Thus there are numerous approaches invented with regards to handling cells directly. Our technique, bio-electrospray (BES), has been developed to be able to manipulate cells and materials simultaneously. The method was proved that it is feasible to directly jet cells at high concentration without affecting cell viability. Moreover, in this study, cell functions were investigated and presented to assure the possibility of using BES as a strategy for tissue engineering. Hence stem cells (MSC), primary cells (blood) and whole organism (C. elegans) were used to assess their associated biologics post treatment. The metabolic assay result of electrosprayed MSC have shown the same propagation efficiency along 3 days as controls. Cell viabilities, apoptosis by key enzyme assays during 24 hours after jetting and necrosis by PI staining, subsequent FACS scan after jetting, were also investigated. No significant numbers of cell deaths were investigated. Additionally, gene expressions by RT-qPCR on whole blood cells were observed by 13 specific primers to both specific and constitutive genes. Genetic level was reported as delta Ct for 78 cross comparisons. No differences of gene expression among sprayed and non-sprayed samples were observed. Finally the embryo of C. elegans were treated and examined for productivity, heat shocked response and global gene expressions. Brood size experiments have confirmed the egg laying capacity of electrosprayed samples are as efficient as the control, no GFP activation of heat shock responses as well as no significant differences in gene expressions have identified. These experiments have confirmed that BES is capable of directly handling cells for tissue engineering without perturbing viability, proliferation and gene expression. We are currently running tissue creation by using BES to position cells for controllable cell patterning for possible organ construction.
10:45 AM - VV1.7
Nano- and Micro-Scale Adhesion in Drug-eluting Stents.
Ting Tan 1 , Juan Meng 1 , Nima Rahbar 2 , Hannah Li 3 , George Papandreou 3 , Cynthia Maryanoff 4 , Winston Soboyejo 1
1 , Princeton University, Princeton, New Jersey, United States, 2 , University of Massachusetts Dartmouth, North Dartmouth, Massachusetts, United States, 3 , Cordis Corporation, Warren, New Jersey, United States, 4 , Cordis Corporation, Spring House, Pennsylvania, United States
Show AbstractThis paper presents the results of a combined experimental and theoretical/computational study of nano- and micron-scale adhesion and interfacial fracture in drug-eluting stents (DES). We have previously published the development of an atomic force microscopy (AFM) method to quantify the adhesion forces between and cohesive forces within the layers of a drug-eluting stent (DES). Surface pairs representing both the individual components and the complete chemistry of each layer within the DES were prepared, and measurements of the pull-off forces between coated AFM tips and substrates were obtained to evaluate all possible interactions occurring in the DES structures. As a model, the CYPHER® Sirolimus-eluting Coronary Stent was studied. A combination of adhesion theory and fracture mechanics concepts was then used to obtain estimates of the mode I fracture toughness values. The experimental measurements of the mode mixity dependence of interfacial fracture toughness were shown to be consistent with crack-tip shielding estimates from zone/row fracture mechanics models.
11:00 AM - VV1.8
Localized and Sustained Release from Drug-Loaded Implantable Devices.
Dattatri Nagesha 1 , Evin Gultepe 1 , Robert Cormack 2 , Mike Makrigiorgos 2 , Srinivas Sridhar 1
1 Physics, Northeastern University, Boston, Massachusetts, United States, 2 Radiation Oncology, Dana Farber Cancer Institute, Boston, Massachusetts, United States
Show AbstractThere are a number of biomedical implants that are used today that are capable of localized drug delivery for improved therapy, enhanced tissue adhesion, decreased immune response and biocompatibility. Non-erodible surfaces especially nanoporous alumina and titania have been used for improved drug loading and release capabilities. However, there is a poor understanding on the elution kinetics of drugs from within these nanoporous surfaces. To study this, nanoporous alumina templates with precise control on pore size, distribution and height was fabricated by anodization method. Templates were loaded with fluorescent Doxorubicin (Dox) as the model drug molecule and release of Dox was monitored using in-situ fluorometry. After an initial burst release phase during the first 100 minutes, which follows non-Fickian diffusion, a long time sustained release followed for several weeks. Constructing a model for sustained release kinetics show that activated surface densities dependent desorption was in effect for nanoporous templates. In localized drug delivery from drug-loaded implants from within tumor sites there is lack of theoretical modeling to predict drug distribution and diffusion upon release. This was studied using drug-loaded polymer coatings on gold fiducial markers. Currently, these markers are used to increase spatial accuracy in delivering radiation treatment for cancer therapy. Elution of drugs locally from these fiducials from within the tumor can further enhance their role as a treatment modality. Results from the modeling study of drug diffusion and in vitro drug release experiments from these fiducials will be discussed in this presentation. This work was supported by IGERT Nanomedicine Science and Technology Program (NSF 0504331), Dana Farber Cancer Institute and Northeastern University
11:15 AM - VV1.9
Effect of Processing Conditions on the Microstructure and Sirolimus Elution from Poly (lactide-co-glycolide) Films.
Andrew Ro 1 , Robert Falotico 1 , Vipul Dave 1
1 Therapeutics and Advanced Research, Cordis Corporation, Johnson and Johnson, Warren, New Jersey, United States
Show AbstractSupercritical carbon dioxide is a viable solvent to process drug-containing polymer devices for drug delivery. It can also be used to modify the morphological features of both polymer and drug at mild temperatures, which presents a prospect to tune drug release and degradation of the device. Poly (L-lactide-co-glycolide) (PLLGA) and poly (DL-lactide-co-glycolide) (PDLGA) films containing sirolimus were prepared using a solution-casting method. Various combinations of processing parameters (e.g. temperature and pressure) were used during supercritical CO2 extraction in order to remove residual solvent and to obtain various polymer and drug morphologies. The morphological features of polymer and drug were characterized by x-ray scattering and differential scanning calorimetry. A range of polymer and drug crystallinities were obtained and the resultant morphologies were dependent on supercritical CO2 extraction conditions and the stereochemistry of the polymer. Heat of fusion values for the polymers ranged from 0 to 40 J/g and the values correlated with the stereoregularity of PLGA. The drug phase in the PLGA films exhibited heat of fusion values ranging from 7 to 46 J/g and was dependent on the chemistry of the PLGA matrix and processing conditions. Surface features of the sirolimus-containing films were analyzed using electron microscopy. Depending on the physical properties of the polymer and drug, the sirolimus-containing PLGA films exhibited unique drug release profiles and in vitro degradation behavior. Crystallinity and stereochemistry of the PLGA matrix were significant determining factors for drug diffusion kinetics.
11:30 AM - VV1.10
Unique Mechanical Properties from Melt Processing Polylactide.
Jianbin Zhang 1 , SuPing Lyu 1 , Lian Luo 1 , Byrant Pudil 1 , Jim Schley 1 , Mike Benz 1 , Adam Buckalew 1 , Kim Chaffin 1 , Chris Hobot 1 , Randy Sparer 1
1 Medtronic Strategy and Innovation, Medtronic, Minneapolis, Minnesota, United States
Show AbstractPoly(lactide) (PLA) and its copolymers can degrade through hydrolysis to non-toxic and water soluble metabolic products. They are ideal materials for biomedical applications like drug delivery, tissue engineering, orthopedics, and etc. However, these polymers are brittle and often need to be toughened. One of the most effective toughening methods is reactive blending. In this paper, we reported unique mechanical properties created by dispersing poly(trimethylene carbonate) (PTMC) in poly(lactide-co-glycolide) (PLGA) on the nanometer scale through reactive blending at high temperature. We speculated that the reaction was a transesterification reaction between the two polymers, which late was proven to be true by a model experiment. A fluorescence-labeled PTMC was designed in such a way that it can be used to detect the reaction between polymers if there is any. After melt-blended the fluorescence-labeled PTMC into the PLGA, the molecular weight results demonstrated the formation of PTMC-PLGA copolymers. We demonstrated that these in situ formed copolymers not only make it feasible for the PTMC phase to form stable nanometer-scale dispersion in the PLGA, it was also required for improved interfacial mechanical performance. This was demonstrated by another experiment where scanning electron micrographs showed that the interfacial adhesion between PLGA/PTMC in a melt-mixed blend was strong and the PTMC dispersed particles stayed at cryo-fractured surfaces.
11:45 AM - VV1.11
Laser Processing of Functional Microstructured and Nanostructured Biomaterials.
Roger Narayan 1 , Ashok Kumar 2
1 Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, United States, 2 Mechanical Engineering, University of South Florida, Tampa, Florida, United States
Show AbstractLasers may serve to create novel biomaterials with unique biological functionalities. We have recently developed microstructured and nanostructured biomaterials with unique biological functionalities using pulsed laser deposition and laser direct writing processes. For example, lasers have recently been used to fabricate biomaterials with unusual cell compatibility and blood compatibility properties. Chemical, mechanical, and biological properties of these laser-processed materials will be discussed.
12:00 PM - **VV1.12
Structure-property linkages in hierarchically structured hybrid biomaterials
Ulrike Wegst 1
1 Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractOne of the major challenges in Tissue Engineering is to develop custom-designed scaffolds, tailored to mimic natural biological templates and designed to actively regulate cell differentiation and tissue assembly. Shortcomings of current tissue scaffolds are that they are chemically, structurally and mechanically very different from the natural tissue for which they substitute. Most current bone substitute materials, for example, are monolithic. This is in contrast to natural bone and other biological ceramics such as, dentin, enamel and mollusk shell which are composites and achieve their unique property combination due to their hierarchical structure. A promising route for the synthesis of tissue substitute materials thus seems to be the emulation of tissue’s hybrid structure because this will allow us to custom-design the materials through variations in composition and structure so that it can simultaneously and optimally fulfill biological and mechanical requirements. We systematically develop hierarchically structured composites that are tailored and optimized in their structural, mechanical, and chemical properties for tissue engineering applications. Preparing tissue scaffolds by freeze-casting (“ice-templating”) of polymers, ceramics and composites we have careful control of material composition and architecture at several length scales of their hierarchical microstructure. This enables us to prepare scaffolds for both hard and soft tissue applications and to deliver the required unique combination of properties necessary for successful tissue replacement.
12:30 PM - VV1.13
Microfabrication of Asymmetric, Homogenous Cell-laden Hydrogel Microcapsule.
Tram Dang 1 , Qiaobing Xu 1 , Kaitlin Bratlie 1 3 , Esther O'Sullivan 4 , Xiao Chen 1 , Robert Langer 1 2 , Daniel Anderson 2
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Department of Anesthesiology, Children Hospital Boston, Cambridge , Massachusetts, United States, 4 Islet Transportation and Cell Biology, Joslin Diabetes Center - Harvard Medical School, Boston, Massachusetts, United States, 2 David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge , Massachusetts, United States
Show AbstractCell encapsulation has been broadly investigated as a technology to provide immunoprotection for transplanted endocrine cells. Here we develop a new fabrication method that allows for rapid, homogenous microencapsulation of insulin-secreting cells with varying microscale geometries and asymmetrically modified surfaces. Micromolding systems were developed using polypropylene mesh, and the mesh material/surface properties associated with efficient encapsulation were identified.Cells encapsulated using these methods maintain desirable viability and preserve their ability to proliferate and secrete insulin in a glucose-responsive manner. This new cell encapsulation approach enables a practical route to an inexpensive and convenient process for the generation of cell-laden microcapsules without requiring any specialized equipment or microfabrication process.
12:45 PM - VV1.14
Novel Encapsulation Strategies Designed for Block Copolymers.
Conlin O'Neil 1 , Diana Velluto 1 , Andrija Finka 2 , Davide Demurtas 3 , Jeffrey Hubbell 1
1 Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland, 2 Department of Plant Molecular Biology, University of Lausanne, Lausanne, Vaud, Switzerland, 3 Center for Integrative Genomics, University of Lausanne, Lausanne, Vaud, Switzerland
Show AbstractAlthough block copolymers have been under intense investigation for decades, it was not until recently with the development of biodegradable chemistries such as hydrolysis, oxidation, and reduction sensitive materials that these systems could be fully exploited as drug carriers. Conventional methods to load therapeutic small molecule drugs or proteins into block copolymer micelles, worm like micelles or polymersomes were originally developed for use with liposomes, emulsions, or small molecule natural and synthetic amphiphiles. However, conventional methods such as solvent dispersion or thin film hydration do not always yield optimal results. Recently, our group has explored the use of block copolymers composed of poly(ethylene glycol)-bl-poly(propylene sulfide) (PEG-PPS), towards drug delivery. For some therapeutic compounds, conventional methods yield high encapsulation efficiencies such as for rapamycin (89% efficiency at 16% loading), or ADAMTS-5 inhibitor (~100% efficiency at 16% loading). However for other small molecule therapeutics, these methods yielded poor results, such as for paclitaxel (4% efficiency at 1% loading). To improve the encapsulation efficiency, an entirely new process was applied which we are calling “direct hydration”. In this process, the neat paclitaxel is heated at 95C for 15-20 minutes with a small molecular weight polyethylene glycol and PEG-PPS. After the melt cools to room temperature, the formulation is rehydrated with an aqueous buffer and this yields loaded micelles displaying high encapsulation efficiencies (88% efficiency at 14% loading for paclitaxel). For cyclosporin A we obtained good results using solvent evaporation from dichloromethane in water (61% efficiency at 3% loading). However we wanted to develop a solvent free method to encapsulate the drug due to concerns over residual solvent. We found that heating the cyclosporin A in the presence of PEG-PPS micelles in water at 60C with stirring partitioned most of the compound into the micelles (73% efficiency at 5% loading). We have also recently been investigating the encapsulation of proteins using the direct hydration method. Here we use PEG-PPS which typically forms polymersomes. The protein of interest can be dispersed into the formulation, encapsulating it inside the aqueous core of the polymersomes. Using this method, we have encapsulated ovalbumin at 37%, bovine serum albumin at 19%, and bovine γ-globulin at 15% efficiency. These numbers represent a substantial improvement over conventional thin film hydration which typically yields efficiencies < 10%.In this presentation I will discuss these new methods and their implications for drug delivery for the next generation of polymeric self-assembling systems.
VV2: Microstructured and Nanostructured Biomaterials
Session Chairs
Sungho Jin
William Mullins
Tuesday PM, December 01, 2009
Room 202 (Hynes)
2:30 PM - **VV2.1
Engineering of Micro- and Nano-Scale Materials to Control Cell Morphology.
Michael Bucaro 1 , Benjamin Hatton 1 , Joanna Aizenberg 1
1 , Harvard University, Cambridge, Massachusetts, United States
Show AbstractSmart biomaterials that can actively guide cell form and fate will enable new solutions in regenerative medicine. We describe a strategy to create multifunctional, actuatable, cell-biomaterial interfaces based on nanopillar arrays. Morphological characteristics of uncommitted cells were manipulated by tailoring the length and distribution of nanostructures. Nanopillar geometries were identified that induce neuron-like morphologies in undifferentiated cells. The results demonstrate the use of conventional silicon fabrication methods to create tunable nanobiomaterials capable of eliciting a spectrum of morphological characteristics and patterned growth in pluripotent cells. This approach is compatible with integrated circuit fabrication and could be applied to create bioinductive surfaces that probe and direct cell behavior, for example, in the formation of cellular networks on neural chips, stem cell lineage specification and manipulation of cell activity for a variety of biomedical applications.
3:00 PM - VV2.2
Biomaterials Nano Geometry for Control of Stem Cell Differentiation.
Karla Brammer 1 , Seunghan Oh 1 2 , Sungho Jin 1
1 Materials Science & Engineering, UC San Diego, La Jolla, California, United States, 2 College of Dentistry, Wonkwang University, Iksan Korea (the Republic of)
Show AbstractTwo important goals in stem cell research are to control the cell proliferation without differentiation, and also to direct the differentiation into a specific cell lineage when desired. Recent studies indicate that the nanostructures substantially influence the stem cell behavior. It is well known that mesenchymal stem cells (MSCs) are multipotent stem cells that can differentiate into stromal lineages such as adipocyte, chondrocyte, fibroblast, myocyte, and osteoblast cell types. By examining the cellular behavior of MSCs cultured in vitro on nanostructures, some understanding of the effects that the nanostructures have on the stem cell’s response has been obtained. Here we demonstrate that TiO2 nanotubes produced by anodization on Ti implant surface[1] can regulate human mesenchymal stem cell (hMSC) differentiation towards an osteoblast lineage in the absence of osteogenic inducing factors. Altering the dimensions of nanotubular-shaped titanium oxide surface structures independently allowed either augmented human mesenchymal stem cell (hMSC) adhesion at smaller diameter levels or a specific differentiation of hMSCs into osteoblasts using only the geometric cues. Small (~30 nm diameter) nanotubes promoted adhesion without noticeable differentiation, while larger (~70 - 100 nm diameter) nanotubes elicited a dramatic, ~10 fold stem cell elongation, which induced cytoskeletal stress and selective differentiation into osteoblast-like cells[2], offering a promising nanotechnology-based route for novel orthopaedics-related hMSC treatments. The fact that a guided and preferential osteogenic differentiation of stem cells can be achieved using substrate nanotopography alone without using potentially toxic, differentiation-inducing chemical agents is significant, which can be useful for future development of novel and enhanced stem cell control and therapeutic implant development.1. Seunghan Oh, et al, J. Biomed. Mater. Res. 78A, 97 (2006).2. Seunghan Oh, et al, PNAS 106(7), 2130 (2009).
3:15 PM - VV2.3
The Wear Properties of Ultra High Molecular Weight Polyethylene (UHMWPE) for applications to Metal-on-UHMWPE Total Hip Replacement against Ti Composite Layers produced by Plasma-Spraying.
Seung-mok Cho 1 2 , Hyun-Kwang Seok 1 , Seung-hee Han 1 , Jin-Woo Park 2 , Yu-Chan Kim 1
1 Materials science & technology research division, Korea Institute of Science & Technology, Seoul Korea (the Republic of), 2 Department of Materials Science & Engineering, Yonsei University , Seoul Korea (the Republic of)
Show AbstractWe present titanium composite coating layers with excellent wear properties produced by plasma-spraying process for applications to artificial hip joints. Using the Ti composites coatings, the wear rate of ultra high molecular weight polyethylene (UHMWPE) in metal-on-UHMWPE total hip replacement is reduced significantly compared to Co alloy coatings that have been most extensively used. The Ti coating layers are produced in controlled atmospheres of Ar or N2 in a chamber. Under N2 atmosphere, coating layers with laminated Ti and TiN layered structures are produced and the wear properties are better than the coatings under Ar atmosphere. To evaluate the wear properties, pin-on-disk type wear tests of UHMWPE against the Ti composite coatings with various thicknesses and different microstructures are performed in bovine serum lubrication. The microstructures of the coatings are analyzed using scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). Hardness and surface roughness are analyzed by nano-indentation and atomic force microscopy (AFM), respectively. Based on the analysis results, the different wear mechanisms of the various coatings are discussed. Finally, biocompatibility of coating layers are evaluated under ISO 10993-1, ISO 10993-5 standards.
3:30 PM - VV2.4
Fabrication of (Ti-O-N-Si)/Ti Composite Coating on NiTi Shape Memory Alloy Using PIIID and Coating Evaluation.
Tao Sun 1 , Lang-Ping Wang 2 , Min Wang 1
1 Mechanical Engineering, The University of Hong Kong, Hong Kong China, 2 Materials Science and Engineering, Harbin Institute of Technology, Harbin China
Show AbstractNiTi shape memory alloys (SMAs) are attracting increasing attention in orthopedics and dentistry due to their unique properties of shape memory and superelasticity. But problems such as bioinertness, Ni ion release and wear debris generation have prevented them from wide applications in the medical field. Appropriate surface modification of NiTi SMAs can eliminate or minimize these problems and provide the new scope of medical applications for these materials. Various techniques have thus been investigated for the surface modification of NiTi SMAs and these techniques have their respective advantages and disadvantages. In this investigation, to achieve a good combination of bioactivity, biocompatibility and wear resistance, thin (Ti-O-N-Si)/Ti composite coatings were fabricated on a NiTi SMA (50.8 at.% Ni) by using a combination of the plasma immersion ion implantation and deposition (PIIID) technique and the radio frequency (RF) magnetron sputtering technique. PIIID, which avoids the “line-of-sight” problem encountered by many coating techniques for metal implants, can produce coatings on the surface of implants of complex shapes and the coatings formed possess high adhesion strength. For obtaining (Ti-O-N-Si)/Ti composite coatings, a Ti layer was fabricated first on NiTi SMA in order to improve the adhesion strength of the composite coatings. Subsequently, O2 and N2 plasma were generated simultaneously in the PIIID equipment and a Ti-O-N layer formed on the Ti layer. Finally, Si was introduced into the Ti-O-N layer through RF magnetron sputtering. After coating fabrication, the structure and properties of composite coatings were studied. XRD results showed that there were no diffraction peaks corresponding to TiO2 or TiN for (Ti-O-N-Si)/Ti composite coatings, indicating that after the coating fabrication process, TiO2 and TiN were not formed in the coatings. SEM examination of coating surfaces and cross-sections indicated that (Ti-O-N-Si)/Ti composite coatings were uniform and compact, having thickness values of about 1μm to 1.5μm. EDX elemental mapping of coating cross-sections indicated that Ni element was depleted from the surface. Pin-on-disc wear tests showed improved wear resistance of NiTi SMA with the (Ti-O-N-Si)/Ti composite coating. Potentiodynamic polarization tests indicated greatly enhanced corrosion resistance of (Ti-O-N-Si)/Ti coated NiTi SMA. The wettability and bioactivity of NiTi SMA with and without the (Ti-O-N-Si)/Ti coating were also evaluated by contact angle measurement and by incubation for two weeks in a simulated body fluid, respectively.
3:45 PM - VV2.5
Localized Corrosion of Surface Treated Porous Nitinol in Different Corrosion Liquid Media.
Chandan Pulletikurthi 2 1 , Norman Munroe 2 1 , Puneet Gill 2 1 , Waseem Haider 2 1 , Smit Pandya 2 1
2 Applied Research Center, Florida International University, Miami, Florida, United States, 1 Materials Science and Engineering, Florida International University, Miami, Florida, United States
Show Abstract Implantable materials are designed to survive in a complex biological medium which consists of a variety of proteins, amino acids, metal and hydrogen ions. As a result, there is always grave concern with regard to the biocompatibility and corrosion resistance of such materials. In this research localized corrosion tests were conducted on surface treated Porous Nitinol (PNT) in osteoblast cell culture medium at 37 °C in order to simulate a bone implant environment. Similar tests were conducted using PBS in order to simulate physiological conditions. Metal ions in each medium after the corrosion tests were measured by ICPMS. A comparative analysis was conducted on the localized corrosion of PNT in each medium.
4:45 PM - VV2.7
Electrochemical Deposition of Apatite/Collagen Composite Coating on NiTi Shape Memory Alloy and Coating Properties.
Tao Sun 1 , Min Wang 1
1 Mechanical Engineering, The University of Hong Kong, Hong Kong China
Show AbstractNiTi shape memory alloys (SMAs) are promising metallic biomaterials for orthopaedic and dental implants. However, in spite of their excellent potential, the safety and reliability of NiTi SMAs in clinical applications are still in controversy, not only because of their bioinertness but also because of the toxic Ni ion release. Therefore, to improve the biocompatibility and bioactivity of NiTi SMAs, many investigations have been conducted on the surface modification of these metals for their intended biomedical applications. Compared to other surface modification techniques, electrochemical deposition, which can form a suitable coating on metal implant surface, is increasingly gaining attention owing to the ease of process control, variability of the coating composition, possibility of protein delivery and suitability for complex implant geometry. In the current study, an apatite/collagen composite coating was formed at 37°C on the NiTi SMA substrate by electrochemical deposition using double strength simulated body fluid (2SBF) which contained dissolved collagen. Surface characteristics, wettability, stability and in vitro bioactivity of the composite coating were subsequently investigated. SEM examination of the surface of composite coatings revealed that many collagen fibers were embedded in flake-like apatite and some apatite nanocrystals nucleated and grew on collagen fibrils. The Ca : P ratio of the composite coating, as was determined by EDX, was about 1.35, which is slightly higher than stoichiometric ratio for octocalcium phosphate (OCP). TEM analysis was conducted for the composite coating. From selected area electron diffraction of the coating, diffraction rings were obtained, indicating apatite in the coating was nanocrystalline or amorphous. These diffraction rings well matched those of OCP. TEM image of the composite coating revealed some small collagen fibrils embedded in the apatite. FTIR results showed the presence of functional groups from both apatite and collagen in the coating. Compared to bare NiTi SMA, the contact angle measurements suggested that wettability of NiTi SMA was improved with the coating formation. The surface energy of bare and as-deposited samples was also calculated according to Owens method. Compared to bare NiTi SMA samples, the potentiodynamic polarization curve of as-deposited NiTi SMA samples displayed lower corrosion current density, more positive corrosion and breakdown potential, suggesting that the composite coating was chemically stable and provided corrosion resistance. The in vitro bioactivity of bare and as-deposited NiTi SMA samples was evaluated by incubating them in the simulated body fluid for up to two weeks.
