OO1: Bio-enabled Material Templates
Chair: Valeria Milam
- Tuesday AM, April 10, 2012
- Marriott, Yerba Buena, Nob Hill BC
8:30 AM - *OO1.1
From Atoms to Structures -How Spiders turn Weakness into Strength
Civil and Environmental Engineering, MIT, Cambridge, Massachusetts, USA.Show Abstract
This talk will explain how materials in biology are synthesized, controlled and used for a variety of purposesâ€”structural support, force generation, catalysis, or energy conversionâ€”despite severe limitations in available energy, quality and quantity of building blocks. We demonstrated that the chemical composition of biology's materials plays a minor role in achieving functional properties. Rather, the way components are connected at different length-scales defines what material properties can be achieved, how they can be altered to meet functional requirements, and how they fail in disease states. We have achieved this by using the worldâ€™s fastest supercomputers to predict properties of complex materials from first principles, in a multiscale approach that spans orders of magnitude in scale. This method, combined with experimental studies, allows us to build virtual â€œin silicoâ€ material models that provide unseen insight into the workings of natural and synthetic materials from the bottom up. We demonstrate this approach in a case study of spider silk, one of the strongest yet most flexible materials in Nature, despite being made out of some the simplest, most abundant and intrinsically weak proteins, including weak hydrogen bonding. We discovered that the great strength and flexibility of spider silkâ€”exceeding that of steel and other engineered materialsâ€”can be explained by the materialâ€™s unique structural makeup that involves multiple hierarchical levels. These hierarchical levels span from the genetic information that defines the protein sequence to the structural scale of an entire spider web. Thereby, each level contributes to the overall properties, but the remarkable properties emerge because of the synergistic interaction across the scales where the sum is more than its parts. By translating this insight gained from the study of natural materials such as spider silk to engineered materials such as carbon nanotube fibers, graphene composites or metal-polymer films, our research has resulted in an engineering paradigm that facilitates the design of sustainable materials starting from the molecular level, leading to the formation of hierarchical structures that span all scales from nano to macro. By utilizing a mathematical tool from category theory we illustrate the hierarchical materials design concept by drawing an analogy to a seemingly far and distant fieldâ€”music. Reminiscent of protein materials, the integrated use of structures at multiple scales is the key to provide superior functional properties despite limitations in available building blocks, a set of musical instruments such as piano, violin or cello. In music, tones are played at different pitch, accentuation or duration and then assembled into melodies. The collective interaction of melodies, played by different instruments and arranged in a particular way, eventually results in the powerful expression of a symphony.
9:00 AM - OO1.2
Robust and Responsive Silk Ionomer Microcapsules
Ye1 2, Olga
School of Chemical Engineering, Nanjing Forestry University, Nanjing, China; 2,
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA; 3,
Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, USA.Show Abstract
We demonstrated the LbL assembly of thin shell microcapsules from biocompatible and biodegradable silk fibroin counterparts modified with poly(lysine) and poly(glutamic) acid. Grainy, porous texture and exponential growth shell facilitate their high permeability. The crosslinked microcapsules are robust and extremely stable in the unusually wide pH range from 1.5 to 12.0 in striking contract to conventional synthetic polyelectrolyte LbL capsules which are readily dissolved at extreme pH conditions. These microcapsules show pH triggered response at acid (pH < 2.5) and basic (pH > 11.0) conditions with 800% increases in volume without compromising capsule integrity. These changes are accompanied by reversible changes in â€œopen/closedâ€ shell morphology which are exploited for pH-triggered loading and unloading of large macromolecules.
9:15 AM - OO1.3
Protein Nanofibers as Functional Templates in Hybrid Bionanomaterials
Organic Chemistry III, Macromolecular Chemistry & Biomaterials, Ulm University, Ulm, Germany.Show Abstract
Peptides and proteins are able to undergo specific self-assembling pathways resulting in the formation of nanofibers with diameters in the range of a few nanometers and lengths exceeding several micrometers. In addition to their implications in neurodegenerative diseases such as Alzheimer's and Parkinson's, an important aspect of such so-called amyloid fibers is their role as functional entities in biological systems. They adopt important roles in biosynthetic pathways and as structural components in lower organisms. The highly ordered arrangement of the peptide chains within the nanofibers, the high nanofiber aspect ratio and the presence of a large variety of functional groups makes them interesting building blocks and templates for novel biological nanomaterials. However, the ability to exploit the functional properties of natural protein nanofibers and to transfer their nanoscopic properties into macroscopic materials are key issues on their way towards nanotechnological applications. Herein, we discuss how the chemical and physical properties of amyloid nanofibers can be exploited to develop polymeric and inorganic peptide hybrid nanomaterials. Using noncovalent interactions, amyloid nanofibers can be spun into high-performance biofibers with diameters from tens to hundreds of Âµm, exhibiting tensile strengths of about 300 MPa and elastic moduli of about 10 GPa. Within the macroscopic material, the nanofiber building blocks adopt a highly ordered arrangement and template the mineralization of calcium phosphate. The resulting hierarchically structured biocomposite exhibits a significant increase in bending rigidity and mimicks the structural characteristics of fibrolamellar bone. In addition, protein nanofibers are known to exhibit hydrophobic binding pockets that are able to interact with small organic molecules, e.g dyes. Here, we demonstrate that the nanofibers are capable to template the polymerization of small organic molecules into polymers, resulting in water-soluble nanoscopic 1D polymer-protein architectures. These novel polymer-protein hybrid nanomaterials have potential applications ranging from nanomedicin to energy conversion.  T. P. J. Knowles, A. W. Fitzpatrick, S. Meehan, H. R. Mott, M. Vendruscolo, C. M. Dobson, M.E. Welland. Science 2007, 318, 1900  D. M. Fowler, A. V. Koulov, W. E. Balch, J. W. Kelly. Trends Biochem. Sci. 2007, 32, 217  C. Meier, M. E. Welland. Biomacromolecules 2011, 12, 3453
9:30 AM - OO1.4
Infrared Transmission through Subwavelength Pores in Gold Replicas of Coscinodiscus Asteromphalus Diatoms
School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA; 2,
School of Materials Science and Engineering, Georgia Institute of Technolgy, Atlanta, Georgia, USA.Show Abstract
Nature provides a vast number of intricate three-dimensional (3D) inorganic structures formed by living organisms. Diatoms (single-celled algae) are among the most versatile structure-forming organisms that form a silica-bearing microshell (frustule) with a specific 3D morphology in a rich variety of shapes and patterned features. Culturing of a given diatom species, followed by shape-preserving chemical conversion of the resulting frustules, can yield enormous numbers of structures with a particular 3D morphology, tailored chemistry, and potentially new (non-biological) properties. Coscinodiscus asteromphalus (CA) diatom frustules possess organized, quasi-periodic patterns of many hundreds of micrometer size pore diameters. Here we report the conversion of CA diatom frustules into 3D gold replicas via a scalable wet chemical process and the infrared transmission and reflection spectra of the gold replicas, which exhibit significant infrared transmission at wavelengths substantially larger than the diameters of the pores. The transmission spectra were simulated using a surface plasmon-interference model, which considers the excitation and interference of surface plasmons on the incident and exiting sides of the gold frustule replica, and radiation of optical energy from the exiting side. We will discuss the experimental and modelling results on the infrared properties of the gold CA replicas, as well as those of well-ordered hexagonal hole arrays and hole arrays matching the hole pattern of the CA frustules that were fabricated in gold films by focused ion beam milling. The reasonably good agreement between the simulated and measured position and intensity of the IR transmission peak indicate that the IR transmission of these gold frustule replicas was enabled by the generation, transmission, and radiation of surface plasmons.
10:00 AM -
10:30 AM - *OO1.6
Role of 3D Scaffold Structure in Controlling Stem Cell Shape and Differentiation
Polymers Division, NIST, Gaithersburg, Maryland, USA.Show Abstract
It is well-known that 2D surface topography from the micro- to the nanoscale can influence stem cell behavior. However, the role of 3D scaffold structure in directing stem cell function has not been elucidated. Thus, we have used a library approach to systematically screen the effect of widely varied scaffold structures on primary human bone marrow stromal cell (hBMSCs) function. Microarray testing revealed that each type of scaffold structure tested induced a unique gene expression signature demonstrating that cells are keenly sensitive to scaffold structure. Further, hBMSC behavior was dependent upon scaffold structure. hBMSCs underwent osteogenic differentiation on nanofiber scaffolds while freeform fabricated scaffolds enhanced hBMSC proliferation. Since cell morphology and cell behavior are linked, hBMSC shape was assessed. hBMSCs took on a highly branched, elongated morphology on nanofiber scaffolds but had a well-spread, more rounded morphology on freeform fabricated scaffolds. These results suggest that scaffolds controlled hBMSC behavior by controlling their shape and indicate that 3D scaffold structure must be designed to drive cells into morphologies that direct their fate. Next, scaffold niche dimensionality was measured. Though it is widely accepted that 3D scaffolds present a more physiological environment than 2D substrates, it not known which scaffolds provide cells with a truly 3D niche. Thus, 3D confocal images of hBMSCs cultured in different scaffolds were analyzed to determine cell dimensionality. This required development of new imaging metrics to determine if cells had a predominantly 2D or 3D morphology. hBMSCs on flat surfaces were assessed as 2D controls. hBMSCs cultured in 3D scaffolds were not as â€œ3Dâ€ as was expected, but were more 3D than were hBMSCs cultured on 2D flat surfaces. Cells had differing degrees of 3Dness in the different scaffolds indicating that cell niche dimensionality varied with scaffold structure. This work yields a new approach for determining if a scaffold provides a 3D niche for cells. Taken together, these results provide a new way to think about how scaffold properties can be tuned to control stem cell fates through control of cell shape and dimensionality.
