Symposium Organizers
Rajesh R. Naik Air Force Research Laboratory
Carole C. Perry Nottingham Trent University
Kiyotaka Shiba Japanese Foundation for Cancer Research
Rein Ulijn University of Manchester
T1: Bioinspired Materials
Session Chairs
Tuesday PM, April 10, 2007
Room 2006 (Moscone West)
9:00 AM - T1.1
Biogenic Nanostructured Silica Formation in Diatoms: Proteins, Genes, and Structure.
Mark Hildebrand 1
1 , Scripps Institution of Oceanography, UCSD, La Jolla, California, United States
Show AbstractDiatoms make cell walls containing three-dimensional nano- and micro- scale silica structures, with a complexity and organization exceeding that possible with current synthetic approaches. Diatom silica structure formation occurs dynamically inside an expandable and moldable membrane-bound intracellular compartment called the silica deposition vesicle, with control occurring at multiple levels. Understanding the molecular details of the process requires identifying structural intermediates and correlating their formation with genes and proteins involved. We have applied molecular, genomic, and microscopic approaches to examine diatom cell wall synthesis. During characterization of structural intermediates, we identified three scales and two distinct stages in structure formation, and observed a correlation between the formation process and optimization of the final structural property required. Using synchronized cultures, we used microarrays to screen all genes in the genome of Thalassiosira pseudonana for a characteristic expression pattern identified in other cell wall genes. One hundred and four genes were identified, and categorized according to cellular role or possible function. We are determining the intracellular localization of proteins encoded by these genes to evaluate their involvement in cell wall formation. Correlation of structure formation with the genes and proteins involved will be essential to understand how diatom genetic information is translated into active chemical moieties that ultimately control the formation of the solid material. These approaches, coupled with genetic manipulation tools, will enable elucidation and manipulation of the intracellular systems involved in biogenic nanostructured silica synthesis, facilitating applications of diatoms in materials science.
9:45 AM - T1.3
Lessons from Diatoms: Formation of nanopatterned functional ceramics under ambient conditions
Nils Kroger 1 2 , Nicole Poulsen 1 , Ken Sandhage 2 , Matt Dickerson 2 , Gul Ahmad 2
1 Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractThe direct syntheses of functional organic-inorganic hybrid materials are severely restricted by the incompatible thermal and/or chemical conditions often required to form desired organic and ceramic phases. Recently, biomineral-forming organisms like diatoms (see figure) and sponges have been recognized as inspirational sources of new strategies for directly synthesizing such hybrid materials under environmentally benign conditions. Here we present novel in vitro and in vivo approaches to produce functional ceramics employing molecules from diatoms as well as using living diatoms themselves.The in vitro approach relies on diatom genes that encode proteins (termed silaffins) involved in biosilica formation. We have designed recombinant silaffins that are able to induce the rapid formation of silica and titania from aqueous precursor solutions. Recombinant silaffin rSilC enabled the synthesis of hierarchically nanopatterned rutile microparticles at ambient temperature and neutral pH. Due to its high refractive index, rutile is highly desirable material for photonic applications, yet previous rutile syntheses require extreme reaction conditions (600-800C, or strongly acidic, hydrothermal conditions). Using an in vivo approach we have developed a unique method for the silica immobilization of functional proteins. The bacterial enzyme hydroxylaminobenzene mutase (HabB) was expressed as a silaffin-fusion protein in the diatom Thalassiosira pseudonana, which resulted in targeted incorporation of the fusion protein into the T. pseudonana silica cell wall. The diatom silica bound HabB was enzymatically active, and remained functional as well as associated with the diatom silica during isolation.
10:00 AM - T1.4
Silicification Biomimetic Studies in Confined Media.
Thibaud Coradin 1 , Clementine Gautier 1 2 , Pascal Lopez 2 , Myriana Hemadi 1 , Jacques Livage 1
1 Chimie de la Matiere Condensee, CNRS-UMR 7574, Université Paris VI, Paris France, 2 Diatom Signaling and Morphogenesis, CNRS-FRE 2910, Ecole Normale Supérieure, Paris France
Show Abstract10:15 AM - **T1.5
The Bioclastic and Shape-preserving Inorganic Conversion (BaSIC) Route to Chemically Tailored Three-Dimensional Nanostructured Microassemblies
Kenneth Sandhage 1 2 , Samuel Shian 1 2 , Michael Weatherspoon 1 2 , Zhihao Bao 1 2 , Phillip Graham 1 2 , David Lipke 1 2 , Eric Ernst 1 2 , Matthew Dickerson 1 2 , Shawn Allan 1 2 , Ye Cai 1 2 , Gul Ahmad 1 2 , Michael Haluska 1 2 , Robert Snyder 1 2 , Laura Sowards 3 , Rajesh Naik 3
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Biotechnology Group, Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, United States
Show AbstractAppreciable worldwide R&D effort is underway to develop new fabrication routes to three-dimensional (3-D) nanostructured micro-assemblies for advanced devices. Such processes must be capable of: i) precise 3-D fabrication on a fine (down to nanometer) scale, and ii) mass production on a large scale. These often-conflicting requirements can be addressed with a hybrid fabrication paradigm that merges biological self-assembly with synthetic chemistry: Bioclastic and Shape-preserving Inorganic Conversion (BaSIC)*. Nature provides numerous examples of organisms that assemble biominerals into complex 3-D (bioclastic) microscale structures. For example, diatoms (unicellular planktonic algae) assemble intricate 3-D microshells (frustules) comprised of silica nanoparticles. Each of the tens of thousands of extant diatom species forms a microshell with a distinct shape and pattern of fine features. Sustained reproduction of a given diatom species can yield enormous numbers of identical frustules (e.g., 40 reproduction cycles can yield >1 trillion replicas!). Such massively parallel, genetically precise, and environmentally benign 3-D self-assembly is highly attractive for device manufacturing, and has no man-made analog. However, the natural silica-based chemistry of diatom frustules inhibits their use in a variety of devices. With BaSIC, these biogenic assemblies can be converted into a wide range of new functional chemistries (TiO2, F-doped TiO2, ZrO2, Cl-doped ZrO2, MgO, BaTiO3, Eu-doped BaTiO3, Zn2SiO4, Mn-doped Zn2SiO4, polymers, etc.), while preserving the 3-D frustule morphologies. Various chemical conversion approaches (gas/solid reaction, liquid/solid reaction, conformal coating, reaction and coating, coating and reaction) utilized in the BaSIC process to generate shape-preserved replicas will be described. Such shape-preserving chemical alteration has also been applied to nanostructured synthetic silica preforms. The optical and chemical properties of such chemically-altered nanostructured micro-assemblies will be discussed. Future advances in the genetic engineering of diatoms (to allow for tailoring of frustule shapes), coupled with shape-preserving chemical modifications via BaSIC, offer the exciting promise of 3-D Genetically Engineered Micro/nanodevices (3-D GEMs).*K. H. Sandhage, “Shaped Microcomponents via Reactive Conversion of Biologically-derived Microtemplates,” U.S. Patent No. 7,067,104, June 27, 2006.
10:45 AM - T1.6
The activity of Diatom inspired synthetic polyamines in Silicification
Carole Perry 1 , David Belton 1 , Vadim Annenkov 2 , Siddharth Patwardhan 1 , Elena Danilovtseva 2
1 Biomedical and Natural Sciences, Nottingham Trent University, Nottingham United Kingdom, 2 , Limnological Institute of Siberian Branch of Russian Academy of Sciences, Irkutsk Russian Federation
Show AbstractIn nature many organisms are able to capture and use monosilicic acid in the formation of highly functional and sometimes elaborate siliceous structures. Much effort has been invested in attempts to determine the underlying synthetic principles involved in this chemical manipulation, not least into investigations involving the unicellular algae diatoms. Within the frustule considerable levels of polyamines have been found either as post translational modifications on the side chain of lysine groups in the peptides known as silaffins or as isolated molecules. Silaffins and the polyamines are proposed to play a significant role in diatom biosilicification producing diverse nano-structured silica valves. The isolated polyamines influence the condensation of silica from condensing systems based on alkoxysilanes or sodium silicate precursors, producing dense silica spheres that are not produced under similar conditions in their absence. The presence of polyamines in nature is not an unusual occurrence with cellular compounds such as spermine, and spermidine, common and the formation of these much longer diatom polyamine species is likely to be a serendipitous extension of their biosynthetic process. The polyamines so far isolated from diatoms have been shown to be very species dependant with varying methylation levels of the amine functionality from primary to quaternary and it is thought that this species dependency ultimately determines the final structural form of the diatom thecae.Here we report on the novel stepwise synthesis of a group of linear methylated propylamines and their activity in silica formation in vitro. Measurements were conducted to determine kinetic effects, the solution state of the polyamines, the surface area and porosity of the siliceous products and the gross morphologies. Comparison is made with the naturally occurring polyamines and the influence of chain length and amine separation assessed both as amine solution species and in the nature of the siliceous materials produced. Their effects on the condensation of a model silicic acid system is reported in terms of kinetic changes through pH and amine concentration as well as characterisation of the novel bimodal (dense hollow microporous spherical and thin walled vesicular) silicas produced. The charge states of the amines during addition to the condensation process were found to affect their solution chemistry and to be critical to the nature of the materials produced, with these charge states being in turn highly affected by amine length. The influence of the level of primary, secondary and tertiary amine functionality has also been investigated. These results show that rates of proton transfer are important in terms of flux from amines to precursor. Finally we show how siliceous materials with tailored properties can be produced through control of pH, amine concentration, chain length and ionic strength.
11:00 AM - T1:Biomat
BREAK
11:30 AM - T1.7
Alkylation is crucial to enhancement of silica condensation rate by diamines.
David Robinson 1 , Blake Simmons 1 , Judith Rognlien 1
1 , Sandia National Laboratories, Livermore, California, United States
Show Abstract11:45 AM - T1.8
Formation of Porous Hydroxyapatite
Deepa Khushalani 1
1 Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai India
Show AbstractMost biological materials with predominantly mechanical function have a hierarchical structure consisting of several different length scale levels (angstrom to millimeter) and incorporate a composite structure where an inorganic component is epitaxially linked to an organic component. In this way, tough materials are designed by nature based on a complex configuration where size and morphology of component and its intricate link to the other species present in the composite all play a pivotal role in creating an impressive 3D organization with multifaceted function. In bone for example, the organization is an elaborate design based on collagen fibrils reinforced with nanosized inorganic mineral particles (hydroxyapatite). These nanosized mineral platelets are able to sustain a large tensile stress whereas the protein layer between them sustain sheer stress. This is an excellent example of how morphology of the inorganic component plays a pivotal role in the function of the overall composite. To this aim, both soft-condensed matter and solid inorganic porous supports have been studied in formation of porous hydroxyapatite. The work carried out using (1) a novel micoremulsion involving reverse micelles of calcium bis(2-ethylhexyl)phosphate (Ca(DEHP)2) and (2) Porous membrane supports of alumina and polycarbonate will be detailed. Products such as nanoporous porous hydroxyapatite with intricate tubular morphology will be presented along with their characterization involving microscopy, diffraction, and their uses in bioactive studies will also be evaluated.
12:00 PM - T1.9
Directed Evolution of Hydroxyapatite-Associated Protein Using Phage Display
Seung-Wuk Lee 1 2 4 , Jing Hang Huh 3 2 , Eddie Wang 1 4 , Emily Perttu 1 4 , Yue Zhao 1
1 Bioengineering , University of California, Berkeley, Berkeley, California, United States, 2 Physical Bioscience Division, Lawrence Berkeley National Lab, Berkeley, California, United States, 4 , UCSF and UCB Joint Graduate Group in Bioengineering, Berkeley, California, United States, 3 Chemical Biology, University of California, Berkeley, Berkeley, California, United States
Show AbstractThe formation of natural bone is thought to occur by the templated mineralization of HA by the surrounding proteins, which include collagen and highly acidic phosphoproteins attached to the collagen scaffold. It has been proposed that the acidic groups serve as binding sites for calcium ions and align them in an orientation that matches the HA crystal lattice, but the biological mineralization process is not understood at the molecular level. Using directed evolution process (phage display), we identified specific binding peptides for single crystal hydroxyapatite in various pH ranges and study their interactions between HA binding peptides and crystal surfaces. Remarkably, the consensus HA binding peptides resulted in characteristic tripeptide repeat (Pro-X-Y) at pH 7.5 and (Ser-Ser-Asp) at pH 5. These sequences are similar to the major repeats of type I collagen and dentin phosphoproteins respectively. Using a panel of synthetic peptides, we defined the structural features required for binding and mineralizing activity of HA. We also incorporated these short HA-binding peptides to construct three-dimensional bone-like materials.
12:15 PM - **T1.10
Mollusk shell nacre- and prismatic sequence - directed crystal design.
John Evans 1 , Sebastiano Collino 1 , Jennifer Giocondi 2 , Christine Orme 2 , Il Kim 1 , Katya Delak 1
1 , New York University, New York, New York, United States, 2 Biophysical and Interfacial Sciences, Lawrence Livermore National Laboratories, Livermore, California, United States
Show AbstractThe biomineralization environment of the nacre and prismatic layers of the mollusk are undoubtedly complex, consisting of many proteins present at the same or at different times in the extracellular matrix, and it is likely that numerous polypeptides jointly manage the overall polymorph selection process. Similarly, it has been postulated that Mg (II) also participates in calcium carbonate mineralization, although the exact role of this metal ion is not yet defined. Up until now, our in vitro mineralization studies of individual nacre- and prismatic-specific polypeptides have omitted this important feature of complexity, i.e., the participation of different polypeptides and Mg (II) in the calcium carbonate formation and the polymorph selection process. Obviously, if Nature employs multiple agents to effect net control over crystal formation, then material science might also need to adopt similar approaches to “tailor” inorganic - based materials with specific properties. To address this issue, we have explored the combinatorial effects of nacre and prismatic polypeptide sequences and the presence of “catalytic” levels of Mg (II)(1:10 Mg : Ca) on in vitro crystal growth. We find that It appears that low levels of Mg (II) can affect the mineralization activity of certain calcium biomineralization sequences in selective ways. In particular, we observe either subtle effects on crystal morphology or surprising alterations that deviate from normal polypeptide activity patterns. Moreover, Mg (II) can “switch” the function of a set of peptides to mimic one another with regard to selective adsorption, pinning, or growth patterns in calcite dislocation hillocks. We believe that Mg (II) can catalytically alter the outcome of protein-mediated biomineralization. With regard to combinatorial mixtures of mollusk shell polypeptides, there is clearly a synergistic effect when specific biomineralization protein sequences are combined together within in vitro assays settings. At this point we do not know if the observed morphologies are due to individual, overlapping effects arising from each peptide component, or, due to effects brought about by the interaction of one peptide species with another. Moreover, we do not know if these synergistic effects are the result of peptide - mineral interactions and/or peptide-catalyzed ion cluster assembly or shuttling in solution. We are now beginning to explore these possibilities in more detail.
12:45 PM - T1.11
Adaptable CaCO3 Mineralization Templates Based on Bis-urea Surfactants: in-situ Synchrotron X-ray Measurements of Structure and Kinetics.
Elaine DiMasi 1 , Seo-Young Kwak 1 , Benoit Pichon 3 , Daniela Popescu 2 , Maarten Smulders 2 , Natalia Chebotareva 2 , Rint Sijbesma 2 , Nico Sommerdijk 3 4
1 National Synchrotron Light Source Dept., Brookhaven National Laboratory, Upton, New York, United States, 3 Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven Netherlands, 2 Department of Chemistry and Chemical Engineering, Eindhoven University of Technology, Eindhoven Netherlands, 4 Soft Matter Cryo-TEM Research Unit, Eindhoven University of Technology, Eindhoven Netherlands
Show AbstractT2: Bioinspired Materials-II
Session Chairs
Tuesday PM, April 10, 2007
Room 2006 (Moscone West)
2:30 PM - **T2.1
Bio-inspired material synthesis and nanoelectronic devices production by protein supramolecule.
Ichiro Yamashita 1 2 3
1 Material Science, NAIST, Ikoma Japan, 2 ATRL, Matsushita Electric Ind. Co., Ltd, Kyoto Japan, 3 CREST, Japan Science and Technology Agency, Kawaguchi Japan
Show AbstractWe proposed a new process for fabricating functional nano-structure on a solid surface using protein supramolecules, which is named “Bio Nano Process” (BNP). We employed a cage-shaped protein, apoferritin as a spatially restricted chemical reaction chamber and biomineralized several kinds of nanoparticles (NP) in the apoferritin cavity. Among them are compound semiconductor NPs, CdSe, ZnSe, CdS. To synthesize these compound semiconductor NPs in the cavity, we designed the slow chemical synthesis system (SCRY) and the two step synthesis process (TSSP). Cd and Zn ions were stabilized by ammonia water and slow sown the chemical reaction speed outside apoferritin (SCRY). Se or S ions are added in the final step to let Cd or Z cation enter the cavity first (TSSP). The combination of the SCRY and TSSP works well and NPs can be synthesized with high efficiency. Making use of protein-protein and protein-solid surface interaction, a monolayer of 2D crystal of them can be made on the silicon wafer in self-assembly manner. Since the protein shell is vulnerable, heat-treatment or UV/ozone-treatment of the array produced a two-dimensional inorganic NP array on the silicon surface. The result demonstrated that inorganic nano-structure can be made by the combination of biomineralizaion, self-assembly and vulnerability of the protein. The inorganic nano-structure obtained by this process can be applied in a various field. We used the inorganic array, iron, cobalt and Indium oxide NP array for the fabrication of the floating nanodots memory. The fabricated floating gate memory functioned well and had the nice endurance and retention time. We also proposed another process using the obtained iron-oxide NP array as the nanometric etching mask. This was realized by the neutral beam etching and 7nm diameter Si nano crystalline columns with high aspect ratio were fabricated. Another effort to make a large biotemplate for single electron transistor (SET) produced a ball and spike type protein supramolecules which has a central cage-shaped protein and protruding spikes. This bio-template will be used to produce a SET by combining the biomineralization technique. These experimental results demonstrated that the BNP can fabricate the inorganic nanostructure using protein supramolecules and the BNP opens up a biological path to nanoelectronic devices.
3:00 PM - T2.2
Biomimetic Synthesis of Silica Nanoparticles
Tracy Davis 1 , Mark Snyder 1 , Michael Tsapatsis 1
1 CEMS, University of MN, Minneapolis, Minnesota, United States
Show AbstractIt is well recognized (1-5) that silica nanoparticles will form upon hydrolysis of tetraethylorthosilicate (TEOS) in basic solutions in the presence of tetrapropylammonium (TPA) and other alkylammonium cations upon exceeding the solubility limit of silica. We recently showed (6) that such silica nanoparticles, formed in the presence of TPA, participate in the growth of zeolites through an oriented aggregation mechanism. Prospects exist for formation and directed assembly of novel materials based upon the identification of such silica nanoparticles. In addition to the highly basic TPA-based pathways, biomimetic silica formation has also received significant attention (7-13). Such work has been driven, at least in part, by the goal to reveal the mechanisms by which hierarchical biosilica structures form and their extension to complex materials synthesis. While possible analogies between peptide mediated biosilica formation and alkylammonium cation templated zeolite crystallization have been acknowledged, the existence of nanoparticles in basic amino acid or peptide sols, similar to those in TPA silica sols, has not yet been reported.Here, we describe a method for room temperature synthesis of silica nanoparticles ranging in size from 4.5 nm to 8 nm in diameter in lysine-silica sols. The particles are characterized by cryogenic transmission electron microscopy and small angle X-ray scattering. Adjustment of silica and lysine concentrations within the sols enables fine control of the size and number density of the nanoparticles. While peptide-mediated biosilica formation is not a new concept in and of itself, the nanoparticles identified here serve as the smallest silica aggregates identified in these systems. Their existence and benign synthesis suggests that they may be of use as intermediate, high-purity reagents not only for films and gels, but also for novel, complex and biocompatible silica-based materials and nanocomposites. References 1. C.-H. Cheng, D. F. Shantz, J. Phys. Chem. B 109, 7266 (2005).2. J. Fedeyko, J. Rimer, R. Lobo, D. Vlachos, J. Phys. Chem. B 108, 12271 (2004).3. J. Fedeyko, D. Vlachos, R. Lobo, Langmuir 21, 5197 (2005).4. B. Schoeman, O. Regev, Zeolites 17, 447 (1996).5. S. Yang, A. Navrotsky, D. Wesolowski, J. Pople, Chem. Mater. 16, 210 (2004).6. T. M. Davis et al., Nat. Mater. 5, 400 (May, 2006).7. D. Belton, G. Paine, S. V. Patwardhan, C. C. Perry, J. Mater. Chem. 14, 2231 (2004).8. J. N. Cha, G. D. Stucky, D. E. Morse, T. J. Deming, Nature 403, 289 (2000).9. N. Kroger, R. Deutzmann, M. Sumper, Science 286, 1129 (1999).10. N. Kroger, S. Lorenz, E. Brunner, M. Sumper, Science 298, 584 (2002).11. M. Sumper, N. Kroger, J. Mater. Chem. 14, 2059 (2004).12. T. Yokoi et al., JACS 128, 13664 (2006).13. T. M. Davis, M. A. Snyder, J. E. Krohn, M. Tsapatsis, Chem. Mater. (2006, accepted).
3:15 PM - T2.3
Structure and Orientation of an Amelogenin on Hydroxyapatite
Wendy Shaw 1 , Susan Kreuger 2 , Ursula Perez-Salas 3 , Kim Ferris 1 , Barbara Tarasevich 1
1 , Pacific Northwest National Labs, Richland, Washington, United States, 2 , NIST, Gaithersburg, Maryland, United States, 3 , Argonne National Lab, Argonne, Illinois, United States
Show AbstractAmelogenin consists of 90% of the protein present during the formation of the unusually long and highly ordered enamel crystals and is found to be critical in proper enamel development. Here we investigated an amelogenin, LRAP, to understand its structure and amino acids important in interacting with HAP. There is indirect evidence of a specific interaction between the C-terminus of amelogenin and the crystal lattice exists, but only recently have direct measurements been made to indicate how the protein is interacting with the inorganic crystal. Solid state NMR and neutron reflectivity are complementary techniques which can provide insight into the protein-crystal interface, under biologically relevant conditions. Using solid state NMR and NR, experimental data will be presented that demonstrate that the C-terminus of LRAP is close enough to the surface of HAP to influence the resulting crystal structure. The structure of the protein in the region has also been investigated. The experimental results are combined to develop a model of the LRAP-HAP interface, providing significant molecular level insight into enamel formation. This work was funded by the NIDCR institute of NIH. PNNL is operated by Battelle Memorial Institute for the U.S. Department of Energy.
3:30 PM - **T2.4
Reversibly Actuated Nanostructures
Joanna Aizenberg 1 , Tom Krupenkin 1 , Alexander Sidorenko 1
1 , Lucent Technologies/Bell Laboratories, Murray Hill, New Jersey, United States
Show AbstractAn important feature of biological/natural systems is their response to external stimuli with the subsequent change in structure or function. The ability to “engineer” adaptiveness into the next generation devices is becoming a key requirement and challenge in materials science and engineering. Here we describe new hybrid nano/micro-structures that mimic biological cilia. These structures are designed to reversibly change and dynamically control the surface geometry, rougness and interfacial chemistry. We demonstrate the application of these novel architectures as actuators that offer fast reversible formation of complex micropatterns.
4:00 PM - T2.5
Bio-Inspired Routes to Functional Metal Oxides
David Wright 1 , Sarah Sewell 1 , Leila Deravi 1
1 Chemistry, Vanderbilt University, Nashville, Tennessee, United States
Show AbstractUnicellular plankton known as diatoms are able to produce ornate nanostructures of silica at ambient conditions. In contrast, current materials approaches require extremes of temperature and pH. Diatoms are able to biomineralize the silica using species specific peptides known as silaffins that possess lysine residues heavily post-translationally modified with polyamines. Herein, we report the use of amine-terminated dendrimers as mimetic templates for silica condensation. Further, the unique host-guest capabilities of the dendrimer may be used to create novel functional silica nanospheres with applications in supported heterogeneous catalysis, biocatalysts, and as biological probes. Additionally, these materials may be readily processed to create functional biomimetic surfaces.
4:15 PM - T2.6
An In Vitro Model System for Elucidating the Crystallochemical Mechanisms of Biomineralization.
Laurie Gower 1
1 Materials Science & Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractBiologically formed hard tissues, often referred to as biominerals, are hierarchical composite structures formed of mineral and organic matrix. The organic matrix, being composed of proteins and/or polysaccharides, often consists of an insoluble phase (such as collagen in bone, or chitin in mollusk shells), as well small quantities of water soluble acidic (i.e., polyanionic) proteins. The acidic macromolecules associated with biominerals have long been thought to regulate the formation of the biomineral crystals, as well as influence the final properties of the bioceramic composite if they become occluded within the mineral phase. Our in vitro studies have led us to propose that these acidic proteins may serve as process-directing agents, in which we have shown that mimetic polypeptides (e.g. polyaspartate) can induce liquid-liquid phase separation in the crystallizing medium, which transforms the traditional crystallization process into an amorphous precursor process. An important contribution of the polyanionic macromolecules is the level of hydration water that is integrated with the sequestered ions to generate the amorphous precursor, because this imparts fluidity to the precursor phase, which has important consequences with respect to molding and shaping crystals since the crystals retain the shape of the precursor phase once it has solidified and crystallized. By manipulating the precursor phase, non-equilibrium crystal morphologies can be generated which mimic many biomineral features, such as the deposition of thin mineral tablets and films, “extrusion” of crystal fibers, patterning and templating of thin mineral films, “molding” 3-D mineral structures, and intrafibrillar mineralization of collagen to mimic the interpenetrating nanostructure of bone. In light of recent studies that have shown a transient amorphous phase is present in many biominerals, there is a strong likelihood that this process plays a fundamental role in the morphogenesis of calcific biominerals. With respect to biomimetic engineering, we have been examining the crystallochemical mechanism involved in this polymer-induced liquid-precursor (PILP) process, to determine if there are general concepts related to this non-specific process which can ultimately be adapted to a variety of inorganic crystallization systems.
4:30 PM - T2.7
Artificial proteins having mineralization motifs
Kiyotaka Shiba 1
1 , Cancer Institute, Tokyo Japan
Show AbstractThe presence of peptide motifs that are related to biomineralization provides the synthetic biologist with the opportunity to fabricate novel proteins affecting mineralization processes. Here I describe our method that enables one to combine multiple peptide motifs to create functional proteins. With this method, we prepared a protein library from natural biomineralization motifs as well as artificial motifs (created by a peptide phage system). Characterization of the created proteins will be introduced.
4:45 PM - **T2.8
Viruses – dynamic, responsive nanostructures with materials applications
Trevor Douglas 1 2 , Mark Young 2
1 Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana, United States, 2 Center for BioInspired Nanomaterials, Montana State University, Bozeman, Montana, United States
Show AbstractViruses have emerged as platforms for synthetic manipulation with a range of applications from materials to medicine. The use of viruses as synthetic templates utilizes the inherent properties that viruses have evolved. The essential nature of all viruses is to infect a host cell, replicate, package its nucleic acid, and exit the cell. In the process, viruses have evolved to move through a broad range of chemical environments. In their journey, viruses demonstrate a remarkable plasticity in their metastable structure and dynamics including coordinated assembly/disassembly and site-specific delivery of cargo molecules. These properties of viruses parallel the ideal properties of many synthetic materials. An appreciation of these properties has resulted in a paradigm shift from the study of viruses as disease causing agents to highly useful molecular assemblies, which can be chemically and genetically manipulated. This allows for synthetic manipulation to impart new function to protein cage architectures combining the best of evolution and truly intelligent design. Characterized viruses represent only a fraction of the predicted viral diversity present in the biosphere making this an exciting time for virology and their applications in materials science.
5:15 PM - T2.9
Interfaces Involving Biomolecules and Inorganic Materials: a Solid State NMR Approach.
