Biological materials naturally display an astonishing variety of sophisticated nanostructures that are difficult to obtain even with the most technologically advanced synthetic methodologies. Inspired from nature materials with hierarchical structures, many functional materials are developed based on the templating synthesis method. This review will introduce the way to fabricate novel functional materials based on nature bio-structures with a great diversity of morphologies, in State Key Lab of Metal Matrix Composites, Shanghai Jiao Tong University in near five years. We focused on replicating the morphological characteristics and the functionality of a biological species (e.g. wood, agriculture castoff, butterfly wings). We change their original components into our desired materials with original morphologies faithfully kept. Properties of the obtained materials are studied in details. Based on these results, we discuss the possibility of using these materials in photonic control, solar cells, electromagnetic shielding, energy harvesting, and gas sensitive devices, et al. In addition, the fabrication method could be applied to other nature substrate template and inorganic systems that could eventually lead to the production of optical, magnetic. or electric devices or components as building blocks for nanoelectronic, magnetic, or photonic integrated systems. These bioinspired functional materials with improved performance characteristics are becoming increasing important, which will have great values on the development on structural function materials in the near future.

The National Aeronautics and Space Administration (NASA) is currently evaluating composite materials for primary and secondary structures. Composite materials are of great interest to NASA due to the potential significant mass savings they would bring, resulting in more efficient deep space exploration. A principal concern is that of lack of damage tolerance, where nearly imperceptible cracks can have drastic effects on structural integrity. To compensate, composites structures are currently designed to be thicker and heavier than would otherwise be required, thus negating the weight savings they promise. Self-healing composites could help improve damage tolerance and in addition can reduce the complexity of composite maintenance while increasing materials performance lifetime and improving reliability. Current work at the Johnson Space Center investigates the use of carbon nanotubes in a thermally activated re-polymerizing matrix in order to develop a self-healing composite.
Composite panels consisting of carbon nanotubes, carbon fibers, and a thermally reversible polymer resin were fabricated and tested. These multifunctional composites exhibit improvements in the thermal, electrical, and mechanical properties. Nanotube additions influence thermal properties through a decrease in the glass transition and increases in the heat capacity, thermal expansion coefficient, and thermal conductivity of the composite. The electrical conductivity is drastically lowered, while storage modulus and toughness are increased. Carbon nanotubes are known to exhibit enhanced microwave heating, and this property is exploited for the heat generation required for healing of the matrix. Incorporation of nanotubes results in better heating efficiency and thermal transport, allowing the composite to be uniformly heated to the target temperature for self healing. Furthermore, microwave irradiation of impacted composites demonstrates the ability to provide visual inspection of the damaged area. Microcracks produced by impaction generate localized heating which are clearly evident in the thermal images of microwave irradiated composites. The ability to use microwaves to observe barely visual damage provides the capacity for damage detection and real-time health monitoring of the healing process. Thus, carbon nanotubes embedded in a thermally reversible polymer matrix can result in a multifunctional nanocomposite with healing and health monitoring capability.

The use of biological materials as templates for functional molecular assemblies is an active research field at the interface between chemistry, biology, and materials science. We demonstrate formation of gold nanofiber films on beta-sheet peptide domains assembled at the air/water interface. The gold deposition scheme employed a recently-discovered versatile chemical process involving spontaneous crystallization and reduction of water-soluble gold-thiocyanate complex upon anchoring to surface-displayed amine moieties (Morag et al, Advanced Functional Materials, 2013, DOI: 10.1002/adfm.201300881). We show that an interlinked network of crystalline Au nanofibers is readily formed upon incubation of the Au(III) thiocyanate complex with the peptide monolayers. Intriguingly, the resultant films were optically transparent, enabled electrical conductivity, and displayed pronounced surface enhanced Raman spectroscopy (SERS) activity, making the approach a promising avenue for construction of nano-structured films exhibiting varied practical applications and functionalities.

In this study, biodegradable nanofoams were produced using cellulose nanofibrils (CNFs) and starch (S). The availability of high volumes of CNFs at lower costs is rapidly progressing with advances in pilot-scale and commercial facilities. The composite foams were produced using a freeze-drying process with CNF/S water suspensions ranging from 1 to 7.5 wt. % solids content. Microscopic evaluation showed that the foams have microcellular structure includes foam walls covered with CNF`s. Microscopic evaluation of the nanofibrils and pore sizes at the foam walls showed no difference among the composites (CNF reinforced starch foams), with average values from 20 nm to 100 nm for pore size diameters and 30 nm to 100 nm for fibril diameters. The physical, mechanical and thermal properties of the CNF/S composite foams were determined according to ASTM standards. The resulting CNF/S composite foam were determined to have an open-cell structure with densities ranging from 0.012 to 0.082 g/cm3 with corresponding porosities between 93.46% and 99.10%. Thermal conductivity ranged from 0.041 to 0.054 W/m-K. Changes in the solids content and CNF/S ratio had little impact on thermal conductivity of the foams. The mechanical performance of the foams produced from the unreinforced starch control was extremely low and the material was very friable. The addition of CNF to starch produced foams, which exhibited structural integrity. The 1.5% CNF-6% starch combination showed significantly better mechanical properties (average of 2530 kPa modulus of elasticity, 6590 kPa modulus of rupture, 907 kPa compression modulus and 3330 kPa compressive strength) when compared with the other composite formulations. The mechanical properties of materials increased with an increase in solids content and CNF/S ratios.