5:00 PM - VV2.8
Synthesis and Characterization of Biocompatible Potassium Niobate Thin Films.
Jason Stoker 1 , Kunttal Keysher 1 , Ashutosh Tiwari 1
1 Materials Science and Engineering, university of utah, Salt Lake City, Utah, United States
Show AbstractHere we report the synthesis and detailed structural, optical, and electrical characteristics of high-quality biocompatible Potassium Niobate (KNbO3) thin films. Films were grown by pulsed laser deposition (PLD) technique on several technologically important substrates including lanthanum aluminum oxide, LaAlO3 (100), magnesium oxide MgO (100), and niobium doped strontium titanate Nb:STO (100). All the films were found to be of high-purity and exhibiting preferential crystallographic orientation. XRD data showed that KNbO3 films on MgO (100) and Nb:STO (100) have (110) orientation while the films on LaAlO3 (100) substrate possessed (111) orientation. Analysis of EDAX and FTIR data revealed the high phase purity and stoichiometry of the films. Band-gap of the KNbO3 films was found to exhibit a large anisotropy with a band-gap value of 3.85 eV in the <110> direction while a value of 4.12 eV in the <111> direction. Polarization vs Electric field (P-E) measurements performed on KNbO3 films, deposited over conducting Nb:STO substrate, showed hysteretic behavior. From the P-E data the max poarization and the remnant polarization of the film was determined to be 10.7 μC/cm2 and 9.4 μC/cm2, respectively.
5:15 PM - VV2.9
Nano-Structured Alumina-Zirconia Ceramic Matrix Composites for Dental and Orthopaedic Implants.
Ahmad Solomah 1
1 , SAC International , Alexandria Egypt
Show AbstractAlimina-zirconia ceramics are considered potential materials for dental and orthopaedic implants due to their bio-inertness, excellent wear resistance and they are bio-compatible with human body. Nano-structured alumina-zirconia ceramic matrix composites (AZCMC's) were prepared using a proprietary process. The sintered AZCMC's were characterized using XRD, SEM, bending strength and fracture toughnesss. The fracture toughness tests were conducted in a humid and dry atmosphere in order to evaluate the effects of water vapor (H2O) on the crack resistance behaviour of such bio-ceramic materials that are intended for use within the human body. The results will presented and discussed in the light of their applications and performance.
5:30 PM - VV2.10
Bio-Templated Diamond-Based Photonic Band Gap Crystals Operating in the Visible.
Jeremy Galusha 1 , Matthew Jorgensen 1 , Michael Bartl 1
1 Department of Chemistry, University of Utah, Salt Lake City, Utah, United States
Show AbstractBiological systems such as butterflies and beetles have developed highly elaborate exoskeleton photonic crystal lattices to create their striking iridescent coloration. We developed a high-resolution structure analysis technique to three-dimensionally reconstruct biological photonic architectures with previously unachieved resolution, leading to the discovery of novel photonic lattices such as quasi-periodic lattices and the most sought-after diamond-based structures. Since many of these structures and photonic effects are not accessible through artificial synthetic means, create exciting opportunities for bio-templating and bio-mimetic manufacturing routes. We will present sol-gel chemistry-based bio-replication routes for the fabrication of high-dielectric photonic crystals from biological templates. For example, using templates from iridescent beetle scales, we successfully fabricated a diamond-based photonic crystal with a high-dielectric (titanium dioxide) framework. Theoretical studies show that this bio-templated photonic crystal possesses a complete band gap in the visible and are supported by structural and optical studies. In addition, we will discuss new bio-mimetic synthesis strategies to further access and exploit the potential of biological structure engineering for advanced photonic applications.
5:45 PM - VV2.11
Surface Modification of Biomaterials by Phosphonate Based Antibacterial Nanocoatings Releasing Bactericidal Species.
Gilles Guerrero 1 , Julien Amalric 1 , Danielle Laurencin 1 , Hubert Mutin 1 , Arnaud Ponche 2 , Albert Sotto 3 , Jean-Philippe Lavigne 3
1 Chemistry, Institut Charles Gerhardt de Montpellier, CNRS-UM2-ENSCM-UM1, Equipe CMOS, UMR 5253, Montpellier France, 2 , Institut de Chimie des Surfaces et Interfaces, UPR-CNRS 9069, Mulhouse France, 3 , Institut National de la Santé et de la Recherche Médicale, ESPRI 26, Université Montpellier 1, UFR de Médecine, Nîmes France
Show AbstractThe adhesion of bacteria to surfaces and the subsequent development of bacterial biofilms is the cause of a wide variety of chronic and device-related infections, including nosocomial infections, legionellosis, and listeriosis.1 In a biofilm, the bacteria which are trapped inside an exopolysaccharide matrix become remarkably resistant to host defenses and antibiotics. It is thus essential to prevent bacterial adhesion and biofilm formation. Rather than developing new materials, a simple and promising strategy is to modify the surface of a biomaterial with an antimicrobial coating.2Phosphonate coupling agents are good candidates to modify the surface of most inorganic biomaterials (titanium, stainless steel, alumina…). In previous work3, it was shown that they form dense, chemically stable monolayers on inorganic surfaces, and that they strongly bind to the surface through P-O-M bridges.4Here, we present work we carried out on two phosphonate based nanocoatings able to release different bactericidal species :- the silver ion Ag+, which has a broad-spectrum bactericidal activity and a very low toxicity toward mammalian cells. -nitric oxide (NO), which is highly important in human physiological processes , a powerful bactericid, and also active in biofilm dispersion.5The formation of phosphonate monolayers functionalized by silver thiolate6 or NO donor groups on titanium or stainless steel will be presented. The coatings were characterized using X-Ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy in grazing-incidence mode and water contact angle measurements. In vitro bacterial adhesion and biofilm assays on these antibacterial nanocoatings with different clinical strains (E. coli, S. aureus,…) demonstrate the strong antibacterial activity of these monolayers despite the extremely low content of antibacterial species.1J. W. Costerton, L. Montanaro and C. R. Arciola, Int. J. Artif. Organs, 2005, 28, 1062.2.D. Campoccia, L. Montanaro and C. R. Arciola, Biomater., 2006, 27, 2331.3.P. H. Mutin, G. Guerrero and A. Vioux, J. Mater. Chem., 2005, 15, 3761.4.F. Brodard-Severac, G. Guerrero, J. Maquet, P. Florian, C. Gervais and P. H. Mutin, Chem Mater., 2008, 20, 5191.5.E. M. Hetrick, J. H. Shin, H. S. Paul and M. H. Schoenfisch, Biomaterials, 2009, 30, 27826.J. Amalric, P. H. Mutin, G. Guerrero, A. Ponche, A. Sotto and J.-P. Lavigne, J. Mater. Chem., 2009, 19, 141.
Symposium Organizers
Roger Narayan University of North Carolina
Suwan Jayasinghe University College London
Sungho Jin University of California-San Diego
William Mullins Office of Naval Research
Donglu Shi University of Cincinnati
VV3: Properties of Biological and Bioinspired Materials
Session Chairs
Sungho Jin
Robert Ritchie
Wednesday AM, December 02, 2009
Room 202 (Hynes)
9:00 AM - **VV3.1
Damage Tolerance in Biomaterials.
Subra Suresh 1
1 School of Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractA variety of useful design approaches and strategies can be extracted from the manner in which natural biological materials respond to mechanical and thermal environments to protect against the onset and progression of damage and failure. Specifically, the design of layered structures as well as optimal spatial gradations in composition, microstructure and physical properties offers insights for possible means to suppress damage evolution during contact loading, impact, penetration, subcritical crack growth, fatigue and thermal shock. This presentation will provide an overview of our work on layered and compositionally graded materials wherein particular strategies for developing damage-resistant engineered surfaces are developed by recourse to systematic experiments and detailed computational simulations. Particular attention will be devoted to damage suppression under normal and frictional-sliding contact as well as impact, thermal and fatigue loading of engineered articulating surfaces with structural design concepts learned from a broad spectrum of natural biomaterials.
9:30 AM - **VV3.2
Ice-templated Bio-inspired Structural Materials by Manipulation of Structure at Multiple Length-scales.
Robert Ritchie 1 2 , Antoni Tomsia 2 , Eduardo Saiz 2 , M. Launey 2 , Etienne Munch 2 , Daan Hein Alsem 2
1 MSE, UC Berkeley, Berkeley, California, United States, 2 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractThe structure of materials invariably defines their mechanical behavior. However, in most materials, specific mechanical properties are controlled by structure at widely differing length scales. Nowhere is this more apparent than with biological materials, which are invariably sophisticated composites whose unique combination of mechanical properties derives from an architectural design that spans nanoscale to macroscopic dimensions with precisely and carefully engineered interfaces. The fracture resistance of such materials originates from toughening mechanisms at almost every one of these dimensions. Few structural engineering materials have such a hierarchy of structure, yet the message from biology is clear – unique mechanical properties can be achieved through the combination of mechanisms acting at multiple length-scales. Nature has successfully used this approach over billions of years, yet despite intense interest by the scientific community, the biomemitic approach has yielded few real technological advances in the design of new synthetic structural materials primarily due to the fact that such materials are difficult to fabricate and that we still lack a complete understanding of how diverse structural features acting at multiple length scales (from the atomic to the macro level) interact to generate unique toughening mechanisms. Indeed, natural composites achieve strength and toughness through complex hierarchical designs which are almost impossible to replicate synthetically. Here we attempt to emulate Nature’s toughening mechanisms using a freeze-casting fabrication process to make materials through the combination of two ordinary compounds, specifically alumina and PMMA, into ice-templated structures whose toughness can be over 300 times (in energy terms) that of their constituents. The final products are bulk lightweight hybrid ceramic-based materials whose high strength and fracture toughness (~200 MPa and >30 MPa√m) provide specific properties comparable to metallic aluminum alloys. These materials are probably the toughest ceramics ever produced, but must be made through careful control of structural size-scales at nano to macro-scales. They are unlike regular composites in that both phases are not load-bearing; the ceramic phase provides for strength but the polymer phase acts like a lubricant to relieve high stresses, much like plasticity in metals. We believe that these model materials can be used to identify the key microstructural features that should guide the synthesis of more advanced bio-inspired lightweight structural materials with unprecedented combinations of strength and toughness.
10:00 AM - VV3.3
Further insight in nanostructured bio-inspired materials by solid state Nuclear Magnetic Resonance.
Christian Bonhomme 1 , Christel Gervais 1 , Florence Babonneau 1 , Guilhem Arrachart 2 , Michel Wong Chi Man 2
1 , universite P et M Curie, Paris France, 2 , Institut Charles Gerhardt ICG, Montpellier France
Show AbstractThe field of bio-inspired nanomaterials is exploding. Complex hybrid materials are generally involved, exhibiting interfaces, which play a major role towards the final chemical and biological properties. At this stage, we can raise the following central question: "is it actually possible to fully describe the hybrid organic/inorganic interfaces in terms of safe chemical and structural characterizations?As a matter of fact, solid state Nuclear Magnetic Resonance (NMR) – and its latest experimental, instrumental and theoretical developments – appears as a remarkable tool of investigation for hybrid materials and interfaces [1-2]. The aim of this communication is to highlight the newest applications of solid state NMR in the field of bio-inspired materials.Very recently, we have proposed new syntheses of hybrid silicas based on molecular recognition through H-bonding. Homo-association of silylated ureidopyrimidinone (UPY) entities, followed by standard hydrolysis and condensation sol-gel reactions, led to nanostructured silica derivatives [3]. The key characterization of the H-bond networks was based on advanced 1H double quantum dipolar recoupling techniques allowing for the detailed description of proton connectivities in the crystalline precursors (silyl-UPY), as well as in the amorphous final materials. The approach was successfully extended to Adenine (A) and Thymine (T) silylated derivatives. Homo-associations (A/A and T/T), as well as hetero-association (A/T), were clearly evidenced by high resolution 1H NMR [4].In this communication, strong emphasis will be made on the latest methodological aspects of 1H solid state NMR: very high field NMR (700 MHz), ultra-fast MAS experiments (up to 70 kHz), recoupling of NMR interactions under high resolution conditions. All these methods open new routes for the characterization of biomaterials, as they should lead to ultimate spectral resolution. Therefore, there is an urgent need for deep understanding of the corresponding spectra and for safe structural assignments. We have shown recently that ab initio calculated 1H NMR data could be obtained with great accuracy by using the DFT based GIPAW (Gauge Included Projected Augmented Wave) method (Pickard and Mauri, 2001). It has been shown that the calculated 1H chemical shifts were strongly related to geometrical features of the H-bond networks [5-6].The "experimental NMR / ab initio NMR" combined approach seems valuable for the clear description of H-bonds at the interface of biomaterials interacting with proteins or other biological species.[1] C. Bonhomme et al. Accounts Chem. Res., 40 (2007) 738 [2] N. Baccile et al. Chem. Mater., 19 (2007) 1343 [3] G. Arrachart et al., Chem. Eur. J., 15 (2009) 5002 [4] G. Arrachart et al., J. Mater. Chem., 18 (2008) 392 [5] F. Pourpoint et al., Appl. Magn. Res., 32 (2007) 435.[6] G. Gervais et al., J. Magn. Reson., 187 (2007) 131.
10:15 AM - VV3.4
Controlled Peptide-mediated Formation of Hybrid Metallic Nanostructures.
Marketa Hnilova 1 , Hanson Fong 1 , Christopher So 1 , Turgay Kacar 1 2 , Candan Tarmerler 1 2 , Mehmet Sarikaya 1 2
1 Departmentof Material Science and Engineering, University of Washington, Seattle, Washington, United States, 2 Department of Molecular Biology and Genetics and MOBGAM, Istanbul Technical University, Istanbul Turkey
Show AbstractOne of the major challenges in nanotechnology research is the development of procedures by which to form metallic nanostructures of controllable and tunable sizes that are also bio-compatible for bionanotechnological applications. Syntheses of metallic nanostructures mediated by combinatorially selected peptides and carried out at ambient conditions are potentially appealing as environmental- and bio-friendly alternatives to conventional chemical methods. Recently, we reported the identification and characterization of two 12 AA peptide sequences (AuBPs) from combinatorial peptide library that interact with gold surfaces with high affinity. In this report we specifically probe AuBP-mediated gold crystal growth morphologies and kinetics in solution. The AuBP sequences were initially produced in both the linear (l-AuBPs) and cyclic forms (c-AuBPs) to determine the effects of amino acid compositions and molecular architectural constraints on their catalytic activities. Here, we find that both l- and c-versions of the AuBP sequences do catalyze gold crystal formation in aqueous solution under ambient resulting in the formation of stable and dispersed peptide-capped gold nanoparticles in a single-step reaction. The observed difference in peptide-mediated kinetics and resulting nanoparticle morphologies may be attributed to the various peptide architectures and folding properties that might affect the accessibility of the functional side groups and molecular recognition during the interaction of gold reduction and formation. The molecular architecture may also affect capping capabilities of the peptides on the gold nanoparticle affecting its aggregation/dispersion characteristics. In this study, we used two gold binding sequences, and systematically varied molecular architecture (I- versus c-), au-ion versus peptide concentrations and reaction conditions. The peptide-based biomimetic approaches of the synthesis metallic nanostructures described here have implications in a wide range of potential practical applications such as controlled bottom-up assembly of hybrid nanostructures, nanobiophotonic, and biosensing platforms. Research is supported by GEMSEC, an NSF-MRSEC, NSF-BioMat, and NSF-IRES Programs at the University of Washington GEMSEC.
10:30 AM - VV3.5
Threat-protection Response of Natural Exoskeletons.
Juha Song 1 , Mary Boyce 2 , Christine Ortiz 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractIt is hypothesized that the functional design of biological exoskeletons are intimately linked to their corresponding environmental and predatory threats (e.g. biting teeth, bird beaks, the crushing, peeling, and cutting claws of crabs, etc.) through the evolutionary process. During a predatory attack, the natural armor, as well as the attack structure, will undergo complex multiaxial deformations since generally both have mechanical properties that are comparable. The nature, interaction, and coupling between the armor and threat stress and strain fields are critical to the understanding the functional design specificity of the armor in achieving sufficient protection and maximizing survivability of the animal. In this study, we investigate this topic using a model system, the fish Polypterus senegalus, which has an exoskeleton composed of highly mineralized scales. The primary predators of P. senegalus are known to be its own species or its carnivorous vertebrate relatives and biting take place during both territorial fighting and feeding. Finite element analysis models of the geometry, multilayered structure, and mechanical properties of both the scale and tooth were constructed and a virtual penetrating biting event simulated on loading and unloading. For the tooth model, optical microscopy images of P. senegalus teeth showed conical geometry with an averaged end-radius of ~15 µm (ranging from ~ 3 µm to ~ 44 µm) and two material layers; a cone of dentin capped by an outer layer of enameloid. The scale of P. senegalus was modeled as quad-layered in accord with its known structure (ganoine, dentin, isopedine, and bone). The elastic and plastic mechanical properties of both the tooth and scale individual material layers utilized in the simulations were quantified experimentally via instrumented indentation. Since the mechanical properties of the threat and armor were comparable, deformation occurred simultaneously in both structures. A higher stress concentration and greater degree of deformation occurred in the tooth compared to the armor, due to the higher curvature compared to the armor. Plasticity took place primarily in the softer underlying dentin layer of the tooth. Deformable and relatively sharp indenters, e.g. the fish tooth, significantly reduce the critical stress fields and plastic deformation inside the armor compared to theoretically rigid indenters. Parametric studies show that smaller end-radius and a thinner enamel layer of the tooth led to larger plastic deformation of the tooth dentin and smaller penetration depth into the scale. These results are consistent with the concept of evolutionary-driven "length-scale matching" between the protective structure its corresponding threat, which can be traced back to "Darwin's finches" whereby the size scale of their beaks (for approximately the same size birds) were adapted to the size scale of the food sources (e.g. seeds).
10:45 AM - VV3.6
Bioinspired Design of Multilayers: Effect of Layer Thickness.
Jing Du 1 , Xinrui Niu 1 , Nima Rahbar 2 , Wole Soboyejo 1
1 Princeton Institute of Science and Technology of Materials (PRISM) and the Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States, 2 Department of Civil Engineering, University of Massachusetts Dartmouth, North Dartmouth, Massachusetts, United States
Show AbstractThis paper examines the effects of layer thickness on the design of bioinspired dental multilayers that are processed from micronscale nanocomposite layers. The static stress states in the dental multilayers are considered for structures with different layer thicknesses. These are modeled under Hertzian contact loading using the finite element methods. Thicker multilayered structures are shown to have much lower stress concentrations. The models are validated using experiments on layered structures that are fabricated from nanocomposite layers that mimic the linear functionally graded structure of the dentin-enamel-junction in natural teeth. Experimental measurements of creep data are also incorporated into a modified rate dependent slow crack growth model for the prediction of crack growth. The predictions of failure loads are shown to be consistent with measurements of critical loads at different loading rates.
11:00 AM - VV3: Properties
Break
11:15 AM - VV3.7
On Mechanics of Connective Tissues.
Hamed Hatami-Marbini 1 , Peter Pinsky 1
1 Department of Mechanical Engineering, Stanford University, Stanford, California, United States
Show AbstractThe extracellular matrix plays a crucial role in defining the mechanical properties of connective tissues like cornea, heart, tendon, bone and cartilage among many others. The unique properties of these collagenous tissues arise because of both the hierarchal structure of collagens and the presence of negatively charged proteoglycans (PGs) which bind collagen fibers together. Here, in an effort to understand the mechanics of these structures, we first study the nanomechanics of collagen molecules and PG glycosminoglycans (GAGs) using molecular dynamics simulation. The results of these studies are used to develop a simple continuum model describing the tissue elasticity at the macro-scale. We focus on tendon and cornea since their morphology is known in great detail due to recent advances in imaging technology. The current study shows that the PGs have an important role in distributing the external force between collagen fibers and their effect cannot be neglected. It also sheds light on the origins of the unique mechanical properties of connective tissue and provides useful results for developing new biomaterials.
12:00 PM - **VV3.9
Hierarchical Self-Assembly of Biomaterials.
Samuel Stupp 1
1 , Northwestern University, Evanston, Illinois, United States
Show AbstractSelf-Assembly is of great interest as a tool to create biomaterials since it offers pathways for the in situ noninvasive transformation of dissolved into solid therapeutic structures in vivo. Self-assembly can also offer extremely rapid processes to generate bioactive materials using modular strategies, or processes that are compatible with living cells in the preparation of therapeutic constructs. In this lecture self-assembly pathways developed in our laboratory are reviewed for supramolecular materials using designed molecules with the capacity to signal cell receptors. One of the self-assembly pathways to be described generates a large diversity of bioactive nanostructures that can be used to co-assemble signals in order to regenerate organs and tissues. A second system to be described involves the self-assembly of polymers and small molecules into hierarchical structures that form bioactive membranes and cell containers, or artificial cells by self-assembly processes on the scale of milliseconds. A third system to be described involves the "pipetting" of monodomain gels that can serve as cell conduits.
12:30 PM - **VV3.10
Molecular Mechanism of Brushite Crystallization.
Jennifer Giocondi 1 , George Nancollas 2 , Christine Orme 1
1 Physical and Life Sciences, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 , University of Buffalo, SUNY, Buffalo, New York, United States
Show AbstractThe biomineral, calcium hydrogen phosphate dihydrate (CaHPO4 ● 2H2O), known as brushite, is a malleable material that both grows and dissolves readily. Compared to the other calcium phosphate (CaP) phases, it has a comparatively fast nucleation rate as a result of its low surface energy. Similarly its faster dissolution rate results from its comparatively high solubility at physiological pH. Within the body these properties can play a role in certain diseases, most notably in kidney stone formation where crystals form under mildly acidic conditions found in urine. However, these same properties, along with brushite’s excellent biocompatibility, can be used to great benefit in making resorbable biomedical cements. To optimize cements, additives are commonly used to control crystallization kinetics and phase transformation. This talk describes the use of in situ SPM to investigate the role of several solution parameters and additives, on brushite atomic step motion. Surprisingly, this work demonstrates that the activation barrier for phosphate (rather than calcium) incorporation limits growth kinetics, and that, additives such as magnesium, citrate and bisphosphonates each influence step motion in distinctly different ways. Our findings provide details of how, and where, molecules inhibit or accelerate kinetics. These insights have the potential to aid in designing molecules to target specific steps and to guide synergistic combinations of additives.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE - AC52 - 07NA27344. Portions of this work were supported by the National Institutes of Health (NIDCR DE03223).
VV4: Medical Applications of Nanomaterials
Session Chairs
Suwan Jaysinghe
Donglu Shi
Wednesday PM, December 02, 2009
Room 202 (Hynes)
2:30 PM - VV4.1
In Vivo Imaging and Drug Storage via Multifunctional Fluorescent Superparamagnetic Nanoparticles.
Donglu Shi 1 , Hoon Sung Cho 1 , Chris Huth 1 , Feng Wang 1 , Giovanni Pauletti 1 , Xu Hong 2 , Hongchen Gu 2
1 Chemical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio, United States, 2 Med-X, Shanghai Jiao Tong University, Shanghai China
Show AbstractThere is an increasing need for early detection and treatment of cancer prior to the tumor mass becoming evident as anatomical anomaly. A major challenge in cancer diagnosis is to distinguish cancer cells from the surrounding, healthy tissue. In addition, there is a need for new approaches that maximize therapeutic benefit, improve tumor targeting, and provide localized intervention. One promising strategy for overcoming current limitations in cancer diagnostic and tumor therapy is to make use of highly luminescent nanoparticles for qualitative or quantitative in vitro detection of tumor cells. However, an optimum nanostructure has yet to be developed that simultaneously offers multiple functionalities, including intensive fluorescence, effective drug storage capability, and therapeutic efficacy. With the development of such nanostructures, it will be possible to initiate cancer treatment earlier and limit exposure of chemotherapeutic agents to defined tumor areas. We present a novel approach to design a fluorescent superparamagnetic system by depositing various nano-phosphors, such as quantum dots, onto the surfaces of composite Fe3O4-polystyrene nanospheres. Fluorescent spectrometer measurements confirm that the surface-functionalized nanospheres exhibit luminescence in the visible light range. Images obtained from the first in vivo administration of nanospheres in live mice support further evaluation of this novel composite as an innovative, multifunctional nanodevice for biomedical applications. The unique combination of fluorescence emission and hyperthermia capability engineered into these nanospheres is anticipated to find clinical applications in early cancer diagnosis and tumor treatment.
2:45 PM - VV4.2
Biocompatible Iron/Iron Oxide Core/Shell Nanoparticles for Magnetic Hyperthermia.