Christian Bonhomme 1 , Cristina Coelho 1 , Thierry Azais 1 , Geoffrey Hartmeyer 1 , Florence Babonneau 1 , Akiyoshi Osaka 4 , Satoshi Hayakawa 4 , Bruno Alonso 2 , Michel Wong Chi Man 3 , Guilhem Arrachart 3
1 , universite P et M Curie, Paris France, 4 , Okayama university, Okayama Japan, 2 , CRMHT CNRS, Orléans France, 3 , ENSCM, Montpellier France
Show AbstractThe structural characterization of biological/inorganic interfaces is one of the most fascinating spectroscopic challenge in the frame of bio-inspired materials. Recent developments in high resolution solid state NMR offers new perspectives in terms of chemical bonding and spatial connectivities between the organic and inorganic components of a given material. 1H nuclei are a key structural probe, as protons are present at all interfaces and "tailor" them by establishing complex hydrogen bonded networks. We will present the latest 1H NMR experiments, including 1D (single quantum -SQ-, ultra fast MAS at very high fied) and 2D (double quantum, DQ) experiments, illuminating the structural features of ureidopyrimidinone silica based materials [1-2]. The DQ experiments allow to establish unambiguous connectivities between pairs of protons, allowing the precise description of H-bonded networks in the crystalline precursors, as well as in the corresponding structured materials. The 1H high resolution solid state NMR approach has been extented to the study of bio-inspired materials, involving SiO2 pillars and adenine/thymine complementary bases [2].Solid state NMR offers original approaches, based on the various interactions involved, such as the heteronuclear dipolar coupling (involving unlike spins) and J-coupling (establishing chemical bond connectivities). These new opportunities will be illustrated by the study of silicophosphate gels, which are excellent candidates for biocompatible materials. New NMR techniques have been implemented for that purpose, including original MAS-J-techniques [3]. The study of substituted HAP materials will be also presented, including new insights obtained by 1H/13C/31P triple resonance dipolar-mediated experiments [4].[1] J. J. E. Moreau, M. Wong Chi Man et al. Angew. Chem., 43, 203, 2004.[2] G. Arrachart, PhD thesis, december 2005, University of Montpellier, France.[3] (a) C. Coelho, C. Bonhomme et al. J. Sol-Gel Sc. Technol., 40, 181, 2006. (b) C. Lejeune, C. Bonhomme et al. Solid State NMR, 27, 242, 2005. (c) C. Coelho, C. Bonhomme et al. J. Magn. Reson., 179, 114, 2006. [4] (a) E. Fujii, A. Osaka, S. Hayakawa, F. Babonneau, C. Bonhomme et al. Acta Biomaterialia, 2, 69, 2006. (b) S. Hayakawa, A. Osaka, F. Babonneau, C. Bonhomme et al. Key Engin. Mater., 309, 503, 2006. (c) S. Hayakawa, A. Osaka, F. Babonneau, C. Bonhomme et al. J. Am. Ceram. Soc, accepted for publication.
5:30 PM - **T2.10
Geckel: Nanostructured Wet/Dry Adhesive Inspired by Gecko and Mussel.
Phillip Messersmith 1 2 , Haeshin Lee 1
1 Biomedical Engineering, Northwestern University, Evanston, Illinois, United States, 2 Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractLiving organisms have evolved a variety of elegant strategies for adhering to surfaces, and several of these have inspired materials scientists in their quest for new high performance synthetic adhesives. Two classic models for bioadhesion include the gecko and the mussel. The gecko adheres to surfaces on a temporary basis through the use of specialized foot-hairs called setae, which are subdivided into terminal nano-sized contact pads (spatulae). Gecko adhesion is strong yet reversible, allowing the gecko to cling to vertical and even inverted surfaces. However, the gecko adhesive strategy works poorly under wet or high humidity conditions. In this talk we report dramatic enhancement of the wet performance of gecko mimetic adhesives through the use of mussel adhesive protein mimetic polymers. In contrast to geckos, mussels thrive under wet conditions through secretion of specialized adhesive proteins that mediate attachment to wet surfaces. The design, synthesis and characterization of a nanostructured temporary adhesive material that exploits both gecko and mussel adhesive strategies will be described. The hybrid ‘geckel’ adhesive adheres well to surfaces under both dry and wet conditions and can be removed and reattached over 1000 times with little decrease in performance. The ‘geckel’ adhesive should prove useful in medical, consumer, military and other applications where temporary adhesion under wet or dry/wet environments.
Symposium Organizers
Rajesh R. Naik Air Force Research Laboratory
Carole C. Perry Nottingham Trent University
Kiyotaka Shiba Japanese Foundation for Cancer Research
Rein Ulijn University of Manchester
T3: Abiotic/Biotic Interactions
Session Chairs
Wednesday AM, April 11, 2007
Room 2006 (Moscone West)
9:30 AM - T3.1
Selectivity and Binding Kinetics of Genetically Engineered Peptides on Metals and Oxides.
Brandon Wilson 1 , Urartu Seker 1 2 , Candan Tamerler 1 2 , Mehmet Sarikaya 1 2
1 Material Science, University of Washington, Seattle, Washington, United States, 2 Molecular Biology & Genetics, Istanbul Technical University, Istanbul Turkey
Show AbstractInorganic binding peptides have been widely studied in recent years because of their potential for applications in molecular recognition elements, nanoscale constructs, and agents for inorganic biofabrication. One major missing area in many of the previous studies, quantitative binding and kinetics of these peptides, has to be studied for a robust design for practical applications. In this study, two metal binding (gold and platinum) and quartz binding peptides were studied based on their specific affinities towards the materials that they were originally selected for. Surface plasmon resonance (SPR) spectroscopy was used to determine kinetics constants on substrates prepared for determining specific affinity and selectivity of the peptides. The combinatorially selected, first-generation, peptides as well as their post-selection engineered derivatives, i.e., multiple repeats and constraint-forms, were used for binding experiments. The binding ability of each peptide to its selected substrate was compared to the binding on other substrates to determine the material selectivity. First and second generation peptides displayed unexpected binding and selectivity behavior that could be explained by a combination of chemical, physical and biochemical forces due to peptides-substrate interactions. Research supported by ARO-DURINT and NSF-MRSEC programs at the University of Washington.
9:45 AM - T3.2
Cell spreading predicted using calculated LogP of surface tethered amino acids
Rachel Rawsterne 2 , Simon Todd 2 , Julie Gough 2 , Frank Rutten 1 , Rein Ulijn 2 3 , Morgan Alexander 1
2 School of Materials, University of Manchester, Manchester United Kingdom, 1 Laboratory of Biophysics and Surface Analysis, School of Phaarmacy, The University of Nottingham, Nottingham United Kingdom, 3 Manchester Interdisciplinary Biocentre , University of Manchester, Manchester United Kingdom
Show AbstractThe interactions of cells with synthetic surfaces are a critical factor in biomaterials design. It would be invaluable if these interactions could be controlled and predicted. Surface wettability is commonly correlated with cell attachment to materials, although many exceptions exist to any rule that has been proposed. In pharmaceutical science it is common practice to use the logarithm of the partition coefficient between water and octanol, LogP, as a reliable indicator of the behaviour of drug molecules in solution and the body. Methods are available to reliably predict LogP values directly from molecular structure to provide a calculated logP parameter, or ClogP. In the experiments described here we utilised the naturally occurring amino acids as a library of chemical functionalities, these molecules were immobilised to glass surfaces using amino silane chemistry. The successful modification of the glass surface with the surface tethered amino acids was verified using X-ray photoelectron spectroscopy, secondary ion mass spectrometry and water contact angle.1 CLogP was calculated from the amino acid molecular structure. A correlation of ClogP with the cosine of the water contact angle was noted when amino acids with charged side chains were omitted.2 Spreading of primary human osteoblast cells was found to follow a linear relationship with ClogP. The Vroman effect may be used to rationalise this observation in the form of the adsorption and displacement of adhesive and non adhesive proteins at the surface from the serum containing media. To the best of our knowledge, the ClogP parameter is the first mathematical method based on molecular structure that may be useful in predicting cell spreading on chemically modified surfaces via non-specific interactions. The potential expansion to other surfaces and limitations of this approach will be discussed.1.Rawsterne, R. E.; Gough, J. E.; Rutten, F.; Pham, N. T.; Poon, W. C.; Flitsch, S. L.; Maltman, B.; Alexander, M. R.; Ulijn, R. V., Controlling protein retention on enzyme-responsive surfaces. Surf. Interface Anal. 2006, 38, 1505–1511.2.Rawsterne, R. E.; Todd, S. J.; Gough, J. E.; Farrar, D.; Rutten, F. J. M.; Alexander, M. R.; Ulijn, R. V., Cell Spreading Correlates with calculated LogP of Amino Acid-modified Surfaces. Acta Biomateriala 2006 (submitted).
10:00 AM - T3.3
Growth of metal nanostructures on templates of RNA-aptamer catalysts formed by Scanned Probe Nanolithography (SPN).
Sungwook Chung 1 , John LaTour 1 , Theodore Tarasow 1 , James De Yoreo 1 , Bruce Eaton 2 , Lina Gugliotti 3 , Daniel Feldheim 3
1 Chemistry, Materials and Life Sciences (CMLS) Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Department of Chemistry and Biochemistry, University of Colorado, Boulder, Boulder, Colorado, United States, 3 Department of Chemistry, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractDirecting the organization of nanomaterials at surfaces is a fundamental challenge of nanoscience. Combining self-assembly with lithography in which chemical patterns serve as templates to define the locations of nanoparticle attachment has been explored as one potential solution. But to be generally applicable to multi-component systems, this approach requires appropriate surface chemistries together with a variety of linker molecules that can be used selectively template a wide range of materials. Moreover, these compounds must be amenable to nanoscale patterning on surfaces in a functional state. Recently, RNA molecules were demonstrated as catalysts for synthesis of metal nanoparticles and can, in principle, also be used to synthesize semiconductors. Moreover, they are known to bind target biomolecules with high selectivity. Consequently they represent a single template chemistry for creating architectures that integrate metal, semiconductor and biomolecular components.Here we report results using SPN to create patterns of RNA molecules that serve as catalytic biochemical templates for the growth of Pd nanoparticles. We have used in vitro selection to isolate and amplify RNA sequences that catalyze the growth of Pd. Two pyridyl-modified RNA sequences (Pdase) were used to form hexagonal and cubic Pd nanoparticles using the organometallic precursor complex tris(dibenzylideneacetone) dipalladium(0) (Pd2(DBA)3). Atomically flat gold substrates coated with self-assembled monolayers (SAMs) of poly(ethylene glycol) (PEG) terminated alkyl thiols were patterned with maleimide terminated alkyl thiols using SPN. These patterns had feature sizes ranging from 10 — 1000 nm and provided binding sites for the 5’ thiol group of the RNA catalysts (5’-GIMP-Pdases). These surface-immobilized RNA catalysts still showed catalytic activity with control over both the location and shape of the Pd nanoparticles. The growth of Pd nanoparticles at these templates was then investigated using AFM. Based on these results, we discuss the possible mechanisms by which RNA template direct nanoparticle growth.This work was supported by the Laboratory Directed Research and Development Program (LDRD Laboratory-Wide Funding, 06-LW-051). This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.
10:15 AM - T3.4
A Novel Informatics-Based Approach for the Design of Inorganic Binding Peptides.
Ersin Emre Oren 1 , Ram Samudrala 2 , Deniz Sahin 3 1 , Marketa Hnilova 1 , Mustafa Gungormus 1 3 , Urartu Seker 1 3 , Sibel Cetinel 3 1 , Anil Cebeci 3 , Nevin Gul Karaguler 1 , Candan Tamerler 3 1 , Mehmet Sarikaya 1
1 Materials Science and Engineering Department, University of Washington, Seattle, Washington, United States, 2 Department of Microbiology, University of Washington, Seattle, Washington, United States, 3 Molecular Biology and Genetics, Istanbul Technical University, Istanbul Turkey
Show AbstractIn nature, proteins control structures and functions of biological hard tissues through specific molecular interactions with inorganics. Emulating biology, genetically engineered inorganic-binding peptides are used as molecular building blocks to construct functional inorganic and hybrid materials for applications in materials science, biotechnology, and medicine. Recently, in vivo (phage and cell-surface display) and in vitro (ribosomal and mRNA display) combinatorial biology protocols have been adapted to select peptides with affinities to desired materials. Although many short peptide sequences specific to metals, oxides, and semiconductors have been discovered and used in the proof-of-principle synthesis, morphogenesis, and assembly of inorganics, building blocks for engineering materials, the nature of peptide/inorganic interaction is not yet well understood. Experimental as well as modeling studies towards this understanding are in their infancy, and accurate force field parameters required to model the protein substrate interaction are still under development. The diverse range of inorganics that need to be characterized further confounds the solution of the problem. Here, we demonstrate the efficacy of a novel hybrid approach to rationally design peptides with predictable affinities and specificities to inorganic materials. Our approach combines existing experimental knowledge with bioinformatics analyses, and enables design of peptides de novo with minimum effort and resources. Using this approach, we have computationally designed and experimentally verified peptides with superior binding affinities to several inorganic substrates, including quartz, hydroxyapatite and gold. Furthermore, we have designed peptides with single or multiple material specificities. Our approach is a general one and may be used to classify and design novel peptides with any arbitrary functional property, including binding to organic substrates (DNA, RNA, and other proteins), ability to spatially organize functional nanostructures, and to create hybrid molecular constructs, resulting in a wide variety of technological applications in engineering and biological fields. Supported by NSF-UW/MRSEC, ARO-UW/DURINT, NSF CAREER Award (to RS), and SPO/Turkey.
10:30 AM - T3.5
Engineering of Nanocoatings and Wires from Aligned Viruses and Structured Particles
Daniel Kuncicky 1 , Rajesh Naik 2 , Orlin Velev 1
1 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 Materials and Manufacturing Directorate, Air Force Research Laboratory, Dayton, Ohio, United States
Show AbstractWe developed a versatile single-step method for rapidly assembling tobacco mosaic virus (TMV) into nanocoatings and macroscopically ordered fibers. The TMV fibers were assembled by withdrawing with a constant velocity a meniscus containing the virus suspension over a substrate. Uniform films with long-range alignment and arrays of virus bundles were formed through a combination of shear and dewetting mechanisms. Discrete, contiguous arrays of TMV fibers were coated over centimeter length scales using only microliters of TMV suspension. The density and branching of the wire structure were controlled by varying the substrate wettability and meniscus withdrawal speed. The ability to precisely control the structure of the TMV scaffold allowed for the fabrication of architectures with advanced chemical and physical functionality. As an example, we developed a procedure where the TMV fibers were first conjugated to Au particles, followed by electroless Ag plating. This allowed for converting the virus fibers into anisotropically conductive arrays of long wires. A complimentary technique for direct patterning of single micron and sub-micron lines from particles and viruses will also be presented. A microscopic meniscus was formed at the end to a thin capillary. The controlled motion of the capillary over the substrate allows for controlled deposition of direct patterned lines. The role of capillary forces in the mechanism of direct wire assembly will be discussed. Ref.: Kuncicky, Naik and Velev, Small, vol. 2, 1462 (2006)
11:15 AM - **T3.6
Electronic Nanodevices on Biomolecules and Microorganism Scaffold
Ravi Saraf 1 , Sanjun Niu 2 , Vivek Maheshwari 1 , Vikas Berry 3 , Jennifer Kane 1
1 Chemical Engineering, University of Nebraska - Lincoln, Lincoln, Nebraska, United States, 2 , BaxterHealth Care Corp., Round Lake, Illinois, United States, 3 , Kansas State University, Manhatten, Kansas, United States
Show AbstractOrganization from nano-scale to micron-scale make biomaterials attractive scaffold to build functional structures. In this talk I will describe two types of devices where the biological structure is used to locally organize nanoparticles to form a macroscopic structure that can be intetegrated with micron scale circuitry for signal and power. The first device is a single electron device composed of a one dimensional necklace of nanoparticles templated on DNA where the particles are cemented together to promote electron tunneling. The second device is a monolayer of nanoparticle self-assembled on a live bacterium that operates as a sensor where the electron-tunneling current between the particles modulates due to the mechanical actuation of the peptidoglycan membrane in response to the external stimuli. In the second part of the talk, I will describe two “physical” device inspired by the abovementioned bio-material devices.
11:45 AM - T3.7
Amelogenin Assemblies Promote the Formation of Elongated Apatite Microstructures in a Controlled Crystallization System
George Nancollas 1
1 Chemistry, University at Buffalo, Amherst, New York, United States
Show AbstractTooth enamel and bone are biocomposites that require controlled mineral deposition at different length scales during their self-assembly to form highly hierarchical structures with unique mechanical properties. The organic matrix in forming enamel consists largely of the amelogenin protein self-assembled into nanospheres that play a pivotal role in controlling the oriented and elongated growth of highly ordered apatitic crystals during enamel biomineralization. Here we report that amelogenin dramatically accelerates the nucleation kinetics by decreasing the induction time in a dose-dependent manner in a controlled constant composition (CC) in vitro crystallization system (pH 6.80, ionic strength 0.15 mol l-1, σOCP = 1.45, 37 °C). The induction time in pure supersaturated solution, 748 ± 25 (n=4) minutes, decreased to 678 ± 22 (n=3), 523 ± 20 (n=3) and 407 ± 17 (n=3) minutes, respectively, in the presence of a 0.5, 1.25 or 5.0 μg ml-1 concentration of amelogenin. Remarkably, at very low protein concentrations, elongated and organized microstructures which are similar in appearance to apatitic crystals in enamel were promoted, at relatively low supersaturations, via interfacial structural match/synergy between structured amelogenin assemblies and apatite nanocrystallites. This suggests that in the presence of amelogenin as substrate, the charged COOH-terminal region may be important in the specific binding of the protein onto apatites, thereby lowering the nucleation energy barrier for a given Δμ (chemical potential difference between the actual state and the equilibrium state). This heterogeneous crystallization study provides experimental evidence to support the concept that amelogenin templating controls the formation of developing enamel crystals at the early stages. Understanding the protein-mediated mineralization and in vitro assembly at the bio-inorganic interface will be a useful guide for biomimetic structures constructed by self-assembly of tailor-made peptide sequences.
12:00 PM - T3.8
Interactions of biomolecules with aluminium polyoxocations and aluminium hydroxides
Carole Perry 1 , Agathe Fournier 1 , Olivier Deschaume 1
1 Biomedical and Natural Sciences, Nottingham Trent University, Nottingham United Kingdom
Show AbstractInteractions of biomolecules with aluminium species is a subject of high interest with application in fields including cosmetology, water treatment and medicine. However the nature of the interactions governing the gelation processes encountered in biomolecules/Al species systems are still to a large extent unknown. Based on the combination of characterisation techniques and synthetic procedures developed and optimised within our group, our work is focused on interaction studies of aqueous aluminium compounds with mucin and lysozyme, two proteins abundantly found in the human body. Proteins were introduced into aluminium reference systems, containing Al13, Al30 or aluminium hydroxide as the dominant species to systematically study the initial interactions. The effects of temperature and Al species to protein ratios on the systems formed were investigated by means of a wide range of analytical techniques: potentiometry, viscosimetry, conductimetry, 27Al NMR, spectrophotometry and electron microscopy.The resulting protein/Al systems were then destabilised by addition of a base in order to improve the gelation processes. The chemical and physical properties of samples taken during and after gel formation were characterised by viscosimetry, dynamic light scattering, and scanning electron microscopy. This results of this study narrow the knowledge gap existing in the explanation of the formation of hybrid Al-biomolecule composite materials from Al-containing aqueous nano-sized precursors, used daily in many industrial applications.
12:15 PM - T3.9
Biomimetic Nucleation of Hydroxylapatite Crystals on Spider Dragline Silk
Chuanbin Mao 1 , Binrui Cao 1
1 Chemistry & Biochemistry, University of Oklahoma, Norman, Oklahoma, United States
Show AbstractSpider dragline silks as natural protein fibres can be pictured as the oriented organization of protein nanocrystals (<10 nm, made of oriented beta-sheets) along the long axis with their spacing filled by amorphous protein domains. In this work, spider dragline silks secreted by Daddy long-legs spider were used as a template to nucleate hydroxylapatite (HAP, i.e., the bone mineral) from a supersaturated solution. By means of transmission electron microscopy and electron diffraction, we found that HAP crystals could be nucleated on the silks with their c-axis preferentially oriented at an average angle of 72.9 degree with respect to the long axis of the spider silks. The preferred orientation of HAP crystals is nearly identical among both different mineralized silks and different sections along the long axis of any mineralized individual silks we studied. In particular, we found that other materials such as Au and CdS crystals could also be nucleated on the spider silk, but they did not have preferred orientation at all. Thus we believe that the oriented nucleation of HAP on the silks is directly related to the structure of both spider silks and HAP. We tried to use interfacial molecular recognition theory to explain why HAP can be site-specifically nucleated on the spider silks with a controlled crystallographic orientation based on the unique features of the crystal structure of HAP and silk proteins. The mineralized spider silks will combine the good mechanical properties of the spider silks (high elasticity and tensile strength) and the biocompatibility of the HAP, and thus may be further assembled into ideal biomaterials as bone implants and tissue engineering scaffolds.
12:30 PM - T3.10
Mimics of Nacre? Aluminium Polyoxocations/ polymer composites: a model study
Carole Perry 1 , Olivier Deschaume 1 , Agathe Fournier 1
1 Biomedical and Natural Sciences, Nottingham Trent University, Nottingham United Kingdom
Show AbstractThe chemistry of aluminium polycations has recently gained renewed interest because of their multiple uses and relevance in scientific areas such as catalysis, cosmetology and medicine [1]. In addition to these fields of application, advantage can be taken of the small particle size and high charge of these defined building blocks for the self assembly of advanced composite materials. Several studies have indeed demonstrated the feasibility of Al polycation association with inorganic polyanions [2] and organic polymers [3].Our contribution details the preparation of composites based on the interactions of aluminium species and synthetic or natural polymers based on our recently developed soft, environmentally friendly and low-cost procedure for the preparation of high purity solutions of Al13 and Al30 and monodisperse aluminium hydroxide sols (20-200nm) [4]. The use of pure Al precursors has a clear advantage in materials design arising from our improved understanding and better control of materials preparation. Composite materials including those that mimic nacre have been prepared using our pure aluminium systems and different polymers including the model protein BSA. In an attempt to understand the link between bioinorganic interactions and the properties of the composites formed, the systems have been analysed using an array of techniques including 27Al NMR, UV-Vis and IR spectroscopy, together with dynamic light scattering, potentiometry, conductometry and electron microscopy. The results obtained demonstrate the stability of Al polycations upon assembly with organic polymers, their strikingly different behaviour in comparison with Al hydroxide, and the possibility of tuning the morphological and chemical properties of Al-based materials on the basis of interactions between their precursors and organic additives. The methodology developed during this work forms a robust base for further studies spanning research fields such as Materials and fundamental Inorganic Chemistry, Biology or Environmental sciences, and possesses significant potential for application to industrial products and processes.[1] Casey, W.H., Large Aqueous Aluminum Hydroxide Molecules, Chemical Reviews C, 2006, 106, 1-16.[2] Son, J.H. & Kwon, Y., New Ionic Crystals of Oppositely Charged Cluster Ions and Their Characterization, Inorganic Chemistry, 2003, 42, 4153-4159 [3] Sanson, N.; Bouyer, F.; Gerardin, C. & In, M., Nanoassemblies formed from hydrophilic block copolymers and multivalent ions, Physical Chemistry, Chemical Physics, 2004, 6, 1463-1466 [4] Shafran, K.L.; Deschaume, O. & Perry, C.C., The static anion exchange method for generation of high purity aluminium polyoxocations and monodisperse aluminium hydroxide nanoparticles, Journal of Materials Chemistry, 2005, 15, 3415-3423
T4: Student/Post-Doc Session
Session Chairs
Rajesh Naik
Carole Perry
Kiyotaka Shiba
Rein Ulijn
Wednesday PM, April 11, 2007
Room 2006 (Moscone West)
2:30 PM - T4.1
Supramolecular Assembly and mineralization of amelogenin by electrodeposition
Yuwei Fan 1 , Zhi Sun 1 , Christopher Abbott 1 , Rizhi Wang 2 , Janet Moradian-Oldak 1
1 Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, California, United States, 2 Department of Materials Engineering, University of British Columbia, Vancouver, British Columbia, Canada
Show AbstractMature tooth enamel neither remodels nor self-repairs after damage. Therefore, in vitro formation of a uniquely ordered composite similar to enamel is of particular interest. Amelogenins are the major protein components of the developing enamel matrix and their supramolecular self-assembly is crucial for the organized and elongated growth of enamel apatite crystals. In our present study we applied a newly developed electrolytic deposition system to promote the amelogenin nano-chain self-assembly and simultaneous calcium phosphate crystallization in vitro. Composite coatings of amelogenin/calcium phosphate were prepared on a cathode substrate (Si wafer), from a calcium phosphate solution with an initial pH of 4-5 at room temperature. The effects of a recombinant full-length amelogenin (rP172) and the recombinant protein without the C-terminal (rP148) on the growth and morphology of the calcium phosphate nano-composite were investigated. A potentiostat was used to control the electrochemical parameters. Following the application of electric current, the local pH around the cathode was increased and resulted in the self-assembly of amelogenin that occurred simultaneously with calcium phosphate mineralization. Transmission and scanning electron micrographs of assembled rp172 amelogenin collected from the 25mM sodium phosphate solution during electrodeposition showed uniform nanospheres and nano-chains structures, while the rP148 formed irregular aggregates. SEM observation of the surface of the nano-composite after electrodeposition, revealed organized nano-rod structures in the presence of rp172, while only nano-sized spherical aggregates were seen in the presence of rP148. Remarkably, protein supramolecular structures imaged by AFM and SEM were stable even after the demineralization of the rP172 composite coating by EDTA. These were composed of a continuous protein network (mesh-like structures) with intact chains of nanospheres. ATR-IR confirmed that the mineral phases were mainly octacalcium phosphate, but apatite and amorphous calcium phosphate were also present. Nanoindentation was tested on rP172 and rP148 composite coating. The rP172 composite coating exhibited higher elastic modulus and hardness than rP148 composite. The fracture toughnes of rP172 composite was comparable to mature enamel. In summary, by applying an electrodeposition device to control local solution pH, we have demonstrated that the full-length rP172, but not the rP148, self-assembles into nano-chain structures in solution, independent on the presence of calcium or precipitating agents such as polyethylene glycol. We therefore conclude that the 25 amino acid hydrophilic C-terminal of amelogenin is essential for the nano-chain assembly, and therefore, for calcium phosphate crystal organization. The new electro-deposition system is effective for fabrication of amelogenin/apatite composites with defined organized structures. Supported by NIH-NIDCR: DE-13414, DE-15644
2:45 PM - T4.2
Engineered Co-assembly of Biocomposite Materials from Live Cells and Inorganic Particles Using Dielectrophoresis on a Chip.
Shalini Gupta 1 , Rossitza Alargova 1 , Peter Kilpatrick 1 , Orlin Velev 1
1 , North Carolina State University, Raleigh, North Carolina, United States
Show AbstractThe co-assembly of live cells and synthetic colloidal particles could be a route to making new hybrid biomaterials, in which the biological functionality of the cells is augmented by the physical functionality of the inorganic particles. We demonstrate how such biocomposite materials can be fabricated by rapid and controlled electric field driven assembly on a chip. The process is based on dielectrophoresis (DEP), mobility and interaction of particles in AC electric fields. Live cells such as baker’s yeast and NIH/3T3 mouse fibroblasts were co-assembled with colloidal particles into freely suspended 1D "wires" and 2D membranes. Experimental observations of the DEP co-assembly dynamics showed that particles smaller in size than the cells were drawn and captured in-between the cell junctions by the electric field. The process could be modeled and understood by a combination of electrostatic field computation and MD-type of particle motion simulation. The effects of voltage, frequency, pH and electrolyte concentration will be discussed. Magnetic microparticles conjugated with lectins could be used to bind the cells irreversibly via bio-specific lectin-polysaccharide interactions. The formed membranes and wires could be manipulated by magnetic field and interfaced with on-chip electrodes. Such functional biomagnetic cell-particle assemblies may find applications in sensors, microassays, microsurgery, or as responsive biomaterials.
3:00 PM - T4.3
Bio-Inspired Mineralization from Aqueous Solutions of Zinc Nitrate Directed by the Nucleic Acid Base Adenine.