Synthetic nanocomposites using carbon nanostructures such as carbon nanotubes, graphene, or graphene oxide as the load-bearing units within a polymer matrix are promising structural materials due to their potential for high strength and stiffness. However, the mechanical properties of these macroscale composites are presently limited by many types of flaws and relatively weak interfaces, preventing them from achieving high strengths comparable to their parent nanostructures. Because these carbon-based nanofillers comprise of particles that are non-uniform in composition, structures, and morphologies, and their distribution within a composite are difficult to control, we choose to fabricate nanocomposites that are flaw-tolerant, rather than flawless. In this talk, we describe the fabrication, mechanical measurements, and structure-property relationships of multilayer graphene oxide-polymer composite films with alternating soft, crack-hindering polymer layers and stiff, load-bearing graphene oxide layers. This structure is inspired by that of sponge spicules[1], where periodic lamellae of soft protein and hard mineral hinder crack propagation, increasing strength and toughness[2,3]. We find multilayer films fabricated in this fashion have double the strength of pure graphene oxide films without sacrificing stiffness, and that employing an optimal polymer layer thickness can maximize both stiffness and strength. Finite-element analysis of the multilayer film reveals the stress redistribution that occurs around a broken graphene oxide layer, providing insights into the statistical nature of the strengths of these multilayer films. This work was supported by the ARO MURI (Award # W991NF-09-1-0541).
1. Woesz, A., et al., J. Mater. Res. 2006, 21, 2068-2078.
2. Fratzl, P., et al., Adv. Mater. 2007, 19, 2657-2661.
3. Kolednik, O., et al., Adv. Funct. Mater. 2011, 21, 3634-3641.

The huge diversity of hierarchical micro-/nano-scale rigid structures existing in biological systems is increasingly becoming a source of inspiration of materials scientists and engineers to create next generation advanced functional materials. Recently, accompanied with the development of nanotechnology, some biologically hierarchical rigid structures have been duplicated and mimicked in artificial materials through hierarchical organization of micro-/nano-scale building blocks. We will report several facile synthetic protocols for one-pot controlled synthesis of several kinds of unique nanoscale building blocks, including ultrathin nanowires, nanoplates, and magnetic nanoparticles, conducting nanocables, and carbon-based nanostructures. Then, we discuss how to assemble these nanoscale building blocks into ordered assemblies as well as their functionalities. These assembled structures based on bio-inspired approaches will find potential applications in different fields.

A recent theoretical insight (Alugrave; A., Engheta N., 2009) attracting attention finds that a symmetric cluster of metal nanoparticles (NPs), viewed as a “metamolecule,” may resonantly enhance local optical magnetic fields dramatically. The challenge to realizing such structures is the difficulty that traditional lithographic techniques face when assembling 3-dimensional (3D) clusters (Shafiei F. et al., 2013). The 3D nanoclusters are naturally formed with our bottom-up self-assembly techniques. We employ viral proteins as scaffolds (Soto C. M, Ratna B. R, 2010) to direct the metamolecule self-assembly because viruses (i) come ready-made at the correct size scale (10s of nm cores); (ii) can be made in large quantities with minimal defects and low cost, (iii) can be genetically or chemically modified to provide a range of desired symmetries and to tune the wavelength and strength of optically induce magnetic moment.
We present the preparation of nanoclusters using cowpea mosaic virus (CPMV) as a scaffold. CPMV was decorated with gold nanoparticles (Au-NP) of various sizes. Two methods were employed to obtain monodisperse Au-NPs and compared with commercial Au-NPs. Dynamic light scattering (DLS) was used to monitor the reaction progress and transmission electron microscopy (TEM) to image resultant CPMV nanoclusters. Electromagnetic simulations were performed using COMSOL multiphysics software package. Simulations show that the plasmonically coupled NPs of the CPMV nanocluster exhibit a resonance response in the visible. Simulations were compared with empirical spectroscopy results. CPMV nanoclusters showed a red shift of the Au-NPs plasmon peak along with a new broad band at longer wavelengths; agreeing with the simulations. The broad band is associated to the nanoparticles coupling in the CPMV nanocluster. These results open the possibility of producing metamolecules in sufficient amounts for the assembly of CPMV nanoclusters into novel optical materials.

The use of biomolecules as scaffolds for organizing inorganic and organic nanomaterials addresses the challenge of integrating multiple functional units with molecular-level control over their spatial arrangement. This approach has been used to build optically active nanostructures in which the plasmonic fluorescence is controlled via the precise arrangement of chromophores and plasmonic antennae. However, previous studies using metal nanoparticles less than ~60nm in diameter reported a predominance of fluorescence quenching due to the small scattering cross-sections of the particles.
In this talk, we will discuss our recent work on the design of hierarchical plasmonic structures built on virus capsid scaffolds and DNA origami tiles. In our design, the virus capsid enables precise control over the three dimensional arrangement of fluorescence dye molecules, whereas the DNA origami tiles provide well-defined control over the distance between the capsid and gold nanoparticles (AuNPs). Using finite-difference time-domain (FDTD) numerical simulations and multimodal single-particle imaging measurements, we show that the judicial design of these hierarchical structures can place a significant fraction of the dye molecules near the hot spots of the AuNPs and thereby effectively increase the fluorescence intensity within the typical AuNP quenching regime. The results also show that fluorescence enhancement is promoted by increasing the AuNPs size.
Our future studies will focus on improving the design of these hierarchical plasmonic structures by exploring an extended variety of metallic species, nanoparticle shapes, and spectral properties of the dye molecules. Identifying alternative viral capsid scaffolds with optimal geometry, rigid structural integrity, and versatile addressability is also currently underway in order to extend the function of future designs. We envision that this work will lead to a better understanding of the antenna effects of photon absorption and emission, allowing for future construction of multicomponent plasmonic systems based on bioinspired structured materials.

Patterned biological particles are widely observed in nature from pollen grains on the millimeter scale to viruses on the nanoscale. However the parallel synthetic fabrication of such precisely patterned three dimensional structures with soft materials such as polymers and gels which could provide significant value in biomanufacturing, drug delivery, aggregative self-assembly and the colloidal sciences is challenging. We describe the parallel synthesis of soft-polyhedra with precisely patterned biomolecules on their faces using a combination of top-down lithographic patterning, molding and bottom-up self-assembly methods. Polyhedra are the most fundamental solids that have been studied since the days of Plato over 2000 years ago. In nature, many viruses have polyhedral geometries and biomolecule patterns on viruses are important in host cell interactions and pathogenicity. In our approach, we utilize the self-assembly of plates by an origami inspired paradigm [1] as well as molding and contact printing to create these structures with a wide variety of soft-materials such as cross-linked gels, stimuli responsive polymers and even cell laden gels. We anticipate that due to the wide range of soft-materials, sizes, and topographic or biomolecule patterns that these polyhedra could be used in a wide range of applications.
References: [1] S. Pandey, M. Ewing, A. Kunas, N. Nguyen, D. H. Gracias, G. Menon, Algorithmic design of self-folding polyhedra, PNAS 108, 50, 19885 (2011).