Ian Baker 1 , Gaundong Zhang 1 3 , Qianglong Zeng 1 , Yifeng Liao 1 , Shiraz Cassim 1 , John Weaver 2 , P. Hoopes 2
1 Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, United States, 3 Bioengineering Department, Belknap Campus, University of Louisville, Louisville , Kentucky, United States, 2 Dartmouth Medical School, Dartmouth College, Hanover, New Hampshire, United States
Show AbstractIn this presentation, we will compare the structure, magnetic properties and heating behavior of Fe/Fe oxide core/shell composite nanoparticles to that of dextran-coated iron oxide nanoparticles. The Fe/Fe oxide nanoparticles utilized the fact that the high saturation magnetization of an iron core (120-190 emu/g, which is twice that of iron oxide) could give a greater heating effect than iron oxide nanoparticles, while the iron oxide coating will allow the nanoparticles to be observed using magnetic resonance imaging so that therapy can be effectively monitored. The nanoparticles were synthesized from microemulsions of NaBH4 and FeCl3, followed by surface modification in which a thin hydrophobic hexamethyldisilazane layer replaced the surfactant coating on the particles. Phosphatidylcholine was then assembled onto the nanoparticle surface. Supported by NIST Grant 60NANB200120, the Nanocancer Working Group at Dartmouth and the Norris Cotton Cancer Center Prouty Pilot Project Program.
3:00 PM - **VV4.3
Theragnostics and Nanotoxicity of Magnetic Nanoparticles.
Veronica Shubayev 1
1 Anesthesiology, School of Medicine and VA Healthcare System, University of California at San Diego, La Jolla, California, United States
Show AbstractEngineered biomaterials such as magnetic nanoparticles (MNPs) provide a basis for cutting-edge targeted diagnostic and therapeutic platforms due to their ability to be simultaneously guided by a magnetic field and bioactive molecules conjugated to their surface. Recent advances in the design of MNPs have advanced several biomedical applications to molecular sensitivities, including magnetic resonance imaging, drug and gene delivery, cell sorting and tissue engineering. Mounting evidence suggests that the enhanced reactive area, ability to cross cell and tissues barriers and resistance to biodegradation of nano-sized particles amplify their cytotoxic potential relative to molecular or bulk counterparts, implicating oxidative stress (OS) as a key paradigm of nanotoxicity. A 3-tier process, OS manifests in activation of reactive oxygen species (ROS) and antioxidant defense system (tier I), followed by a pro-inflammatory response (tier II) and DNA damage leading to apoptosis and mutagenesis (tier III). Upon their in vivo administration, MNPs are quickly challenged by macrophages of the reticuloendothelial system (RES), which buffer potential MNP toxicity but reduce their circulation time for therapeutic and diagnostic platforms. While therapeutic strategies of localized cytotoxicity, such as tumor targeting and macrophage-suicide approaches are exciting, potentially toxic implications for MNP overload to healthy tissues should be considered, and a rising chorus of government, industry, academia and environmentalists is calling for studies on toxicity of nanoparticles. As the demand for nanotoxicity assessment increases, clinical relevance and mechanistic approaches should be prioritized. The coalescence of engineering and biomedical applications together with toxicology disciplines will foster development of relevant strategies to engineer advanced biomaterials such as magnetic nanoparticles. This talk will review current studies on some potential MNP applications, toxicity and relevant methods of nanotoxicity assessments, and analyze the engineering strategies employed to optimize MNPs for use in biomedical applications. The role of MNP size, composition and surface chemistry in regulating their intracellular uptake, in vivo biodistribution, macrophage recognition and cytotoxic changes will also be described.
3:30 PM - VV4.4
Superparamagnetic Maghemite Nanoparticles for Diverse Biomedical Applications: Effective Parameters on Their Characteristics.
Ozge Baltaci 1 , Ahmet Ozenbas 1
1 Metallurgical and Materials Engineering, Middle East Technical University, Ankara Turkey
Show AbstractMaghemite (γ-Fe2O3) nanoparticles are used extensively in the field of biomagnetics for a broad range of applications, such as drug delivery, cell separation, magnetic resonance imaging, sensing and therapeutic applications. All these biomedical applications require that the nanoparticles are superparamagnetic with sizes smaller than 20 nm with narrowsize distribution to have uniform physical and chemical properties. Main purpose of this study was the production of these nanoparticles by a typical method which will allow us to obtain maghemite phase in desired properties. To achieve this purpose two different processing techniques were employed; Sol-Gel Processing and Microwave Synthesis. In the Sol-Gel method different starting materials such as ethylene and diethylene glycol were used. Peak intensities showed that crystallinity of the samples (maghemite phase) was higher than the samples which were prepared by microwave synthesis. Approximate particle sizes were calculated between 4 and 48 nm using Scherrer equation. Also from the XRD results amounts of the maghemite phase were estimated as 77.5, 30 and 28.7 for the samples heated at 300, 350 and 4000C, respectively. Vibrating Sample Magnetometer (VSM) results indicated superparamagnetic behavior of the samples.Magnetization curves were fitted by using Langevin function, tangent hyperbolic and linear terms for superparamagnetic, ferromagnetic and paramagnetic parts, respectively. Occurrence of hematite phase in these samples do not disturb the superparamagnetic behavior but the increase of the amount of hematite caused a decrease in the saturation magnetization (Ms) values.It is considered that microwave method, second technique used to produce maghemite nanoparticles, is easy and efficient way to produce maghemite nanoparticles. For this study different microwave powers and durations were used in the range of 630 and 900 W. Approximate particle sizes were found between 2.6 and 24.6 nm from the XRD results. According to TEM studies, it can be concluded that the theoretical and measured interplanar spacings were matched with maghemite phase. From the magnetic measurement (VSM) results some samples which were produced at 850 W, showed superparamagnetic behavior, on the other hand other samples behaved paramagnetically at room temperature.In summary two different production methods were used to synthesize superparamagnetic maghemite nanoparticles. Both of the methods are efficient ways of obtaining superparamagnetic nanoparticles. But in the microwave procedure it is considered that microwave irradiation may not be fully effective in the oven so that only some of the samples have desired maghemite phase with superparamagnetic behavior under the experimental conditions used in this study.
3:45 PM - VV4.5
Multivalent Peptide Display on Model Engineered Nanoparticles (Virus-Like Particles and Silica Nanoparticle-Supported Lipid Bilayers) Facilitates Highly Specific Targeted Delivery of Diagnostic and Therapeutic Agents to Human Cancer Cells.
Carlee Ashley 1 , Juewen Liu 1 , David Peabody 2 , C. Jeffrey Brinker 1 2 3
1 Chemical Engineering, University of New Mexico, Albuquerque, New Mexico, United States, 2 Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, New Mexico, United States, 3 Self-Assembled Materials, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractOur research focuses on controlling the biophysical and biochemical properties of engineered nanoparticles to achieve highly specific delivery of diagnostic and therapeutic agents to human cancer cells without affecting the viability of other cells and tissues. We have developed two model nanoscale systems for targeted delivery applications: protocells and virus-like particles (VLPs) of MS2 bacteriophage. Protocells are porous silica nanoparticle-supported lipid bilayers that take advantage of the low toxicity and immunogenicity of liposomes, along with their ability to be modified with PEG to extend circulation times and with various ligands to effect targeting. The protocell is more stable than liposomes, however, and the nanoporous core enables precise control of cargo loading efficiencies and release rates. MS2 VLPs self-assemble from 180 copies of a single coat protein into 28-nm monodisperse capsids that are highly tolerant of high density peptide display. We are, therefore, developing MS2 VLPs as an integrated platform for both targeted delivery and random peptide display, enabling selection of high affinity targeting peptides from a complex library (1010-1012 using in vitro techniques) in a process analogous to phage display. We have demonstrated, using a peptide identified to have an affinity for human hepatocarcinoma via phage display, that targeted protocells and VLPs have a nanomolar affinity for Hep3B and HepG2; high specificity is achieved through multivalent display of the targeting ligand (~240 peptides per protocell or VLP). Experiments employing lipids with a range of melting points suggest that the fluidity of the protocell’s supported bilayer promotes ligand recruitment to the target cell surface and enables highly selective targeting at low peptide densities. Targeted protocells and VLPs are rapidly endocytosed by Hep3B and HepG2 but show minimal surface binding and absolutely no internalization by hepatocytes, HUVECs, T- and B-lymphocytes, and macrophages. We have demonstrated selective delivery of various nanoparticles (gold NPs, iron oxide NPs, and quantum dots), chemotherapeutic agents (doxorubicin, camptothecin, and sorafenib), siRNA that silences the expression of various proteins (e.g. cyclin B1, COX-2, VEGF, etc.), and protein toxins (ricin A chain, cholera toxin, and diphtheria toxin) to hepatocarcinoma using targeted protocells and VLPs. We have, furthermore, incorporated histidine-rich peptides within targeted protocells and VLPs to facilitate endosomal disruption and have modified cargo with nuclear localization sequences to further enhance the effect of therapeutic agents on their intracellular targets. We propose that both protocells and VLPs can contribute to the emerging field of theranostics, enabling the combined delivery of diagnostic and therapeutic agents to cancer cells with unprecedented specificity.
4:00 PM - VV4: Medical
BREAK
4:15 PM - VV4.6
Size-Controllable Nanoparticles Prepared by A Supramolecular Approach.
Kuan-Ju Chen 1 , Hao Wang 1 , Shutao Wang 1 , Helen Su 1 , Amanda Armijo 1 , Wei-Yu Lin 1 , Yanju Wang 1 , Jing Sun 1 , Ken-ichiro Kamei 1 , Hsian-Rong Tseng 1
1 Department of Molecular and Medical Pharmacology, UCLA, Los Angeles, California, United States
Show AbstractA supramolecular approach has been developed for the preparation of supramolecular nanoparticles(SNPs) with variable sizes from three different molecular building blocks 1)Adamantane-grafted first-generation polyamidoamine dendrimer,n-Ad-PAMAM, 2)b-cyclodextrin-grafted branched polyethylenimine,CD-PEI, and 3)Ad-functionalized PEG compound,Ad-PEG, by using a CD/Ad recognition system. The uniqueness of our design is the use of a capping/solvation group. This solvation group Ad-PEG competes with the dendrimer building block to constrain the continuous propagation of the cross-linked network, and on the other hand confers water solubility to the SNPs. By tuning mixing ratios among the three molecular building blocks in PBS aqueous buffer solution, the equilibrium between the propagation/aggregation and capping/solvation of the cross-linked network fragments can be altered, allowing arbitrary control over the sizes of the water-soluble SNPs.Further studies were carried out to unveil the unique properties of these SNPs, including 1)their stability at different temperatures and pH values, as well as in physiological ionic strength media, 2)their competitive disassembly in the presence of Ad molecules, and 3)reversible control over the size using in situ alteration of the mixing ratios of the molecular building blocks. Finally, Positron Emission Tomography (PET) was employed to study the biodistribution and lymph node drainage of the SNPs in mice. MicroPET/CT studies suggested that the biodistribution patterns of the 30 and 100 nm SNPs were quite similar. In both cases, rapid blood clearance through liver accumulation of the SNPs was observed. Moreover, the terminal elimination half-lives were also quite different. Together, the results indicated that the in vivo clearance of the 30 nm SNPs is faster than that of the 100 nm SNPs. To explore the use of the SNPs for immune modulation, we investigated the lymph node trafficking of both 30 and 100 nm 64Cu-labeled SNPs by using front footpad injection. We observed the 30 nm SNPs drained into the local auxiliary lymph node and peaked at 5 minutes post injection. On the other hand, there is no significant accumulation was detected in the lymph nodes where the 100 nm SNPs were injected.In conclusion, we have successfully developed a convenient, flexible, and modular synthetic approach for the preparation of size-controllable SNPs. PET imaging studies were carried out by injecting 64Cu-labeled SNPs of different sizes into mice. Both whole-body biodistribution and lymph node drainage studies showed that the sizes of the SNPs affect their in vivo characteristics. Besides the imaging studies shown herein, we are currently exploring the use of the size controllable SNPs for other biomedical applications. References: 1)M.E.Davis,Z.G.Chen,D.M.Shin, Nat.Rev.Drug Discovery.2008,7,771.2)Y.W.Jun,J.H.Lee,J.Cheon,Angew.Chem.2008,120,5200.3)Hao Wang¥,Shutao Wang¥,Helen Su¥,Kuan-Ju Chen et al,Angew.Chem.Int.Ed.2009,48,4344
4:30 PM - VV4.7
Anchor Nanoparticles on Tumoritropic Stem Cell Membrane: A New Way for Delivery.
Hao Cheng 1 2 , Renuka Ramanathan 3 , Minglin Ma 2 , Qiaobing Xu 1 2 , Robert Langer 1 2 , Daniel Anderson 2
1 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 The David H. Koch Institute for Integrative Cancer Research , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractNanostructures have been emerged as a promising modality to deliver therapeutics for cancer therapy. However, majority of nanostructures are cleared during circulation and cannot reach tumors even after the optimization in size, shape, flexibility and surface properties. Drug delivery vehicles, which can sense positions of tumors and are not cleared by human bodies before reaching tumors, will be more promising for cancer targeting. Some types of stem cells have tumoritropic migratory properties and have been utilized in the study of cancer therapies by genetically engineering stem cells to express tumor suppressive proteins or metabolic products. We reported a strategy to attach nanostructures asymmetrically on cell membrane, utilizing the binding between biotin and avidin. Substantial amount of 40nm nanoparticles still anchored on human bone marrow derived mesenchymal stem cell (hMSC) membrane 2 days after attachment. Nanoparticles on hMSC membrane did not affect the ability of cells to respond to tumor spheroid in 3D collagen gels. This technique may have broad applications because it circumvents the step of viral infection and has the potential to load many types of therapeutics rather than cell producing drugs.
4:45 PM - VV4.8
Multifunctional Linear-Dendritic Block Copolymers for Gene Delivery.
Daniel Bonner 1 2 , Kris Wood 2 , Alan Leung 2 , Jane Chen-Liang 2 , Robert Langer 2 , Paula Hammond 2
1 Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractNucleic acid therapies offer the promise to address unmet medical need in cancer, inherited genetic disorders, and vaccine development, but delivery of DNA to appropriate tissues is not yet clinically viable. DNA can be delivered via viral vectors with excellent efficiency, but this technique raises safety concerns and the possibility of immune rejection. Synthetic systems, generally polymer or lipid-based, have suffered from low transfection efficiency but are largely safe and biocompatible, though only transient gene expression is gained. We have developed a modular, linear-dendritic block copolymer gene delivery system capable of transfecting a range of cell lines in vitro at efficiencies on par with standard commercially available non-viral vectors. Here, we evaluate the functional consequences of chemical structure modifications within the linear-dendritic architecture using confocal microscopy to quantitate material performance with respect to intracellular barriers to gene delivery. Rather than taking gene expression as the sole endpoint of material performance, understanding relative efficiencies among various intracellular transport processes can shed light on important structure-property relationships.
5:00 PM - VV4.9
Self-Assembled PEG Hydrogel Particles to Control Bacteria-Biomaterial Interactions.
Qichen Wang 1 , Matthew Libera 1
1 Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, New Jersey, United States
Show AbstractWe are using polymeric nano/micro hydrogel particles self assembled on solid surfaces to control the interactions of those surfaces with physiological systems. We are particularly interested in modifying surfaces to control their interactions with staphylococcal bacteria with the long-term goal of reducing biomaterials-related infection. This particular work concentrates on the emulsion polymerization and subsequent surface self assembly of PEG-based [poly(ethylene glycol)] gel particles with diameters ranging from approximately 50 – 500 nm. PEG-based gels have been widely studied in various forms and in various ways to render surfaces resistant to protein adsorption and cell adhesion, and our work exploits these antifouling properties. We copolymerized PEG diacrylate (PEGDA) with acrylic acid (AA) dissolved in dichloromethane and dispersed as an emulsion in water. Our initial experiments have avoided surfactants. The acrylic acid provides charged groups that facilitate electrostatic self-assembly as well as sites for post-polymerization chemical functionalization. Zeta-potential and light-scattering measurements indicate that the AA-containing gel particles display pH-dependent charge and swelling behavior whereas pure PEGDA gels do not. Bulk gels with similar compositions indicate that the pH-dependent swell ratios (hydrated mass/dry mass) change from ~5 at pH below about 6 to over 12 for pH above about 7. After purification and filtration, gel particles were deposited on poly-l-lysine (PLL) -coated silicon substrates from buffer solutions at pH 7.4. The quantity of gel particles deposited and their spatial distribution on the surface was varied based on the concentration of gels in solution, the pH, and the deposition time. We concentrated on surfaces with extremes of high (~2-3 gel particles/sq. micron) and low (~0.5-1 particle/sq. micron) particle coverage, and we compared the response of Staphylococcus epidermidis (S. epi) adhesion and proliferation on these surfaces to that on unmodified silicon, PLL-coated silicon, and pure PEGDA bulk gel. Bacteria do not adhere to the bulk gel, but they do adhere and grow prolifically on silicon and PLL-treated silicon. While bacteria still adhere and proliferate on the gel-modified surfaces, the surface density of adherent bacteria and their rate of growth are significantly lowered relative to the silicon and PLL-treated silicon surfaces. Increasing the surface density of gel particles from the low-coverage to high-coverage condition also decreases the S. epi adhesion and proliferation rates. This finding suggests that otherwise cell-adhesive surfaces with a surface distribution of nano/microscale cell-repulsive features may be useful in reducing the susceptibility of biomedical devices to bacterial infection.
5:15 PM - VV4.10
Development of Polymeric Nanoconjugates for Cancer Treatment.
Rong Tong 1 , Jianjun Cheng 1
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractPolymeric nanoparticles are promising carriers for the delivery of chemotherapeutics for cancer therapy because they are able to carry large payload of therapeutic modality, extravasate leaky tumor vasculature, and mediate sustained drug release in tumor tissues. Of a handful of nanoparticulate carriers being studied, polymeric nanoencapsulates are particularly promising because they can be readily prepared through the co-precipitation of hydrophobic polymers and small molecule drugs in a process called nanoprecipitation. However, nanoencapsulates typically have significant drug burst release, low drug loading and uncontrollable drug encapsulation efficiency. To address these issues, we developed nanoconjugation technique to allow successful formulations of sub-100 nm sized, mono-modal nanoconjugates with definable drug loading, quantitative drug loading efficiency and controlled release profiles. Nanoconjugates were prepared through a drug-initiated ring opening polymerization followed by nanoprecipitation. In the first step, hydroxyl-containing therapeutic agents are used as initiators to initiate living polymerization of cyclic ester monomers (e.g., lactide), and result in polyester-therapeutics conjugates. In the second step, precipitation of the polyester-therapeutics conjugates gives the desired polyester-drug nanoconjugates. Using paclitaxel as a model drug, we have been able to formulate paclitaxel-polylactide nanoconjugates with 100% drug incorporation efficiency and up to 37% drug loading. These new nanoparticles are promising delivery vehicles for targeted cancer therapy with improved efficacy and reduced toxicity.
5:30 PM - VV4.11
Lipidoids - a New Class of Material for Intracellular Delivery of Biomacramolecules.
Qiaobing Xu 1 , Janet Zoldan 1 , Seungwoo Cho 1 , Yadira Soto 1 , Kevin Love 1 , Hao Cheng 1 , Said Bogatyrev 1 , Nguyen David 1 , Michael Goldberg 1 , Christopher Levins 1 , Brian Carvalho 1 , Peter Bojo 1 , Patrick Wu 1 , Robert Langer 1 2 , Daniel Anderson 2
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe non-viral intracellular delivery of biomacromolecules (e.g. DNA, siRNA, et.al) remains an important challenge for clinical development. The diversity of current delivery materials remains limited, in part because of their slow, multi-step syntheses. Here, I will present a new class of lipid-like materials, as called "lipidoids", for the delivery of a variety of biomacromolecules into mammalian cells. The synthesis of lipidoids is based on an addition reaction between acrylates or acylamides with primary or secondary amines. We generated a library of lipidoids by varying the type of amines and the type of acrylates or acrylamides. This library of lipidoids have been screened in vitro for their ability to facilitate the delivery of a variety of biomacromolecules to the cells. The safety and efficacy of the delivery by lipidoids have also been investigated in mice.
5:45 PM - VV4.12
Lipid-Coated Nano- and Microparticles for Vaccine Design: Co-delivery of Adjuvants and Antigens by ``Synthetic Viruses" or ``Synthetic Bacteria."
Anna Bershteyn 1 , Elizabeth Riley 2 , Rui Freitas 3 , Luis Moita 3 , Darrell Irvine 1 2
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Cell Biology of the Immune System, Institute of Molecular Medicine, Lisbon Portugal
Show AbstractTo mimic the structure of lipid-enveloped pathogens, we used an oil-in-water emulsion process to create "synthetic pathogens" consisting of a biodegradable poly(lactide-co-gylcolide) core polymer coated by a phospholipid shell. The particles were characterized using confocal microscopy, scanning electron microscopy, and cryogenic transmission electron microscopy (CryoTEM). Emulsion synthesis of particles using sonication yielded ~100 nm particles, mimicking lipid-enveloped viruses, while homogenization yielded ~1 micron particles, mimicking bacteria in size. Confocal fluorescence microscopy revealed lipid self-assembly and two-dimensional fluidity at particle surfaces. CryoTEM revealed the possible lipid nanostructures that could be formed at particle surfaces by tuning the lipid content: single bilayer shells, multilamellar "onions," or petal-like "flowers. " Protein antigens could be encapsulated within the core or conjugated to the lipid surface via lipid headgroups containing sulfhydryl-reactive maleimide esters. Further, we functionalized these particles with pathogen-derived molecules such as ligands for Toll-like receptors (TLRs), to impart immunostimulatory properties to the particles for vaccine delivery and for basic studies of the immune response. Lipid-like molecules such as the clinically-relevant lipopolysaccharide analog monophosphoryl lipid A (MPLA) or the triacylated lipopeptide adjuvant Pam3Cys spontaneously incorporated into the lipid layers coating the surfaces of the particles, while more hydrophobic compounds, such as the small-molecule TLR7/8 agonist R848, were sequestered in the solid polymer core. Using this model system, we compared the relative immunogenicity of TLR ligand-carrying particles with surface-bound vs. encapsulated antigen -- two different approaches for particle vaccine formulation being pursued in a variety of preclinical vaccine studies. We found that localization of antigen at the surface vs. within the core of particles, as well as incorporation of one vs. multiple TLR agonists, has tremendous implications for guiding an immune response to vaccines. When particles with surface-conjugated protein antigen were internalized by splenic dendritic cells (DCs) in vitro, the presence of TLR ligands inhibited cross-presentation of antigen to CD8+ T-cells while enhancing antigen presentation to CD4+ T-cells. This result coincided with rapid acidification of phagosomes containing TLR ligand-functionalized particles. Our results imply that the enhancement in CD4+ T cell activation commonly reported for TLR agonists may come at the expense of CD8+ T cell priming in the case of particle surface-displayed antigen. In contrast, antigens encapsulated in the cores of particles exhibited enhanced cross-presentation when TLR ligands were co-delivered by the particles. Thus, control over antigen and adjuvant delivery may provide a means to promote cellular or humoral immune responses using the same delivery vehicle.
Symposium Organizers
Roger Narayan University of North Carolina
Suwan Jayasinghe University College London
Sungho Jin University of California-San Diego
William Mullins Office of Naval Research
Donglu Shi University of Cincinnati
VV5: Processing of Nanofibers and Nanoparticles for Medical Applications
Session Chairs
Kalpana Katti
Prashant Kumta
Thursday AM, December 03, 2009
Room 202 (Hynes)
9:00 AM - VV5.1
Electrospun HA-Biocomposite Scaffolds for Bone Tissue Engineering.
Perena Gouma 1
1 , SUNY Stony Brook, Stony Brook, New York, United States
Show AbstractNovel biocomposite nanofibrous materials were explored in this work as 3D scaffolds mimicking the architecture of a natural scaffold, that is porcine urinary bladder extracellular matrix. Natural polymers and their composites with nanocrystalline hydroxyapatite are the active elements of the scaffold. A series of cell (osteoblast) culture studies were carried out to assess the in-vitro effectiveness of the scaffolds to promote cell growth and differentiation. Cell viability studies were carried out in samples taken after they were cultured for 1, 7, and 14 days respectively. Analysis of osteoblast phenotypic markers (ALP activity and osteocalcin detection) was also carried out in these samples. Finally, scanning electron microcopy was used to evaluate the cell-nanofiber interactions. It was shown that the cells grown on hydroxyapatite (HA)-biocomposites had significant growth and mineralization. This was attributed to cell spreading on HA nanoclusters along the polymer fibers, as observed in the electron micrographs. These novel nanocomposites are promising candidates for synthetic bone applications.