11:00 AM - OO1.7
Enzyme-guided Crystal Growth for Next Generation Biosensors
de la Rica1, Laura
Materials, Imperial College London, London, United Kingdom; 2,
, Universidade de Vigo, Vigo, Spain.Show Abstract
Enzymes are essential components of the bionanotechnology toolbox that have found applications in areas as relevant as nanomaterials synthesis, nanolithography and the fabrication of sensors.[3,4] In particular, enzymes have been shown to work as nanoreactors that finely control the kinetics of crystal growth to yield nanocrystals of defined size, shape and crystallinity. Furthermore, enzymes are extremely useful labels that amplify the signal of biosensors, a feature that has been extensively used in enzyme-linked immunoassays (ELISA). Here we present a new generation of biosensors that merge these two concepts to yield ultrasensitive sensors with characteristics that overcome some limitations observed in classical detection schemes. When combined with the specific recognition feature of antibodies, the proposed signal amplification method can be used as a universal platform to detect molecules of great medical relevance such as cancer biomarkers and infectious diseases. For example, we designed a signal amplification scheme that yields a larger signal when the target molecule is less concentrated, which allows the detection of ultralow concentrations of cancer biomarkers in serum with high confidence. In this approach, the optical properties of plasmonic transducers are tailored by the growth of silver nanocrystals guided by glucose oxidase. By harnessing the kinetics of crystal growth with the enzyme to control the morphology of the nanocrystals, the response of the sensor can be engineered to yield a drastic signal at ultralow concentrations of the analyte, which radically decreases the possibility of a false positive by undesired interferences. This is demonstrated by detecting the cancer biomarker prostate specific antigen (PSA) with a concentration as low as 1 ag/mL spiked into whole human serum. In another approach, the growth of gold nanoparticles is utilized as the signal in ELISA. The key step in this methodology is to limit the rate of growth of the nanocrystals with the enzyme catalase so that the intensity of the color of the solution depends on the concentration of target molecule. Moreover, the enzyme also determines the size and morphology of the nanocrystals, which dictates a change in the color of the solution from blue to red that allows detecting ultralow concentrations of clinically relevant proteins by simple visual inspection. The signal amplification mechanism based on enzyme-guided crystal growth could be adapted to other optically active nanocrystals such as quantum dots.  de la Rica, R.; Matsui, H. Angew. Chem. Int. Ed. 2007, 47, 5415-5417.  de la Rica, R.; Fabijanic. K. I.; Baldi, A.; Matsui, H. Angew. Chem. Int. Ed. 2010, 49, 1447-1450.  de la Rica, R.; Fratila, R.; Szarpak, A.; Huskens, J.; Velders, A. H. Angew. Chem. Int. Ed. 2011, 50, 5703-5706.  Aili, D.; Mager, M.; Roche, D.; Stevens. M. M. Nano Lett. 2011, 11, 1401-1405.
11:15 AM - OO1.8
Spatially Modulated Doping of Single-layer Graphene and MoS2 by Self-assembled Peptide Nanowires
Hayamizu1 2, Christopher
GEMSEC, Genetically Engineered Materials Science and Engineering Center, University of Washington, Seattle, Washington, USA; 2,
PRESTO, Japan Science and Technology Agency (JST), Tokyo, Japan.Show Abstract
Developing elegant hybrid systems between biological molecules and nanomaterials is key in creating novel bio-nanoelectronic devices, where versatile biomolecular functions are integrated with well-established electronics of nanomaterials. Single-layer graphene, MoS2, and other atomic single layers (ASLs), represent ideal nanomaterials to form such bio/nano systems due to their two-dimensional structure. Biomolecules self-assembling into ordered nanostructures on ASLs offer a novel bottom-up technology, where organized biomolecular architectures spatially govern the electronics of ASLs. Despite the enormous potential in bridging nano- and bio-worlds at the molecular scale, no work has yet realized a way to combine the self-assembled nanostructures of biomolecules to control electronic and/or optical properties of ASLs. Here, we demonstrate that engineered dodecapeptides self-assemble into two-dimensional supramolecular networks of â€œpeptide nanowiresâ€, on the surface of two different ASLs: single-layer graphene and MoS2. Peptide nanowires have uniform dimensions, typically ~1-nm thick, ~12-nm wide, and micro-meters in length, and introduce electric charges into single-layer graphene and MoS2 via biomolecular doping. Unique to peptide nanowires, we find that their abrupt boundaries create electronic junctions in graphene, which manifest themselves within the single-layer as a self-assembled electronic network. Furthermore, we demonstrate that designed peptides modify both conductivity and photoluminescence of single-layer MoS2. Supramolecular peptides show unique electronic interactions with ASLs. While the absence of peptide organization on surfaces results in random doping, ordered peptide nanowires predictably modify the conductivity of graphene. The coherent peptide conformation in nanowire architectures on ASLs potentially provides new foundations to study primary interactions at the bio/nano interface. Furthermore, peptides with different amino acid sequences can recognize different types of ASLs, verified by the demonstration of unique molecularly ordered patterns on single-layer graphene and MoS2, respectively. Controlling nano-electronics through biologically-coded self-assembled peptides is now possible, potentially opening new avenues in self-assembled nanodevices for future bioelectronics and biophotonics. Research supported by NSF-MRSEC, NIH-T32, NSF-BioMat and JST-PRESTO programs.
OO2: Macromolecule Design Strategies for Bio-enabled Materials Systems
Chair: Harry Bermudez
- Tuesday PM, April 10, 2012
- Marriott, Yerba Buena, Nob Hill BC
1:45 PM - *OO2.1
Genetically Encoded Stimulus Responsive Elastin-like Polypeptides: Applications in Drug Delivery
Biomedical Engineering, Duke University, Durham, North Carolina, USA.Show Abstract
This talk will cover recent developments in my laboratory on the genetically encoded synthesis of stimulus-responsive recombinant biopolymers and their self-assembly into nanoparticles for drug delivery. In the first example, we designed a chimeric polypeptide that consists of two segments: an ELP segment that consists of (VPGXG)n repeats (where n ranges from 60-150) followed by a short (GGY)8 segment, and showed that attachment of multiple copies of a hydrophobic molecule at the Y position can impart sufficient amphiphilicity to the polypeptide and thereby drive its self-assembly into near-monodisperse nanoparticles with the attached hydrophobic small molecule embedded in the core of the nanoparticle. This is an interesting finding, because it appears that any molecule with a hydrophobicity that is greater than a threshold value appears to drive attachment-triggered self-assembly of the chimeric polypeptide into a nanoparticle. Because many cancer chemotherapeutics are insoluble hydrophobic small molecules with poor bioavailability, this approach of attachment-triggered encapsulation of small hydrophobic molecules into soluble nanoparticles has great utility to increase the solubility, plasma-half-life and tumor accumulation of cancer chemotherapeutics. As a specific example, I will show how conjugation of multiple copies of the cancer chemotherapeutic Doxorubicin (Dox) via a pH-sensitive linker to the end of an ELP spontaneously triggers ELP self-assembly into near-monodisperse micelles. These nanoparticles are ~40 nm in diameter, release drug at pH 5.0 (relevant to endo-lysosomal release), are taken up by cells, show subsequent localization of the drug to the nucleus, and are cytotoxic. Notably, these Dox-loaded nanoparticles have a four-fold higher maximum tolerated dose than free drug and induce near complete tumor regression in a murine cancer model following a single dose. In the second example, I will discuss diblock ELPs with a histidine-rich hydrophobic block to create pH-responsive nano-particles. We show that these systems self-assemble in response to three orthogonal triggers: temperature can be used to self-assemble the ELPBCs into micelles below physiological temperature, a drop in pH that corresponds to tumor pH leads to micelle disassembly, and addition of physiological concentrations of Zn2+ can further stabilize these micelles or alternatively can be used to trigger their self-assembly at lower temperatures with no adverse impact on their pH sensitivity. These pH-sensitive nanoparticles achieve a more homogeneous intratumoral spatial distribution than their pH-insensitive counterparts, indicating their potential as delivery vehicles of drugs or imaging agents to solid tumors. This family of self-assembling ELPs provides rich opportunities for application in biotechnology and medicine.