Peptide driven synthesis and assembly of inorganic nanomaterials has received much attention in the field of materials science. While there is a large amount of literature available on the fabrication of nanoparticles and assemblies using peptides, comparatively little is known the nanomaterial&’s in-depth atomic structure. Such information is an important prerequisite for the design of peptide sequences which can ultimately result in nanomaterials with tunable properties. In this work, atomic-scale structural information was elucidated for peptide-capped Pd nanomaterials using extended X-ray absorption fine-structure spectroscopy (EXAFS), high-energy X-ray diffraction (HE-XRD), and pair distribution function (PDF) analysis. Peptide synthesized Pd nanoparticles have been previously created using the Pd4 peptide (TSNAVHPTLRHL) and were shown to perform Stille C-C coupling reactions on various aryl halides at high turnover frequencies (TOFs) with low Pd loadings under non-traditional ambient conditions. By substituting the histidines at the 6 and/or 11 positions to either weakly interacting alanines or strongly interacting cysteines different TOFs were observed for the coupling of 4-iodobenzoic acid with PhSnCl3. As all the Pd nanoparticles were approximately the same size, variations in catalytic activity must be influenced by structural variations imposed by the peptide and/or the peptide&’s orientation on the Pd surface. Using EXAFS, the local chemical environment of peptide capped Pd nanoparticles and pre-reduced complexes was probed and correlated their corresponding catalytic activity. HE-XRD patterns were also obtained for the peptide-capped Pd nanoparticles and analyzed in terms of their PDF. While all materials resemble the bulk fcc lattice, certain degrees of structural disorder are observed for each Pd nanoparticle system. Atomic-scale Pd nanoparticle data was obtained by modeling the PDFs using reverse Monte Carlo (RMC) simulations. Three-body and four-body correlation functions were derived from modeled Pd nanoparticles and used to describe differences in catalytic properties. Taken together, such analysis yields important atomic-scale structure information, which assists in the fundamental understanding of these materials&’ properties and which can be used to create Pd nanomaterials with tunable properties through peptide sequence design.

Bio-inspired materials and devices are attracting increasing interest
because of their unique properties, which have paved the way to many
significant applications. Ion channels that exist in living organisms
play important roles in maintaining normal physiological conditions
and serve as “smart” gates to ensure selective ion transport. Thus,
designing a system that simulates these complex processes in living
systems is a challenging task for nanoscience. The gating property
nanochannel is realized by modifying the surface with functional
molecules that can respond to external stimuli. Recently, we have
developed various responsive nanochannel systems which were controlled
by our designed biomolecules or smart polymers responding to the
single external stimulus, provided an artificial counterpart of
switchable protein-made nanochannels. Most recently, we developed
dual-responsive single nanochannel systems, and compared with the
single external stimulus systems, the present work is more complicated
and moves one step farther for the development of “smart” nanochannel
systems for real-world applications. These intelligent nanochannels
could be used in energy-conversion system, such as photoelectric
conversion system inspired by rhodopsin from retina or bR, and
concentration-gradient-driven nanofluidic power source that mimic the
function of the electric eels. Learning from nature is a constant
principle for there are numerous mysterious properties in nature,
which have developed over millions of years of evolution and will give
us inspiration to develop novel functional interfacial materials.

The unique properties of the kinesin/microtubule pair, where the kinesin motor protein uses energy harnessed by the hydrolysis of adenosine triphosphate (ATP) to move along microtubule filaments, makes it quite suitable in size for lab-on-a-chip devices; and therefore, a promising tool in the development of synthetic nano-machines.
In order to engineer tailor-made artificial transport systems capable of directional transport of nanoobjects in a cell-free environment, biotinylated kinesin protein can be functionalized with nanoparticles via biotin-streptavidin linkages. Relying on the ligand exchange method, magnetite (Fe₃O₄) nanoparticles were designed bearing a free amine surface that can be chemically linked to streptavidin and consequently, coupled to the kinesin motor protein.
The movement of hybrid Fe₃O₄ magnetic nanomaterial over microtubules filaments could be monitored under fluorescence microscopy by labeling the streptavidin linker with fluorescein, and accordingly, run lengths and velocities of engineered nanotransport devices were monitored. These experiments shed light on the transport of functional hybrid nanoparticles by kinesin-based molecular shuttles to be potentially employed as drug delivery systems.

Hemostatic materials, at exerting direct pressure to prevent bleeding, allow time to activate the intrinsic coagulation cascade of the organism, to achieve hemostasis. That is, they generate a mechanical barrier or a matrix to which platelets can adhere, stimulating coagulation. Composite nanofiber materials are attractive for creating new materials with new or enhanced properties compared with single materials. Poly (vinyl alcohol) (PVA) is widely used in biomedicine, due to its excellent water-solubility, high biocompatibility, hydrophilicity, as well as some mechanical properties, besides being a good stabilizer of noble metal particles. The incorporation of nanoparticles can improve the performance of the mechanical, thermal, optical, electrical, antimicrobial, antifouling and catalytic properties of a polymer. Compared with other nanomaterials, silver nanoparticles (AgNPs) have an excellent antibacterial action, damaging the membrane structure of bacterias and causing changes in their permeability and breathing, through the release of silver ions and the generated reactive oxygen species. Graphene oxide nanosheets (GrO) is used as a matrix can induce binding capability in AgNPs and thus enhance its antimicrobial activity.
In the present work, we will introduce a hemostatic material, consisting of PVA nanofibers obtained by electrospinning , to obtain enhanced mechanical properties and, at the same time, antimicrobial activity. The nanofibers are reinforced with the hybrid nanomaterial Graphene Oxide nanosheets/Silver Nanoparticles (GrO/AgNPs). The synthesis of graphene oxide sheets was achieved successfully by the modified Hummer's method. A novel environmentally-friendly method was successfully employed for the synthesis of silver nanoparticles, by using geranium extract as reducing agent and ethylene glycol. The results of UV-vis spectroscopy suggest that the synthesis method used to the hybrid material was adequate. Optimal conditions for the synthesis of AgNPs were achieved by changing the ethylene glycol by ethanol in both hydrothermal and reflux conditions. The hydrothermal yields a larger diameter of the nanoparticles and the hybrid material had a uniform distribution of the nanoparticles on the graphene oxide nanosheets.

