We have developed synthetic methods that allow incorporation of unprecedented levels of functionality into polypeptide materials. We report on the design and properties of stimuli responsive polypeptide motifs that are able to respond differently to different individual stimuli, such as redox, temperature, or enzymes. These materials allow multimodal switching of polypeptide properties to obtain desirable features, such as coupled responses to multiple external inputs. The reversible, multiresponsive nature of these polypeptides makes them particularly attractive as components in molecular devices or nanoscale assemblies capable of sequential, or triggered, responses to different stimuli, akin to switches capable of performing Boolean-like operations. We will describe how these motifs can be incorporated into self-assembled materials such as vesicles and hydrogels.

Carefully designed peptide conjugate molecules are used to direct the synthesis and assembly of a diverse class of ‘hollow&’ spherical nanoparticle superstructures. In this talk, we describe the design of these structures, with particular emphasis on methods for controlling sphere diameter and composition. In addition, we discuss several unique emergent properties of these materials, ways in which these properties can be tuned, and how these properties enable cargo storage and release applications.

The self-assembly of suprastructures from recombinant amphiphilic proteins would allow precise control over surfactant chemistry and the facile incorporation of biological functionality. We used cryo-TEM to confirm self-assembled structures from recombinantly-produced mutants of the naturally-occurring sunflower protein, oleosin (1). Oleosin is an amphilphilic protein with two hydrophilic blocks separated by an interior hydrophobic block with a proline knot that causes the folding of the protein into the shape of a “U.” We studied the phase behavior of a subset of truncation mutants of the wild-type molecule, as a function of solution ionic strength and protein hydrophilic fraction, observing nanometric fibers, sheets, and vesicles. Vesicle membrane thickness correlated with increasing hydrophilic fraction for a fixed hydrophobic domain length. The existence of a bilayer membrane was corroborated in giant vesicles through the localized encapsulation of hydrophobic Nile red and hydrophilic calcein. Circular dichroism revealed that changes in nanostructure morphology in this family of mutants were unrelated to changes in secondary structure.
We further modified the protein in a variety of ways - removing structure from the internal hydrophobic component and adding less bulky residues to the hydrophobic core. This family of molecules are surfactants that form spherical micelles (as measured by DLS, cryo-TEM and X-ray scattering) and have a low CMC. Using recombinant methods, we have also incorporated bio-functionality into these proteins, including receptor binding peptide and affibodies, protease cleavable domains, biotinylation, and temperature dependent switches. Ultimately, we envision using recombinant techniques to introduce novel functionality into these materials toward numerous biological applications and the construction of responsive, self-assembled soft matter.
References
K. B. Vargo, R.Parthasarathy and D. A. Hammer. Proceedings of the National Academy of Sciences USA109, 11657-11662 (2012).

Collagen, the most abundant protein in mammals, plays a crucial role in tissue development and regeneration, and its structural and metabolic abnormalities are associated with debilitating genetic diseases and numerous pathologic conditions. The ability to target collagens in diseased tissue could lead to new diagnostics and therapeutics, as well as applications in regenerative medicine. In this talk, I will present a new collagen targeting strategy that is based on triple helical hybridization between denatured collagen strands (of diseased tissues) and synthetic collagen mimetic peptide (CMP). This hybridization results in robust collagen specific binding in vivo which allows detection of degraded collagens present in normal tissues undergoing fast remodeling (e.g. bones and cartilage) and those in diseased tissues with persistent wound healing activity (e.g. tumor, fibrosis). I will describe various experiments designed to elucidate the mechanism of the hybridization as well as those verifying the CMP&’s collagen binding capacity both in vitro and in vivo. This is an entirely new way to target the microenvironment of malignant tissues and could lead to new opportunity for management of numerous pathologic conditions associated with high collagen degradation and remodeling activity.