2:15 PM - OO2.3
Design of Multi-component Self-assembled Peptide Amphiphile Micelles for Treatment of Atherosclerosis
Chemical and Biomolecular Engineering, University of California- Berkeley, Berkeley, California, USA; 2,
Materials Department, University of California- Santa Barbara, Santa Barbara, California, USA; 3,
Institute for Molecular Engineering, University of Chicago, Chicago, Illinois, USA.Show Abstract
Atherosclerosis, a disease characterized by the development of plaques, is one of the major causes of cardiovascular disease, which continues to be a leading cause of death in the United States. The lack of non-invasive treatment options for atherosclerosis once a plaque has developed presents an opportunity to design a drug delivery vehicle that can deposit a drug of interest at the site of the plaque. In order to develop such a treatment, markers of atherosclerosis must be identified that distinguish plaques from healthy sections of arteries. Universal markers for atherosclerosis exist and provide a means for a targeted drug delivery approach. One such late stage marker is fibrin, which forms as part of the blood clotting process, and preliminary work shows that the peptide CREKA selectively binds to fibrin in in vivo models of atherosclerosis . Early stage targets are also being explored including cellular adhesion markers of inflammation present on the artery wall. Drug delivery vehicles are created using peptide amphiphiles as the building blocks to form self-assembled micelles. Micelles provide the ability to load a drug of interest into the hydrophobic core or hydrophilic corona, as dictated by the structure of the drug. Peptide amphiphiles are formed by conjugating a hydrophilic head group, formed from a targeting peptide, to a hydrophobic tail, such as an alkyl chain, generally 12-18 carbons in length. Spherical micelles formed through the conjugation of a peptide, such as CREKA, to a DSPE-PEG tail vary in the range from 10-20 nm in diameter as determined by dynamic light scattering and cryogenic transmission electron microscopy. Critical micelle concentrations (CMC) obtained are on the order of 10 uM. The role of the hydrophobic tail is also being investigated to determine the function it plays in increasing the stability of micelles when in contact with proteins commonly found in the body, such as albumin. Additionally, the incorporation of multiple targeting peptides provides a multifunctional vehicle capable of binding to both early and late stage markers of atherosclerosis. The ability to tailor the size of micelles using two targeting peptides combined in a mixed micelle conformation will be discussed. The presentation of multiple peptide targeting components in a single micelle is verified by FRET.  Peters, D, et al. Targeting Atherosclerosis by Using Modular, Multifunctional Micelles. PNAS. 2009; 106 9815-9819.
2:30 PM -
3:00 PM - *OO2.4
Rationally Assembled Multifunctional Materials
, Brookhaven National Laboratory, Upton, New York, USA.Show Abstract
A fabrication of nanomaterials with tailored and multifunctional properties requires ample abilities to arrange different types of functional nanoparticles into designed architectures. The assembly strategy based on bio-selective encoding of nano-components, e.g. with DNA, potentially offer a power of self-assembly and the design versatility. Although a significant progress was demonstrated in the area of DNA-mediated assembly, assembled structures typically contain only one type of particles. We developed a broadly applicable strategy for DNA functionalization of nanoparticles of different types. Our approach allows for assembly of multi-functional heterogeneous materials from such nanoparticles and their combinations. The detailed studies of these heterogeneous assemblies, clusters and ordered arrays, reveals, for example, that a significant modulation of optical properties of individual components can be achieved due to plasmonic and collective effects. Our findings and their applications to optical and bio-detection areas will be discussed. Research is supported by the U.S. DOE Office of Science and Office of Basic Energy Sciences under contract No. DE-AC-02-98CH10886.
3:30 PM - OO2.5
Exploring Locked Nucleic Acids as a Reversible Biomaterials Assembly Tool
Milam1 2 3.
School of Materials Science & Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA; 2,
Dept. of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA; 3,
Institute for Bioengineering & Biosciences, Georgia Institute of Technology, Atlanta, Georgia, USA.Show Abstract
Oligonucleotides hold great promise as a programmable biomaterials assembly and disassembly tool. Modified oligonucleotides, such as locked nucleic acid (LNA), have been of recent interest in physiological applications due to their superior nuclease resistance over DNA. LNA is the most promising nucleic acid analog due to its reportedly low cytotoxicity effects. Past work in this area has focused on reversing DNA-linked assemblies (in the absence of cells) through thermal denaturation steps. Previously, the Milam lab has reported studies using competitive hybridization events to disassemble DNA-linked particles under isothermal conditions. Here, we focus on programming the isothermal assembly and disassembly of LNA-linked colloidal particles. Initially, to drive LNA-mediated particle assembly, we employ short duplexes that are either 1) perfectly-matched or 2) contain a single, center mismatch. Certain parameters must be controlled to minimize nonspecific attractions between LNA-functionalized colloidal particles, including the surface duplex density and the number ratio of large and small particles. To induce LNA-mediated disassembly, longer, perfectly-matched target strands are added to drive competitive displacement of the lower-affinity, original partner strands. Confocal microscopy confirms substantial assembly for both perfectly-matched and mismatched cases. Flow cytometry results indicate that the perfectly-matched targets are more efficient at displacing the mismatched duplex strands than perfectly-matched duplex strands. This work demonstrates that LNA can be used to assemble and disassemble colloidal particles under isothermal and physiologically-relevant conditions.
3:45 PM - OO2.6
Tunable Release of Active Oligonucleotides from Uncrosslinked Gelatin Microspheres
, Georgia Institute of Technology, Atlanta, Georgia, USA.Show Abstract
We are investigating gelatin-based matrices for the temporary encapsulation, then release of active, short oligonucleotide stands. While most previous work has focused on using gelatin matrices with covalent crosslinks in which protease digestion triggers release of encapsulated agents, we are using uncrosslinked gelatin in order to preserve its relevant temperature sensitivity for biomaterials applications such as drug delivery. Following encapsulation of DNA, polyelectrolyte bilayers are deposited on the gelatin matrices to act as a temporary diffusion barrier and prevent premature escape of DNA. We found that this polymer coating typically hindered DNA release at room temperature, but promoted at least 5-fold greater release at 37 Â°C relative to the room temperature samples. DNA released from the gelatin matrices was quantified through subsequent hybridization events with polystyrene particles functionalized with the complementary partner sequence. These hybridization studies confirmed that the gelatin matrix does not appear to compromise subsequent duplex formation capabilities of DNA. Our first studies in this gelatin-DNA system involved the use of small uniform â€œblockâ€ geometries as well as polydisperse microspheres to assess the role of the polyelectrolyte coating and gelatin matrix. More recently, however, we have employed a microfluidics-based processing approach to form large, monodisperse gelatin microspheres for DNA encapsulation. Overall, our studies indicate that these DNA-loaded, uncrosslinked gelatin carriers represent a promising system for triggered release of encapsulated oligonucleotides for a variety of bio-related applications.
4:00 PM - *OO2.7
Engineering DNA-based Materials Systems for Real-world Applications
Biological and Environmental Engineering, Cornell University, Ithaca, New York, USA.Show Abstract
DNA plays a critical role in all living organisms as the carriers and also the regulators of genetic information. A myriad of enzymes have been evolved that can control and process DNA efficiently and elegantly. Our research focuses on using DNA as both genetic (bio) and generic (nano) materials: a combination of these two distinct but complementary aspects, i.e., biomaterial with nanomaterial, has enabled us to establish a variety of DNA-based materials systems that are specifically designed for real-world applications. More specifically, inspired by polymers, we have successfully created different topologies of DNA from which we have since developed dendrimer-like DNA, DNA-hydrogels, DNAsomes, and DNA-nanoparticle hybrid assemblies, all in bulk scale. With these novel DNA-based materials, we are exploring real-world applications in diagnostics, cell-free protein production, drug delivery, cell culture and novel optoelectronics. For more information, please refer to our relevant publications:
1. Nature Communications, accepted, (2011)
2. Chemical Society Reviews, in press, (2011)
3. Nature Nanotechnology, 6, 268-276 (2011)
4. Angew Chem Int Ed. 49, 380-384 (2010)
5. Nature Protocols, 4, 1759-1770 (2009)
6. Nature Nanotechnology, 4, 430-436 (2009)
7. Nature Materials, (Article) 8, 519-525 (2009)
8. Nature Materials, (Article) 8, 432-437 (2009)
9. Nature Nanotechnology, (Cover Article) 3, 682-690 (2008)
10. Nature Materials, 5, 797-801 (2006)
11. Nature Protocols, 1, 995-1000 (2006)
12. Nature Biotechnology, 23, 885-889 (2005)
13. Nature Materials, 3, 38-42 (2004)
OO3: Poster Session: Bio-enabled Materials Systems
Chair: Marc Knecht
- Tuesday PM, April 10, 2012
- Moscone West, Level 1, Exhibit Hall
5:00 PM - OO3.2
Biomimetic Synthesis of Pd Nanoparticles for Energy Efficient Catalysis
Chemistry, University of Miami, Coral Gables, Florida, USA; 2,
, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, USA.Show Abstract
Rapid environmental degradation and exhaustion of limited resources caused by processes that fuel technological advancements require the development of new materials that function more efficiently and operate under energy-neutral and eco-friendly conditions. This multi-pronged approach in green chemistry includes the need to efficiently produce materials and the necessity of reducing waste and production costs. We have demonstrated this approach by utilizing the Pd4 peptide in the synthesis of Pd nanoparticles for the Stille coupling reaction. This unique peptide, isolated via phage display, specifically recognizes fcc Pd and binds to the surface of growing materials in solution to generate peptide-capped Pd nanoparticles. These materials were used as catalysts for the coupling reaction between different aryl halides and organostannane reagents in aqueous solution at room temperature giving quantitative product yields using ultra low catalyst loadings (>0.001 mol% Pd). The catalysts are insensitive to reagent functional groups, are reactive for both electron withdrawing and donating aryl halides, and are selective to produce the new C-C bond. As a model system for green catalysis, it is essential to determine the catalytic mechanism driven by the peptide-capped Pd nanoparticles in order to optimize their efficiency by providing critical information regarding the structure-function relationship. By monitoring the turnover frequency (TOF) of the reaction at different catalyst loading, the results suggest an atom leaching mechanism is at work where the initial oxidative addition step at the nanoparticle is able to abstract Pd species from the surface, which was confirmed using a unique quartz crystal microbalance analysis.