Shape, size, and surface modification control functionality of metal nanocrystals in many applications. Metal nanocrystals of different shape from in-situ approaches facilitate the exploration of new functionality in sensors, catalysts, optic, and electronic devices while the underlying shape-directing mechanisms still remain poorly understood. Short polymers of naturally occurring amino acids have been employed as efficient regulating agents to engineer the structure of nanocrystals through recognition of crystallographic facets. A naturally selected peptide named T7 (Acyl-TLTTLTN-Amide) was reported to bind to platinum nanocubes, and to yield a high percentage of single crystalline platinum cubes in a reductive synthesis route. In this study, we explain the mechanism of specific cube recognition and of cube formation from cuboctahedral seed crystals using molecular dynamics simulation, synthesis, and characterization. The higher mobility of water molecules near the edges of nanocubes, compared to the center of the facets, as well as by a unique match of polarizable atoms in T7 (N, O, C) to the square pattern of epitaxial sites plays a major role for peptide adsorption onto {100} facets. These contributions support adsorption of peptide near the edges (-5.8±0.8 kcal/mol) while inner areas of nanocube facets and extended {100} surfaces repel the peptide at low concentration (+13±2 kcal/mol). In addition, the peptide concentration was found to be a crucial factor. On extended {100} surfaces, multiple T7 peptides interact with each other and turn repulsion into attraction upon increase in concentration. The main interaction mechanism of T7 with even and shaped surfaces is anticipated as soft epitaxy, supported by the charge-neutrality of the peptide (protection of the N and C termini by acyl and amide groups) and by the absence of thiol groups that could form covalent bonds. On cuboctahedral seed crystals, T7 peptides preferentially locate on {100} facets at intermediate surface coverage in correlation with a maximum yield of Pt nanocubes in reductive synthesis, while about equal distribution on {100} and {111} facets is found for low and high concentration. Selective stabilization of {100} facets is specific to peptide T7 and in contrast to another peptide S7 (Acyl-SSFPQPN-Amide) that strongly stabilizes {111} facets over a wide range of concentration in experiment and simulation. The visualization of facet preferences and estimation of binding energies of peptides on metal nanostructures in atomic resolution using the INTERFACE force field demonstrates considerable capabilities of high performance simulations.

Dental pulp stem cells (DPSCs) are ectomesenchymal cells that have been shown to be multipotent and capable of generating odontoblasts, osteoblasts, adipocytes and neurons. On tissue culture plastic these cells show a dexamethasone dependent differentiation, which we found could be alleviated by growth on thin films of spun cast polybutadiene. As we known, graphene, as a new biocompatible material, retains some unique properties such as high electrical conductivity, elasticity with the ability to absorb various molecules including potential inducers of differentiation. It therefore holds tremendous potential for a wide variety of biomedical applications. We are currently exploring the use of graphene and graphene oxide introduced into the media and incorporated into spun cast polymer thin films. Differentiation is being monitored immunohisotchemically (osteocalcin expression) and biomineralization is being assessed (Alizarin red and SEM/EDX). We have found no cytotoxic effects on DPSC with graphene added to the media at concentrations up to 0.1mg/mL.

Three-dimensional (3D) porous metal nanostructures gain increasing attention for their potential applications to energy systems, sensors, electronic devices, etc. However, efficient, robust immobilization of the nanostructures within 3D scaffolds is still very challenging. Here we introduce a facile templating method to synthesize and immobilize noble metal nanostructures using catechol-grafted polymer nanofibers as a bio-inspired reactive template. A redox-active polymer, catechol-grafted poly(vinyl alcohol) (denoted as ‘PVA-g-ct&’), is synthesized and electrospun into reactive nanofibers by electrospinning. The grafted catechol is inspired by mussel adhesive proteins, which mediate binding and reduction of noble metal ions on the nanofiber templates. Highly open porous silver nanostructures are spontaneously generated by simply immersing a PVA-g-ct nanofiber mat into an aqueous solution of silver ion precursors under ambient conditions due to the reducing capability of the grafted catechols, while gold and platinum ions are partially reduced and complexed with the nanofiber templates, requiring an additional thermal treatment for their complete reduction into solid metal nanostructures. In addition, silver-gold and silver-platinum hybrid nanostructures are generated using the pre-synthesized silver nanoparticles on the PVA-g-ct nanofibers by sequential treatments with metal ion precursors. We expect that the bio-inspired reactive nanofibers can be used as an attractive template for the synthesis and immobilization of metal nanostructures within 3D porous structures, providing a wide range of functional nanomaterials for biosensors, catalytic systems, and electronic devices.

Increased in vivo nanoparticle circulation times would be beneficial to sustained systemic drug delivery, active and passive targeting of both tumor-located and circulating cancer cells, bio-imaging, as well as the prevention of viral and bacterial spread. Accurate determination of mesoporous silica nanoparticle (MSN) biodistribution is often confounded by aggregation, which masks the behavior of individual nanoparticles and results in rapid uptake and clearance by the mononuclear phagocyte system (MPS). In mice, the notion that nanoparticles quickly accumulate in the liver, spleen, and kidney is widely accepted; however, by altering the size and surface chemistry of MSNs we are able to shift biodistribution systematically. MSN synthesis using a dual modification polyethylene glycol (PEG) plus trimethylsilyl chloride (TMS) enables the formation of particles that are uniform, nano-sized, and colloidally stable in diverse media, including simulated biological fluids. Using whole animal fluorescent imaging, fluorescent microscopy, TEM, SEM, and ICP-MS we demonstrate that 25 and 50 nm particles can remain systemically distributed, thereby minimizing their accumulation in MPS organs, as compared to 150 and 250 nm particles synthesized with identical surface chemistries. To further alter organ accumulation and extend circulation time via innate immune system evasion, we shielded MSNs with red blood cell derived membrane vesicles. To accomplish this, we fused membrane vesicles, derived from mouse and chicken red blood cells, to the surfaces of monodisperse 50 - 250 nm MSNs, characterized the nanoparticles, and measured circulation time and systemic distribution using both an ex ovo chicken embryo model and in vivo mouse model. Our results reveal the individual effects of particle size and surface chemistry on biodistribution and clearance.