Micha Jost 1 2 , Peter Gerstel 1 2 , Joachim Bill 1 2 , Fritz Aldinger 1 2
1 Pulvermetallurgisches Laboratorium, Max-Planck-Institut fuer Metallforschung, Stuttgart Germany, 2 Institut fuer Nichtmetallische Anorganische Materialien, University of Stuttgart, Stuttgart Germany
Show AbstractZinc oxide and zinc oxide based materials or devices are promising candidates for a number of functional applications, e. g. as UV light emitters or gas sensors. The chemical bath deposition (CBD) of such materials by thermohydrolysis of zinc salts is an attractive method for the preparation of thin films and deposition products of various morphologies.[1,2] The use of biomolecules as additives in this process supresses the otherwise observed formation of elongated micron-long crystals. We found that the use of additives derived from DNA, which are known to interact with metal ions, enables us to engineer materials with interesting structural and physical properties.The thermohydrolysis of zinc salts in the presence of the nucleic acid base adenine was investigated. Deposition products from solutions containing zinc nitrate and adenine were obtained on surface-oxidized silicon substrates at a temperature of only 60°C. Particles with a diameter between 5 µm and 10 µm are formed on the substrate. SEM investigations of the deposits reveal that the particles have a "pompon-like" morphology, i.e. they are built up from platelets with a thickness in the range of 100 nm, which are radially oriented and thus lead to an overall spherical shape of the particles. XRD measurements of the deposition product indicate its crystallinity and the diffraction pattern is consistent with a structure similar to that of layered double hydroxides (LDHs) of zinc.Interestingly, in the presence of hexamethylenetetramine (HMTA) and hydrochloric acid besides zinc nitrate and adenine, different types of deposition products are obtained. The rationale of this approach is to start the process at a lower pH value and then slowly raise the pH upon heating by hydrolysis of HMTA. From such solutions a smooth, compact film with a thickness of around 700 nm is obtained on the silicon substrate. This film is covered by a 30 µm thick layer composed of smooth spherical particles about 2 µm in diameter. This system shows a very strong photoluminescence upon excitation with UV-light. As the 30 µm layer is formed through a sedimentation process, by using an "upside down" orientation of the substrate we were able to produce a smooth, compact, non-porous film.The results which will be presented show that DNA-derived biomolecules are useful as directing agents in bio-inspired mineralizations and pave the way to future investigations aiming at the DNA-programmed synthesis of zinc oxide based, functional materials.References[1] P. Gerstel, R. C. Hoffmann, P. Lipowsky, L. P. H. Jeurgens, J. Bill, F. Aldinger, Mineralization from Aqueous Solutions of Zinc Salts Directed by Amino Acids and Peptides, Chem. Mater. 2006, 18, 179.[2] L. Pitta Bauermann, A. del Campo, J. Bill, F. Aldinger, Heterogeneous Nucleation of ZnO Using Gelatin as the Organic Matrix, Chem. Mater. 2006, 18, 2016.
3:15 PM - T4.4
Microgel Coatings for Modulation of the Host Response to Implanted Biomaterials
Neetu Singh 1 , Amanda Bridges 2 3 , Julia Babensee 2 3 , Andres Garcia 2 4 , L. Lyon 1 2
1 Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 4 Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show Abstract3:30 PM - T4.5
Enzyme-Triggered Cell Attachment
Simon Todd 1 , Rein Ulijn 1 , Julie Gough 1
1 , University of Manchester, Manchester United Kingdom
Show AbstractThe developed world continues to see dramatic increases in the use of materials that interact with living cells and tissues. Understanding and ultimately controlling these interactions is of importance for a number of existing and emerging technologies, including tissue engineering and biosensing. A new challenge in this area is to engineer materials surfaces that allow for a two-way communication between biology and biomaterial. Here, we demonstrate an example of a hydrogel surface that can be switched between adhesive and non-adhesive when triggered by an enzyme.1 Our system is based on modified poly(ethylene glycol) acrylamide (PEGA) hydrogel surfaces. PEGA has been shown to have desirable properties for use as thin 3D hydrogel surfaces in biomedical applications. PEGA can be easily micropatterned, contains a high density of functional groups, provides a passive background that resists non-specific biomolecule adsorption, and is highly hydrated mimicking the natural tissue environment. 2 We also demonstrated that these surfaces could be made cell-adhesive by incorporating the well known RGD integrin cell binding sequence into the hydrogel structure (no cell adhesion observed for the RGE control).2 In this work, PEGA surfaces were modified with enzyme cleavable peptide linkers using a solid phase peptide synthesis (SPPS) approach, directly onto the micropatterned hydrogel. By using a combination of surface analysis (ToF SIMS) and fluorescence microscopy, we demonstrate that by choosing a peptide sequence to match a certain protease, hydrogel surfaces can be made responsive to target enzymes only. We then applied these systems in cell culture and demonstrate that for the first time the possibility of switching cell adhesion ON or OFF in response to an enzyme.References:1 RV Ulijn, J. Mater. Chem. 2006, 16 (23): 2217-2225. 2. M. Zourob, J.E. Gough, R.V. Ulijn. Adv. Mater. 2006, 18: 655-699
3:45 PM - T4.6
Formation of Nanostructured Crystalline Titanium Dioxide with the Aid of Polypeptides.
Matthew Dickerson 1 , Gul Ahmad 1 , Ye Cai 1 , Micheal Haluska 1 , Nicole Poulsen 2 , Sharon Jones 3 , Vonda Shephard 2 , Rajesh Naik 3 , Nils Kroger 1 2 , Ken Sandhage 1
1 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, United States
Show Abstract4:00 PM - T4.7
Towards a Molecular Level Understanding of Peptide-Mineral Interactions: a Computational and Experimental Study
Carole Perry 1 , Siddharth Patwardhan 1 , Rajesh Naik 2
1 Biomedical and Natural Sciences, Nottingham Trent University, Nottingham United Kingdom, 2 Materials and Manufacturing Directorate, Air Force Research Laboratory, AFRL/MLPJ, Bldg 651, Wright-Patterson AFB, Dayton, Ohio, United States
Show AbstractIn the search for new materials with desired functional properties and their processing technologies, scientists have focused on the sophistication exhibited by biological organisms in building materials structures as an inspirational source. This control is often a result of molecular interactions and recognition between biological molecules such as peptides and proteins and inorganic materials. In order to learn from biological processes and make use of their remarkable ability in designing novel materials, it is important to identify the rules that govern biomolecule-inorganic materials interactions at the molecular level. To this end, we have studied the effects of the structure and chemistry of inorganic materials on peptide binding. A range of materials have been synthesised including amorphous silica and crystalline zinc oxide using soft synthesis routes and the sequences of peptides binding these materials have been identified using combinatorial phage display libraries (biopanning). The results obtained suggest that materials properties control the interactions with peptides. For example, silica particles of varying sizes with similar surface chemistries bind peptides with unique but distinct sequences. Molecular dynamic (MD) simulations of the isolated peptides have been used to provide information on peptide conformations, solvent accessible surfaces and insights into the mechanisms underpinning binding. Model studies of mineral formation in the presence of the peptides identified by biopanning show that these peptides affect a range of materials properties including growth rates and morphologies. It is believed that the results obtained will increase our understanding of biomolecule-inorganic mineral interactions and this knowledge will be utilised to develop novel functional materials and new synthetic approaches to such materials.
4:15 PM - T4.8
Does architecture of an additive have an important role to play in the precipitation and dissolution of silica?
Carole Perry 1 , Graham Tilburey 1 , Siddharth Patwardhan 1
1 Biomedical and Natural Sciences, Nottingham Trent University, Nottingham United Kingdom
Show AbstractThe stability and chemistry of silicic acid and silica is important when considering the impact that the dissolution and precipitation of silica has on Global biological and geological processes. The ability of some aquatic organisms such as diatoms to deposit biosilica cell walls in an environment that is undersaturated with respect to the silica precursor (silicic acid) is intriguing. It has been found previously that a number of organic molecules can enhance the rate of silica formation when present in supersaturated solutions of silicic acid and that organic ligands and inorganic ions can also affect the dissolution of silica and silicates. In this contribution, we investigate the role of the architecture of organic molecules, some derived from biosilicifying organisms, in the precipitation and dissolution of silica. We have studied the stability of a range of silica species with and without the presence of organic additives and identified silica species that are active in the presence of additives. Some small chain nitrogen containing molecules exhibit silica precipitating abilities even for globally undersaturated silicic acid solutions, which has not been previously reported. In addition, the results show that polyelectrolytes affect the stability of silica species that results in increased rates of dissolution. In another series of experiments, we have studied the influence of amine architecture on silica materials formation. Variation in amine architecture led to the generation of a range of microscopic to macroscopic amorphous and crystalline silicon-containing novel hybrid materials. The relationship between the structure of the material formed and the architecture of the amine used has been explored using a range of techniques including X-ray diffraction, FTIR, solid state NMR spectroscopy, Electron microscopy and gas adsorption analysis.
4:30 PM - T4.9
Colorimetric response of peptide coated gold nanoparticles.
Joseph Slocik 1 , Jeffery Zabinski 1 , Rajesh Naik 1
1 Materials and Manufacturing Directorate, Wright Patterson AFB, Wright-Patterson AFB, Ohio, United States
Show AbstractColorimetric assays involving gold nanoparticles functionalized with biomolecules have proven to be effective for the detection of DNA, metal ions, and bacterial toxins. Although in each case, a single recognition event is responsible for a defined color change, which ultimately underutilizes the large spectral range of gold nanoparticles. Alternatively, peptides represent excellent sensing elements for vapors, chemical and biological targets, radioactive markers, and small molecule agents; and when incorporated with gold nanoparticles, offer a colorimetric means for detection of multiple targets based on representative color shifts. In this study, we survey the colorimetric response of peptide coated gold particles to various metal ions. Different color shifts provide a unique indicator for binding to a specific metal ion based on various aggregate sizes.
4:45 PM - T4.10
PEG based enzyme-responsive hydrogel particles for treatment of chronic wounds
Nurguse Bibi 1 , Julie Gough 1 , Rein Ulijn 1
1 School of Materials, The University of Manchester, Manchester United Kingdom
Show AbstractEnzyme-responsive materials (ERMs) are a new class of smart materials that undergo macroscopic transitions when triggered by selective catalytic actions of enzymes. In recent years, high levels of proteolytic enzymes that degrade vital tissue proteins required for normal healing have been reported in chronic wounds; and these wounds cause the deaths of millions per year. This study shows the development of an enzyme responsive hydrogel to mop-up excess enzymes by exploiting polymer collapse within chronic wounds to promote the wound healing process of these wounds. We have demonstrated the entrapment of enzymes into PEGA (polyethylene glycol acrylamide) beads that have been modified with charged protease-specific enzyme cleavable peptide linkers (CECPL) using standard solid phase peptide synthesis and Fmoc-chemistry. The swelling and accessibility of the PEGA beads was examined at different buffer concentrations and pH values using an optical microscope. Under the influence of pH, the charged residue was found to attract and allow accessibility of an oppositely charged protease into PEGA beads. We have found that the proteases are able to recognise and cleave the peptides bonds of the CECPL into cleaved products using HPLC. Enzyme entrapment was analysed using confocal fluorescence microscopy and the decrease in enzyme activity using a commercially available fluorescence substrate of the corresponding enzyme. Our approach utilises the collapsing property of the hydrogel PEGA beads to entrap the excess proteases in chronic wounds. The uniqueness of this approach is that once the charge of the CECPL is cleaved off, the proteases are entrapped within the beads they are unable to leak back into the wound as the pore size of the PEGA beads collapses.
5:00 PM - T4.11
Understanding the Blood Response to Foreign Materials for the Rational Design of Hemostatic Agents.
April Sawvel 1 , Sarah Baker 1 , Todd Ostomel 1 , Galen Stucky 1
1 Chemistry, University of California Santa Barbara, Santa Barbara, California, United States
Show AbstractThe most effective strategy for treating combat casualties is early hemorrhage control1. The traditional methods for controlling blood loss, such as the application of pressure at the wound site and the implementation of a tourniquet, do not always effectively prevent catastrophic blood loss. In recent years, there has been increasing interest in the potential of inorganic and organic based materials for use as hemostatic agents. The most promising materials developed for this purpose are chitin and chitosan based dressings, starch based polymer powders, and zeolite composite powders.QuikClot™, a zeolite composite material, remains the most effective at treating traumatic injuries, with a 100% survival rate in lethal groin injuries of swine models2. Use of this product, however, is only recommended after the traditional methods for treating severe hemorrhage have failed because hydration of the zeolite composite is highly exothermic. The host-guest properties of zeolite based materials have been exploited to attenuate the heat of hydration3, but most of this work was performed empirically, and little is known about the mechanism by which zeolite based materials induce blood clot formation.QuikClot™ is thought to arrest hemorrhage via local dehydration, which promotes coagulation by concentrating platelets and clotting proteins at the surface of the material. We have investigated the effects of zeolite composite hydration level, which can be used to control the heat release, on clotting rate and we have found that the material remains hemostatically active with changes in hydration level. The application of electron microscopy for monitoring the blood response to inorganic materials will also be discussed. It is becoming increasingly clear that concentration of the clotting factors from dehydration is not the only important mechanism of accelerated blood clot formation for zeolite based materials. For example, the zeolite composite may also present attractive surface properties for protein adhesion and platelet aggregation. A better understanding of the key material properties and of the biochemistry at the material interfaces will aid in the rational design of next generation hemostatic agents.1. H.B. Alam et al. Military Medicine, 2005, 170, 63-69.2. H.B. Alam et al. The Journal of Trauma, 2004, 56, 974-984.3. T.A. Ostomel et al. Journal of Thrombosis and Thrombolysis, 2006, 22, 55-67.
5:15 PM - T4.12
Deposition of Crystallographically Tunable Hydroxyapatite Films with a CaTiO3 Interfacial Layer onto Ti6Al4V by TEP Regulated Hydrothermal Synthesis.
Daniel Haders 1 2 4 , Alexander Burukhin 3 , Yizhong Huang 4 , David Cockayne 4 , Richard Riman 1
1 Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States, 2 Department of Biomedical Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States, 4 Department of Materials, University of Oxford, Oxford United Kingdom, 3 , Shlamberge, Novosibirsk Russian Federation
Show AbstractThe motivation of this study was to evaluate the time and temperature dependent process by which films are deposited onto Ti6Al4V substrates via hydrothermal synthesis in a 0.232 m Ca(NO3)2 - 0.232 m EDTA - 0.187 m TEP – 1.852 m KOH - H2O chemical system. The deposition process was modeled using thermodynamics software, and films were evaluated at synthesis times from 0-46 hours by XRD, FESEM, TEM, EDX, and X-ray pole figures. Thermodynamic modeling predicted a continuous two-step process that deposited CaTiO3 below 180 °C and hydroxyapatite (HA) above 180 °C. Analysis of XRD, FESEM, TEM, and EDX data confirmed this prediction. TEM and EDX revealed that a several hundred-nanometer CaTiO3 interfacial layer was maintained at synthesis times up to at least 46 hours. A 100 nm chemical transition zone, on the substrate side of the morphological substrate-film interface, revealed calcium diffusion from the surface into the substrate and titanium diffusion from the bulk to the substrate surface. X-ray pole figure analysis of the (002) crystallographic plane revealed a refinement of (002) orientation with increasing synthesis time. Together these results led to the formation of three conclusions. This is the first hydrothermal synthesis process to deposit a CaTiO3 interfacial layer and an overlying HA film in a single continuous process. Second, together, the several hundred nanometer CaTiO3 layer and the 100 nm wide Ti-CaTiO3 chemical transition zone serve as a chemical intermediate that chemically binds HA to titanium. Third, the increase of (002) crystallographic texturing with synthesis time is directly related to preferred hexagonal crystal orientation. The consequences of functionalizing the HA film surface via preferential exposure of specific crystallographic planes - through control of crystal morphology, preferred crystal orientation, aspect ratio, and crystal spacing - on protein adhesion and bioactivity are modeled and discussed.
5:30 PM - T4.13
Biomimetic Layer-by-Layer (BioLBL) assembly of Nanoparticles and Metal-Oxides.
Ken-Ichi Sano 1 , Yusuke Iimori 2 , Akira Yamamoto 2 , Kiyotaka Shiba 1
1 Protein Engineering, The Cancer Institute, JFCR, CREST/JST, Tokyo Japan, 2 Incubation Center, R&D, Pentax, Wakou Japan
Show AbstractThe biomolecules including peptides, proteins, nucleic acids, sugars, and polyamines have been receiving much attentions as tools for the bottom-up assembly of nano-structures. Besides biomolecules found in living organisms, artificial peptide aptamers, which are isolated from in vitro evolution systems, come under the spotlight. We previously isolated, using a peptide-phage system, the peptide aptamer, TBP-1 (NH2-Arg-Lys-Leu-Pro-Asp-Ala-Pro-Gly-Met-His-Thr-Trp-COOH), that binds to the surfaces of titanium (Sano, K., Shiba, K. JACS 125 p14234). Subsequently, we found that TBP-1 also binds to the surfaces of silver and silicon, but not to other metals tested, i.e., gold, platinum, copper, tin, iron, zinc and chromium (Sano, K., et al. Langmuir 21 p3090). TBP-1 also possesses the capacity to mediate biomimetic mineralization of titanium dioxide, silver and silica. Thus TBP-1 functions both as a binding molecule and as a mediator for mineralization. By taking advantage of the bifunctionality of TBP-1, we have developed a novel method for assembly of multilayered nanostructures, which we call “BioLBL” (biomimetic layer-by-layer assembly) (Sano, K., et al. JACS 128 p1717). The BioLBL enables us to pile up different nanoparticle layers that are sandwiched by mineral layers of titanium dioxide, silver and silica. We have demonstrated the feasibility of BioLBL by fabricating multilayers of cage proteins that were sandwiched by silica. In this structure, each layer contained cage proteins having distinct semiconductor nanodots. This heterogeneous multilayer may lead to the development of a novel type of a multivalued memory element. Recently, we constructed layers of cage protein that were sandwiched by layers of glass-titanium dioxide. We have observed that phase transition from vitrified titanium dioxide to anatase or rutile nanocrystalline occurred at high temperature. The multilayer of anatase nanocrystalline must explore the development of dye-sensitized nanocrystalline titanium dioxide solar cells (DSC). We are currently using TBP-1 as a binder and a mediator of mineralization. Other peptide aptamers that also have a capacity for biomineralization (aptamer for ZnO, Cu2O and germania, etc) can used in BioLBL. By combining different aptamers, we can construct elaborated structures composed of distinct nanoparticles and metal oxides. The ability to fabricate heterogeneous multilayer will enable us to develop novel types of electronic devices, battery cells, biosensors, etc.
5:45 PM - T4.14
An in vitro Mineralization Study of the Eggshell Matrix Proteins from Avian Eggshells
Ankur Duarah 1 , Gayathri Subramanyam 1 , Manjunatha Kini 2 , Suresh Valiyaveettil 1
1 Department of Chemistry, National University of Singapore, Singapore Singapore, 2 Department of Biological Sciences, National University of Singapore, Singapore Singapore
Show AbstractThe formation of an eggshell is one of the fastest mineralization processes (17-22h) known. The eggshell acts as a safe house for the developing embryo. The CaCO3 coating around the eggshell membrane has a multi-purpose role, starting from withstanding environmental stress to being chemically inert and biologically invincible. Many eggshell matrix proteins, glycoprotein and proteoglycans have been isolated, purified and is found to be active in modifying CaCO3 morphology in vitro conditions. The exact mechanisms operating during the biomineralization process is still not clearly understood.To understand the mechanism of biomineralization in avian eggshells, we have isolated, purified and characterized a few proteins from goose, chicken and quail eggshells. We have investigated the ultrastructure and the mineral composition of the eggshell using scanning electron microscopy (SEM) infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), energy dispersive scattering (EDS) and elemental analysis using the inductively coupled plasma atomic absorption spectroscopy (ICP-AAS). The soluble organic matrix (SOM) containing the biomacromolecules was extracted from the eggshell, purified by reversed phase high performance liquid chromatography (RP-HPLC) and gel filtration chromatography. The proteins were characterized using amino acid composition analysis, mass determination by matrix assisted laser desorption ionization-time of flight (MALDI-TOF), electron spray ionization mass spectrometry (ESI-MS) and N-terminal sequencing. Amorphous calcium carbonate (ACC) has been reported to be a transient precursor mineral phase in avian eggshell formation. We speculate that these cuticular nanoparticles are probably formed from the coalescence of ACC phase and may have an important role in modulating the kinetic and thermodynamic parameters directing eggshell formation. The talk will focus on the details of extraction, characterization of proteins, analyzing their activity and mechanisms of mineralization using in-vitro crystallization techniques.
T5: Poster Session: Bioinspired Materials
Session Chairs
Rajesh Naik
Carole Perry
Kiyotaka Shiba
Rein Ulijn
Thursday AM, April 12, 2007
Salon Level (Marriott)
9:00 PM - T5.1
Controlling the active assembly of nanomaterials though a chemical switch engineered into kinesin biomolecular motors.
Adrienne Greene 1 , Amanda Trent 1 , George Bachand 1
1 Biomolecular Interfaces and Systems, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractBiomolecular motors, such as kinesin, enable active transport and dynamic assembly of composite nanomaterials at hybrid interfaces. Within living systems, complex signaling mechanisms are utilized to control the function of these motors and direct the transport of macromolecules based upon the physiological needs of the cell. A significant challenge in applying kinesin-based transport systems to active materials assembly is the inability to regulate motor protein function while maintaining the energy supply. The objective of this project was to introduce an engineered chemical switch into kinesin biomolecular motors to control motor function in synthetic materials and systems. Kinesin motors were genetically mutated to create a zinc-binding domain in the neck linker region of the protein. When zinc is bound to this neck-linker region, the functionality of the motor protein is inhibited. By altering the position of the zinc-binding domain, five distinct motor proteins were genetically mutated. Sequencing of these mutations confirmed the presence of the metal ion binding domain. Three of the five mutations indicated preserved functionality of the kinesin motor protein, as evidenced by the catalysis of ATP and the active transport of microtubule filaments in inverted motility assays. One of the five mutations demonstrated successful inhibition of kinesin motility by binding divalent metal ions (e.g., Zn2+, Ni2+, Cu2+, and Co2+). To restore kinesin motility, a variety of chelators including 1,10 phenanthroline, cysteine, and nitrilotriacetic acid were used to remove the divalent metal ions out of the system. Preliminary analyses indicate that the stability of the mutant kinesin can support repeated cycles of metal addition and chelation (i.e., on/off cycles). These data demonstrate the ability to control kinesin function in synthetic systems through the use of a chemical switch genetically engineered into the kinesin biomolecular motor. Future implications of chemical regulation in active transport systems include the ability to locally control motor protein functionality and direct active transport and assembly processes by electrochemically changing the valency of the metal ions using a scanning probe tip or integrated microelectronic systems.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.
9:00 PM - T5.10
Carbon and steel surfaces modified by Leptothrix discophora SP-6: characterization and implications
Tuan Anh Nguyen 1 , Yuzhuo Lu 1 2 , Shizhe Song 2 , Xianming Shi 1 2
1 , Western Transportation Institute, Montana State University, Bozeman, Montana, United States, 2 , School of Materials, Tianjin University, Tianjin China
Show AbstractLeptothrix discophora SP-6, a type of manganese(Mn)-oxidizing bacteria, was found to accumulate Mn oxides from the aqueous environment and thus play an important role in microbiologically influenced corrosion by increasing the electrochemical potential of steel and other metals. Similarly, this bacteria was found to modify the surface of glass carbon in aqueous solution and increase its potential. In the latter case, biomineralized Mn oxides can be used as cathodic reactants for a novel microbial fuel cell. The biofilm formation and biomineralization processes were studied using electrochemical (OCP and EIS), biological, and surface analytical (FSEM/EDS and XPS) techniques. The structure and chemistry of the biomaterials formed on the substrate surface were examined as a function of the pretreatment of the substrate surface, applied polarization stimulus, growth time, among other factors. The research findings are expected to shed light on the fundamental interactions between the bacteria and the substrate surface and help advance the knowledge base needed for the application of a promising bio-cathode fuel cell.
9:00 PM - T5.11
Virus-templated Assembly of Biocomposite Nanowires
L. Andrew Lee 1 , Derrick Bell 1 , Zhongwei Niu 1 , Mike Bruckman 1 , Byeongdu Lee 2 , Qian Wang 1
1 , University of South Carolina, Columbia, South Carolina, United States, 2 , Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractThe introduction of biological elements into materials synthesis yielded highly ordered and programmable structures. For example, the genetic programming of bacteriophage has been used to guide the formation of long-range ordered systems. Viruses, ferritin, heat shock proteins, and enzyme complexes serve as inspirational materials that have been utilized as templates for inorganic nanoparticle synthesis and aligning various materials into nanosized wires, rings, fibers, and films. Tobacco Mosaic Virus (TMV) arranges 2130 coat protein subunits in a helical structure. Recently, we have demonstrated that native Tobacco Mosaic Virus (TMV) can be co-assembled with aniline to give one-dimensional nanowires. Here, we utilize coat protein subunits of TMV to produce monodispersed, micron-length biocomposite nanofibers stabilized by in situ surface polymerization of aniline. Our studies confirm that the conformational switch of the coat protein assemblies from stacked disks to a helical configuration is a key factor for such assembly process. In addition, using different doping reagents, conductive TMV-polyaniline composite nanowires can be readily produced.
9:00 PM - T5.12
Piezoelectric Inkjet Printing of Biomaterial Templates.
Leila Deravi 1 , Sarah Sewell 1 , Aren Gerdon 1 , Jan Sumerel 2 , David Wright 1
1 Chemistry, Vanderbilt University, Nashville, Tennessee, United States, 2 , Dimatix, Inc., Santa Clara, California, United States
Show AbstractPiezoelectric inkjet printing is a powerful non-contact, non-destructive rapid prototyping technique used for processing materials. A MEMs constructed printhead uses a patterned PZT (Pb(Zr0.53Ti0.47)O3) piezoelectric transducer bonded to a silicon diaphragm to generate acoustic energy, driving the drop formation. This novel method of materials deposition can be used to immobilize a variety of biomaterials, while retaining their original biological activity. Coupled in conjunction with the sensitivity of the quartz crystal microbalance (QCM), the average weight of one drop of printed material was calculated. Regardless of the pattern specified or the solution printed, piezoelectric inkjet printing reproducibly formed sub-20 pL drops with minimal evaporation post deposition, ensuring that this method for materials deposition is highly reproducible for small-scale area fabrication. The accuracy and versatility of this printing method has been demonstrated through the microscale patterning of several biological, hybrid composite materials, including biological templates for metal oxide growth.
9:00 PM - T5.13
Propulsion of Platinum Coated Polystryene Microsphere by an Asymetric Distribution of Reaction Products.
Jonathan Howse 1 , Richard Jones 1 , Ramin Golestanian 1
1 Physics and Astronomy, Sheffield University , Sheffield United Kingdom
Show AbstractIn the current miniaturization race towards small motors and engines, a rapidly expanding subdomain is the quest for autonomous swimmers, able to move in fluids which appear very viscous given the small length scales (low Reynolds Number). Nature propels objects at low Reynolds numbers using methods very different from the propulsion systems exploited by man at the macroscale, such the flagella of E.coli. Robotic microswimmers that generate surface distortions is one such artificial system (e.g. by mimicking sperms), but it seems equally interesting to try to take advantage of physical phenomena that become predominant at small scales. Interfacial “phoretic” effects (electrophoresis, thermophoresis, diffusiophoresis) are a natural avenue given the increased surface to volume ratio. Very recently, in line with earlier suggestions of self electrophoresis of objects that would be able to generate an electric field around them, many experimental reports have appeared of heterogeneous objects (rods of hundreds of nanometers to centimetres length) swimming using different catalytic or reactive chemistry at their different ends. Many mechanisms may be responsible for the observed motions, but phoretic mechanisms are high on the list in many cases. We present experimental data for the reaction-driven propulsion of small platinum coated polystyrene microsphere in solutions of hydrogen peroxide. The data obtained is compared to the theoretical behaviour for such particles. The motion of the particles is driven by an asymmetric distribution of reaction products generated by the catalytic breakdown of fuel at the surface of the microsphere. The propulsive velocity of the device is determined as well as the scale of the velocity as a function of the concentration of the fuel. The displacement as a function of time has been determined and has allowed for the calculation of diffusion coefficients, rotational diffusion coefficients, and particle velocities. The behaviour of ferromagnetic particles undergoing similar processes in a constant magnetic fields as well as the possibility of wholly biological enzymatic propulsion will also be discussed.