“Smart” polymers that respond to stimuli in their aqueous environments with a pronounced physical change are of great utility in biotechnology and medicine. Currently, however, only few peptide polymers show this behavior. Here, we uncover the relationship between the syntax of peptide polymers and their lower critical solution temperature (LCST) transition behavior as well as a class of peptide polymers that show the reverse -upper critical solution temperature (UCST)- behavior. I will show that the syntax of these functional peptide polymers ranges from polymers composed of simple repeats of a few amino acids to those whose syntax resembles the complex non-repetitive syntax of protein domains, and that the concept of syntax can be deployed to re-program bioactive peptides to exhibit dual functions, as seen by their stimulus responsiveness and biological activity. The unique linguistic features exhibited by these peptide polymers suggests that peptide polymers can be best described as linear macromolecules that are composed of amino acid “letters” that are organized as “words”, with higher order organization of one or more words that repeat or recur to create a “phrase” (the macromolecule) and postulate that the syntax -word order- of this class of polymers controls their function. Hence, by analogy to syntax in natural language —defined as the arrangement of words in a phrase that controls its meaning, I will introduce new concept -syntactomers- to describe polymers whose properties are controlled by their organization as a collection of letters into words and the higher order organization of words into functional phrases.

Designing protein-based biomaterials with specific functional properties is desirable for fundamental interest as well as for applied needs such as medical devices, scaffolding in regenerative medicine and drug delivery. To improve predictability of biomaterials function, multiple parameters in protein polymer design need to be considered, including sequence chemistry, molecular weight and domain distribution. Concurrent with the experimental design of such protein polymers, appropriate mathematical models are needed to predict how the engineered polymers will self-organize at different length scales with consideration for structural hierarchy to relate to material functions. The importance of multi-scale bioengineering and the combined use of modeling and experiment in advancing designs of biomaterials will be the focus of the talk. This is an emerging field where modeling can inform polymer design and vice versa. The approaches being pursued in protein-polymer design and bioengineering, polymer processing and modeling/predictions of function will be described as an example on how this iterative approach can be used to broaden predictive structure-function relationships in the field.

The use of biological scaffolds to template inorganic material offers unique strategies to synthesize precise composite nanostructures of different sizes, shapes, and compositions. Proteins are unique biological scaffolds that consist of multiple binding regions, or epitope sites, that site-specifically associate with conserved amino acid sequences within protein binding partners. These binding regions can be exploited as synthesis sites for multiple inorganic species within the same protein scaffold, resulting in bimetallic inorganic nanostructures. We demonstrate this strategy with the scaffold protein clathrin, which self-assembles into spherical cages. Specifically we design tether peptides that noncovalently associate with distinct clathrin epitope sites while initiating simultaneous synthesis of two inorganic species on the assembled clathrin protein cage. We demonstrate the versatility of this unique biotemplating strategy by synthesizing two types of composite structures, silver-gold mixed bimetallic nanoparticles and silver-gold core-shell nanostructures, from a single clathrin template. This noncovalent, Template Engineering Through Epitope Recognition, or TEThER, strategy can be readily applied to any protein assembly with known epitope sites to template a variety of bimetallic structures without the need for chemical or genetic modifications.

For decades the biological roles of nucleic acids as catalytic enzymes, intracellular regulatory molecules, and as the carriers of genetic information have been studied extensively. More recently, the sequence-specific binding properties of DNA that make it so ubiquitous among all living systems have been hijacked to direct the assembly of materials at the nanoscale. In such cases, it has become useful to consider the DNA as an artificial bond that facilitates nearly infinite tailorability in the interactions between nanomaterials via bond (i.e. oligonucleotide) length, strength, orthogonality, and even directionality. Although this powerful concept can be applied in variety of contexts including DNA tiles, origami scaffolds, and supramolecular constructs, here we explore the use of rigid inorganic nanoparticles functionalized with DNA that act to orient oligonucleotides perpendicular to their surfaces to dictate DNA bonding interactions. By elucidating a series of design rules for the nature of these DNA bonds, we show the construction of nanoparticle superlattices with over 20 different crystal symmetries with precise control over particle size and spacing. In some cases, these materials can be prepared so that they form large single crystalline domains with a well-defined crystal habit indicative of the minimum energy Wulff polyhedron of the parent superlattice. Finally, we show opportunities for dynamic and reconfigurable superlattices facilitated by the unique properties of the DNA bond.

