Symposium Organizers
Shu Yang University of Pennsylvania
Fiona Meldrum University of Leeds
Nicholas Kotov University of Michigan
Christopher Li Drexel University
MM1: Bioinspired Synthesis and Assembly
Session Chairs
Tuesday PM, April 14, 2009
Room 3020 (Moscone West)
9:00 AM - **MM1.1
Patchy Micelles and Liposomal Systems: Modular Assembly for Drug and Gene Delivery
Paula Hammond 1
1 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractThe ability to manipulate micellar structures to achieve optimal biomaterials properties has been one of the primary goals in the design of biomimetic and bioinspired materials systems. Natural systems often present molecular recognition sites on the surfaces of cell walls in clusters or predetermined groupings based on multivalent binding sites. Although it has been shown that binding avidity can be greatly influenced by the presence of multivalent ligands, there is little known about the impact of the nature of presentation of ligand. Cluster presentation has been shown to be of critical importance in cellular functions such as adhesion and mobility. Here we explore the role of cluster presentation of ligand on patchy micelles generated by the self-assembly of linear dendritic block copolymers. Key to the approach is the synthesis of new amphiphilic linear peptide-dendritic block copolymers that self-assemble in the solution state to generate stable micelles with highly branched, dense dendritic groups in the exterior shell. Due to the unique nature of the dendritic outer block, these micelles act as vessels with a highly tunable 3D presentation of ligand, enabling the creation of delivery nanoparticles with homo- or heterogeneous surfaces that enable cluster presentation of ligand. Biological studies of cellular interactions with ligands indicate that not only the valency but spatial and geometric factors such as branching mode and the localized clustering of groups are important in influencing binding, intracellular uptake and downstream signaling processes. In vitro and in vivo studies indicate that these factors have significant influence on uptake. Additional studies on the general self-assembly behavior of these peptide-dendritic systems, and the resulting formation of liposomal and other colloidal structures will also be discussed.
9:30 AM - **MM1.2
The Molecular Structure of Helical Supramolecular Dendrimers
Virgil Percec 1
1 Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractHelical secondary structures represent one of the most fundamental architecture encountered in biological macromolecules. Our laboratory is using self-assembling dendrons as a model to mimic and understand the principles via which helical structures are assembled. In this presentation the molecular structure of helical supramolecular dendrimers generated from self-assembling dendrons and dendrimers and from self-organizable dendronized polymers was elucidated by the simulation of the x-ray diffraction patterns of their oriented fibers by using the helical diffraction theory applied to simplified atomic helical models and Cerius2 calculations based on complete molecular helical structures. Hundreds of samples were screened until a library containing fourteen supramolecular dendrimers and dendronized polymers provided a sufficient number of helical features in their oriented fibers. These techniques provided examples of single-92 and -113 helices, triple-61, -81, -91 and -121 helices and an octa-321 helix that were assembled from crown-like dendrimers, hollow and non-hollow supramolecular crown-like dendrimers, hollow and non-hollow supramolecular disc-like dendrimers, hollow and non-hollow supramolecular and macromolecular helicene-like architectures. The method elaborated here was transplanted from structural biology and will be applicable to other classes of synthetic helical assemblies. These experiments demonstrated that self-assembling dendrons, dendrimers and self-organizable dendronized polymers have a simpler primary structure and more complex topology but exhibit a richer architectural diversity of their secondary structure than proteins, nucleic acids and carbohydrates. The elaboration of new functions based on helical assemblies will be discussed.
10:00 AM - MM1.3
Bio-inspired Use of Ionically Crosslinked Polyamines in Hollow Sphere Synthesis
Shyam Kadali 1 , Hitesh Bagaria 1 , Michael Wong 1 2
1 Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, United States, 2 Department of Chemistry, Rice University, Houston, Texas, United States
Show AbstractIn nature, it is shown that polyamines behave in unusual ways in solution due to their charged nature and some times generate specific assemblies [1-2]. Studies have revealed that, in biosilification, naturally-occurring polyamines adopt particular conformations depending on their concentration and salts present, and cause aggregation of silica species [2-3]. To take advantage of this behavior, we developed a materials synthesis technique in which synthetic polyamines such as polyallylamine and polylysine are crosslinked with multivalent anions like citrate to form polymer-salt aggregates, that then serve as templates for the deposition of nanoparticles to form micron-sized hollow spheres or "nanoparticle-assembled capsules (NACs)" [4-5]. This electrostatically-driven route is attractive for encapsulation and scale-up because encapsulation and materials formation occur in water, at mild pH values, and at room temperature.NACs can potentially find wide-ranging applications in pharmaceutical, food, and consumer industries by serving as miniature containers to store, deliver, and release substances. One of the most encouraging aspects of NACs is the flexibility in design of materials to tailor them for specific applications. Although synthesis of NACs is well understood [4-5], less attention has been paid to their structural properties and stability. It is of crucial importance to address this aspect of NACs in view of their use and applicability. While most applications may require that NACs not disassemble or deform under shear stress, some may require triggered release under specific conditions to release the encapsulated material (e.g., enzymes or drugs). In this presentation, the stability of NACs is studied under varying pH, ionic strength, and osmotic pressure conditions.As an illustration, capsules can be made either polymer filled or water filled by changing pH between 3 and 10. On the other hand, outside this pH range, NACs can be dissembled. Osmotic pressure studies [6] carried out using poly(styrenesulfonate sodium salt) solutions suggests that the polymer-salt aggregates that reside inside the capsules provide structural reinforcement of the capsules. Understanding the sensitivity of NACs towards various conditions would help in better understanding and perhaps tailoring their properties for drug delivery and controlled release. Keywords: Microcapsule, hollow, nanoparticle, NACs, pH, ionic strength, osmotic pressureReferences:[1] S. V. Patwardhan et al., Silicon Chemistry 1: 47–55, 2002.[2] S. K. Tripathy et al.,Handbook of Polyelectrolytes and Their Applications, ed., American Scientific Publisher, California, 2002[3] S. V. Patwardhan et al., Chem Comm 1113-1121, 2005[4] R. K. Rana et al., Adv. Mater. 17, 1145-1150 (2005) [5] S. B. Kadali et al., Topic. Catal, 49, (3-4) ,251-258 (2008)[6] C. Gao, et. al., Eur. Phys., V5, 21(2001)
10:15 AM - MM1.4
Supramolecular Assembly of the Dps-like Cage Protein from the Hyperthermophile Sulfolobus Solfataricus.
Chris Broomell 1 , Mark Young 1 , Trevor Douglas 1
1 Center for Bioinspired Nanomaterials, Montana State University, Bozeman, Montana, United States
Show AbstractMetal organic frameworks (MOFs) have garnered much attention in the past several years for the relative facility of their synthesis and potential benefit in diverse applications such as energy storage, drug delivery and as novel polymeric materials. MOFs generally comprise metal ions or clusters coordinated by rigid or semi-rigid organic building blocks. To date there have been relatively few reports of MOF assembly from peptide-based precursors. However, there are numerous examples in nature whereby coordination polymerization directs macromolecular assembly and critically influences material properties. MOFs generated from biomolecules offer several potential advantages over their synthetic counterparts including extensive structural diversity, intrinsic chirality and the capacity for introduction of catalytic or similar biological functionalities.Protein cages represent an intriguing platform for construction of metal-organic assemblies. The cages are themselves supramolecular assemblies of limited numbers of protein subunits that spontaneously self-assemble into spherical structures with monodisperse size distributions. Cage surfaces are readily modifiable via genetic and chemical methods, thereby permitting the highly symmetrical and spatially controlled multi-valent display of metal coordinating ligands. Cage interiors are ideal for incorporation of additional functionality, for example, as nano-templates for mineralization or the controlled synthesis of functional bio-materials or as containers for drug encapsulation. Together, these features underscore the potential for protein cages as building blocks for MOF development, including the generation of heterogeneous materials with tunable properties and hybrid functionalities.Current focus will be recent generation and characterization of supramolecular assemblies using the dodecameric Dps-like protein from the hyperthermophile Sulfolobus solfataricus as a tecton and a combination of metal-chelate and organic click-based coordination connectivity.
10:30 AM - MM1.5
Theoretical Model for the Self-assembly of Clathrin into Targeted Nanoscale Assemblies.
Shafigh Mehraeen 1 , Alia Schoen 2 , Sung Yeon Hwang 2 , Sarah Heilshorn 2 , Andrew Spakowitz 3
1 Mechanical Engineering, Stanford University, Stanford, California, United States, 2 Materials Science and Engineering, Stanford University, Stanford, California, United States, 3 Chemical Engineering, Stanford University, Stanford, California, United States
Show AbstractClathrin is a cytoplasmic protein that plays a critical role in endocytosis by forming the basket-like cages on the cell membrane that seed the formation of the endosome pits that transport cargo into the cell. A single clathrin complex adopts a pinwheel configuration. The aggregation of many clathrin pinwheels on a membrane or interface leads to lattice-like assemblies with a mixture of 5-, 6-, and 7-member rings. In vitro assembly of clathrin within a solution results in closed, nanoscale assemblies with various shapes and sizes. Our goal in this research is to develop a fundamental theoretical model for the thermodynamics and kinetics of clathrin assembly in 2 and 3 dimensions in order to guide experiments toward the assembly of targeted nanoscale assemblies. Towards this goal, we have developed a theoretical model for clathrin assembly that can address the assembly dynamics in 2 and 3 dimensions. The clathrin are modeled as effective pinwheels that form leg-leg associations and resist elastic bending deformation; thus, the pinwheels are capable of forming the range of ring structures that are observed experimentally. Our theoretical model combines Brownian dynamics simulations with dynamic mean field theory in order to track the motion of hundreds of clathrin pinwheels at sufficiently long time scales to achieve complete assembly. With this theoretical model, we predict the phase diagram for clathrin assembly and perform dynamic simulations for a range of quenches into the phase diagram. The resulting dynamics exhibit the hallmark behavior of spinodal decomposition with subsequent coarsening of ordered domains. The defect structures in the final configurations result in large-scale elastic stresses in the lattice network; these stresses will be discussed in the context of the biological function of clathrin and in terms of controlling the resulting assembled structures.
10:45 AM - MM1.6
Artificial Polymers Mimic Bacteriophage Capsid Proteins and Encapsulate Nucleic Acids.
David Robinson 1 , George Buffleben 1 , Ronald Zuckermann 2
1 , Sandia National Laboratories, Livermore, California, United States, 2 , Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractThe filamentous bacteriophage m13 and related viruses encapsulate DNA with protein, forming a relatively rigid organic nanowire about 1 micrometer long and less then 10 nanometers wide. The length of the wire is formed from many copies of a single protein, which is a single alpha helix formed from about 50 amino acids. It can be viewed as a very sophisticated surfactant, with hydrophilic regions that interact with the DNA and form the outer surface, and hydrophobic regions that pack against each other. We have implemented these design principles in peptoids (sequence-specific N-functional glycine oligomers) and have found that they form well-defined assemblies with DNA. We are applying these peptoids to branched DNA duplexes in efforts to create rigid three-dimensional organic structures that assemble in precisely defined ways.
11:15 AM - **MM1.7
Bio-inspired Polymer Brushes for Hierarchical Soft and Hybrid Materials.
Christopher Ober 1 , Abhinav Rastogi 1 2 , Rong Dong 1 2 , Marvin Paik 1 , Manabu Tanaka 1 , Grace Berrios 1 , Suddhasattwa Nad 2 , Norah Smith 2 3 , Lisa Blum 4 , Yelena Bisharyan 3 , Yi Liu 2 , Khajak Berberian 5 , Theodore Clark 3 , Judith Appleton 4 , Barbara Baird 2 , Manfred Lindau 5 , Hector Abruna 2
1 Materials Science & Engineering, Cornell University, Ithaca, New York, United States, 2 Chemistry and Chemical Biology, Cornell University, Ithaca, New York, United States, 3 Microbiology and Immunology, Cornell University, Ithaca, New York, United States, 4 James A. Baker Institute of Animal Health, Cornell University, Ithaca, New York, United States, 5 Applied and Engineering Physics, Cornell University, Ithaca, New York, United States
Show AbstractTopological and chemical groups at the surface have been shown to affect biological response. Significant work has gone into studying protein adsorption and non-specific adsorption resistance on material surfaces. Self assembled monolayers (SAMs) have been used as model surface coatings to study biological interactions. However, polymer brushes present an attractive alternative to SAMs. Polymer brushes are an assembly of polymer chains that are tethered at one end to a surface or interface. This tethering is sufficiently dense that the polymer chains are crowded and are forced to stretch away from the surface or interface to avoid overlapping. They can be made using several different methods, giving the ability to tailor and design surface properties through functionalization of side-groups, and can be grown much thicker offering a higher density of surface reactive sites. Our group has invested much effort to study the use of polymer brushes in controlling the interaction between material surface properties and bio-matter. We have grown poly(acrylic acid) (PAA) brushes for use in two different electrochemical applications through surface modification of the polymer brush.
11:45 AM - **MM1.8
Orthogonal Approaches to Functionalized, Well-defined Nanostructures.
Craig Hawker 1
1 Materials Research Laboratory, UCSB, Santa Barbara, California, United States
Show AbstractIn designing polymeric materials for use in nanotechnology it rapidly becomes apparent that control over all aspects of polymer structure (molecular weight, polydispersity, number and position of functional groups, architecture, etc.) is required if these materials are to be used successfully to create nanostructures in the sub-50 nm size regime. Equally important to the rapid introduction and incorporation of these materials into devices is the development of robust and simple techniques for their synthesis. This last feature will allow a wide range of materials to be prepared efficiently while also permitting non-experts to prepare well-defined materials. The most promising approach to this is a ‘bottoms-up’ approach relying on chemistry, and recent developments in nanoparticles, shape persistent 3-dimensional macromolecules, 'living' free radical procedures and Click chemistry have allowed the construction of tailor-made polymer molecules and nanoparticles that facilitate this strategy. The design and application of these materials in the design of bio-inspired hierarchical soft and hybridmaterials will be described with examples including novel diagnostic and therapeutic agents for the treatment of cardiovascular disease, sub-20nm patterning strategies for advanced microelectronics and composite structures for controlling cell growth and proliferation. Further examples will demonstrate that these new synthetic techniques may also have application in other areas such as bio-sensors, DNA chips, delivery devices and high modulus hydrogels.
12:15 PM - MM1.9
The Self-organization of 2D Ordered Spines into 3D Mesoscale Hierarchical, Helical Assemblies.
Boaz Pokroy 1 , Sung Hoon Kang 1 , L. Mahadevan 1 , Joanna Aizenberg 1
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show AbstractIn this talk we will show an interesting phenomenon of how spontaneous helicity may be induced in an athermal mesoscopic system, where neither the assembling elements nor the field are chiral. In our approach, capillarity-driven bending and subsequent optimization of the adhesive contact in a rationally-designed array of nanopillars result in the generation of highly-ordered helical clusters with unique structural hierarchy. This phenomenon arises from the sequential assembly of self-similar chiral building blocks over multiple length scales. While complex, chiral movement of the pillars and their significant mechanical interlocking at the sub-micron scale are expected to be widely applicable. In this presentation we will demonstrate their function in the context of self-assembly into new structures with uniform, periodic patterns and controlled chirality, and as an efficient particle-trapping and adhesive system.
12:30 PM - MM1.10
Designing Molecular-Recognition Hydrogels for Cell Encapsulation.
Cheryl Wong Po Foo 1 , Sarah Heilshorn 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States
Show AbstractCell transplantation has emerged as a promising therapy for a variety of diseases, including Parkinson’s, Huntington’s, and stroke. However, cell survival after transplantation is poor and unpredictable; and enhanced cell survival is directly correlated to functional recovery. Cell encapsulation within a physical hydrogel has been found to increase cell survival during transplantation; however, current physical hydrogels require a change in environmental conditions, such as pH, temperature, or ionic strength, to initiate the sol to gel phase transition during cell encapsulation. These conditions are detrimental to cell survival and consequently can negate any positive effects of the hydrogel. In response, we have designed, synthesized, and characterized a family of molecular-recognition hydrogels that do not require environmental triggers for gelation to occur. Instead, the hydrogels are composed of two components that undergo a sol-gel phase transition upon mixing due to specific molecular-recognition interactions through hydrogen bonds. The design of the two components is based on simple polymer physics considerations and utilizes bio-mimimcry to create modular engineered proteins. Precise variations in the molecular-level design of the two components, created using recombinant protein techniques, are used to predictably tune the hydrogel viscoelasticity. Adult neural progenitor cells are encapsulated within these gels with high viability at constant physiological conditions. The gels promote the growth and differentiation of these neural progenitors into both glial and neuronal phenotypes, which adopt a well-spread and branched morphology in these 3D cultures.
12:45 PM - MM1.11
A Biocompatible Bottom-Up Route for Preparation of Hierarchical Hybrid and Bio-Hybrid Materials.
Francisco del Monte 1 , Maria C. Gutierrez 1 , Maria L. Ferrer 1
1 , ICMM-CSIC, Madrid Spain
Show AbstractStructurally organized inorganic materials are attracting much attention for emerging applications (e.g., catalysis, storage and controlled release systems, smart fillers and biotechnologies) since they offer a desirable combination of high internal reactive surface along narrow nanopores with facile molecular transport through broad “highways” leading to and from these pores. The incorporation of biomolecules within such organized materials with a full preservation of their native structure would result in the achievement of functional materials with increased levels of space organization; e.g. hierarchically organized functional materials. In this work, we have applied the ISISA (ice-segregation induced self-assembly) process for the preparation of hierarchical hybrid and bio-hybrid materials exhibiting a very sophisticated structure with up to six levels of space organization. The ISISA process consists on the unidirectional freezing (at -196 degrees C) of the hydrogel nanocomposites. Upon freezing, the ice formation causes every solute originally dispersed in the hydrogel to be segregated from the ice phase. After freeze-drying, the resulting hierarchical structures consists on well aligned micrometer-sized pores in the freezing direction corresponding to the empty areas where ice crystals originally resided, being the macrostructure supported by the matter accumulated between adjacent ice crystals.
MM2: Biopolymer Mediated Synthesis and Assembly
Session Chairs
Xinqiao Jia
Nicholas Kotov
Tuesday PM, April 14, 2009
Room 3020 (Moscone West)
2:30 PM - **MM2.1
Biohesion – Coupling Materials and Biological Entities using Engineered Solid Binding Peptides.
Mehmet Sarikaya 1 2 , Ersin Oren 1 2 3 , Ram Samudrala 1 2 , Beth Traxler 1 2 , John Evans 1 4 , Candan Tamerler 1 2 5
1 Genetically Engineered Materials Science and Engineering Center, Universityof Washington, Seattle, Washington, United States, 2 Materials Science and Engineering, Universityof Washington, Seattle, Washington, United States, 3 Microbiology, University of Washington, Seattle, Washington, United States, 4 Chemistry, New York University, New York, New York, United States, 5 Molecular Biology and Genetics, Istanbul Technical University, Istanbul Turkey
Show AbstractIn biology, molecular recognition is the basis of all interactions including those between antigen-antibody, anyzme-substrate, and protein-lipid membrane, in which proteins play the central role. As being molecular and ionic transporters, functional scaffolds, cell signalers, and transcription factors regulating genes, proteins are the workhorses of life. With the recent developments of nanoscale engineering in physical sciences and the advances in molecular biology, we are combining genetic tools with synthetic nanoscale constructs in creating a hybrid methodology, molecular biomimetics. Here, using biology as a guide and adapting bioschemes including combinatorial mutagenesis, bioinformatics, and recombinant DNA technologies, we select, design and tailor short peptides (7-60 amino acids) with specific binding to and assembly on functional solid materials and use them a building blocks in technology and medicine. Based on the fundamental principles of genome-based design, molecular recognition, and self-assembly, we can now engineer peptides with specific sequences to control adhesion of biological entities to solids (biohesion) and use them as nucleators, catalyzers, growth modifiers, molecular linkers and erector sets, simply as fundamental utilities for nano- and bionano-technology. We will review the recent developments in our collaborative research groups in this rapidly developing polydisciplinary field, focusing on the utility of solid-binding peptides in: i. Functional biomaterialization for nanotechnology (nanoparticles and thin films) and regenerative medicine (scaffolds towards tissue regeneration), ii. Bi-functional genetic fusion constructs (enzymes and cell signalers); iii. Molecular erectors for directed and targeted self assembly of biomolecular/nanoparticle multicomponent entities towards imaging and sensing for nanophotonics and diagnostics. The research is supported mainly, by, NSF-MRSEC, and also by NSF-BioMat, NSF-IRES, and NIH programs.