9:15 AM - VV5.2
Poly(1,3-Butylene Fumerate) and Poly(1,3-Butylene Fumerate)-co-(1,3-Butylene Maleate) as Electrospun Scaffold Materials.
Kirsten Cicotte 1 2 , Shawn Dirk 1 , Elizabeth Hedberg-Dirk 2
1 Organic Materials Department, Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 Center for Biomedical Engineering and Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico, United States
Show AbstractPoly(butylene fumerate) (PBF) and poly(butylene fumerate)-co-(butylene maleate) (PBFcBM) have been synthesized from the ring opening and condensation reactions of maleic anhydride (MA) and 1,3-butanediol (BD). PBFcBM synthesized in this way contains greater than 85% maleate groups. Both PBF and PBFcBM have a glass transition temperature (Tg) below room temperature and therefore cannot be electrospun using the conventional electrospinning process as a non-porous film results. To facilitate production of nonwoven micro- and nano-fiber mats, a UV-source (λ=356 nm) was used in combination with a photoinitator loaded polymer solution to initiate the crosslinking reaction of the fumerate and maleate functional groups as the fibers were produced. The resulting non-woven fiber mats are potentially suitable scaffolds for tissue engineering and drug delivery application. Synthesis, electrospinning, degradation and initial cell studies will be discussed. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin company, for the United States Department of Energy under contract DE-AC04-94AL8500.
10:00 AM - VV5.4
Role of Scaffold Architecture and Mechanical Properties of Electrospun Scaffolds in Cell Seeding.
Nandula Wanasekara 3 , Ming Chen 2 , Vijaya Chalivendra 1 , Sankha Bhowmick 1 2
3 Materials and Textile Department, University of Massachusetts Dartmouth, North Dartmouth, Massachusetts, United States, 2 Bioengineering & Biotechnology Program, University of Massachusetts Dartmouth, North Dartmouth, Massachusetts, United States, 1 Mechanical Engineering, University of Massachusetts Dartmouth, North Dartmouth, Massachusetts, United States
Show AbstractSeeding a layer of cells at specific depths within scaffolds is an important optimization parameter for bi-layer skin models. Experimental investigation has been performed to investigate the effect of fiber diameter and its mechanical property on the depth of cell seeding of for electrospun fiber scaffold. Polycaprolactone (PCL) is used to generate scaffolds that are submicron (400nm) to micron (1100nm) using electro-spinning. 3T3 fibroblasts were seeded on the electro-spun fiber scaffold mat of 50-70 microns thickness in this study. In order to investigate the effect of fiber diameter on cell migration, first, the electrospun fiber scaffold was studied for variation of mechanical properties as a function of fiber diameters. Atomic force microscopy (AFM) was used to investigate the Young’s modulus (E) values as a function of fiber diameter. It was identified that as the fiber diameter increases, the Young’s modulus values decreases considerably from 1.1GPa to 200MPa. The variation in E is correlated with cell seeding depth as a function of vacuum pressure. A higher E value led to a lower depth of cell seeding (closer to the surface) indicating that nanofibrous scaffolds offer larger resistance to cell movement compared to microfibrous scaffolds.
10:15 AM - **VV5.5
Novel Nanoclay Based Biopolymer Scaffolds for Bone Tissue Engineering.
Kalpana Katti 1 , Avinash Ambre 1 , Nicholas Peterka 1 , Dinesh Katti 1
1 Civil Engineering, North Dakota State University, Fargo, North Dakota, United States
Show AbstractNovel nanocomposite systems are currently extensive investigated as candidates for bone tissue engineering scaffolds. The primary role of the scaffold is to provide mechanical support and allow the organization, growth, proliferation and differentiation of cells in the process of forming functional tissue by providing both physical and chemical stimulus. Use of nanoclays has been successfully implemented in design of barrier coatings and nanocomposites for structural applications. In our group we have developed an altered phase theory that describes the fundamental mechanisms of property enhancement by nanoclays in polymer-clay nanocomposites and also guidelines on suitable choice of clay modifiers. The use of nanoclays requires the modification by organic molecules that render the clays compatible with polymers to enable intercalation or exfoliation of clays. These molecules are often toxic and may not be used for biomedical applications. Here we report modification of Na-montmorillonite (Na-MMT) clay with unnatural amino acids in order to design intercalated clay structures that may be utilized for bone biomaterials applications. We demonstrate biocompatibity, cell viability and growth of osteoblasts on these modified clay systems and also incorporation of nanoclays into biopolymer based nanocomposite scaffolds and films. These studies open new avenues for incorporation of nanoclays into 3D scaffold systems with potential applications in bone tissue engineering.
10:45 AM - VV5: Processing
Break
11:00 AM - VV5.6
Development of Boron Cage Compound Nanocomposite Elastomers.
Eric Eastwood 1 , Daniel Bowen 1 , Mark Lee 2 , Fred Hawthorne 2
1 Materials Engineering, Honeywell FM&T, Kansas City, Missouri, United States, 2 International Institute of Nano and Molecular Medicine, University of Missouri - Columbia, Columbia, Missouri, United States
Show AbstractA wide variety of nanofillers of varying compositions have been used to create polymer nanocomposites including tubes, wires, fibers, sheets, and particles. A new class of compounds was identified for use as nanofillers, boron cage compounds. Boron cage compounds are discrete, icosahedral closed cage molecules of high boron content and examples include carboranes and dodecaborate salts. Several chemically modified boron cage compounds were incorporated into polyolefin elastomers such as poly(ethylene-co-vinyl acetate), poly(ethylene-co-vinyl acetate-co-vinyl alcohol), poly(ethylene-co-ethyl acrylate), and poly(ethylene-co-octene), among others, in order to modify the material properties. The resulting thermal and thermomechanical properties were evaluated to determine the conditions when plasticization and reinforcement occur to better understand the chemical structure/physical property relationships. Materials with a wide range of properties were produced, however under certain conditions, advanced materials were created with high boron contents, improved thermal stability, mechanical strength, and significant reinforcement.
11:15 AM - VV5.7
Radio-frequency Heating of Single-walled Carbon Nanotubes and Gold Nanoparticles for Hyperthermia of Cancer Cells.
Zulfiqar Chikani 1 2 , Leiming Xie 2 , Chinmay Darne 1 2 , Zheng-Zheng Shi 3 , Jarek Wosik 1 2
1 Electrical and Computer Engineering, University of Houston, Houston, Texas, United States, 2 Texas Center for Superconductivity, , University of Houston, Houston, Texas, United States, 3 Radiology , The Methodist Hospital Research Institute, Houston, Texas, United States
Show AbstractWe report on studies of single-walled carbon nanotubes (SWNT) and gold nanoparticles (GNP) parameters for rf-induced optimal heating rate at characteristic frequencies of 10, 64, 128 and 300 MHz. The potential of thermal therapy for cancer was first observed in rf hyperthermia and rf ablation procedures, for which cell temperatures increase to 41-46 °C and to 43-55 °C, respectively. The recent development of nanotechnology opened not only a possibility of enhanced but also non-invasive heating using external electromagnetic radiation. Selective delivery of nanoparticles to the tumor can result in very efficient and localized distribution of heat throughout the tumor. Nanoparticles introduced heating enhancement is analogous to a well-known effect of heating resistive structures in a body (ex. implants). Nanoparticles, including carbon nanotubes convert the rf energy into heat much more efficiently compared to direct rf tissue heating.The SWNTs used in this study were grown by high-pressure carbon monoxide disproportionation (HiPco) method and had an average diameter and length of 1.1 nm and 350 nm, respectively. They were individually suspended in 1 wt% aqueous non-ionic surfactant (Pluronic F108) using high-shear mixing, ultrasonication and ultracentrifugation processes. The final density of this homogeneous colloidal SWNT suspension was 30 mg/L. GNPs’ diameters measured here (TedPella company) were in the range of 5 nm to 200 nm and they were suspended in water.Two different high quality-factor (Q), resonators (maximum Q of 800) were designed to study mechanism of nanoparticles heating in either rf-electric and rf-magnetic fields. In order to obtain high Q we had to use high conductivity metals and low loss-tangent (single crystal sapphire) materials to build such resonators. The resonators were providing uniform rf-electric and rf-magnetic fields, achieving at 10 W of the rf input power, 200 V/mm and 5 mT, respectively. Temperature of water suspended nanoparticles was measured using either infrared camera (Electrophysics PV 320) or OTG-MPK5 Opsen’s fiber optic temperature sensors. The first method is non-contact, however, the temperature calibration is quite challenging. The fiber optic sensors are rf immune, because this method is based on measurements of the temperature-dependent band-gap of GaAs single crystal.Heating up to 60 degrees °C was measured at moderate level of rf-power. The most efficient heating enhancers were SWNT and GPN of 5 nm in diameter. Cytotoxicity studies with GNPs and SWNT were also successfully completed not showing any influence of these nanostructures on cells.The mechanism of SWNT and GPN heating based on their response to the rf-electric and magnetic fields as well tissue/nanoparticles heat transfer model will be discussed. For the optimized SWNT and 5 nm GPN samples, ex-vivo measurements (from microscope) of cultured cancer cells subjected to different level of rf-power will be presented and discussed.
11:30 AM - VV5.8
Multiwall Carbon Nanotube Scaffolds for Tissue Engineering Purposes.
Francisco del Monte 1 , Maria C. Gutierrez 1 , Maria L. Ferrer 1 , Maria J. Hortiguela 1 , Viviana Ramos 2 , Ander Abarrategui 2 , Jose Luis Lopez-Lacomba 2
1 , ICMM-CSIC, Madrid Spain, 2 , Universidad Complutense de Madrid, Madrid, Madrid, Spain
Show AbstractThis work demonstrates the validity of ISISA process for preparation of monolithic MWCNT/CHI scaffolds of utility for tissue engineering purposes. The MWCNT/CHI scaffolds were prepared by the ISISA (ice segregation induced self-assembly) process [1, 2]. For this purpose, MWCNT (6 wt. %) were dispersed in a buffered aqueous solution (1 mL) also containing chitosan (CHI, 1 wt. %) which allows for the achievement of a homogeneous suspension of MWCNT in water. The MWCNT/CHI suspension was frozen by unidirectional immersion into a liquid nitrogen bath. The ice formation (hexagonal form) caused every solute originally dispersed in the aqueous suspension to be segregated from the ice phase. Freeze-drying gave rise to ultraweightlighted (specific gravity is 8×10-2) and self-supported monolithic scaffolds which a microchanneled structure that resembles a chamber-like architecture in the form of interconnected MWCNT/CHI sheets arranged in parallel layers.The adsorption properties of MWCNT were used for incorporation of rhBMP-2, a potent osseo-inductor protein that promotes the differentiation of differentiated cells into an osteoblastic lineage. The activity of adsorbed rhBMP-2 was evaluated both in vitro and in vivo (by the ectopic bone formation at muscle tissue) with excellent results. The biocompatible character of the MWCNT/CHI scaffolds was remarkable accordingly these experiments. Such an excellent MWCNT biocompatibility was ascribed to the purification process used for MWCNT, which eliminated metal traces and amorphous carbon. It is noted that metals [3] and amorphous carbon [4] are reported to be the major factors responsible for MWCNT cytotoxicity. Disassembly of the MWCNT/CHI scaffold was observed for in vivo experiments, favored by cell colonization and tissue growth. Disassembly of the scaffold structure resulted in dispersion of some single MWCNT/CHI into the regenerated and the surrounding tissue but most of MWCNT/CHI forming the scaffold structure migrated from the implant zone. It is our belief that migration occurs by first, incorporation to the blood circulation system and lately, cleared from systemic blood circulation through the renal excretion route [5]. Further work must be conducted to corroborate this issue and also to explore the potentiality of MWCNT/CHI scaffolds for different tissue engineering purposes (e.g.; the high electric conductance of MWCNT/CHI scaffolds should make them highly suitable as substrates for neuronal growth). [1] A Abarrategui et al. Biomaterials 2008;29:94[2] MC Gutierrez et al. Chem. Mater. 2007;20:634–648.[3] CW Lam et al. Toxicol Sci 2004;77:126-134.[4] M Lundborg et al. Environ. Res. 2001;86:244-253.[5] R Singh et al. Proc Natl Acad Sci USA 2006;103:3357–3362
11:45 AM - VV5.9
Biocompatibility Assessment of a Conductive Ni-Ti-CNT Composite.
Puneet K. Gill 1 , Norman Munroe 1 , Chandan Pulletikurthi 1 , Waseem Haider 1 , Smit Pandya 1
1 Mechanical and Materials Engineering, Florida International University, Miami, Florida, United States
Show AbstractA novel ternary composite was prepared by incorporating CNTs into Nitinol (Ni-Ti), which can find applications in implantable devices such as bio-micro-fuel-cells. Due to the size limitations such bio materials should possess superior functional properties such as electrical conductivity, bio-compatibility etc. The composite was seeded with human umbilical vein endothelial cells in order to assess its biocompatibility and cell proliferation was studied with the aid of florescent microscopy. ASTM F 2129-08 cyclic polarization in vitro corrosion tests were conducted to evaluate the corrosion resistance in phosphate buffered saline (PBS) at 37 °C. The morphology of the composite was studied by SEM/EDS before and after corrosion tests. Surface resistance was determined by using four point probe technique.
12:00 PM - VV5.10
Preparation and Characterization of Carbon Nanotube-Reinforced Hydroxyapatite Nanocomposites.
Ashley White 1 , Roger Brooks 2 , Neil Rushton 2 , Alan Windle 1 , Ian Kinloch 3 , Serena Best 1
1 Dept. Materials Science and Metallurgy, University of Cambridge, Cambridge United Kingdom, 2 Orthopaedic Research Unit, Addenbrooke's Hospital, University of Cambridge, Cambridge United Kingdom, 3 School of Materials, University of Manchester, Manchester United Kingdom
Show AbstractHydroxyapatite (HA) is a biologically active ceramic that is used in surgery to replace and mimic bone. While HA promotes bone growth along its surface, its mechanical properties are not sufficient for major load-bearing medical devices [1]. Carbon nanotubes (CNTs), as one of the strongest and stiffest materials available [2], have the potential to strengthen and toughen HA, thus expanding the range of clinical uses for the material [3]. Furthermore, studies have suggested that the nanotubes themselves possess some bioactive properties [4-6].The work presented will comprise an overview of the preparation of these composite materials, results from studies on specially-designed atmospheres to sinter the composites, as well as results from mechanical tests and cell studies. HA was synthesized by the wet chemical method using Ca(OH)2 and H3PO4, and multiwalled CNTs were produced by chemical vapor deposition. Composite materials were made by the in-situ formation of HA in the presence of CNTs. Some of the CNTs were functionalized to improve their interaction with HA and make them dispersible in water. The resultant HA-CNT powders were pressed into pellets and sintered to produce the final specimens. The sintering parameters and atmosphere were optimized for maximum sintering of the HA, with minimal burn-out of the nanotubes and maximum retention of the hydroxyl groups of the HA. Additionally, the mechanical properties of the HA and composites were tested for tensile strength and toughness, and cell studies were conducted to examine cell proliferation and adhesion. We have studied the effect of CNT loading, CNT surface chemistry, and sintering conditions on the microstructure and mechanical and biological properties of the composites. The raw materials, composite microstructure, and HA-CNT interface were investigated using SEM, TEM, XRD, FTIR, and TGA; the mechanical properties of the composites were evaluated by diametral compression and toughness testing; and the biological properties were examined to determine the effect of CNTs on cell proliferation and adhesion.[1] Hench, J Amer Ceram Soc, 74 (1991).[2] Yu, et al., Science, 287 (2000).[3] White, et al., Int J Appl Ceram Technol, 4 (2007).[4] George, et al., J. of Exp. Nanoscience, 1 (2006).[5] Zanello, et al., Nano Lett, 6 (2006).[6] Price, et al., Biomater, 24 (2003).
12:15 PM - **VV5.11
Complex Engineered Nanostructured Materials and Hybrid Composite Delivery Systems for Bone Regeneration.
Prashant Kumta 1
1 Swanson School of Engineering and School of Dental Medicine, University of Pittsburgh, Pittsburgh , Pennsylvania, United States
Show AbstractTissue engineering and nanotechnology in recent years have brought an extraordinary transformation in the biomaterials field. Consequently, new biodegradable scaffolds containing functionalized carriers have led to the development of novel drug, protein, growth factors, DNA, including stem cell delivery systems. Innovative 3-D printing of complex biological structures has additionally provided a unique manufacturing platform for generating novel 3-D structures mimicking the intricate microstructures of biological systems and organs. There is still much to be desired with regards to providing a viable clinical therapy for bone regeneration. This presentation will discuss the collaborative efforts at the University of Pittsburgh between the engineering, dental medicine and school of medicine faculty to generate next generation concepts for bone regeneration. These concepts involve a unique combination of novel nanostructured calcium phosphates (NanoCaPs) particulates, NanoCaPs-biologics gel based hybrid structures including injectable CaP containing biocompatible bio-cements that can serve as carriers of proteins, plasmid DNA, normal and stem cells. A paradigm shift in the synthesis, design, and processing of biodegradable metals and composite structures is also being explored with the inception of the recently funded NSF sponsored Engineering Research Center (ERC)-Revolutionizing Metallic Biomaterials. A distinctive aspect is the fusion of these various novel strategies for the generation of revolutionary biocompatible porous and 3-D biodegradable composite hybrid structures as “smart functional” load bearing alternatives for mineralized tissue regeneration. Such a strategy could offer myriad options for providing customized medical treatments for various bone related injuries and ailments.
12:45 PM - VV5.12
Sonochemical Synthesis and Characterization of Bio-Based Hydroxyapatite Nanoparticles.
Vijaya Rangari 1 , Tarig Hassan 1
1 Materials Science and Engineering, Tuskegee University, Tuskegee, Alabama, United States
Show AbstractHydroxyapatite is a natural bio ceramic material that contains calcium phosphate group. It is mainly used in bio medical applications due to its structural similarity to the bone and teeth in the human body. More than seventy percent of the human bones are composed of hydroxyaptite. Man made hydroxyapatite is considered as a good bone replacement material because of strong chemical bond with host bone tissue and it also can be used in the field of nanocomposites. In this study we explore the synthesis of hydroxyapaite nanoparticles using the sonochemical method. In this technique phosphoric acid solution was used as the source of phosphor and egg shell particles was used as the source of calcium. Due to the high cost and environmental hazard of the petroleum and mineral derived products, a growing effort has emerged in recent years on the research, development, and application of bio-composites materials for engineering applications. Chicken eggshell is an industrial byproduct that contains about 95% calcium carbonate and can offer a great material for industrial and structural applications. Phosphoric acid and calcium hydroxide particles derived from eggshell were irradiated with high intensity ultrasonic horn (Ti-horn, 20 kHz, 100 W/cm2 at 50% amplitude) for 2 hours at 10°C in the presence of distilled water. The resultant product was obtained via repeated washing in water and centrifuge then vacuum dried for 24 hours. The product was characterized using XRD and TEM analysis. Keywords: Hydroxyapatite, Bio Nanoparticles, Eggshell and Sonochemical method.
VV6: Properties and Processing of Biological and Bioinspired Materials
Session Chairs
Mehmet Sarikaya
Donglu Shi
Thursday PM, December 03, 2009
Room 202 (Hynes)
2:30 PM - VV6.1
Unveiling the Formation Mechanism of Nanostructured Aragonite Platelets in Nacre.
Xiaodong Li 1 , Zaiwang Huang 1
1 Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina, United States
Show AbstractPrevalent viewpoint regarding nacre’s aragonite platelets as single crystals has been held for several decades. Recent atomic force microscopy (AFM) observation indicates that an aragonite platelet is composed of a large amount of nanoparticles with an average size of 32~44 nanometers. These apparently contradictive results have triggered a new debate on the basic structural elements of nacre, whether an aragonite platelet is a pure monocrystal or made of complex polycrystals. Here we demonstrate direct evidence that a single crystal-like aragonite platelet is essentially assembled with aragonite nanoparticles. The aragonite nanoparticles are readily oriented and assembled into pseudo-single crystal aragonite platelets via screw dislocation and amorphous aggregation, which are two dominant mediating mechanisms between nanoparticles during biomineralization. These findings will advance our understanding of nacre’s biomineralization process and provide additional design guidelines for developing biomimetic materials.
2:45 PM - **VV6.2
Biologically Active Collagen-based Scaffolds: Advances in Processing and Characterization.
Ioannis Yannas 1 , D. Tzeranis 1 , B. Harley 1 , P. So 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractA small number of type I collagen-glycosaminoglycan scaffolds (collagen-GAG scaffolds or CGS) have unusual biologically activity consisting primarily in inducing partial regeneration of organs in the adult mammal. Two of these are currently in use in a variety of clinical settings. CGS appear to induce regeneration by blocking the adult healing response, following trauma, consisting of wound contraction and scar formation. Several structural determinants of the biological activity have been identified, including ligands for binding of fibroblasts to the collagen surface, the mean pore size (which affects ligand density) and the degradation rate (which affects the duration of the wound contraction-blocking activity by the scaffold). Processing variables that affect these determinants include the kinetics of swelling of collagen fibers in acetic acid, freezing of the collagen-GAG suspension and crosslinking of the freeze-dried scaffold. Recent developments in processing of CGS include fabrication of scaffolds that are paucidisperse in pore size, scaffolds with gradients in physicochemical properties (and therefore biological activity), and scaffolds that incorporate a mineral component. Advances in characterization of the pore structure of CGS have been made by use of confocal and nonlinear optical microscopy. The mechanical behavior of CGS as well as the resistance to degradative enzymes have been studied. Following seeding with cells (typically fibroblasts), contractile forces in the range 26 - 450 nN per cell are generated by the cells, leading to buckling of scaffold struts. Ongoing studies of cell-seeded CGS with nonlinear optical microscopy have shown an advantage over the use of confocal microscopy due to the ability of the former method to image the CGS surfaces without staining (which alters its surface ligands), reduced cell photo-damage, reduced fluorophore photobleaching, and the ability to image deeper inside the scaffold.
3:15 PM - **VV6.3
Genetically-Engineered Peptides as Molecular Building Blocks for Materials Synthesis, Assembly and Fabrication.
Mehmet Sarikaya 1 2
1 Genetically Engineered Materials Science and Engineering Center, University of Washington, Seattle, Washington, United States, 2 Departments of Materials Science and Engineering, and Chemical Engineering, University of Washington, Seattle, Washington, United States
Show AbstractWith wisdom gained from long experience, Mother Nature has evolved mechanisms of simplicity and elegance to synthesize soft and hard tissues exhibiting remarkable functional properties. Nature achieves these feats of engineering by making use of molecular building blocks and by controlling materials assembly in a hierarchical manner from the nano- to the macroscale. With a growing understanding of the processes involved came the realization that biological principles may have applications for solving problems in human-made systems. There is indeed a rich and long history of gaining inspiration from Nature’s biological structures to design practical materials and systems. Traditionally, biomimeticists have focused on emulating or duplicating biosystems using mostly synthetic components and conventional approaches. By merging recent advances in molecular biology with state-of-the-art engineering and characterization from the physical sciences, our goal in Molecular Biomimetics been to shift the biomimetic materials science paradigm from imitating Nature to engineering natural materials to perform artificial functions. Here, we combine biology’s proven molecular tools, i.e., peptides, with synthetic nanoscale constructs, e.g., nanoparticles, to make molecular biomimetics a full-fledged methodology. Through combinatorial biology, genetic engineering and bioinformatics approaches, we developed and adapted genetic protocols to design polypeptides specific for inorganic and organic surfaces, and utilize them in bio-inspired pathways to manufacture a new generation nanostructured, multifunctional materials for biotechnology, nanotechnology, and molecular medicine. Acknowledgements: I would like to thank my close colleagues Professors C. Tamerler (ITU/UW), R. Samudrala (UW), and M. Snead (UCS). This project is supported by GEMSEC, an NSF-MRSEC at the University of Washington, and NSF BioMat and IRES programs.
3:45 PM - VV6.4
Functional Protein Fibers: Processing, Characterization, and Application.
Natalia Tansil 1 , Ming-Yong Han 1
1 Synthesis and Integration, Institute of Materials Research and Engineering, Singapore Singapore
Show AbstractNatural protein fibers offer an advantageous combination of excellent physical properties and inherent biocompatibility. Unfortunately, most of these fibers lack the thermal and chemical resistance that are required for modification or fine-tuning of their properties; hence limiting their actual use. On the other hand, the incomplete understanding on the in-vivo processing of natural protein fibers has hindered a complete reproduction of their properties using in-vitro techniques. An optimal approach is therefore required to add functionalities to these fibers while preserving their advantageous natural characteristics. Various functional materials--ranging from biomolecules such as enzymes and growth factors to inorganic nanoparticles of titania and gold--have been indeed been grafted onto protein fibers to produce multifunctional, biocompatible fibers. However, there has been limited effort toward the complete integration of the functional materials with the protein fibers at the molecular level. In this work, we studied the effect of functional group, molecular structure, size, and crosslinking conditions on the interaction between these two components. Luminescent dyes and nanoparticles, used as representative of functional materials, were successfully incorporated into protein fibers. The use of these luminescent materials also allowed us to conveniently study their interaction using confocal and fluorescent microscopy. Through a better selection, design, and modification of functional materials with stable and tailorable interaction with the fibers, we aim to enable the use of natural protein fiber especially as value-added biomaterials.