Light triggered changes in biological molecules which enable various functions such as vision, photosynthesis and heliotropism have long inspired materials chemists to mimic these phenomenon&’s to create new functional materials and devices. The ability to detect and translate the conformational changes in the small molecule retinal into the macroscopic effect of vision exemplifies a very powerful and elegant approach to the design of new functional materials. Nanocarbon materials such as nanotubes and graphene, with their exceptional electrical conductivity, robustness and small size, have attracted interest as possible nanoscale replacements for inorganic semiconductors. We have demonstrated an optically active nanotube-hybrid material by non-covalent functionalization of single-wall nanotubes with an azo-based chromophore. Upon UV illumination the chromophore undergoes a trans to cis isomerization leading to charge redistribution near the nanotube. The resulting change in the local electrostatic environment led to a shift in the threshold voltage and increased conductivity of the nanotube. Graphene shares many of the same excellent materials properties as carbon nanotubes; however, unlike nanotubes, graphene can be grown over large areas with excellent control over uniformity and without concern for alignment and organization, which advantageously makes its processing more similar to that of traditional semiconductors and therefore also more industrially scalable. We demonstrated the reversible modulation of doping in graphene using light switchable azobenzene containing molecules tethered to the surface via π-π interactions with a pyrene group. As the molecules switch reversibly from trans to cis form the dipole moment also changes, and hence the extent of doping in graphene. The sensitivity of the readout by graphene in a given transistor architecture is striking, as a relatively small change in electrostatic potential due to isomerization of molecule results in a 40 times voltage amplification. We outline the characterization of these interfaces by Raman spectroscopy, electrical measurements, and by Second Harmonic Generation, to probe the molecular orientation, and charge transfer characteristics to gain mechanistic insight into this effect.

Polymeric membranes are a promising molecular separation technology, but current filtration membranes separate solutes by size, compounded in some cases by charge effects. They cannot effectively separate small organic molecules of similar size. In contrast, biological transport systems such as ion channels, porins and nuclear pore complexes exhibit exceptional separation selectivity based on specific interactions between the membrane nanochannels and a target solute. We aim to develop synthetic polymer membranes that separate organic molecules based on their chemical features, inspired by the structure of biological pores. These systems combine two important structural features to achieve high selectivity: 1. Constricted pores similar in diameter to the target compound (~1 nm for ion channels and porins); 2. Functional groups lining the pore that interact with the target during passage (e.g. spatially arranged hydrogen bonding groups in maltoporin LamB). We mimic this structure by synthesizing novel amphipilic comb copolymers that microphase separate to form ~1 nm nanochannels due to the immiscibility of the backbone and side-chains. The side chains contain functional groups able to preferentially interact with the solute through hydrogen bonds (such as ether oxygens or tertiary amines) and initiate a facilitated transport mechanism. We synthesized such copolymers with polyacrylonitrile by free radical and atom transfer radical polymerization (ATRP) methods. Solutions of these polymers are coated onto an ultrafiltration (UF) membrane support, to become the selective layer of thin film composite (TFC) nanofiltration membranes. Upon coagulation of the coating, microphase separation occurs between the hydrophobic backbone and hydrophilic side chains, as documented by differential scanning calorimetry (DSC). This phase separation allows the formation of a percolated network of nanochannels of the desired size, polarity and hydrogen-bond selectivity, through which only the target solute can selectively interact. The membrane nanostructures are characterized by X-ray scattering. Membrane selectivities are probed via diffusion tests of dye pairs, with similar size and shape but different hydrogen-bonding properties, such as phloroglucinol which contains -OH groups, and mesitylene which contains -CH3 groups instead. Diffusion kinetics is followed with UV-Vis spectrophotometry. We found that organic molecules that contain hydrogen bond accepting groups (e.g. -OH, -COOH) diffuse faster through these membranes than those that do not. These systems are promising first examples of membranes that separate small molecules based on their chemical features.

Introduction
To understand the role of physical property of microenvironment surrounding cells for changes in cellular functions, we prepared cytocompatible micro-sized hydrogels composed of bioinspired phospholipid polymer. This hydrogels could be formed spontaneously by mixing aqueous solutions containing poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate (BMA)-co-4-vinylphenylboronic acid (VPBA)] (PMBV) and poly(vinyl alcohol) (PVA). Moreover, the PMBV/PVA hydrogel could be reversibly dissociated by addition of natural sugar compound. Its crosslinking relies on specific covalent binding between VPBA units in the PMBV and hydroxyl groups in PVA. Because this crosslinking reaction occurs under physiological condition (neutral pH, room temperature), living cells can be encapsulated in the hydrogel without adverse effects. The use of microfluidic device allowed for encapsulating cells in the microgel and controlling cell number in the microgel. These microgels were suitable as matrices to determine the relationship between physical properties around cell and cellular functions (e.g., proliferation, differentiation). Here we will report, elasticity and molecular diffusivity of the PMBV/PVA hydrogels related to cell response.
Materials and Method
The molecular weight (Mw) and molar ratio of MPC/BMA/VPBA of the PMBV were 40 kDa and 0.71/0.13/0.16, respectively. The Mn of PVA was 4.2 kDa. Five-wt% PMBV containing cells and 1.0-5.0 wt% PVA in cell culture medium were introduced into microfluidics and mixed together to make microgels. Diffusion coefficient of fluorescence-labeled proteins in the microgels with varied pre-polymer concentration was measured by fluorescence correlation spectroscopy. Elastic modulus of the hydrogels was determined by dynamic mechanical analysis. Cell proliferation behavior was evaluated by using single HeLa cell in the microgel.
Results and Discussion
The MPC polymers are well-known to inhibit cell attachment and cell response on the surface. Therefore, PMBV/PVA hydrogel enables the specific evaluation of the physical effects on cell response in the absence of cell-matrix interaction. The microfluidics produced spherical hydrogels with the diameter of 10-100 µm, and encapsulated single to several cells in the microgels. Elasticity of the hydrogel increased from 24 to 367 Pa as the PVA composition increased. This range of elasticity was similar to that of fat tissue or brain. The diffusivity of the proteins in the microgel were in the order of 10-7 cm2 s-1, which is similar to that in the native extracellular matrix. While preliminary experiment revealed that cell proliferation behavior did not change in this diffusivity range. Therefore, elasticity can be considered as a primary factor in modulating cell proliferation. The PMBV/PVA microgel expects to be a potent candidate for artificial cellular microenvironment allowing for regulating cellular functions by changes in physical properties.