5:00 PM - OO3.3
Peptide-based Synthesis, Characterization and Catalytic Applications of Metal Nanoparticle Networks
Chemistry, University of Miami, Coral Gables, Florida, USA.Show Abstract
Recent advances in the development of methods for the fabrication of metallic nanostructures reveal great interest in adapting bio-inspired approaches to achieve technologically important materials. By employing such processes, emerging directions could be achieved for the production of inorganic materials under eco-friendly conditions of solvent, temperature, and pressure; however, new methods to control the shape, size, and composition are required. Among these materials, Pd nanoparticles attract great attention due to their excellent catalytic properties. We have fabricated multiple inorganic nanomaterials using a self-assembling peptide that acts as a template in the solution where spherical as well as non-spherical nanostructures can be prepared. Spherical particles, 1-dimensional nanoribbons, and dense/networked nanoparticle networks (NPNs) were observed by selecting the metal:peptide ratio in the reaction. The synthetic method and final nanostructures were fully characterized by UV-vis spectroscopy, transmission electron microscopy, dynamic light scattering, and powder X-ray diffraction analysis. The synthesized nanostructures were subsequently employed as catalysts for two entirely different classes of reactions, including Stille coupling and 4-nitrophenol reduction, such that the catalytic efficiency of the materials was studied as a function of both the inorganic composition and structure and the peptide template in solution. Catalytic loading and turnover frequency analyses demonstrated that these two characteristics worked in combination to control the reactivity of the materials. From this analysis, the spherical nanoparticles and NPNs demonstrated higher reactivity as compared to the 1-dimensional nanoribbons for all of the selected catalytic reactions. This unique reactivity trend is likely to be dependent upon two factors: the metallic surface area and the reagent penetration depth within the peptide scaffold. Such results could prove to be critical for future research for the fabrication of nanocatalysts where the composite/stabilizing structure mediates the reactivity of the materials. Also, these materials provide a green and effective route for catalyzing C-C coupling as well as direct surface reactions with high efficiency, complying with energy demands that are likely to be highly important for the future generation energy-efficient catalysis.
5:00 PM - OO3.5
Crystallographic Recognition Controls Peptide Binding and Activity for Bio-based Nanomaterials
Chemistry, University of Miami, Coral Gables, Florida, USA; 2,
, Air Force Research Labs, Wright-Patterson Air Force Base, Ohio, USA; 3,
Physics, Yeshiva University, New York, New York, USA; 4,
Polymer Engineering, University of Akron, Akron, Ohio, USA.Show Abstract
Peptides have been isolated with the ability to specifically bind inorganic materials to generate nanoparticle-based systems; however, the binding mechanism by which these peptides recognize and bind with the nanostructures at high affinity is still relatively unknown. By understanding this level of chemical interactions, nanoparticles could be designed that optimize both size and surface availability for a variety of applications ranging from catalysis to biomedical sensing. Furthermore, such systems are envisioned to operate under environmentally friendly and energy efficient conditions and may address issues related to future energy concerns. To probe this effect, we have isolated the Pd4 peptide, which is able to generate nearly monodisperse Pd nanocatalysts and have begun to explore its specific surface binding effects. To explore this phenomenon, we have selectively altered the binding capability through histidine residue substitutions in the peptide sequence. Catalytic analysis of the generated nanoparticles demonstrated a direct correlation between the reactivity and the peptide sequence, which suggests that the biotic/abiotic interface plays a critical role in the overall materialâ€™s functionality. Furthermore, by modifying the Pd:peptide ratio employed during materials synthesis, we have observed size control via the actual peptide sequence, which is in direct contrast with typical ligand-based nanoparticle preparation routes. Together, this suggests that peptides can recognize the crystalstructure of the material and bind once such inorganic structural features are present in the reaction mixture. These results are significant as they begin to demonstrate mechanistic understandings of these biologically influence interactions, which could lead to progress toward the ability to design highly specific biotic-abiotic interfaces at the atomic level with structural control of complex inorganic materials that could be immediately employed in a vast array of technologically important applications.
5:00 PM - OO3.6
Nano-pipette Directed Motion of Biomimetic Transmembrane Channel
Chemical and Biochemical Enginering, Rutgers University, Piscataway, New Jersey, USA; 2,
Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.Show Abstract
Via Dissipative Particle Dynamics (DPD) approach, we study the directed motion of a transmembrane end-functionalized nanotube using a suitably functionalized nano-pipette. In our earlier work (Nanoscale 2011), we demonstrated the design and creation of biomaterials which promote controlled release by integrating end-functionalized nanotubes into lipid bilayers. Each nanotube encompasses an ABA architecture, with a hydrophobic shaft (B) and two hydrophilic ends (A). To allow controlled transport through the nanotube, we also introduce hydrophilic tethers at one end of the tube. We showed that nanotubes initially located in the outer solvent spontaneously penetrate the membrane and assume a trans-membrane position, with the hydrophilic tethers extending from the surface of the bilayer. The hydrophilic tethers can also serve as anchors for directing the motion of the inserted nanotube across the membrane. We demonstrate this process by locating a suitably functionalized nano-pipette near such an end-functionalized nanotube. The nanotube diffuses in the membrane until the tethers are close to the nano-pipette. Due to favorable interactions, the tethers anchor onto the nano-pipette. We also show that the nanotube motion can be controlled through the nano-pipette.
5:00 PM - OO3.7
Probing the Limits of Aptamer Affinity with a Microfluidic SELEX Platform
Ahmad1, Seung Soo
Xiao2 5, H. Tom
Soh1 2 5.
Biomolecular Science and Engineering, University of California, Santa Barbara, Santa Barbara, California, USA; 2,
Materials, University of California, Santa Barbara, Santa Barbara, California, USA; 3,
Electrical and Computer Engineering, University of California, Santa Barbara, Santa Barbara, California, USA; 4,
Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California, USA; 5,
Mechanical Engineering, University of California, Santa Barbara, Santa Barbara, California, USA.Show Abstract
Nucleic acid-based aptamers offer many potential advantages relative to antibodies and other protein-based affinity reagents, including facile chemical synthesis, reversible folding, improved thermal stability and lower cost. However, their selection requires significant time and resources and selections often fail to yield molecules with affinities sufficient for molecular diagnostics or therapeutics. Towards a selection technique that can efficiently and reproducibly generate high performance aptamers, we developed a microfluidic selection process (M-SELEX) that can be used to obtain high affinity aptamers against diverse protein targets. Here, we isolated DNA aptamers against three protein targets with different isoelectric points (pI) using a common protocol. After only three rounds of selection, we discovered novel aptamer sequences that bind to platelet derived growth factor B (PDGF-BB; pI = 9.3) and thrombin (pI = 8.3) with respective dissociation constants (Kd) of 0.028 nM and 0.33 nM which are both superior to previously reported aptamers against these targets. In parallel, we discovered a new aptamer that binds to apolipoprotein E3 (ApoE; pI = 5.3) with a Kd of 3.1 nM. Furthermore, we observe that the net protein charge may exert influence on the affinity of the selected aptamers. To further explore this relationship, we performed selections against PDGF-BB under different pH conditions using the same selection protocol, and report an inverse correlation between protein charge and aptamer Kd.
5:00 PM - OO3.8
Collisional Quenching-based Fluorescence Glucose Sensing Using Enzyme-immobilized ZnO Nanocrystals
Materials Sci. & Eng., Korea University, Seoul, Republic of Korea.Show Abstract
As an alternative to electrochemical sensing, many researchers are exploring fluorescent methods for biological sensing. Fluorescence sensing relies on the interaction between fluorophores and analytes that causes the change in the optical signals of fluorophores. The use of fluorescent indicators can provide sensitive and selective detection in liquid media which has led to widespread use in biological analysis. Currently, organic fluorophores have been replaced with inorganic semiconductor and metal nanoparticles, especially quantum dots, because of their high resistance to photo-bleaching and intense light emission by high quantum efficiency. Also, tuning the color of light emission can be achieved simply by changing the particle size due to quantum confinement effect. However, fluorescent glucose biosensors based on quantum dots are highly limited. In this study a simple approach to sensitive glucose detection has been developed based upon variation in the fluorescence of ZnO nanocrystals with glucose concentration. ZnO nanocrystals were successfully synthesized in wurtzite structure using a surfactant, mercaptoundecanoic acid (MUA) via the polyol method. MUA molecules not only served as a template for the synthesis of spherical-shape nanoparticles but also provided water solubility and biocompatibility due to its carboxyl group. Carboxyl-terminated ZnO nanocrystals were activated by esterification of n-hydroxysulfo-succinimide (Sulfo-NHS) catalyzed by water-soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Glucose oxidase (GOx), an enzyme could be immobilized to ZnO nanocrystals by replacing NHS with amino-acid groups of GOx. ZnO-MUA-GOx bioconjugates showed decrease in the photoluminescence (PL) intensity by appearance of glucose molecules due to the collisional quenching by hydrogen peroxide generated from enzymatic oxidation reaction of glucose. PL intensity showed linear decrease with glucose concentration from 1.6 to 33.3 mM, which fully covers physiological glucose level. ZnO-MUA-GOx bioconjugates showed detection limit lower than 0.33 mM and response time less than 5 sec. They also revealed distinct specificity against cholesterol molecules.