3:00 PM - **MM2.2
Reversible Structural Transition of a DNA-Lipid Film.
Matthew Tirrell 1 , Surekha Gajria 1 , Thorsten Neumann 1 , Luc Jaeger 1
1 Materials Research Laboratory, University of California, Santa Barbara, Santa Barbara, California, United States
Show AbstractNaturally derived polyanions such as nucleic acids (RNA and DNA) can self-assemble with cationic lipids via electrostatic complexation, driven thermodynamically by the release of counterions. The structure of these complexes dispersed in water have been studied extensively by groups such as Safinya et al. and have been recognized as potentially useful in the field of gene delivery . The structure of films in water is dominated by the nature of the lipid e.g. cylindrical lipids like DDAB or DOPC and their nucleic acid complexes form lamellar structures. Within these lamellar complexes in aqueous solution the lipid assumes a bilayer formation and the DNA is a double helix. However amphiphilic lipids like DOPC and DOPE and their nucleic acid complexes are water soluble while cationic lipids like DDAB tend to form more water insoluble complexes, depending on the length of the carbon chain tail. These cationic complexes are only soluble in organic solvents like ethanol, isopropanol or chloroform. It is possible to obtain nucleic acid-lipid films when the dissolved cationic lipid complex of DDAB and nucleic acid is cast on a solid material such as Teflon or glass. These self-standing films have been characterized macroscopically by tensile properties and nucleic acid intercalation experiments. It has been reported that the DNA strands within these films can be aligned as the film is stretched, which has led to their application as a new type of anisotropically conductive material . The tensile properties of these films are adjustable with molecular weight or by mixing different kinds of nucleic acid, like DNA and RNA for the complex with DDAB. It was expected that these films would have the same characteristic structure as these complexes in water. The state of the DNA within similar films generated by Langmuir-Blodgett (LB) as well as layer-by-layer (LbL) deposition is a subject of controversy, as few papers have been able to propose a consistent structure (e.g. A-, B-, or C-form DNA. Although some papers have suggested the DNA in such films is single stranded, the evidence is very thin; often no structure is given to satisfactorily explain the state of the lipid . We focused in our work on the structure of DNA-DDAB films and found an intriguing model that is able to fully describe the behavior of the DNA and the lipid in the film.Our overall picture shows that the film undergoes a transition from double stranded helical DNA complexed with a bilayer of DDAB in the wet state, while in the dry state we observed a repetition unit of single stranded DNA complexed with a monolayer of DDAB.
3:30 PM - MM2.3
Biomediated Assembly of Complex and Dynamic Nanostructures.
Erik Spoerke 1 , Judy Hendricks 1 , Adrienne Greene 1 , Haiqing Liu 1 , George Bachand 1 , Elena Bekyarova 2 , Robert Haddon 2 , Bruce Bunker 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , University of California at Riverside, Riverside, California, United States
Show AbstractMicrotubules (MTs) and motor proteins (MPs) are remarkable biological tools that mediate sophisticated intracellular organization, assembly, and transport. Capable of regulating intracellular cargo transport, cytoskeletal organization, and even elements of cell division, these cooperative active biomolecules are attractive targets for integration into emerging nanotechnologies. We have learned to incorporate these biomolecular tools into in vitro materials assembly schemes that enable us to create dynamic, nanoscale architectures in two and three dimensions. We have demonstrated the use of MTs and MPs in the formation of dynamic templates for the formation of structures such as “erasable” arrays of interconnects formed from carbon nanotubes or three dimensional composite asters. We have also explored how interactions between the MTs, MPs, and synthetic supramolecular assemblies, such as hydrogels or liquid crystals, enable us to create complex, dynamic composite structures in three dimensions. This talk will focus on a description of these biomediated assemblies and discussion of some of the underlying interactions responsible for the dynamic, non-equilibrium structures created. Sandia is 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.
3:45 PM - MM2.4
Protein-Polymer Biohybrid Amphiphiles.
Jeroen Cornelissen 1 , Irene Reynhout 1 , Ton Dirks 1 , Guillaume Delaittre 1 , Ho-Cheol Kim 2 , Roeland Nolte 1
1 Institute for Molecules and Materials, Radboud University, Nijmegen Netherlands, 2 , IBM Almaden Research Center, San Jose, California, United States
Show AbstractAmphiphilic molecules (also termed surfactants or soaps) consist of both a hydrophilic and a hydrophobic segment and have been widely studied because of their self-assembling properties in aqueous media. For a long time these studies have mainly focused on low molecular weight amphiphiles, such as phospholipids and their synthetic counterparts (e.g., dioctadecyldimethylammonium chloride), and consequently the self-assembly behavior of these compounds is now well understood. In fact, the type of aggregates that phospholipids form in water (e.g., micelles, rod-like structures, bilayers, and vesicles) can accurately be predicted by established models, which are based on the shape of the molecules. Besides the traditional type of surfactants, also various amphiphilic block copolymers have recently beenshown to exhibit interesting self-assembling properties. Such block copolymers (also referred to as ‘‘super amphiphiles’’) often aggregate in a remarkably similar way as their low molecular weight counterparts. Compared to traditional surfactants, amphiphilic block copolymers, however, form more robust assemblies, rendering them ideal for the construction of nanoreactors and drug delivery vehicles. Following this line of development, our group has recently designed novel types of macromolecular amphiphiles that contain a biopolymer, e.g., a beta-sheet helical peptide or even a complete protein as the hydrophilic block. It was envisioned that the site-specific linking of a hydrophobic polymer to a protein would result in a biohybrid amphiphile, a so-called giant amphiphile, which shows great structural analogy with traditional surfactants even though it is considerably larger. Owing to their typical molecular structure, the giant amphiphiles were expected to show a similar hierarchical self-assembly behavior as the conventional surfactants [1].Here we will report on the formation of defined assemblies using these polymer-protein biohybrid building blocks. Increasingly complex architectures are formed when going from diblock copolymer to triblock copolymer based amphiphiles [2]. On a surface, the phase segregation of these segmented macromolecules can be used to create proteins patterns. In dispersion, on the other hand, a variety of aggregate structures can be obtained. The properties of these materials are dictated by a combination of amphiphilicity and the function of the biomacromolecular component. Recent progress includes, among others, the formation of large vesicle-like structures that contain active enzyme of which the activity depends on the type and molecular weight of the hydrophibic polymer.[1]. A.J. Dirks, R.J.M. Nolte, J.J.L.M. Cornelissen Adv. Mater. (2008) 20, 3953.[2]. I.C. Reynhout, J.J.L.M. Cornelissen, R.J.M. Nolte J. Am. Chem. Soc. (2007) 129, 2327.
4:00 PM - MM2.5
Peptide-Mediated Deposition of Nanostructured TiO2 into the Periodic Structure of Diatom Biosilica and its Integration into the Fabrication of a Dye-Sensitized Solar Cell Device.
Clayton Jeffryes 1 , Tim Gutu 2 , Haiyan Li 2 , Jun Jiao 2 , Gregory Rorrer 1
1 Chemical Engineering, Oregon State University, Corvallis, Oregon, United States, 2 Physics, Portland State University, Portland, Oregon, United States
Show AbstractDiatoms are single-celled algae that make silica shells called frustules that possess periodic structures ordered at the micro- and nanoscale. Nanostructured TiO2 was deposited onto the frustule biosilica of the diatom Pinnularia sp. Poly-L-lysine (PLL) conformally adsorbed onto surface of the frustule biosilica. The condensation of soluble Ti-BALDH to TiO2 by PLL-adsorbed diatom biosilica deposited 1.32 ± 0.17 g TiO2/g SiO2 onto the frustule. The periodic pore array of the diatom frustule served as a template for the deposition of the TiO¬2 nanoparticles, which completely filled the 200 nm frustule pores and also coated the frustule outer surface. Thermal annealing at 680 oC converted the as-deposited TiO2 to its anatase form with an average nanocrystal size of 19 nm, as verified by XRD, electron diffraction, and SEM/TEM. This material was then integrated into a dye-sensitized solar cell device. Specifically, a single layer of diatom-TiO2 frustules was deposited to surface density of 15 microgram TiO2/cm2 on top of an anatase TiO2 nanoparticle layer deposited to surface density of 2.5 mg/cm2 on conductive ITO glass. The composite structure was thermally annealed at 400 C, followed by addition of N719 dye, I3 electrolyte, and Pt back electrode. A relative increase in short-circuit current of nearly 50% was observed after deposition of the diatom-TiO2 layer. The difference was not due to the increase in the amount of TiO2 in the device, because the amount of diatom-TiO2 was small (<1%) relative to the anatase TiO2 base layer. Instead, the periodic structure of the intact frustule pores may have helped to improve photon capture. This is the first reported study of directing the peptide-mediated deposition of TiO2 into a hierarchical nanostructure using a biologically fabricated template. This study also illustrates how these materials can be integrated into device structures.
4:30 PM - **MM2.6
Synthesis and Characterization of Elastin Mimetic Hybrid Polymers with Alternating Molecular Architecture and Elastomeric Properties.
Xinqiao Jia 1
1 Materials Science and Engineering, University of Delaware, Newark, Delaware, United States
Show AbstractWe are interested in developing elastin mimetic hybrid polymers (EMHPs) that capture the multiblock molecular architecture of tropoelastin and the remarkable elasticity of mature elastin. In this study, multiblock EMHPs containing flexible synthetic segments based on poly(ethylene glycol) (PEG) alternating with alanine-rich, lysine-containing peptides were synthesized by step growth polymerization using telechelic azido-PEG and alkyne-terminated KA3K peptide, employing orthogonal click chemistry. The resulting EMHPs contain an estimated 5 repeats of PEG and KA3K, and have an average molecular weight of 34 KDa. Covalent cross-linking of EMHPs with hexamethylene diisocyanate (HMDI) through the lysine residue in the peptide domain afforded an elastomeric hydrogel (xEMHP) with a compressive modulus of 0.12 MPa when hydrated. The mechanical properties of xEMHP are comparable to a commercial polyurethane elastomer (TecoflexTM SG80A) under the same conditions. In vitro toxicity studies showed that although the soluble multiblock copolymers exhibited some toxicity at high concentrations, due partially to the presence of high charge density, the cross-linked hybrid elastomer did not leach out any toxic reagents and allowed primary porcine vocal fold fibroblasts (PVFFs) to grow and proliferate. These materials are promising candidates for applications as tissue engineering scaffolds in vocal folds as well as other mechanically active tissues.
5:00 PM - MM2.7
Using Double-Stranded DNA Probes to Assemble and Disassemble Colloidal Satellite Structures at Room Temperature.
Bryan Baker 1 , Valeria Milam 1 2 3
1 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractDNA-mediated assembly of particles has been a widely popular area of study in the past decade. Owing to the specific recognition between complementary DNA sequences, particles can be directed to assemble into defined structures based on DNA hybridization events between complementary surfaces. The current study continues to explore this bio-inspired area of research using DNA hybridization to generate colloidal satellite structures consisting of large microspheres surrounded by a monolayer of nanoparticles. By varying the sequence length and affinity of each DNA duplex linkage or double-stranded probe on the nano-scale, we can tune the degree of microsphere-nanoparticle attraction within these micro-scale satellite structures to be weakly stable at room temperature. Upon incubation with a specific DNA target sequence under ambient conditions, the satellite structures disassemble due to competitive hybridization events in which the original immobilized partner strand is replaced by the soluble target sequence. We have found that the kinetics of these competitive hybridization events depends on the differences in base-length and fidelity in base-pair matches between the original partner strand and the soluble targets. Thus, by tuning the affinity of the double-stranded probes bridging the particles, we have been able to generate weakly stable satellite assemblies while controlling the kinetics of competitive hybridization that underlies disassembly.
5:15 PM - MM2.8
DNA-based Polymers and Liquid-like Hydrogel by Target-driven Polymerization.
Jong Bum Lee 1 , Young Hoon Roh 1 , Dan Luo 1
1 Biological Eng., Cornell Univ., Ithaca, New York, United States
Show AbstractDNA, with its outstanding specificity and intrinsic biocompatibility, has been utilized as a new building block in the construction of polymers and hydrogels. Here we report DNA-based soft materials from micro- (DNA-based polymers) to macroscale (liquid-like DNA hydrogels) by target-driven polymerization. The polymers were generated only in the presence of a specific DNA by assembling a single photo-responsive moiety on a DNA monomer with nanoscale precision and then introducing the system to UV light. This precision allows for specific and sensitive pathogen sensing. In the macroscale, liquid-like DNA hydrogel was enzymatically created in the presence of specific target DNA used as a template deriving elongated DNA via polymerase. A gelling process was based on the physical interactions of long DNA strands as opposed to base pairing. These biocompatible DNA hydrogels were almost fluidic-like but still held gel properties. They were easily able to be transformed back and forth to any shape depending on the mold. Inspired by these characteristics of liquid-like DNA hydrogels, we have developed an injectable extracellular matrix for tissue engineering.
5:30 PM - MM2.9
Enzyme-Assisted Self-Assembly of Defined Peptide Nanostructures
Apurba Das 1 , Rein Ulijn 1
1 Department of Pure & Applied Chemistry, The University of Strathclyde, Glasgow United Kingdom
Show AbstractDesign and construction of various nanostructured materials using molecular self-assembly is a very active area in current research for biological and non-biological applications. It is a major challenge to control the self-assembly process (nucleation and growth of nanostructures) and to avoid kinetically entrapped aggregates under physiological conditions. Enzymes have recently emerged as tools to achieve this by converting non-assembling precursors into self-assembly building blocks in a space/time controlled fashion. Enzyme-controlled hydrogelation is particularly attractive for biomedical applications of hydrogels in drug delivery, 3D cell culture and diagnostics and supramolecular electronics.Peptide-based biomaterials are attracting interest due to their programmable and biodegradable nature. A number of Fmoc (fluorenyl-9-methoxycarbonyl) based amino acids and dipeptides form excellent supramolecular hydrogelators due to their hydrogen bonding and pi-pi interactions. We explore the use of hydrolytic enzymes to direct self-assembly of nanostructures based on aromatic short peptide derivatives. Two complementary approaches were followed (i) esterase-directed self-assembly via hydrolysis of N-(fluorenyl-9-methoxycarbonyl) (Fmoc)-peptide esters, (ii) thermolysin assisted self-assembly of nanofibrous hydrogels based on Fmoc-peptide-esters formed via a process known as reversed hydrolysis.1 Different types of nanostructures including tubes, fibers and twisted sheets were obtained depended both on the route of self-assembly and the chemical nature of the building blocks, highlighting the versatility of using aromatic short peptide derivatives in self-assembly. Interestingly, the first method allows the consequent formation of nanotubular structures with tunable diameter for different Fmoc-peptide building blocks. In each case, the self-assembly of Fmoc-peptides was driven by hydrogen bonding interactions forming β-sheet structures combined with pi-pi interactions of the aromatic fluorenyl groups as confirmed by FT-IR and fluorescence spectroscopy respectively. These self-assembled pi-conjugated peptide nanostructures can serve as a tool to find for supramolecular electronics.Reference:1. A. K. Das, R. Collins and R. V. Ulijn, Small, 2008, 4, 279.
5:45 PM - MM2.10
Self-assembly of π-conjugated Oligomers onto ssDNA Templates via Hydrogen-bonding.
Mathieu Surin 1 , Pim Janssen 2 , Roberto Lazzaroni 1 , Philippe Leclere 1 , Bert Meijer 2 , Albert Schenning 2
1 Laboratory for Chemistry of Novel Materials, University of Mons-Hainaut, Mons Belgium, 2 Laboratory for Macromolecular and Organic Chemistry, Eindhoven University of Technology , Eindhoven Netherlands
Show AbstractPi-conjugated oligomers and polymers are the central ingredients in the field of ‘organic electronics’ and offer new opportunities for devices such as solar cells and field-effect transistors, with the advantage of easy-processability and mechanical flexibility of organic materials. For tailoring the optical and electronic properties of those materials, the control over the assembly of conjugated molecules at the nm-scale is of major importance. An elegant way to direct the supramolecular order of conjugated molecules is to make use of a well-defined template. In this view, DNA is a remarkable building block to construct well-defined nano-objects because of the control in the design of its architecture and the high specificity of the base recognition process.[1] Furthermore, the base-by-base synthesis of oligonucleotides makes it possible to control both their length and their sequence from a few to more than one hundred bases. In this study, we propose to fabricate π-conjugated molecular stacks for which the size, the shape, and the intermolecular interactions are controlled by a self-assembly process guided by a well-defined single-stranded oligonucleotide template. This is realized by mixing in aqueous solution a defined single-stranded DNA (ssDNA) with a hydrophilic pi-conjugated oligomer (e.g., an oligo(phenylene vinylene)) bearing a complementary H-bonding moiety.[2] This bottom-up approach leads to hybrid, fully-bound structures for which the size is controlled by the length of the oligonucleotide. We characterize these supramolecular structures via a joint theoretical and experimental approach: atomistic modeling based on Molecular Dynamics is carried out to propose structural models that can be related to Circular Dichroism spectroscopy and Tapping-Mode Atomic Force Microscopy measurements. By modifying the nature of the conjugated oligomers that self-assemble onto the ssDNA, we obtain hybrid structures that differ in terms of the helical pitch of the strand, the amplitude of the intermolecular interactions, the assembly on surfaces, etc. [3,4] This is essential for exploiting these functional structures into optoelectronic devices and for the future design of hybrid systems with different chromophores (e.g., conjugated electron donors and acceptors) fine-positioned along the DNA strand. [1] a) N.C. Seeman, Nature 2003, 421, 427 ; b) F.A. Aldaye, A.L. Palmer, H.F. Sleiman, Science 2008, 321, 7195.[2] P.G.A. Janssen, J. Vandenbergh, J.L.J. van Dongen, E.W. Meijer, A.P.H.J. Schenning, J. Am. Chem. Soc. 2007, 129, 6078-6079.[3] G.P. Spada, S. Lena, S. Masiero, S. Pieraccini, M. Surin, P. Samorì, Adv. Mater. 2008, 20, 2433.[4] M. Surin, P.G.A. Janssen, R. Lazzaroni, Ph. Leclère, E.W. Meijer, A.P.H.J. Schenning, Adv. Mater. 2008, in press (DOI: adma.200801701).
MM3: Poster Session: Synthesis of Bio-inspired Hierarchical Soft and Hybrid Materials
Session Chairs
Nicholas Kotov
Christopher Li
Fiona Meldrum
Shu Yang
Tuesday PM, April 14, 2009
Exhibition Hall (Moscone West)
6:00 PM - MM3.1
Physicochemical and Dielectric studies of the Hydration Mechanism in Proteins (Casein and Lysozyme).