[Introduction]Tissue engineering is most usually assigned as the application of medical science and engineering principles in the design, erection, interpolation, growth and maintenance of living tissues. Normally, a three-dimensional structure, called scaffold, is necessary in tissue engineering applications since bioartificial tissues involve three-dimensional structures with cell multitude. The evolution of the field of tissue engineering goes in parallel with the coherent demand for new scaffolding materials with definite properties such as controlled porosity and pore size distribution, biocompatibility and biodegradation. Among these materials, natural polymers predispose especially interest because of their biocompatibility, biodegradation, and exuberance. Polysaccharides are natural polymers that include cellulose, chitin, and starch. Cellulose is the most abundant polysaccharide found on earth, but cellulose has many limitations in utilization and manipulation such as its poor solubility in water or organic solvent. We found that aldehyde introduced polysaccharide via Malaprade oxidation can be degraded at the glycoside bonds through the reaction with amino groups. In this study, we focus on the control of cellulose scaffolds degradation by oxidation and reaction with amine species.
[Materials and methods] 1-Butyl-3-methylimidazolium chloride, an ionic liquid, was used to dissolve cellulose at 100C and maintained at room temperature for 7 days, providing flexible cellulose hydrogels. The cellulose scaffold was modified and oxidized using periodate oxidation (Malaprade oxidation), oxidation of carbohydrate by glycol cleavage to provide dialdehyde. Aldehyde groups introduced into cellulose were quantified by simple iodometry. During immersion of the cellulose scaffolds in the amino acid solution, the mass loss of the scaffolds was evaluated and the molecular weight variation of the eluted oxidized cellulose was determined by gel permeation chromatography and mass spectrometry.
[Results and discussion] Porous cellulose hydrogel scaffold were developed by using ionic liquid as a solvent. The aldehyde groups were well introduced by periodate oxidation. The introduced aldehyde groups reacted with amino groups to form Schiff base. The cellulose scaffolds after oxidation degraded in the amino acid solution. And the degradation was controlled by increasing the concentration of periodate, time of reaction and concentration of amino acids. Partially oxidized cellulose is the chemical properties of the oxidized residues and, in particular, the hydrolytic lability that may provide a basis for biomaterial with increased biodegradability. The results indicated that cellulose scaffold completely degraded in 1% periodate with 5, 10, and 15% glycine, partially degraded in 1% glycine in 16 hours. Successfully we developed the cellulose scaffolds by controlling the degradation.

Carbohydrate-based polymers are widely used in biomedical applications, including drug delivery and tissue engineering. Though most polysaccharides used today are isolated from natural sources, synthetic polymers offer several advantages including control over molecular weight and distribution and the ability to modify the polymer at the monomer level. To this point, we have developed the synthesis of a new type of carbohydrate polymer using a ring-opening polymerization method, in which glucose is linked via an alpha-amide bond to give a poly-amido-saccharide (PAS). PASs maintain many of the features of natural polysaccharides, including a defined stereochemical conformation and pyranose rings in the mainchain, but the amide rather than ether linkage provides unique characteristics. Further modification of these chiral polymers via controlled oxidation of the primary alcohol to the carboxylic acid and a second polymerization of the initiating group to yield glycopolymers creates a variety of new materials with very different properties. The structure, thermal, and mechanical properties of these polymers are investigated, and their potential in different biomedical applications is assessed, particularly in the area of protein stabilization.

Glycerol based polymers are of wide spread interest for industrial, cosmetic, and pharmaceutical applications. Poly(1,3-glycerol carbonate) based biomaterials are being investigated as drug-loaded buttressing films for the prevention of tumor recurrence after surgical resection, nanoparticles for drug delivery, and coatings for prevention of seroma. Poly(1,2-glycerol carbonate)s, however, are far less explored. Herein, we report a facile and efficient method to synthesize linear atactic poly(1,2-glycerol carbonate)s using a readily available starting material benzyl glycidyl ether. We also report the hydrolytic kinetic resolution of benzyl glycidyl ether using Jacobsen&’s catalyst and subsequent polymerization to afford the chiral isotactic polymer. Poly(1,2-glycerol carbonate)s degrade significantly faster than poly(1,3-glycerol carbonate). The significantly increased degradation rate fulfills an unmet need for readily degradable biocompatible polycarbonates for the biomedical and pharmaceutical industry.