5:00 PM - OO3.9
Combination Self-assembly of β-sheet Peptides and CNT: Functionalizing CNT with Bioactive β-sheet Block Copolypeptides
Materials Science and Engineering, Yonsei University, Seoul, Republic of Korea.Show Abstract
Carbon nanotubes are intrinsically insoluble in aqueous solution. Since biological systems are composed of water-soluble structures, the solubilization of CNTs in aqueous solution is a prerequisite for their use in bioapplications. In addition, surface functionalization of CNTs with biologically active molecules is important to give them specific biological functions. The two main approaches for the solubilization of CNTs are based on covalent and noncovalent functionalization. In covalent functionalization, functional groups such as carboxylic acids or amines are formed by chemical reactions in defect sites of CNTs, which can then be used as sites for conjugation reactions with bioactive molecules. The problem with this approach is that it can damage the intrinsic structural and electrical properties of pristine CNTs. By contrast, the noncovalent approach can potentially preserve the Ï€-conjugated system of CNTs. This approach usually uses amphiphilic molecules, in which the hydrophobic part of the molecule wraps around the wall of CNTs, and the hydrophilic part interacts with an aqueous solution. Various types of molecules including low molecular weight amphiphiles or surfactants, polymers, carbohydrates, DNAs or RNAs, proteins, and peptides, have been used to noncovalently functionalize and solubilize CNTs. Peptides(the minimal form of proteins) can be developed as protein-like artificial nanomaterials when properly designed and self-assembled into controllable and elaborate nanostructures. It has recently been demonstrated that self-assembled peptide nanostructures based on Î²-sheet peptides can be developed as promising biomaterials. Notably, self-assembling Î²-sheet peptides can be functionalized to become bioactive nanostructures when a biologically active and hydrophilic peptide segment is conjugated to the Î²-sheet segment, yielding bioactive Î²-sheet block copolypeptides. In doing so, diverse types of controlled and biologically useful Î²-sheet peptide nanostructures could be fabricated. Herein, we present systematic investigation of the combination self-assembly between the bioactive Î²-sheet block copolypeptides and CNTs. This type of self-assembly system includes force balance processes between two classes of completing forces: the attractive forces between Î²-sheet segments, and the attractive forces between Î²-sheet segments and CNTs. If the former predominates, the peptides construct Î²-sheet nanostructures while CNTs are still insoluble. On the other hand, water-soluble CNTs noncovalently functionalized with the bioactive Î²-sheet block copolypeptides can be constructed if the latter becomes dominant. This research is important in fabricating peptide-decorated bioactive and functional CNTs. Moreover, understanding such force balance processes is valuable for controlling and thereby inhibiting aggregation behavior of Î²-amyloids and related proteins in protein misfolding diseases.
5:00 PM - OO3.10
Rationally-designed Novel Self-assembling Peptide Building Blocks: Cyclic Peptide Ampiphiles
Material Sceince and Engineering, Yonsei University, Seoul, Republic of Korea.Show Abstract
Self-assembled peptides have been well known as promising biomaterials and functionalizable nanomaterials. Peptides, as principle components of natural proteins, have the advantages such as biocompativity and specific structures by their sequences. Peptides have mostly been designed to have linear molecular configuration, like a single strand long chain. Peptide chains have played a role in self-assembly of peptide nanostructures. For the purpose of the control of self-assembly processes and structures, novel peptide building blocks are different from traditional linear configuration and expected to build up another nanostructures. Cyclic peptides are one of the self-assembly building blocks that have unique morphological features and more constrained property than linear peptides. Another useful building block for self-assembly is the amphiphile molecules. Conventional amphiphile molecules are possessing both hydrophilic and hydrophobic parts on two ends of molecules. In contrast, the hydrophobic and hydrophilic groups are located on two opposite faces in facial amphiphiles. We suggest novel self-assembly building block in which the these cyclic and facial properties are combined. Here, we have designed, synthesized, and investigated the structures and characteristics of the novel and functionalized self-assembling cyclic amphiphile peptides. This approach shows the characteristic nanostructure formations. These special structures have hollow spaces in the core site and it should be useful for the intracellular delivery system.
5:00 PM - OO3.11
In vitro Selection of Binding-activated Transducers for Selective Capture and Release of Molecules
Plakos1 2, Yi
Xiao1 2, H. Tom
Materials Department, University of California-Santa Barbara, Santa Barbara, California, USA; 2,
Department of Mechanical Engineering, University of California-Santa Barbara, Santa Barbara, California, USA.Show Abstract
The availability of molecules that can perform complex functions triggered by target binding would impact many important areas in biotechnology including targeted drug delivery, in vivo imaging, and in vitro molecular diagnostics. However, the use of directed evolution methods to generate such Binding-Activated Transducer (BAT) molecules has proven to be a significant challenge because the desired molecular function must be directly linked to the selection strategy. As a first step, we have previously reported a microfluidic selection strategy that can generate DNA aptamers that undergo large conformational changes upon binding to a protein target (S. S. Oh et. al., PNAS 2010). In this work, we report a significant advancement in the selection of BAT molecules wherein a small â€œtriggeringâ€ molecule (ATP, adenosine triphosphate) can activate a number of molecular functions of the transducer including 1) the release of a specific DNA sequence, 2) the release of a â€œcargoâ€ molecule (ATMND, 5,6,7-trimethyl-1,8-naphthyridin-2-ylamine) and 3) the capture of a â€œtargetâ€ molecule (NMM, N-methyl mesoporphyrin IX). To isolate these BAT molecules, we first designed a DNA library that incorporates both the pocket sequence to hold the cargo molecule as well as the inactivated DNAzyme sequence that capture the target molecule. We then performed microfluidic selections, which efficiently isolate the BAT molecules for the aforementioned functions. After 10 rounds of selection, we identified 3 DNA sequences that exhibit high affinity to ATP (Kd = ~20 Î¼M). Importantly, we confirmed that these BAT molecules, upon binding to ATP, indeed transduce the release of ATMND and the capture of NMM through fluorescence measurements.
5:00 PM - OO3.12
Profiling and Characterization of Silver, Zinc Oxide and Silver/ Zinc Oxide Hybrid Nanoparticles for Antimicrobial and Antifungal Properties
Myisha Roberson1, Clayton
Materials Science and Engineering, Tuskegee University, Tuskegee, Alabama, USA.Show Abstract
Bio-compatible surface modified nanomaterials are known to be less cytotoxic to cells and more effective in therapies at lower dosages. Nanoparticles such as iron oxide, silver, gold and zinc oxide, etc are well known in the literature as minimum to non-toxic materials for healthy cells. They can be used as therapeutic drug, or drug carrier systems. In this study we have synthesized the ZnO, Ag and ZnO/Ag hybrid nanoparticles using microwave synthesis method and tested for their wound healing properties. These nanoparticles are susceptible to infection, induces cellular proliferation, increases skin penetration rate and cellular migration that allow the wound healing process to proceed toward a more regenerative pathway. The as-synthesized nanoparticles were characterized using X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) techniques to study the crystalline structure, composition, particle size, morphology and purity. Standard disk diffusion assays were used to study the antibacterial and/or antifungal properties of as prepared nanoparticles. Results shows that the Ag, ZnO and ZnO/Ag nanoparticles have antifungal and antimicrobial properties that potentially decrease susceptibility of a fungal or bacterial infection in a healing wound at minimum concentration of 50 Âµg/mL. Key words: Ag/ZnO hybrid nanoparticles, antimicrobial, antifungal, wound healing
5:00 PM - OO3.13
Microtubule Mimicry: Toward Biomolecular Self-assembly in Synthetic Materials
, Sandia National Labs, Albuquerque, New Mexico, USA.Show Abstract
Microtubules (MTs) are dynamic supramolecular protein nanofibers that facilitate and direct a host of complex biological processes in cells ranging from chromosome separation during cell division to regulating cellular morphology and the trafficking of intracellular cargo. Creating synthetic analogs to MTs would present opportunities for advanced nanomaterials assembly and adaptable materials development. But creating these analogs requires a detailed understanding of the principles governing MT form and function. In this presentation, I will describe the use of wedge-shaped peptide dendrimers, designed to mimic key characteristics of a microtubuleâ€™s natural tubulin building blocks. Guided by molecular dynamics simulations, these dendrimers contain characteristics such as electrostatic charge, hydrogen bonding, and amphiphilicity. By synthetically tuning these variables, we aim to reproduce characteristic influences on tubulin assembly including balance of lateral and vertical interactions of tubulin, molecular asymmetry, and supramolecular programmability. This supramolecular platform is a powerful tool for study of the critical factors that may lead to synthetic materials with the diverse, dynamic, and adaptable functions seen in natural microtubule systems. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
5:00 PM - OO3.15
Hybrid Configurations of Lipid Membranes with Plasmonic Nanoparticle Arrays
Physics, LMU Munich, Munich, Germany.Show Abstract
Bilayers of phospholipid molecules display a high level of lateral mobility while covering the underlying substrate. Due to these unmatched characteristics, supported membranes feature unique capabilities to mimic biological surfaces and dynamic cellular processes that involve lateral mobility and movement of receptors. Noble metal nanoparticles and nanostructures on the other hand can impose obstacles to the mobility of molecules in this otherwise fluid environment. These particles furthermore exhibit extraordinary optical properties that offer a broad range of useful applications for plasmonic sensing and spectroscopy if they are properly harnessed. We demonstrate the fabrication and characterization of large-scale hybrid nanoparticle/supported membrane configurations that are built up by immobile arrays of plasmonic nanoparticles and nanoantennas embedded within a fluid supported membrane. Merely bottom-up nanofabrication methods are employed to control the size and spacing of billions of gold particles and triangles on one single substrate with nanometer precision. Subsequently, a supported membrane is assembled over the bare substrate in between the nanopattern. Fluorescently labeled ligands can be bound to the fluid lipid component, the nanoparticle component, or both, providing a hybrid configuration consisting of mobile and immobile ligand molecules with controlled geometry. Finally, we discuss how the intriguing properties of this innovative hybrid biomaterial platform can be used for sensing applications and surface-enhanced Raman spectroscopy.