4:00 PM - VV6: Properties
BREAK
4:15 PM - VV6.5
Targeted Drug Delivery to Respiratory Tract for Prophylaxis of Free Radical-induced Damage in Second-hand Tobacco Smoking.
Alexey Vertegel 1 , Vladimir Reukov 1 , Victor Maximov 1 , Ryan Mulligan 2 , Rodney Schlosser 2 , Carl Atkinson 2
1 Bioengineering, Clemson University, Clemson, South Carolina, United States, 2 , Medical University of South Carolina, Charlestone, South Carolina, United States
Show AbstractFree radical-induced damage makes an important contribution to harmful effect of tobacco smoke on both the upper and lower respiratory system. No therapy exists at present to prevent or alleviate these effects. Superoxide dismutase (SOD) has recently been proposed as potentially powerful therapeutic agent for resolution of inflammation. It can thus be expected that the sustained presence of SOD in the respiratory tract will reduce the incidence and/or alleviate the symptoms associated with the inhalation of tobacco smoke. However, one problem associated with therapeutic use of SOD for respiratory conditions is ensuring that topically administered therapeutics actually reach the respiratory mucosa and remain in contact with it long enough to be effective. Normal mucociliary clearance typically results in rapid removal of topical medications within 15-20 minutes when it would be desirable to maintain mucosal contact for hours to days. Here, we report targeted delivery to and retention of SOD on respiratory epithelium using biodegradable polylactic acid (PLA) nanoparticles as delivery vehicles. SOD and a targeting antibody (MUC1), which binds to an epitope on the surface of epithelial cells, were simultaneously attached to PLA nanoparticels. Using in vitro sinonasal epithelial cell cultures, we demonstrated that cigarette smoke extract (CSE) induces a vigorous inflammatory response, as evidenced by secretory mediators. This inflammatory response can be inhibited with the use of SOD, thus confirming that SOD has therapeutic potential. Furthermore, we showed that PLA-MUC1-SOD nanoparticles readily bind to the surface of epithelial cells and remain attached to the surface for at least 4 days, while unconjugated SOD and PLA-SOD nanoparticles lacking the antibody were cleared within minutes.In a pilot in vivo study, mice were exposed to 3 days of cigarette smoke at a dose of 4 cigarettes/mouse/exposure with mice receiving two exposures per day. Mice were either treated with PBS or PLA-MUC1-SOD nanoparticles daily 30 minutes prior to the first daily exposure. Lungs were harvested 12 h following the final exposure, and the degree of alveolar inflammation, production of reactive oxygen species and lung histology analyzed. Histological studies demonstrated that animals treated with PBS showed evidence of neutrophil accumulation within the parenchymal wall and surrounding vascular structures, and evidence of epithelial cell vacuolization and cytoplasmic blebbing, features associated with cell death and damage. In contrast animals treated with PLA-MUC1-SOD nanoparticles showed few parenchymal inflammatory infiltrates and no obvious evidence of epithelial hyperplasia. We also found significantly lower levels of reactive oxygen species in mice treated by PLA-MUC1-SOD nanoparticles versus PBS treated controls. Taken together these studies demonstrate that PLA-MUC1-SOD nanoparticles were efficient in this model of acute cigarette smoke exposure.
4:30 PM - VV6.6
pH-responsive Coiled-coil Peptide Functionalised Surfaces.
Caterina Minelli 1 2 , Jian Liew 1 3 , Murugesan Muthu 2 , Heiko Andresen 1 2 , Molly Stevens 1 2
1 Materials, Imperial College London, London United Kingdom, 2 Institute of Biomedical Engineering, Imperial College London, London United Kingdom, 3 Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Victoria, Victoria, Australia
Show AbstractCoiled coil peptides play important functional roles in numerous biological processes. In depth knowledge of the folding mechanisms of coiled coils can contribute to a better understanding of these biological processes and allows the full exploitation of their potentials in a wide range of applications. Inspired by nature, we designed and synthesized responsive functional materials incorporating coiled coil motifs whose assembly/disassembly can be triggered by exact cues such as changes in environmental pH and temperature. For example, we modified the well-known structure of the leucine zipper coiled-coil of the yeast transcriptional activator GCN4 by introducing glutamic acid and lysine amino acids alongside the hydrophobic core of the coiled coil. At low pH, salt bridges contribute to the stability of the coiled coil, while glutamic acid residues destabilize the coiled-coil assembly at high pH. The peptides were synthesized by solid state synthesis, purified, and identified by mass spectroscopy. We studied the conformation and the peptide self-assembly by circular dichroism spectroscopy under different conditions of solvent pH, ionic strength, temperature and polarity. As predicted, the peptides form coiled coil homodimers at low pH and unfold for higher pH, with a sharp transition around pH 5.8.We used these peptides to create functional responsive surfaces. We studied the behaviour of the peptides when bound to gold surfaces using surface plasmon resonance spectroscopy and quartz crystal microbalance with dissipation monitoring. The surface density of the peptides was controlled by selecting, during surface functionalization, a solution pH and polarity permitting a more or less compact conformation of the peptides. We then demonstrated that the coiled coils still undergo conformational changes with pH when bound to the surface. The coiled coils were used as switching anchor points to bind nanoparticles in an environmentally controlled reversible manner. These peptide engineered surfaces may find a broad range of applications, for example in sensor technologies.
4:45 PM - VV6.7
Functionalization and Patterning of Chimeric Protein-based Materials.
Zhao Huang 1 , Yang Lu 2 , Jaimin Shah 1 , Kathleen Matthews 1 , Jun Lou 2 , Sarah Bondos 3 1
1 Biochemistry and Cell Biology, Rice University, Houston, Texas, United States, 2 Mechanical Engineering and Materials Science, Rice University, Houston, Texas, United States, 3 Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, Texas, United States
Show AbstractA key advantage of protein-based materials is the potential to directly incorporate novel functions via gene fusion to produce chimeric polypeptides capable of both self-assembly and the desired chemical reactivity. However, facile production of functionalized protein materials is frequently hampered by the need to generate recombinant chimeric monomers and the requirement to assemble the materials in conditions that will not irreversibly damage the functional protein. In contrast, the gene encoding the Drosophila melanogaster transcription factor Ultrabithorax (Ubx) is stable in E. coli, and the recombinant protein rapidly self-assembles in gentle, aqueous conditions to form materials with a variety of morphologies. Ubx chimeras with either Enhanced Green Fluorescent Protein (EGFP) or mCherry generate fluorescent materials, demonstrating the activities of the functional proteins are neither impaired by the assembly process nor by confinement within the material. Conversely, the fusions do alter the mechanical properties of the materials; however, the chimeric materials retain to a large extent the remarkable extensibility of their wild-type counterparts. Finally, we have established methods that combine EGFP-Ubx and mCherry-Ubx monomers to self-assemble patterned materials. The self-adhesive properties of Ubx materials also permit manual construction of microscale to macroscale patterned materials. The ability to easily functionalize and pattern protein-based materials expands their potential utility in a wide variety of applications.
5:00 PM - VV6.8
Complementary Silk-Siloxane Hybrid Optofluidics.
Konstantinos Tsioris 1 , Peter Domachuk 1 2 , Graham Tilburey 1 , David Kaplan 1 , Fiorenzo Omenetto 1
1 Biomedical Engineering, Tufts University, Medford, Massachusetts, United States, 2 CUDOS, University of Sydney , Sydney , New South Wales, Australia
Show AbstractAn important application of polydimethyl-siloxane (PDMS) -based microfluidic devices is small volume chemical analysis or “lab-on-a-chip”. While this technology reduces volumes of analytes used, volumes of samples required and increases analysis efficiency, it is not the most expedient or efficient for creating a simple, disposable chip to perform a single (or small battery) of tests on a disposable substrate for point-of-care use. Such a device would require the constituent material of the device itself to be functionalized with appropriate reagents. Functionalizing PDMS, however, typically requires significant chemical processing that limits the variety of dopants and introduces significant fabrication investment. We propose a hybrid-polymer approach, whereby the PDMS forms the bulk of the microfluidic device and a second polymer is functionalized and used to form one surface of the device allowing analytes to flow over it and react with the functional surface. We further demonstrate the use of functionalized silk fibroin protein for the additional polymer layer. Much like PDMS, the optical properties of silk are also favorable for making optofluidic devices; silk films (approximately 100µm thick) with greater than 95% transmission over the visible have been demonstrated [1]. We demonstrate a hybrid-polymer silk-PDMS optofluidic device which enables a broad range of functional sensitivities with minimal fabrication overhead and good optical quality. We embody such a device by using a diazonium coupled silk film (or, simply, “azo-silk”) [2] that is pre-fabricated and integrated into the floor of a PDMS microfluidic channel. The azo-silk has a spectral absorption that changes in response to pH in the microfluidic channel.We present a method for using multiple polymers, in this case PDMS and silk fibroin, to combine the inherent ease of functionalization of silk with the fabrication versatility of PDMS. This enables compact opto- and micro-fluidic sensing platforms where the optofluidic network is provided by the PDMS and the biochemical/optical signature is provided by the silk layer. We use this approach to demonstrate a proof-of-principle micro-flow pH sensor based on the changes in spectral response of the active silk layer incorporated in the PDMS device. The opportunities available to functionalize biopolymer layers offer the broader application of micro- and optofluidic technologies. This material system is also a promising candidate for potential in vivo sensor applications such as functional material coated optical fibers.[1]B. Lawrence, M. Cronin-Golomb, I. Georgakoudi, D. Kaplan, and F. Omenetto, "Bioactive Silk Protein Biomaterial Systems for Optical Devices," Biomacromolecules, vol. 9, pp. 1214-1220, 2008.[2]A. Murphy, P. John, and D. Kaplan, "Modification of silk fibroin using diazonium coupling chemistry and the effects on hMSC proliferation and differentiation," Biomaterials, vol. 29, pp. 2829-2838, 2008.
5:15 PM - VV6.9
Greatly Increased Toughness of Infiltrated Spider Silk.
Seung-Mo Lee 1 , Eckhard Pippel 1 , Ulrich Goesele 1 , Christian Dresbach 2 , Yong Qin 1 , C. Vinod Chandran 3 , Thomas Braeuniger 3 , Gerd Hause 4 , Mato Knez 1
1 , Max Planck Institute of Microstructure Physics, Halle(saale) Germany, 2 , Fraunhofer Institute for Mechanics of Materials, Halle(saale) Germany, 3 Institute of Physics , Martin-Luther-University Halle, Halle(saale) Germany, 4 dMicroscopy Unit Biocenter, Martin-Luther-University Halle, Halle(saale) Germany
Show AbstractIn nature, tiny amounts of inorganic impurities, such as metals, are incorporated in the protein structures of some biomaterials and lead to unusual mechanical properties of those materials. A desire to produce these biomimicking new materials has stimulated materials scientists, and diverse approaches have been attempted. In contrast, research to improve the mechanical properties of biomaterials themselves by direct metal incorporation into inner protein structures has rarely been tried because of the difficulty of developing a method that can infiltrate metals into biomaterials, resulting in a metal-incorporated protein matrix. We demonstrated that metals can be intentionally infiltrated into inner protein structures of biomaterials through multiple pulsed vapor-phase infiltration performed with equipment conventionally used for atomic layer deposition (ALD). We infiltrated zinc (Zn), titanium (Ti), or aluminum (Al), combined with water from corresponding ALD precursors, into spider dragline silks and observed greatly improved toughness of the resulting silks. The presence of the infiltrated metals such as Al or Ti was verified by energy-dispersive x-ray (EDX) and nuclear magnetic resonance spectra measured inside the treated silks. This result of enhanced toughness of spider silk could potentially serve as a model for a more general approach to enhance the strength and toughness of other biomaterials.
5:30 PM - VV6.10
Vesicle Based Gelation of Alginates for Inkjet Printed Scaffolds.
Rachel Saunders 1 , Kwan Liem 2 , Robert Mart 2 , Simon Webb 2 , Brian Derby 1
1 The School of Materials, The University of Manchester, Manchester United Kingdom, 2 School of Chemistry and Manchester Interdisciplinary Biocentre, The University of Manchester, Manchester United Kingdom
Show AbstractDrop-on-demand inkjet printing is a fabrication technique which is capable of depositing materials layer-by-layer to form complex constructs. Previous studies have established the feasibility of printing as a cell patterning technique, demonstrated by a post-printing cell viability exceeding 95% [1]. The next step is the simultaneous deposition of scaffold matrix and cells, which would yield improved cell-construct integration and control over cell placement. This work presents a novel single drop delivery mechanism in which both the matrix and cross-linker are present but separated through the use of vesicle packaging. The incorporation of calcium-loaded thermally triggered vesicles in alginate solution provides a printable material with controlled gelation [2]. This gelation system is an important advance towards the goal of simultaneous fabrication of a hybrid scaffold and can contribute to the minimisation of key issues such as hydration and pattern preservation.Printing parameters were found to have no effect on the integrity of the calcium-loaded vesicles. Alginate solutions containing calcium-loaded vesicles were successfully printed and the printed layers were shown to gel on demand at 37 °C. Printed alginate layers were evaluated with regards to their potential to provide three dimensional structures. Hydration of the printed gel during printing is key to the construction of a multi-layer scaffold and several hydration mechanisms have been evaluated.1.Saunders, R.E., Gough, J.E., and Derby, B. Delivery Of Human Fibroblast Cells By Piezo-electric Drop-On-Demand Inkjet Printing. Biomaterials, 2008. 29: P. 193-203.2.Westhaus, E. and Messersmith, P.B. Triggered Release Of Calcium From Lipid Vesicles: A Bioinspired Strategy For Rapid Gelation Of Polysaccharide And Protein Hydrogels. Bioma-terials, 2001. 22(5): P. 453-462.
VV7: Poster Session: Micro- and Nanoscale Processing of Biomaterials
Session Chairs
Suwan Jaysinghe
Sungho Jin
William Mullins
Roger Narayan
Donglu Shi
Friday AM, December 04, 2009
Exhibit Hall D (Hynes)
9:00 PM - VV7.1
A Bio-inspired Design for Greater Energy Absorption in Personnel Protective Systems.
Juliana Bernal Ostos 1 , Nicole Schauser 3 , Frank Zok 1 , Galen Stucky 2
1 Materials, University of California, Santa Barbara, Santa Barbara, California, United States, 3 , Dos Pueblos High School, Goleta, California, United States, 2 Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California, United States
Show AbstractWe use principles gleaned from biological materials to improve energy absorption under compression by smoothly interfacing materials that have drastically different mechanical properties. How to best interface materials with a mismatch in their stiffness values has long been an area of scientific research and a question of practical importance for the creation of mechanically sound composite structures. Studies of natural systems that exhibit such interfaces have shown that Nature often employs structural and compositional gradients rather than sharp, sudden changes between the two materials. Examples of this in biological materials include the byssal threads that anchor mussels to stone, the interface between the soft tissue of jumbo squids and their hard beaks, and the transition between tendons and bone through fibrocartilage in the human body. In contrast, man-made materials and structures typically employ sharp interfaces. In order to compensate for the inherent weakness at the interface, these materials and structures often require additional support mechanisms, which come at a cost and reduce the efficiency of the overall structure. In personnel protective systems research and development, there is a push to apply bio-inspired design ideas to the creation of materials that absorb more energy per unit weight than the materials that are currently available. The energy absorbing materials in personnel protective systems serve as an interface between a hard and stiff buffer plate and the protected personnel. In this work we investigate the effects of a gradient in relative density on the ability of foam materials to absorb energy under compression. We have developed a technique to create polyurethane foam materials with tunable density gradients. We have used this technique to create foams containing two, three and four density levels, and we have tested the resulting foams under compression according to ASTM 1621. Our results show that graded foam structures can absorb more energy per unit weight than non-graded foams. This result will inform the design and creation of bio-inspired materials for future personnel protective systems.
9:00 PM - VV7.11
Protein Encapsulation into Polylactide Particles by Electrohydrodynamic Spray Drying Using Coaxial Nozzles.
Hwanki Ho 1 , Jonghwi Lee 1
1 Department of Chemical Engineering and Materials Science, Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractSpray drying is a widely used process to produce food and pharmaceutical powders. In the traditional spay drying process, the particle size distribution is relatively wide and not well controlled. Electrospraying technology has been studied in many fields to produce particles of various substances in nano-/microsize with using properly controlled processing variables and solution properties. The use of electrohydrodynamic force in spray drying offers a possibility to tailor the particle size and morphology. Electrohydrodynamic spray drying uses a strong electric field to induce spraying jets in addition to the air stream of spray drying. Encapsulation can be achieved by the electrohydrodynamic jetting of coaxial nozzles, which stabilizes sensitive active ingredients and controls their release in a diverse range of applications including foods, pharmaceuticals, and cosmetics applications. The present work describes the application of novel electrohydrodynamic spray drying of coaxial nozzles for protein delivery. The coaxial electrospraying with two immiscible fluids are systematically investigated to engineer the release rate of the protein. This simple method can microencapsulate proteins into polylactide (PLA) microspheres with minimal aggregation. The size distribution of the generated particles was narrow. The obtained particles were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and UV/Vis spectroscopy. Core/shell structure and morphology affects the release rate of the protein with respect to the thickness and channel existence in the shell. Lysozyme was released from the PLA microspheres in a sustained release manner with minimal initial burst release.
9:00 PM - VV7.12
Encapsulation of Oil into Water-Soluble Polymer Particles by Electrohydrodynamic Jetting.
Harim Bae 1 , Jonghwi Lee 1
1 Department of Chemical Engineering and Materials Science, Chung-Ang university, Seoul Korea (the Republic of)
Show AbstractEncapsulation is an important technique being used to protect sensitive active materials. The capsule wall isolates them from the atmospheric oxygen, moisture, temperature and light. The essential oil and organic extracts of Zizyphus jujube, which is sensitive to the environmental stimuli, have antimicrobial efficacy against food-borne pathogens (natural preservatives). In this study, essential oil-loaded chitosan particles were prepared using an electrospraying technique, in which a sufficiently strong electric field was applied to overcome the surface tension of a droplet. A co-axial electrospray process was developed to encapsulate immisible liquids located in each inner and outer nozzle. Microparticles of approximately 2 μm with smooth surfaces were observed by a scanning electron microscope. Confocal laser scanning microscope images showed that oil was distributed evenly in the microparticles. Entrapment of oil in the core-shell structure is expected to slow down the release of volatiles and guarantee more protection for oil against atmospheric conditions. This method may have a potential application in different types of food or pharmaceutical products where maximum protection for flavours or sustained release is required.
9:00 PM - VV7.13
Diffusion Dynamics of the NLS Coated Quantum Dot Inside the Cell Nucleus.
ChiungWen Kuo 1 , TI-Yen Chueh 1 , Peilin Chen 1
1 Research Center for Applied Sciences, Academia Sinica, Taipei Taiwan
Show AbstractRecently, there is an increasing research activity focused on the development of various nanoparticles for the gene delivery. However, it was found that the nanoparticles are often trapped on the cell membrane or inside the cytoplasm due to the particle size and the lack of nuclear targeting mechanism. Semiconductor nanocrystals, also known as quantum dots, are known to be small enough for entering the cell nucleus and to exhibit superior optical properties allowing the tracking of single nanoparticles inside the cells for a long time. When the quantum dots are decorated with nuclear localization signaling (NLS) peptides, it has been shown that the efficiency for the nanoparticles to enter the cell nuclear has been increased. Therefore, it is very interesting to investigate the dynamic of the quantum dots coated with NLS inside the living cells. Here, we report the study of the dynamic of the core/shell quantum dots (CdSe/Zns) coating with NLS by total internal reflection microscopy (TIRFM). We have examined the nuclear entry process of the quantum dots without using the transfection reagent. The amine presenting quantum dots was linked to different cysteine terminated NLS through the maleimide conjugation. It was found that at a higher concentration of quantum dot (8 nM), most of the nanoparticles were aggregated in the cytoplasm. However, at a lower concentration (0.08 nM), about 15% of the NLS coated quantum dots could enter the cell nucleus. To investigate the individual dynamic of individual nanoparticles, we have been recorded the trajectories of the NLS coated quantum dots in the perinucelar region. The average diffusion coefficient of the trajectories was measured to be 0.5 um^2/s (n=60). Two different types of trajectories, confined and diffusive, have been identified.
9:00 PM - VV7.14
Core-shell Structured Composite Nanofiber Containing Two Different Growth Factors for Wound Healing.
Hyuk Sang Yoo 1 , Ji Suk Choi 1 , Shinyoung Park 1 , Hyesung Kim 1 , Hyun Ah Jung 1
1 , Kangwon National University, Chuncheon Korea (the Republic of)
Show AbstractCoaxial electrospinning received much attention because water-soluble protein in aqueous phase can be electrospun with polymers in organic phase. In coaxial electrospinning, two immiscible phases composed of organic and aqueous phase are electrospun through a dual nozzle composed of an inner and an outer nozzle. In this study, we prepared a coaxial nanofiber simultaneously containing encapsulated basic fibroblast growth factor (bFGF) and chemically-immobilized epidermal growth factor (EGF). For coaxial electrospinning, the outer solution composed of a mixture of poly(ε-caprolactone)-poly(ethylene glycol) and poly(ε-caprolactone) in a chloroform/methanol mixture and the inner solution composed of bFGF in 1% poly(vinyl alcohol) solution were simultaneously electrospun to fibrous meshes. Flow rates of the inner solution and the outer solution were 0.1 and 1.0 (ml/h), respectively. A coaxial nanofiber containing bFGF in the core was employed for surface modification with EGF. EGF, HOBt, and EDC were reacted with surface-exposed amine groups of the nanofiber in phosphate buffered saline (pH 8.0). An extent of chemical modification was determined by X-ray photoelectron spectroscopy (XPS). Wound healing efficacy of the nanofiber was tested in female C57BL/6 mice with diabetic ulcers at dorsal area. The nanofibers were applied to aseptically-treated wounds. Coaxial electrospinning successfully generated nanofibers with a core-shell structure. Because bFGF was encapsulated completely inside the nanofiber, the nanofiber with the conjugated EGF showed a significant peak of N1s while the encapsulated bFGF nanofiber showed only C1s and O1s peaks. An extent of wound closer was measured at day 4 and 7, where a bFGF-EGF nanofiber treatmentshowed the superior wound closer result compared to EGF nanofiber, bFGF nanofiber, and a control group.Two different growth factors were successfully encapsulated and immobilized in a single nanofibrous mesh. A multi-functional nanofiber can be a superior candidate for drug delivery system for wound healing.
9:00 PM - VV7.15
Bi-segmented Nanorods for Multi-functional Drug Carrier.
Hyuk Sang Yoo 1 , Ji Suk Choi 1 , Shinyoung Park 1 , Hyesung Kim 1 , Hyun Ah Jung 1
1 , Kangwon National University, Chuncheon Korea (the Republic of)
Show AbstractNanorods offer a unique ability to combine a number of essential diagnostic, imaging, delivery and dosage properties compared to traditional spherical particles. In this study, a bi-segmented nanorod was fabricated by electrodeposition and further surface-modified with temperature-responsive polymers in an aim to non-covalently immobilize an anti-cancer drug on the rods. A silver layer coated on one side of an Al2O3 template served as a working electrode in a three-electrode configuration. After pre-deposition of nickel on the template, gold and nickel were sequentially deposited to prevent erosion of the nickel segment during pre-deposited nickel dissolution. Length of each segment was controlled by changing the amount of coulombs applied during the deposition. The pre-deposited nickel layer was removed using HNO3 solution and the template was dissolved using NaOH solution. A diameter of the fabricated segment was measured by SEM, suggesting that the diameter was 100nm and the length ranged from 1000nm to 2500nm. A gold segment was chemically modified with Pluronic F-127 to encapsulate excessive amounts of doxorubicin around the nanorod according to temperature changes and a nickel segment was decorated with folate to confer an active targeting moiety to the nanorod toward cancer cells. Thiol-modified Pluronic was conjugated to the gold segment and a carboxyl group of folate was attached to the nickel segment. Conjugation of folate and encapsulation of doxorubicin were visualized by confocal microscopy. Doxorubicin encapsulation was precisely controlled by changing temperatures with an ‘on-and-off’manner. Doxorubicin was maximally encapsulated around the modified nanorods at 37°C and a full extent of doxorubicin release was observed at 4°C. Further studies are required determine amounts of drug loading according to gold segment length using Pluronic F-127, targeting effects of folate. In addition, pharmacodynamics of doxorubicin-encapsulated nanorods should be also optimized to employ nanorods as multifunctional anti-cancer drug carriers.