Due to the rigid-rod characteristics of carbon nanotubes (CNT) they have been shown to aide and induce atomic and nano-scale ordering of polymer materials. In this work, this CNT trait is exploited to understand its potential along with other rigid nano-carbons to promote ordered assembly of biological materials. For the synthetic formation of collagen materials highly aligned collagen fibrils are necessary in order to replicate the native collagen structure in bone, tendon, and ligaments. This study also allows for fundamental understanding regarding collagen self-assembly. The ability to form highly aligned collagen fibrils may also lead to new fiber processing methods to enable in the development of novel applications for collagenous materials. In this work collagen fibers were self-assembled in the presence of both single-wall carbon nanotubes (SWNT) and carbon nano-chips (CNC) using a gel-spinning approach. The morphology and dispersion quality of the nano-carbons was found to play a significant role in the overall collagen fibril alignment. Small-angle X-ray Scattering (SAXS) analysis shows that low concentrations (0.5 wt%) of well-dispersed SWNT promote collagen molecular alignment leading to banding structure similar to native collagen. Fiber morphology was analyzed by both Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Beyond ordering, the nano-carbons used were also able to reinforce the collagen composite fibers. Mechanical property characterization showed a considerable increase in both strength and elastic modulus (100% and 122%, respectively), as compared to control fibers. This work is the first to show direct evidence that nano-carbon fillers may promote collagen molecular and fibril alignment during self-assembly processes.

Carbon-nanotubes (CNTs) are one of the most promising nano-materials and have been applied for various nano-electric devices, such as solar cells, batteries, and sensors, due to their superb physical properties, chemical inertness and excellent electron conductivity. One of the most basic issues in CNTs synthesis is a control of CNTs diameter and quality, since variations of CNTs cause dispersion of device characteristics. To address the issue, there have been many reports on a CNTs synthesis using catalysts of iron nanoparticles which were produced utilizing physicochemical and biological approaches.
In this presentation, we report a novel method for synthesis of diameter controlled multi-walled CNTs (MWNTs) by utilizing two-kinds of biomineralized iron nanoparticles as catalysts for chemical vapor deposition (CVD). The iron nanoparticles were 7 nm and 4.5 nm in diameter and were produced by utilizing cage-shaped proteins, ferritin and Dps, respectively. The two kinds of protein had silicon-binding peptide aptamers and could carry iron nanoparticles onto a surface of silicon substrate. Diameters of the MWNTs could be controlled in a range of 5-10 nm by the ratio of two kinds of the proteins. Structures of MWNTs were essentially maintained even at 600°C in atmospheric air. A weight loss peak of thermo-gravimetric analysis appeared at 678°C corresponds to a loss of 63 wt% which was attributable to the MWNTs themselves. We applied the thin MWNTs to electrodes of dye-sensitized solar cells (DSSCs). The MWNTs were coated with TiO₂ by biomineralizing activity of a genetically modified Dps. The TiO₂-coated MWNT improved an electric resistance of a DSSC photoelectrode. As a result, the power conversion efficiency of the DSSC with the protein-templated TiO₂-MWNT was enhanced from 5.8% to 6.6%. Moreover, the MWNTs were able to be applied for counter electrodes instead of rare metal Pt. Those results indicated that the thin MWNTs can be used as an excellent material for solar cells.