9:00 PM - T5.14
Wear in Active Nanosystems Powered by Biomolecular Motors.
Yoli Jeune 1 , Henry Hess 1
1 Materials Science and Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractThe degradation of static nanosystems, such as nanoparticles, is frequently characterized by chemical processes, e.g. oxidation, as well as by mechanical processes, that is wear and tear. Active, dynamic nanosystems generate their own internal motion and mechanical forces, which can be expected to lead to wear of the components. We have observed, for the first time, wear caused by mechanical forces generated by molecular motors. Our experimental setup consists of surface-adhered kinesin motor proteins transporting functionalized microtubules. This system can be employed as a nanoscale transporter, often termed “molecular shuttle”. By imaging microtubule number and distribution over time, we can detect the impact of motor activity on the system. We find that over a time period of hours, active motors cause frequent microtubule breakage. In contrast, this degradation mechanism is absent if the kinesin motors are not active. We will present a detailed study of the degradation process and discuss the implications for technological and biological nanosystems.
9:00 PM - T5.15
Infiltration of Microparticulate Bioglass® into Etched and Bonded Dentin.
Diana Zeiger 1 , Sally Marshall 1 , Kuniko Saeki 1 , Venu Varanasi 1 , Larry Watanabe 1 , Grayson Marshall 1
1 Preventive and Restorative Dental Sciences, University of California, San Francisco, San Francisco, California, United States
Show AbstractMillions of dental restorations are placed annually, many of which involve adhesive resin bonded to dentin. A major disadvantage of bonding treatments is leakage, which weakens the bond and reduces the lifetime of the restoration. It may be possible to modify the interface to reduce leakage. Objective: Test the hypothesis that microparticulate Bioglass® can be integrated into the resin-dentin bonding process and that its reactions when exposed to simulated body fluid (SBF) will decrease leakage. Methods: The coronal dentin of human third molars (N=6) was exposed by polishing with SiC paper through 320 grit, after which the dentin was etched with phosphoric acid (35%) gel etchant for 15 sec and rinsed with deionized water for 15 sec. A slurry of 40 % (w/v) Bioglass® (average particle size ~1 μm) in ethanol was placed on top of the sample, which was then vacuum-aspirated for one min in an occlusal to apical orientation. Adhesive was applied and light-cured per manufacturer’s instructions, then two layers of composite were applied over the adhesive and light-cured. Samples were stored in SBF at 37°C. Leakage was evaluated as follows: serial slabs 0.9 mm thick were cut from teeth, which were coated with nail polish to within 1 mm of interface. Bonded interfaces were soaked in 50% (w/v) silver nitrate for 2 hours, developing solution for 4 hours under fluorescent lights, and rinsed. Nail polish was removed from the side of interest, which was polished through 1200 grit. Additionally, treated (vacuum-aspirated and bonded to composite) whole teeth were either cryofractured or embedded in Stycast resin, cross-sectioned longitudinally, polished through 0.3 μm diamond, fixed with sodium cacodylate and glutaraldehyde, then dehydrated through an ascending series of ethanols and dried in hexamethyldisilazane. Specimens were examined by scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDX) using a charge-free anticontamination system (CFAS) in backscatter mode. Results: X-ray maps of cryofractured samples showed that microparticles of Bioglass® infiltrated etched dentin to a depth of ~ 5-10 μm and were held in place by adhesive resin; the resin was also able to permeate dentin to form an apparently normal hybrid layer. After one week’s storage in SBF, X-ray maps showed reduced penetration of silver into adhesive/hybrid layer of Bioglass®-treated teeth compared to negative controls. Silicon was also evident in the adhesive/hybrid layer of Bioglass®-treated teeth, as were increased levels of calcium and phosphorus. Conclusions: Bioglass® powder may be effectively integrated into the resin bonding process while still allowing the resin to permeate dentin and reduce leakage from storage in SBF. Support: NIH/NIDCR Grant P01DE09859.
9:00 PM - T5.16
Design and Fabrication of a Bioinspired Encapsulated Artificial Hair Cell Sensor
Maryna Ornatska 1 2 , Sergiy Peleshanko 1 2 , Michael McConney 1 , Nannan Chen 3 , Craig Tucker 3 , Jonathan Engel 3 , Sheryl Coombs 4 , Chang Liu 3 , Vladimir Tsukruk 1 2
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Materials Science and Engineering, Iowa State University, Ames, Iowa, United States, 3 Electrical and Computer Engineering , University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 4 Biological Sciences, Bowling Green State University, Bowling Green, Ohio, United States
Show AbstractHighly sensitive flow receptors found in the lateral line of fish have inspired the design of micromachined artificial hair cell sensors. This report describes the investigation of a gelatinous structure, the cupula, covering hair cells in the lateral line system of fish and fabrication of a hydrogel-capped, micromachined hair sensor. Results of micromechanical characterization of biological and biomimetic hydrogel cupulae demonstrate that physical properties of the photocured hydrogel cupula are similar to that of the biological analog. Model experiments in steady flow and with oscillating dipole showed that presence of the hydrogel cap significantly improves sensitivity of the microfabricated flow sensor. These findings support the concept that the cupula serves as an important mechanotransduction element.
9:00 PM - T5.17
Diameter Controlled Metallic Nanowires on an Alpha Synuclein Template
Sonal Padalkar 1 2 , Robert Colby 1 2 , Parijat Deb 1 2 , Kara Cunzeman 1 , John Hulleman 3 , Jean-Christophe Rochet 3 , Eric Stach 1 2 , Lia Stanciu 1 2
1 Material Science and Engineering, Purdue University, West Lafayette, Indiana, United States, 2 Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana, United States, 3 Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana, United States
Show AbstractThe fabrication of new nanostructured materials from the bottom up technique is critical for the efficient design of complex nanodevices. The present research demonstrates the capacity of the alpha synuclein protein to self assemble into nanofibers of 8 nm in diameter and 500 nm – 1 μm in length, which have been used as templates for the synthesis of silver and platinum nanowires. The nanowire diameter has been successfully controlled, from 15 – 125 nm, by varying the pH of the metallic solution and the reduction time thereby enabling precise control over the lateral dimension of the metallic nanowires. Further, conductivity measurements have been performed on individual nanowires to prove their electrical continuity. The integration of proteins in the synthesis of metallic nanowires with controlled diameter makes the present approach of great interest for fabrication of metallic interconnects between building blocks in nanocircuitry.
9:00 PM - T5.18
Protease-Responsive Microparticles for Capture/Release
Tom McDonald 1 , Rein Ulijn 1
1 Manchester Interdisciplinary Biocentre (MIB), University of Manchester, Manchester United Kingdom
Show AbstractResponsive polymer hydrogels are becoming an increasingly important area of research due to their biocompatibility. Poly(ethylene glycol) acrylamide, PEGA was initially developed for solid phase peptide synthesis [1] (SPPS) due to its excellent swelling properties in organic solvents. The material was also found to swell in aqueous solvents and has excellent enzyme compatibility. The material is therefore ideally suited for use in combinatorial library synthesis and biological analysis (on-bead screening). [2] Earlier results from our group demonstrated that PEGA can be used as an enzyme-responsive material whereby carefully designed peptides act as the stimuli-responsive elements. [3, 4] PEGA beads that are commercially available are between 100-500 µm in diameter. For future applications in automated screening and in drug delivery much smaller particles are required, giving rise to faster response times and possibilities of automated analysis using a cell sorter.Hence, it is the aim of this work to develop micron-sized PEGA enzyme-responsive particles. We will show that the microparticles can be formed with a mean diameter less than 20 µm (the size of biological cells). Using fluorescent labeling and two-photon microscopy we show that these particles have a homogeneous distribution of amine groups for functionalisation. The particles could be modified with a range of peptides, that carry different protease recognition sequences and responsive elements (charged residues). HPLC analysis combined with two-photon microscopy confirmed that the microparticles are compatible with enzymes and enzyme reactions are faster compared to those on conventional macro beads. Peptide elements could be designed to favour particle swelling or particle collapse upon enzyme action- thus demonstrating the versatility of the system.1. M. Meldal. Current Opinion in Chemical Biology 2004, 8:238–244 2. M. Meldal. QSAR Comb. Sci. 24, 2005, No. 10, 1141 – 11483. P.D. Thorton, G. McConnell, R.V. Ulijn. Chem Comm. 47, 2005, 5913-5915.4. R. J. Mart, R. D. Osborne, M. M. Stevens and R. V. Ulijn. Soft Matter, 2006, 2, 822–835.
9:00 PM - T5.19
Structural and Mechanical Characterization of a Natural Multiscale Composite - Bamboo
Xiaodong Li 1 , Linhua Zou 1
1 Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina, United States
Show AbstractBeing a typical natural material, bamboo is one of the most extensively referenced model for the biomimetic design of composites. The structure and mechanical properties of bamboo, in particular at the nanoscale, are still, to a large extent, unknown. Here we present the atomic force microscopy structural and nanoindentation mechanical characterization of ground parenchyma cells and vascular bundles (including metaxylems, phloems and fiber caps) in a bamboo culm. We found that the cell walls of bamboo fibers are composed of nanoscale grains (particles) of cellulose. Hardness and elastic modulus of individual constituents in the bamboo culm were measured by nanoindentation. The strengthening and toughening mechanisms of bamboo are also discussed.
9:00 PM - T5.2
Characterization and Quantification of Gold Binding Peptide Monolayer Formation on Au(111) via Time-Lapsed AFM.
Christopher So 1 , Urartu Seker 2 , Candan Tamerler 1 2 , Mehmet Sarikaya 1
1 Materials Science and Engineering, University of Washington, Seattle, Washington, United States, 2 Molecular Biology and Genetics, Istanbul Technical University, Instanbul Turkey
Show AbstractInorganic binding peptides offer an attractive biological avenue as robust linkers for the immobilization of genetically tagged biomolecules as well as the display of chemical functionalities on specific material surfaces. The three-repeat moiety of Gold Binding Peptide-1(3RGBP1) has been shown to bind avidly to particular orientations of crystalline gold lattices such as the (111) face. To characterize the mode and efficiency of binding to this surface, ex-situ time-lapsed atomic force microscopy (AFM) experiments were carried out on (111) gold for coverage analysis to quantitatively interpret the kinetics of peptide assembly and to correlate the data to observed growth morphologies. Trials were performed using a minimally invasive protocol to preserve the peptide’s native state of assembly for imaging. Kinetic experiments were first performed with a 1.0 ug/mL starting concentration to observe the change in morphologies and equilibration time on the surface. This time was then used to observe assembly coverages under various concentrations in order to determine kinetic constants using the Langmuir isotherm. Assembly processes at 1.0 ug/mL appear to reach an equilibrium point above 400 seconds where morphologies remain similar as well as area coverage. Peptide assembly is observed to initially adsorb as globular domains, which then form branched fragments with complex networking in increasing coverage until equilibrating at >90% on the surface. For experimental validation, the kinetic data was correlated to previously found quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) spectroscopy data published under similar conditions. Coverage trends from the concentration-varied experiment show good correlation to Langmuir fitting while approaching coverages of 90% as seen in high concentration SPR and QCM data. 3RGBP1 was found to have an average Keq of 1.021x10^7 M-1 from the observable AFM coverages, comparable to 1.12x10^7 M-1 from in-situ QCM experiments.
9:00 PM - T5.21
Rapid Peptide-induced Formation of Phase-Pure Crystalline Multicomponent Oxides from Aqueous Precursor Solutions at Room Temperature.
Gul Ahmad 1 , Matthew Dickerson 1 , Benjamin Church 1 , Eric Ernst 1 , Ye Cia 1 , Sharon Jones 3 , Rajesh Naik 3 , Melanie Tomczak 3 , Jeffrey King 1 , Christopher Summers 1 , Nils Kroger 1 2 , Kenneth Sandhage 1
1 Material Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Biotechnology Group, Materials and Manufacturing Directorate, MLJP, Air Force Research Laboratory, , Dayton, Ohio, United States, 2 School of Chemistry , Georgia Institute of Technology, Atlanta, Georgia, United States
Show Abstract9:00 PM - T5.23
Structure and Mobility of 1-D Lipid Bilayers on Silicon Nanowires
Julio Martinez 1 2 , Jay Huang 1 3 , Alexander Artyukhin 1 2 , Pieter Stroeve 2 , Jiann -Wen Ju 3 , Olgica Bakajin 1 , Aleksandr Noy 1 , Donald Sirbuly 1
1 Biosecurity and Nanosciences Laboratory, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Department of Chemical Engineering and Material Science, University of California Davis, Davis, California, United States, 3 , University of California, Los Angeles, Los Angeles, California, United States
Show Abstract9:00 PM - T5.24
Peptide-Based Enzyme-Responsive Polymer Hydrogel Particles
Paul Thornton 1 , Rein Ulijn 1
1 Manchester Interdisciplinary Biocentre, University of Manchester, Manchester United Kingdom
Show AbstractEnzymes, and specifically proteases, play essential roles in biochemical processes. Indeed, specific proteolytic enzymes have been identified to play key roles in disease states and are therefore valuable targets for therapeutic programs. We will describe a conceptually new approach to polymer-based enzyme-triggered release whereby the selective catalytic action of (disease specific) enzymes triggers a charge-induced swelling response in chemically cross-linked hydrogel particles, resulting in the release of physically entrapped macromolecules. This approach has a number of advantages over existing methods: it does not require covalent modification of the drug molecules, thus chemical requirements upon the drug molecules are more flexible. The polymer material itself does not disintegrate upon release and release rates will no longer be governed directly by enzyme kinetics.PEG-based cross-linked polymers were modified with peptide linkers that have a dual function: sensing and actuation. The sensing part consists of enzyme cleavable linker (ECL) and the actuation part consists of two oppositely charged amino acids that flank the ECL on either side, thus creating a zwitterionic peptide that confers no overall charge when coupled to a hydrogel. Upon selective enzyme hydrolysis of the ECL, a doubly negatively charged carboxylic acid fragment is removed, leaving a doubly cationic amine fragment tethered to the polymer, thus placing an overall positive charge on the gel and causing it to swell. By using two-photon fluorescence microscopy, we demonstrate that the molecular accessibility of macromolecules to the interior of hydrogel beads can be changed dramatically. This allows for macromolecules to be released on-demand, as demonstrated for a number of dextrans and proteins. References: 1) P. D. Thornton, G. McConnell and R. V. Ulijn, Chem. Commun., 2005, 47, 5913-5915.; R. V. Ulijn, J. Mater. Chem, 2006, 16, (23), 2217-2225.2) P.D. Thornton, R.J. Mart, R.V.Ulijn, 2006, under review.
9:00 PM - T5.25
Synthetic Control over Magnetic Moment and Exchange Bias in All-Oxide Materials Encapsulated within a Spherical Protein Cage.
Michael Klem 1 4 , Damon Resnick 2 4 , Keith Gilmore 2 4 , Mark Young 3 4 , Yves Idzerda 2 4 , Trevor Douglas 1 4
1 Chemistry & Biochemistry, Montana State University, Bozeman, Montana, United States, 4 Center for Bioinspired Nanomaterials, Montana State University, Bozeman, Montana, United States, 2 Physics, Montana State University, Bozeman, Montana, United States, 3 Plant Science, Montana State University, Bozeman, Montana, United States
Show AbstractThis work focuses on the synthetic control of magnetic properties of mixed oxide magnetic nanoparticles of the general formula Fe3-xCoxO4 (x ≤ 0.33) in the protein cage ferritin. In a biomimetic approach, variations in the chemical synthesis result in the formation of single phase Fe3-xCoxO4 alloys or intimately mixed binary phase Fe/Co oxides, modifying the chemical structure and magnetic behavior of these particles, as characterized by static and dynamic magnetization measurements and X-ray absorption spectroscopy. We have demonstrated exchange bias as a mechanism for enhancing the magnetic response as a function of temperature in a composite nanoparticle. The properties of a Co3O4/Fe3-xCoxO4 nanoparticle assembly was studied as a function of Co/Fe loading, and the ability to tune the magnetic properties, particularly the exchange bias, as a function of Co loading was also demonstrated. This work illustrates the use of a biomimetic synthesis route in the formation of magnetic nanoparticles with controlled composite ferri- and antiferro-magnetic properties.
9:00 PM - T5.26
Mimicking Enamel Formation Using Recombinant Matrices
Stefan Habelitz 1 , Wu Li 2
1 PRDS, University of California, San Francisco, California, United States, 2 Cell and Tissue Biology, University of California, San Francisco, California, United States
Show AbstractDental enamel forms through a protein controlled mineralization and enzymatic degradation process with a nanoscale precision that human engineering may be able to mimic. Biotechnology facilitates the cloning of enamel proteins and proteases, while glass-ceramics with oriented fluoroapatite (FAP) crystals provide valuable substrates to study interactions of these biomolecules with apatite mineral. In this study we used a number of recombinant enamel proteins under constant ionic solution conditions to mimic the enamel matrix and enamel synthesis in-vitro. Discs of FAP glass-ceramic were introduced as a template for apatite nucleation and crystal growth. The full-length amelogenin protein (rH175) was found to accelerate apatite crystal growth by about 25 times under specific physical-chemical conditions on (001) planes of FAP. Alignment of self-assembled nanostructures parallel to the c-axis of apatite was observed on (hk0) planes of FAP. Using a constant composition titration system, enamel proteins controlled the growth of elongated crystals of 50 nm diameter and up to 1 µm length from saturated calcium phosphate solutions of and at physiological pH comparable to mechanisms of enamel crystal formation in-vivo. Interaction of a matrix metalloproteinase, MMP-20, with amelogenin proteins immobilized on FAP glass-ceramics revealed specificity of protein binding to apatite. A model system for the synthesis of artificial enamel is presented. Supported by NIH/NIDCR R21-DE015416, R01-DE15821.
9:00 PM - T5.27
Effect of Cultivation time on Photoluminescence of Nitzschia frustulum.
Tian Qin 1 , Timothy Gutu 2 , Doohyoung Lee 1 , Jun Jiao 2 , Chih-hung Chang 1 , Greg 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 microscopic algae capable of soluble silicon uptake and biomineralization. One of the unusual properties of diatoms is that they produce an amorphous silica shell called “frustules” that consist of nano porous silica structure. This structure offers attractive probabilities for their application in optoelectronic or photonic device. A two-stage photobioreactor was used to cultivate diatom species Nitzschia frustulum under controlled conditions. Samples are taken along the cultivation time for photoluminescence (PL) property measurement. The result shows that PL intensity is cultivation time dependent. The longer diatoms were cultivated, the higher PL intensity of the frustules is. PL peak position is in the range of 440nm-500nm (2.5eV-2.8eV). TEM images of frustules taken at different cultivation time showed a quite different morphology. This might explain the cultivation time dependency of PL intensity.
9:00 PM - T5.28
Controlled silica deposition on soft-lithography fabricated poly-L-lysine templates
Randall Butler 1 , Nicholas Ferrell 2 , Rajesh Naik 3 , Derek Hansford 2 1
1 Materials Science and Engineering, The Ohio State University, Columbus, Ohio, United States, 2 Biomedical Engineering, The Ohio State University, Columbus, Ohio, United States, 3 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States
Show AbstractOrganisms like diatoms and sponges utilize organic templates to control the deposition of silica with exquisite micro- and nanoscale features. A number of previous studies have begun to unravel the array of genes, proteins, and mechanisms by which biosilicification, this in vivo synthesis of silica, is moderated. Proteins called silaffins and long-chain polyamines (LCPAs) have been isolated from the frustule of the diatom C. fusiformis. Similarly, the sponge T. aurantia synthesizes silica with a repeating array of three protein subunits (silicateins) within their spicules. A number of synthetic compounds, including the cationic polymer poly-L-lysine (PLL), have been shown to induce the deposition of silica in vitro from silicic acid solutions in morphologies that mimic naturally-formed silica. Current engineering techniques enable the fabrication of materials at the micro- and nanoscale, albeit in less intricate morphologies than those achieved in nature. While photolithography has enabled the fabrication of many microdevices, this method has several disadvantages, including difficulty in applying the process to nonplanar surfaces, high fabrication costs, and relatively few compatible materials and surface chemistries. The techniques of soft lithography have been devised to overcome several of the limitations inherent to photolithography; each of these techniques utilizes an elastomeric stamp, mold, or mask to pattern materials. Herein we describe the combination of soft-lithographic patterning and biomolecule-induced deposition to create microscale patterns of silica on a diverse array of substrates. A soft lithographic technique was used to create a sacrificial layer of the polymer poly(n-propyl methacrylate) (PPMA) on the desired substrate. Subsequently, poly-L-lysine was deposited on the substrate, after which removal of the PPMA yielded a pattern of PLL on the substrate. Exposure of the PLL template to a silicic acid solution resulted in silica deposition in the pattern spatially and geometrically controlled by the PLL. With this procedure, we have created both continuous and discontinuous silica patterns on metallic, ceramic, and polymer substrates. While morphology of the deposited silica varied between substrates, the ability to pattern silica through this templated growth was demonstrated on all investigated substrates. EDS, optical micrography, and SEM analysis verified the controlled deposition of silica on the PLL template patterns. This PLL template-mediated induction of silica formation may facilitate the incorporation of silica in new microdevices and serve as a prototype process for controlled deposition with other biomolecule-material systems.
9:00 PM - T5.3
The Nucleation of Calcium Phosphate by Amelogenin
Wendy Shaw 1 , Barbara Tarasevich 1 , Christopher Howard 1 , Jenna Larson 1
1 , Pacific Northwest National Labs, Richland, Washington, United States
Show AbstractThe ability of the enamel protein amelogenin to promote the nucleation of calcium phosphate was studied in an in vitro system involving metastable supersaturated solutions. It was found that recombinant amelogenin (rM179 and rp(H)M180) promoted the nucleation of calcium phosphate, forming octacalcium phosphate (OCP) which was followed by transformation to hydroxyapatite (HAP). The amount of calcium phosphate increased with increasing supersaturation of the solutions and increasing protein concentrations up to 6.5 µg/ml. At higher protein concentrations, the amount of calcium phosphate decreased. The kinetics of nucleation were studied in situ and in real time using a quartz crystal microbalance (QCM) and showed that the protein reduced the induction time for nucleation compared to solutions without protein. This work shows a nucleation role for amelogenin in vitro which may be promoted by the association of amelogenin into nanosphere templates, exposing charged functionality at the surface. This work was funded by the NIDCR institute of NIH. PNNL is operated by Battelle Memorial Institute for the U.S. Department of Energy.
9:00 PM - T5.30
From Peptides To Proteins: Control Of Net Molecular Charge And Hydrophilicity On The Kinetics Of Calcite Growth.
Selim Elhadj 1 2 , James De Yoreo 1 , John Hoyer 3 , Patricia Dove 2
1 CMLS, LLNL, Livermore, California, United States, 2 Geosciences, Virginia Tech, Blacksburg, Virginia, United States, 3 Biological Sciences, University of Delaware, Newark, Delaware, United States
Show AbstractMany studies have shown that proteins isolated from sites of biomineralization are unusually enriched in the acidic amino acids, notably aspartic and glutamic. This has led to hypotheses that the physiochemical properties of biomolecules influence biomineral growth. Using in situ AFM to measure kinetics of growth in characterized solution compositions, we show that low solution concentrations of aspartate and peptides promote the growth of calcite (CaCO3) by a systematic relation that scales with net molecular charge and hydrophilicity of the biomolecule.Data analysis shows the degree of enhancement is independent of amino acid sequence but not composition. The relation is general to a range of functional chemistries and explains recent reports that natural proteins isolated from abalone nacre enhance calcite growth by 5-fold over rates measured in the pure system and under constant supersaturation. The rate enhancement arises from increases in the kinetic coefficient. We interpret the mechanism to be a catalytic process whereby biomolecules reduce the energy barrier, Ek, by perturbations that displace water molecules and changes the local electrostatic potential. The result is a decrease in the energy barriers for attachment of solutes to the solid phase that represents < 8% of Ek.The new relationship suggests that peptide model systems may be scaled up to better understand the growth-modifying properties of more complex biomolecules, including proteins. These findings also provide an avenue for designing the structural and chemical features of synthetic molecules that will allow modulation of growth rates with a degree of control that is currently only expressed in biogenic minerals.
9:00 PM - T5.31
Characterization of Biopolymer Films Used in Electronic Applications
Kristi Singh 1 , Lawrence Brott 1 , Wayne Li 2 , Hans Spaeth 2 , Robert Jones 2 , Andrew Steckl 2 , James Grote 1 , Rajesh Naik 1
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States, 2 Electrical Engineering Dept, University of Cincinnati, Cincinnati, Ohio, United States
Show AbstractBiopolymers such as DNA and silk have been shown to exhibit interesting electronic properties with great potential for use in device architectures. The ability exists to form biopolymer thin films that can be incorporated into device structures with controlled film thickness ranging from nanometers to micrometers. The thin film forming capability is starting to be utilized for the incorporation of DNA into photonic devices. Recent results have demonstrated enhancement in performance in organic light emitting diodes (OLED) that incorporate DNA thin films as an electron blocking (EB) material. Techniques such as plasma enhanced chemical vapor deposition (PECVD) and ink jet printing can be used to deposit large areas with biopolymer films. Here we present various deposition techniques for DNA-based films as well as detailed characterization of the films to include AFM, SEM, and FT-IR spectroscopy.
9:00 PM - T5.32
Controlling membrane curvature: a new approach to study biological signals
Cheng-han Yu 1 2 , Raghuveer Parthasarathy 3 , Jay Groves 1 2
1 Department of Chemistry, University of California, Berkeley, Berkeley, California, United States, 2 Physical Bioscience and Materials Science Divisions, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Department of Physics, University of Oregon, Eugene, Oregon, United States
Show Abstract9:00 PM - T5.33
Controlled Synthesis of High Quality Polypeptides Thin Films via Surface-initiated Vapor Deposition polymerization
Wenwei Zheng 1 , Curtis Frank 2
1 Chemistry, Stanford University, Stanford, California, United States, 2 Chemical Engineering, Stanford University, Stanford, California, United States
Show Abstract9:00 PM - T5.34
Effect of Enzyme Treatments on the Delamination Behavior of Human Stratum Corneum.
Kemal Levi 1 , Joy Baxter 2 , Helen Meldrum 2 , Manoj Misra 2 , Eugene Pashkovski 2 , Reinhold Dauskardt 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 , Unilever Research and Development, Trumbull, Connecticut, United States
Show Abstract9:00 PM - T5.4
Novel Hydroxyapatite Binding Peptides: Selection, Characterization and in vitro Mineralization
Mustafa Gungormus 1 , Hanson Fong 1 , Candan Tamerler 1 2 , Mehmet Sarikaya 1 2 3
1 Department of Materials Science and Engineering, University of Washington, Seattle, Washington, United States, 2 Department of Molecular Biology, Genetics and Biotechnology, Istanbul Technical University, Istanbul Turkey, 3 Department of Chemical Engineering, University of Washington, Seattle, Washington, United States
Show AbstractBiomineralization is a complex process, in which hard tissues are generated through inorganic material formation regulated, mainly, by proteins. Proteins control synthesis, and nano- and micro-architectures of the hard tissues at molecular and higher dimensional levels leading to tissue-specific functional properties, Hard tissue formation is an excellent process to emulate for fabricating functional materials for practical applications in technology and medicine. In this molecular biomimetic approach in the broadest sense, proteins, either isolated from hard tissues or designed theoretically have been studied extensively to understand how they influence inorganic material formation and to fabricate materials with tailored structures. Usually a large number of proteins are involved in the process of natural biomineralization and there is still a limited knowledge about their temporal and spatial distribution during tissue formation, a major drawback in these approaches. A new approach in biomimetic materials synthesis is using genetically selected and engineered peptides that have specific affinity to desired inorganics. Here, as a first step towards designed material structures, we use hydroxyapatite (Hap) as a model to materialize calcium-phosphate-based nanoparticulates using biocombinatorially selected peptides. For this we first selected Hap-binding heptapeptides (more than 400) through a peptide-phage library and describe the identification of two peptides; one strong and one weak binder that are subsequently used in in vitro mineralization of calcium phosphate. The two candidate binders were identified by a combination of qualitative immunofluorescence microscopy and ELISA. The mineral formation kinetics was monitored using optical absorption and assays of calcium and phosphate, while the minerals formed by optical and electron microscopy and spectroscopy. To mimic the biological processes, an enzyme was use to control inorganic ions in solution. We found a drastic effect on mineral formation, e.g., orders of magnitude of accelerated growth and morphogenesis, using the strong binder compared that of weak binder or controlled case (no binder). The implications from this study will be discussed in terms of fundamentals of material formation (e.g., peptide-mineral interaction) to practical application in tissue regeneration. The research is supported by USA/ARO/UW-DURINT, NSF/UW-MRSEC and SPO of Turkey.