9:00 PM - VV7.16
Surface Modification of Electrospun Nanofibers for Gene Delivery in Diabetic Ulcers.
Hyuk Sang Yoo 1 , Ji Suk Choi 1 , Shinyoung Park 1 , Hyesung Kim 1 , Hyun Ah Jung 1
1 , Kangwon National University, Chuncheon Korea (the Republic of)
Show AbstractNano-inspired polymeric non-woven meshes were prepared by electrospinning for potential application of efficient gene delivery at wound sites. A matrix metalloproteinase (MMP) family is a hydrolytic enzyme highly expressed in diabetic ulcers to facilitate cellular migration during wound healing process. In this study, poly(ε-caprolactone)-poly(ethyleneglycol)[PCL-PEG] block copolymer was electrospun to non-woven and nanofibrous structures. In order to obtain controlled release of therapeutic DNA from nanofibrous scaffolds, a MMPs-specific peptide, DGPLGVC was employed as a MMP-cleavable linker between electrospun nanofibers and cationic polymers for gene delivery vehicles. PCL-PEG block copolymer dissolved in an organic solvent mixture (10% (w/v)) was electrospun to prepare nanofibers. The amount of surface-exposed amine groups on the nanofibers were quantitatively measured by fluorescamine assay. A primary amine group on the surface the electrospun nanofibers was reacted to a terminal carboxyl group of MMPs-specific peptide in 0.1M phosphate buffer. For conjugation of PEI, PEI was activated with SPDP for 30min and peptide-immobilized nanofibers were subsequently mixed to conjugate thiol groups of the peptide to SPDP-activated PEI. The reaction was performed at room temperature for 12h. The morphology of PCL-PEG electrospun nanofibers was observed by SEM, suggesting that the average diameter was approximately 900nm. As a result of fluorescamine assay, the amount of exposed amine groups on the fibrous meshes was 0.387nmol/mg, suggesting that 3~4% amine group of total amount of primary amine groups was exposed. PEI-conjugation to the nanofibers was confirmed by XPS. Survey scans spectra of C1s, O1s, and N1s confirmed that PEI density on the PEI-nanofiber was 0.384nmol/mg, suggesting that 99.2% of the exposed amines participated in the reaction. Cationic polymer-immobilized electrospun nanofibers are expected to accelerate diabetic wound healing and hold a promising candidate for dermal gene delivery.
9:00 PM - VV7.17
Magnetite Nanoparticles in Microsphere for Intestinal Delivery.
Hyuk Sang Yoo 1 , Ji Suk Choi 1 , Shinyoung Park 1 , Hyesung Kim 1 , Hyun Ah Jung 1
1 , Kangwon National University, Chuncheon Korea (the Republic of)
Show AbstractMagnetite nanoparticles are widely employed as super eminent contrast agents for magnetic resonance imaging (MRI). However, magnetite nanoparticles are easily degraded in acidic solutions and therefore cannot be employed for peroral delivery. In the current study, amphiphilic polymer-stabilized magnetite nanoparticles were prepared for efficient encapsulation within pH-sensitive microspheres. A di-block copolymer composed of PCL and methoxy PEG (mPEG-PCL) was dissolved in dichloromethane and FeCl2/FeCl3 in aqueous phase was subsequently added to the organic phase. Ammonium hydroxide solution (NH4OH) was slowly added to mixture with a vigorous stirring for preparation of magnetite precipitates with the block copolymer. Eudragit L100-55, pH-sensitive polymethacrylate polymer, and the mPEG-PCL-stabilized magnetic nanoparticles in a methanol/acetone mixture were slowly poured into mineral oil with 1% Span83 for water-in-oil emulsification. The microspheres was washed with n-hexane and freeze-dried. The magnetic properties of the mPEG-PCL-stabilized magnetite nano-aggregates were confirmed by a vibrating sample magnetometer (VSM), suggesting that incorporation of mPEG-PCL slowly decreased T2-relaxation time. Dynamic light scattering (DLS) showed incorporation of mPEG-PCL amphiphilic diblock copolymer prevented magnetite nanoparticles from being aggregated each other. Encapsulation efficiencies of the mPEG-PCL-stabilized magnetite nano-aggregate were also affected by the amount of mPEG-PCL in the aggregates. Therefore, the pH-sensitive microspheres encapsulating the magnetic nano-aggregates are expected to be a potential imaging agent for intestinal tracts.
9:00 PM - VV7.18
Enhanced Transport Properties and Structural Transformation of Silver Doped Hydroxyaptite.
Brajendra Singh 1 , Samayendra Kumar 2 , Bikramjit Basu 3 , Rajeev Gupta 1 2
1 Physics, IIT Kanpur, Kanpur, U.P., India, 2 Materials Science programme, IIT Kanpur, Kanpur, U.P., India, 3 Department of Metallurgical and Materials Engineering, IIT Kanpur, Kanpur, U.P., India
Show AbstractWe report the structural transformation and the transport studies of Silver doped hydroxyapatites Ca10-xAgx(PO4)6(OH)2 ( x= 0.0 to 1.5). A dramatic increase in the conductivity by two orders of hydroxyapatite in presence of silver ions is observed by impedance measurements in the temperature range 450oC to 650oC. The characteristic surface plasmon resonance effect is used to explore the presence of silver nano-particles, and Ag+ ions in hydroxyapatite using optical absorption measurements. The activation energy has been found to be 0.0756 eV in silver doped composition in comparison to 0.3916 eV for the parent hydroxyapatite. The sintering temperature dependence and compositional variation on the structural transformations from hydroxyapatite into tricalcium phosphate phases have been explored using Raman and X-ray diffraction techniques.
9:00 PM - VV7.19
Surface Charge Modifications of Silicon Nanowires for Electronic Nano-biosensor Applications.
H. Cho 1 , X. Li 1 , I. Baek 1 , S. Lee 1 , J. Yang 2 , C. Ahn 2 , A. Kim 2 , C. Ah 2 , C. Park 2 , G. Sung 2
1 Physics, Hanyang University, Seoul Korea (the Republic of), 2 Nano-Bio Electronic Devices Team, Electronics and Telecommunications Research Institute, Daejon Korea (the Republic of)
Show AbstractRecently silicon nanowires have attracted a lot of attention for the base material of FET-type biomolecular sensors enabling ultrasensitive, label-free, and real-time detection since their high surface-to-volume ratio makes the electronic transport characteristics highly sensitive to their surface environment. Unlike the ordinary MOSFET devices where silicon channel is well protected by the SiO2 layer with minimal interface states, the silicon biosensors often have their surface exposed to various environments during the fabrication and detection processes. Hence it is very important to investigate the surface modifications for each process and their influence on their transport characteristics. Starting from silicon-on-insulator(SOI) wafer with a 40 nm-thick top silicon layer of boron concentration ~ 5 x 10^17 cm-3, we fabricated silicon nanowires of varying width(100-300 nm) and length(2-20 μm) by using conventional CMOS technology and measured their transport characteristics on each step of the biosensor fabrication processes where the silicon nanowires have oxide-stabilized surface, bare surface, OH-modified surface, amine-modified surface and aldehyde-functionalized surface. The wires with oxide-stabilized surface as a point of reference showed reproducible and systematic behaviors with mobilities ranging from 200 to 500 cm2/Vs and surface charge density 2.5 x 10^11 cm-2 depending on wire dimensions. However, significant surface charge densities induced by the various surface modifications were observed ranging from 4.3 x 10^11 to 1.7 x 10^12 cm-2 and fluctuated with elapsed time. Characteristics of each surface states exhibited different behaviors and their properties are extensively elucidated.
9:00 PM - VV7.2
A Sensitive Method to Detect Escherichia Coli based on Immunomagnetic Separation and Real-time PCR Amplification of Aptamers.
Hye-Jin Lee 1
1 , Korea University, Seoul Korea (the Republic of)
Show AbstractAptamers, single stranded nucleic acids, provide a unique opportunity as amplifiable molecules using polymerase chain reaction (PCR) as well as recognition molecules like antibodies. We report a highly sensitive detection of E. coli by taking advantage of the aptamer amplification as well as the specific binding of aptamers onto E. coli. This unique approach consists of three steps. First, the target E. coli was captured by antibody-conjugated magnetic beads. Second, the RNA aptamers were bound onto the surface of captured E. coli in a sandwich way. Finally, the heat-released aptamers were amplified by using real-time reverse-transcriptase PCR (RT-PCR). The aptamer amplification in this approach has enabled a sensitive detection of microorganisms, such as the detection of ten E. coli in 1 ml sample. When compared to the amplification of nucleic acids extracted from the target microorganisms, this approach can not only prevent the loss of target nucleic acids during the sample preparation by obviating the necessity of cell lysis, but also provide an additional mechanism of signal amplification due to the binding of many aptamers to the surface of each E. coli. Detection of E. coli in this approach showed a wide dynamic range from 101 to 107 E. coli per ml, which can be explained by the exponential amplification of aptamers. This report has demonstrated, for the first time, the effective use of aptamer amplification in the development of sensitive microorganism detection. It is anticipated that the present approach will be easily expanded and employed in various types of microorganism detection.
9:00 PM - VV7.20
Spinning of Recombinant Silk Proteins for Technical Applications.
David Keerl 1 , John Hardy 1 , Thomas Scheibel 1
1 Lehrstuhl Biomaterialien, Universitaet Bayreuth, Bayreuth Germany
Show AbstractSpider dragline silk (used for the frame and radii of spider’s orb webs) is a natural fiber that has aroused great interest in science and industry due to its outstanding mechanical properties that have evolved during evolution. The research in our group is focused on the design and production of protein-based materials with well-controlled properties. We have successfully designed and produced a variety of engineered spider silk-like proteins (eADF3 and eADF4) based upon the primary sequence of the natural dragline proteins ADF3 and ADF4 from the Araneus diadematus spider. The engineered spider silk proteins can be modified on the molecular level using chemical methods for functionalization to optimize the biochemical and mechanical properties of the final product. Engineered spider silk proteins can be processed into fibers using different spinning methods, amongst which our group focuses especially on the technical realization of a biomimetic approach. Utilization of our biomimetic spinning technique allows for the production of silk fibers with well-defined mechanical properties, suitable for a variety of different applications. Spider silk proteins have great potential for technical applications and we believe that they will become important biomaterials in the near future. Here we present our latest results on our biomimetic fiber production process.
9:00 PM - VV7.21
Pulsed-DC Electrospray for Biopolymer Particle Production.
Cho Hui Lim 1 , Michael Mullins 1
1 Chemical Engineering, Michigan Technological University, Houghton, Michigan, United States
Show AbstractIn this work we are developing a simple and cost effective device that allows us to produce monodisperse particles and capsules with controllable size and adjustable sheath thickness on demand. To achieve this goal, we have combined the techniques of dual-capillary electrospray and pulsed electrospray. Dual-capillary electrospray has received considerable attention due to its ability to create core-shell structure in a single step. However, there are difficulties in controlling two simultaneous flows. Conventional electrospray has mainly been conducted using direct-current (DC) voltage or alternating-current (AC) voltage. It has rarely been conducted using pulsed high voltage. In contrast to the conventional electrospray, pulsed electrospray has the potential to provide greater control over the process variables. This work discusses the combination of the two techniques, and focuses on the effect of the pulsed voltage characteristics (e.g. pulse frequency, pulse amplitude, and pulse width) on the electrospray particle morphology and size distribution. The result for the techniques utilizing a biodegradable polymer, poly (L-lactide) PLLA, which is useful for biomedical applications, is presented. Some important parameters such as polymer concentration, organic solvent, feed flow rate, distance between the spray head and the collector, spray head, and collector were selected based on the previous study on DC electrospray and pulsed electrospray. The pulse frequency was varied from 1 Hz to 100 Hz. The pulse amplitude was adjusted in order to operate in a periodic cone-jet mode. Three different pulse widths were examined at each pulse frequency. The viscosity and electrical properties of the working fluid were determined before each experiment. The particles were collected either as a dispersed phase in a grounded liquid bath or on a solid collection electrode, and were then characterized by Zetasizer Nano ZS, field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). Particles were successfully produced by pulsed voltage with the pulse frequency of 10 Hz or lower. The average particles’ diameter was in the micrometer scale without the use of any additives to increase the electrical conductivity of the working fluid. The particles surface morphology and conformation differ considerably from those produced in a continuous DC electrospray.
9:00 PM - VV7.22
Controlled Enhancement of Neuronal Branching on Patterned Nanostructured TiOx/BSA Surfaces.
Ajay Singh 1 , Varun Vyas 1 , Cristina Lenardi 1 , Lasma Gailite 1 , Paolo Milani 1
1 Physics, CIMAINA, Milan, Lombardia, Italy
Show AbstractIt has been well established that cells receive chemical signals through the action of ligands binding to membrane and cytoplasmic receptors; it is becoming increasingly important to study the effect of physico-chemical properties of cell microenvironment on cellular morphology and cell functions (1). In a classical study, Webb et al had shown that differences in surface charged functional groups and wettability has significant effect on NIH 3T3 fibroblast attachment, spreading, and cytoskeletal organization (2). Further studies have continued to explore the effects of cell-surface interactions on cellular behavior but very few have been dedicated to titania, in particular nanostructured (ns) TiOx (3). Past studies were limited to bulk coated nanostructured thin film-cell surface interactions, without considering the fabrication of micropatterns of ns-TiOx with spatial distribution of surface charge/roughness and hydrophilic/hydrophobic patterns; however surface properties of cell culture substrate may have a profound effect on cell mechanobiology that regulates cell function in vitro (2). Ns-TiOx-cell interactions studies were carried out on non-neural cells and exploring substrate specific physico-chemical properties on neural cell functions; such as differentiation are of great importance in neurobiology.We propose a facile technique for the design of hydrophilic titanium oxide nanopatterns over hydrophobic bovine serum albumin micropatterns based on nanosphere lithography (NSL), in order to examine the effect of differential surface wettability on neuronal cell differentiation. The studies of PC12 cell differentiation result in a remarkable enhancement of neuritogenesis in terms of number of neurites per cell as well as the length of axon. The increase of the two differentiation parameters was statistically approved, confirming the suitability of the novel technique for cell substrate microfabrication. Such microengineered surfaces that induce neuritogenesis through wettability effects in addition to neurotrophic factors have perspectives in high throughput screening and living cell microarray technologies (4).1. Colpo P, Ruiz A, Ceriotti L, Rossi F. Surface Functionalization for Protein and Cell Patterning. Adv Biochem Eng Biotechnol. 2009 May 21. [Epub ahead of print].2. Ken Webb, Vladimir Hlady, and Patrick A. Tresco. Relative importance of surface wettability and charged functional groups on NIH 3T3 fibroblast attachment, spreading, and cytoskeletal organization. J Biomed Mater Res. 1998 September 5; 41(3): 422–430.3. J. He, W. Zhou, X. Zhou, X. Zhong, X Zhang, P. Wan, B. Zhu, and B. Chen. The anatase phase of nanotopography titania plays an important role on osteoblast cell morphology and proliferation. Journal of Materials Science: Materials in Medicine 2008;19(11):3465-3472.4. Dragunow M. High-content analysis in neuroscience. Nat Rev Neurosci. 2008;9(10):779-88.
9:00 PM - VV7.23
Metal Oxide Based Antigen Nanocarriers for Efficient Cross-priming of Antigen Specific T Cells.
Haiyan Li 1 , Yuhuan Li 2 , Puiyi Pan 2 , Yan Zhang 2 , Miach Eastman 1 , Jun Jiao 1 , Hong-ming Hu 1 2
1 Department of Physics, Portland State University, Portland, Oregon, United States, 2 Laboratory of Cancer Immunobiology, Robert W, Franz Cancer Research Center, Earle A, Chiles Research Institute, Providence Portland Medical Center, Portland, Oregon, United States
Show AbstractCross-priming plays a central role in the generation of adaptive cell-mediated immune responses to infectious pathogens and malignancies. Here, we examine the potential of metal oxide nanoparticles as antigen carriers to enhance antigen cross-presentation for robust activation of cytotoxic T lymphocytes. Model antigen OVA was conjugated to the surface of functionalized TiO2 nanoparticles and Fe2O3 nanoparticles via chemical ligation. Dendritic cells were cultured with titrated amount of OVA coated nanoparticles or soluble OVA and used to stimulate naïve OT-I transgenic T cells that specifically reactive to the SIINFEKL peptide derived from OVA proteins. Flow cytometry was used to measure the CD8+ T cell proliferation. Our data showed that the in vitro cross-presentation efficiency of TiO2 nanoparticle-OVA was one order of magnitude higher than that of OVA coated Fe2O3 nanoparticles or soluble OVA. The OVA-specific CD8+ T cell population, both in the spleen and in the lymph node, was monitored after adoptive transfer of naïve OT-1 spleen cells into C57BL/6 mice and subcutaneous injection of OVA coated nanoparticles and soluble OVA. In accordance with the in vitro results, cross-presentation of OVA coated TiO2 nanoparticles but not Fe2O3 nanoparticles significantly enhanced CD8+ T cell proliferation in vivo. Since the sizes and antigen concentrations of TiO2 and Fe2O3 nanoparticle are similar, we hypothesize that the significant differences in the ability to promote cross-presentation is related to the nanoparticle surface chemistry that could greatly influence the antigen release after they were phagocytosized by dendritic cells. Our data point to possible approaches to enhance the ability of metal oxides to cross-present antigens by modifying the surface chemistry or physical trade of nanoparticles. Our results showed the great potential to utilize metal oxide for the development of vaccines for cancers and infectious diseases.
9:00 PM - VV7.24
Carcinogenic Cellular Responses to Functional Hyaluronic Acid Modified Surfaces.
Chia Chi Ho 1 , Laura Beasman 1 , Geoffrey Wang 1 , Sharon Gerecht 1
1 Chemical & Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, United States
Show Abstract
Background: Cellular microenvironment influences and regulates cellular functions and pathways. Specifically, it plays an important role in tumor progression. It is increasingly recognized that microenvironment rich in hyaluronic acid (HA) assists cancer invasiveness and metastasis, both of which are the hallmarks of malignancy. HA facilitates these malignant traits of cancer by enhancing growth and angiogenesis. HA is an anionic, non-sulfated glycosaminoglycan that distributes ubiquitously in the extra cellular matrix, and it has been known to co-regulate gene expression, proliferation, motility, adhesion, and signaling. Hyaluronic acid has two primary receptors: CD44, which acts to affect cellular adhesion and proliferation; and CD168, which is involved in migration and mitosis. Hypothesis: We hypothesized that HA-modified surface provides a functional microenvironment for cellular studies of cancer cells.Aim: We aimed to create functional surfaces that present HA in distinct patterns, providing spatio-temporal surface cues, on glass substrates.Methods: The microcontact printing (μCP) method was applied to create HA- patterned surfaces. Breast cancer cell line HTB-26 and colon cancer cell line LS174T, were used to demonstrate interaction with functional HA surfaces. To show interactions with the surface, immunofluorescence staining for HA receptors, CD44 and CD168, and scanning electron microscopy were preformed.Results: We first examined the expression of CD44 and CD168 in breast and colon cancer cells. We found that both cell lines express CD44 on the membrane while CD168 was expressed within the nuclei. When cultured on the HA-patterned surfaces, breast and colon cancer cells were attached within 24hours while cell growth was observed within 48hours. Moreover, fluorescent immunostaining for CD44 demonstrated expression on adhered breast and cancer cells. Scanning electron microscopy verified cell attachment onto the pattered surfaces, and further revealed extensions present on the periphery of the cancer cells, indicating their intrusive nature. Conclusions: Our observations indicate that HA patterned surfaces support cancer cell adhesion and growth, suggesting the role of HA in tumor development. Our engineered surfaces provide a means to study carcinogenic response to environmental cues.
9:00 PM - VV7.25
Design of a Targeted Virus-like Particle (VLP) Carrier for Delivery of Nanoparticles, Chemotherapeutic Agents, and siRNA to Human Cancer Cells.
Carlee Ashley 1 , David Peabody 2 , C. Jeffrey Brinker 1 2 3
1 Chemical Engineering, University of New Mexico, Albuquerque, New Mexico, United States, 2 Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, New Mexico, United States, 3 Self-Assembled Materials, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractVirus-like particles (VLPs) have received considerable attention in recent years for their potential in drug delivery, vaccine development, gene therapy, and materials science applications. VLPs of MS2 bacteriophage have been successfully produced in vivo and in vitro, and their protein capsids are highly tolerant of peptide insertions. Furthermore, several conjugation chemistries are available that enable modification of the interior and exterior capsid surfaces with various organic and inorganic compounds. To this end, we have displayed a targeting peptide (SP94) identified by phage display to have a high affinity for human hepatocarcinoma on MS2 VLPs. We have demonstrated that VLPs bearing at least 60 copies of the SP94 peptide bind to Hep3B and HepG2 with high specificity (Kd = 0.93 nM and 3.11 nM, respectively) due to multivalent display of the targeting peptide. We have used confocal fluorescence microscopy to show that, while targeted VLPs are rapidly endocytosed by Hep3B and routed to lysosomes, they are not internalized by human hepatocytes. We have encapsidated gold and iron oxide nanoparticles, quantum dots, chemotherapeutic agents, and siRNA within MS2 VLPs by chemically conjugating them to the pac site, a specific RNA sequence present in the bacteriophage genome that initiates capsid assembly. We have established that targeted MS2 VLPs loaded with these types of cargo are internalized by Hep3B cells and release their cargo into the cytosol within four hours. Targeted MS2 VLPs loaded with doxorubicin or camptothecin cause an 80% loss in Hep3B viability within 72 hours but have very little affect on the viability of hepatocytes. Targeted MS2 VLPs that encapsidate a cocktail of siRNA, which silences expression of cyclin A2, cyclin B1, and cyclin B2, induce apoptosis in Hep3B cells within eight hours but do not affect the viability of hepatocytes even after a ten-day incubation period. Thus, we have successfully demonstrated that VLPs of MS2 bacteriophage can be used to specifically deliver a variety of cargo to human hepatocarcinoma cells in vitro. We are currently extending our work with targeted VLP-based delivery to prostate cancer cells. Prostate cancer displays prostate-specific membrane antigen (PSMA); PSMA is only expressed by certain prostate cancer cell lines and by the neovasculature of tumors, making it an ideal target for active delivery. Furthermore, the growth of prostate cancer cells, even those that are hormone insensitive, depends on the presence of the androgen receptor (AR). We are, therefore, using PSMA ligands, including a monoclonal antibody, folate, and peptides identified by phage display, to target MS2 VLPs to prostate cancer cells. We have, furthermore, identified siRNA that silences expression of the androgen receptor, thereby inducing apoptosis, and are investigating the possibility of using MS2 VLPs to deliver siRNA to prostate cancer in vitro and in vivo (xenograft and orthotopic mouse models).
9:00 PM - VV7.26
Boronic Catechol Esters of Bortezomib as Prodrugs for Targeted Anti-Cancer Therapy.
Jing Su 1 , Kvar Black 1 , Vincent Cryns 2 3 , Phillip Messersmith 1 3
1 Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, United States, 2 Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States, 3 Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois, United States
Show AbstractBortezomib is a dipeptide boronic acid analogue with antineoplastic activity. By reversibly inhibiting the 26S proteasome and blocking targeted proteolysis, bortezomib disrupts various cell signaling pathways, leading to cell cycle arrest, apoptosis, and inhibition of angiogenesis. In vivo, bortezomib delays tumor growth and enhances the cytotoxic effects of radiation and chemotherapy. Currently this highly potent anticancer drug is only being applied in treatment of multiple myeloma cancer because of the much greater sensitivity of myeloma cells to proteasome inhibition by bortezomib compared with normal cells and most other cancer cell lines. The mechanism for this specificity is poorly understood. We hypothesized that targeted delivery of bortezomib to specific cancer cells should increase the uptake and thus the proteasome inhibitory effects of the drug, as well as decrease the side effects on normal cells. The high affinity of boronic acid toward the catechol moiety can be exploited to form a catechol ester of bortezomib as prodrug. Furthermore, the bortezomib-catechol-complex can dissociate in the acidic intracellular environment in cancer cells and thus release bortezomib for proteasome inhibition selectively in these cells. Such prodrugs can also be easily conjugated to various drug carriers such as dendrimers, nanoparticles and etc. for controlled anti-cancer drug delivery. For the first time we report the synthesis and characterization of boronic ester prodrugs formed from bortezomib and catechol-containing molecules. The pH-sensitive dissociation of bortezomib-catechol conjugates was studied by fluorescence assays and boron11 NMR. The bortezomib-catechol conjugate was incoporated into PEG-containing macromolecules terminated with ligands for targeting human breast cancer and ovarian cancer cell lines. In the future, the pro-apoptotic effects of bortezomib-catechol conjugates on cancer cells will be evaluated by annexin V and caspase activity assays compared to those of bortezomib alone. Our approach of using a catechol ester of bortezomib as prodrug may be widely applicable for targeted drug delivery to specific tumor tissues and for tuning the pharmacokinetics of bortezomib in anti-cancer therapy.