Kalliopi Vartzelis-Nikaki 1 , Sotiria Krypotou 1 , Amalia Konsta 1
1 , National Technical University of Athens, Athens Greece
Show AbstractThe hydration and proton transport mechanisms in casein and lysozyme powders are studied by means of physicochemical and dielectric spectroscopy methods, using: a) Equilibrium and dynamic water sorption isotherms, b) Differential scanning calorimetry (DSC), c) Thermally stimulated depolarization currents (TSDC) techniques in the temperature range from 77 to 300 K and d) Dielectric relaxation spectroscopy (DRS) in the frequency range 10-106Hz. The water content of the samples varied between 0.07 and 0.61 w/w.The experimental results of equilibrium water sorption were analyzed on the basis of the GAB equation and the tightly bound water percentage was approximately evaluated from the analysis. From dynamic water sorption isotherm the diffusion coefficients of water during sorption and desorption in our samples were determined.A detailed analysis of the peaks obtained by TSDC and DRS techniques permitted us to determine the hydration content corresponding to water irrotationally bound to the protein macromolecule, as well as the level as which percolative proton transfer along threads of hydrogen-bonded water molecules in the surface of protein macromolecules sets on, depending on the protein nature. A peak attributed to localized short range hopping of protons through the bulk sample has also been detected. Using special dielectric techniques, Arrhenius plots have been recorded and activation energies for the various processes, as a function of water content, have been determined. The role of glass transition temperature, as detected by DSC, on the onset of proton transport is emphasized and the behaviour of dc-conductivity, as well as its role on the biological function of living organisms, is further discussed.
6:00 PM - MM3.10
Perspective of Using the Biopolymers for Management Nanostructure and Functional Properties Fat-containing Food Products.
Tamara Rashevskaya 1 , Anatoliy Ukraines 1
1 Department of products from milk, NUFT(National University of Food Technologies), Kyiv Ukraine
Show Abstract One of most actual social problems of our time is creation of technologies of foodstuff of functional purpose which are directed for protection and preservation of health of the population. The special attention is paid at the use of food additives from vegetative raw material. We create kinds of a butter with biopolymers pectin and inylin, which are received from vegetative raw material. By the results of clinical tests the kinds of butter are recommended by Ministry of Health of Ukraine in the treatment-and-prophylactic purposes and an improving in health feed. Complex researches have shown, that weedsakhared pectin and inylin in butter`s heterosystem are surface-active substances. Micro-and nanostructure of butter consists of crystal aggregates, nanoblocks and nanograins, which are formed during its self-organization.The mechanism of nanostructure`s self-organization is based on phase transformations and fractionating of glycereds. The hierarchy of self-organizing of nanostructure of butter is offered. The crystal fatty phase`s initial stage of formation is formation of crystals embryos made from highly melting glycered. During the growth of nanograins, nanoblocks and aggregates occurs fractionating of glycerids on temperatures of hardening, conformation and polimorphism to forms,Identical glycered are packed in lamelle;uncrystaled glycered and a water phase with the biopolymers dissolved in it make a start on periphery. Crystal nanograins d=5-10 nm form lamelle, the adsorptionis layers of biopolymers and a water phase are formed on the lamelles interface. Nanostructure of crystal aggregates and nanoblocks consists of alternating lamelles of nanograins and layers of water phase.The polysugated amorphous-crystal lipid layer is formed on the surface of aggregates and nanoblocks. It is established, that adding such polysugareds pectin and inylina leads to crushing the structural elements of butter at 5-25 × the most part of them are in nanosize range of 1-100 nm.Thus the quantity of a water phase, disparhyriesed on nanolevel increases for 60 %, that brakes microbiological and oxidizing processes of a product`s damage and accordingly raises its biological interface.Thus increasing of the butter`s biological value butter (with pectin and inylin) is connected with functional properties of these biopolymers, and with features nanostructure`s of these kinds of butter. The above-stated testifies to perspectivity of using of the biopolymers for butter`s and other fat-containing food products management of nanostructure and functional properties and also creation of the butter`s and food product`s interface nanotechnologies.
6:00 PM - MM3.11
Nanostructure Interfaces of Phases and Nanoelements Multicomponent Lipid System.
Tamara Rashevskaya 1
1 Department of products from milk, NUFT(National University of Food Technologies), Kyiv Ukraine
Show Abstract The formation of the lipid systems' nanostructure multicomponent is investigated by the example of butter. On the result of complex researches it is established, that in the process of butter formation ,the formation of butter's nanostructure occurs on a method "from down to up". Nanostructure of a continuous fatty phase of a fresh-made aggregates consists of crystal glycered layers and set of layered many-sided crystal aggregates in size 1000 - 2600 nm. The crystal glycered layers and layers of aggregates consist from monomolecular glycered layers;their thickness is 5 nm; their surface has a lamelle structure.Lamelle are generated from mono - and biolayers of glycered. By electrono - positrono method angilation there were found out nanoporu r ~ 0,22-0,56 nm in dairy-fat structure. The most probable and steady radius of nanoporu is 0,35 nm; it is specified that nanoporu have fylerenosimilas structure.There are indentificate nanoparts waters on electrono - microscopic pictures nanostructure, are formed by the centers of their nanoporu. They are formed from nanoporu paralele crystal layers.On nanocapitals nanostructure's the product difindates continuous water phase. The borders of the amorphous and crystal layers nanogreins' and phases' aggregates of fat have rough with ledges surface; ther are formed nanodrops of moisture adsorptionis connection of moisture's films. During the storage of butter the self the organization nanostructure on a method "from down to up" occurs where crystal units are brocken into nanoblocks, size 40-800 nm. The formation of layered aggrgats and nanoblocks is based on glycered's fractionis. More fusible glycered make a start front cristalisation. On a surface of aggregats and nanoblocks amorphously - a crystal layer is formed, and on the surface of their crystal layers nanoparts water phase form, d ~ 3-50 nm; their size decreases with easilyfusibility glycered increasing; they are forming a surface. Adding the vegetative food additives the size of nanoelements decreases by 5 - 25 times, changes nanostructure crystal layers which architecture is influenced by the nature of the additive. So surfaces of crystal layers of aggregats and fatty globul (with the additive food inylina) have butter dentred nanostructure: an external surface - convex and inside of - concave which are connected by a principle, a ledge to a hollow. During the formation of the butter's nanostructure occurs fractionis inylina. The crystal nanoblocks include nanolayers with a various phase condition: crystal, amorphously crystal, amorphous and liquid crystal with structure smektives phases. They have various structure: dentred, string - like, fibrilarated, globularated. In nanostructure of butter with pectin superficial pectino - lipid layers of nanoblocks and fatty globul aggegates consist of cambers, many-sided nanocristal and cells,there size is up to 100 nm with nanoparticle and films of water phase on surfaces of borders of the aggregates.The results of researches have shown that the nanostructure surfaces of nanoelements and their borders of the aggregates are influenced by the nature brought additives storage period of the product that allows to operate the architecture and interactions surfaces nanoelements and also the physical and chemical properties of the materials.
6:00 PM - MM3.12
Nanodiamond-Embedded Hydrogels as Therapeutic Sequestering Matrices for Localized and Sustained Bioactivity.
Robert Lam 1 , Mark Chen 1 , Eiji Osawa 2 , Dean Ho 1 3
1 Biomedical Engineering and Mechanical Engineering, Northwestern University, Evanston, Illinois, United States, 2 , NanoCarbon Research Institute, Nagano Japan, 3 Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois, United States
Show AbstractIn this work, we describe a novel material consisting of embedded doxorubicin hydrochloride (DOX)-nanodiamond (ND) conjugates in poly(ethylene glycol) diarylate (PEGDA)-based hydrogels. NDs have recently been examined for biomedical applications due to their unique combination of size, aspect ratio and surface properties. NDs have been previously bound to numerous biological agents. In particular, we have previously attached 2-8 nm NDs with DOX, a well known chemotherapeutic ideal for drug release assays studies due to its innate UV-vis spectra absorbance. The polymer matrix we have chosen is PEGDA, due to the innate water solubility, versatility and ease of modifying density, pore sizes and functional attachment groups. The interplay between the components can be adjusted to obtain eventual desired sequestration or release kinetics. The hydrogels are formed via UV photopolymerization, thereby creating a matrix potentially applicable towards a variety of biomedical applications, including chemotherapy, regenerative medicine, and wound treatment. ND-PEGDA hydrogels were demonstrated to sequester drug extremely well in comparison to ND deficient hydrogels. Release assays consisted of immersion of hydrogels of different compositions with and without NDs in PBS and water at physiological conditions in triplicate. Standard hydrogels were shown to elute the majority of their payload within the first couple days in a seemingly diffusion based manner while hybrid gels that contained NDs showed a controlled and constant release for up to two weeks that avoided an initial “burst” release profile. In fact, ND-deficient hydrogels were shown to release 20 times more drug than ND containing hydrogels. After two weeks, the majority of the DOX still remained in ND embedded hydrogels, demonstrating the powerful drug entrapment abilities of the ND surface. Current studies are underway to explore the driving drug-ND surface binding mechanisms and exploiting these factors for desired release triggers and rates.Characterization via Environmental Scanning Electron Microscopy (ESEM) showed uniform dispersion of nanoparticle features within the hydrogel matrix upon UV polymerization. This was due to the fact that DOX-ND conjugates were mixed with a PEGDA precursor solution prior to photopolymerization. In addition, the process is facile, requires little time and can be accomplished on a benchtop. Photopolymerized hydrogels have particularly exciting implications in in vivo applications, since gels can be formed in situ into complex shapes. Since NDs have the capacity to be bound with several therapeutic and imaging agents, we postulate potential applications with these hydrogels in adjuvant therapy that require imaging or localized and slow drug release capabilities.
6:00 PM - MM3.13
Morphology and crystallization of the poly(3-hydroxybutyric acid) /Tannic acid blends
Chean Su 1
1 Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung Taiwan
Show AbstractMiscibility and crystallization in blends of poly(3-hydroxyalkanoates) (PHAs) with tannic acid (TA) were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy ( SEM) and wide-angle X-ray diffraction (WAXD). The result of thermal analyzing revealed that the PHB/TA.PHB8V/TA and PHB12V/TA exhibited a homogenous phase and a composition-dependent glass transition temperature (Tg), indicating the blends are miscible. The dependence of the Tg on the composition of these blends were fitted by the Fox equation, Gordon-Taylor equation and Kwei equation. The q value of Kwei equation of these system are negative, showing an interaction existed. The k value of kwei equation is PHB12V/TA (B=-45.62 cal/cm3),PHB8V/TA (B=-40.12 cal/cm3) and PHB/TA (B=-23.4 cal/cm3), respectively. Furthermore, SEM showed that the morphology of these blends are homogenous phase. The results of SEM are equal to the results of DSC in these blends. To confirm the behavior of the specific interaction, FT-IR showed that there is a new absorbance peak at the wavenumber 1703 cm-1 regard as the feature of hydrogen bond. From a thermodynamic viewpoint, the strength of the specific interaction in a blend can be described by its interaction energy density parameter (B) which can be obtained from the depression in the equilibrium melting based on the Nish-Wang equation. On the morphology observation of PHAs/TA, PHB/TA, PHB8V/TA and PHB12V/TA have Malt-cross and ring-banded feature using POM. Twist and irregular feature increases with increasing crystallization temperature and blending proportion of TA. On the crystalline kinetics, the relative magnitudes of growth rate of spherulite is in order of PHB>PHB8V>PHB12V because PHV content of PHB-co-PHV increase steric hindrance. In the PHAs/TA blends, the hydrogen-bonding interactions between PHAs and TA, which resulted the growth rate of spherulite of the blends decreased quickly as TA content added.
6:00 PM - MM3.14
Selection of specific ZrO2-interacting Peptides using Phage Display
Dirk Rothenstein 1 , Joachim Bill 2
1 Materials Synthesis and Microstructure Design, Max-Planck-Institute for Metals Research, Stuttgart Germany, 2 Institute of Non-Metallic Inorganic Materials, University of Stuttgart, Stuttgart Germany
Show AbstractZirconium-based oxide ceramics are commonly applied as key active component in a broad field of technical applications, e. g. as ion conductors in sensing devices and fuel cells or scaffolding parts of dental implants. Conventional ceramic processing is connected with energy-intensive reaction conditions and the use of elaborated technical equipment. Contrasting man-made oxide ceramics the biomineralization of elaborate mineral structures by various living organisms is achieved under ambient conditions. Such mineralized hard tissues, consisting of carbonate, phosphate, or silicate compounds are composite materials of a mineral and an organic phase. Generally, the organic phase consists of one or more protein species which functions as scaffold and controlling substance presumably through boundary layer interactions. Up to the present, zirconium dioxide (ZrO2) was not detected in biominerals. Therefore, a straight forward approach to isolate naturally occurring proteins, which influence the mineralization of ZrO2 is not possible.By means of industrial biotechnology we aim to benefit the advantages of biomineralization processes in technical oxide ceramic synthesis. A phage display system was adapted to identify peptides, which specifically interact with defined crystal planes of single crystals als well as with powders made of ZrO2. Isolated peptides were analysed by bioinformatics and experimentally scrutinized to influence the mineralization from zirconium salt solutions under mild reaction conditions. The resultant materials were analysed using electron microscopy and diffraction methods.
6:00 PM - MM3.15
Fluorescent Organic Nanotubes for Biosensory Platform
Chiyoung Park 1 , Jeong Hun Lee 1 , Hyehyeon Kim 1 , Chulhee Kim 1
1 Department of Polymer Science and Engineering, Inha University, Incheon Korea (the Republic of)
Show Abstract A self-assembly approach using suitable building blocks is a powerful strategy not only to construct nano-architectures but also to control materials properties through bottom up approach. Here, we report on the facile methodology to construct nanotubes with tunable surface functionalities derived from self-assembly of dendrons and cyclodextrins (CDs). In addition, we demonstrate that this type of fluorescent organic nanotubes with functionally controllable surface can be utilized as a useful tool for the construction of nanotube-nanoparticle hybrid, supramolecular biological assembly, and bioensory vehicle. As a primary building block, the amphiphilic amide dendron with the focal pyrene unit formed a vesicular structure in an aqueous phase. The assembly process can be regulated by various factors such as hydrophobic effect, hydrogen bonding, and host-guest interaction. The inclusion of the focal pyrene moiety into CDs with various C-6 functional groups at the narrower rim induces self-assembled functional nanotubes of which the surface is covered with CDs, therefore the surface can be functionalized with C-6 moieties of CD building blocks. The nanotubes with amine or carboxyl surface functionalities were effectively utilized as the nanotemplate for the orientation and direct nucleation of metal nanoparticles. The programmed assembly and fluorescence characteristics of the functional CD-covered dendron nanotubes enabled us to utilize this new type of nanotube as a platform for protein sensing.
6:00 PM - MM3.16
Self-assembly Formation of Multiple Tethered Lipid Bilayers.
Seyed Ruhollah Tabaei Aghda 1 , Magnus Branden 1 , Fredrik Hook 1
1 Applied physics, Chalmers university, Göteborg Sweden
Show AbstractTethered lipid bilayers have been proven powerful as experimental models in studies of membrane-spanning proteins, which are currently the most important targets in drug discovery. Tethering of planar lipid membranes reduces the influence from the solid support on the lateral mobility of the membrane constituents and provides a sufficiently large solvent reservoir underneath the membrane for studying molecular transport events. Inspired by cell-cell junctions, where membrane residing proteins control the separation between two or more membranes without interfering with their integrity, we developed a new self-assembly route for formation of multiple macroscopically homogenous and highly fluid tethered lipid bilayers (lipid diffusivity~5 μm2/s) with compartmentalized inter-membrane volumes geometrically confined by membrane-anchored DNA duplexes. The formation of multiple macroscopically homogeneous planar membrane-membrane junctions with sealed inter-membrane liquid reservoirs was accomplished using so called bicelles, which is a versatile class of model membranes generally composed of a mixture of the long-chained dimyristoyl phosphatidylcholine (DMPC) and the short-chained dihexanoyl PC. Quartz crystal microbalance with dissipation (QCM-D) was used to monitor the formation of such architectures and to study of their ion permeability.
6:00 PM - MM3.18
Electrochemically Active Vesicles.
Hoon Kim 1 , Ji-Woong Park 1
1 , gist, Gwangju Korea (the Republic of)
Show AbstractWe report the formation of electrochemically active vesicles by the rod-coil polymers consisting of a tetraaniline (TANI) block and a polyethylene glycol (PEG) block. Two diblock polymers of TANI-b-PEG550 and TANI-b-PEG2000 with respective molecular weights (MW) of PEG blocks, 550 and 2000, and a triblock polymer, TANI-b-PEG-b-TANI with the MW of its PEG block, 600, were synthesized by coupling of TANI and polyethylene glycol monocarboxylic acid. All three rod-coils were characterized in their aqueous solution with concentration of 0.001~0.005 wt%. Dynamic light scattering (DLS) data of their solutions indicated the presence of large particles with diameter ranging from several hundred nanometers to a few micrometers. Optical microscopy of the solution also gave clear images of the vesicles. Transmission electron microscopy (TEM) of rapidly evaporated sample on carbon coated TEM grids exhibited the images of collapsed vesicles with size of 1~2μm. We studied morphological transition of the vesicles by addition of oxidizing or reducing agents to the vesicular solutions. Detailed characterization of electrochemical properties as well as the solution behaviors of the vesicles will be presented. This work was supported by the Program for Integrated Molecular Systems (PIMS) at Gwangju Institute of Science and Technology and the Korea Research Foundation Grant funded by the Korean Government (Grant KRF-2005-205-D00035).
6:00 PM - MM3.2
Supramolecular Assembly of Peptide Fibers Through Metal Coordination.
Madhumita Mukherjee 1 , Michael Ogawa 1
1 Chemistry, Bowling Green State University, Bowling Green, Ohio, United States
Show AbstractPeptide-based nanostructures play important roles in many areas of nanoscience and nanotechnology. Considerable effort is thus being devoted to better understand how the morphologies of such structures can be both predictively determined and rationally-controlled. Towards this end, our group has been exploring the use of transition metal chemistry to help direct the assembly of peptide structures in ways that may add to, and perhaps complement, the formation of native-like conformations (Biomacromol. 2007, 8, 3908).Reported here is the design, synthesis, and characterization of a new type of metal-peptide assembly prepared through the non-covalent self-association of amphipathic polypeptides that are coordinated to the axial positions of either Fe(III) or Co(III) protoporphyrin IX. The binding of the pyridine-containing peptide (AQ-Pal14) to the metalloporphyrin is monitored by UV-Vis spectroscopy which shows that the porphyrin Soret band loses intensity and undergoes a small, but distinct, red-shift upon the addition of peptide. This behaviour is accompanied by the appearance of an induced circular dichroism signal at 423 nm to indicate that the porphyrin ring is in close communication with the chiral peptide environment.Scanning Electron Microscopy (SEM) analysis of evaporated samples the peptide-porphyrin complex shows that these species form extended arrays of fiber bundles having having lengths that exceed several hundred microns. A closer examination reveals that these materials exist as bundles of smaller fibers which have diameters on the order of ca. 2 microns. The results show how metal coordination can be used to construct new types of peptide-based materials.
6:00 PM - MM3.20
Synthesis and Self-Assembly of Poly(diethylhexyloxy-p-phenylenevinylene)-b-poly(methyl methacrylate) Rod-Coil Block Copolymers.