9:00 PM - T5.5
Selection of Specific Gold-Binding Peptides via Cell Surface Display
Marketa Hnilova 1 , Ersin Oren 1 , Urartu Seker 1 2 , Brandon Wilson 1 , Xiaorong Xiorong 3 , Candan Tamerler 1 2 , Mehmet Sarikaya 1
1 Department of Material Science and Engineering, University of Washington, Seattle, Washington, United States, 2 Department of Molecular Biology and Genetics, Istanbul Technical University, Istanbul Turkey, 3 , Intel Corporation, Santa Clara, California, United States
Show AbstractGenetic selection and identification of inorganic-binding peptides through various combinatorial displays became challenging, mainly because a potential wide spectrum of inorganic-binding peptides applications in nano- and biotechnology. Selected inorganic-binding peptides can perform a strong affinity to certain inorganic materials and thus alter their function and structure. Furthermore, in some cases, the peptides can also be used as synthesizers for inorganics in the presence of the precursors. We selected gold-binding peptides from FliTrx bacterial surface library displaying randomized dodecapeptides inserted into FLITRX chimera bacterial surface flagellin protein. Application of FliTrx bacterial library brought us certain advantages over the phage display libraries such as, less time consuming and simplifying panning procedure as well as lowering contamination risks, caused by using only one host. For the initial binding experiment of isolated clones we used fluorescent microscopy technique, previously adapted for the inorganic-binding characterization and described in our earlier studies. This technique allowed us to sort our selected gold-binding clones comparing the number of adhering cells onto the gold substrate into three groups as strong, moderate and weak. Among strong binder group we synthesized two gold-binding peptides (AuBP) and verified their binding affinities to gold and respective cross-specificities in surface plasmon resonance and fluorescence microscopy studies. We compared the binding affinities and specificities of our selected gold-binding peptides (AuBP) to the 14-aa gold-binding peptide (GBP1), isolated through cell surface display and previously used in our studies. Among the peptide binding characterizations we also tested the ability of our selected peptides to reduce gold from AuCl4- solution resulting in gold nanoparticle formation and its effect of morphogenesis. Here we aim to demonstrate the quantitative affinity and selectivity of gold binding peptides and their effect on nanoparticle morphology and morphogenesis. Supported by NSF/UW-MRSEC and ARO/UW-DURINT.
9:00 PM - T5.6
Synthesis of Au2S Nanoparticles using Apoferritin.
Keiko Yoshizawa 1 2 , Kenji Iwahori 1 2 , Kenji Sugimoto 1 2 , Ichiro Yamashita 1 2 3
1 , Japan Science and Technology, Kawaguchi Japan, 2 Material Science, NAIST, Ikoma Japan, 3 ATRL, Matsushita Electric Ind. Co., Ltd, Kyoto Japan
Show AbstractSemiconductor nanoparticles (NPs) exhibit intriguing properties and are a powerful tool for the development and fabrication of materials with novel functions. For examples, CdS, CdSe and ZnS NPs are used as a fluorescent marker due to their dramatic size-dependent alteration in optical absorption and emission spectra1. Ag2S is p-type semiconductor2 and Ag2S NP have been used as a photosensitizer for photographic purposes3. It is also expected that Ag2S NP is easily converted into An NP by the heat-treatment. If Ag2S NPs can be placed at designed positions and converted into Au NP, there will be many applications such as quantum dots catalytic NP and so on. However, there were a few numbers of publications concerning the preparation of Au2S NPs because size control of Au2S nanoparticles is difficult due to the aggregation property of Au2S nanoparticles in water4. To address this issue, we employed the cage shaped protein, apoferritin, the inner cavity of which was used to synthesize Ag2S NPs. Apoferritin has a cavity, 7 nm in diameter. In the construction of Au2S NPs using apoferritin, we mixed Au(I)-thiourea complex and apoferritin with ratio of 3000 : 1 in range from pH 6 – 9, and they were incubated at room temperature overnight5. At pH8, the core formation ratio was almost 100% and the yield of the ferritin with Ag2S is over 60 %. The diameter of synthesized Au2S NPs is about the same size with small size dispersion. Moreover, Although Au2S is generally insoluble in water, our prepared Au2S NPs can be dissolved over 100 mg / mL in water due to the water-soluble protein shell. This solubility will make it possible to place and construct nano-structures made of Au2S NPs and we are trying to apply these Au2S NPs to electronic devices.1. X. Peng, J. Wickman, A. P. Alvisatos, J. Am. Chem. Soc. 1998, 120, 5343.2. K. Ishikawa, T. Isonaga, S. Wakita, Y. Suzuki, Solid State Ionics 1995, 79, 60. 3. G. L. De Rycke, F. Henderickx, European Patent Application 1990, No.892026 13.9,4. T. Morris, H. Copeland, G. Szulczewski, Langmuir 2002, 18, 535.5. K. Yoshizawa, K, Iwahori, K, Sugimoto, I. Yamashita, Chemi. Lett. 2006, 35(10), 1192
9:00 PM - T5.7
Specific and pH Dependent Hydroxyapatite Crystal Binding Peptides
Jin Huh 3 , Yue Zhao 1 , Anna Merzlyak 1 , Seung-Wuk Lee 1 2
3 Chemistry, University of California, Berkeley, Berkeley, California, United States, 1 Bioengineering , University of California, Berkeley, Berkeley, California, United States, 2 Physical Bioscience Division, Lawrence Berkeley National Lab, Berkeley, California, United States
Show AbstractIt has been previously suggested that type I collagen acts as a structural matrix in bone, whereas nucleation of hydroxyapatite crystal, a naturally occurring form of calcium apatite and a major inorganic component of bone, is mediated by noncollagenous anionic phosphoproteins such as bone sialoproteins. However, specific molecular interactions at the protein and hydroxyapatite crystal interface, which govern crystal nucleation and growth, are still not known. In order to study specific interactions between bone crystals and proteins, a directed evolutionary technique called phage display was employed with single crystal hydroxyapatite as target material at various pH conditions. At physiological pH condition (pH 7.5), the dominant binding peptide sequences resulted in (Pro-X-Y)x repeat, which is similar to type I collagen, a major component of extracellular matrices of natural bone. In acidic pH condition (pH 5.0), the dominant binding sequences resulted in dentin phosphoproteins repeats, (Ser-Ser-Asp)x. Detailed binding study were performed to verify the binding affinity against hydroxyapatite crystals. To identify the peptide motifs in type I collagen that interact with bone crystals, the similar phage display was performed and eluted with type I collagen. The obtained peptide sequences matched similarly with the certain part of the type I collagen. The properties of the identified peptides will be discussed for the verification of specific binding and nucleation for hydroxyapatite crystals. These results will help uncovering the best binding conditions of identified peptide sequences for vitro growth of hydroxyapatite crystals.
9:00 PM - T5.8
Improved Adhesion Between Metal and Polymer Utilizing a Biomimetic Initiator.
Lesley Meade 1 , Xiaowu Fan 2 , Phillip Messersmith 2 , L. Brinson 3
1 Materials Science , Northwestern University, Evanston, Illinois, United States, 2 Biomedical Engineering, Northwestern University, Evanston, Illinois, United States, 3 Mechanical Engineering, Northwestern University, Evanston, Illinois, United States
Show Abstract Marine mussels have the remarkable ability to attach to virtually any organic and inorganic substrates under aqueous conditions. The proteins responsible for adhesion contain an abundance of tyrosine residues that are post-translationally transformed into L-3,4-dihydroxyphenyl-alanine (DOPA). The adhesive properties of DOPA are due to the catechol side chain and are oxidation dependent; DOPA forms a fully reversible bond to metal oxide surfaces, but with oxidation it forms irreversible, covalent bonds to organic substrates. We have capitalized on DOPA’s role in adhesion by using a biomimetic initiator to perform surface-initiated polymerization (SIP) from NiTi and Ti-6Al-4V wires for use in polymer composites. In our system, a DOPA-mimetic catecholic initiator is first immobilized to metal oxide surfaces and subsequently activated using atom transfer radical polymerization (ATRP) to grow polymer chains tethered to the substrate. These polymer brushes interact and entangle with the bulk polymer chains of a composite thereby increasing the interfacial strength between the metal reinforcement and the polymer matrix. We performed macro-pullout tests of wires modified by SIP of polymethyl methacrylate (PMMA) from bulk PMMA in order to quantify the change in interfacial adhesion of the modified wires. NiTi and SIP modified NiTi wires (0.127 mm diameter) were hot pressed between two PMMA sheets and subsequently pulled out at a rate of 0.5 mm/min. The SIP modified wires demonstrated an average improvement in interfacial shear strength of 240% with progressive failure in contrast to the catastrophic failure observed for the unmodified system. Our results indicate a dramatic improvement in adhesion between the reinforcing wire and polymer matrix. Thus, our method is promising for application in both macro- and nanoscale composites. We also speculate that the catechol-anchoring group will provide a strong and water resistant bond between reinforcement and matrix as demonstrated in nature, leading to improved durability of the composite in aqueous environments. The improved adhesion we have demonstrated may be well suited for use in biomedical composites where typical reinforcement modification may break down because of the aqueous environment.
9:00 PM - T5.9
Structural Characterization of Octapeptide Systems: effect of amino acid type and charge distribution
Antonios Konstantopolous 1 , Alberto Saiani 2 , Aline Miller 1
1 Manchester Interdisciplinary Biocentre, University of Manchester, Manchester United Kingdom, 2 School of Materials, University of Manchester, Manchester United Kingdom
Show AbstractDe novo designed peptides are currently attracting considerable interest due to their structural simplicity, diverse functionality and their ability to self-assemble into a variety of structures. For example it is possible to design and synthesise relatively small peptides with defined structure and function that self-assemble into 3-dimensional structures that are able to support the growth of a wide of variety of cell types. The strategy to date for the preparation of complex, self-assembled structures via peptide self-assembly has involved the ‘fishing’ for interesting materials which are then usually tested for cell attachment. This has led to only a primitive level of understanding of the factors and mechanisms underpinning the structuring and properties of such materials. Here we have focussed on examining systematically the effect of charge distribution and size of amino acid on the self assembly behaviour of a series of octapeptides that have been synthesised using solid phase peptide synthesis methods in our laboratory: FDFDFRFR, FDFRFDFR, FDFDFKFK, FDFKFDFK, FKFDFDFK and FDFKFKFD. Each system can form hydrogels under appropriate conditions of pH, ionic strength and peptide concentration and phase diagrams summarising behaviour will be presented. The structure of our systems have been elucidated using a combination of Fourier transform infra-red spectroscopy (FTIR), atomic force microscopy (AFM) and small angle neutron scattering (SANS). This work has shown that the peptides form beta-sheet rich fibrils that have circa 4-6 nm in diameter, and these can associate further along their length scales depending on the amino acid sequence. These fibrils, or thicker fibers, then become physically entangled to give rise to a 3-dimensional fibrillar hydrogel that does not flow upon inversion of the sample vial. The mechanical properties of all resulting hydrogels have been explored using oscillatory rheometry and results related back to hydrogel macrostructure. In this paper we will discuss the effect of amino acid type, charge distribution and concentration on the self-assembling behaviour of our peptide series across the length scales and propose a gelation mechanism. The structure of our materials will subsequently correlated to the mechanical properties of the final hydrogel.References1 Chen, P. Colloids and Surfaces A: Physicochem. Eng. Aspects. 2005, 1-3, 3-24.
Symposium Organizers
Rajesh R. Naik Air Force Research Laboratory
Carole C. Perry Nottingham Trent University
Kiyotaka Shiba Japanese Foundation for Cancer Research
Rein Ulijn University of Manchester
T6: Bio-Direct/Self-Assembly I
Session Chairs
Thursday AM, April 12, 2007
Room 2006 (Moscone West)
9:30 AM - **T6.1
Genetic Engineering of Novel Spider Silk Chimeric Proteins.
Olena Rabotyagova 1 , Cheryl Wong 1 , Jia Huang 1 , Carole Perry 2 , Rajesh Naik 4 , Anne George 3 , David Kaplan 1
1 Biomedical Eng, Tufts University, Medford, Massachusetts, United States, 2 , Nottingham Trent Univ, Nottingham United Kingdom, 4 , Wright Patterson Air Force, Dayton, Ohio, United States, 3 , Univ. Ilinois Chicago, Chicago, Illinois, United States
Show AbstractSpider silks possess impressive mechanical properties due to a unique combination of alanine rich crystalline beta-sheets, elastic beta-spirals and amino acid repeats that form helical structures. The goal of the present project is to exploit the novel self-assemblya nd materials properties of spider silk, while enhancing these materials with new functional features. Examples include selective mineralization and cell binding recognition. To achieve these goals, a genetic engineering strategy has been employed in which block designs are engineered into the silk by borrowing well-characterized functional domains from nature – such as cell integrin-binding peptides, silica polymerization domains from marine diatoms and dentin matrix protein from mammalian bone and teeth. For example, the R5 peptide derived from the silaffin protein of the diatom Cylindrotheca fusiformis and the human dentin matrix protein I found in bone and dentin, have been characterized for their ability to control the nucleation and growth of silica and calcium hydroxyapatite, respectively. Through genetic engineering, new spider silk chimeras were generated based on these systems, with an ability to precipitate silica or calcium hydroxapatite. To generate silk-based silica-composite proteins, the R5 peptide was fused with the consensus sequence from the major ampullate dragline silk protein I from the golden orb weaving spider Nephila clavipes. In the second protein, the carboxyl terminal domain of the dentin matrix protein I (DMP 1) was combined with the consensus repeat of the dragline. Silk-R5 and silk-DMP I chimeras were cloned, expressed and characterized. The silk-R5 controlled silica nucleation and polymerization, the silk-DMP I exhibited control of hydroxyapatite nucleation and growth. These novel mineralized silk biomaterial composites have potential applications for a variety of materials and biomaterials needs due to the combination of properties. The design strategy provides versatility for the generation of additional silk fusion proteins tailorable in terms of sequence chemistry to influence polymer molecular weight, nucleation or binding domains or additional functional features.
10:00 AM - T6.2
Creating Hydrogels from Self-Assembling Peptides
Amran Mohammed 1 , Antonios Konstantopoulos 2 , Laurent Caron 2 , Aline Miller 2 , Alberto Saiani 1 2
1 School of Materials, The University of Manchester, Manchester United Kingdom, 2 School of Chemical Engineering and Analytical Science, The University of Manchester, Manchester United Kingdom
Show AbstractMolecular self-assembly is a powerful tool for the preparation of molecular materials with a wide variety of properties. This is illustrated by the abundance of self-assembled proteins and polysaccharides encountered in Nature. Peptides are particularly promising as building blocks for a number of reasons. The natural amino acid pool consists of 20 members with different physical properties including polar, non-polar, acid, basic and aromatic groups. In addition, an infinite number of unnatural amino acids can be designed in the laboratory. Amino acids can be combined in endless different ways leading to a vast number of building blocks with different physical properties. However, the understanding of the molecular interactions and self assembly rules in these materials is still limited, consequently, the fundamental link between building block structure, mesoscopic structure and material properties has not yet been elucidated. We decided to focus our work on a set of so-called ionic- complementary peptides. Since their discovery by Zhang ionic-complementary peptides have attracted considerable attention as they represent a potential new generation of natural biomaterials for applications such as 3-D scaffolds for tissue engineering or new drug delivery vehicles. On a more fundamental aspect it is hoped that the investigation of these systems will help the understanding of amyloid fibrillogenesis in protein misfolding diseases (e.g. Alzheimer, Parkinson).The octo-peptides were synthesized in our laboratory via solid phase synthesis methods based on the following amino acids: Alanine (A), Phenylalanine (F), Lysine (K), Arginine (R), Glutamic Acid (E), Aspartic Acid (D). The following octo-peptides were synthesised: AEAEAKAK, AEAKAEAK, FEFEFKFK, FEFKFEFK, FDFDFKFK, FDFKFDFK, FDFDFRFR, FDFRFDFR. Peptide solutions were prepared by dissolving the desired quantity of peptide in distilled water at 90°C. The solutions were subsequently cooled at room temperature.Alanine based peptides did not form hydrogels in the investigated concentration range (1 to 80 mg ml-1), while all phenylalanine based peptides formed hydrogels upon cooling. The critical gelation concentration was found to be a function of the type of amino acids used as well as the charge distribution along the peptide sequence.The properties of our hydrogels have been investigated using mainly small angle neutron scattering (SANS) and atomic force microscopy (AFM). Our structural investigation revealed that AEAEAKAK and all phenylalanine based peptides self-assemble and form fibers in solution. Our SANS results could be fitted using simple rod-models and the diameter of the fibrils evaluated. AEAEAKAK was found to form thicker fibers. Our results also suggest the existence of different network structures depending on the peptide used and suggest two mechanisms for the network junctions formation: a branching mechanism and an aggregation mechanism.
10:15 AM - **T6.3
Peptide Folding and Consequent Self-assembly: Hydrogels for Cell Encapsulation and Subsequent Injectable Delivery or Other Nanotechnology
Darrin Pochan 1
1 Materials Science and Eng, University of Delaware, Newark, Delaware, United States
Show AbstractThe local nano- and overall network structure, and resultant viscoelastic and cell-level biological properties, of hydrogels that are formed via β-hairpin self-assembly will be presented. These peptide hydrogels are potentially ideal scaffolds for tissue repair and regeneration due to their ability to mimic natural extra cellular matrix. The 20 amino acid 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 short fibrils that are 3 nm wide and up to several hundred nm long 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. 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, or thixotropic, 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. Initially, 2D cultures of several cell lines (including progenitor osteoblasts, fibroblosts, and mesenchymal stem celles) proved that the hydrogel is nontoxic and sustains cellular attachment with or without serum proteins without altering the physical properties of the hydrogel. The cell-material interaction is normal in 2-D and so was extended into 3D by cell encapsulation. The ability to control the kinetics of assembly afforded the control of homogeneous cell encapsulation in 3-D. Cells were observed to remain viable in 3-D culture for extended periods of time. Peptide design for folding and self-assembly, self-assembly characterization, gel material properties, and cell-level biological properties of these peptide hydrogels will be discussed. In addition, peptide nanostructures as specific templates for inorganic nanoparticle directed assembly will be presented. The specificity of designed peptide nanostructure provides the opportunity for potential signal transduction hybrid materials to be constructed. Initial results with gold and semiconductor nanoparticles will be presented.
10:45 AM - T6.4
Understanding the Molecular Structure of Fmoc-peptide Hydrogels
Andrew Smith 1 2 , Vineetha Jayawarna 1 2 , Richard Williams 1 2 , Richard Collins 2 , Steve Eichhorn 1 2 , Aline Miller 1 2 , Alberto Saiani 1 , Rein Ulijn 1 2
1 Material Science, University of Manchester, Manchester United Kingdom, 2 Manchester Interdisciplinary Biocentre, University of Manchester, Manchester United Kingdom
Show AbstractPeptide-based self-assembled biomaterials have the potential to act as artificial extracellular matrices for wound repair and tissue engineering. We recently demonstrated that di-/tri-peptides modified with fluorenylmethyloxycarbonyl (Fmoc) form highly tuneable hydrogels that support cell culture in 3D. Understanding the process of gel formation and the nano-fibrous structures formed is important to begin the rational selection of peptide sequences to produce hydrogels with desirable properties that may ultimately be used to control and direct cell behaviour.Monitoring the environment of the large, aromatic Fmoc group was achieved by observing fluorescence emission of the molecule as the hydrogel forms. Current data indicates that the aromatic fluorenyl rings form π-π interactions. Circular dichroism has been used to investigate the peptide backbone arrangement within the hydrogel. This combined with data from FT-IR spectroscopy indicates that an anti-parallel β-sheet structure is formed in the gel state.These observations imply that the peptides hydrogen bond to one another in addition to aromatic interactions to further stabilise the system. A molecular model suggests that the self assembled structures form via a π-stacking interlocked anti-parallel β-sheet arrangement, a number of sheets twist together to form nanotubes due to the inherent twist present in β-sheets.Transmission electron microscopy confirmed formation of these nano-structures and demonstrates how variations in amino acid sequence alter the structure of the fibres formed.
11:30 AM - T6.5
Protein-like molecular self-assembly
Amalia Aggeli 1 , Neville Boden 1 , Susan Felton 1 3 , Ashley Firth 1 2 , John Fisher 3 , Eileen Ingham 3 , Jennifer Kirkham 2 , Colin Robinson 2
1 Chemistry, SOMS Centre, University of Leeds, Leeds, West Yorkshire, United Kingdom, 3 Institute of Medical & Biological Engineering, University of Leeds, Leeds United Kingdom, 2 Dental Institute, University of Leeds, Leeds United Kingdom
Show AbstractMolecular self-assembly has been attracting increasing interest from the scientific community in the recent years due to its importance in understanding biology and a variety of diseases at the molecular level, and also due to the wide range of potential applications of self-assembled nanostructures in nanotechnology. Self-assembly is an intrinsic property of peptide molecules. Learning to control precisely peptide self-assembly can be a powerful way of constructing a wealth of nanostructured materials and devices with programmable combination of functionalities appropriate for specific applications. In the SOMS Centre we have exploited the biological beta-sheet motif to design simple de novo peptides that self-assemble in a hierarchical manner to form a variety of well-defined twisted elongated nanostructures such as tapes (single molecule in thickness), ribbons (a pair of stacked tapes back to back), fibrils (a bundle of stacked ribbons) and fibres (a pair of fibrils interacting edge-to-edge). A theoretical model has been developed to rationalise this self-assembly process. At concentration typically higher than 0.5% v/v in solution these micrometer-long aggregates can form isotropic solid-like organogels and hydrogels, as well as nematic liquid crystalline fluids and gels. On solid surfaces, the tapes untwist to form single-molecule thick surface coatings. The self-assembly can be switched on or off by external chemical (eg pH and ionic strength) and physical (eg temperature, shear) triggers. The mechanical, structural and bioactive properties as well as the surface chemistry of these systems can be controlled by appropriate peptide design. The aim of our research is to understand the fundamental factors that govern peptide self-assembly and to apply this knowledge to the design of useful peptidic materials. The research is carried out by ten postgraduate students and postdoctoral researchers funded by EPSRC, BBSRC, European Union, the Royal Society, MRC as well as the chemical and pharmaceutical industry. In this presentation, progress on two particular projects will be reported. Ca+2- binding peptide gels have been self-assembled in situ in teeth caries-like lesions and have been shown to increase enamel remineralisation which can lead to tooth repair. This property has been ascribed partly to the ability of the peptide fibrils to template hydroxyapatite crystals mimicking the natural process of biomineralisation. Peptide hydrogels in physiological solution conditions have also been developed for usage as versatile scaffolds for soft tissue engineering and as injectable biolubricants in osteoarthritic joints. The biocompatibility of the peptides has been demonstrated using cell cultures.Dr Aggeli is a Royal Society University Research Fellow.
11:45 AM - T6.6
Directed Assembly of Virus Particles at Nanoscale Chemical Templates.
Sung-Wook Chung 1 , Raymond Friddle 1 , Selim Elhadj 1 , Anju Chatterji 2 , Andrew Presley 3 , Chung-Yi Chiang 4 , John Johnson 2 , Matthew Francis 3 , Angela Belcher 4 , James De Yoreo 1
1 Chemistry, Materials and Life Sciences Directorate, Lawrence Livermore Nat'l Lab, Livermore, California, United States, 2 Department of Molecular Biology, Scripps Research Institute, La Jolla, California, United States, 3 Department of Chemistry, University of California at Berkeley, Berkeley, California, United States, 4 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractViruses have recently gained attention amongst materials scientists because they can be either engineered site-specifically to present catalytic, electronic, and optically active moieties or evolved through natural selection to bind to semiconductor and metal nanoparticles. Thus they can serve as building blocks for fabricating hierarchical structures with near-molecular density of functionality, provided their assembly can be directed. Here we report results using scanned probe nanolithography (SPN) to direct organization of viruses into 1D and 2D patterns and in situ atomic force microscopy (AFM) imaging to investigate the dynamics of organization as the governing interaction variables, including pattern geometry, inter-viral potential, virus flux, and virus-pattern interaction, are varied. We have chosen three systems for this research, each of which provides a distinct motif. The first is the near-spherical icosahedral Cowpea Mosaic Virus (CPMV). The second is the wire-like M13 bacteriophage. The third is the disk- or rod-shaped Tobacco Mosaic Virus (TMV). M13 was altered to present anti-strepavadin (AS) binding sites at one end through the use of biopanning methods. CPMV was modified to present either cysteine (Cys) or histidine (His) tags at the capsid apices by direct genetic engineering. TMV was also modified to present Cys and His-tags through site-selective chemical modification to intact viral capsids. Atomically-flat gold substrates coated with SAMs of polyethylene glycol (PEG) terminated alkyl thiols were patterned with alkyl thiols terminated by maleimide (MA), nickel-chelating nitrilotriacetic acid (Ni-NTA), or biotin to bind to the Cys, Hys, or AS groups respectively. Template features had sizes ranging from 10-100nm and were separated by 50 to 1000nm. In all cases, deposition of viruses onto the templates occurred in solution where the critical control parameters including virus flux, interviral potential, and virus mobility could be controlled through the virus concentration, solution composition, and template chemistry, respectively. AFM was then used to investigate the degree of ordering, packing geometry, assembly kinetics, and cluster-size distribution both on the templates as well as the surrounding PEG-terminated regions. We show that the degree of ordering depends on all parameters chosen. For example, in the case of CPMV, as the virus-virus attraction is increased through introduction of hydrophobic effects, 2D arrays of viruses evolve from poorly-ordered, to well-ordered rhombohedral, and then hexagonally close packed assemblies and 1D patterns increase from single to multiple rows of viruses in width. Taking cues from previous work on both epitaxial and colloidal systems, we present a physical picture of virus assembly at templates which exhibits the nucleation dynamics of epitaxial systems and the condensation dynamics of colloids.
12:00 PM - T6.7
Self Assembly of Glucose Oxidase – SP1 fusion protein to enzyme nanotubes
Arnon Heyman 1 , Ilan Levy 1 , Sharon Wolf 2 , Arie Altman 1 , Oded Shoseyov 1
1 The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, and the Otto Warburg Minerva Center for Agricultural Biotechnology, The Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot Israel, 2 Electron Microscopy Unit, Weizmann Institute of Science, Rehovot Israel
Show AbstractSelf assembly is a prerequisite for fabricating nanoscale structures. Here we present a new fusion protein based on the stress-responsive homo-oligomeric protein, SP1. This ring-shaped protein is a highly stable homododecamer which could be potentially utilized to self assemble different domains and enzymes at a predicted and oriented manner. Glucose oxidase (GOx), one of the most commonly used industrial enzymes was selected. Gox gene was fused in-frame to SP1 and the fusion protein was expressed in Escherichia coli (E.coli). Gel filtration FPLC revealed a high molecular weight active complex with an approximate diameter of 50 nm, as determined by Dynamic Light Scattering. Electron microscopy observations revealed dodecamer complexes encircled by GOx enzymes. Moreover, complexes self assembled into active multienzyme nanotube particles containing hundreds of GOx per tube. This work demonstrated the value of SP1 to self-assemble long rhythmic complex nano-structures for various applications.