9:00 PM - VV7.28
Analysis of Nano-properties of Osteroporosis Human Compact Bone by Using Small Angle Neutron Scattering and Nanomechanical Tests.
Yong Choi 1 , Eun J. Shin 2 , Baik S. Seong 2 , Doo J. Paik 3 , Hanson Fong 4 , Mehmet Sarikaya 4
1 Electronic Materials Engineering, Sunmoon University, Asan, Chungnam, Korea (the Republic of), 2 HANARO, KAERI, Daejeon Korea (the Republic of), 3 College of Medicine, Hanyang University, Seoul Korea (the Republic of), 4 GEMSEC, University of Washington, Seattle, Washington, United States
Show AbstractHuman bone is a hierarchical composite with significant structural features at the nanometer-scale containing principally collagen and mineral hydroxyapatite. The nanostructure in bone depends, in the part, on nutrition, external load and growth history. In this study, we discuss the results of small angle neutron scattering (SANS) and nano-mechanical tests to compare nanostructural effects with their mechanical properties of normal and osteoporosis human compact bones. Specifically, we use jaw bone because it is a relatively large plate bone with relatively low stress distortion among the many bones in the human body. The SANS profiles reveal the directional and regular distribution of plate-like bone crystals, lacuna rough surface and nano-sized canaliculi in the compact bone. We also find that the osteoporosis human bone has fewer bone crystals, lacuna and canaliculi than normal human bone. Microstructure observations by TEM and SEM also support these SANS evaluation. Nano-indentation measurement of the human bone samples, in particular modulus and hardness, reveal interesting characteristics, in particular, in the osteoporosis human bone. Based on the structure-property correlations, both normal and diseased bones will be analyzed for strength and toughness via nanocomposite rules of mixtures.
9:00 PM - VV7.29
Preparation of Monodisperse Biodegradable Polymer Microparticles Using a Microfluidic Flow-focusing Device for Controlled Drug Delivery.
Qiaobing Xu 1 , Hashimoto Michinao 2 , Tram Dang 1 , Todd Hoare 1 , Daniel Kohane 3 , George Whitesides 2 , Robert Langer 1 4 , Daniel Anderson 4
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Chemistry, Harvard University, Cambridge, Massachusetts, United States, 3 Anesthesiology / Critical Care Medicine, Children's Hospital Boston, Boston, Massachusetts, United States, 4 David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractDegradable microparticles have broad utility as vehicles for drug delivery and form the basis of several FDA-approved therapies. Conventional emulsion-based methods of manufacturing produce particles with a wide range of diameters (and thus kinetics of release) in each batch. We have developed a method to fabricate monodisperse, drug-loaded microparticles from biodegradable polymers using the microfluidic flow-focusing (FF) devices and the drug delivery properties of those particles. Particles were engineered with defined sizes, ranging from 10 μm to 50 μm. These particles were nearly monodisperse (polydispersity index = 3.9 %). We incorporated a model amphiphilic drug (bupivacaine) within the biodegradable matrix of the particles. Kinetic analysis showed that the release of drug from these monodisperse particles was slower than that from conventional methods of the same average size but a broader distribution of sizes and, most importantly, exhibited a significantly lower initial burst than that observed with conventional particles. The difference in the initial kinetics of drug release was attributed to the uniform distribution of drug inside the particles generated using the microfluidic methods. These results demonstrated the utility of microfluidic FF for the generation of homogenous systems of particles for the delivery of drugs.
9:00 PM - VV7.3
Low-Temperature ZnO Atomic Layer Deposition on Biotemplates: Flexible Photocatalytic ZnO Structures from Eggshell Membranes.
Seung-Mo Lee 1 , Gregor Grass 2 , Gyeong-Man Kim 3 , Christian Dresbach 4 , Lianbing Zhang 1 , Ulrich Goesele 1 , Mato Knez 1
1 , Max Planck Institute of Microstructure Physics, Halle(saale) Germany, 2 School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, United States, 3 , Fraunhofer Institute for Cell Therapy and Immunology, Leipzig Germany, 4 , Fraunhofer Institute for Mechanics of Materials, Halle(saale) Germany
Show AbstractHighly flexible and macroporous thin membranes of ZnO with a strong photocatalytic effect were prepared by using the inner shell membrane (ISM) of a naturally available avian eggshell as template for a low-temperature ZnO atomic layer deposition (ALD). Contrary to most of the materials deposited by ALD at low temperatures, the deposited ZnO is not amorphous but shows a polycrystalline nature and thus adds certain functionalities to the template. Here in order to clarify large technical benefit and general applicability of the ZnO structures deposited at low temperatures, two different membranes on which TiO2 or ZnO are deposited under similar processing conditions were prepared and then comparative studies in terms of crystallographic features, mechanical/thermal stability and bactericidal efficiency were performed. Both membranes (ZnO and TiO2 coated) clearly exhibited bactericidal effects as well as mechanical flexibility / thermal stability even at relatively high temperatures. However, the ZnO membranes prepared even at fairly low temperatures (~100°C) exhibited polycrystalline phases and showed a comparatively good bactericidal efficiency as well as higher mechanical flexibility, as compared to TiO2 coated membranes. This study shows the big benefit of low-temperature ZnO ALD i.e., the thermally non-destructive nature, thereby preserving mechanical stability and native morphologies of the used templates, together with added functionality (bactericidal effects).
9:00 PM - VV7.30
Functionalizing GUV by Nucleic Acid Hybridization in Microfluidics: Principles and Applications.
Jian Xu 1 , Paul Beales 1 , Kyle Vanderlick 1
1 School of Engineering, Yale University, New Haven, Connecticut, United States
Show Abstract Synthetic cells have received enormous attention as the potential platforms for exploiting the functions of natural cells, such as energy conversion and cell signaling; synthetic cells can be made of vesicles at the comparable dimensions to the natural cells, such as giant unilamellar vesicles (GUVs), functionalized with appropriate molecular components. Functionalized lipid vesicles are also of great interest in immunotherapy: the efficient T-cell stimulation and proliferation in response to artificial antigen presenting cells (aAPCs) is a primary goal for the adoptive immunotherapy to cancers; aAPCs can be made of GUVs functionalized with antibodies or ligands. A general challenge of the functionalization of GUVs is how to coat the vesicles without having floating antibodies or drugs in the solution environment. Here we show a microfluidic platform for effective GUV functionalization via nucleic acid hybridization. The hydrophobic modification of DNA makes it possible to encode the vesicles and lipid bilayers with various DNA sequences. The unique properties of DNA strands, including base pairing and reversible hybridization, are employed to mediate the interactions between GUVs and planar lipid bilayers. Manipulating the solutions in channels with dimensions of tens of microns provides a controllable environment to functionalize the GUVs with high spatial resolution, to interrogate single GUVs and to statistically study their group behavior. We investigate DNA mediated GUV interactions with planar lipid bilayers formed in microfluidic channels: by using the microfabricated mechanical valves, we effectively immobilize, functionalize and release DNA-encoded lipid vesicles from the planar lipid bilayers; our experiment shows that the vesicles are uniformly functionalized with no floating ligands. By the partitioning behavior of cholesterol modified DNA in multiple lipid phases, we construct a platform of GUVs with oriented phase separations, which have potential applications in quantitative investigation of the behavior of various cell components among different phases.
9:00 PM - VV7.31
Polymer-lipid Nanocarrier for the Controlled Co-delivery of Drugs and Genes.
Junping Wang 1 , Emily Woo 1 , Anthony Lepre 1 , Xiaojun Yu 1
1 , Stevens Institute of Technology, Hoboken, New Jersey, United States
Show AbstractMany co-delivery systems of both drug and gene have been developed in recent years especially in some cancer therapy area. It has been reported that the co-delivery of both p53 gene and anticancer drug could increase the gene expression level as well as improve the cytotoxicity of the anticancer drug. However the application of this delivery system was hindered by the inefficiently loading and burst release of the hydrophilic drug, and low gene transfection efficiency. The stability is also an issue for many lipid based delivery system.We have developed a polymer-lipid nanocarrier (PLN) with dual functions to load both the protein and plasmid DNA. The new formulation of cationic PLN for both protein and gene delivery was fabricated by solvent evaporation technique. The PLNs were formulated by mixing poly(lactic-co-glycolic acid) (85:15) (PLGA) as a core, cholesterol, 1,2-Dioleyl-3-trymethylammoniumpropane (DOTAP) and Tween 80 as the layer. The characterizations of this PLN include size and zeta potential measurement and stability study. Bovine serum albumin (BSA) was used as the model hydrophilic drug to study the loading efficiency and the release profile of this PLN. The transfection efficiency of this PLN was evaluated by transfect plasmid DNA (pEGFP)/PLNs complexes into human osteoblast cells in comparison with the commercially available lipofectine. Cell viability was tested via MTS assay. The results have demonstrated that this PLN had an average size of 84.9±11.8 nm, and a zeta potential of 45.84±0.15mV. As a hydrophilic drug carrier, PLN did not show any burst release in the beginning and the release profile was sustained which is superior to the traditional PLGA nanoparticles. The nano-size and cationic surface property allow the nanostructure to have comparable transfection efficiency with the commercial available lipfectin. The stability study showed that after 6 month stock in the fridge, the size and zeta potential of PLNs did not change significantly, and no aggregation formed. These results indicate that the novel polymer-lipid nanocarrier might serve as a promising carrier for dual delivery of proteins and genes for enhanced cancer therapy and other biomedical applications.
9:00 PM - VV7.32
Layer-by-layer Assembled Polymer Coatings for Anti-fog Applications.
Nurxat Nuraje 1 , Girma Endale 1 , Robert Cohen 1 , Michael Rubner 1
1 Materials Science and Engineering and Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show Abstract Fogging is a phenomenon of forming small droplets of water on transparent surfaces, which reduces the visibility of medical devices, vehicle windows, airplane windshields, optical wear (eye glasses, goggles, and face shields), binoculars and other optical devices. Thus, the development of long lasting, mechanically durable anti-fogging films is greatly desired by many industries. In this work, we studied a new type of hydrophilic coating that could be applied to many surfaces to produce a long-lasting anti-fog effect. The coating provides unique properties as a result of a molecular-level blend of two hydrophilic polymers, such as natural (chitosan and carboxyl methyl cellulose) and synthetic (poly(ethylene oxide) grafted poly(acrylic acid) copolymers) via a layer-by-layer (LBL) assembly process. To improve mechanical durability of the films on glass substrates, the surface was modified via self-assembly of epoxy functionalized silane molecules. Cross-linking chemistry was then applied to improve the mechanical robustness of the LBL assembled polysaccharide films on the surface. The LBL films were characterized using several techniques, such as profilometery (PL), spectroscopic ellipsometry (EL), contact angle measurement (CA), and atomic force microscopy (AFM). The anti-fog properties of the films were evaluated by aspiration test, optical test and humid chamber test. Test results showed that the LBL films were highly robust and exhibited permanent antifogging properties.
9:00 PM - VV7.33
Syntheses of Hydroxyapatite Bioceramic Nanospheres Through a Facile Sol-gel Method.
Kai Li 1 , Sie Chin Tjong 1
1 physics and material science, City University of Hong Kong, Hong Kong China
Show AbstractStoichiometirc bioceramic hydroxyapatite (Ca5(PO4)3(OH), HA) nanospheres with uniform dimension distribution were synthesized through a convenient sol-gel routine. The formation of HA nanospheres involved the reaction between (NH4)2HPO4 and CaCl2 in ethanol/PVA aqueous sol-gel system, with ammonia solution adjusting under neutral environment. The as-synthesized products were characterized by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR). FESEM images showed the as-synthesized products exhibited spherical morphology, having a uniform diameter of 50~60nm; XRD and FTIR patterns indicated the nanospheres displayed typical crystalline diffraction peaks and main vibration bands of HA respectively; EDAX result confirmed the stoichiometric composition with Ca/P molar ratio approaching to 5:3. Besides the apatite formation after 3-week immersion in Simulated Body Fluid (SBF) could be observed on compact discs composed of the nanospheres sintered at 550°C, which could be an indication of good biocompatibility.
9:00 PM - VV7.4
Formation of Calcium Carbonate using Peptides and Proteins in the Shell of Pearl Oyster, Pinctada fucata.
Michio Suzuki 1 , Kazuko Saruwatari 1 , Hiromichi Nagasawa 2 , Toshihiro Kogure 1
1 Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo Japan, 2 Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo Japan
Show AbstractThe shell of pearl oyster, Pinctada fucata, consists of two layers with different structures: nacreous and prismatic layers. Both layers are composed of calcium carbonate (CaCO3) crystals and organic matrices. Organic matrices form framework walls or sheets which are made of a chitin sheet at the center part and proteins covering the sheet [1]. Previous works [2] suggested that these proteins interact with CaCO3 crystals to regulate them. In order to understand the functions of these proteins in detail, we have identified two new proteins in the shell (Prismalin-14 from the prismatic layer and Pif from the nacreous layer) and performed in vitro experiments of CaCO3 growth with these proteins. Prismalin-14 consists of 105 amino acid residues containing N- and C-terminal Asp-rich regions. We prepared recombinant peptides of Prismalin-14 (rPrismalin-14) and CaCO3 crystals were precipitated from the solution with them. The overall morphology of the crystals was rhombohedral as in the control experiment, but the surface became rough and minute steps were formed. To clarify the contribution of the N- and C-terminal Asp-rich regions, rPrismalin-14 without N- and C-terminal Asp-rich regions (rPrismalin-14 ΔNΔC) were prepared and subjected to the similar experiment. rPrismalin-14 ΔNΔC has less activity than rPrismalin-14. These results indicate that Prismalin-14 interacts with calcium carbonate crystals via its Asp-rich regions. Pif cDNA encodes a precursor protein, which was cleaved to Pif 97 (525 a.a.) and Pif 80 (460 a.a.) post-translationally. Pif 97 has VWA domain which binds other proteins, and chitin-binding domain. Pif 80 includes 28.5% Asp residues. The fraction containing Pif 97 and Pif 80 separated by gel filtration HPLC was applied on the β-chitin sheet or α-chitin-coated glass plate and incubated in a CaCO3 supersaturated solution. Calcite and vaterite platy crystals were formed on the β-chitin sheet. On the other hand, some aragonite crystals were formed on the α-chitin-coated glass plate. These aragonite crystals were formed between the chitin membrane and glass plate. They were single-crystalline with the c-axis perpendicular to the glass plate. This feature is very close to that of the aragonite crystals in the nacreous layer.[1] Levi-Kalisman, Y. et al. (2001) J. Struct. Biol. 135, 8[2] Addadi, L. et al. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 4110
9:00 PM - VV7.5
Self-assembly of Thermally Responsive Micellar Nanoparticles from Amphiphilic Diblock Polypeptides.
Wookhyun Kim 1 , Elliot Chaikof 1
1 Surgery and Biomedical engineering, Emory University/Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractA variety of opportunities exist for micelles or vesicles produced through self-assembly of amphiphilic block polypeptides, particularly in drug delivery and targeted bioimaging. We report the synthesis of two amphiphilic diblock polypeptides (ADP1 and ADP2) based on elastin-mimetic polypeptide (EMP) sequences through genetic engineering. A peptide sequence containing consecutive cysteine residues was incorporated at the block interface to stabilize micellar structure. The formation and morphology of protein nanoparticles was investigated by NMR and fluorescence spectroscopy, as well as by multi-angle dynamic light scattering, atomic force and transmission electron microscopy. The critical micelle concentration of ADP1 and ADP2 was 2.0 and 3.5 μM, respectively, and hydrophobic fluorescent molecules could be easily encapsulated within the hydrophobic micelle core. Our results demonstrate the generation of a versatile new class of protein-based nanoparticles with significant potential for controlled drug delivery.
9:00 PM - VV7.6
Fabrication of Three-dimensional Scaffolds with an Inverse Opal Structure and Their Applications in Tissue Engineering.
Sungwook Choi 1 , Jingwei Xie 1 , Yu Zhang 1 , Younan Xia 1
1 Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, United States
Show AbstractScaffold with an inverse opal structure can be considered as an ideal system for tissue engineering because of their highly uniform pore size and regular three-dimensional interconnectivity. The procedure for fabricating the inverse opal scaffold includes three major steps: production of uniform microspheres using a fluidic device; fabrication of a cubic close packed (ccp) lattice; and development of an inverse opal structure by infiltration, freeze-drying, and selective dissolution of the ccp lattice template. Both uniform poly(caprolactone) and gelatin microspheres have been used as the template for the fabrication of hydrophilic chitosan and hydrophobic poly(D,L-lactide-co-glycolide) scaffolds, respectively. The resulting scaffolds exhibited a uniform pore size, interconnected network of pores, and nanostructured surface. Confocal microscopy imaging and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for cultured samples of preosteoblastic cells (MC3T3-E1) confirmed the penetration and proliferation of the cells throughout the 3D scaffold in 3 weeks.
9:00 PM - VV7.7
Protein Patterning Through Bio-compatible Orthogonal Processing.
Priscilla Taylor 1 , Jin-Kyun Lee 2 , Margarita Chatzichristidi 3 , Kari Midthun 1 , Alexander Zakhidov 2 , Barbara Baird 1 , George Malliaras 2 , Christopher Ober 2
1 Chemistry and Chemical Biology, Cornell University, Ithaca, New York, United States, 2 Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 3 Chemistry, University of Athens, Zografou 15771 , Attiki, Greece
Show AbstractThe ability to define multiple biomolecules on a single surface in high resolution while retaining their functionality is integral to the development of micro- and nanoscale bio-devices. However, conventional patterning methods require the use of organic solvents and imaging materials, which are damaging to delicate biomolecules. Proteins and other biomolecules require bio-compatible patterning conditions. We have developed an orthogonal patterning process, utilizing fluorinated solvents and imaging materials, which we have shown to be completely benign to biomolecules. This process does not disturb or adversely affect previously-deposited protein layers and so allows for patterning of multiple biomolecules on a single substrate.We describe the synthesis of a fluorinated imaging material, soluble in segregated hydrofluoroethers (HFEs), both of which we demonstrate to be benign to biomolecules. Furthermore, by applying this process to imprint lithography, we circumvent the need for the irradiation used with conventional photolithography, which can be very damaging to biomolecules. We demonstrate the implementation of this orthogonal system to the high-resolution patterning of proteins by imprint lithography.
9:00 PM - VV7.8
Fabrication of Microneedle PDMS Mold using Laser Writer.
Hyung-Jun Kim 1 , Bong-Jin Kim 1 , Sung-Mok Jung 1 , Hyun ho Lee 1
1 Chemical Engineering, Myongji Univ., Yongin-si, Gyoonggi-do, Korea (the Republic of)
Show AbstractRecently, there have been many interests on the fabrication of microneedle, which can improve drug delivery through dermal skin. Advantage of using microneedle includes reduction of pain, long-term sustainability, and the delivery efficiency. Numerous methods to penetrate drugs effectively have been developed so far using micro-fabrication processes. For example, silicon or polymer are micro-fabricated using lithography and reactive ion etching, etc to fabricate microneedle mold-master, which can be a template for a soft mold of PDMS. The mold of PDMS is usually a mold for drug, which can be cast as a concrete microneedle-shaped drug. In this paper, a simple laser writer was adoped to fabricate a PDMS microneedle mold. The laser patterned PDMS mold does not require a precedent template, which requires many micro-fabrication steps. It has efficiency without using photolithography, repeatability in manufacturing, and simplicity in process. By controlling laser power, writing speed, and PDMS compositions, needle-holes as small as 150m at bottom could be fabricated. The depth of needles can be ranged from 100m to 1.5 mm. In addition, microneedle templates, which were stacked SU-8 with gradually reducing the size of stacking (the size of peak stack is less than 20m), are introduced and compared with the laser fabricated microneedles. Then, CMC (Carboxymethyl Cellulose) solution was applied on laser fabricated or SU-8 stack type PDMS molds to investigate their characteristics for drug delivery. The results demonstrate the feasibility of using laser writer for successful application to cost-effective process.
9:00 PM - VV7.9
M13 Phage Engineering for the Selective Adsorption on the Substrate.
Yun Jeong Kim 1 , Dae Young Jeon 1 , So Jeong Park 1 , Kyung Hoon Hwang 2 , Chang-Hoon Nam 2 , Jeong Sook Ha 3 , Gyu Tae Kim 1
1 Electrical Engineering, Korea university, Seoul Korea (the Republic of), 2 Human Engineering Campus, Kist Europe, Saarbruecken Germany, 3 Chemical & Biological Engineering, Korea University, Seoul Korea (the Republic of)
Show AbstractThe M13 is a filamentous bacteriophage with surface active proteins which can be genetically modified to bind specific materials. The selective adsorption characteristics by the surface engineering can be applied to arrange the M13 phage according to the predefined patterns. The surface of wild type M13 phage is known to have negative charges. To increase the adhesion between M13 phage and Si/SiO2 substrate, we carried out the surface treatments on the Si/SiO2 substrate by the 3-aminopropyltriethoxysilane(APS) over 1 hour. The enhanced adhesion of M13 phages on the APS-treated substrates was observed and the electrical connection as a device configuration could be also made. The current-voltage characteristics were observed to be unstable depending on the different kinds of the treatments and the buffer solutions. The origin of the unstable electrical properties will be discussed from the point of the ionic contribution on the electrical currents.
Symposium Organizers
Roger Narayan University of North Carolina
Suwan Jayasinghe University College London
Sungho Jin University of California-San Diego
William Mullins Office of Naval Research
Donglu Shi University of Cincinnati
VV8: Processing of Next Generation Biomaterials and Medical Devices
Session Chairs
Suwan Jaysinghe
Roger Narayan
Friday AM, December 04, 2009
Room 202 (Hynes)
9:00 AM - **VV8.1
Tissue Response to Titanium Dioxide Nanotube Modified Surfaces.
Lars Bjursten 1 2 , Garrett Smith 2 1 , Seunghan Oh 2 4 , Lars Rasmusson 3 , Sungho Jin 2
1 , Lund University, Malmo Sweden, 2 , UCSD, San Diego, California, United States, 4 Department of Dental Biomaterials, College of Dentistry, Wonkwang University, Iksan Korea (the Republic of), 3 , Sahlgren's academy, Gothenburg Sweden
Show AbstractTitanium is a widely used biomaterial for oral implants, although it is susceptible to intra-oral bacteria and inflammatory reactions. In this project we explored the soft tissue response in rats as well as bone tissue response in the scull bone of rabbits to titanium dioxide (TiO2) nanotubes coated titanium implants and compared with a titanium implant covered with a naturally formed TiO2 on a mesoscale structured surface. Vertically-aligned nanotubes with a ~70nm inner diameter and ~250nm height were fabricated by electrochemical anodization on Ti disks (5mm Ø by 1.5mm height). Gritblasted implants with a typical roughness depth of ~2um were used as reference. Six rabbit received a total of 24 implants in the scull bone according to a procedure that was modified from a previously published procedure for implantation onto the tibia in rabbits (Bjursten et al, J Biomed Mater Res A. 2009 Apr 2, epub). Four disc-shaped implants are placed on planar surface on the bone with a teflon cover cap . The implants are spring loaded and held in place by brackets. After 8 weeks of healing the pull-out forces were measure. These were significantly higher for the nanotube covered surfaces compared to the controls (P<0.01)Twenty rats received each implant type in the abdominal wall. Tissues were removed en bloc after one or six weeks of healing. Histological evaluation showed that foreign body capsule thickness was significantly lower for the nanotube surface at one week (p<0.05) and six weeks (p<0.05) compared to the gritblasted surface. There was a significantly higher concentration (p<0.05) of ED1-positive cells per capsule area for the gritblasted compared with the nano surface at six weeks. The ED1-positive cells per capsule area for the nanotube surface decreased (p<0.02) between one and six weeks. Significantly lower NO activity, measured by presence of nitrotyrosine, (p<0.05) was found on the nanotube surface at one week. The reduced numbers of recruited macrophages, and less developed fibrotic capsule suggests that the nanotube-modified surface is beneficial for implants in contact with soft tissues. This may be due to the NO scavenging properties of TiO surfaces that is greatly increased by the nanotube structure. These findings may be significant for the interaction between titanium implants in soft tissue as well as bone tissue and provide a mechanism to improve future clinical implants.
9:30 AM - VV8.2
Enhanced Drug Delivery Properties of Porous Silicon: Towards Minimally Invasive Medicine.