Chun-Chih Ho 1 , Yi-Huan Lee 2 , Chi-An Dai 2 , Rachel Segalman 3 4 , Wei-Fang Su 1
1 Materials Science and Engineering, National Taiwan University , Taipei Taiwan, 2 Polymer Science and Engineering, National Taiwan University, Taipei Taiwan, 3 Chemical Engineering, University of California, Berkeley, Berkeley, California, United States, 4 Materials Sciences Division, Lawrence Berkeley National Laboratories, Berkeley, California, United States
Show AbstractA series of monodisperse poly(diethylhexyloxy-p-phenylenevinylene-b-methyl methacrylate) (DEH-PPV-b-PMMA) polymers were synthesized using Siegrist polycondensation and anionic polymerizations followed by “click” chemistry. Alkyne-terminated DEH-PPV and azide-terminated PMMA were synthesized first, and then the two functionalized polymers underwent 1, 3-cycloaddition reaction to obtain copolymers. Both the conversion of the end-functionalization of the homopolymers and the yield of the “click” reaction were higher than 98% as determined by 1H nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC). Transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) studies reveal the details of copolymer morphology. In previous studies of weakly segregated rod-coil copolymers, the rod-rod interaction dominated the phase behavior. The DEH-PPV-b-PMMA system presented here has higher block segregation strength and therefore offers new insight into the competition between rod-rod and rod-coil interactions that occurs in these systems. This competition results in new phase behavior. The DEH-PPV rods are organized as a monolayer that is inclined with the lamellar normal (smectic C) for the copolymers containing low volume fraction of PMMA coil (<54%). However, the DEH-PPV rods are organized as a strip and pack into hexagonal lattice with the coil for high coil fraction copolymers (>66%). The phase behaviors of the copolymers were studied using differential scanning calorimetry (DSC), polarized optical microscopy (POM) with heating stage, temperature varied wide angle X-ray scattering (WAXS), and temperature varied small angle X-ray scattering (SAXS). Upon heating the low coil fraction copolymers exhibit a series of clear transitions of smectic-lamellar to amorphous-lamellar to disordered structure. Whereas for the high coil fraction copolymers, two transitions of smectic-hexagonal to amorphous-hexagonal and smectic-hexagonal to disorder structure cannot be clearly differentiated. The order-to-disorder temperature (ODT) decreases slowly with increasing coil fraction while the smectic-to-isotropic transition (SI) temperature stays relatively unchanged. The steady SI temperature suggests the strong rod-rod interaction keeps the liquid crystalline behavior of DEH-PPV rod segment in the nanodomain structure regardless of the amount of coil segment in the copolymers. A complete phase diagram of this copolymer has been established basis on the theoretical results of phase behavior studies: Landau expansion theory and two-dimension self-consistent-field theory (2D-SCFT).
6:00 PM - MM3.21
Engineered Phage for Aligned Tissue Regenerating Materials.
Anna Merzlyak 1 2 , Seung Wuk Lee 1 3 4
1 Bioengineering, UC Berkeley, Berkeley, California, United States, 2 Bioengineering, UCSF, San Francisco, California, United States, 3 Physical Bioscience Division, Lawrence Berkeley National Lab, Berkeley, California, United States, 4 , Berkeley Nanoscience and Nanotechnology Institute, Berkeley, California, United States
Show AbstractIn this study we have demonstrated that genetically engineered M13 bacteriophage can be utilized to construct a novel tissue engineering material that is able to both support and influence cell growth. M13 bacteriophage (phage) are naturally occurring nanofiber-like viruses, which can self-assemble into directionally organized liquid crystalline structures due to their long-rod shape and monodispersity. Multifunctionality can be imparted on the phage by genetically engineering them to display a high density of peptides and therapeutic molecules on their major and minor coat proteins. We have engineered M13 phage to display cell-signaling peptides RGD and IKVAV as well as their nonspecific controls (RGE and IQVAV) on its major coat proteins. We then used the engineered phage as a building block for the construction of aligned nanofiber tissue regenerating materials. Through viability assays and microscopy studies we have verified that three- dimensional fibers spun from the engineered viruses can support cellular growth, proliferation and differentiation. With immunostaining studies we have demonstrated the specificity of interaction of the RGD- and IKVAV modified phage to the cells. Furthermore with the aid of SEM and bright-field microscopy we have demonstrated that the fabricated phage matrices self assembled into directionally organized structures, which in turn dictated the alignment and direction of cell growth. Finally we have begun expanding the functionality of the phage by simultaneously engineering its minor and major coat proteins, to allow for future delivery of therapeutic particles. Such multifunctional and structurally aligned phage matrices offer promising opportunities for therapies that address challenging medical problems, such as the regeneration of nerve tissue after spinal cord injuries, or as in vitro model systems for studying complicated cell signaling environments.
6:00 PM - MM3.23
Enzymatic Synthesis of Amorphous Calcium Phosphate-Chitosan Nanocomposites and its Processing into Hierarchical Structures.
Francisco del Monte 1 , Maria C. Gutierrez 1 , Matias Jobbagy 1 , Maria L. Ferrer 1
1 , ICMM-CSIC, Madrid Spain
Show AbstractBiomineralization offers the opportunity to produce highly organized nanocomposite structures, controlling specific architectures over extended length scales for a wide range of inorganic materials. Enzymatically assisted routes also offer the possibility to synthesize a number of materials with excellent control on the structural organization. In particular, HA precursors and different calcium carbonate precipitates could be obtained in solutions by enzyme-catalyzed decomposition of urea by urease. Furthermore, the gradual generation of base provided by urea hydrolysis has recently been used for the preparation of monolithic and homogeneous chitosan hydrogels. The homogeneous pH modulation besides the low temperature used for urea hydrolysis allow for the achievement of CHI hydrogels with a homogeneous 3D network structure with superior biotechnological performance than chitosan solutions gelled by neutralization with alkaline solutions, gaseous NH3 or dialysis. Here in, we applied the urease assisted hydrolysis of urea for the preparation of nanocomposites (of turbid appearance) based on calcium phosphate precipitates and CHI hydrogel (see Scheme I in downloaded file). The base generated by urea hydrolysis promoted both CHI gelation and calcium phosphate precipitation at biological temperatures (~37 degrees C). Otherwise (e.g., urea hydrolysis by thermal decomposition at 90 degrees C), CHI would undergo partial decomposition. Macroporous scaffolds (e.g.;, hierarchically organized) were obtained by a cryogenic process (named ISISA, ice segregation induced self-assembly) that simply consist on the unidirectional freezing (at -196 degrees C) of the hydrogel nanocomposites. Upon freezing, the ice formation (hexagonal form) causes every solute originally dispersed in the hydrogel to be segregated from the ice phase. After freeze-drying, the resulting hierarchical structures consists on well aligned micrometer-sized pores in the freezing direction corresponding to the empty areas where ice crystals originally resided, being the macrostructure supported by the matter (e.g., calcium phosphate nanoparticles dispersed within CHI matrix) accumulated between adjacent ice crystals. The excellent control on ice crystals formation, ice segregation matter and matter self-assembly between adjacent ice crystals allows ISISA for unique tailoring of the final macrostructural features of the resulting scaffolds. Thus, figure 1 (see at downloaded file) shows the porous channels of up to 90 microns that can be simply obtained by using different freezing rates in the application of the ISISA process to the hybrid hydrogel. The calcium phosphate nanoparticles entrapped within the CHI scaffold are identified as amorphous calcium phosphate as revealed by TEM, XRD and NMR experiments (see figure 1, right, at downloaded file).
6:00 PM - MM3.24
Fabrication of Nanoengineered Plasmonic Hybrid Systems for Bio-nanotechnology.
Kirsty Leong 1 , Melvin Zin 2 , Hong Ma 2 , Memet Sarikaya 2 , Alex K.-Y. Jen 2 1
1 Chemistry, University of Washington, Seattle, Washington, United States, 2 Materials Science and Engineering, University of Washington, Seattle, Washington, United States
Show AbstractUsing a protein enabling strategy and biomolecular recognition, surface plasmon enhanced tunable quantum dot (QD) nanoarrays are fabricated where a 25-fold and 40-fold increase in the QDs photoluminescence is observed. This is accomplished by spectrally tuning the localized surface plasmon resonance of gold nanopillars and exploiting their unique optical properties to modify their surrounding environment. Nine different unique geometric arrangements of gold nanopillars are arranged where the diameter is varied from 50 nm, 100 nm, and 200 nm with a tip-to-top distance spacing of 50, 100, 150, and 200 nm. Protein functionalized QDs are self-assembled onto the nanopillars in a step-wise fashion with a concomitant incremental increase in separation from the metal surface using gold binding polypeptides as a fusion partner and biotin-steptavidin spacer units. The highest QD emission intensity is observed at a QD-metal distance of ~17.50 nm when attached onto smaller gold nanopillars. The stronger near-field coupling interactions between neighboring nanopillars spaced at a tip-to-tip distance of 50 and 100 nm gives rise to higher emission intensity. At larger tip-to-tip distances, the nanopillars interact through far-field dipolar interactions thus behaving independently rather than collectively. The QDs emission intensity is further enhanced by sandwiching the QDs in between the local electromagnetic fields of two metal nanoparticles at equal QD-metal distances. In addition to enhancing the QD emission intensity, QD-dye hybrid assemblies are fabricated using these surface plasmon enhanced QD nanoarrays to demonstrate surface plasmon assisted Förster resonance energy transfer (FRET). The QDs-dye hybrid system exhibits an 80% increase in energy transfer rates from a donor (QD) to an acceptor (dye) compared to nonmetal QD-dye systems. The overall approach allows for a comprehensive control both laterally (lithographically defined nanostructures) and vertically (QD-metal distance) of the collectively behaving QD-nanostructure assemblies. Thus the use of metal nanostructures can enhance the photoluminescence of nearby fluorophores and FRET between a donor and acceptor chromophore in order to create optimally integrated systems for a variety of applications in bio-nanotechnology.
6:00 PM - MM3.25
Harnessing Mechanical Nanopatterning of Microenvironments by Cells with Matrix Compliance.
Nathaniel Huebsch 1 2 , Praveen Arany 1 , Angelo Mao 1 , Jose Rivera-Feliciano 1 , David Mooney 1
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 2 Division of Health Sciences and Technology, Harvard-MIT, Cambridge, Massachusetts, United States
Show AbstractFunctional complexity is a critical requirement for tissue engineering scaffolds, as such materials must function as local micro-environments which provide programming cues to host or transplanted cells. One approach to this goal is the design of complex, synthetic analogs of the natural extracellular matrix (ECM). Both the specific composition of receptor-binding adhesion epitopes presented by such materials and the nanoscale heterogeneity in their presentation, have demonstrated effects on cell behavior. In a seemingly unrelated observation, a variety of cell types, including mesenchymal stem cells (MSCs), change their behavior in response to the mechanics of their micro-environment. While mechanisms for cell responses to specific molecular adhesion epitopes are well established, the biophysical means through which cells sense and ultimately respond to the mechanical properties of the ECM are incompletely understood. We hypothesized that matrix mechanics might affect cell fate partially by controlling the formation of receptor-adhesion ligand bonds. To test this hypothesis, we assessed formation of bonds between MSCs and biomimmetic RGD-peptides grafted to 3D alginate hydrogels using a FRET-based technique. Strikingly, the number of RGD-integrin bonds indeed depended on matrix compliance, but in a biphasic manner that was independent of the specific type of alginate polymer or crosslinking molecule. Further analysis revealed that enhanced binding to RGD correlated not with microscale changes in MSC morphology but rather with their ability to exert traction forces to reorganize RGD peptides on the nanoscale. This suggests that stem cells can nanopattern their microenvironment in a mechanically regulated fashion. Consistent with that hypothesis, bond formation, along with matrix reorganization, was decoupled from ECM mechanics with drugs that inhibit cell traction.We speculated that this mechanical nanopatterning, by increasing the structural complexity of the ECM, would engender the micro-environment with functional complexity. Thus, we examined the effects of ECM elastic modulus on the specific receptors MSC used to bind RGD and on their lineage specification. Consistent with historical data, the α5-integrin could not act as an RGD receptor in 2D – however, in 3D matrices, this receptor bound RGD in a mechanically-dependent manner. MSCs’ ability to form α5-integrin-RGD bonds had important consequences on their fate, as their differentiation to osteoblast-like phenotype correlated with the α5-integrin-RGD bond formation, whereas differentiation toward adipocyte-like cells was optimal in softer matrices. This work highlights a role for stem cells, not only in terms of their ability to respond to complex biomaterials, but also in terms of their ability to transform simple template materials into information-rich, structurally complex materials in-situ.
6:00 PM - MM3.26
Reversible Alginate Sponge for 3D Cell Culture.
Zhensheng Li 1
1 , Invitrogen Corporation, Frederick , Maryland, United States
Show Abstract AlgiMatrix is a product designed in Invitrogen as a tool to guide the formation of 3D spheroids or interconnected aggregates, which can be used for tissue engineering, drug screening, bioproduction and tumor metastasis research. Alginate, a defined polysaccharide extract from brown seaweed, is the main chemical component. With a modified lyophilization technology, it was made as porous sponge like structure and manipulated by two providing buffers. One buffer maintains the sponge structure, while the other one can dissolve oe soften sponge in medium. Both buffers works at neutral physiological conditions and reverse each other to control the sponge compliance and transparency, which makes the sponge very unique and flexible for 3D cell culture. This product is animal origin free, completely biocompatible and biodegradable. It can be used for RUO (research use only), IVD (in vitro diagnostic) and even clinic later on. It is going to lead the market of 3D cell culture to a new level.
6:00 PM - MM3.27
Patterned Biomineralization on Polydiacetylene Arrarys of Various Functional Groups
Won-doc Lee 1 , Gil-Sun Lee 1 , Dong-june Ahn 1
1 Chemical and Biological Engineering, Korea University, Seoul Korea (the Republic of)
Show AbstractBiological organisms have unique abilities to nucleate, grow and organize biominerals which are being used as the essential body parts for their survivals. These abilities which are known as the biomineralization processes are usually achieved by the creation of proper organic matrices and the precipitation onto the matrices by the chemical interactions at the inorganic/organic interfaces. The in-vitro biomimetic synthesis of organic-inorganic composites produced by nature is a subject of much attention still being researched throughout these days.The most abundantly produced biominerals are calcite, aragonite and vaterite. These three biominerals classified by different crystal structures and possess distinctive properties. These biominerals consist of organic-inorganic hybride complex and shows the potential to be used as new material with high quality and performance that can be used in many fields of engineering. However, the discovery of specific optimal growing condition for biomineralization is still not cleared. In experiments, we made hollow tubes with the height and diameter of 5 mm and assembled them into close-packed pattern arrays. Then, the array water interface formed in each hole that is filled two-thirds with DI-water is deposited by solution coating with different polydiacetylenes(PDAs). Polymerization was performed in situ by UV (254 nm) irradiation. This results in two-dimensional polymer crystalline domains that are spanned by the linear polymer chains. We deposited patterned PDAs on the octadecyltrichloro-silane(OTS) coated slides by raising the height of the DI-water for the contact with the sample and the substrate. Then, growth for crystallization of calcium carbonate on the surfaces of patterned PDAs was carried out. From this experiment, we demonstrate for the first time that systematic combinational biomineralization becomes possible for farther understanding of crystal growth
6:00 PM - MM3.28
Single-Particle Tracking and Ca2+ -Triggered Fusion of Lipid Vesicles Tethered to a Fluid Supported Lipid Bilayer using DNA hybridization.
Lisa Simonsson 1 , Gudrun Stengel 1 , Peter Jonsson 2 , Fredrik Hook 1
1 Applied Physics, Chalmers University of Technology, Gothenburg Sweden, 2 Solid State Physics, University of Lund, Lund Sweden
Show AbstractThe diffusive dynamics and fusion of vesicles tethered to supported lipid bilayers (SLB) are key features in understanding the natural exocytosis process and for delivery of membrane constituents to real cell membranes or mimics thereof. We recently demonstrated efficient fusion of lipid vesicles induced by cholesterol-modified DNA zippers(1,2), which in a reductionist way mimics the natural protein-based fusion machinery. It was previously shown by us and others that lipid vesicles tethered to SLBs via DNA hybridization display lateral diffusion. In this paper we show that by tethering vesicles to an SLB in a zipper-like manner, vesicle fusion with the underlying bilayer can be induced upon addition of Ca2+. The tethered lipid vesicles (Ø~100 nm) and the fusion process were visualized using total internal reflectance fluorescence (TIRF) microscopy and single-particle tracking was used to investigate the influence of the number of DNA tethers on the diffusive behaviour of vesicles tethered, using either fusogenic DNA zippers or non-fusogenic binding DNA. It was found that the average diffusion coefficient increases non-linearly with decreasing number of DNA strands per vesicle. Interestingly, at a critical number of DNA per vesicle, Ca2+ can be used to induce fusion of vesicles already tethered to a SLB. Combined with TIRF microscopy of the same region prior to and after addition of Ca2+, we currently explore the correlation between the lateral mobility and the on set of fusion, including its kinetics. Taken together, DNA-mediated fusion emerges as a promising tool for retroactive functionalization of artificial and biological membranes and may help to dissect the functional role of fusion proteins.1.Stengel, G.; Zahn, R.; Hook, F., DNA-induced programmable fusion of phospholipid vesicles. Journal of the American Chemical Society 2007, 129, (31), 9584-+.2.Stengel, G.; Simonsson, L.; Campbell, R. A.; Hook, F., Determinants for membrane fusion induced by cholesterol-modified DNA zippers. Journal of Physical Chemistry B 2008, 112, (28), 8264-8274.
6:00 PM - MM3.29
Nematic Ordering of Self-Assembled Nanowires Suspensions.
Tae Hee Han 1 , Ji Sun Park 1 , Ju Kyun Oh 1 , Sang Ouk Kim 1
1 Department of Materials Science and Engineering, KAIST, Daejeon Korea (the Republic of)
Show AbstractBionanofabrication, constructing nanostructures from biological building blocks is an emerging technology for generating functional devices. A variety of nanomaterials with diverse chemical or biological functionalities have been synthesized by utilizing highly specific biomolecular interactions. However, large-scale organization of those nanostructured biomaterials, which is critical for diverse applications, has rarely been explored yet. Here we demonstrate liquid crystalline peptide nanowires as novel materials for nanofabrication. The peptide nanowires individually dispersed in an organic solvent. The stable dispersion of peptide nanowires exhibited colloidal liquid crystalline phase for a broad concentration range, allowing the rapid alignment of peptide nanowires under an external field. Hierarchical organization of liquid crystalline peptide nanowires consisting of highly specific biomolecular assembly and nanoscale liquid crystalline ordering provides an efficient pathway to a novel bionanoarchitecture. The potential application of liquid crystalline peptide nanowires includes nanopatterning, reinforcing materials for nanocomposites, etc.
6:00 PM - MM3.3
Phase Transitions in Liquid Crystal Nanocolloids
Jing Zhou 1 , Christopher Spillmann 1 , Jawad Naciri 1 , Amy Blum 2 , Banahalli Ratna 1
1 Center for Bio/molecular Science and Engineering , Naval Research Laboratory, Washington, District of Columbia, United States, 2 Department of Chemistry, McGill University, Montreal, Quebec, Canada
Show AbstractLiquid crystal-based nanoparticles are a new class of material in which rod-shaped liquid crystal mesogens are stabilized and confined in a nanosized polymer matrix. These materials have great potential in nanoscale sensing, actuation and photonics due to their unique electrooptical properties. We are investigating the effect of nanoscale liquid crystal confinement on the phase behavior of the liquid crystals. We have synthesized nanoparticles containing a well known liquid crystal that exhibits a nematic phase, 4-pentyl-4-cyanobiphenyl (5CB). Using a mini-emulsion process, the 5CB is confined in a gel-like polymer network inside the nanoparticle. By varying the amount of crosslinker used for the polymer network, the rigidity of the nanoparticles can be changed and studied using atomic force microscopy. Thermal energy involved in phase transition of 5CB molecules in these gel-like nanoparticles is measured using differential scanning calorimetry and compared to the phase transition of the bulk material containing the same composition. Understanding the relationship between crosslinking density and liquid crystal phase behavior in nanoparticles will allow us to have better control of functions of these nanoparticles.