5:00 PM - OO3.17
Manufacturing Anisotropic Eco-capsules and Its Assembly
MSE, Gatech, Atlanta, Georgia, USA.Show Abstract
Anisotropic capsules based on sodium chloride cubic cores were synthesized by layer-by-layer (LbL) assembly of the hydrogen-bonded polymers from the anhydrous alcohol solutions. A nonhazardous core release by water has been used. The overall thickness of these LbL shells with four bilayers is within 20 nm in dry state which is twice higher than for the LbL shells produced from the aqueous solutions. The cubic capsules as was observed mainly forms the highly compacted 3D cubic arrays due to the face to face interactions and steric confinements in sharp contrast to the assembly built by the spherical capsules for which the hexagonal packing is generally favored. The assembled spherical microcapsules create a large number of openings with extensive surface areas while the cubic microcapsules build close, compact aggregates. Thus the porosity of the cubic microcapsules assembly is mainly caused by the nano-porous shells which can be tuned by solvent composition (dielectical constant, pH).
5:00 PM - OO3.18
Apatite Coating on Hydroxyapatite/Collagen Nanocomposite Membrane for Surface Functionalization
Biomaterials Unit, Nano-Bio Field, International Center for Materials Nanoarchitechtonics (MANA), National Institute for Materials Science, Tsukuba, Ibaraki, Japan; 2,
Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan; 3,
Human Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan; 4,
Department of Neurosurgery, Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan.Show Abstract
The development of biomaterials applicable to tissue engineering technology has recently focused on the surface functionalization that can promote tissue regeneration. A biomimetic apatite coating is an effective technique for surface functionalization of biomaterials, since apatite can be incorporated with biomolecules including plasmid DNA and growth factors (BMP-2, FGF-2). The objective of our research is to develop an efficient coating technique for hydroxyapatite and collagen (HAp/Col) nanocomposites. The HAp/Col nanocomposites have the potential as bone substitutes due to their similar composition, nanostructure, and biological properties to those of human bone . The HAp/Col nanocomposites membrane samples were synthesized by the simultaneous titration method using Ca(OH)2, type-I atelocollagen and H3PO4 as starting precursor materials . Two different coating solutions, so-called CP solution  and RKB solution  have been investigated to deposit an apatite layer on the sample surface. The CP solution (NaCl 142 mM, CaCl2 3.75 mM, K2HPO4.3H2O 1.50 mM, buffered to pH=7.40 at 25 oC) was prepared using reagent grade chemicals . The sample was immersed in 3 ml of the CP solution at 25 oC for 24 hours after precoating with amorphous calcium phosphate (ACP) by three times alternate dipping into CaCl2 and K2HPO4.3H2O solutions . The RKB solution was prepared by mixing clinically available infusion fluids; Ringerâ€™s solution (calcium solution), Klinisalz B (phosphate solution), and Bifil (alkalinizer) .The sample was immersed in 2 ml of the RKB solution at 37oC for 2 days. After coating in the CP solution, no apatite deposition was found on the sample surface as confirmed by scanning electron microscopy (SEM). A bioresorbable and highly unstable HAp/Col surface might inhibit the heterogeneous nucleation of apatite at the sample surface. In contrast, after coating in the RKB solution, micro-sized particles of apatite were deposited on the sample surface. It is considered that apatite particles were first formed in the RKB solution by homogeneous nucleation, grew into larger particles, and then deposited on the sample surface. It was found that apatite coating technique using the RKB solution was effective for the HAp/Col nanocomposites, whereas that using the CP solution was not. Functionalization of HAp/Col nanocomposites would be possible by using the RKB solution supplemented with biomolecules. References:  Kikuchi et al., Biomaterials 2001; 22: 1705-11.  Oyane et al., Acta Biomater. 2011; 7: 2969-76.  Mutsuzaki et al., J. Biomed. Mater Res. B 2008; 86B: 365-74. Acknowledgements: Authors would like to acknowledge the financial support from Japan Society for the Promotion of Science (JSPS)postdoctoral fellowship.
5:00 PM - OO3.19
Building of Hierarchical Zinc Oxide Nanostructures on a Biological Template
Materials Science and Engineering Program, University of California-Riverside, Riverside, California, USA; 2,
Department of Bioengineering, University of California-Riverside, Riverside, California, USA; 3,
Department of Electrical Engineering, University of California-Riverside, Riverside, California, USA.Show Abstract
ZnO is a direct, wide-bandgap semiconductor which has proven useful for many electronic and optoelectronic applications in both bulk and nanocrystalline forms. Bio-directed synthesis of ZnO is a promising technique capable of morphological control under generally mild, low temperature conditions. Several ZnO-binding peptides have been reported, and a few have been further investigated for biomineralization purposes [1-3]. Such studies have focused on free peptides or peptides arranged on a planar surface. Here we report the biomineralization of ZnO on an M13 bacteriophage template. The highly ordered viral protein coat acts as a three-dimensional scaffold for the ZnO-binding peptides producing a hierarchical structure unavailable to isolated peptides in solution. The added organization of the template dictates the size, shape, and morphology of the resulting semiconductor material. A reported peptide sequence (EAHVMHKVAPRP) with a high affinity for ZnO was used to biomineralize ZnO using a Zn(OH)2 precursor solution . To explore cooperative effects caused by proximity and ordering during nucleation and growth, the peptide was fused to either the M13 minor coat protein or the M13 major coat protein using genetic modification or a sulfo-SMCC conjugation, respectively. The 3-5 copies of the minor coat protein located at the tip of the virus are highly flexible and possess only minimal long range organization. In contrast, the 2700 copies of the major coat protein located along the length of the virus have significant long range order. Transmission electron microscopy was used to examine the nanocrystal size and size distribution, geometry, morphology, and crystalline structure of the mineralized material. Further investigation of the crystal structure and material composition was completed with x-ray diffraction and energy dispersive x-ray spectroscopy. The optical properties of the bio-templated nanocrystalline ZnO were characterized using photoluminescence and absorption measurements. The relative intensities of the band edge and defect emission peaks were evaluated, as well as the width of the band edge emission peak. The hierarchical structure created by the viral template controls both the structure and properties of the resulting ZnO nanomaterials.  M. Umetsu, et. al., Adv. Mater. (2005) 17, 2571-2575;  M. M. Tomczak, et. al., Acta Biomater. (2009) 5, 876-882;  Z. Huang et. al., J. Colloid. Interf. Sci. (2008) 325, 356-362
5:00 PM - OO3.20
Nanoparticle Biotemplating at Two Distinct Epitope Sites at a Protein Interface
Materials Science and Engineering, Stanford University, Stanford, California, USA.Show Abstract
Biotemplating is a unique synthetic route that provides an attractive â€œgreenâ€ strategy for the potential manufacture of nanomaterials for electronic devices and energy technologies. Protein scaffolds, in particular, offer an infinite number of structural scaffolds with multiple exposed sites that can interact with the inorganic material. However, most protein biotemplates involve chemical or genetic modifications to the protein interface in order to interact with the inorganic material of interest. To extend the flexibility of protein biotemplates, we have established a unique biotemplating strategy that allowed us to successfully functionalize protein assemblies to template inorganic material using site-specific, non-covalent interactions without chemical or genetic modifications. The protein used in our study, clathrin, is a self-assembling intracellular protein that plays a major role in the transportation of cargo across the plasma membrane. Clathrin has proven to be a flexible biotemplate, forming stable assemblies in vitro that are analogous to in vivo 2D hexagonal lattice and 3D cage structures. Our previous studies have incorporated the â€œclathrin-boxâ€ or "C-box" epitope sequence into the design of bi-functional peptides in order to mimic the non-covalent, heterogeneous protein-protein interactions that occur in vivo between adaptor proteins and clathrin. The bi-functional peptides combine the C-box recognition sequence upstream of inorganic-binding sequences, creating a molecular link between the clathrin protein interface and inorganic material. This strategy has been named Template Engineering Through Epitope Recognition, or TEThER, and facilitates a variety of inorganic materials to interface with the clathrin protein without modifying the protein assembly. The success of this strategy was previously illustrated through the biotemplated synthesis of three different inorganic particles: titanium dioxide, cobalt oxide, and gold. In the current study, we prove the flexibility of the TEThER strategy by introducing the use of a second, distinct epitope site on clathrin, the "W-box". The W-box epitope binds a conserved tryptophan-rich region of select adaptor proteins and is located a site distinct from the C-box. We illustrate the versatility of our protein biotemplate by synthesizing gold and titanium dioxide nanoparticles using the distinct W-box epitope site. We also extend the use of the TEThER strategy to demonstrate successful synthesis of platinum nanoparticles using either the C-box or W-box epitopes. These experimental results present the possibility of future heterogeneous nucleation of multiple inorganic materials on a single protein biotemplate with site-specificity for each inorganic species. We conclude that the TEThER strategy is a versatile and modular platform for biotemplating reactions.