Jennifer Andrew 1 , Elizabeth Wu 2 , Emily Anglin 1 , Lingyun Cheng 3 , William Freeman 3 , Michael Sailor 1 2
1 Chemistry and Biochemisty, University of California- San Diego, San Diego , California, United States, 2 Bioengineering, University of California- San Diego, San Diego, California, United States, 3 Shiley Eye Center, University of California- San Diego, San Diego, California, United States
Show Abstract“Side effects may include. . .” This disclaimer is ubiquitous in drug prescribing information and advertisements, and is a direct result of the limitations of current pharmaceutical technologies. Today, most medications are designed to be taken orally or intravenously; they then travel through the bloodstream, working systemically to treat a localized symptom or disease. This systemic treatment of disease reduces the efficacy of the drug and requires higher dosages to ensure the medicine reaches the desired area. These higher dosages increase the risks of unwanted side effects and toxicity. To overcome the limitations of current pharmaceutical technologies, biocompatible and biodegradable porous silica (SiO2)- based materials have been developed. These particles allow for high drug loading, controlled release, as well as a simple optical method for monitoring release in a clinical setting. The biocompatible porous SiO2 particles were prepared by the electrochemical etch and subsequent thermal oxidation of a single crystalline silicon wafer. The porous structure of the particles gives rise to an optical reflectance spectrum, which can be tuned by varying the etching conditions. As drugs are loaded in or released from the pores the optical reflectance spectrum changes, providing an optical method for monitoring drug release. Candidate drug molecules (bevacizumab, daunorubicin, doxorubicin), relevant to the treatment of both cancer and various ocular diseases, were subsequently loaded by electrostatic adsorption or covalent attachment. Covalent linkers with varying hydrophobic and hydrophilic moieties and molecular weights were utilized, and their effect on drug release was compared. The effects of porous SiO2 surface chemistry on drug loading and release was investigated. The bioactivity of the loaded drugs after release was also verified. An enzyme-linked immunosorbent assay (ELISA) was developed to verify the bioactivity of the protein drug bevacizumab, and a cell proliferation assay was used for both daunorubicin and doxorubicin. Drug molecules released from porous silica exhibit linear release profiles with no initial burst release. Drug release occurs primarily through the dissolution of the porous SiO2 matrix, this rate can be increased or decreased by using a more hydrophilic or hydrophobic covalent linker, respectively. Porous SiO2, therefore, provides a drug carrier that can be readily tailored to obtain a desired release rate, simply by modifying its surface chemistry for a range of therapeutic molecules.
9:45 AM - **VV8.3
Electrically Triggered Drug Delivery using Nanoporous Electrodes.
David Robinson 1 , Shaun Gittard 2 , Benjamin Jacobs 1 , Chung-An Max Wu 1 , Roger Narayan 2
1 Energy Nanomaterials, Sandia National Laboratories, Livermore, California, United States, 2 Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, United States
Show AbstractNanoporous electrodes, such as those made from carbon or gold, can capture and release ionic analytes at concentrations near 1 mole per liter of pore volume through capacitive charging or electrochemically reversible adsorption. In vitro studies suggest that this phenomenon can be the basis for a noninvasive, precise, and programmable drug delivery method. It eliminates the need for bulk fluid delivery to target tissue and requires only a thin electrical connection, minimizing pain and tissue disruption. Timing of release can be flexibly controlled. Compared to iontophoretic methods, there is minimal involvement of ions other than the drug, further reducing tissue disruption. We have designed effective gold electrode assemblies and observed the depletion and release phenomena using electrochemical methods and charged dyes.This work was performed under the Laboratory-Directed Research and Development Program at Sandia National Laboratories, a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
10:15 AM - VV8.4
3D-printing of Urethane-based Photoelastomers for Vascular Tissue Regeneration.
Stefan Baudis 1 , Thomas Pulka 2 , Bernhard Steyrer 2 , Harald Wilhelm 2 , Guenter Weigel 3 , Helga Bergmeister 3 , Juergen Stampfl 4 , Robert Liska 1
1 Institute of Applied Synthetic Chemistry (Division: Macromolecular Chemistry), Vienna University of Technology, Vienna Austria, 2 , TGM Vienna, Vienna Austria, 3 Ludwig-Boltzmann Cluster for Cardiovascular Research, Vienna Medical University, Vienna Austria, 4 Institute of Materials Science and Technology, Vienna University of Technology, Vienna Austria
Show AbstractLifestyle diseases are and will be a big issue and challenge for the industrial countries. For this reason regenerative medicine is a growing discipline in life science. Still there is the need for tailored, biocompatible, biodegradable and functional biopolymers with 3-dimensional, bio-inspired structures as scaffolds for guided tissue regeneration. The mechanical properties of materials designated for vascular tissue replacement are of crucial importance [1]. The elastic modulus, the tensile strength as well as the suture tear resistance have to be optimized.Our approach is to use photopolymers for artificial vascular grafts. Via the layer-by-layer photopolymerization of suitable resin formulations as performed in additive manufacturing technologies (AMTs) very complex structures are realizable. Hence AMTs offer the possibility to create cellular structures within the artificial grafts that might favor the ingrowth of new tissue.In preliminary studies a large variety of different monomers was screened. Cyanoethyl acrylate-based photopolymer hydrogels fulfill the basic material requirements for vascular tissue regeneration but still have some drawbacks [2]. Thus commercially available urethane diacrylates (UDA) were chosen as new base monomers since urethane groups are known to have good cell-adhesion behavior [3] and poly-UDAs show adequate mechanical performance. The mechanical properties of the photoelastomers can be tailored by addition of reactive diluents (e.g. 2-hydroxyethyl acrylate, HEA) and thiols [4] (e.g. 3,6-dioxa-1,8-octane-dithiol) as chain transfer agents to comply with the mechanical properties of natural blood vessels (modulus of ~0.5 MPa, tensile strength of ~1 MPa and elongation at break of ~130%). To examine the suture tear resistance a new testing method has been developed.A formulation containing 30w% UDA and 70w% HEA complies with the mechanical properties of natural blood vessels, shows good biocompatibility in in-vitro tests and was successfully 3D-printed with digital light processing AMT.[1] Lyman, D. J.; Fazzio, F. J.; Voorhees, H.; Robinson, G.; Albo, D., Jr. J. Biomed. Mater. Res. 1978, 12, 337-345.[2] Baudis, S.; Heller, C.; Liska, R.; Stampfl, J.; Bergmeister, H.; Weigel, G. J. Polym. Sci. A 2009, 47, 2664-2676.[3] Schuster, M.; Turecek, C.; Kaiser, B.; Stampfl, J.; Liska, R.; Varga, F. J. Macromol. Sci. A 2007, 44, 547-557.[4] Senyurt, A. F.; Wei, H.; Phillips, B.; Cole, M.; Nazarenko, S.; Hoyle, C. E.; Piland, S. G.; Gould, T. E. Macromolecules 2006, 39, 6315-6317.
10:30 AM - VV8.5
Additive Manufacturing Technologies for the 3D Fabrication of Biocompatible and Biodegradable Photopolymers.
Christian Heller 1 2 , Martin Schwentenwein 1 , Juergen Stampfl 2 , Franz Varga 3 , Robert Liska 1 , Maja Porodec 4 , Michaela Schulz-Sigmund 4 , Guenter Russmueller 5
1 Institute of Applied Synthetic Chemistry, Vienna University of Technology, Vienna Austria, 2 Institute of Materials Science and Technology, Vienna University of Technology, Vienna Austria, 3 Ludwig Boltzmann-Institute of Osteology, Hanusch Hospital, Vienna Austria, 4 Institute of Pharmacy, University of Leipzig, Leipzig Germany, 5 Department of Cranio-, Maxillofacial and Oral Surgery, Medical University of Vienna, Vienna Austria
Show AbstractThe design of a 3D scaffold with defined pore sizes offering good cell adhesion is still an important topic in tissue engineering. One approach to manufacture these scaffolds is by the curing of photosensitive resins by the means of Additive Manufacturing Technologies (AMTs) like microstereolithography (µ-SLA), Digital Light Processing (DLP) and two-photon induced photopolymerization (TPIP). With these techniques feature resolutions down to 10 µm (µ-SLA and DLP) or even 200 nm (TPIP) are obtainable.For this purpose new classes of monomers based on poly(vinyl alcohol) and therefore, circumventing potentially toxic (meth)acrylate chemistry, have been developed. These monomers have shown better biocompatibility in terms of cytotoxic effects compared to (meth)acrylate references. Beside a high reactivity of the resin, the shrinkage and the mechanical properties of the final part material are another essential parameter. Low molecular weight monomers lead to densely cross-linked materials which suffer from high shrinkage and strains within the cured material. Therefore, we have prepared various high molecular weight monomers based on biocompatible spacers like oligomeric fatty acid or oligo(ethylene glycol). Finally, 3D parts of biocompatible materials could be structured successfully with µ SLA, DLP and TPIP.
10:45 AM - VV8.6
The Mechanics of Mussel Byssal Threads: A Study in Protein Unfolding and Graded Structures.
Brian Greviskes 1 , Mary Boyce 1
1 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractNatural materials and structures have evolved over millions of years to perform very complex and specific biomechanical functions and, as a result, can provide insight into optimal designs for particular properties. Mussel byssal threads, the attachment appendage of aquatic mussels, are an example of a highly optimized natural adherent material and structure. These threads protrude from the mussel, connecting the mussel to rocks and other hard surfaces, providing a strong and resilient, yet dissipative attachment (so that the mussel can remain attached to the rocks without being dashed against them during violent wave periods). The threads themselves are graded, with both the geometry and the mechanical properties transitioning from the proximal (proximal to the mussel) thread section, which is thicker with an elliptical cross-section, compliant, and highly dissipative, to the distal thread section, which is thinner with a circular cross-section, stiff (relative to the proximal section) and less dissipative at low strains, but more dissipative at high strains.Here, the mechanical properties of the individual thread sections during the large cyclic stretches seen during its function are measured, determining and comparing the elastic vs. dissipative features of the behavior of each region and of the thread as a whole. The distal exhibits an initially stiff behavior followed by a “yield” and a transition into a more compliant large strain behavior. Upon unloading, the material reveals substantial recovery, indicating that the “yield” is not a plastic event, but rather the result of the microstructural evolution (unfolding) of the folded domains. More recovery occurred when the material was allowed to “rest” prior to subsequent loadings, demonstrating that the protein domains refold in a time-dependent manner. This unfolding and refolding provides the resilient yet dissipative material behavior. The proximal region is found to be more compliant, with no distinct “yield” event, but rather a continuous unfolding process as evidenced by a more compliant unloading and reloading behavior – again providing a dissipative but resilient response. A microstructurally-informed constitutive model that captures the microstructural evolution of these materials with loading (an evolution that is dominated by protein unfolding) was formulated for both distal and proximal regions. The constitutive model employs the mechanically-induced protein evolution as the strain rate and stretch-dependent dissipation mechanism, and captures the major characteristics of the elastic and the dissipative features of the mechanical behavior of these threads. These material models are then incorporated into a three dimensional finite element model of the thread, in order to gain insight into the overall thread behavior (the contributions from the distal and the proximal regions to the entire thread response) and the design of graded adherent structures.
11:00 AM - VV8: Processing
Break
11:15 AM - VV8.7
Electrochemical Deposition of Organic-inorganic Nanocomposites.
Igor Zhitomirsky 1
1 Materials Science and Engineering, McMaster University, Hamilton, Ontario, Canada
Show AbstractElectrochemical methods have been developed for the deposition of composite films, containing biopolymers, inorganic nanoparticles, drugs and proteins. Chitosan films were deposited by cathodic electrodeposition. Composite films containing hydroxyapatite, silica, titania and other bioceramics, bioglass in a chitosan matrix were obtained as monolayers, multilayers or materials of graded composition. Hydroxyapatite – chitosan films showed preferred orientation of hydroxyapatite nanoparticles in the chitosan matrix, similar to the orientation of hydroxyapatite in natural bones. Multilayer films were obtained, containing organic and inorganic layers. The films provided corrosion protection of metallic implants in simulated body fluid solutions.It was found that heparin-chitosan films can be obtained using chitosan-heparin complexes. The addition of anionic heparin to cationic chitosan resulted in increasing cathodic deposition rate. Bovine serum albumin – chitosan films were obtained by cathodic deposition. It was shown that this method allows electrodeposition of composite films containing other proteins and enzymes in a chitosan matrix.The feasibility of anodic deposition of alginic acid and hyaluronic acid has been demonstrated. Composite films containing hydroxyapatite and other bioceramics, bioglass, heparin and bovine serum albumin in the matrix of alginic acid or hyaluronic acid were obtained as monolayers, multilayers or materials of graded composition. It was shown that electrodeposition can be used for the fabrication of biopolymer films containing carbon nanotubes and bioceramics. Compared to layer-by-layer self assembly, the electrochemical methods offer the advantages of high deposition rate, the possibility of fabrication of thick and uniform films on substrates of complex shape, rigid control of film microstructure and composition.
11:30 AM - VV8.8
Electrohydrodynamic Jetting and Encapsulation.
Patrick Odenwaelder 1 , Yen Choo 2 , Nicolai Suter 3 , Suwan Jayasinghe 1
1 Mechanical Engineering, University College London, London United Kingdom, 2 , Plasticell Ltd., London United Kingdom, 3 , Nisco Engineering, Zurich Switzerland
Show AbstractElectrospray techniques have become established in the life sciences for uses from cell encapsulation [1] to, more recently, directed cell placement [2]. The largest application for electrosprays in the life sciences is the encapsulation of active biomaterials ranging from medication to cells and has been of considerable interest to the life sciences for some time. The most prominent area of encapsulation has been immunosuppression of xenotransplanted cells and islets of Langerhans [3]. This field has received considerable attention and development for several decades. One encapsulation technique that is commonly used is electrohydrodynamic jetting. In this process a conducting fluid in a needle connected to a high voltage power supply is charged and then drawn towards a grounded electrode by the electric field. Depending on the properties of the liquids processed, the voltages, flow rates and the setup, various spray modes can be achieved, of which the most commonly used are micro-dripping and cone-jet modes. Cells can be encapsulated by suspending them in a solution containing alginate and other materials in suspension and electrospraying them into a solution of a crosslinking agent, most commonly calcium chloride. Encapsulations are created using a single needle setup for some suspension or a coaxial arrangement of two or more needles for multiple media and suspensions, depending on the desired final result. This technique can be used to directly process and encapsulate many different types of materials [4-6]. Using this technique it is possible to encapsulate a wide combination of materials and can potentially be scaled up for larger trials or use in the pharmaceutical industry. Another expanding area of research is the use of electrosprays as a placement and print technique of living tissue. Recently, this technique has been established as a safe handling method for the placement of tissues from stem cells to entire embryos [7, 8]. This talk will elucidate how electric field driven encapsulation techniques can expanded to new applications. We demonstrate how electrohydrodynamic jetting and encapsulation can be effectively for new applications from directed printing to encapsulation in multiple layers. References: 1.Chang, T.M.S., 1964. 146(3643): p. 524 - 525.2.Jayasinghe, S.N., P.A. Eagles, and A.N. Qureshi, Biotechnol J, 2006. 1(1): p. 86-94.3.Orive, G., et al., Nat Med, 2003. 9(1): p. 104-7.4.Jayasinghe, S.N. and A. Townsend-Nicholson, Lab Chip, 2006. 6(8): p. 1086-90.5.Jayasinghe, S.N., Biotechnol J, 2007. 2(8): p. 934-7.6.Patel, P., et al., Soft Matter, 2008. 4: p. 1219 - 1229.7.Mongkoldhumrongkul, N., J.M. Flanagan, and S.N. Jayasinghe, Biomed Mater, 2009. 4(1): p. 15018.8.Geach, T.J., et al., Analyst, 2009. 134(4): p. 743-7.
11:45 AM - VV8.9
Micro-Structured Silica Coatings with HA Particles Using a PDMS Stamp.
Alejandro Pelaez-Vargas 1 2 , Daniel Gallego-Perez 2 , Nicholas Ferrell 2 , Maria Fernandes 3 , Derek Hansford 2 , Fernando Monteiro 1
1 , INEB - Instituto de Engenharia Biomédica, Divisão de Biomateriais, Universidade do Porto, Portugal and Departamento de Engenharia Metalúrgica e Materiais, FEUP - Faculdade de Engenharia, Universidade do Porto, Portugal., Porto Portugal, 2 Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio, United States, 3 Laboratório de Farmacologia e Biocompatibilidade Celular, Faculdade de Medicina Dentária, Universidade do Porto, Porto Portugal
Show AbstractIt is well known that titanium is the gold standard for oral implantology. However, in many clinical cases its appearance is not ideal for patients with thin gingival tissues. Yttrium stabilized zirconia (Y-TZP) and zirconia toughened alumina (ZTA) are alternative materials that have excellent aesthetic performance but slow osseointegration. The implementation of bioactive coatings could be used as a strategy to address this problem. In this work, a technique that includes silica sol-gel chemistry and soft lithography technology was developed to produce micropatterned silica coatings with hydroxyapatite nanoparticles (nanoHA). NanoHA was prepared following a standardized methodology in our group. Silica sol was obtained using alkoxides (TEOS and MTES). A meta-stable solution of silica with nanoHA particles was prepared. A microtexturing technique using previously patterned PDMS stamps was optimized using a multilevel resolution mask with feature sizes ranging from 500nm to 20μm. Morphological characterization before and after sintering was conducted via SEM. The coatings were then sterilized and cultured with MG63 human osteoblast-like cells using a standardized protocol at two time points (4h and 24h). Adhesion and cell morphology were evaluated using SEM and LSCM.Crack-free micropatterned silica coatings with nanoHA particles were successfully obtained. SEM and LSCM images showed cell alignment in the direction of the micropatterns. These preliminary results showed that micropatterned bioactive silica coatings on dental ceramics could find applications in the fabrications of aesthetic oral implants. The PhD grant FCT/SFRH/BD/36220/2007 is acknowledged.
12:00 PM - VV8.10
Antimicrobial Activity of Ormocer Microneedles with Silver Coatings Deposited by Pulsed Laser Deposition.
Shaun Gittard 1 , Roger Narayan 1 , Aleksandr Ovsianikov 2 , Boris Chichkov 2
1 Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, United States, 2 Nanotechnology, Laser Zentrum Hannover, Hannover Germany
Show AbstractMicroneedle mediated transdermal drug delivery is a promising technique for the administration pharmacological agents directly into the bloodstream, a requirement for protein and nucleic acid-based pharmacologic agents which are incompatible with other delivery methods. One major concern associated with microneedle use is the increased risk of infection due to the creation of pores in the stratum corneum. In this study, we demonstrated the production of microneedles with antimicrobial activity that can reduce the associated risk of infection. Two photon polymerization-photopolymerization micromolding and pulsed laser deposition were used to fabricate the microneedles and enable antimicrobial activity, respectively. The silver-coated organically modified ceramic (Ormocer) microneedles were shown to inhibit growth of S. aureus by testing with the agar diffusion assay. Biocompatibility of the silver-coated microneedles was demonstrated by performing the MTT assay with human epidermal keratinocytes. This study indicates that thin film deposition of silver by pulsed laser deposition is a viable method for creating microneedles that inhibit infection at the site of use.
12:15 PM - VV8.11
Gentamicin Sulfate Doped Polyethylene Glycol Diacrylate Microneedles Inhibit Growth of Pathogenic Bacteria.
Shaun Gittard 1 , Aleksandr Ovsianikov 2 , Boris Chichkov 2 , Roger Narayan 1
1 Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, United States, 2 Nanotechnology, Laser Zentrum Hannover, Hannover Germany
Show AbstractMicroneedles are an emerging drug delivery technology that has the potential to provide the robustness of injections without the pain. With the ability to efficienty deliver protein and nucleic acid based pharmacological agents, the technique shows promise to improve treatment of a wide range of disease, from diabetes to cancer. In microneedle mediated drug delivery, small projections are used to improve the delivery of pharmacological agents through the stratum corneum and epidermis of the skin. Due to the potential for infectious agents to enter the microneedle generated pores, we investigated the antimicrobial ability of antibiotic doped microneedles. A photopolymerizing hydrogel, polyethylene glycol diacrylate 600 with Irgacure 369 photoinitiator and the antibiotic gentamicin sulfate, was used to fabricate microneedle arrays. The photopolymerization-micromolding technique using molds of microneedles fabricated by two photon polymerization was used to create the microneedles. FTIR and nanoindentation were used to characterize the chemical and mechanical properties of the antibiotic doped hydrogels, respectively. The microneedles were shown to have nonfouling properties while still having no adverse affects on human epidermal keratinocyte viability. Agar diffusion assays with Staphylococcus aureus demonstrated that the gentamicin doped microneedles inhibit the growth of pathogenic bacteria. This study suggests that photopolymerization micromolding with antibiotic doped polymers is an effective means of creating microneedles with reduced risk of infection.
12:30 PM - VV8.12
Crosslinked Laminin Fibers Nanofabricated by Multiphoton Excited Photochemistry and Their Application in Studying Interaction of Ovarian Cancer Cells with Intracellular Matrix.
Xiyi Chen 1 , Molly Brewer 1 , Paul Campagnola 1
1 CCAM, Univ. of Conn. Health Center, Farmington, Connecticut, United States
Show AbstractOvarian cancer is among the deadliest gynecological cancers and has a very low survival rate. It is thus very important to study the interaction between ovarian cancer cells and their extracellular matrix, so that insights can be gained regarding the metastasis mechanisms involved, as this may lead to new treatment/detection methods. We use multiphoton excited photochemistry (MPE) to crosslink laminin molecules and form desired fibrillar structures to mimic the ovarian basal lamina in vivo. Three ovarian cancer lines of different invasiveness potentials (OVCA433, SKOV-3.ip1, and HEY-1), together with an immortalized ovarian epithelial cell line (IOSE) as the control, are employed to study the migration, directed migration, adhesion, and f-actin assembly. Our results indicate that the nanofabricated laminin model recaptures some of the 3D topographic and biochemical cues of the native basal lamina. The cell migration dynamics on the laminin nanofibers are distinctly different from those on the 2D laminin monolayer on the glass. All four cell lines migrate along the laminin lines, and their focal adhesions are induced by the laminin structures. We also discovered that the total migration rate increases with the metastatic potential. The nanostructured fibers influence strongly the cytoskeletal dynamics in terms of spread area, rigidity, and adhesion strength, where the more invasive cells are less rigid and more weakly adhered to the nanofibers. Collectively, the results suggest that both haptotactic and contact mediated migration as well as decreased adhesion may be operative in metastasis of ovarian cancer in vivo.
12:45 PM - VV8.13
Tissue Engineering Scaffold Design and Fabrication by Analytical Modeling and Laser Microablation.
George Engelmayr 1
1 Bioengineering, Penn State University, University Park, Pennsylvania, United States
Show AbstractA variety of design and fabrication methodologies have been applied to the problem of creating bioresorbable scaffolds for use in tissue engineering. Here I will present on our progress toward the rapid fabrication of tissue engineering scaffolds with explicitly programmed structural-mechanical properties.Engelmayr et al. recently reported in Nature Materials [1] on the use of excimer laser microablation to fabricate an “accordion-like” honeycomb scaffold from the bioresorbable elastomer poly(glycerol sebacate) (PGS) [2]. The accordion-like honeycomb microstructure yielded anisotropic stiffnesses closely matched to native myocardium, while simultaneously providing an inherent structural capacity to promote the native-like alignment of seeded neonatal rat heart cells. Matching of anisotropic mechanical properties to native myocardium was achieved via a combination of pore geometry and PGS bulk mechanical properties, which were dialed-in by empirically varying the pore geometry and PGS curing time (range 4-16 h) at constant temperature (160°C). Notably, others recently reported on tailoring PGS bulk mechanical properties for cardiac muscle applications by varying the PGS curing temperature [3].Said progress in scaffold design is tempered, however, by the need for quantitative models sufficiently rigorous to yield functionally-accurate approximations of scaffold material behavior under physiologically-relevant conditions. In our lab we are taking an analytical approach in which mechanics of materials-based techniques are utilized to synthesize deterministic scaffold design equations amenable to coupling with our laser equipment.The long-term goal of our work is contribute toward the development of processes by which engineered tissues can be explicitly designed, rapidly rendered, and reproducibly validated for pre-clinical and clinical applications. References:1.Engelmayr GC Jr, Cheng M, Bettinger CJ, Borenstein JT, Langer R, Freed LE. Accordion-like honeycombs for tissue engineering of cardiac anisotropy. Nat Mater. 2008 Dec;7(12):1003-10. Epub 2008 Nov 2.2.Wang Y, Ameer GA, Sheppard BJ, Langer R. A tough biodegradable elastomer. Nat Biotechnol. 2002 Jun;20(6):602-6.3.Chen QZ, Bismarck A, Hansen U, Junaid S, Tran MQ, Harding SE, Ali NN, Boccaccini AR. Characterisation of a soft elastomer poly(glycerol sebacate) designed to match the mechanical properties of myocardial tissue. Biomaterials. 2008 Jan;29(1):47-57.