12:15 PM - T6.8
Structure and Function of the Directed Cooperative Assembly of 2-D and 3-D Polarized Proteorhodopsin Arrays
Hongjun Liang 1 , Gregg Whited 2 , Anna Ivanovskaya 1 , Galen Stucky 1
1 , UCSB, Santa Barbara, California, United States, 2 , Genencor International, Inc., Palo Alto, California, United States
Show AbstractMembrane proteins (MPs) play an essential role for matter, energy, and information transport to maintain life activities. The hierarchical assembly of membranes and associated MPs are abundant in biological systems for sophisticated biological functions. For example, the grana structure of thylakoid membranes in plant chloroplasts enables efficient light harvesting and development of a proton gradient for ATP production. Proteorhodopsin is the membrane protein used by marine bacterioplankton as a light-driven proton pump. Here we describe a cooperative assembly process directed by electrostatic interactions that organizes proteorhodopsin molecules into ordered arrays spontaneously. Three major interactions define the co-assembly process: pR-pR, pR-membrane and membrane-membrane interactions. We show here that the interplay of those interactions is electrostatically tunable to yield 2-D and 3-D long-range-ordered pR arrays with well-defined orientation and packing density. Understanding this rapid electrostatically driven assembly process sheds light on organizing membrane proteins in general, which is a prerequisite for membrane protein structural and mechanistic studies.
12:30 PM - T6.9
Immobilization of hexa-arginine tagged esterase onto multiwalled carbon nanotubes via electrostatic attraction
Anna Laromaine 1 , Jin Jeong 2 , Milo Shaffer 3 , Raquel Verdejo 3 , Bong Hyun Chung 2 , Molly Stevens 1 4
1 Materials, Imperial College, London United Kingdom, 2 Bionanotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology, Dae-jeon Korea (the Republic of), 3 Chemistry, Imperial College, London United Kingdom, 4 Institute of Biomedical Engineering, Imperial College, London United Kingdom
Show AbstractBiosensor applications of carbon nanotubes are being increasingly investigated. For this, the interaction of multiwalled nanotubes (MWNT) with biomolecules is of interest1,2. The strategies for the formation of biomolecule-functionalised MWNTs include physical adsorption, electrostatic attraction and covalent binding. In this study, we investigated the immobilization of a recombinant enzyme onto MWNTs via electrostatic attraction. We used three differently treated MWNTs (pristine (MWNT), acidic treated (MWNTa), basic treated (MWNTbt)), which were previously characterized by transmission electron microscopy, Raman spectroscopy and Infrared spectroscopy. Hexa-arginine-tagged esterases (Arg6-esterases, recombinant enzyme) were tethered to the MWNT through a positively charged tag in the N-terminal enzyme region as a new coupling strategy avoiding the use of any linker molecules and covalent bonding. The MWNTbt resulted in the most efficient immobilization of Arg6-esterases with sustainable enzyme activity compared to MWNT and MWNTa as characterized by AFM, SDS-PAGE, and enzymatic activity assay. It is assumed that the base treatment provides both hydroxyl and carboxyl groups on the surface of carbon nanotubes, which results in a suitable suitable surface for the immobilization of arginine tagged proteins compared to the MWNT and MWNTa. This is a new approach for formation of MWNT-protein complexes and gives new insights for biosensor or biomedical applications. References[1] Kam, N.W.S.; Dai, H. J Am Chem Soc 2005, 127, 6021-6026[2] Katz, E.; Wilner, I. ChemPhysChem 2004, 5, 1084-1104
12:45 PM - T6.10
Peptides that noncovalently solubilize carbon nanotubes
Leah Witus 1 , John-David Rocha 1 , Virany Yuwono 1 , Sergey Paramonov 1 , Bruce Weisman 1 , Jeffrey Hartgerink 1
1 Chemistry, Rice University, Houston, Texas, United States
Show AbstractFrom strong materials to electronics to biological sensors, single-walled carbon nanotubes have exciting yet elusive potential for a wide variety of commercial applications. Before carbon nanotubes’ unique electrical and mechanical properties can be put to use, methods of solubilization and functionalization must be further developed. This project presents a series of peptides that noncovalently solubilize single-walled carbon nanotubes using a design motif that combines a combinatorial library sequence to bind to nanotubes with a rationally designed section to create environmentally tuned solubility characteristics. The ability of the peptides to individually disperse carbon nanotubes without altering their electronic structure is shown by UV-Vis-NIR, fluorescence, and regular and vitreous ice cryo-TEM. Identification of the species composition of each sample by two-dimensional fluorescence reveals that one of the peptides exhibits some diameter selectivity. Additionally, one of the rationally designed modifications addresses the poor stability of noncovalently solubilized nanotube solutions by including cysteine residues for covalent crosslinking between adjacent peptides. The increased stability to dilution of carbon nanotubes coated in the crosslinked peptide is demonstrated by dialysis. This demonstrates an approach in which nanotubes may be noncovalently functionalized making them biocompatible and bioresponsive.
T7: Bio-Direct/Self-Assembly II
Session Chairs
Thursday PM, April 12, 2007
Room 2006 (Moscone West)
2:30 PM - **T7.1
Smart Peptide Nano-assemblies Functionable as Building Blocks for Nanodevices and as Nanoreactors for Room-temperature Material Synthesis.
Hiroshi Matsui 1
1 Chemistry, City University of New York, Hunter College, New York, New York, United States
Show AbstractBottom-up fabrications of electronics and sensors have been studied extensively by assembling nanometer-sized building blocks into the device configurations. While various nanocomponents have been applied as building blocks to construct nanodevices, the more reproducible methods to assemble them onto precise positions are desirable. We have been fabricating peptide-based nanotubes and functionalizing them with various recognition components such as antibody, and our strategy is to use those functionalized peptide nanotubes, which can recognize and selectively bind a well-defined region on antigen-patterned substrates, as building blocks to assemble three-dimensional nanoscale architectures at uniquely defined positions and then decorate the nanotubes with various materials such as metals and quantum dots for electronics and sensor applications. This mineralization process on the nanotube was also induced by the surface peptides that could grow those monodisperse crystals in controlled sizes at room temperature due to the peptides’ conformations and sequences. Recently, we advanced this concept to use collagen triple helices as new templates, whose chemical moiety, functionality, length, and diameter could be controlled by using recombinant technology, such an expression system of collagen fragments in E coli. Significant advantages of this system are to produce the biological wires with a uniform diameter (controllable betwen 15 nm – 30 nm) and a uniform length (controllable between 60 nm – 300 nm), and to produce them in a large quantity, both critical for real-world applications. Slight modifications in peptide sequences of the triple helices via mutagenesis change their surface properties. When metals and semiconductors were grown on the triple helices as templates, their morphologies were quite sensitive to the peptide sequences of the triple helix. For the second part of this presentation, a new biomimetic and non-classical crystallization route for room temperature-material synthesis is introduced by using peptide assemblies as catalytic and fusion nanoreactors. We developed a novel catalytic template of peptide assembly, which could cap the nucleated particles, mineralize them to BaTiO3 and β-Ga2O3 crystals, and then fuse them to grow the monodisperse nanoparticles in the peptide assembly at room temperature. In this work, we tethered the peptide assembly to incorporate the enzymatic functionality as a nano-reactor in order to catalyze the hydrolysis. In addition to the enzymatic chemical moieties of the peptide, their characteristic shape, the cavity created by capping particles, could tether the efficient dehydration pathway and the optimal surface tension advantageous for the room temperature crystal growth. This multi-functional peptide assembly could be applied for syntheses of a variety of nanomaterials that are kinetically difficult to grow at room temperature.
3:00 PM - **T7.2
Biologically-Directed Assembly for Nanophotonic Applications
David Ginger 1
1 , University of Washington, Seattle, Washington, United States
Show AbstractBiological systems excel at the synthesis, binding and assembly of structures with nanoscopic length scales. This talk will describe our efforts to capitalize on these advantages by adapting biological materials (proteins and DNA) for applications in both nanofabrication and nanophotonics. In the area of nanofabrication we describe the use of engineered surface binding proteins as functional biological inks in Dip-Pen Nanolithography (DPN) applications. For nanophotonic applications, we position chromophores at precise distances from plasmon resonant metal nanostructures using biological self-assembly with DNA linkers. We then characterize these supramolecular structures using single-particle darkfield scattering, single-molecule fluorescence spectroscopy, and single-molecule fluorescence lifetime measurements. Using this approach, we demonstrate that the fluorescence intensity of individual biologically-assembled fluorophore/metal clusters is a sensitive function of the spectral overlap between the fluorophore and the nanoparticle plasmon resonance.
3:30 PM - T7.3
Reflectin proteins from squid reflective tissues can be used to generate thin films with unique optical properties.
Wendy Crookes-Goodson 1 , Ryan Kramer 2 , Rajesh Naik 1
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States, 2 Human Effectiveness Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States
Show AbstractMany animals have specially adapted tissues that reflect light; reflection of light is used in communication and counter-predation, particularly in aquatic animals. Reflection in animal tissues is achieved through alternating layers of high and low refractive index materials, creating Bragg-like stacks. In cephalopods, such as squid, octopi, and cuttlefish, the stacks are composed of flat, proteinaceous platelets of high refractive index interspersed with cytoplasm, the low refractive index material. The platelets are composed of reflectins, highly unusual proteins with skewed amino acid compositions. Recombinant reflectin is highly insoluble, but could be extracted from E. coli inclusion bodies with 6 M guanidinium chloride and subjected to affinity purification. Purified reflectin dissolved in ionic liquids or hexafluoroisopropanol was used in the creation of thin films. These reflectin films responded to changes in humidity; both the thickness and reflective properties of the film changed rapidly and reversibly. Films cast from ionic liquid self-assembled into diffraction gratings whose spacing was dependent upon the speed of dip-coating. The synthesis and characterization of reflectin thin films will be presented.
3:45 PM - T7.4
The Clustering of Adhesive Lipids Enhances Vesicle-Vesicle Adhesion.
Robert Mart 1 , Kwan Liem 1 , Xi Wang 1 , Simon Webb 1
1 Chemistry, University of Manchester, Manchester, Greater Manchester, United Kingdom
Show AbstractOur aim is to create structurally defined aggregates of vesicles that will mimic the form and function of tissue. To do so, we design and synthesise adhesive lipids as mimics of cell adhesion molecules (CAMs) and embed them in the membranes of vesicles. The adhesive interaction used to crosslink these simple mimics of cells is the relatively weak copper(iminodiacetate)-histidine link; this interaction is similar in strength (K around 103 M-1) to natural adhesive interactions like selectin-sialyl Lewis X, which have individual strengths less than 104 M-1. Given that the localization of CAMs within lipid rafts has recently been shown to play a key role in enhancing cell adhesion, we hoped that lipid clustering would augment these individually weak links in a biomimetic manner to give tight links between vesicles. To investigate this aspect of cell adhesion, we recently developed a perfluoroalkyl-pyrene membrane anchor that enables synthetic lipids to phase separate within phospholipid bilayers in the liquid ordered (lo) phase. This motif allowed us to create lipid raft mimics; phase separated domains of adhesive lipids floating within a fluid matrix. Furthermore, the extent to which our synthetic CAMs clustered into adhesive patches on the surface of vesicles could be controlled by changing vesicle composition, allowing us to show extensive receptor phase separation significantly enhanced vesicle-vesicle adhesion. Indeed, only vesicles with adhesive patches adhered to their conjugate histidine-coated vesicles to form large heterogenous vesicle aggregates 20-80 μm in diameter. We now hope to develop this methodology to form larger biocompatible tissue mimics that are structured on a submicron scale. References: (1) S.J. Webb, L. Trembleau, R.J. Mart and X. Wang, Org. Biomol. Chem, 2005, 3, 3615-3617. (2) M. Bayati, K. Greenaway, L. Trembleau, and S.J. Webb, Org. Biomol. Chem, 2006, 4, 2399-2407. (3) R.J. Mart, X. Wang, K.P. Liem, and S.J. Webb, J. Am. Chem. Soc, 2006, DOI: 10.1021/ja0657612
4:30 PM - T7.5
Controlling the behavior of thermo-reversible protein fibrillar hydrogels for tissue engineering applications
Alberto Saiani 1 , Aline Miller 1 2 , Julie Gough 2 , Hui Yan 1
1 Manchester Interdisciplinary Biocentre, University of Manchester, Manchester United Kingdom, 2 School of Materials, University of Manchester, Manchester United Kingdom
Show AbstractRecently the ability of proteins and peptides to self-assemble into ordered supramolecular architectures on the meso- to macroscopic length scales has attracted great attention in the development of novel biomaterials due to their potential biocompatibility and biodegradability[1]. In particular, the β-sheet motif is of most interest due to its important role in the formation of protein fibrils, which can further self-organize into a three dimensional network, i.e. a protein hydrogel that is able to retain up to 97% water or biological fluid. Such protein hydrogels have been suggested to be promising candidates for biological applications such as tissue engineering scaffolds[2].Here we will show that novel thermo-reversible fibrillar hydrogels can be formed from an aqueous solution of hen egg white lysozyme by adding the reductant dithiothreitol and their properties can be controlled by varying protein concentration, reductant concentration and ionic strength of the matrix[3]. The elastic modulus of the hydrogels formed is of the same order of magnitude as the value reported for other cross-linked biopolymer gels such as actin and agarose. Micro differential scanning calorimetry experiments confirmed that the hydrogels were thermally reversible and that gelation and melting occurs through a solid-liquid like 1st order transition. Infra-red and transmission electron microscopy studies of very dilute samples revealed the presence of beta-sheet rich fibrils that were ~ 4 – 6 nm in diameter and 1 micron in length. These fibrils self-assemble along their long axes to form larger fibers that become physically entangled to form the 3-dimensional network observed in both cryoSEM and small angle neutron scattering studies. The potential to control and manipulate the gel properties has been explored by varying the protein concentration, reductant concentration and ionic strength of the matrix[4]. Results will be presented and discussed in relation to the degree of the reduction of lysozyme and differences and similarities highlighted. In addition we will present our preliminary cell culture experiments that show the gel matrix promotes cell spreading, attachment and proliferation; indicating our lysozyme gels are biocompatible and they can provide a viable support for the cells. References1. Ozbas, B; Kretsinger, J.; Rajagopal, K.; Schneider,J.P.; Pochan D.J. Macromolecules 2004, 37, 7331-7337.2. Jayawama, V.; Ali, M.; Jowitt, T.A.; Miller, A.F.; et al. Adv. Mat. 2005, 18,611-614.3. Yan H.; Saiani A; Gough, J.E.; Miller, A.F. Biomacromolecules 2006, 7(10), 2776-2782.4. Yan, H.; Saiani A; Miller, A.F. to be submitted.
4:45 PM - **T7.6
Nucleic-acid Based Devices.
Milan Stojanovic 1
1 Department of Medicine, Columbia University, New York, New York, United States
Show AbstractStarting from simple nucleic acid components, we can quickly build-up complexity. For example, using beads that can accept and release oligonucleotides we can form networks of beads capable of remote sensing and Boolean algebra. Or, we can construct beads that can sense concentrations of small molecules above threshold, and release insulin.
5:15 PM - T7.7
Structure and applications of a temperature responsive recombinant protein hydrogel based on silk- and elastin-like amino acid motifs
Lawrence Drummy 1 , Joseph McAullife 2 , Richard Vaia 1 , Rajesh Naik 1
1 AFRL/ML, Air Force Research Labs, WPAFB, Ohio, United States, 2 , Genencor International, Inc., Palo Alto, California, United States
Show AbstractProteins form the main components of many natural materials, and they can be designed to offer tailored functionality and material properties. Elastin-like polypeptide motifs exhibit a reversible hydrophilic-hydrophobic phase transition in aqueous solution and have been examined for a variety of applications, including sensors and controlled release devices. Incorporation of silk-like polypeptide segments into an elastin-like polypeptide, in defined locations, is investigated as a route to tailor the solubility and thermo-mechanical properties of the material. Silk elastin-like proteins (SELP)s come from a family of repeat sequence protein polymers that are recombinantly expressed in E. coli. The sequences of the repeat segments are derived from the crystalline regions of Bombyx mori silk (GAGAGS) as well as from mammalian elastin (GVGVP), and certain functional amino acid residues such as lysine can be inserted at regular intervals along the macromolecular backbone. SELP gels are formed by heating the protein solutions in order to induce physical crosslinking of the silk beta-sheet regions. The gels contain approximately 80-90% water by weight and can be used for encapsulation of enzymes or nanoparticles, as well as for templating composite material fabrication. During gel formation, small angle X-ray scattering (SAXS) shows intensity increases in two distinct regions of reciprocal space, verifying a hierarchical gel structure. As the sample is cooled to room temperature, one of these regions (at smaller length scales) shows reversible intensity changes as a function of temperature, while the other does not. The reversible intensity change is attributed to the swelling and collapse of the gel, while the irreversible intensity change is due to the crystalline regions formed by the silk blocks.
5:30 PM - T7.8
Incorporating both magnetic and catalytic activity into a range of self assembled protein cage architectures
Mark Allen 1 2 , Michael Klem 1 2 , Mark Young 3 2 , Trevor Douglas 1 2
1 Chemistry and Biochemistry, Montana State University, Bozeman, Montana, United States, 2 Center for BioInspired Nanomaterials, Montana State University, Bozeman, Montana, United States, 3 Plant Sciences, Montana State University, Bozeman, Montana, United States
Show AbstractProtein cage architectures have been used for the synthesis of materials having unique magnetic and catalytic properties. Incorporation of phage display peptides has allowed for the engineering and design of protein cage architectures that can be used for mineral synthesis with control over the mineral phase. Protein cages such as viruses, ferritins, heat shock proteins, and Dps proteins self assemble from structurally identical subunits to form highly symmetrical structures. Through a reversible disassembly/reassembly process the cages can be differentially modified to incorporate multiple mineral specific nucleation sequences into an individual protein cage. This symmetry breaking approach allows the simultaneous synthesis of two (or more) nano-materials (semi-conductor/alloy, or antiferromagnet/ferromagnet) constrained within the same protein cage. Interaction between these phases yields new emergent properties such as magnetic exchange interactions that can be explored. This approach is found in nature in the mixed assembly of two types of mammalian ferritin subunits, H and L. This gives rise to tissue specific populations with different ratios of subunits leading to functional changes in control of nucleation vs. particle growth. Using a symmetry breaking approach will allow the design of protein cages with greater synthetic function. This presentation will focus on the property control of materials exerted through disassembly/reassembly of symmetry broken protein cages.
5:45 PM - T7.9
Development of robust and long-lived lipid bilayer membranes through hydrogel encapsulation
Tae-Joon Jeon 1 , Noah Malmstadt 1 , Jacob Schmidt 1
1 Deaprtment of Bioengineering, UCLA, Los Angeles, California, United States
Show AbstractConsiderable recent effort has been devoted toward the development of sensors based on single molecule transport measurements of channel proteins. Although preliminary results have been very promising, further application and development of these sensors is hampered by the lipid bilayer membranes in which the proteins are incorporated. These membranes are problematic to form, extremely fragile, and short-lived (lifetimes < 1 day). We have recently developed a new method with which lipid bilayer membranes can be vibrationally isolated and stabilized, resulting in significantly longer membrane lifetime, increased mechanical stablility, and the ability to be transported. The hydrogel encapsulated membranes are created by forming a freestanding lipid bilayer membrane in the presence of a hydrogel precursor solution. The polymerization initiators in solution may then be optically or chemically activated, resulting in a self-assembled network surrounding and supporting the membrane at the molecular level. We have seen that these encapsulated membranes are more robust and long-lived than their unencapsulated counterparts as a result of the intimate hydrogel/membrane contact. We have also created cross-linkable lipids which form membranes that can bond directly to the hydrogel matrix, further strengthening the membrane and resulting in lifetimes >11 days. These membranes are of high quality and support the incorporation and measurement of single channels. We have also created these stablilized membranes within glass capillaries, lending them to a portable format. We will report these results as well as the latest work with our system attempting to further extend the lifetime of encapsulated membranes as well as the development of devices based on them.“Hydrogel-Encapsulated Lipid Membranes,” Tae-Joon Jeon, Noah Malmstadt, and Jacob J. Schmidt, Journal of the American Chemical Society 128, 42-43 (2006).
T8: Poster Session: Bio-Direct/Self-Assembly III
Session Chairs
Rajesh Naik
Carole Perry
Kiyotaka Shiba
Rein Ulijn
Friday AM, April 13, 2007
Salon Level (Marriott)
9:00 PM - T8.1
Rapid and Zeptomolar Protease Detection using Peptide-Functionalised Gold Nanoparticles
Anna Laromaine 1 , Liling Koh 1 , Muthu Murugesan 1 , Rein Ulijn 2 , Molly Stevens 1 3
1 Materials, Imperial College, London United Kingdom, 2 Materials Science Centre, University of Manchester, Manchester United Kingdom, 3 Institute of Biomedical Engineering, Imperial College, London United Kingdom
Show AbstractThe ability to control the dynamic assembly of nanostructures under physiological conditions has potential applications in biosensing and drug delivery. The optical properties of gold nanoparticles can be exploited by controlling their size and size distribution [1]. Peptides are interesting tethers for the assembly of gold nanoparticles as the availability of different amino acids allows for rational design of sequences. Proteases, are (i) chemo, regio, and enantioselective; (ii) work under mild conditions; and (iii) are involved in disease states such as HIV, Alzheimer’s disease, Hepatitis C, Candida infections and pancreatitis [2].We propose here that peptide-gold nanoparticle conjugates can be selectively dis-assembled in the presence of proteases.The protease, thermolysin, known to be selective for hydrophobic residues for P2 and non-selective for residues in the P1 position (P1-P2, where P1 is the N-terminus), is used to demonstrate this proof-of-concept [3]. Peptide, N-Fluorenyl-9-methoxycarbonyl (Fmoc)-Gly-Phe-Cys was designed with the incorporation of Cys to facilitate attachment to the gold nanoparticle surface via a gold-thiolate bond [4] and π-π interactions [5] between the Fmoc groups to cause an aggregation of peptide-functionalised gold nanoparticles. The selective hydrolysis of the Gly-Phe bond would produce a positive charge at the N-terminus, resulting in a dispersion of peptide-gold nanoparticles.TEM images of peptide-gold nanoparticles reveal an aggregated nanoparticles assembly with a plasmon resonance peak of 565nm in the UV-visible spectrum. Detection of a range of concentrations of thermolysin (7.2nM to 2.08zM) caused the aggregated blue peptide-gold nanoparticle solution to turn pinkish-red. A change in the state of aggregation was apparent after 5 min as determined from A/D ratio calculations. 7.2nM thermolysin produced a shift from 565nm to 532nm in 6 hours and TEM images revealed a well-dispersed system at 6 hours. Single molecule (2.08zM) detection was also demonstrated which produced a dispersed system in 23 hours. Controlled experiments using Fmoc-gly-d-Phe-d-Cys as the control peptide or trypsin as the control protease did not dis-assemble.We have successfully designed a protease sensor using peptide-functionalised gold nanoparticles. The sensor enables rapid protease detection with a much higher sensitivity (single molecule) than previously reported. Our approach offers dynamic control over the nanoparticle assemblies under mild conditions, which could prove useful for the development of a new class of biologically-controlled materials with applications in drug delivery and monitoring of enzymes.References[1] Chowdhury,M.H. J. Biomed.Opt. 2004;9(6):1347-1357[2] Maly D.J. ChemBioChem. 2002;3(1):16-37[3] Ron H.P.Doeze, Angew. Chem. Int. Ed. 2004;43:3138-3141[4] Niemeyer.C.M., Angew. Chem. Int. Ed;2001(40):4128-4158[5] Toledano, S. JACS. 2006;128(4):1070-1071
9:00 PM - T8.10
Protein engineering of Cellulose – Spider silk composite
Sigal Meirovitch 1 , Shaul Lapidot 1 , Hanan Stein 1 , Oded Shoseyov 1
1 The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture and the Otto Warburg Minerva Center for Agricultural Biotechnology, The Hebrew University of Jerusalem, The Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot Israel
Show Abstract9:00 PM - T8.11
DOPAminylation: versatile mussel-inspired surface modification chemistry
Haeshin Lee 1 , Phillip Messersmith 1 2 3
1 Biomedical Eng., Northwestern University, Evanston, Illinois, United States, 2 Material Sciences and Engineering, Northwestern University, Evanston, Illinois, United States, 3 Institute for NanoBiotechnology in Advanced Medicine, Northwestern University, Evanston, Illinois, United States
Show AbstractBiointerface science is an interdisciplinary research area combining material science, biological science and chemistry. A large amount of research has been conducted to develop surface modification chemistries. Silane, thiol, and plasma chemistries are the ones that have been used for modifying oxide, metals, and polymeric surfaces respectively. However surfaces that are modified by the current chemistry are still limited to defined categories which do not include composites, ceramics, papers, and a large body of polymeric surfaces such as poly(tetrafluoroethylene) (PTFE). In addition, to impose functional properties on the surfaces, they often require extensive synthetic chemistry to tether biological molecules on the surfaces. Therefore, it is necessary to develop a surface chemistry that shows surface versatility and multi-functionality. Here, we propose a simple one-step aqueous coating method called DOPAminylation. This surface chemistry is inspired by mussel adhesive proteins found in marine environment, playing an important role in an interfacial adhesive. The adhesive protein shows a repeated di-peptidyl sequence of DOPA (3,4 dihydroxylphenylalanine) and lysine that are exhaustively repeated throughout the protein. We found that dopamine, a bi-functional small molecule that has amine and catechol, which are the side chains of lysine and DOPA showed a versatile surface coating capability. We found that under oxidative conditions (pH > 7.5), dopamine surprisingly forms adherent nanofilms on virtually all natural and synthetic surfaces: metals (Au, Ag, Pt, Cu, Pd, stainless steel), oxides (TiO2, NiTi, SiO2, Quartz, Al2O3, Nb2O5), semiconductors (GaAs, Si3N4), polymers (polyethylene (PE), polystyrene (PS), polyethyletherketone (PEEK), polyurethanes, polydimethylsiloxane (PDMS), polycarbonate (PC), polytetrafluoroethylene (PTFE), polyethyleneterephthalate (PET)), and ceramics (glass and hydroxyapatite). The polymerized dopamine thin film was found to be a chemical black hole, meaning that it is reactive to a wide variety of organic species such as amine, thiol, and imidazole, and also complexes with various inorganic metals. The reactivity toward those organic functional groups serves as a convenient toolbox for biomolecular conjugations on versatile surfaces avoiding or minimizing time-consuming synthetic modifications of biomolecules. Also, metal complexation properties of the DOPAminylated thin film enable to metallize any surfaces which might potentially be useful for biomedical devices and electronics. In summary, DOPAminylation is a bio-inspired innovative surface modification chemistry, and we demonstrated surface-independent (1) silver and copper metallizations, (2) poly(ethylene glycol) conjugation i.e. PEGylation, and (3) biomacromolecule conjugations
9:00 PM - T8.12
Evolutionary Screening for Selective Sensing Materials and their Integration with a Membrane Based Chemical Sensor.