Proteins have recently attracted much attention as a building block for supramolecular structures due to their functional diversity as well as biocompatible and biodegradable properties. Several strategies for the construction of protein nanostructures including nanowires, nanotubes and nanorings have been described [1-4]. These approaches were based on the specific molecular recognition such as metal ion-protein, enzyme-inhibitor and protein-protein interaction [4]. Although various sophisticated structures of protein have been developed, the design of protein supramolecular structures is still challenging because of the structural complexity of proteins. Herein, we presented the fabrication of highly discrete protein polygons from cellular self-assembles of green fluorescent protein (GFP). The rationally designed GFP monomer is expressed in cell, and it undergoes the cellular self-assembly into polymeric forms of protein, thereby offering a highly simple and versatile way to prepare protein polymers. Furthermore, these protein polygons could be functionalized through introduction of the desired ligand into either N-terminus or C-terminus of a monomer protein using genetic manipulation. Notably, GFP polygons from dimer to decamer were individually purified, indicating that these GFP polygons can display the exact number of ligands. Finally, we showed that fabrication of discrete GFP polygons depending on the valency of functional proteins.
[1]. R. Matsunaga, S. Yanaka, S. Nagatoishi, K. Tsumoto Nat Commun. 4 (2013)
[2]. TF.Chou, C. So, BR. White, JC. Carlson, M. Sarikaya, CR. Wagner ACS Nano 2, 12 (2008)
[3]. ER. Ballster, AH. Lai, RN. Zuckermann, Y. Cheng, JD. Mougous Proc Natl Acad Sci U S A. 105, 10 (2008)
[4]. K. Oohora, A. Onoda, T. Hayashi Chem Commun., 48 (2012)

Recently, structural colored materials attract many researchers&’ attention as environmentally friendly color materials. Structural color is observed in the materials that have the microstructures comparable to the wavelength of visible light. We can obtain brightly colored materials, without any toxic dyes or pigments, by utilizing structural colored materials. There exist so many informative examples in living things for making artificial structural colored materials. In this paper, we describe the preparation of structural colored materials imitating the bird&’s feather that displays an angle-independent structural color.
Here, we have an interest in a blue bird, Steller&’s jay. This bird&’s feather contains the amorphous structure of air cavities in keratin matrix (spongy layer) above the assembly of melanin granules, and reveals an angle-independent bright blue structural color. However, an amelanotic Steller&’s jay&’s feather having the same type of spongy layer displays a white color due to the lack of melanin granules. This fact indicates that the brightly structural colored materials having amorphous structure require the existence of a black background.
Therefore, for making artificial angle-independent structural colored materials, we prepared the membranous colloidal amorphous arrays of mono-dispersed submicron-sized silica particles (SiO₂ thin films) on a black quartz glass substrate by Layer-by-Layer (LbL) deposition technique that enables us to control the film thickness of SiO₂ thin films.
For LbL deposition, we employed a cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDDA) (M_W = 400,000-500,000), and silica particles of 190 nm in diameter of which surface was negatively charged. First, a black quartz glass substrate with negative charges was dipped into PDDA aqueous solution (0.2 wt%) for 10 min, followed by rinsing with water. Then, the substrate was dipped into the silica particles aqueous suspension (10 wt%, containing NaCl 0.02 M) for 10 min, followed by washing. We defined these operations as one cycle and prepared SiO₂ thin films by varying the number of repeating times of the cycle.
Symmetrical and circular pattern around origin in two-dimensional fast-Fourier transform power spectrum of the scanning electron microscope (SEM) image on the surface of the resultant SiO₂ thin film confirmed that silica particles formed isotropic amorphous array with short-range order. From the results of the SEM observations on the SiO₂ thin films with various thicknesses, we found that the thickness was directly proportional to the number of repeating times of the cycle. Additionally, the saturation of the structural color from the SiO₂ thin films was decreased when using a clear glass plate as a substrate.
In summary, we succeeded to prepare the structural colored materials imitating the feather of the blue bird by depositing mono-dispersed submicron-sized silica particles with short-range order on a black substrate.