6:00 PM - MM3.5
Metabolic Insertion of Nanostructured TiO2 into the Patterned Biosilica of the Diatom Pinnularia sp.
Clayton Jeffryes 1 , Tim Gutu 2 , Jun Jiao 2 , Gregory Rorrer 1
1 Chemical Engineering, Oregon State University, Corvallis, Oregon, United States, 2 Physics, Portland State University, Portland, Oregon, United States
Show AbstractThis is the first reported study of using a living organism to controllably fabricate semiconductor TiO2 nanostructures imbedded within a hierarchical structure by a bottom-up self assembly process. Diatoms are single-celled algae that make silica shells or frustules with intricate nanoscale features imbedded within periodic two-dimensional pore arrays. A two-stage photobioreactor cultivation process was used to metabolically insert titanium into the patterned biosilica of the diatom Pinnularia sp. In Stage I, diatom cells were grown up on dissolved silicon until silicon starvation was achieved. In Stage II, soluble titanium and silicon were continuously fed to the silicon-starved cell suspension for 10 h. The feeding rate of titanium was designed to circumvent the precipitation of titanate in the liquid medium, and feeding rate of silicon was designed to sustain one cell division. The addition of titanium to the culture had no detrimental effects on cell growth and preserved the frustule morphology. Co-feeding of Ti and Si was required for complete intracellular uptake of Ti. Intact biosilica frustules were isolated by treatment of diatom cells with SDS/EDTA and then analyzed by TEM, STEM-EDS, and XRD. Although the frustule biosilica had a bulk TiO2 content of 4.0 wt%, titanium was preferentially deposited as a nanophase lining the base of each frustule pore, with estimated local TiO2 content of nearly 80 wt%. Thermal annealing in air at 720 C converted the biogenic titanate to anatase TiO2 with an average crystal size of 32 nm.
6:00 PM - MM3.6
Biological Fabrication of Photoluminescent Nanocomb Structures by Metabolic Incorporation of Germanium into the Biosilica of the Diatom Pinnularia sp.
Debra Gale 1 , Gregory Rorrer 1
1 Chemical Engineering, Oregon State University, Corvallis, Oregon, United States
Show AbstractDiatoms are single-celled algae that make microscale silica shells or “frustules” with intricate nanoscale features such as two-dimensional pore arrays. In this study, the metabolic insertion of low levels of germanium into the frustule biosilica of the pennate diatom Pinnularia sp. by a two-stage cultivation process induced the formation of frustules which strongly resembled double-sided nanocomb structures. The final product contained 0.2 to 1.0 wt% Ge in biosilica, depending upon the amount of soluble germanium added to the cultivation process. The 30 micron frustules consisted of a mixture of parent valves possessing a normal two-dimensional array of 200 nm pores, and daughter valves possessing the nanocomb structure formed by the fusion of the pore arrays. After thermal annealing in air, the Ge-doped frustules possessed blue photoluminescence (PL) with peak wavelength of 440-460 nm. The PL intensity was controlled by the annealing temperature and the level of Ge in the biosilica. The optimal PL intensity was obtained at a thermal annealing temperature of 400 C. XPS and TEM/electron diffraction measurements confirmed that Ge-doped diatom biosilica consisted of amorphous GeO2 after thermal annealing at 400 C. This nanostructured GeO2 was the likely the origin of the blue photoluminescence. This is the first reported study of using a cell culture system to biologically fabricate a Ge-doped silica nanocomb structure with controllable photoluminescent properties.
6:00 PM - MM3.7
Build-up Design of Artificial Antibody via Coiled-coil Peptide Assembly.
Mitsuo Umetsu 1 2 3 , Hiroyuki Koike 1 , Takeshi Nakanishi 1 , Izumi Kumagai 1
1 Department of Biomolecular Engineering, Tohoku University, Sendai Japan, 2 Center of Interdisciplinary Research, Tohoku University, Sendai Japan, 3 PRESTO, JST, Tokyo Japan
Show AbstractThe antibodies with high affinity are utilized in the fields of medicine and sensing, while the design of multispecific and multivalent antibodies resulted in the increase of the size of antibodies so that the expression of antibodies in bacteria and cells becomes hard. In this study, we report the in-vitro build-up production of multispecific and multivalent antibodies by clustering small antibody fragments via coiled-coil peptides. First, the variable region fragments of anti-GFP and anti-EGFR camel antibodies (anti-GFP VHH and anti-EGFR VHH, respectively) are assembled to a bispecific hetero VHH dimer, reversibly in response of nickel ion concentration, by the fusion of a paring coiled-coil peptide which is assembled with each other by the addition of nickel ion. The bispecific hetero VHH dimer spontaneously immobilizes GFP proteins on EGFR-displayed CHO cells, but not neat CHO cells. Further, we also cluster anti-EGFR camel antibodies on a ferritin to make a highly-multivalent antibody via coiled-coil peptides. We show the merit for the build-up design of artificial antibody via coiled-coil peptide assembly in terms of protein preparation and function.
6:00 PM - MM3.8
Novel Synthesis of Self Assembled DNA Nanotubes.
Rakesh Joshi 1 2 , Amrita Kumar 3 , Ashok Kumar 1 2
1 mechanical Engineering, ENB118, University of South florida, Tampa, Florida, United States, 2 Nanomaterials & Nanomanufacturing Research Center, University of South Florida, Tampa, Florida, United States, 3 Pathology, , Emory Univeristy School of Medicine, Atlanta, Georgia, United States
Show Abstract DNA nanotubes are the self assembled nanometer-scale circuits for bio-nanoelectronics. They can be targeted to connect at specific locations on larger-scale structures and can subsequently be metallized to form nanometer scale wires. DNA nanotubes fabrication techniques, reported so far, are the multi step procedures acompanied by long chain reactions. In this article we report a simple approach to construct the DNA nanotubes by implementing the concept of applying a suitable DC-bias to DNA - gold plating solution. Negatively chared double stranded DNA was used as precursor. The self assembled nanotubes fabricated by this method are attached to gold nanoparticles and expected to be the building blocks for highly efficient genosensors. Size of the nanotubes could vary form 30 nm to 300nm in diameter by simply changing the DC pulse duration whereas the nanotube length can be varied from 1 micron to 20 micron by changing the DC pulse value. The DNA nanotubes were found to be very stable at room temperature. Their growth and structure have been studied in detail using high resolution transmission electron microscopy and atomic force microscopy. The gold-DNA self assembly was studied using absorption spectra. Cyclic voltammetry was used to study gold–DNA formation as well as a tool to detect DNA concentration in the mixed solution.
6:00 PM - MM3.9
Controlled Peptide-Mediated Assembly and Formation of Hybrid Nanostructures.
Marketa Hnilova 1 , Alisa Carlson 1 , Turgay Kacar 1 2 , Chris So 1 , Hanson Fong 1 , Candan Tamerler 1 2 , Mehmet Sarikaya 1 2
1 Department of Material Science and Engineering and GEMSEC, University of Washington, Seattle, Washington, United States, 2 Molecular Biology and Genetics and MOBGAM, Istanbul Technical University, Istanbul Turkey
Show AbstractThe hybrid bi-material nanostructures with controlled optical properties have a wide spectrum of applications in nanotechnology and medicine, such as biosensing, molecular targeting, and bioimaging. Conventionally, bi-material nanostructures are produced in complex multistep processes usually involving relatively high temperatures, using organic solvents and strong reducing agents. A novel alternative to the currently used chemical processes may be the utility of genetically engineered peptides for inorganics (GEPIs) that have the capability of controlling both assembly and formation of various nanostructures. Previously, we selected gold- and quartz-binding peptide sequences (AuBP and QBP) using combinatorial peptide libraries. These peptides have high binding affinity onto respective solid surfaces and also catalytic activity in peptide-mediated biomaterialization experiments. Here we combine these sequences to produce a novel bifunctional peptide (QBP-AuBP). We first demonstrate the utility of the bifunctional peptide as a molecular linker to direct immobilization of gold nanoparticles onto the silica glass surface using self-assembly and soft lithography techniques. Then, we use the silica glass decorated with gold nanoparticles, acting as nucleation seeds, for subsequent gold formation by a peptide-mediated reduction procedure. Both systems form fundamental platforms for a variety of functional devices. Materials and nanostructures are characterized using dark field optical microscopy, scanning electron microscopy and atomic force microscopy. The approaches described here have implications in a wide range of potential applications including controlled assembly of hybrid composite nano- and molecular structures. Research is supported by NSF-IRES and MRSEC Programs through the University of Washington GEMSEC (DMR 0520567).
Symposium Organizers
Shu Yang University of Pennsylvania
Fiona Meldrum University of Leeds
Nicholas Kotov University of Michigan
Christopher Li Drexel University
MM4: Inorganic-Organic Composites
Session Chairs
Fiona Meldrum
Shu-Hong Yu
Wednesday AM, April 15, 2009
Room 3020 (Moscone West)
9:00 AM - **MM4.1
Polymer Controlled Crystallization and Morphogenesis of Biominerals.
Shu-Hong Yu 1
1 Division of Nanomaterials & Chemistry, Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui, China
Show AbstractMorphogenesis and biomimetic mineralization of inorganic minerals and inorganic-organic hybrid materials have attracted a lot of attention recently. By use of simple organic molecules, surfactant or low molecular weight polymers as additives, various forms of inorganic minerals and inorganic-organic hybrids can be synthesized by polymer controlled crystallization process. Recent progresses on the synergistic effects of the functionalities of a polymer, its controlled crystallization in a mixed solvent and its combination with either a hard interface or an air/solution interface, or a liquid/liquid interface, will be overviewed. The combination of a polymer additive with a suitable mineralization media or an interface (soft or hard) makes it possible to access various inorganic superstructures with complexity and specialty. The new findings in the area of polymer controlled crystallization provide new and exciting possibilities for rational design of various kinds of inorganic and inorganic-organic hybrid materials with ideal hierarchy and controllable length scale.
9:30 AM - MM4.2
Calcite Crystals with Composite Structures: Synthesis and Mechanical Properties
Yi-Yeoun Kim 1 , Luis Ribeiro 2 , Fabien Maillot 1 , Stephen Eichhorn 2 , Fiona Meldrum 1
1 Chemistry, University of Bristol, Bristol United Kingdom, 2 Materials, University of Manchester, Manchester United Kingdom
Show AbstractThe incorporation of polymer particles within calcite single crystals was investigated as a route to producing crystals with superior mechanical properties. Biominerals provide a unique inspiration for materials design, often exhibiting complex morphologies and possessing superior mechanical properties. While many of the biominerals with excellent mechanical properties are polycrystalline, biogenic single crystals, such as the calcite skeletal elements of sea urchins often fracture with difficulty and have strength-to-weight ratios exceeding those of many man-made construction materials. The fracture resistance of these biogenic single crystals is generally considered to derive from organic macromolecules occluded within the crystals, giving them a composite character.In the work described here, encapsulation of latex particles within calcite single crystals was investigated by precipitating calcium carbonate in the presence of latex particles with different sizes and surface chemistries. The effect of the crystal growth conditions, and the presence of soluble additives on the encapsulation of particles, was also studied. “Hard sphere”-type latexes were poorly incorporated, and were only embedded in the outer surfaces of crystals. In contrast, use of latexes with surface-confined polyelectrolyte chains resulted in a significant improvement in latex encapsulation, an effect attributed to stronger binding of these “hairy” particles to the crystal surfaces. To achieve encapsulation of a high density of latex particles, the possibility of changing the crystal growth mechanism was investigated. Rather than growing crystals via a traditional “ion-by-ion” route, calcite was precipitated in the presence of an additional additive which promotes crystallisation via “mesocrystal assembly”. On combination of these two methods – the use of “hairy” latexes, and the PSS additive, a remarkable level of latex incorporation was achieved such that a high density of particles were uniformly incorporated through the calcite single crystal.The mechanical properties of these composite crystals were investigated using nanoindentation techniques, and were compared with the properties of pure calcite crystals. Calcite crystals incorporating PS beads displayed a lower stiffness, modulus and hardness than pure calcite crystals, demonstrating that these composite particles exhibited mechanical properties between those of pure calcite and polystyrene. The composite crystals also displayed increased plastic behaviour and reduction in brittleness, probably due to a reduction in micro-crack formation in the calcite phase caused by the PS bead reinforcement. It can therefore be concluded that incorporation of polystyrene beads in calcite crystals introduces an energy dissipating mechanism which increases the toughness of the brittle crystal phase.
9:45 AM - MM4.3
The Investigation of Europium Fluoride and Barium Titanate Mesocrystals.
Christine Lausser 1 , Helmut Coelfen 1 , Markus Antonietti 1
1 Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, Potsdam-Golm , Brandenburg, Germany
Show AbstractThe design and synthesis of functional materials with hierarchically ordered structures plays a key role in materials science. In the past few years, many efforts have been devoted to the controlled fabrication of desired structures using different nanoscale building blocks. This has created new opportunities for the development of novel functional materials and their applications in catalysis, photonics and electronics. The strategy for self-assembly of complex nanostructures is generally based on coding the surface properties of the building blocks. This can be achieved, e.g., by using additives such as organic molecules, which can provide recognition of affinity interactions between different building units. An alternative way for self-organization is the application of external physical fields like an electric field to order anisotropic nanoparticle building units. Rare earth trifluorides are of particular interest to diverse applications in high-performance luminescent displays, optical communication, laser materials, catalyst and other functional materials because they are expected to have unique luminescence and magnetic properties. Here, we report on formation of Europiumtrifluoride mesocrystals by using a functional polymer additive. Mesocrystals are superstructures of mutually aligned nanoparticles. We show both, the formation mechanism of this complex nanostructure and the morphology and structure.A second investigated system is BaTiO3 mesocrystals. BaTiO3 has ferro- and piezoelectric properties and is used in electric industry for fabrication of multilayer capacitors, piezoelectric transducers, pyroelectric elements, and ferroelectric memories. Furthermore it could be useful for nonlinear optics, optical memories and electro-optic modulators.Based on the ferroelectric character of BaTiO3, an induced electric polarisation persists after removing an external electric field. BaTiO3 nanoparticles can be ordered by an external electric field as they get polarised and arrange to an ordered structure. The structure and formation mechanism of these mesocrystals is described.
10:00 AM - MM4.4
Tuning Mineralization in 3-D Gel Matrices: Porous Silicon Surfaces and Gradients
Lara Estroff 1 , Jason Dorvee 1 , Adele Boskey 3 , Nakwon Choi 2 , Abraham Stroock 2
1 Dept. Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 3 Biochemistry, Weill Medical College, New York, New York, United States, 2 Department of Chemical and Biological Engineering, Cornell University, Ithaca, New York, United States
Show AbstractThe bone-cartilage interface is a superb example of how Nature seamlessly integrates the properties of soft and hard materials in a hierarchical manner. We have been developing an in vitro model of the formation of the cartilage-bone tidemark by adapting a double-diffusion system (DDS) to create a controlled gradient of mineral density within a hydrogel matrix. In the DDS, calcium and phosphate solutions are introduced to opposite ends of a 6 cm tube of gel (gelatin or agarose). A band of carbonated apatite crystals appear on the third day of the experiment, close to the center of the tube. Our approach to controlling the band structure, composition, and position is three-pronged: 1) introduction of functionalized nano-porous silicon (pSi) membranes into the DDS to obtain control over the nucleation of carbonated apatite crystals; 2) introduction of enzymatically produced gradients of mineralization inhibitors; and 3) development of a computational model of the reaction-diffusion processes in the DDS. By using hydrosilyation of the pSi to introduce functionality (e.g., carboxylic acids, hydroxyls, phosphates) to the surfaces, we have demonstrated control over the size and morphology of the apatite nanocrystals grown on the surfaces. The DDS can also be used to study the effect of gradients of mineralization inhibitors and/or promoters on the position and structure of the mineralized band. To demonstrate this concept, we replaced the phosphate (Pi) reservoir with a pyrophosphate (PPi) reservoir and introduced polymer beads with covalently attached alkaline phosphatase, an enzyme capable of converting PPi to Pi. With no phosphatase beads, a band of calcium pyrophosphates (both di- and tetrahydrates were identified by XRD) forms off-center of the tube. The introduction of phosphatase beads into the system creates both a point sink for PPi, an inhibitor, and a point source for Pi. In experiments with these beads, asymmetric bands of carbonated apatite crystals form within the gel. The side of the band closest to the phosphatase beads is sharp, while the far side has a more gradual transition to mineral-free gel. We interpret this result to mean that the PPi, which is not hydrolyzed by the immobilized enzymes, acts as an inhibitor of apatite growth, creating the sharp interface closest to the beads. Finally, we will present results using a multi-scale Kinetic Monte Carlo model to study the high order crystallization process of nanocrystalline hydroxyapatite in the DDS. This technique can validate and predict experimental observations, including the addition of an inhibitor or promoter of mineralization. In conclusion, the DDS with pSi membranes provides insight into the role hydrogel matrices play in controlling biomineralization and provides synthetic approaches to organic-inorganic composites for biomedical applications.
10:15 AM - MM4.5
In Vitro Synthesis of Hybrid Materials Exhibiting a Bone-Like Architecture.
Nadine Nassif 1 , Frederic Gobeaux 1 2 , Emmanuel Belamie 1 , Patrick Davidson 2 , Gervaise Mosser 1 , Marie-Madeleine Giraud-Guille 1
1 , LCMCP-CNRS-UPMC, Paris France, 2 , LPS, u-psud 11-CNRS, Orsay France
Show AbstractCompact bone is a remarkable biological tissue which associates a dense collagen organic matrix and an apatite mineral network in close interaction. This natural composite exhibits a hierarchical order, from nanometers to centimeters and more, responsible for its high mechanical performances.Our approach results from the optimization of the procedures involved both in the preparation of the organic matrix and in the mineralization process. Appropriate conditions to reproduce the three dimensional organization of collagen in compact bone are based on the spontaneous self-assembly of protein at high concentrations into liquid crystalline phases (MM Giraud-Guille, G. Mosser, E. Belamie, Curr. Opin. Colloid Interface Sci. 2008, 13, 303–313). After a sol/gel transition, highly ordered collagen matrices are formed which turned out to be ideal templates for in vitro biomimetic mineralization. In parallel, an easy crystallization method for hydroxyapatite (HA) was proposed in order to induce mineral growth within collagen organic matrices. The method has the advantage of being performed at room temperature in a short time (4 days) without pH control and does not produce any secondary phases or by-products. Small-angle X-ray scattering and wide-angle X-ray diffraction were combined to study the organic matrix and mineral phase simultaneously. Additionally, electronic and optical microscopy techniques were performed to support the findings of synchrotron X-ray diffraction measurements. The presence of cross-striated fibrils proves that the collagen is not denatured during our mineralization process thus emphasizing the biomimetic aspect of our procedure. Moreover, the resulting hybrid material exhibits an important level of hierarchy observed in vivo, the aligned or twisted collagen organization, as well as the co-alignment between the HA crystals and the organic fibrils. Therefore, this material constitutes a unique example of a synthetic material that combines the composition, the structural orientation as well as the macroscopic architecture described in compact bone. This new biomimetic hybrid material therefore opens fascinating perspectives in bone tissue engineering.
10:30 AM - MM4.6
Rational Design of Protein-Based Bone Glues for Use in Mechanically Robust Hard-Tissue-Like Composites.