Justyn Jaworski 1 3 , Si-Hyung Lim 2 , Arunava Majumdar 2 4 , Seung-Wuk Lee 1 3
1 Bioengineering, UC Berkeley/ UCSF, Berkeley, California, United States, 3 Physical Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Mechanical Engineering, UC Berkeley, Berkeley, California, United States, 4 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractCurrent commercially available chemical sensors face a trade-off between sensitivity and selectivity. The biggest challenge for these chemical sensors is generating the selectivity of a receptor to its respective target molecule against a background of various interfering agents. Utilizing the combinatorial screening power of phage display, we have developed a recognition motif of amino acids capable of selectively binding the explosive TNT (trinitrotoluene) while remaining inactive to DNT (dinitrotoluene), differing in only a single nitro group. Our unique approach of combining selective receptors with a sensitive detection platform overcomes the above mentioned limitations by minimizing the amount of false positives detected. The sensing platform utilizes a parylene micromembrane surface stress sensor array which functions with a capacitive signal readout. Upon the parylene membrane, a layer of gold is present acting as both the second electrode of the capacitive sensor as well as the point of attachment for a monolayer coating of the target specific receptor. Previously it was demonstrated that interactions of the parylene surface receptor with a target molecule result in the membrane experiencing a surface stress attributed to the binding event. Surface stresses as low as 1mJ/m2 create a detectable deflection of the gold coated membrane producing a change in the capacitive signal. By employing phage display, we have created several receptors selective for a variety of targets. The process utilizes a large combinatorial library of M-13 bacteriophage expressing candidate receptors on the pIII region of their protein coat. The library of potential receptor-bearing phage is allowed to incubate with the target molecule, such as TNT. Non-specific binders are washed away, while specifically bound phage are eluted from the target and captured. The screening is repeated several times with increasingly stringent binding conditions until a homologous binding motif emerges. This amino acid sequence constitutes the receptor which is then created using solid-phase peptide synthesis to contain a thiolated poly (ethylene glycol) linker to provide attachment to the gold coated membrane and to reduce the response to humidity changes. Comparative binding assay data suggests levels of binding to DNT for the TNT designed peptide are on the order of non-specific interaction confirming that the designed peptide is indeed selective for the TNT target. This unique approach offers a significant advantage of versatility owing to the modular nature of the receptor layer. By utilizing evolutionary screening, we can create a receptor for a small molecule of interest, be it explosives, chemical warfare agents, pesticides, common pollutants, etc., which can then be incorporated onto the membrane based sensing platform.
9:00 PM - T8.13
Designing module structures for Lab-on-a-Chip devices integrated with kinesin/microtubule-based molecular shuttles.
Takahiro Nitta 1 , Akihito Tanahashi 1 , Motohisa Hirano 1 , Henry Hess 2
1 Dept. of Math. and Design Eng., Gifu University, Gifu Japan, 2 Dept. of Materials Sci. and Eng., Univ. of Florida, Gainesville, Florida, United States
Show AbstractNature has developed sophisticated intracellular material transportation systems with kinesin motors and microtubules. Kinesin motors convey nano-scale cargo to their destinations on microtubule networks. Inspired by this intracellular material transport, kinesin/microtubule-based molecular shuttles are designed for nanoscale transport in engineered systems. Functionalized microtubules loaded with cargo are gliding over kinesin motors coated surfaces. The microtubules are directed along pre-determined tracks to their destinations. Integration of the molecular shuttles with Lab-on-a-Chip technology may lead to devices with the channel width of sub-micrometers. Various modules of the envisioned devices, such as rectifiers, concentrators, and molecular sorters, have been constructed. However, since there is no guideline for the module designs, developments of modules of higher performance have to be carried out experimentally by trial and error. We are working on a simulation tool for designing module structures of Lab-on-a-Chip devices integrated with molecular shuttles (Nitta, Lab on a Chip, 2006). Here, we present an extended simulation method to simulate molecular shuttle movements under external forces and molecular shuttle detachments from module surfaces. The simulation method was validated by comparing the simulation results with published experimental observations. These developments enable us to simulate how a molecular sorter works and cargo loss during the transportations. Using this simulator, module structures of high efficiency and minimal cargo loss can be designed.
9:00 PM - T8.14
Effects of Biomaterials and Matrix Molecules on the Osteoblastic Differentiation of Rat and Canine Bone Marrow Stromal Cells In Vitro
Feyzan Ozdal-Kurt 1 , Ibrahim Tuglu 2 , Seda Vatansever 2 , Sait Tong 2 , Bilge Sen 5 , Ismet Deliloglu-Gurhan 4
1 Biology, Celal Bayar University, Manisa Turkey, 2 Histology and Embryology, Celal Bayar University, Manisa Turkey, 5 Dentitry, Ege University, Izmir Turkey, 4 Bioengineering, Ege University , Izmir Turkey
Show Abstract9:00 PM - T8.15
Collagen Structural Hierarchy and Susceptibility to Degradation by Ultraviolet Radiation.Medford, Massachusetts 02155 USA
Olena Rabotyagova 1 3 , Peggy Cebe 2 , David Kaplan 3
1 Department of Chemistry, Tufts University, Medford, Massachusetts, United States, 3 Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, United States, 2 Department of Physics, Tufts University, Medford, Massachusetts, United States
Show AbstractCollagen type I is the most abundant extracellular matrix protein in the human body, providing the basis for tissue structure and directing cellular functions. Collagen has a complex structural hierarchy organized at different length scales, including the characteristic triple helical conformation. In the present study, we examined the relationship between collagen structure (native vs. denatured) and sensitivity to UV radiation with a focus on changes in primary structure, local conformation, structural order, microstructure and material properties. Structural and functional changes in the collagens in film form were related to the initial conformation (native vs. denatured) and energy of irradiation. These changes were tracked using SDS-PAGE to assess molecular weight, Fourier transform infrared (FTIR) spectroscopy to study changes in the secondary structure, and atomic force microscopy (AFM) to characterize changes in mechanical properties of the films. The results correlate differences in sensitivity to irradiation with initial collagen structural state. Differences were found at the molecular (primary structure), nano and mesoscopic (conformation and supercoiling of the triple helices) and macro levels with differences in mechanical properties. Intermolecular hydrogen bonds were broken first, followed by intramolecular hydrogen bonds holding the collagen triple helix together. In general, native collagen was more susceptible to UV-254 radiation during the early stage of collagen denaturation; however, during subsequent stages which include peptide bond cleavage, heat-denatured collagen degraded to a greater extent than the native collagen. The loss of hydrogen bonds in collagen is accompanied by hydrogen abstraction through free radical mechanisms. The results suggest that the negative effects of electromagnetic radiation on biologically relevant extracellular matrices (collagen in the present study) are important to assess in the context of the state of collagen structure. The results have implications in tissue remodeling, wound repair and disease progression.
9:00 PM - T8.16
A method to generate biomimetic superhydrophobic engineering surfaces
Yilei Zhang 1 , Sriram Sundararajan 1
1 Mechanical Engineering, Iowa State University, Ames, Iowa, United States
Show AbstractSuperhydrophobic surfaces are found in many natural systems, such as leaves and human cornea. The high contact angle behavior and self-cleaning ability of these surfaces make it easy to remove contaminants and keep the surfaces clean. It is well known that surface roughness plays an important role for such surfaces to achieve both high contact angle and self-cleaning ability. A versatile processing method based on electrostatic deposition and dry etching was developed to generate controllable roughness on engineering surfaces. These generated surfaces have a binary roughness structure on the micro- and nanoscale. The fluorocarbon thin layer generated during the dry etching process acted as a hydrophobic coating. This simple process is shown to achieve high contact angles with water of more than 160 degree. The spatial roughness parameter (autocorrelation length) was found to affect this contact angle behavior. Physical mechanisms for this observation are discussed on the basis of air-trapping. The effect of micro and nano scale roughness on the contact angle behavior was also studied.
9:00 PM - T8.17
Structure, function and in vitro mineralization studies of proteins isolated from the dorsal shield of cuttlebone, Sepia officinalis: Insights into mollusc shell formation
Gayathri Subramanyam 1 , Yiew Jocelyn 1 , Uma Devi Kanthimathi 1 , Suresh Valiyaveettil 1
1 Chemistry, National University of Singapore, Singapore Singapore
Show AbstractNature’s method of building materials using a bottom-up approach is fascinating. A clear understanding of this process of molecular self-assembly may pave way for the design of new materials at the nanoscale with very special properties. We are attempting to unveil nature’s fabrication strategy by studying the biomineralization process in marine organisms, where complex mineral structures are built into exquisite functional structures by the aid of specially designed biomacromolecules. In the present work, we were interested in studying the structural construction of cuttlebone by investigating the structure of the biomacromolecules occluded within the cuttlebone, and the role of these intramineral biomolecules in the formation of skeletal tissue. Cuttlebone refers to the specially adapted light-weight internal hrad-material of the cuttlefish which helps the creature stay afloat in water. The ultrastructure of the dorsal shield of cuttlebone was examined using scanning electron microscopy (SEM) to reveal aragonitic lamellar stacks. The intramineral proteins isolated by decalcification, dialysis and lyophilization was purified by reversed-phase high performance liquid chromatography (RP-HPLC) to obtain two major proteins of molecular weight 7 KD and 8 KD, in addition to a hydrophobic 17 KD protein. The proteins were characterized by MALDI-TOF, ESI-MS and N-terminal sequencing using Edman degradation. The secondary structural features of the proteins were studied using circular dichroism (CD) and anisotropic fluorescence spectroscopy. Light scattering studies indicated a concentration-dependent self-assembly of the proteins to form nano and micro fibres. The 7 KD and 8 KD proteins were found to aggregate under acidic conditions and exist as monomers in alkaline environments. The role of each of these proteins in mineralization was evaluated using in vitro CaCO3 precipitation experiments. References1.L. Addadi, D. Joester, F. Nudelman and S. Weiner, Chem. Eur. J., 2006, 12, 980 – 9872.F. Nudelman, B. A. Gotliv, L. Addadi and S. Weiner, J. Struct. Biol., 2006, 153, 176 - 187
9:00 PM - T8.18
Study of biochemical activity of immobilized yeast cells in response to external stimuli using differential interferometry
Gaurav Singh 1 , Dmitri Fomenko 2 , Vadim Gladyshev 2 , Ravi Saraf 1
1 Chemical and Biochemical Engineering, University of Nebraska Lincoln, Lincoln, Nebraska, United States, 2 Biochemistry, University of Nebraska Lincoln, Lincoln, Nebraska, United States
Show Abstract9:00 PM - T8.19
An In-Situ AFM Study of the Affect of Magnesium Impurities on Brushite Growth.
Jennifer Giocondi 1 , Xiangying Guan 2 , Jonathan King 1 , Christine Orme 1 , George Nancollas 2
1 Chemistry, Materials and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Dept. of Chemistry, State University of New York, Buffalo, Buffalo, New York, United States
Show AbstractThe mineralized structures found in nature occur in many unique forms that are difficult to reproduce in the lab using traditional methods. Gaining insight into how biological organisms construct these amazing structures would have great impact on both disease treatment and prevention as well as lead to new synthesis methods. Brushite, dicalcium phosphate dihydrate, is an important biomineral found in human kidney stones and dental calculi. It is also believed to be a precursor to the hydroxyapatite that forms bones and teeth. The goal of our research is to understand brushite growth on the microscopic level. In the work presented here we use in-situ AFM to investigate the crystal growth from dislocation hillocks on the (010) face of brushite in the presence of magnesium impurities. The atomic step morphology and growth rates are correlated with bulk crystallization rates as measured by constant composition experiments. Magnesium is typically the most abundant divalent ion, other than calcium, found in biological fluids. While the other calcium phosphate phases are known to incorporate magnesium, there has been no evidence that brushite does so. Our experiments confirm this finding but show that magnesium inhibits brushite growth and changes the step morphology. By correlating changes in the step velocity with magnesium concentration and brushite supersaturation we are able to determine how magnesium impurities interact with the growing mineral.
9:00 PM - T8.2
Protease specificity screening on liquid crystal arrays.
Louise Birchall 1 , Rein Ulijn 2 , Simon Webb 1
1 School of Chemistry , Manchester Interdisciplinary Biocentre, The University of Manchester, Manchester United Kingdom, 2 School of Materials, Manchester Interdisciplinary Biocentre, The University of Manchester, Manchester United Kingdom
Show AbstractGiven the large number of proteases and their importance in both proteomics and biomedical science, high-throughput screening methods for determining protease specificity are required. Existing methods suffer from the disadvantages of being time-consuming and needing expensive equipment to read the results of the analysis.Very recently, it has been shown that it is possible to detect enzyme activity using surfactant modified liquid crystal displays [1]. Inspired by this work, we aim to interface enzyme activity directly with liquid crystal display technology, therefore allowing the accurate, high throughput detection of protease specificity.Our first steps towards this goal are presented:The synthesis of peptidic surfactants that will undergo changes in physical properties, like critical micelle concentration, upon cleavage by a protease and the establishment of a protocol for observing the resultant changed in the LCD using optical microscopy.1. Brake, J.M.; Daschner, M.K.; Luk, Y.Y.; Abbott, N.L., Biomolecular interactions of phospholipid-decorated surfaces of liquid crystals, Science, 2003, 302, 2094.
9:00 PM - T8.20
Chemo-electrical energy conversion in a BioCell using Adenosine triphosphate: Modeling and experimental validation
Vishnu Baba Sundaresan 1 , Donald Leo 1 , Stephen Sarles 1
1 Mechanical Engineering Department, Virginia Tech, Blacksburg, Virginia, United States
Show Abstract9:00 PM - T8.21
How Do Red Blood Cells Deform? – A Structure Mechanics View
Long Xiao 1 , H. Jerry Qi 1
1 Department of Mechanical Engineering, University of Colorado, Boulder, Colorado, United States
Show Abstract9:00 PM - T8.22
Hydrogel-based Microcontact Printing for Fabrication of Arrays of Membranes and Membrane Proteins.
Sheereen Majd 1 , Anna Sauer 1 , Michael Mayer 1 2
1 Biomedical Eng., University of Michigan, Ann Arbor, Michigan, United States, 2 Chemical Eng., University of Michigan, Ann Arbor, Michigan, United States
Show Abstract9:00 PM - T8.23
Structure and Swelling Behavior of Self-Assembled Lipid/Silica films.
Darren Dunphy 1 , Eric Carnes 2 , Ying-Bing Jiang 1 , Helen Baca 2 , C. Brinker 1 2
1 , Sandia National Labs, Albuquerque, New Mexico, United States, 2 , University of New Mexico, Albuquerque, New Mexico, United States
Show AbstractRecently it was demonstrated that living cells entrapped within a mesostructured lipid/silica film formed via a self-assembly route actively direct the pathway of self-assembly (Baca et al., Science, July 2006); an important step in developing a thorough understanding of this process is the fundamental characterization of lipid/silica self-assembly without the presence of cells. Here we present the results of Grazing-Incidence X-ray Scattering (GISAXS) studies of silica films templated with short chain diacyl phosphatidylcholine lipids as a function of both acyl chain length (6-10 carbons) and lipid/silica ratio. We find that the phase behavior of these lipid/silica composites is dominated by the formation of lamellar and 2D hexagonal phases, although other mesophase morphologies also appear (i.e., a rhombohedral phase of unknown structure).For lamellar lipid/silica phases, the maximum interlayer spacing appears to be limited by the swelling behavior of phospholipid lamellae, yielding partial phase separation in lipid/silica films. Because this swelling behavior may be involved with localization of external components (nanocrystals, proteins, etc.) around cells during cell-directed self assembly, we will review our efforts in characterizing this phenomenon through x-ray scattering. Also, we will discuss lipid/silica mesophase formation using other lipids, including monoacyl phosphatidylcholines (commonly known as lysolipids) and a monoglyceride, glycerol monooleate (GMO). GMO is of particular interest in that 3D cubic phases derived from both micellular packing and bicontinuous surfaces are present in the lipid/water phase diagram; preliminary results show that these are also present in the lipid/silica system.
9:00 PM - T8.24
Applying Biomolecular Machinery for Nanostructure Assembly
Erik Spoerke 1 , Judy Hendricks 1 , Haiqing Liu 1 , George Bachand 1 , Bruce Bunker 1 , Robert Haddon 2 , Elena Bekyarova 2
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , University of California at Riverside, Riverside, California, United States
Show AbstractMicrotubules and motor proteins are key biological agents involved in the regulation of intricate physiological transport and assembly processes, ranging from cell division to the color changing behavior of some fish. These processes require that microtubules and kinesin motor proteins cooperate in a dynamic, active collaboration to direct the transport, assembly, and organization of biological nanomaterials. The controlled precision and scalability evident in this natural technology address some of the major challenges limiting nanomaterials assembly today. Our work attempts to utilize these active biological agents as tools for assembling technological nanomaterials into functional structures. By combining chemical and biological selectivity with active, and energy-consuming biological assembly processes, we aim to create microtubule-based bioscaffolds for nanomaterials organization and assembly. In this talk, I will discuss the use of selective chemical and biological methods used to direct the formation of these microtubule constructs and how these structures are used to create functional nanoscale device assemblies. This biomolecular approach to nanomanufacturing has tremendous potential to influence the application of functional nanostructures. 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.
9:00 PM - T8.25
Mimicking the Nature to Achieve Superhydrophobic Surfaces by Vapor Phase Deposition.
Sushant Gupta 1 , Rajiv Singh 1 , Arul Chakkaravarthi 2 , Jeff Opalko 2 , Deepika Singh 2
1 Materials Science & Engineering, University of Florida, Gainesville, Florida, United States, 2 , Sinmat Inc., Gainesville, Florida, United States
Show Abstract9:00 PM - T8.26
Novel Vapor Phase biodegradable coatings for controlled drug delivery systems.
Rajiv Singh 1 , Arul Chakkaravarthi Arjunan 1 , Sushant Gupta 1 , Jeff Opalko 2 , Deepika Singh 2
1 Materials Science and Engineering, University of Florida, Gainesville, Florida, United States, 2 , Sinmat Inc., Gainesville, Florida, United States
Show Abstract9:00 PM - T8.27
Nanoscale Cardiovascular risk Profiler
Kondama Reddy Ravi Kiran 1 , Thomas Barrett 3 , John Carruthers 2 , Shalini Prasad 1
1 Electrical and Computer Engineering, Portland State University, Portland, Oregon, United States, 3 Department of Medicine, Oregon Health and Science University, Porltand, Oregon, United States, 2 Physics, Portland State University, Porltand, Oregon, United States
Show Abstract9:00 PM - T8.28
Molecular Erectors: Directed Enzyme Immobilization via Genetically Engineered Peptides
Urartu Seker 2 1 , Brandon Wilson 1 2 , Candan Tamerler 2 1 , Mehmet Sarikaya 1 2
2 Molecular Biology an Genetics, Istanbul Technical University, Istanbul Turkey, 1 Materials Science and Engineering, University of Washington, Seattle, Washington, United States
Show Abstract9:00 PM - T8.29
X-ray Absorption Spectroscopy (XAS) Characterization of CaCO3 Growth on Organothiol Self-Assembled Monolayers
Jonathan Lee 1 , Yong-Jin Han 1 , Trevor Willey 1 , Robert Meulenberg 1 , Louis Terminello 1 , Tony van Buuren 1 , James De Yoreo 1
1 , Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractX-ray Absorption Spectroscopy (XAS) has been used to characterize the structural evolution of bio-inspired crystallization systems. We present an XAS investigation of CaCO3 growth on self-assembled monolayers (SAMs) of organothiols prepared on Au(111) substrates. In the natural world, bio-organisms utilize surface matrices of organic molecules to exert remarkable control over the mode of mineral crystallization from solution. Elaborate, hierarchical inorganic assemblies are often generated, which can exhibit architecture on the sub-micron scale. Such precise engineering of crystal structure and, therefore, material properties would find direct application in the fabrication of inorganic components for optical and electronic devices. Hence, an understanding of the underlying physical processes is required to aid development of new material growth technologies. Self-assembled monolayers of omega-substituted alkanethiols, mercaptophenols and mercaptobenzoic acids serve as templates for patterned crystallization and, as such, mimic the natural processes of biomineralization. In addition, these systems offer a relative simplicity of structure. As a consequence, they represent suitable models from which to characterize the interaction between organic and inorganic phases during crystal nucleation and growth. This interaction resides at the heart of biomineralization processes. XAS provides ideal capabilities for the investigation of structural development at the organic/inorganic interface during crystallization. Due to the chemical specificity of the technique, atoms at the buried interface can be probed directly. Furthermore, Near Edge X-ray Absorption Fine Structure (NEXAFS), the first component of XAS, can be used to characterize the geometric and electronic structure of organic monolayers. Moreover, the Extended X-ray Absorption Fine Structure (EXAFS), the second component of XAS, provides assignment of the local environment about a specific element and can yield the structure of the crystalline mineral.This work was supported by the Division of Chemical Sciences, Office of Basic Energy Science, and performed under the auspices of the U.S. DOE by LLNL under contract No. W-7405-ENG-4
9:00 PM - T8.3
A systematic study of molecular motor-driven self-assembly
Isaac Luria 1 , Elizabeth Mobley 1 , Michelle Kinahan 1 , Henry Hess 1
1 Materials Science and Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractSelf-assembly, a key bottom-up fabrication technique, relies on the motion of the building blocks to establish predetermined connections. Active transport driven by molecular motors, employed in biological systems to bridge diffusion and pressure-driven fluid flow regimes, can accelerate the transport of nano- and mesoscale building blocks. Moreover, the strong and directed forces exerted by the motors lead to surprising self-organization phenomena in the assembly process. We have studied the self-assembly of individual components propelled by molecular motors in a biomimetic system. Specifically, we used kinesin motor proteins bound to a surface to propel biotinylated microtubules; adding streptavidin allowed the microtubules to stick to each other. This left us with a surface covered in motor-propelled, “sticky” components capable of forming nanoscale structures. On a planar surface, these “sticky” building blocks will self-assemble into long “wires” which subsequently form rotating “spool” structures of varying radius. Thus, the motor-driven, constrained motion of the building blocks and intermediate assemblies guided the formation of the structures, despite the non-specific nature of the binding. We envision that the ability to restrict and define the transport of building blocks will complement the design of specific connections between building blocks in self-assembled systems. Here we present a systematic study of the assembly process, in which we characterized the local and global results of the assembly process as a function of the input parameters.
9:00 PM - T8.30
Biological Fabrication of Germanium/Silca nanocomposite
Doo-Hyoung Lee 1 , Tian Qin 1 , Clayton Jeffryes 1 , Debra Gale Gale 1 , Gregory Rorrer 1 , Chih-Hung Chang 1 , Timothy Gutu 2 , Jun Jiao 2
1 Chemical Engineering, Oregon state University, Corvallis, Oregon, United States, 2 Department of Physics, Portland State University, Portland , Oregon, United States
Show AbstractDiatoms are single celled microalgae that possess cell walls composed of amorphous silica nanoparticles that are patterned into intricate nano- and microsctructures. Recently, we harnessed the biomineralization capacity of the marine diatoms to biologically fabricate silicon oxide/ germanium oxide nanocomposite materials. Germanium nanoparticles embedded in silica matrix could potentially use for memory devices and optoelectronic devices. In this paper, we will report our recent success in the fabrication of germanium nanocrystals embedded in Nitzschia-diatom silica frustules. Highly crystalline germanium nanocrystals around 5nm are uniformly dispersed throughout the diatom frustules. In addition, strong blue photoluminescence was observed from these nanocrystals embedded diatom. This research is supported by National Science Foundations’ Nanoscale Interdisplinary Research Team grant number BES-0400648.
9:00 PM - T8.4
Novel cancer therapeutics through inhibiting telomerase-associated protein complexation
Alphonsus Tan 1 , So-Jung Han 4 3 , Sahn-Ho Kim 3 , Judith Campisi 3 , Seung-Wuk Lee 1 2 , Judith Campisi
1 Bioengineering , University of California, Berkeley, Berkeley, California, United States, 4 Molecular and Cellular Biology, University of California, Berkeley, Berkeley, California, United States, 3 Life Science Division, Lawrence Berkeley National Lab, Berkeley, California, United States, 2 Physical Bioscience Division, Lawrence Berkeley National Lab, Berkeley, California, United States
Show AbstractThe activation of telomerase, an enzyme that adds specific nucleotide sequences to the 3’ end of telomeric DNA, allows many cancer cell types to divide indefinitely. Three telomere associated proteins, TIN2, TRF1, and TRF2, form a complex which controls telomere length by modifying telomere structure and the ability of telomerase to access telomeres. Characterization of the interactions between these proteins may lead to novel anti-cancer therapies. Phage display is a powerful tool that utilizes combinatorial screening to identify and characterize protein interactions with a specific target. Using phage display, we have identified the protein binding motifs between TIN2, TRF1, and TRF2. Immunoprecipitation and Western Analysis of synthesized amino acid sequences and the target proteins corroborate the results obtained from phage display. Site specific mutation of amino acids within the binding domains was performed to analyze any affect on protein-protein interactions. Our findings provide a possible specific target for peptide-based inhibitors and other anti-cancer drug delivery systems.
9:00 PM - T8.5
Design and Development of a Bio-inspired Adhesive based on Complex Coacervation.
Abril Estrada 1 , Cheng-jun Sun 2 , Hua Zhao 2 , Herbert Waite 1 2
1 Chemistry and Biochemistry, University of California-Santa Barbara, Santa Barbara, California, United States, 2 Molecular, Cellular and Developmental Biology, University of California-Santa Barbara, Santa Barbara, California, United States
Show AbstractWhile few synthetic adhesives have shown much bonding ability under wet conditions, marine adhesives have proved remarkably effective underwater. The adhesive synthesized by sand castle worm Phragmatopoma californica is of special interest, being composed of three highly charged and repetitive proteins that include the modified residue L-3,4-dihydroxyphenylalanine (DOPA), to which underwater adhesion is attributed. Here we report on the synthesis of marine adhesive protein mimics and their subsequent use for the formation of polyelectrolyte complexes (PEC's) in solution. Charged polymers containing phosphate and amine side chains have been synthesized employing α-amino acid-N-carboxyanhydride (NCA) polymerizations and radical polymerizations. By coupling the oppositely charged polymers in solution under specific conditions of pH, temperature, ionic strength and polymer concentration, we have obtained PEC's, also known as complex coacervates, with the ability to swell or absorb water from their surroundings. The potential of PEC's to remove hydration layers that inhibit adhesion on underwater surfaces, and the many adhesive and cohesive roles of DOPA and DOPA-like structures contained in the polymer chains will also be discussed.
9:00 PM - T8.6
Synthesis of poly(ethylene glycol)-co-peptide hydrogels by thiol-ene photoinitiated polymerization
Benjamin Fairbanks 1 , Charles Nuttelman 1 , Kristi Anseth 1
1 Chemical and Biological Engineering, Univ. of Colo., Boulder, Colorado, United States
Show AbstractThe ability to tune material properties to mimic those of native tissues has made synthetic hydrogels an attractive class of material to encapsulate cells and study/manipulate tissue development. While hydrogels formed through traditonal addition or condensation reactions allow for highly regular chemical architectures, most methods of forming these types of covalently crosslinked hydrogels require reaction conditions that are incompatible with cell encapsulation. Recently, conjugate addition reactions between thiol functional groups and conjugated unsaturated functional groups (e.g., acrylate or vinyl sulfone) have been used to create hydrogels under mild, physiologically relevant conditions. Here, we present a the creation of similar networks via the unique radical-mediated thiol-ene polymerization, a photo-catalyzed reaction between a thiol group and an unconjugated ene (e.g., allyl ether or vinyl ether) that proceeds through a step growth mechanism resulting in a 1:1 reaction between the thiol group and ene moieties. Gels were made with four-arm poly(ethylene glycol) (PEG) allyl ether of molecular weights of 10kDa and 20kDa and a peptide, KCKGGPRGKCK, containing a trypsin/cathepsin K cleavable substrate (in bold) flanked on either end by a cysteine residue providing the thiol functionality and lysine residues for enhanced aqueous solubility. Polymerizations were performed with varying concentrations of photoinitiator, 4-(2-hydroxyethoxy) phenyl-(2-hydroxy-2-propyl)ketone (Irgacure 2959). The polymerization reaction was monitored with differential scanning calorimetry and gelation characteristics with rheometry. Gel swelling and modulus were influenced by both the molecular weight of the PEG as well as initiator concentration indicating differences in network structure. Complete degradation via surface erosion was observed upon exogenous delivery of trypsin. Networks polymerized using this method containing a relevant MMP degradable peptide sequence as well as the RGDS integrin binding motif permitted significant cell spreading for encapsulated human neonatal foreskin fibroblasts and primary porcine valvular interstitial cells.
9:00 PM - T8.7
Nanowire Fabrication by Self-Assembly of Tobacco Mosaic Virus Coat Proteins.