There is an urgent need for improved cultured intestinal models for studying oral drug delivery and intestinal disease, or to serve as a potential treatment for short bowel syndrome (SBS). Common intestinal epithelial culture models are 2-dimensional, which limit the understanding of cell behavior in their natural environment. However, native small intestinal tissue consists of multi-scale structures, such as crypts and villi, as well as extra-cellular matrix (ECM) that play an important role in aiding cellular growth and impacting cellular phenotype. To this end, we have developed a method that allows for the growth of Caco-2 in a monolayer on substrates mimicking the natural topography of the small intestinal tract. Using replica molding of PDMS, we obtained biomimetic collagen-I hydrogel substrates that showed enhanced growth of epithelial cells. This system will contribute to a better understanding of the growth of intestinal cells and eventually to efficient drug delivery in the GI for various disorders.
Porcine small intestinal tissue was washed, fixed, sectioned and placed in 0.1%OsO4 in 0.1M PBS (4 °C, 72 hours) followed by agitation to remove the epithelial cells. Samples were rinsed, dehydrated in ethanol, critically point dried (CPD) and silanized. A thin layer of PDMS (10:1 v:v) was applied on the tissue and baked for 2 hours at 60°C, and separated with via differential swelling in TEA. Positive bovine collagen-I replicas were solution cast on PDMS molds and allowed to gel at 37°C for 2-3 hours. Caco-2 cells were seeded at a density of 76,000 cells/mL and grown for 8 days. Fluorescence microscopy images were taken at day 8 to capture cell behavior on the replica and flat controls. To image the collagen gels, they were fixed, ethanol dehydrated and CPD. The dried gels were sputter coated with platinum and imaged using a Field Emission Scanning Electron Microscope (FE-SEM).
SEM images show that negative PDMS crypt-villi structures exhibit similar size features compared to native intestinal tissue, ranging from millimeter macrofolds to hundreds of micron villus protrusions. The CPD collagen gels have similar micro-scale size features compared to the native intestinal tissue, but there was a loss in height of villus-like structures due to dehydration and heat processing of the hydrogels for SEM. The hydrogels provided environmental and topographical cues, allowing seeded cells to proliferate and mature. Fluorescence microscopy images show that Caco-2 grown on the porous collagen replicas formed monolayers and exhibit a 3.8-fold increase in proliferation compared to flat controls that remained subconfluent after 8 days in culture. Ongoing studies involve characterizing the hydrogel surface topography to understand and quantify Caco-2 and primary intestinal stem cell behavior on these biomimetic materials. This model will serve as stepping-stone to enhance drug delivery as well as play a crucial role in regenerative medicine.