We have investigated a bio-resin made of a keratin and fibroin protein, which derived from feathers and animal fibers. Fine powder of these proteins can be resinified by hot pressing at 100-180°C after adding water. This resinification is attributed to the crosslinking reaction by the formation of dehydroalanine residues under hydrothermal environments. These bio-resins have excellent properties such as high glass transition temperature, thermal conductivity and mechanical strength. These bio - resins are suitable for environmental friendly materials for housing and electronic components. However, these protein powders are expensive.
In Japan, the amount of textile waste has reached 1.7 million tons/year, and most of them are incinerated or subjected to a landfill disposal. 20% of textile waste is reused and recycled as industrial dusting cloths, heat insulators for automobiles, refuse derived fuels and raw materials for nylon or polyester fibers. Therefore, we investigate the fabrication of bio-resins using textile wastes, wasted feathers and wool from poultry farms and meat processing plants, which contain keratin and fibroin protein.
In the case of wool, (1) unstained pure wool yarns were crushed using a planetary ball mill apparatus; (2) 15 wt% distilled water was added to the crushed yarns; and (3) the obtained material was heated to 130°C (pressure, 20 MPa; vacuum < 6.0 Pa) using a pulsed-electric current sintering apparatus, and then immediately cooled. Obtained bio-resin exhibits slight brownish transparent colort. After drying, the glass transition temperature of the bio-resin was measured using the TMA and its dielectric properties at an ambient temperature were measured using the parallel-plate electrode method. The glass transition temperature was found to be 165°C. The dielectric dissipation factor (tanδ) gradually increased from 0.02 to 0.05 with increasing the frequency from 10³ to 10⁷ Hz. The relative permittivity gradually decreased from 5 to 4 with increasing the frequency from 10³ to 10⁷ Hz. Further, the obtained bio-resin can be recycled via the mechanically crushing. The glass transition temperature and dielectric properties of this resin were comparable to conventional resins.
In the case of textile waste, twisted union yarns (60% silk and 40% cuprammonium rayon) and silk-mixed spun acrylic yarns (50% silk and 50% acrylic ester) were crushed and sieved to remove cuprammonium rayon and acrylic ester; (2) 20 wt% distilled water was added to the crushed yarns to obtain a slurry-like material; and (3) the obtained material was heated to 150°C (pressure, 20 MPa; vacuum < 6.0 Pa) by using a pulsed-electric current sintering apparatus, and then immediately cooled. The glass transition temperature and dielectric properties of the obtained resin were comparable to those of the resins obtained from wool and feathers. Moreover, the renewability of the silk fibroin resin was confirmed.

The integration of a tripeptide derivative, which is a versatile self-assembly motif, with a ruthe-nium(II)tris(bipyridine) complex affords the first su-pramolecular metallo-hydrogelator that not only self-assembles in water to form a hydrogel, but also exhibits gel-sol transition upon oxidation of the metal center. Surprisingly, the incorporation of the metal complex in the hydrogelator results in the nanofibers, formed by the self-assembly of the hydrogelator in water, to have the width of a single molecule of the hydrogelator. These results illustrate that metal complexes, besides being able to impart rich optical, electronic, redox or magnetic properties to supramolecular hydrogels, offer a unique geometrical control to pre-arrange the self-assembly motif prior to self-assembling. The use of metal com-plexes to modulate the dimensionality of intermolecular interactions may also help elucidate the interactions of the molecular nanofibers with other molecules, thus fa-cilitating the development of supramolecular hydrogel materials for a wide range of applications.

The practical use of chemical sensors is realized in a vast number of applications, such as in industrial processes, environmental studies, agriculture, clinical settings, and military technologies. These applications stimulate huge growth in research into all aspects of high performance sensing. Whilst huge advances in receptor and transduction principles have been made, the ability to detect multiple volatile vapors and trace level molecules in real time is still challenging.

The Naturally formed photonic structures in the wing scales of tropical Morpho Butterflies have begun to provide novel bio-inspiration within the sensing community. In our recent study we have shown that the local chemical environment within the iridescent scales of the Morpho butterfly strongly influences the reflectivity upon low-concentration vapor exposures. Multivariate analysis of the reflectance spectra arising from the preferential absorption of different volatile organic compounds (VOCs) reveals a selective vapor response. This naturally occurring polarity gradient within the hierarchical photonic structure offers exciting prospects for the detection of VOCs using a single functionalized nanostructure, rather than through traditional sensor array approaches.

Here we demonstrate the unique opportunities that arise from utilizing Morpho Nanostructures for sensing through experimental and theoretical results. The vapor-induced differential reflectance spectral features that arise through different incident angles and linear-polarizations will be shown.

Tubular architectures consisting of self-assembled bilayers or monolayers of rationally designed amphiphilic molecules, so-called organic nanotubes (ONTs) have proved to be of significant importance for potential biological, medical, and industrial applications [1]. In contrast to conventional lipid nanotubes with identical inner and outer surfaces, diverse chemical functionalization of the inner surfaces of the ONTs allows us to encapsulate, store, transform, sense, visualize, and to release biomacromolecular guests in the cylindrical nanospace [2]. Furthermore, self-assembled ONTs with 10 nm inner diameters and 1000 nm length can actually provide the confined water volume corresponding to 1 attoliter (aL) [10(-18) liter]. From this attoliter chemistry point of view, we are now focusing on the elucidation of meso-scale host-guest science and engineering by using solid ONTs of 10~100-nm inner diameters with well-defined dimensions and functionalities. Here we discuss current research achievements on the encapsulation, confinement effect, and nano-fluidic and release behavior of anticancer drugs and biomacromolecules in the ONT nano-channels.
Self-assembled ONT from 2-glucosamine derivative carrying the tetraglycine unit with carboxylic acid terminal were able to give a nanocontainer, in which the anticancer drugs (cis-dichlorodiamineplatinum, CDDP) are densely populated on the inner surfaces via endo-complexation. The size dimension of the container proved to be 14-nm outer diameter, 6.7-nm inner diameter, and several micrometers long. Then, we demonstrated efficient loading and prolonged release of CDDP by using the high-axial supramolecular ONT. Next, we found that well-defined inner diameters of ONTs proved to remarkably affect the resistance of confined proteins to heat and to a denaturant. We investigated the dynamic behavior of Green Fluorescence Protein (GFP) involving transportation, diffusion, release and stability in the confined nanospace by using ONT hosts with three different inner diameters (10, 20, and 80 nm). The ONT hosts we employed were prepared by self-assembly of 1-glucosamine derivative carrying an oligoglycine unit with amino terminal. By utilizing an endo-sensing procedure based on fluorescence resonance energy transfer (FRET) between GFP and the interior fluorescence acceptor immobilized on the nanotube inner surface, we directly detected GFP behavior in the nanochannels of the ONTs in real time. As a result, the 10 nm nanochannel allowed us to store GFP most stably and without denaturation under high temperature and high denaturant concentrations, probably due to the confinement effect based on rational fitting of the inner diameter to the size of GFP.
References
[1] T. Shimizu et al., Chem. Rev. 105, 1401-1443 (2005).
[2] N. Kameta et al., Soft Matter, 7, 4539-4561 (2011).