Eddie Wang 1 2 , Michael Chiang 3 , Seung-Wuk Lee 1 2
1 Bioengineering, University of California, Berkeley, Berkeley, California, United States, 2 Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Molecular Cell Biology, University of California, Berkeley, Berkeley, California, United States
Show AbstractThe design of synthetic bone grafts with mechanical properties suitable for use in load-bearing applications remains a challenge. In biomineralized systems such as bone, the mineral phase is tightly integrated with organic macromolecules. These macromolecules act as glues and dissipate energy, greatly increasing fracture toughness. To mimic natural systems we have rationally designed novel biopolymers consisting of elastin-like polypeptides (ELPs), for mechanical strength, genetically fused with hydroxyapatite binding peptides (HBPs), for mineral binding. We are integrating these proteins into composite materials with calcium phosphate minerals and investigating the effects of charge and physical/chemical crosslinking on material properties. The use of rationally designed molecular glues creates composite materials with superior, tunable mechanical properties which may be useful for various hard tissue engineering materials.
10:45 AM - MM4.7
Scalable Shear-Driven Nanospinning of Wet-Processable Polymer and Hybrid Composite Fibers.
Stoyan Smoukov 1 , Eunkyoung Shim 2 , Benham Pourdeyhimi 2 , Manuel Marquez 3 , Orlin Velev 1
1 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 College of Textiles, North Carolina State University, Raleigh, North Carolina, United States, 3 Harrington Dept. of Bioengineering, Arizona State University, Tempe, Arizona, United States
Show AbstractMany industrially important fibers are only produced by wet-spinning. The process involves extrusion through nozzles, and commercial fibers are limited to diameters above approximately 10 microns. Efficient methods for nanofiber formation would allow new applications for fine filters, make better wound dressings, barrier materials, and tissue scaffolds. Here, we report a new nanospinning method where fibers are formed by shear extension and anti-solvent based precipitation in bulk solution. The method has a number of advantages compared to the existing methods of fiber formation. Most importantly, instead of using nozzles, the method relies on combined capillary instabilities and shear extension to form the fibers. This is especially desirable for the incorporation of various particle additives in composite fibers, which is problematic for traditional wet-spinning due to clogging of the nozzles. The fibers have diameters of 200-500 nm, comparable to many electrospun fibers, yet produced in bulk. The fiber production scales up proportionately with the volume of the production device, and could be made into a continuous process. Nanospun fibers of various polymers and composites with potential applications in next-generation non-woven textiles are demonstrated.
11:30 AM - **MM4.8
Materials Chemistry Meets Genome Biology: Molecular Principles of Bio-enabled Mineral Formation.
Nils Kroger 1
1 School of Chemistry and Biochemistry & School of Materials Science and Engineering, Georgia Tech, Atlanta, Georgia, United States
Show AbstractDiatoms are a large group of single-celled microalgae that produce cell walls made of amorphous silica. The silica cell walls are three-dimensional hierarchical microstructures displaying species specific, porous patterns with pore sizes in the nano-to micrometer range. Elucidating the molecular principles of diatom silica biomineralization has the potential to serve as a guideline for the development of novel, environmentally benign approaches for materials synthesis. Indeed, emerging insight into the biochemical mechanism of silica biomineralization in diatoms has recently led to the development of recombinant polypeptides for in vitro syntheses of silica and titania materials under mild reaction conditions. Systematic analyses using bacteriophage display methods revealed high positive charge density and the presence of multiple hydroxy-amino acids as a common feature in silica and titania forming (poly-)peptides. This insight has spurred the development of an in silico method for screening entire diatom genome databases to identify novel proteins involved in diatom silica biomineralization.
12:00 PM - MM4.9
Peptide-Polymer Conjugates that Mimic Functions of Silicateines to Control the Formation of Composite Fibers.
Hans Boerner 1 , Stefanie Kessel 1
1 Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, Potsdam Germany
Show AbstractHere we present our recent investigation on a bioinspired silicification process to rapidly produce silica composite fibers that exhibit six levels of hierarchical order.Precisely controlled composite fibers, combining polymers and inorganic components at nanoscopic length scales, have been recognized as promising building blocks for tissue engineering, bioceramics or designed material reinforcement. Particularly, the anisotropic dimensions and the directional properties of composite fibers make them highly interesting as building blocks for bottom-up strategies. Biological composite materials indeed demonstrate the potentials arising from controlled interactions of organic and inorganic compounds.[1] A breathtaking structural and functional diversity exists in nature, including materials such as the exoskeletons of diatoms and cage structures of marine glass sponges.To mimic biomaterials based on silica composites a bioinspired silicification process was established to control silica condensation and access well-defined silica composite fibers. For that, self-assembled poly(ethylene oxide)-peptide nanotapes,[2] have been utilized, possessing anisotropic functionalities to mimic silica morphogenesis proteins from glass sponges (silicateines) to direct the silicification process.[3] In analogy to biosilicification, silicic acid is provided directly as the silica precursor. A rapid enrichment of the precursor on the functional nanotapes controls the “silicic acid”, preventing uncontrolled 3D condensation and directing the formation of the silica network. Thus, very low concentrations of silicic acid and short contact times are sufficient to form well-defined silica composite nanotapes (proto composite tapes).[4] These proto structures could be isolated successfully. However, at higher concentrations, the proto composite tapes self-assemble spontaneously, resulting in the construction of macroscopic composite fibers with about a millimeter in width and up to centimeters in length. These macroscopic composite fibers possess a complex inner structure with six distinguishable levels of hierarchical order.The co-assembly route was further extended toward an automated plotting process. This utilizes a solution of the PEO-peptide nanotapes as ink to draw macroscopic nanostructured composite fibers, where the orientation of the nanostructure elements correlates to the macroscopic drawing direction.[4][1] Weiner, S.; Addadi, L.; Wagner, H. D. Mater. Sci. Eng., C 2000, 11, 1.[2] Eckhardt, D.; Groenewolt, M.; Krause, E.; Börner, H. G. Chem. Commun. 2005, 2814.[3] Kessel, S.; Thomas, A.; Börner, H. G. Angew. Chem. Int. Ed. 2007, 46, 9023.[4] Kessel, S.; Börner, H. G. Macromol. Rapid. Commun. 2008, 29, 419.
12:15 PM - MM4.10
Development of an Icosahedral Virus-like Particle Platform for Peptide Display and Investigation of Biomimetic Silica Condensation Kinetics.
Carlee Ashley 1 , David Peabody 2 , 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 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractDiatoms possess intricate nanostructured siliceous cell walls whose synthesis is directed by silaffins and long-chain polyamines, both of which catalyze the condensation of silica from silicic acid under neutral conditions. We seek to create nanomaterials that emulate the properties of diatom frustules and to investigate the kinetics of biosilicification by displaying catalytic peptides on the surfaces of bacteriophages and subsequently self-assembling them into 2D structures. Bacteriophages possess several properties that enable their self-assembly into highly-ordered 2D structures via evaporation-driven processes. Phages are highly monodisperse, possess symmetrical geometries, and occur in sizes from tens to hundreds of nanometers. Furthermore, the protein capsids of bacteriophages can be genetically modified to express peptides with specific or random amino acid sequences. We have used two 28-nm icosahedral bacteriophages of Escherichia coli, MS2 and Qβ, in conjunction with a novel deposition technique, convective assembly, to create hexagonal-close packed (HCP) structures that retain their long-range order upon desiccation. We have monitored the dynamics of 2D film formation using Grazing-Incidence Small-Angle X-ray Scattering (GISAXS) at a synchrotron source. Furthermore, we have developed a platform for specific and random peptide display using the virus-like particle (VLP) of MS2. The MS2 capsid is highly tolerant of peptide insertions, enabling peptides to be displayed in high density and in specific locations on the VLP surface. We have produced MS2 VLPs that display 90 copies of the R5 peptide, which is found in the silaffin-1 protein of the diatom, Cylindrotheca fusiformis, and have quantified the degree of silica condensation in the presence of this VLP using the molybdate colorimetric assay. We have also used phage display to identify peptides with an affinity for silica particles synthesized in the presence of the R5 peptide and have confirmed that basic amino acids are prevalent in the peptides that catalyze neutral pH biosilicification. We have, to this end, displayed poly-L-lysine, poly-L-arginine, and poly-L-histidine of various lengths on the surfaces of MS2 VLPs to study condensation rates at various concentrations of pre-hydrolyzed tetramethyl orthosilicate (TMOS). We have, furthermore, investigated the rate of silica condensation in the presence of free R5 peptide, poly-L-lysine, poly-L-arginine, poly-L-histidine, and four peptides identified to have an affinity for silica via phage display. We are currently attempting to control the rate of silica condensation in the presence of VLPs that display catalytic peptides in order to selectively synthesize a thin layer of silica on the surfaces of well-ordered VLP arrays. Understanding the kinetics of biosilicification is crucial to creating silica-based nanomaterials in a biocompatible, biomimetic fashion.
12:30 PM - MM4.11
Hierarchically Structured Macroscopic Structures of Gelatin and Strontium Phosphates.
Henrik Birkedal 1 , Bjorn Mikladal 1
1 Department of Chemistry & Interdisciplinary Nanoscince Center, Aarhus University, Aarhus Denmark
Show AbstractNature presents a wealth of examples of complex hierarchical structures that integrate nano-components into 3D functional materials. In the present contribution we present a bioinspired approach to the creation of hierarchical three dimensional structures.At the interface between a Sr-loaded gelatin gel and a sodium phosphate solution spectacular cm-long hierarchical structures are found to grow into the solution. The structures have a width of a couple hundred microns and a wall thickness of about 10 microns. The walls display a distinct structure with an outer layer of ball shaped 500 nm large assemblies of nanocrystals followed by a broader layer of needle shaped crystals and finalizing by a smoother layer upon which macroscopic crystals are attached. The ball layer is found to be sodium rich Sr-apatite, while the needles are Sr-apatite, which towards the other side of the wall become interlaced with another phase: nastrophite, which is a hydrated sodium strontium phosphate. The route to these spectacular structures will be discussed together with in depth characterization of the structures.
12:45 PM - MM4.12
Silica Coated Peptide Fibrils as Biomaterials with Tunable Shear Modulus
Aysegul Altunbas 1 , Joel Schneider 2 , Darrin Pochan 1
1 Materials Science & Engineering, University of Delaware, Newark, Delaware, United States, 2 Department of Chemistry & Biochemistry, University of Delaware, Newark, Delaware, United States
Show AbstractIn this study, a bio-inspired route was used for the fabrication of a 3D scaffold that displays hierarchical organization of an inorganic layer around an organic self-assembled peptide fibril template. The 20 amino acid peptide used in this study, MAX8, consisted of alternating hydrophilic (lysine) and hydrophobic (valine) residues flanking a four amino acid turn sequence in the center (VKVKVKVKVDPLPTKVEVKVKV-NH2). After intramolecular folding into a beta-hairpin conformation on addition of a desired solution stimulus, this peptide intermolecularly self-assembles into a three dimensional network of entangled fibrils rich in beta-sheet with a high density of lysine groups exposed on the fibril-surfaces. Polyamines are known to catalyze the polycondensation of silicic acid in water and the lysine-rich surface chemistry was utilized to create a silica shell around the fibrils. The mineralization process of the fibrils was initiated under physiological conditions by adding the silica precursor, tetramethyl orthosilicate, to the pre-assembled hydrogel, which results in a rigid, porous silica network that retains the microscale and nanoscale structure of the peptide fibril network. Structural characterization via Transmission Electron Microscopy, cryogenic-Scanning Electron Microscopy and Small Angle Neutron Scattering, mechanical characterization via oscillatory rheology, and in vitro biological properties of the silicified hydrogels will be presented.
MM5: Directed Assembly of Organic/Inorganic Hybrid
Session Chairs
Nicholas Kotov
Christopher Li
Wednesday PM, April 15, 2009
Room 3020 (Moscone West)
2:30 PM - **MM5.1
Formation of Hierarchical Architectures through Self-Directed Crystal Growth in Organic-Inorganic Combined Systems
Hiroaki Imai 1
1 Department of Applied Chemistry, Keio University, Yokohama Japan
Show AbstractMultiscale hierarchical architectures of biominerals are emerging from a combination of inorganic crystals and organic macromolecules. However, mimicking the elaborate control on biomineralization by using conventional technologies is commonly difficult. Here, strategies for the production of biomimetic hierarchical architectures in aqueous solutions are shown. Various characteristic morphologies consisting of regularly assembled nanometric inorganic units were achieved through crystal growth directed with specific organic species under diffusion mass transfer conditions in organic gel matrix. Hierarchically laminated calcium phosphate was formed in a gel matrix of poly(acrylic acid) containing phosphate anions by diffusion of calcium cations. A hierarchical architecture of calcite similar to the microstructure of egg shells was obtained in an agar gel matrix containing calcium ions by diffusion of carbon dioxide. Rectangle films, acute spines and hollow cones of calcium carbonate consisting of iso-oriented nanoscale crystal grains, which were similar to particular microstructures of biominerals, were produced in a solution containing specific soluble organic polymers, such as poly(acrylic acid). A nacre-mimetic layered architecture was also achieved from potassium sulfate with poly(acrylic acid). The formation of the iso-oriented nanocrystals in the hierarchical architectures was ascribed to crystal growth directed with the incorporation of specific organic molecules. The morphogenesis could be associated with the construction of the macroscopic structures through stepwise growth of the oriented nanometric units under diffusion-limited conditions. The resultant composite materials had organic domains in nanoscopic scale and performed as a new type of hosts for incorporation of organic molecules.
3:00 PM - MM5.2
Multidomain Peptides as Biocompatible Single-Walled Carbon Nanotube Surfactants.
Erica Bakota 1 , Jeffrey Hartgerink 1
1 Chemistry, Rice University, Houston, Texas, United States
Show AbstractIn recent years, the interaction of single-walled carbon nanotubes (SWCNTs) with biological systems has been heavily researched. SWCNTs have unique optical and electrical properties that make them promising materials for biosensors and cell scaffolds. However, solubilization of SWCNTs in a biologically compatible surfactant has historically been a problem. Conventional surfactants, such as sodium dodecyl sulfate (SDS), have been shown to be extremely cytotoxic to cells. Covalent sidewall modification of the SWCNT as a means of solubilization (while potentially less cytotoxic) results in destruction of the electronic structure of the tube. Finally, traditionally “biocompatible” surfactants such as the Pluronic series only allow poor fluorescence of SWCNTs. Thus new biocompatible surfactants are needed. A class of peptides, called multidomain peptides, has been shown to noncovalently solubilize SWCNTs. These peptides assemble to form β-sheet fibers, which can effectively wrap SWCNTs without disturbing the nanotube electronic structure. In this work, the cytotoxicity of selected multidomain peptides has been studied using NIH 3T3 mouse fibroblasts. These studies were run in parallel with a known cytotoxic control, SDBS, and two non-cytotoxic controls, Pluronic F68 and Pluronic F127. Statistical analyses reveal that the toxicity of the multidomain peptides is not significantly different from the Pluronic series, making multidomain peptides promising alternatives for delivering SWCNTs in vitro. In addition, the cytotoxic effects of the SWCNTs themselves were also explored. It was determined that SWCNTs do not display any significant toxicity, regardless of the surfactant in which they are suspended.
3:15 PM - MM5.3
Formation of Hg Nano-particles via Metal Attachment to Plasmid DNA.
Shikha Varma 1 , Subrata Majumder 1 , G. Chainy 2
1 , Institute of Physics, Bhubaneswar India, 2 , Utkal University, Bhubaneswar India
Show AbstractTransition metal pollution poses a serious threat to the environment and the health of living beings. Hg is one such element that in addition to being a challenging pollutant is extremely toxic. Mercury, due to its high oxidation proximity, can cause carcinogenic, mutagenic and teratogenic effects in the cells of the living organism causing modification in the cell-DNA. The electronic structure of DNA can get severely altered due to the hybridization of molecular orbitals of DNA with metallic states. The understanding of the electronic structure of DNA, prior to and after metal attachment, thus can delineate the effect of Hg conjugation to DNA. We have utilized the technique of X-ray Photoelectron Spectroscopy (XPS) to investigate the electronic structure of a circular plasmid DNA, both prior to and after its reaction with a Hg salt. XPS measurements have been performed in a UHV chamber equipped with a hemispherical analyzer and a dual Mg-Al X-ray anode. The core level spectra for DNA, primarily exhibiting the presence of Phosphorus (P), Nitrogen (N), Carbon and Oxygen (O), get severely modified after their interaction with Mercury. The electronic structure studies and the binding energy shifts of core levels from plasmid, prior to and after metal attachment, suggest that the Hg metal has a high affinity of attachment to the nitrogenous bases of the plasmid DNA. This is in contrast to the Mg2+ binding which conjugates to the phosphate backbone of the DNA. The interaction of Hg metal with plasmid DNA has also been investigated with Scanning Probe Microscope (SPM). The SPM studies, performed using Nanoscope IIIa, indicate the cleavage of circular double-stranded plasmid on its interaction with metal Hg and formation of linear chains. Agarose gel electrophoresis also supports these results. The high resolution SPM images, surprisingly, also show the presence of Hg-nanoparticles attached to the linear DNA. In some regions Hg-Nanowires are also observed. Core level shifts also support the presence of Nano-Hg-particles. The studies reveal that the present technique of Hg attachment to the nitrogen bases of the plasmid DNA can be utilized to produce Hg nanoparticles (and Hg-nano-wires) with 4-5nm diameter.
3:30 PM - MM5.4
Bio-templated Fabrication of Gold Nanowires for Device Application.
Youjin Lee 1 , Angela Belcher 1
1 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractOne-dimensional gold nanowires with well-defined structures have been pursued due to their intrinsic characteristics. The reliability of gold materials both chemically and electrically enables them to be good candidates for nanoelectronic device applications such as bio-sensors, photonics, and waveguides. In our laboratory, we have used filamentous M13 phage as a biological template for the growth and nucleation of various metal and metal oxide nanowires. Previously, we have identified and displayed a gold binding peptide on the M13 virus for one-dimensional structure with gold nanoparticle attachment. However, it is desirable to further control nanowire fabrication. Towards this end, we have achieved a novel, controlled synthesis for 1-D nanowires. Incubation of gold ions with surfactant capped M13 in an aqueous system results in well-defined one-dimensional gold nanowires. The whole process was done under aqueous conditions at room temperature using environmentally friendly materials. The mechanism of formation of gold nanowires, properties, and possible application will also be discussed.
3:45 PM - MM5.5
Amphiphilic Molecules-Conjugated Nanomaterials
Peng He 1 , Xinyuan Zhu 2
1 Chemistry, North Carolina State University, Raleigh, North Carolina, United States, 2 School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai China
Show AbstractWe summarized our recent progress on the study of amphiphilic molecules-conjugated nanomaterials and their interfacial self-assembly. Phospholipids as biological amphiphilic molecules and hyperbranched poly(amidoamine) as synthetic amphiphilic polymers are the two representative targets with distinctive functions and properties for investigations. In the first research part of biological amphiphilic molecules, phospholipids with different functional groups were chemically modified on the surface of different types of nanomaterials, including metallic nanoparticles (NPs), carbon nanotubes (CNTs), and quantum dots (QDs). Although nanomaterials such as CNTs were swathed in numerous synthetic and natural molecules, sheathing them in a uniform layer of bioactive phospholipid molecules has successfully achieved excellent dispersibility both in aqueous and non-aqueous systems due to the amphiphilic property of phospholipids. Photoluminescence enhancement of QDs and size-controlled growth of NPs after phospholipid functionalizations were also reported. In the second research part of synthetic amphiphilic polymers, a general strategy for synthesizing amphiphilic core-shell hyperbranched poly(amidoamine) and realizing the interfacial self-assembly of QDs conjugated with polymers has been employed. Aqueous QDs were firstly transferred into chloroform phase in the presence of palmityl choloride functionalized hyperbranched poly(amidoamine) and then self-assembled at the water/chloroform interface by decreasing the pH value of aqueous phase or introducing α-CDs to the aqueous phase. All these findings will serve as a future platfom for new devices ranging from biosensors to nano-detectors.