5:00 PM - OO3.21
Antimicrobial Properties of a Zinc - Releasing Bioceramic
Materials Science and Engineering, State University of New York- Stony Brook, Stony Brook, New York, USA; 2,
Plant Pathology and Plant-Microbe Biology, Cornell University-NYSAES, Geneva, New York, USA; 3,
Chemical and Molecular Engineering, State University of New York- Stony Brook, Stony Brook, New York, USA.Show Abstract
Up to 80% of nosocomial infections are caused by biofilm-producing bacteria such as Staphylococci and Pseudomonas aeruginosa. These types of microorganisms can become resistant to antibiotics and are difficult to eliminate. As such, there is tremendous interest in developing bioactive implant materials that can help to minimize these post-operative infections. Using water-based chemistry, we developed an economical, biodegradable and biocompatible orthopaedic implant material consisting of zinc-doped hydroxyapatite (HA), which mimics the main inorganic component of the bone. Because the crystallinity of HA is typically too compact for efficient drug release, we substituted calcium ions in HA with zinc during the synthesis step to perturb the crystal structure. An added benefit is that zinc itself is a microelement of the human body with anti-inflammatory property, and we hypothesized that Zn-doped HA is an inherently antibacterial material. All HA samples were synthesized by a co-precipitation method using aqueous solutions of Zinc nitrate, Calcium Nitrate, and Ammonium Phosphate. SEM/EDS and XRD data showed that Zn was successfully incorporated into the HA. The effectiveness of Zn-doped HA against a model biofilm-forming bacterium is currently being evaluated using a wild-type strain and a streptomycin-resistant strain of Pseudomonas syringae pv. papulans (Psp) which is a plant pathogen isolated from diseased apples.
5:00 PM - OO3.22
Temperature-responsive Hydrogels with Improved Swelling and In Situ Crosslinking for Aneurysm Embolization
Bioengineering, Arizona State University, Tempe, Arizona, USA.Show Abstract
Introduction: Rupture of intracranial aneurysms is a devastating and potentially lethal health event, and current techniques for filling these aneurysms lead to high recurrence. A promising alternative is the use of liquid materials which can be injected and then become solid within minutes, blocking blood flow into the aneurysm. Smart materials such as copolymers of N-isopropylacrylamide (NIPAAm) may be useful for embolization due to their lower critical solution temperature (LCST) in water, forming a physical gel when heated above the LCST (~ 30Â°C). However, purely physical gels of poly(NIPAAm) are prone to deswelling and creep. Here, we report on an improved copolymer system for embolization which crosslinks by in situ reaction above the LCST and transitions from liquid to solid with almost no volume change. The material is a copolymer of NIPAAm, Jeffamine M-1000 acrylamide (to control gel swelling), and cysteamine-acrylamide bearing thiol groups. When mixed in aqueous solution with poly(ethylene glycol) diacrylate (PEGDA), the polymer system crosslinks by Michael-type addition, resulting in an elastic dual physical-chemical gel. Methods: Copolymers were synthesized and then characterized using NMR (composition), HPLC (molecular weight), and cloud point determination (LCST). The copolymer systems (copolymers + PEGDA) were characterized by rheometry, a gel swelling study, a catheter injectability test, and in glass aneurysm flow models. Results and Discussion: The polymers were synthesized with slightly lower JAAm content than feed. The polymers, 0, 10, and 20 % JAAm had LCST all between 28-33Â°C and Mn~10 kDa. Swelling increased with JAAm content. Greater JAAm inclusion showed faster decrease in phase angle after mixing with PEGDA, lower phase angles, and shear moduli which were less sensitive to frequency. All of these indicate that crosslinking is faster and more complete in gels containing JAAm. JAAm-containing polymers were injectable through a warm microcatheter for over 3 minutes while those without JAAm were not injectable after 30 seconds. Gels with JAAm, however, were too weak to remain in glass aneurysm models under high flow conditions (80 mL/sec) for more than 1 hr. Conclusions: A desirable LCST (below body temperature) was obtained for all polymers. JAAm content of 16 wt% provided gels that retain their volume adequately for embolization and are injectable for a longer time post-mixing. Gels with JAAm are initially weaker, but are highly elastic and of similar modulus after crosslinking. Higher molecular weight polymers of similar composition will be synthesized in future work to provide increased modulus while preserving the deliverability, swelling control, and elasticity observed in this class of materials.
5:00 PM - OO3.23
Colorimetric Detection of Microcystin-LR Using Peptide-derived Au Nanoparticles
, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, USA.Show Abstract
The need for simple, specific detection of water-borne contaminates is an ever growing concern given the diverse chemical nature of water pollutants derived from various industrial, domestic and biologically sources. Microcystin-LR (MC-LR) is a cyanobacteria toxin commonly found in fresh water sources containing algae blooms which can produce MC-LR at dangerous concentrations. In this study, Au nanoparticles are created using fusion peptides containing sequences for Au ion precipitation and MC-LR binding. As MC-LR is introduced to the Au nanoparticle solution, the MC-LR binds in close proximity to the Au nanoparticles, causing a colorimetric change. Due to the specificity of the peptide for MC-LR, this colorimetric sensor only changes color in the presence of MC-LR and not in the presences of similar toxins.
5:00 PM - OO3.24
The Effects of CTAB on Single-stranded DNA Binding to Gold Nanorods
Materials Science & Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA; 2,
Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA.Show Abstract
Cetyltrimethylammonium bromide (CTAB) surfactant is commonly used to mediate the growth of gold nanorods (AuNRs) from spherical gold nanoparticle seeds. We have synthesized uniform AuNRs with an aspect ratio of 3 to 4 using a seeded growth method. While the presence of CTAB appears crucial to the anisotropic growth of AuNR from spherical seeds, UV-Vis and FTIR spectroscopy studies indicate that CTAB is only weakly bound to the AuNR surface. As CTAB is removed through multiple washing steps, the AuNRs visibly aggregate. Interestingly, aggregated AuNR suspensions were at least partially restabilized if CTAB was reintroduced to the suspension. Here, we explore the effects of adding a random library of 69 base long single-stranded DNA sequences to the growth solution in both the presence and absence of CTAB to study the effects of biological macromolecules on the size and shape of resulting gold nanoparticles. The resulting gold nanoparticles were characterized using spectroscopy as well as TEM and dynamic light scattering.
5:00 PM - OO3.25
Multifunctional Antioxidant Rare Earth Nanoparticles: Targeting, Delivery and Protection of Neuronal Cells in Alzheimer Model
Kumar1 2 3, Soumen
Das1 2 3, Annamaria
Seal1 2 3.
Mechanical Materials and Aerospace Engineering, University of Central Florida, Orlando, Florida, USA; 2,
Nanoscience Technology Centre Center, University of Central Florida, Orlando, Florida, USA; 3,
Advanced Materials Processing and Analysis Centre, University of Central Florida, Orlando, Florida, USA; 4,
Department of Basic and Applied Biology, University of L'Aquila, L'Aquila, Italy; 5,
Physics Department, University of L'Aquila, L'Aquila, Italy.Show Abstract
Oxidative stress and Î²-amyloid are considered as major pathological factors in the Alzheimer disease. Therefore, selected delivery of drug and/or antioxidant to the affected area (Î²-amyloid plaque) may stop the disease progression. Antibody conjugated nanoparticles have been researched for detection, identification, imaging and targeting. However, there is always a concern of proper antibody orientation, restricted interaction due to the steric hindrance and fast clearance from the biological system. Herein we report a systematic design of nanoparticle conjugated with antibody for selected targeting. For this purpose Anti-Î²-amyloid antibody was conjugated with oxide nanoparticle (cerium oxide nanoparticles; CNPs), which is a novel regenerative antioxidant nanoparticles, for targeting plaque in an in-vitro Alzheimer model. To reduce the steric hindrance between the antibody and targeted ligand, poly-ethylene glycol (PEG) spacer of 18.1Ã… was used. First â€“NH2 functionalized nanoparticle were synthesized and PEG were attached. Single force microscopy was used to confirm the stealth effect of PEG coated CNPs. Surface charge of nanoparticle coated with PEG was used to properly orient the antibody and then conjugated using EDC/Sulfo-NHS chemistry. Enhanced targeting and increased bio-compatibility were observed in case of CNP-PEG-Ab as compared to CNP-Ab. Moreover, preservation of neural structure was observed by modulating the BDNF signaling pathway in in-vitro Alzheimer model using this novel Ab conjugated antioxidant nanoparticle.