Lim Lee 1 , Derrick Bell 1 , Zhongwei Niu 1 , Mike Bruckman 1 , Byeongdu Lee 2 , Qian Wang 1
1 , University of South Carolina, Columbia, South Carolina, United States, 2 , Advanced Photon Source, Argonne National Lab, Argonne, Illinois, United States
Show AbstractThe quaternary structure of proteins has been an intriguing feature of molecular functionality, but recently such organized assemblies have been utilized as robust structural templates for inorganic material synthesis and nanomaterial development. Viruses, ferritin, heat shock proteins, and enzyme complexes form a core of such biogenic nanostructures. These systems serve as inspirational materials that have been utilized as templates for inorganic nanoparticle synthesis and aligning various materials into nanosized wires, rings, fibers, and films. Recently, we have demonstrated that native Tobacco Mosaic Virus (TMV) can be co-assembled with aniline to give one-dimensional nanowires. Here, we utilize coat protein subunits of TMV to produce monodispersed, micron-length biocomposite nanofibers stabilized by in situ surface polymerization of aniline. Our studies confirm that the conformational switch of the coat protein assemblies from stacked disks to a helical configuration is a key factor for such assembly process. In addition, using different doping reagents, conductive TMV-polyaniline composite nanowires can be readily produced.
9:00 PM - T8.8
Controlled assembly of recombinantly produced Spider Silk in a Microfluidic Device.
Sebastian Rammensee 1 , Ute Slotta 2 , Thomas Scheibel 2 , Andreas Bausch 1
1 Biophysics Department E22, Technische Universitaet Muenchen, Garching Germany, 2 Biotechnology Group, Chemistry Department, Technische Universitaet Muenchen, Garching Germany
Show AbstractSpider Silks are protein materials which show mechanical properties being superior to all man-made materials in regard to toughness and elasticity. However, commercial applications of natural spider silk are complicated by the highly cannibalistic and territorial behavior of spiders. This problem can be circumvented by recombinant production of spider silk analogous proteins in bacteria. Further, the recombinant technology allows the introduction of tailored subunits into the proteins in order to produce materials that are individually optimized for the given application.In vivo, the highly complex spinning process is performed in a specialized organ, being a topic of current research. The spinning dope is a protein solution of high concentration revealing liquid crystalline flow properties. We study the process of silk fiber formation in microfluidic devices under laminar flow conditions, where mixing occurs only by diffusion. We investigated whether modifications of flow geometry and flow parameters such as shear rate, Péclet number, viscosity and the presence of different non-aqueous phases in the flow alter the structure and mechanical properties of the resulting silk structures.With a whole set of recombinantly produced spider silk analogous proteins available for experiments, the influence of different structural features of the proteins on fiber formation can be studied. We present secondary structure information obtained by infrared spectroscopy and Scanning Electron Microscopy images of the produced silk assemblies.
9:00 PM - T8.9
Production of novel cellulose-protein composite materials in Acetobacter xylinum
Shaul Lapidot 1 , Gerhard Miksch 2 , Mara Dekel 1 , Sigal Meirovitch 1 , Erwin Flaschel 2 , Oded Shoseyov 1
1 The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture and the Otto Warburg Minerva Center for Agricultural Biotechnology, The Hebrew University of Jerusalem, the Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot Israel, 2 Fermentationstechnik, Universitaet Bielefeld, Bielefeld Germany
Show AbstractThis research project aims at producing novel self assembled composite materials with superior mechanical properties made from bacterial cellulose and spider silk in Acetobacter xylinum. The materials will be produced by a novel fusion protein of cellulose binding domain (CBD) and synthetic spider silk (CBD-Silk). Two parallel strategies were chosen for production of the cellulose-silk composite; in-vitro by supplementation of recombinant CBD-Silk (E. coli produced) to the A. xylinum medium during its growth and cellulose production. In-vivo, by expressing CBD-Silk in A. xylinum under the kil system, specially designed for recombinant protein secretion in Gram negative bacteria. The binding of CBD-Silk to the bacterial cellulose will enable matrix assisted refolding and polymerization of the spider silk, whereas the crystalline ordered fibrous structure of the cellulose will serve as a template for proper silk arrangement. Former work showed that cellulose production increased by 5-fold upon supplementation of recombinant CBD to the A. xylinum medium. Recently we managed to successfully express functional CBD in supernatants of transformed E. coli which serves as a model for the kil system. Furthermore A. xylinum expressing CBD under the kil system were produced and are presently being analyzed. Preliminary results indicated a significant difference in the morphology of the cellulose producing colonies. The production of the fusion protein CBD-Silk is under progress.
Symposium Organizers
Rajesh R. Naik Air Force Research Laboratory
Carole C. Perry Nottingham Trent University
Kiyotaka Shiba Japanese Foundation for Cancer Research
Rein Ulijn University of Manchester
T9: Bioresponsive and Bionanomaterials
Session Chairs
Friday AM, April 13, 2007
Room 2006 (Moscone West)
9:30 AM - **T9.1
Bio-Responsive Nanoparticle Assemblies
Molly Stevens 1
1 Department of Materials and Institute for Biomedical Engineering, Imperial College, London United Kingdom
Show AbstractThe ability to direct the assembly of inorganic nanoparticles has received growing interest in the creation of new nanotechnology devices and in medical science. Assembly and dis-assembly of such assemblies under physiologically accessible environmental conditions, as triggered for example by changes in pH or the presence of enzymes is valuable for materials to be utilized for sensing in vivo and drug delivery. We have engineered coiled-coil peptide functionalised nanoparticles, the assembly of which can be reversibly controlled under mild conditions (near-neutral pH and ambient temperature). A reversible pH-induced transition occurs between pH 8.5 and 7 for gold nanoparticles coated with acidic leucine zipper-like coiled-coil peptides as monitored by circular dichroism, transmission electron microscopy and UV-visible spectroscopy. We have also developed a new approach to enzyme triggered nanoparticle dis-assembly whereby real-time monitoring of enzyme action is possible with very high sensitivity. The enzyme responsiveness of the system is demonstrated by incubating tri-peptide functionalised nanoparticles with concentrations of thermolysin ranging from 7 nM to 2 zM.
10:00 AM - T9.2
Enzyme-Triggered Self-Assembly of Peptide Hydrogels via Reversed Hydrolysis
Richard Williams 1 2 , Rein Ulijn 1 2
1 Manchester Interdisiplinary Biocentre, The University of Manchester, Manchester United Kingdom, 2 Materials Science Centre, The University of Manchester, Manchester United Kingdom
Show AbstractPeptide-based self-assembled biomaterials have the potential to act as artificial extracellular matrices for wound repair and tissue engineering. We recently demonstrated that di-/tri-peptides modified with fluorenylmethyloxycarbonyl (Fmoc) form highly tuneable hydrogels that support cell culture in 3D. The self-assembly mechanism that is exploited builds on recent reports by us and others that demonstrated that a number of the peptides self-assemble into nanofibrous structures driven by pi-stacking of the conjugated fluorenyl group, and are further stabilized by hydrogen bonding (fig1). The ability to control the assembly of these structures on-demand by application of an external stimulus is of value, especially in biomedical contexts. For example, in minimal invasive surgery for tissue repair, a liquid precursor is mixed with cells and injected into the body to form a gel scaffold in situ for tissue regrowth.Stimuli that have been used to trigger self-assembly include a variety of chemical and physical means, such as changes in ionic strength, pH, and temperature, and addition of certain chemical entities. An alternative approach is to exploit enzyme catalyzed reactions as selective biological stimuli to trigger hydrogel assembly. This approach has a number of advantages because enzymes highly selective, work under mild conditions (aqueous, pH 5-8, 37 °C) and play key roles as selective catalysts in cell pathways and disease states.We believe that enzyme triggered formation of fibrillar gels allows for self assembly to occur under thermodynamic control, thus avoiding the problem of aggregate formation via kinetic entrapment.In this presentation we will describe a conceptually novel approach by using proteases, enzymes that normally hydrolyze peptide bonds in aqueous medium, to perform the reverse reaction (i.e., peptide synthesis or reversed hydrolysis) to produce amphiphilic peptide hydrogelators that self-assemble to form nanofibrous structures (Toledano et al, JACS, 2006). We report on the use of IR, Fluorescence and CD spectroscopies combined with Cryo-scanning electron microscopy to verify the formation of nano-scale fibrillar structures with timeMonitoring the environment of the large, aromatic Fmoc group was achieved by observing fluorescence emission of the molecule as the hydrogel forms. Current data indicates that the aromatic fluorenyl rings form pi-pi interactions. IR studies show this interaction leads to the formation of antiparrellel β-sheets which provide the structure of the fibrils. HPLC analysis allowed us to follow the thermodynamic formation of the tripeptide.
10:15 AM - **T9.3
Enzymatic Supramolecular Hydrogelation for Making Biomaterials.
Zhimou Yang 1 , Bing Xu 1 , Gaolin Liang 1 , Manlung Ma 1
1 Chemistry, HKUST, Kowloon Hong Kong
Show AbstractEnzymes, as a class of highly efficient and specific catalysts, dictate a myriad of reactions that constitute various cascades in biological systems in nature. The expression and distribution of enzymes differ by the types and states of cells, tissues, and organs, thus leading to diverse extracellular and intracellular environments. Using an enzymatic reaction to convert precursors into hydrogelators that self-assemble into nanofibers as the matrices of the hydrogel, one can control the delivery, function, and response of a hydrogel according to a specific biological condition or environment, thus providing an accessible route to create sophisticated soft materials for biomedicine. This talk will discuss enzymatic formation or regulation of supramolecular hydrogels, a biomimetic methodology not only provides a new way to create hydrogels in vivo, but also could ultimately lead to a new paradigm for developing biomaterials. In addition, specific examples of the applications of enzymatic hydrogelation will also be illustrated.
10:45 AM - T9.4
Nanopore-based Detection of Immune Complexes and Viruses.
Jeffrey Uram 1 , Kevin Ke 1 , Alan Hunt 1 2 , Michael Mayer 1 3
1 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan, United States, 3 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractWe present a nanopore-based assay that uses the resistive-pulse technique for detecting and characterizing biological self-assembly in two model systems: (i) the formation of immune complexes from antibody-protein interaction; and (ii) the binding of antibodies to a virus particle. The assay is rapid, label-free, requires no immobilization or modification of the antibody or antigen, and is able to detect individual complexes (antibody-protein, antibody-virus) by monitoring the changes in electrical resistance that occur when a complex passes through a nanopore. We employed a novel fabrication technique that used a femtosecond-pulsed laser to machine conical nanopores with diameters as small as 190 nm in borosilicate cover glass. These conical nanopores made it possible to estimate the number of antibodies in an immune complex or bound to a virus particle. Monitoring the passage of individual complexes (antibody-protein, antibody-virus) allowed following the growth and size-distribution of the complexes. With this technique, we were able to detect antibody-protein complexes consisting of as few as 40 proteins. The technique offers a general strategy for characterizing the dynamics of biological self assembly, and may be applicable to synthetic systems that either form aggregates naturally or are triggered to aggregate.
11:30 AM - **T9.5
Self-assembly of peptides and peptide derivatives into nanofibrous scaffolds.
Jeffrey Hartgerink 1
1 Chemistry & Bioengineering, Rice University, Houston, Texas, United States
Show AbstractOne-dimensional, nanostructured, materials are desirable in applications ranging from nanoelectronics to biomaterials. Those that can be prepared via self-assembly have advantages in that they can be designed to interact with and respond to their environment in a predictable fashion. In this seminar I will discuss the design, synthesis and characterization of three self-assembling peptide-based systems that form nanofibers. The application of these systems as a scaffold for stem cell growth and differentiation will also be discussed.
12:00 PM - T9.6
Kinesin-driven cargo pick up through the unzipping of DNA surface tethers
Marlene Bachand 1 , Brandon Heimer 1 , George Bachand 1
1 Biomolecular Interfaces & Systems, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractEnergy-consuming processes play a fundamental role in the self-assembly of dissipative structures and materials in biological systems. Such non-equilibrium processes enable rapid restructuring and reorganization of materials in response to the continuously changing physiological needs of a cell. Integration of mechanisms mimicking these processes may permit the development of nanoscale devices and materials in which the assembly, disassembly, and organization may be programmed or self-regulated. The overall goal of our work is to understand and mimic Nature’s means for assembling dissipative nanostructured materials through the integration of active and dynamic assembly processes in hybrid architectures. We have recently demonstrated the transport and assembly of nanocomposite materials using a biomolecular active transport system. In these experiments, highly-constrained, ring-like structures were assembled through the kinesin-driven transport of microtubules and nanocrystal quantum dots. More recently, work has focused on the ability to pick-up surface-tethered nanoparticles using kinesin-based transport of functionalized microtubules. Streptavidin-coated, polymer and crystalline nanoparticles were tethered to surfaces using bifunctional, partially-doubled stranded DNA oligomers. These oligomers enabled the establishment of stable, singly-tethered nanoparticles to gold surfaces. Elastic collisions between kinesin-driven microtubules and tethered nanoparticles in motility cells resulted in the "unzipping" of the DNA molecules, and transfer of the nanoparticles to the microtubule. These results of this work and the relationship to the active assembly of nanostructure materials will be discussed.*Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, or the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
12:15 PM - T9.7
Reversible Vesicle Restraint in Response to Spatiotemporally-Controlled Electrical Signals
Gregory Payne 1 , Chao Zhu 1 2 , Srinivasa Raghavan 2 , Douglas English 3 , Reza Ghodssi 4
1 Center for Biosystems Research, University of Maryland Biotechnology Institute, College Park, Maryland, United States, 2 Department of Chemical and Biomolecular Engineering, Univeristy of Maryland, College Park, Maryland, United States, 3 Department of Chemistry and Biochemistry, Univeristy of Maryland, College Park, Maryland, United States, 4 Department of Electrical and Computer Engineering & Institute for Systems Research, Univeristy of Maryland, College Park, Maryland, United States
Show AbstractThe signal processing capabilities of microelectronic devices are often compared to those of the nervous system, yet their differences are profound. Microelectronic devices communicate with electrons, while the nervous system communicates with ions and molecules. While comparing the brain and computer is instructive, bridging the signaling differences could offer substantial practical benefit. For instance, the effective interfacing of microelectronic devices with biology could provide new opportunities for applications that range from biosensing to neuroprosthetics. Here, we report the use of a localized electrical signal to perform a chemical signaling operation common in the nervous system. Neurotransmitters are integral to chemical communication between pre- and post-synaptic nerve cells. In most cases the neurotransmitters are water soluble but are compartmentalized within vesicles for their targeted delivery – exocytosis of the vesicles releases the neurotransmitters into the synaptic cleft. In addition to free vesicles that are available for exocytosis, the pre-synaptic cells often have a reserve pool of neurotransmitter-containing vesicles that are tethered to the cytoskeleton. The reversible restraint and mobilization of this reserve pool of vesicles is triggered by a complex and incompletely-understood biochemical reaction cascade. We mimic the reversible restraint of vesicles using localized electrical signals. Specifically, we employ electrical signals to reversibly restrain vesicles by enlisting the stimuli-responsive aminopolysaccharide chitosan that is able to “recognize” electrical stimuli and electrodeposit onto cathode surfaces as a stable film. We show that surfactant-vesicles and liposomes can be co-deposited with chitosan, and are entrapped (i.e., restrained) within the deposited film’s matrix. Vesicle co-deposition can be controlled spatially and temporally using microfabricated wafers with independent electrode addresses. Finally, we show that vesicles restrained within the deposited chitosan matrix can be mobilized under mildly acidic conditions (pH < 6.5) that re-solubilize chitosan. Potentially, the ability to restrain and mobilize chemical signals that are segregated within vesicles, may allow microfluidic systems to access the rich diversity offered by chemical signaling.
12:30 PM - T9.8
Collagen Based Materials for Local Drug Delivery Systems
Katarzyna Slowinska 1 , Chi Kin Liu 1 , Luciano Castaneda 1 , Suzanne Pluskat 1 , Earry Te 1 , Darline Ky 1
1 Chemistry and Biochemistry, California State University, Long Beach, Long Beach, California, United States
Show Abstract A novel collagen based material for local drug delivery systems is reported. The collagen matrix modified with standard (glutaraldehyde) and novel (monolayer protected gold clusters) crosslinking agent was characterized using several methods to determine the structure and properties of the material. Electrochemical Time-of-Flight (ETOF) method was used to measure the diffusion coefficient of 4-hyrdoxy Tempo, a molecular probe, in collagen I matrix solution as a function of its concentration and the extent of crosslinking with Glutaraldehyde (GA). The values of the diffusion coefficient were correlated with Circular Dichroism (CD) and viscosity data to assess the changes of the structure of a collagen matrix. The low value of probe diffusion coefficient indicates that the molecular collagen contributes to large diffusion hindrance of the medium. The combined Brinkman or effective medium model and the Carman-Kozeny model are used to estimate the average diameter of a matrix pore as a function of collagen solution composition. We show that 0.5 and 1% (w/w) collagen matrix crosslinked with the addition of GA above 0.1% (v/w) forms matrix with pores larger than in native collagen. This result suggests the existence of a micro-phase separation in the crosslinked collagen matrix [1]. The ETOF method was also used to measure the diffusion coefficients of Tempo amid derivatives with different length of the alkyl chain (CnTPA, n=5-9) in collagen matrix solution as a function of crosslinking with GA. The values of the diffusion coefficient were interpreted in terms of hydrophobic interactions between the molecular probe and the matrix, within the matrix pores. Furthermore we present novel type of a crosslinking agent, a monolayer protected gold nanoclusters, which can produce unique collagen matrix arrangement and thus improves the properties of the matrix. The collagen matrix modified with this novel crosslinking agent is studied in terms of its structure with transmission electron microscope. The thermal stability is examined with differential scanning calorimetry. To assess the biocompatibility of the matrix, cytotoxicity assays are conducted.The implications of these findings in the design of small molecule and protein drug delivery systems will be discussed.References:[1] D. Ky; C. K. Liu; C. Marumoto; L. Castaneda; K. Slowinska Journal of Controlled Release, 2006, 112, 214
12:45 PM - T9.9
In vitro selection on surfaces (ISOS): Advanced screening of biological reagents for materials applications
Scott Sweeney 1 , Amy Mahady 2 , Rajesh Naik 3 , J. Berglund 2 , James Hutchison 1
1 Department of Chemistry and Materials Science Institute, University of Oregon, Eugene, Oregon, United States, 2 Institute of Molecular Biology, University of Oregon, Eugene, Oregon, United States, 3 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, United States
Show AbstractInterest in the use of biopolymers, such as RNA and peptides, for nanomaterials applications has increased substantially in recent years. This has been driven in part by in vitro selection methods, such as phage display and SELEX, that allow for the identification of peptides or RNA aptamers with desirable functionality. Additionally, the use of biological reagents in the preparation of nanomaterials alleviates the use of potentially harmful chemicals, leading to greener syntheses. Despite recent progress, a significant challenge remains in the identification of biological reagents with suitable selectivity and activity for the formation of well-defined nanomaterials. To address this challenge we have developed a novel method, in vitro selection on surfaces (ISOS), for selecting peptides and RNA aptamers from diverse biomolecule libraries that have a high affinity and selectivity for surface bound targets. To carry out ISOS, we have designed a microreactor that allows for screening only on the surface of interest, greatly enhancing the selectivity and simplicity of the screening process. To demonstrate the utility of ISOS, we have selected both peptide and RNA molecules that show a high affinity for gold surfaces, as indicated via binding assays and sequence analysis. We have subsequently used these selected biopolymers in the synthesis of both solution and surface bound nanostructures. It is expected that the high degree of selectivity and versatility of the ISOS approach will establish its use in a variety of applications ranging from drug delivery and sensors to synthesis and separations.
T10: Biomedical Materials and Applications
Session Chairs
Friday PM, April 13, 2007
Room 2006 (Moscone West)
2:30 PM - T10.1
A Novel Technique for Intracellular Nanosensor Delivery
Karen Fisher 1 2 , Jonathan Aylott 2 , Rhodri Jones 2 , Vesselin Paunov 1
1 Department of Chemistry, University of Hull, Hull, North Humberside, United Kingdom, 2 School of Pharmacy and Department of Immunology, University of Nottingham, Nottingham United Kingdom
Show AbstractWe report a new method for delivery of nanosensors through the membrane of living cells. The method is based on using cationic liposomes as encapsulating agents for nanosensors as their membranes naturally fuse with cellular membrane. This makes them prospective vehicles for intracellular delivery of nanosensor probes. Polyacrylamide nanosensor particles were prepared by water-in-oil microemulsion polymerisation where the monomers (acrylamide and N,N-methylene bisacrylamide) and fluorophores are dissolved in water and introduced to the microemulsion as the aqueous phase. The produced nanosensors are spherical polymeric particles with a typical diameter of 50 nm which results in sub-second response times, indeed some sensors respond in the millisecond timeframe. Nanosensors consist of a stimulus-responsive fluorescent probe encapsulated into a porous nanoparticle where the fluorophore and other components of the sensor cannot leak out and contaminate the cell interior, while the signal triggering component (analyte) can freely diffuse through the pores of the nanosensor matrix. Using this versatile methodology a range of pH and oxygen sensitive fluorophores were physically entrapped within the nanoparticles polymeric matrix by binding to high molecular weight dextran molecules. We used the lipid extrusion technique to encapsulate our nanosensor particles within the small liposomes doped with a cationic lipid. The nanosensor suspension was mixed with the cationic liposomes followed by multiple extrusions through a polycarbonate membrane. We used TEM to study the degree of encapsulation of the nanosensors inside the liposomes. We used human mesenchymal stem cells (hMSC) to test the nanosensor delivery method by exposing the cells to liposomes modified with fluorescently tagged lipids and cationic liposomes loaded with fluorescently labeled nanosensors. An increase in fluorescence of hMSC was seen following incubation with PC:PG:FITC DHPE liposomes. We also showed that the nanosensors are successfully delivered into the cell interior after incubation of the hMSC cells with nanosensor loaded liposomes which was confirmed by confocal fluorescence microscopy and other techniques. The developed new method for non-invasive intracellular delivery of nanosensors can find a number of applications for monitoring the local conditions inside cells for a number of cell types. Intracellular delivery of the nanosensors allows important metabolic markers (glucose, oxygen, calcium and pH) to be determined as hMSC differentiation occurs. This information can help to identify differentiation events and trigger the development of new classes of nanosensors to monitor and record the lineage commitments of hMSC.
2:45 PM - T10.2
Creation of fluorescent gold nanoclusters using rationally designed and combinatorially selected peptides.
Jennifer Martinez 1 , Chang Zhong 1 , Dung Vu 2 , Jurgen Schmidt 3 , Yuping Bao 1 , R. Dyer 2
1 MPA-CINT, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 C-PCS, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 3 B-3, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractNanoclusters are collections of small numbers of noble metal atoms that exhibit strong size-dependent emission. These water soluble clusters are smaller in size (<1 nm), with comparable fluorescence to semiconducting quantum dots; yet, nanoclusters are produced at ambient temperature with nontoxic precursors. Our lab and others have produced nanoclusters with discreet fluorescence emissions using dendrimer templates. While these clusters show great promise for sensing and imaging applications, the large relative size of the dendrimer template may ultimately limit their applicability. In an effort to produce nanoclusters that are easily conjugated to biomolecules and to mimic the biological creation of organic/inorganic hybrids, we have employed both combinatorial and rational design methods to create peptides that control the growth of gold nanoclusters. The selection, design, synthesis, and photophysics of the resulting clusters will be discussed.
3:00 PM - T10.3
Metal Oxide Materials as Hemostatic Agents
Sarah Baker 1 , April Sawvel 1 , Galen Stucky 1
1 Chemistry, University of California Santa Barbara, Santa Barbara, California, United States
Show AbstractThe ability to quickly stop severe bleeding after traumatic injury will have great impact on public health. Quikclot, a zeolite based composite material, has proven to be highly effective at stopping hemorrhage and conferring survival both in an animal model of lethal groin injury and in combat.1,2 However, the mechanism of action of Quikclot is not well-understood. Toward the rational design of superior hemostatic materials, we will first describe our efforts toward uncovering the materials properties which influence its efficacy. These properties include: heat and ion release, protein-accessible surface area, and surface chemistry. We will also describe how these properties affect specific aspects of blood clotting, including platelet and protein activation, and blood cell agglutination.Although Quikclot has been shown to save lives, it is used only as a last resort in treatment of hemorrhage because of the danger that it may damage tissues due to its exothermic reaction with water. We have discovered that certain classes of metal oxides clot blood nearly as quickly as does Quikclot in vitro, both in normal and heparinized whole blood, despite having significantly lower surface areas and no heat release. Additionally, we have uncovered evidence that suggests that these hemostatic agents and Quikclot act on the blood through distinct pathways. Further, we have found that the combination of the two types of materials enables better in vitro performance than if used separately, an indication that the two agents, when used together, work in concert. In an effort to optimize and understand the favorable clotting interaction inorganic oxides and blood, we will describe how the modification of surface chemistry, surface area, and guest cations affects blood-clotting characteristics.1.Ostomel, T. A.; Stoimenov, P. K.; Holden, P. A.; Alam, H. B.; Stucky, G. D., Host-guest composites for induced hemostasis and therapeutic healing in traumatic injuries. Journal of Thrombosis and Thombolysis 2006, 22, 55-67.2.Alam, H. B.; Burris, D.; DaCorta, J. A.; Rhee, P., Hemorrhage Control in the Battlefield: Role of New Hemostatic Agents. Military Medicine 2005, 170, (1), 63-69.
3:15 PM - T10.4
Bioceramic Coatings Produced by Right Angle Magnetron Sputtering for Biomedical Applications.
Zhendong Hong 1 , Donald Ellis 1 2 , John Ketterson 1 3
1 Dept. of Physics and Astronomy, Northwestern University, Evanston, Illinois, United States, 2 Department of Chemistry, Northwestern University, Evanston, Illinois, United States, 3 Department of Electrical and Computer Engineering, Northwestern University, Evanston, Illinois, United States
Show Abstract3:30 PM - T10.5
Microgel Bioconjugates for Cancer Cell Targeting
William Blackburn 1 , Erin Dickerson 2 , John McDonald 2 , L. Lyon 1 3
1 Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractThe targeting of cancer cells has become an intense focus of research, as current cancer therapies lead to numerous side effects. Delivering cancer drugs to only cancer cells would greatly reduce the adverse effects, while also reducing the amount of a drug needed to kill the cancer cells. Cancer cells often overexpress receptors on the cell surface as a means to acquire additional nutrients. We utilize these receptors to deliver hydrogel nanoparticles to the cancer cells. The synthesis of core/shell poly(N-isopropylacrylamide) (pNIPAm) and poly(N-isopropylmethacrylamide) (pNIPMAm) hydrogel nanoparticles with radius of gyration near 50 nm is described. The particle size and volume transition were measured by dynamic light scattering and multi-angle laser light scattering. To enable in vitro studies of cellular uptake, the particles contain 4-acrylamidofluorescein (AFA) in the core as a fluorescent marker and N(3-aminopropyl)methacrylamide (APMA) in the shell, to allow folic acid or peptide sequence (RGD or YSA) coupling to the microgels. The ligand is then used to target the particles to cancer cells.We have shown that particles conjugated with one of the ligands are efficiently taken up by their target cells preferentially over particles that contain no targeting ligand. Particles conjugated with these various targeting moieties have been shown to be taken up in a variety of in vitro test beds; folate-labeled particles are taken up by KB and HeLa cells, while particles with RGD on their surface were taken up by M21 cells and particles conjugated with YSA were taken up by HEY cells. Fluorescent microscopy was used to visualize the uptake. These results suggest that these core/shell hydrogel nanoparticles may be efficient delivery vehicles for anti-cancer drugs. The results also suggest that multiple forms of cancer can potentially be targeted with our methods.
3:45 PM - T10.6
Biomimetic polymeric vesicles for efficient DNA delivery
Giuseppe Battaglia 1 , Hannah Lomas 1 , Irene Canton 1 , Steven Armes 2
1 Engineering Materials, University of Sheffield, Sheffield United Kingdom, 2 Chemistry, University of Sheffield, Sheffield United Kingdom
Show AbstractWe present a novel gene delivery vector based on the ability of a synthetic amphiphilic block copolymer to mimic biological phospholipids by forming membrane-enclosed structures, specifically nanometer-sized vesicles. We report the use of a pH-sensitive diblock copolymer that forms vesicles at neutral pH, and binds to DNA to form a stable complex at endocytic pH. The responsive nature of the polymers was used to encapsulate DNA and the vectors formed from these polymeric vesicles have been shown to transfect both animal and human primary cells with a very high degree of efficiency through the triggered collapse of the vesicle and the formation of polymer DNA complexes