4:15 PM - **MM5.6
Bio-enabled Assembly of Hybrid Nanomaterials.
Rajesh Naik 1
1 Materials and Manufacturing, Air Force Research Laboratory, Wright Patterson AFB, Ohio, United States
Show AbstractBiomolecular building blocks are used in the synthesis of nanomaterials and assembly of hybrid structures by exploiting the recognition properties of biomolecules. In nature, the programmed assembly of amino acid within a polypeptide or the nucleotide sequence within nucleic acids gives rise to biomolecules that direct specific interactions. The interactions between the biomolecules such as in coiled-coil proteins, nucleic acids and antigen-antibody can be used in creating hybrid structures. Similarly, using molecular engineering can be to create multifunctional biotemplates to assemble and/or synthesize hybrid materials. As the library of biomolecular templates that interact with various materials begins to become populated, and in combination with computational modeling experiments, a much clearer understanding of mechanism of biotic-abiotic interactions will begin to emerge. Thus, one should be able to create hybrid materials using rational design by dialing-in the different bio-domains that could direct the synthesis and assembly of hybrid materials for a desired application. In my talk, I will describe approaches to achieving hybrid structures using biomolecular templates, and the properties associated with these hybrid structures.
4:45 PM - MM5.7
Nano Shish Kebabs and Beyond, Hierarchical Structure Enabled by One Dimensional Nucleation.
Bing Li 1 , Bingbing Wang 1 , Rebecca Chen 1 , Christopher Li 1
1 Materials Sci. & Eng., Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractWe report herein the hierarchical structure and morphologies enabled by one dimensional crystallization. Using both controlled solution crystallization and physical vapor deposition methods, carbon nanotubes (CNTs) were periodically decorated with polymer lamellar crystals, resulting in nano hybrid shish-kebab (NHSK) structures. The periodicity, which can be readily controlled by tuning the crystallization condition, varies from 20 - 150 nm. The kebabs are approximately 5-10 nm thick (along CNT direction) with a lateral size of ~ 20 nm to micrometers. The detailed mechanism of forming this periodic structure on CNTs will be discussed. Because the polymer kebabs can be easily removed, these unique NHSKs can serve as templates to fabricate a variety of CNTs-containing hybrid materials with controlled pattering on the CNT surface. Sub-10 nanometer alternating patterning was achieved by using crystalline block-copolymers. In addition to CNTs, electro-spun nanofibers were also used to form hierarchically ordered polymer nanofiber structures, named as nano fiber shish kebabs (NFSKs). Pre-formed poly(ethylene oxide) (PEO) nanofibers served as the shish and a secondary polymer was decorated on the nanofiber in the form of single crystal lamellae by either an incubation (slow crystallization), or a solvent evaporation (fast crystallization) method. The structural parameters of the NSFK such as the fiber diameter, periods, the kebab size etc., were readily controlled by changing the electrospinning and crystallization conditions. This hierarchical architecture is of great technological interest because it provides a platform for incorporating different functionalities into nanoscale polymer fibers in an ordered fashion. As a proof-of-concept, gold nanoparticles (AuNPs) were immobilized on the PEO nanofiber by using HS-terminated PEO as the secondary polymer. Regular line arrays of AuNPs were periodically immobilized onto the nanofiber, and the AuNP lines were perpendicular to the nanofiber. The detailed formation mechanism will be discussed.
5:00 PM - MM5.8
Magnetic-Metallic hybrid Nanoparticles for Cellular Targeting and Microwave Thermotherapy of Prostate Cancer.
Dickson Kirui 1 , Diego Rey 1 , Cameron Bardliving 1 , Carl Batt 2
1 Biomedical Engineering, Cornell University, Ithaca, New York, United States, 2 Food Science, Cornell University, Ithaca, New York, United States
Show AbstractMagnetic-Mmetallic hybrid microwave-active nanoparticles are being developed as therapeutic agents which can be directed to cancer cells and carry out localized thermotherapy of prostate cancer. Controlled thermal decomposition of precursor metal was used to synthesize magnetic-metallic hybrid nanoparticles such as Au-Fe3O4 creating various shapes (peanut-like and dumbbell-like) particles. The magnetic particles were characterized by TEM, HRTEM, SEM, FT-IR, and Zeta sizer to determine particle morphology and size. Magnetic properties of these particles were measured using vibrating sample magnometer (VSM). These nanoparticles have the following characteristics: (a) particle size of 15-20 nm which will lead to enhanced permeability and retention( EPR) effect (b) composed of peanut-shaped Au and Fe portion that will allow dual functionalization (c) highly superparamagnetic ~ 80 emu/mg (VSM) which will enhance microwave capabilities.To render the particles water soluble and also allow further functionalization, PEGylated phospholipid (Avanti polar lipids) was used to encapsulate the as-synthesized hydrophobic nanoparticles forming micellar particle composites. Hydrophobic quantum dots (CdSe/ZnS) were additionally encapsulated in the micelles allowing them to be localized by fluorescence microscopy. Next, we generated nanoparticle- antibody conjugates with J591 antibody that binds to the prostate-specific membrane antigen (PSMA), a well-known prostate cancer tumor maker that is expressed on prostate acinar epithelial cells. We demonstrated that these bioconjugates can efficiently target and taken up by the prostate LNCaP epithelial cells, which express PSMA. We further investigated the susceptibility of the particles to focused microwave thermotherapy inside the cadaver bull prostate using a clinical Transurethral Microwave Thermotherapy (TUMT) device. Intraprostatic temperature profile during microwave treatment of the bull prostate was monitored with several fiber optic probes. The tissue injected with nanoparticles showed a 10 oC temperature increase (n = 4 prostates) over a 20-min treatment period as compared to the tissue not injected with nanoparticles.
5:15 PM - MM5.9
DNA Templated Fabrication of Metal and Ceramic Nanostructures
Satoshi Ohara 1 2 , Yoshiharu Hatakeyama 2 , Mitsuo Umetsu 2 , Jinghua Han 1 3 , Kazuyoshi Sato 1 , Tadafumi Adschiri 2
1 , Osaka University, Ibaraki Japan, 2 , Tohoku University, Sendai Japan, 3 , Tianjin University, Tianjin China
Show AbstractDeoxyribonucleic acid (DNA) is one of the polymer templates most appropriate to build up defined inorganic materials. In this study, we describe the formation of palladium (Pd)-DNA nano hybrid structures such as nanoparticle, nanonecklace and nanoring by the combination of metallization and DNA compaction, and apply the uniquely-assembled hybrid materials for chemiresistive hydrogen sensors with volume expansion-type response. This paper also reported arrangement of ceramic nanoparticles by DNA template.
5:30 PM - MM5.10
Hybrid Nanomaterials: Nanoparticle Arrays via Self Assembled Peptide Structures
Nikhil Sharma 1 2 , Darrin Pochan 1 2
1 Materials Science & Engineering, University of Delaware, Newark, Delaware, United States, 2 , Delaware Biotechnology Institute, Newark, Delaware, United States
Show AbstractThe bottom up approach towards nano-scale patterning presents the possibility of creating hierarchical architectures through simple self-assembly strategies. Herein, we demonstrate the use of peptidic templates for the construction of linear arrays of inorganic nanoparticles. A 20 amino acid peptide, consisting of alternating hydrophilic (lysine) and hydrophobic (valine) residues flanking a central diproline turn sequence, was employed to create laterally spaced (2D) nanoparticle arrays of gold. This peptide self assembles into laminated morphology in solution and has a periodic nanostructure consisting of alternating hydrophobic and hydrophilic layers with a lateral periodicity of 2.5 nm. Negatively charged gold nanoparticles are templated into the positively charged lysine layer through electrostatic interaction and are aligned within the template that itself swells to a periodic spacing of 4.0 nm in order to accommodate the particles. A long chain alanine-rich polypeptide was used to create one-dimensional nanoparticle assemblies. This peptide assembles into fibrils with monodisperse widths and presents its charged functional groups periodically along the length of the fibril. These functional groups bind nanoparticles and results in their spatially modulated linear arrangement. Nanoparticle arrays have potential applications in nano-electronics and photonics, and we are currently attempting to create arrays of quantum dots and hetero-structures of metal and semiconductor particles.
5:45 PM - MM5.11
Dynamic Hybrid Materials for Constitutional Self-instructed Membranes.
Mihail Barboiu 1
1 , Institut Europeen des Membranes, Montpellier France
Show AbstractMany fundamental biological processes appear to depend on unique properties of inner hydrophylic domains of the membrane proteins. Gramicidin A, KCsA-K+, Aquaporin are well known non-exclusive examples, of protein-channels in which ions or water molecules diffuse along the directional pathways. Recently, we proved the possibility to create directional hydrophilic pathways and urea ribbons are used to oriented the transporting superstructures in the fixed-site hybrid materials by a sol-gel process. Herein, a synthetic membrane system has been set up within the pores of an oriented mesoporous solid support, and evidence is presented that the membrane adapts and evolves its internal structure so as to improve its ion transport properties. From the conceptual point of view, a columnar silica nanospace can be used as a scaffolding matrix to oriented functional self-organized macrocycles non-covalently incorporated through hydrophobic interactions. Under these conditions such hybrid materials, reminiscent with the bilayer membrane structure, must be rendered constitutionally dynamic. Because of the ability to undergo continuous change in constitution of their organic functional network in response of external stimuli or environmental factors, these membranes express an adaptive behaviour: the addition of the fittest cation drives the evolution of the membrane toward the formation of a specific channel superstructure, selective for the cation that promoted its generation in the first place. This is nice example of dynamic membranes where a solute prepares itself its own selective membrane. More generally, applying such consideration to hybrid materials, leads to the definition of dynamic hybrid materials, which might provide new insights into the basic features that control the design of artificial ion-channels.1. Barboiu, M. & Lehn, J.-M. Proc. Natl. Acad. Sci. U.S.A. 99, 5201-5206 (2002).2. Cazacu, A. et al. J. Am. Chem. Soc. 128, 9541-9548 (2006).3. Barboiu, M., Vaughan, G. & van der Lee, A. Org. Lett. 5, 3073-3076 (2003).4. Barboiu M. et al. J. Membrane Sci. 161, 193-206 (1999).5. Barboiu M et al. J. Membrane Sci. 172 91-103 (2000).6. Barboiu, M., et al J. Am. Chem. Soc. 126, 3545-3550 (2004). 7. Arnal-Herault, C. et al. Angew. Chem. Int. Ed. 46, 4268-4272 (2007). 8. M. Michau et al. Hybrid Membranes. Chem. Eur.J., 14, 1776-1783 (2008).
Symposium Organizers
Shu Yang University of Pennsylvania
Fiona Meldrum University of Leeds
Nicholas Kotov University of Michigan
Christopher Li Drexel University
MM6/NN7: Joint Session: Intelligent Polymers in Biological Systems
Session Chairs
Andreas Lendlein
Christopher Li
Rein Ulijn
Thursday AM, April 16, 2009
Room 3018 (Moscone West)
9:00 AM - **MM6.1/NN7.1
Responsive Hydrogels and Hybrid Nanostructures through beta-Hairpin Self-assembly
Darrin Pochan 1 , Joel Schneider 2
1 Materials Science and Eng, University of Delaware, Newark, Delaware, United States, 2 Chemistry and Biochemistry, University of Delaware, Newark, Delaware, United States
Show AbstractSelf-assembly of molecules is an attractive materials construction strategy due to its simplicity in application. By considering peptidic or charged synthetic polymer molecules in the bottom-up materials self-assembly design process, one can take advantage of inherently biomolecular attributes; intramolecular folding events, secondary structure, and electrostatic interactions; in addition to more traditional self-assembling molecular attributes such as amphiphilicty, to define hierarchical material structure and consequent properties. The local nano- and overall network structure, and resultant viscoelastic and cell-level biological properties, of hydrogels that are formed via beta-hairpin self-assembly will be presented. These peptide hydrogels are potentially excellent scaffolds for tissue repair and regeneration due to inherent cytocompatibility, porous morphology, and shear-thinning but instant recovery viscoelastic properties. The 20 amino acid parent peptide MAX1 (H2N-VKVKVKVKVDPPTKVKVKVKV-CONH2), has been shown to fold and self-assemble into a rigid hydrogel based on environmental cues such as pH, salt, and temperature including physiological conditions. The hydrogel is composed of a network of fibrils that are 3 nm wide and heavily branched and entangled with no covalent crosslinking required for gel stiffness. In addition, slight design variations of the MAX1 sequence allow for tunability of the self-assembly/hydrogelation kinetics as well as the tunability of the local peptide nanostructure and hierarchical network structure.. In turn, by controlling hydrogel self-assembly kinetics, one dictates the ultimate stiffness of the resultant network and the kinetics through which gelation occurs. Importantly, once formed into a solid, self-supporting gel the network can be disrupted by the introduction of a shear stress. The system can shear thin but immediately reheal to preshear stiffness on the cessation of the shear stress. This shear thinning behavior of these physical networks makes them interesting candidates for injectable delivery in vivo where no post injection chemistry is required to set up the network. Peptide structure for folding and self-assembly, self-assembly characterization, gel material properties, and cell-level biological properties of these peptide hydrogels will be discussed.
9:30 AM - **MM6.2/NN7.2
Self-organized Biopolymer Gels without Crosslinkers.
Gerard Wong 1
1 Materials Science and Engineering, Dept. of Physics and Dept of Bioengineering, University of Illinois, Urbana, Illinois, United States
Show AbstractInteractions between flexible chains and rigid rods govern a broad range of systems, from liquid crystalline polymers to biological tissues. It is well known that the Flory theory predicts coexistence between isotropic and anisotropic phases in such ‘rod-coil’ systems consisting of polymers of dissimilar flexibility. We find that the existence of strong electrostatic interactions can drastically modify this baseline behavior, and lead to unexpected modes of self organization. We study the phase behavior in semi-dilute mixtures of strongly-charged actin rods and DNA chains using confocal microscopy and synchrotron x-ray diffraction. Instead of macroscopic phase separation, we find an entangled percolating network of elongated nematic F-actin domains threading through a mesh of random DNA coils. The more highly-charged DNA coils compress F-actin rods and induce nematic order at concentrations well below the Onsager criterion. The inter-actin molecular spacing in these nematic domains exhibits a power law dependence on DNA concentration, consistent with counterion-dominated osmotic pressure. With added salt, the system undergoes a transition from a ‘strongly-charged’ regime dominated by counterion controlled osmotic pressure to a ‘weakly-charged’ regime dominated by conventional depletion effects. The entire phenomenon is entropic in origin. Interestingly, these nematic domains are reticulated into a network without forming bulk defects, by restructuring perpendicular crossings into locally tangent crossings, suggesting that mixtures of biopolymers with different flexibilites may lead to unexpected mechanical properties.
10:15 AM - MM6.4/NN7.4
Core/Shell Nanocapsules Self-Assembled from Amphiphiles for Efficient Delivery of Anticancer Drugs
Yi-Yan Yang 1 , Jeremy P.K. Tan 1 , Fredrik Nederberg 2 3 , Shrinivas Venkataraman 1 , Sung Ho Kim 2 , Kazuki Fukushima 2 , James L. Hedrick 2
1 , Institute of Bioengineering and Nanotechnology, Singapore Singapore, 2 , IBM Research, San Jose, California, United States, 3 , Stanford University, Stanford, California, United States
Show AbstractMicellar nanoparticles self-assembled from amphiphilic polymers, which have a hydrophobic core and a hydrophilic shell, have received increasing attention in the field of anticancer drug delivery as the core allows for the incorporation of hydrophobic drugs and the shell protects the enclosed drugs from enzymatic degradation and provides prolonged blood circulation. However, there are several challenges associated with the existing micellar nanoparticles, including low drug loading capacity and wide size distribution, which may lead to ineffective drug delivery and undesirable biodistribution of the drug. In order to overcome these issues, we have synthesized ABC mikto-arm terpolymers poly(ethylene glycol) (5k)-poly(D-lactide) (2k)-poly(D-lactide) (2k) (PEG-PDLA-PDLA) and poly(ethylene glycol) (5k)-poly(L-lactide) (2k)-poly(L-lactide) (2k) (PEG-PLLA-PLLA), or the miktoarm poly(ethylene glycol) (5k)-poly(D-lactide) (2k)-poly(L-lactide) (2k) (PEG-PDLA-PLLA) with well-controlled molecular weight via organocatalytic ring-opening polymerization. After being loaded with paclitaxel (a hydrophobic anticancer drug), stereocomplexes of PEG-PDLA-PDLA and PEG-PLLA-PLLA or PEG-PDLA-PLLA formed micellar nanoparticles with smaller size and more narrow size distribution as well as higher drug loading level when compared to those prepared from conventional stereo regular linear or Y-shaped amphiphiles. Interestingly, the interactions between paclitaxel molecules and the stereocomplexes led to the formation of a nanocapsule structure. Therefore, near zero-ordered release kinetics of paclitaxel was achieved without significant initial burst. In addition, being inspired from amphiphilic peptide structure, we have synthesized core/shell nanocapsules from a small molecular amphiphile, which are being used to incorporate hydrophilic anticancer agents such as doxorubicin, proteins and genes. These nanocapsules provide great potential as a unique carrier for efficient delivery of anticancer drugs.
10:30 AM - MM6.5/NN7.5
Force Generation of Expanding Actin Gels
Schmidt Stephan 1 , Georg Freund 1 , Emmanuele Helfer 2 , Walter Zimmermann 1 , Andreas Fery 1
1 Physicak Chemistry II, Universität Bayreuth, Bayreuth Germany, 2 LEBS, CNRS, Guf-sur-Yvette France
Show AbstractIn nature actin gels provide cells with mechanical support and the ability to generate forces to fulfil various biological functions. Force generation in actin gels is mainly associated with directed polymerization of actin monomers into branched filaments that extend against the load. From a general point of view the branched actin filaments represent an active gel-like material. Its ability to generate forces by monomer insertion is also appealing from a material science point of view; in particular with regard to transferring the active properties of actin to artificial gels. However, while the biochemical processes associated with the actin polymerization are well understood, the molecular scale mechanism of force generation is still matter of debate.We use a simplified in vitro assay composed of purified proteins and artificial colloidal probes to directly study the forces during actin network growth. Force measurements on actin networks are performed using colloidal probe AFM techniques. In our setup the actin gel is compressed between a colloidal probe and a solid substrate while it deflects an AFM cantilever during expansion. Using fluorescence microscopy we observe the gel extension in direct conjunction with the AFM measurement. Furthermore, we vary the actin density and crosslinking via drugs or proteinic constituents like ARP2/3 and gelsolin. Generally, we observe increasing stall forces as the gel density or crosslinking density is increased. Results also suggest that the forces are limited by tensile stress build-up as the gel extends outward. Understanding of the gel behaviour in the framework of linear elasticity theory is subject to ongoing modelling efforts. In another experiment we analyze the motion of colloids propelled by the comet-like tail of polymerizing actin filaments. This allows us to test the well accepted Brownian ratchet models that explain force generation by monomer inclusion. We focus on analysing the curvature of the particle trajectories, and find that they deviate strongly from a Gaussian distribution. This implies that the underlying microscopic processes are fluctuating in a non-independent manner. A stochastic simulation shows, that the non-Gaussian curvature distribution can be explained by a positive feedback mechanism in which attached chains under higher tension are more likely to snap back from the colloid.