5:00 PM - OO3.26
Colorimetric Protein Detection: Plasmonic Shift via DNA-Au Nanoparticle Flocculation based on Chemically Engineered DNA-M13 Bacteriophage Platform
Nanoengineering, University of California, San Diego, La Jolla, California, USA.Show Abstract
For early-stage disease diagnosis, advanced biomarker detection systems are highly critical. In addition, the sensors need to be convenient to run, reliable and low-cost to have global applicability. Previously, we demonstrated a biosensor system based on chemically modified thiolated M-13 bacteriophage that could induce rapid color changes after mixing with metal nanocrystals due to the plasmon shifts in direct response to antigens in solution. Some of the major benefits of using M13 bacteriophage platforms were that these bioscaffolds are easy to replicate, are stable in most environments as compared to enzymes, have the inherent ability to recognize other biomolecules and possesses over 2700 major coat proteins which can serve as modes to generate amplified signals. In most diseases including cancer however, multiplexed detection of various proteins is needed. To meet this challenge, we demonstrate here our recent efforts on using DNA modified bacteriophage to generate amplified colorimetric changes in solution. We modified the major capsid protein of M13 bacteriophage with DNA using amine-succinimidyl ester and thiol-maleimide chemistry. The DNA conjugated phage were reacted with various antigens in solution and captured magnetically using iron oxide beads. The bound DNA-M13 bacteriophage were then released into solution by chemical denaturation and then detected by adding DNA-conjugated metal nanocrystals to generate colorimetric changes in solution. These strategies are being explored for multiplexed protein detection in solution by reading the specific DNA conjugated to the nanoparticles or to the phage.
5:00 PM - OO3.27
Peptidomimetic Element for Controlling Polymer Brush Grafting Density, Protein Adsorption and Cell Attachment
K. H. Aaron
Lau1 2, Jinghao
Kuang1 2, Kevin
Biomedical Engineering, Northwestern University, Evanston, Illinois, USA; 2,
Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA.Show Abstract
Efficient control of the surface density of biofunctional molecules is non-trivial. Strategies developed for one substrate or biomolecule often prove to be ineffective with other materials due to subtle changes in substrate chemistry. The surface concentrations of co-deposited molecules often do not match the ratio in the source material. We previously introduced a mussel adhesive-inspired oligopeptide for surface grafting of antifouling polypeptoid brushes. We now demonstrate the versatility of this peptidomimetic element for controlling the surface grafting density of different polymer brushes with a range of chain lengths. Both electrostatically neutral species and those with charged sidechains are investigated. Colloid probe AFM is used to characterize the pH, ionic strength and surface density responses of the charged polymer brushes. We show how the ability to control the surface chain density enables the control of adsorbed protein density, and the relationship between protein density and cell attachment is investigated.
5:00 PM - OO3.28
Immobilization of Nanoparticles onto Carbon Nanotubes Based on Affinity Binding Peptides
Shimada1 2, Mitsuo
Umetsu2 3, Takuma
Chikamoto2 4, Mizuaki
Sugiyama2 5, Hiroyuki
Institute of Industrial Science, The University of Tokyo, Tokyo, Japan; 2,
3D BEANS Center, BEANS Project, Tokyo, Japan; 3,
Graduate School of Engineering, Tohoku University, Sendai, Japan; 4,
, Seiko Instruments Inc., Tokyo, Japan; 5,
Institute of Engineering Innovation, The University of Tokyo, Tokyo, Japan.Show Abstract
Carbon nanotube (CNT) is an attractive material possessing unique electrical and mechanical properties. Such properties of CNTs hold great promise for development of nano-electronic devices, such as FET, flexible electrode and electrical wiring. Especially, functionalization of the CNT surface by nanomaterials and enzymes is a key technique for the construction of a photoelectric conversion element and a high-sensitivity sensing device. Meanwhile, peptides with specific molecule recognition have a potential for the immobilization of nanomaterials on solid surfaces without special treatments or complicated processes. The functionalization process using peptides with specificity will open a way to high-valued CNTs device with nanomaterials. In this study, we screened the CNT binding peptides (CNTBPs) from peptide-displayed phage library system, and demonstrated the direct arrangement of CdSe nanoparticles onto the surface of CNTs using CNTBPs. We newly identified peptides with an affinity for single-walled (SW) or multi-walled CNT, corresponding to CNPBP1 [HMSHKQTRLSSG] or CNTBP2 [HMGLTKIHYSAL], respectively. The CNTBPs were chemically synthesized with a biotin molecule on Lysine residue at C-terminus via a glycine linker (CNTBP-[GGGSK]-biotin). To investigate the ability of the peptides for immobilization of nanomaterials onto CNT surface, we applied streptavidin-conjugated CdSe nanoparticles as a model compound, which possessed fluorescence, and introduced CNTBPs onto the CdSe surface via avidin-biotin bonding. The nanoparticles with CNTBPs were mixed to the CNT suspension in the buffer solution at room temperature. After removing unbound particles, the fluorescence from CdSe was detected on the suspension only in the case with CNTBP; in contrast, no luminescence was observed in the case without the peptide. Through TEM and SEM observation of the suspension, we found CdSe nanoparticles were bound and arrayed onto the CNT surface, and confirmed that the both of CNTBP1 and CNTBP2 could be used to functionalize SWCNT. Furthermore, we applied the peptide-assisted immobilization method to the bridge of SWCNTs between the tapered electrodes on Si, which was obtained through dielectrophoresis of CNTs. The device chip was soaked in the buffer containing CNTBP2 and CdSe nanoparticles, and then it was washed with ultrapure water and dried up by N2. In fluorescence microscope observation, the emission from CdSe was detected only in the position of CNTs, while no emission was found on either Al electrode or Si substrate. As evidenced here, the CNTBP has highly-selective binding capability against CNTs, and this simple one-pod-mixing process for the selective surface functionalization of CNTs has a widespread potential for the fabrication of high-sensitivity and high-selectivity sensors using CNT-based nanostructures.
5:00 PM - OO3.29
Electrostatically Driven Bio-Inspired Hierarchical Artificial Vascular Networks
, U.S. Army Research Laboratory, Aberdeen Proving Grounds, Maryland, USA.Show Abstract
Vascular networks provide a method to distribute fluid throughout a system. Artificial vascular materials with enhanced properties are being developed that could ultimately be integrated into systems reliant upon fluid transport while retaining their structural properties. An uninterrupted and controllable supply of liquid is optimal for many applications such as continual self-healing materials, in-situ delivery of optically index matched fluids, thermal management and drug delivery systems could benefit from a bio-inspired approach that combines complex network geometries with minimal processing parameters. Two such approaches are electrohydrodynamic viscous fingering (EHVF) and electrical treeing (ET), both harnessing an electrostatic approach to network growth. Viscous fingering (VF) is a phenomenon that occurs when a low viscosity liquid is forced through a high viscosity fluid or matrix. The flowing liquid will branch, or form fingers due to capillary and viscous forces. EHVF is a modification on viscous fingering in which a DC voltage (10-60 kV) is applied to the low viscosity conductive fluid and forced through a dielectric matrix material, inducing fingers with a reduction in size and an increased branching behavior. The ensuing patterns mimic those found in biology and geology. Observation of VF and EHVF requires Hele-Shaw conditions in which a 2D system must possess a thin gap or in a porous 3D system. In the 2D instance silicone oil or PDMS was used. The interfacial tension was reduced by optimizing the surfactant concentration, resulting in branched pattern of small diameter fingers. Various filler materials were used to represent a more 3D system. Matrix filling reduces finger relaxation and allows for curing. Interfacial polymerization was also investigated. Robust, polymerized, fingers were formed and subsequently filled showing fluid transport. In moving more toward a true 3D system, materials such as fumed silica and crushed glass were investigated under. ET is the result of partial discharges in a dielectric material. In the vicinity of a small diameter electrode, the local electric field is greater than the global dielectric strength, causing a local, step-wise, breakdown to occur forming a highly branched interconnected structure. ET growth is influenced by the geometric configuration of the electrodes. ET is a viable method to produce networks on a smaller, micron, scale than EHVF. Surface modified electrodes, by carbon nanotube deposition, aid in increasing the local field, enabling a higher rate of tree initiation and growth. Inclusion of particles was investigated to determine if the growth direction can be manipulated. The use of self-clearing electrodes was investigated by UV dye infiltration through the hollow channels. Fluid delivery can be tailored through the applications of different electrode and ground manufacturing techniques for optimized flow rates for a given application.