Carbon nanotubes (CNTs) uniquely provide the fundamental requirements for mimicking biological protein channels, which selectively transport chemicals through the cell membrane at rates orders of magnitude faster than a simple diffusion or Newtonian fluidic system. Incorporating comparable transport properties into a mechanically stable solid state device will not only eliminate expensive protein expression and separation steps, but can also provide a wide range of applications such as chemical delivery and sensing, energy generation, and water purification. The atomically smooth and inert structure of CNT walls allow for a nearly frictionless flow of molecules through the nanotube core over large lengths. For instance, water velocity in CNTs shows five orders of magnitude enhancement relative to other conventional materials of similar pore size, thus rivaling that of protein channels. In addition to fast flow rates, transport can be modulated by gatekeeper chemistry using steric hindrance, electrostatic attraction/repulsion, or biochemical state. The selectivity region can be precisely placed at the nanopore entrance by chemically functionalizing carboxylate groups formed at both ends from oxygen plasma cutting. In this study, by measuring the ionic current through individual single-walled CNTs spanning a barrier between two fluid reservoirs, we experimentally demonstrate the similarities between the highly selective and fast passage of ions through individual single-walled CNTs and protein ion channels. We also propose a theoretical model to explain the unique dependence of ionic conductance on electrolyte type and concentration in such systems. Fundamental understanding of nanofluidic systems is essential for elucidating the physical mechanism underlying significantly more complex biological nanochannels.

Carbon nanotube (CNT) pores give a structural and functional mimic of an ion channel, in part because smooth, narrow and hydrophobic inner pores of CNT are remarkably similar to the natural biological pores. Incorporation of CNT pores into the biologically-relevant environments and measurements of ion and proton transport in these assemblies would not only enhance our understanding of molecular transport in these materials systems, but also open up ways to develop novel bioengineering applications. We will describe incorporation of carbon nanotube pores into a lipid membrane and measurement of proton and osmotically-induced ion transport through these model nanopores using dynamic light scattering (DLS) experiments. We also discuss factors that govern and ion rejection in these structures and compare the results with modeling results and measurements in nanotube-based membrane structure. This research was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, and the LLNL LDRD program.

Biomolecular unit cells can be described as small building blocks whose repetition can form the basis of a novel biomolecular material system. The biomolecular unit cell consists of a lipid bilayer interface formed at the contact of two aqueous droplets encased in lipid monolayers. The droplets are surrounded by a hydrophobic organic solvent (Hexadecane), and are sitting on fixed silver-silver chloride (Ag/AgCl) electrodes. Many types of biomolecules such as ion channels can self-assemble in the lipid bilayer interface. Therefore, the Droplet Interface Bilayer (DIB) has been extensively used to systematically study the activity of various biomolecules including alamethicin, bacteriorhodopsin, and many others. Accordingly, other types of biomolecules such as mechanosensitive (MS) channels self-assembled within the DIB should be able to respond to an expansion in the artificial membrane. And therefore can be used as a model system to understand how the structure of the protein and its incorporation into the unit cell affects its transduction properties. MS channels residing in the cytoplasmic membrane of Escherichia coli respond to a mechanical tension in the cell membrane, and fall under three categories according to their conductance level. MscL, the mechanosensitive channel of Large conductance, has been studied both in vivo and in vitro using patch-clamp methods.
This paper presents first attempts to study of the MscL channel activity in an artificial DIB system. A novel and simple technique is developed to characterize the behavior of an artificial lipid bilayer interface containing MS channels. The experimental setup is assembled on an inverted microscope and consists of two micropipettes filled with PEG-DMA hydrogel and containing Ag/AgCl wires, a cylindrical oil reservoir glued on top of a thin acrylic sheet, and a piezoelectric oscillator actuator. Using this technique, dynamic tension can be applied by oscillating axial motion of one droplet, producing deformation of both droplets and area changes of the DIB interface. The tension in the artificial membrane will cause the MS channels to gate, resulting in an increase in the conductance levels of the membrane. The results show that the MS channels are able to gate under an applied dynamic tension. Moreover, it can be concluded that the response of channel activity to mechanical stimuli is voltage-dependent and highly related to the frequency and amplitude of oscillations.

Understanding the structure-function relationships of biological materials can enable approaches in the design of functional materials for use in a variety of applications such as in sensing and electronics. Biological systems exemplify the utilization of specifically designed templates for building and tuning materials properties. The assembly of biomolecular building blocks into larger and ordered structures is highly attractive because it does not involve complicated pathways or external manipulation. Biomimetic approaches that involve the use of proteins, peptides and other biomacromolecules have been investigated by researchers to create hybrid materials. Our research activities are aimed at understanding of how biomolecules interact with abiotic surfaces, investigating structure-function relationships of biomaterials, and how they can be used in the creation of functional materials. In this talk I will describe some our recent work on understanding peptide interactions with materials as well some recent work on tuning the hierarchical organization of a biopolymer and its effect on mechanical properties.

Genetically engineered spider silk block copolymers are promising candidates to study the effect of block composition, sequence, and length on fiber formation. Spider silk block copolymers were prepared based on the assembly of two individual blocks, a hydrophobic poly-alanine rich block (A) and a hydrophilic glycine-rich block (B). The A block consisted of one polyalanine/polyglycine repeat (GAGAAAAAGGAG) responsible for β-sheet formation. The B block was composed of four GGX repeats, separated by the GSQGSGR sequence. Based on our previous work, we applied recombinant DNA technology to engineer the second generation of spider silk block copolymers H(AB)n and H(AB3)n to study the length effect on fiber formation. The constructs were cloned, expressed and purified and their secondary structures and morphologies were assessed by FTIR, SEM, and AFM. In terms of morphology, as the number of AB repeats increased, the transformation from disordered structures to nanofibrils occurred. For example, H(AB)12 block copolymer with Mw of 43.7kDa self-assembled into fibrils with an average diameter of 25 nm in aqueous media; whereas, H(AB)2 with an Mw of 11.6 kDa did not form particular morphologies. Moreover, fiber formation of H(AB)12 was induced by applying shear force in protein solution using an AFM tip. In addition the effect of solvent environment on structure formation was studied. W