10:45 AM - MM6.6/NN7.6
A Supramolecularly Assisted Transformation of Block Copolymer Assemblies from Micelles into Nanotubes.
James Hedrick 1 , Sung Ho Kim 1 , Fredrik Nederberg 1 , Bob Jakobs 3 , Jeremy Tan 2 , Kazuki Fukushima 1 , Yiyan Yang 2 , Alshakim Nelson 1 , E. Meijer 3
1 , IBM Research, San Jose, California, United States, 3 , Eindhoven University of Technology and Nanotechnology, Eindhoven Netherlands, 2 , Institute of Bioengineering and Nanotechnology, Singapore Singapore
Show AbstractThe self-assembly of amphiphilic block copolymers in selective solvents provides a defined methodology to a variety of supramolecular assemblies including spherical micelles, worm micelles, vesicles, multicompartment micelles, toroids, and helices. Efforts to bolster the weak intermolecular interactions that effect micelle formation, include selective crosslinking of either the interior (core), exterior (corona) or throughout the micelle as well as non-covalent interactions. Examples of non-covalent interactions include polyelectrolyte complexes, hydrogen-bonding, charge-transfer complexes and stereocomplexation. The role of non-covalent interactions is particularly pronounced in peptide amphiphiles, a new class of self-assembling biomaterials with applications ranging from regenerative medicine to nanotechnology/engineering. These materials assemble into well-defined nanofibers as a consequence of the formation of beta-sheets in the peptide region. We will describe a supramolecularly assisted approach to transform the morphology of block copolymer assemblies using a rigid hydrogen bonding motif at the hydrophobic/hydrophilic block junction to affect the curvature of the copolymer assembly. Our target block copolymer is a poly(ethylene oxide)-b-polylactide (PEG-PLA), a widely studied material for drug/gene delivery, that assembles into spherical micelles in water with diameters ranging from 20-40 nm. PEG-PLA copolymers having a single rigid benzamide linkage at the block junction transformed the typical spherical micelle morphology into nanotubes, not typically seen for macromolecules. This supramolecularly assisted polymer assembly opens a new arena for making a nanotube structure that is anticipated to have application in nanomedicine.
MM8: Functional Biomimetics: Fabrication, Optical, Sensing, Mechanical Behaviors
Session Chairs
Nicholas Kotov
Christopher Li
Thursday PM, April 16, 2009
Room 3020 (Moscone West)
2:30 PM - **MM8.1
Unconventional Concepts in Microfluidics.
Stephan Herminghaus 1
1 , MPI for Dynamics and Self-Organization, Goettingen Germany
Show AbstractAs a natural analog to microelectronics, microfluidics has been pushed by increasing demands from technology. In particular, biotechnology asks for ever more sophisticated means for performing complex analysis with minute amounts of precious biomaterials. While some concepts have meanwhile been well established in technological processes, we are investigating novel concepts for the next generation of microfluidic processing. This comprises open microfluidic systems as well as the use of monodisperse gel-emulsions as defined compartmented media for presenting both the educts and products of interest. Furthermore, we use the interfaces between adjacent aqueous compartments as model biomembranes. These may serve for the in-situ investigation of membrane proteins as well as for novel concepts of self-assembled molecular electronics.
3:00 PM - MM8.2
Hierarchically Structured Polymer and Hybrid Tissue Scaffolds by Freezing.
Amalie Oroho 1 , Philipp Hunger 1 , Ulrike Gesa Wegst 1
1 Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractThe design requirements for tissue scaffolds appear deceptively simple: to provide a porous matrix with interconnecting porosity that promotes rapid cell ingrowth and, at the same time, possesses sufficient strength to prevent failure under physiological loads until full integration and healing is reached. Yet, the challenge persists to custom-make materials that mimic the diverse range in structure-property combinations of the different tissues in our body. An important reason for this is that frequently multi-level hierarchical composite structures are required, which are difficult to emulate in synthetic materials.One manufacturing process with which it is possible to manufacture structures with complex porosity is freezing followed by lyophilization. Utilizing the process of ice formation it is possible to create hierarchically structured materials with cellular or lamellar architecture that can be controlled across several length-scales. By varying either or both freezing rate and polymer chemistry, the pore geometry, surface roughness, and interfacial bonding, and with it the mechanical performance of the scaffold can be controlled. Our first results show that freeze-cast polymers have a specific stiffness, specific strength and specific toughness ideally suited for soft tissue applications.
3:15 PM - MM8.3
Rapid Nanoimprinting of Silk Fibroin Films.
Jason Amsden 1 , Ashwin Gopinath 2 , Luca Dal Negro 2 , David Kaplan 1 4 , Fiorenzo Omenetto 1 3
1 Biomedical Engineering, Tufts University, Medford, Massachusetts, United States, 2 Electrical and Computer Engineering , Boston University, Boston, Massachusetts, United States, 4 Chemical Engineering, Tufts University, Medford, Massachusetts, United States, 3 Physics, Tufts University, Medford, Massachusetts, United States
Show AbstractBiopolymers such as collagen, chitosan, and silk fibroin are promising materials for incorporation into biomedical optical devices. Silk fibroin is a particularly promising candidate because of all aqueous processing, optical clarity, and relatively easy functionalization. In addition, it is capable of being processed into thin mechanically robust films with excellent surface quality and optical transparency and it is possible to reproduce nanometer scale features by a soft lithography casting process (H. Perry, et, al., Adv. Mater., 20, 3070-3072, 2008). While this technique allows fabrication of at least 40 nm transverse features in silk fibroin films when cast at ambient conditions from an aqueous silk solution, the transition from the solution into a solid film takes considerable time (12-36 hours) hindering the capacity to readily produce multiple devices. In this study we describe a process by which a silk film can be nanoimprinted with multiple patterns in a very short time (seconds to minutes) by a low-temperature (<100 °C) and low pressure hot embossing technique. In addition, by adjusting the glass transition temperature of the silk film by varying the absorbed mositure, we describe a process by which the films can be nanoimprinted at room temperature. These nanoimprinting techniques combined with the favorable optical properties of silk opens avenues for fabrication of all-organic biophotonic components on the nanoscale that can be readily functionalized and employed as a new technology platform that seamlessly combines nanophotonics and and biopolymeric and bio-comaptible materials, adding a novel dimension to the space of biomedical optical devices.
3:30 PM - MM8.4
Biomimetic Assemblies of Peptide Nanowires, their Controlled RT Mineralization with Semiconductors, and their Applications in Pathogen Sensing Devices.
Roberto de la Rica 1 , Hiroshi Matsui 1
1 Dept. of Chemistry, City University of New York-Hunter College, New York, New York, United States
Show AbstractNon-lithographic fabrications of devices such as electronics and sensor have been studied extensively by assembling nanometer-sized building blocks into the device configurations. While various nanowires and nanoparticles with superior physical properties have been synthesized as the building blocks, more reproducible methods to assemble them onto precise positions are desirable to construct nanodevices. We developed triple helix peptide nanowires as multifunctional smart building blocks, and we used recombinant technology to design them in uniform length and diameter. The quantity of peptide nanowire was amplified by E. coli expression system. We designed these nanowires to incorporate biomolecular recognition components (antibody), and our strategy is to use those functionalized peptide nanowires, which can recognize and selectively bind a well-defined region on antigen-patterned substrates, as building blocks to assemble nanoscale architectures at uniquely defined positions. In order for the application in electric device fabrications, after configuring device geometries with these nanotubes by the biomolecular recognition, we turned on the biomineralization function of peptides on the nanotube sidewall to develop various material coatings such as metals and semiconductors for electronics and sensor applications. It should be noted that the coating morphology such as particle-domain size and inter-particle distance on the nanotubes could be tuned by peptide sequences and conformations. Due to these peptides’ catalytic function, some semiconductor coatings could be developed at room temperature on the nanotube. Besides the microelectronics, I will introduce the peptide nanotube pathogen sensor chips as another example of peptide nanotube device. Here the peptide nanotubes coated by the antibody of target pathogen were bridged between a pair of electrodes, and the detection was made by the capacitance change via the binding events of viruses on the nanotube. The advantage of this chip sensor as compared to conventional nanoscale chip sensor is that the characteristic capacitance values for pathogens could be used to indentify the stains of viruses in addition to the antibody recognition of the nanotube. Therefore, this system could be developed as a nanoscale pathogen diagnostic chip. The capacitance-based detection also reduced the chip-to-chip variation of the measurement as compared to traditional DC conductivity probe nanosensors by solving the nanoscale interface resistivity issue. The sensing with the peptide nanotube sensor chip was fairly robust and the detection limit was on the order of 100 virus particles/mL.
3:45 PM - MM8.5
Peptide-Nanowire Hybrid Materials for Selective Sensing of Small Molecules.
Michael McAlpine 1 , Heather Agnew 2 , Rosemary Rohde 2 , Mario Blanco 2 , Habib Ahmad 2 , Andreea Stuparu 2 , William Goddard 2 , James Heath 2
1 Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States, 2 , California Institute of Technology, Pasadena, California, United States
Show AbstractThe development of a miniaturized sensing platform for the selective detection of chemical odorants could stimulate exciting scientific and technological opportunities. Biomimicking smart materials which integrate chemical recognition moieties with sensitive transducers could provide a general system for highly specific smell sensors. Oligopeptides are robust substrates for the selective recognition of a variety of chemical and biological species. Likewise, semiconducting nanowires are extremely sensitive gas sensors. Here we explore a bio-inspired approach to mimicking olfaction by linking peptides to silicon nanowire sensors for the selective detection of small molecules. The silica surface of the nanowires is passivated with peptides using amide coupling chemistry. The peptide/nanowire sensors can be designed, through the peptide sequence, to exhibit orthogonal responses to acetic acid and ammonia vapors, and can detect traces of these gases from "chemically camouflaged" mixtures. Through both theory and experiment, we find that this sensing selectivity arises from both acid/base reactivity and from molecular structure. These results provide a model platform for what can be achieved in terms of selective and sensitive "electronic noses," and suggest application as implantable breath sensors for molecular disease indicators.
4:00 PM - MM8.6
Polysaccharide Composites: From Thin Films to Nanofibers.
Caroline Schauer 1 , Jessica Schiffman 1 , Keith Fahnestock 1 , Michael Laudenslager 1 , Valerie Binetti 1
1 MSE, Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractChitin is a colorless biopolymer found in shells of crabs and shrimp and is the second most abundant poly(saccharide) found in nature. Chitosan, the acid soluble form of chitin, is a non-toxic, biodegradable, biopolymer consisting primarily of β(1→4) linked 2-amino-2-deoxy-β-D-glucopyranose units, and is known for its metal chelation abilities. We harness the metal chelating ability of chitosan in two independent platforms: thin films for biosensing and nanofibrous meshes for filtration.Structurally colored polysaccharide thin films offer a promising materials platform for the development of a metal ion sensor due to the rapid, straightforward field-readable response of the visual color change which occurs upon exposure to metal ions. When a dissolved analyte binds to sites along the polymer backbone, film reflectance properties can be altered, either because of a dimensional change in film thickness or an optical change in the film effective RI. The optical and physical changes alter the path length of reflected light and, thus, change the perceived film color. Our research has focused on cross-linked polysaccharide thin films of chitosan, thiol modified chitosan, and alginate and composite thin films of polysaccharide-metallic nanoparticles.Electrospinning is a cost effect method of producing nanofibers from a large variety of bulk starting materials in a moderately easy, repeatable, and simple fashion. Both chitin and chitosan have successfully been electrospun solo into non-woven mats and polymer-composite membranes. Crosslinked chitosan and chitin nanofibrous meshes will be developed to harness the metal chelating properties of chitosan for filtration devices. The membranes are composed of randomly oriented cylindrical nanofibers and have large surface area-to-volume ratios. The mechanical properties of these membranes were evaluated utilizing a uniaxial tensile tester. For many applications, the creation of composite membranes would yield more desirable properties; therefore, organic molecules (glutaraldehyde), clays (diatomaceous earth), and nanoparticles (carbon black) were incorporated into the chitosan membranes. The creation of composite mats was confirmed using FTIR, solubility testing, and a Zeiss Supra 50/VP FESEM. We intend to tailor these membranes for water purification applications. Hence, flux capacity and chelation capabilities were tested and the resulting microstructure and presence of metal ions analyzed with a FESEM combined with energy dispersive spectroscopy (EDS). Finally, the crystalline domains of the chitin and chitosan membranes were confirmed using XRD since filtration capability is a function of amorphous and crystalline domains. As a result of their intrinsic properties, as well as nanoscale fibers and pores, chitin and chitosan composite membranes offer unique properties that can be tailored to suit a variety of applications.
4:30 PM - MM8.7
Biomimetic Ultrathin Whitening from Capillary Force Induced Random Clustering of Micropillar Arrays.
Dinesh Chandra 1 , Shu Yang 1 , Andre Soshinsky 2 , Robert Gambogi 3
1 Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 , Johnson and Johnson Consumer Products, Morris Plains, New Jersey, United States, 3 , Johnson and Johnson Consumer Products, Skillamn, New Jersey, United States
Show AbstractWhiteness is important to many technologies, including papers, coatings and displays. Nature provides elegant examples of structural colors as shown in the scales of white beetles, which compose of a random network of microfilaments that is only a few microns thick. Here we report fabrication of biomimetic ultrathin whitening layers (less than 9 micron thick) from randomly collapsed hydrogel micropillars, consisting of 2-hydroxyethyl methacrylate (HEMA) and glassy methyl methacrylate (MMA). When exposed to water, followed by drying in air stream, the micropillars were softened, bent and randomly clustered together due to competition between capillary force and elastic restoring force of the pillars, resulting in white appearance. The degree of whiteness is comparable to the uncoated paper, which is at least 120 microns thick, and its whiteness is caused by cellulose filaments network. By varying the relative composition of the two polymeric components, we controlled the elastic modulus of the pillars in the wet state, and thus the cluster size and resulting whiteness. By minimizing the sum of capillary interaction energy and elastic bending energy of the pillars for a cluster, we estimated the average cluster size as a function of elastic modulus of the pillars, which agreed well with the experimental observation.
4:45 PM - MM8.8
A bottom-up Technological Approach to Biophotonics.
Luca De Stefano 1 , Ilaria Rea 1 , Edoardo De Tommasi 1 , Mario De Stefano 2 , Annalisa Lamberti 3 , Ivo Rendina 1
1 Naples, IMM-CNR, Naples Italy, 2 Dept. of Environmental Sciences, Second University of Naples, Naples Italy, 3 Dept. of Biochemistry and Medical Biotechnologies, University of Naples "Federico II", Naples Italy
Show AbstractFrom materials science and optical point of view, useful photonic properties can be found when the device fabrication process can be controlled at finely. This is the reason why complex micro- and nano-structured materials for photonic applications are designed and fabricated using the best available technologies in the top-down approach. The opposite method to engineering systems at the sub-micron-scale is the bottom-up way inspired by natural organisms: biology provides tools for controlling and/or synthesizing materials at the molecular level. Some biological organisms could exhibit ordered geometries and complex photonic structures which often overcome the products of the best available fabrication technologies. An example of this control is represented by the diatoms, microalgae with a peculiar cell wall made of amorphous hydrated silica valves, reciprocally interconnected like a Petri dish in a structure called “frustule”. The valve surfaces exhibit specie-specific patterns of regular arrays of holes similar to man-made photonic crystal structures. More of 100000 types of diatoms have been discovered and classified by different shapes of their cell walls. We focused our investigations on a centric diatom, the Coscinodiscus walesii, characterized by a diameter of about 150 μm and a radial symmetry very similar to that of a photonic crystal fiber. We have demonstrated that this diatom acts as an artificial microlens: its frustule can focalize the light in a spot less than 10 μm, the focal length depends on the wavelength of the incident radiation. This focusing effect it is due to coherent superposition of waves scattered by the holes present on the diatom surface. Diatoms surface can be also properly functionalized to bind a molecular probe which specifically recognizes a target analyte: the intricate structure of diatoms frustules offers a lager surface area respect to a planar glass slide. We have covalently linked on the diatoms frustules a dye labelled antibody and studied the efficiency of the chemical functionalization by a fluorescence macroscopy system. Then, we have verified that the antibody, linked on the diatom surface, still recognizes specifically its antigen. From all these results, we believe that diatoms could really be a possible technological platform for biophotonic application.
5:00 PM - MM8.9
Bio-inspired Assembly of Functional Nanomaterials.
Stephen Morin 1 , Song Jin 1
1 Chemistry, University of Wisconsin - Madison, Madison, Wisconsin, United States
Show AbstractIn biomineralization processes nature demonstrates superior strategies for the assembly of nanomaterials into complex architectures. Here we adapt principles derived from biomineralization to the bottom up assembly of nanoscale functional materials. Specifically, carefully positioned surface organic molecules are used to control where inorganic nanocrystals nucleate and grow generating predetermined micro/nanopatterns directly from solution. In initial studies, we patterned surface carboxylic acid groups onto commodity engineering polymers and used them to control the nucleation of crystalline inorganic nanomaterials, such as the semiconductors ZnO and CdS, creating micropatterned arrays on the polymer surface directly from aqueous solutions. To extend this bio-inspired approach to truly bottom-up nanoscale assembly, we then utilized self-assembling nanostructured block copolymers to nucleate arrays of functional nanocrystals (quantum dots) directly from aqueous solutions. This new platform enabled the generation of highly tunable linear arrays of metal sulfide nanocrystals, such as CdS and ZnS, with sub 60 nm periodicities. We are now expanding our strategies to macromolecular templates with controlled sequences and chemical functionality, such as synthetic collagen fibers and β-peptide fibrils, in an effort to specifically nucleate and assemble a diverse family of inorganic nanocrystals into programmed architectures. The organized nanomaterial structures produced and the fundamental understandings gained from these assembly strategies will prove invaluable in the push to create functional material systems on ever shrinking length scales.
5:15 PM - MM8.10
Mechanical Properties of Hierarchically Ordered Large and Small Molecule Self-Assemblies.
Daniel Carvajal 1 , Ronit Bitton 2 , Kenneth Shull 1 , Samuel Stupp 1 2
1 Meterials Science and Engineering, Northwestern University, Evanston, Illinois, United States, 2 IBNAM, Northwestern University, Chicago, Illinois, United States
Show AbstractRecently the Stupp group discovered a new form of large and small molecule self-assemblies (Capito et al. Science 319, 1812, 2008) made from high molecular weight hyluronic (HA) acid and peptide amphiphiles (PAs). These closed membranes (sacs) have a unique structure which consists of parallel PA fibers at the HA interface when the membrane is formed. A perpendicular layer of fibers, formed by the self-assembly of PA around HA molecules that reptate through the membrane, is observed at longer times. HA reptation is proposed to be driven by differences in osmotic pressure between the solutions.A better understanding of the structure-property relationship of the membrane/sac is essential for tailoring its characteristics for desired applications, yet its hierarchical structure presents a unique challenge in quantifying its mechanical properties. To this effect, the relationship between incubation time and mechanical properties of the assemblies produced was explored by varying the incubation time from minutes to hours. The mechanical properties of the membranes were directly measured using membrane inflation techniques. Drop shape analysis techniques were used to investigate the swelling behavior of the sac in PA solutions, water, and solutions with set osmotic pressures. Osmotic pressure measurements of these solutions were also performed before, during, and after sac formation in order to gain an understanding of the driving force behind HA reptation through the membrane. It was found that the kinetics of perpendicular fiber formation and growth could be suppressed and/or controlled by using specific initial osmotic pressure differences. The permeability and robustness of the membranes and sacs could also be altered by varying incubation times. These observations and measurements are a big step towards forming rationally designed assemblies based on these systems.