Luminescent europium (Eu) and dysprosium (Dy) doped Yttrium-Vanadate (Y-V) nanoparticles (NPs) were synthesized in a cavity of the protein, apoferritin. The use of inorganic nanoparticles (NPs), instead of organic dyes, is becoming popular for molecular labeling because of their strong resistance to photobleaching. Since structure of protein is strictly regulated by DNA, the size of NPs in the protein also becomes homogeneous. Moreover, apoferritin is thermally stable water soluble protein, and thus encapsulated NPs are also stably dispersed in aqueous solution. The sequence of a protein can be modified by protein engineering to enable the protein to bind to a specific molecule, e.g. an aptamer, these NPs are likely to be biocompatible and would have significant potential for biological imaging applications.
Y-V NPs were synthesized by incubating a solution of apoferritin with Y³⁺ and VO₃^- ions in the presence of ethylene diamine-N-N'-diacetic acid (EDDA). EDDA plays an important role in preventing Y-vanadate precipitation in bulk solution by chelating the Y³⁺ ions. Using high resolution electron microscopy, the obtained NPs in the apoferritin cavities were confirmed to be amorphous, and to consist of Y and V. The average size of the obtained NPs was 6.6 ± 0.7 nm.
Eu-doped Y-V (Y-V:Eu) NPs were synthesized by the same procedure as Y-V NPs, except that Eu(NO₃)₃ was added. Y-V:Eu NPs exhibited a strong absorption peak due to the O-V charge transfer transition and remarkable luminescence at 618 nm due to the ⁵D₀ - ⁷F₂ transition. Luminescence showed maximum intensity at Eu doping ratio of 11.4%. Strong red luminescence was easily observed by eye, even in a brightly lit room.
It is known that O-H vibrations play a dominant role in the non-radiative transition from excited Eu³⁺ ions and that transition is greatly reduced by substituting hydrogen (H) to deuterium (D). To investigate the non-radiative transition pathway of Y:Eu and Y-V:Eu NPs, the luminescence lifetime of these NPs in water (H₂O) and heavy water (D₂O) were compared. The lifetime difference in H₂O solution and D₂O solution is six times larger in Y:Eu than Y-V:Eu NPs at low Eu concentration. This means non-radiative transition due to the O-H vibration is smaller in Y-V:Eu NPs. Accordingly, Y-V NPs showed strong luminescence compared to Y:Eu NPs which we reported previously [1]. Dy-doped Y-V (Y-V:Dy) NPs were also synthesized in apoferritin cavities and showed luminescence peaks at 482 nm and 572 nm, corresponding to ⁴F_9/2 - ⁶H_15/2 and ⁴F_9/2 - ⁶H_13/2 transitions. Luminescence showed maximum intensity at Dy doping ratio of 3.5%. This solution had a yellow color under UV irradiation.
[1] T. Harada and H. Yoshimura, J. Appl. Phys, 114, 044309 (2013).

There is a constant need for economical and portable point-of-care biodiagnoistic devices. Numerous colorimetric sensors are based on the aggregation of plasmonic nanoparticles; however, colloidal solutions present limitations on the portability of the sensor. We present a new sensing platform in which the colorimetric signal comes from changes in the morphology of substrate-bound nanoparticles. The sensing platform consists of immobilized gold-coated silver nanoparticles on a glass substrate, on top of which a stimulus-responsive polyelectrolyte-aptamer film is assembled. Binding of the target to the aptamer leads to the swelling of the polyelectrolyte layer as conferred by ellipsometry, and results in an increase in the diffusion rate of etchant molecules. The etchant changes the size and shape of the nanoparticles and therefore the colour or intensity of the film. We achieve a discernible colorimetric difference between the control film and the target bound film, and investigate the concentration dependence and effects of interference species. Characterization techniques such as ellipsometry and cyclic voltammetry will help to advance the understanding of the mechanisms involved. Further development of this platform may provide facile field analysis by using consumer electronics in addition to presenting new opportunities for aptamer-based sensing.

Although it is known that specific biochemical cues in tissue extracellular matrices (ECM) play a critical role in regulating cellular growth processes and their fate, the role of physical cues of them such as stiffness in guiding the fate of resident stem cells has not been well studied so far. In this study, we have demonstrated engineered phage mediated matrix controlling stiffness for various applications over conventional tissue engineering materials by exploiting its physical and biological structural features (such as the phage&’s self-assembling, selfreplicating and evolving nature). We modified M13 phages to express biotin-like peptides (HPQ) and/or integrin binding peptides (RGD) on their major and minor coat proteins. The stiffness of matrix was controlled by cross-linking the engineered phage with different concentarions and compositions of streptavidin and polymer mixture. Then, we verified that osteogenic differentiation could be controlled according to the rates of stiffness of the constructed phage matrix. Osteogenic gene expressions through mRNA expression quantification and protein activity assays showed that they were specifically increased when bone stem cells were cultured on the M13 matrix with adequate stiffness. Our phage matrices, which can be easily functionalized with various ligands and growth factors to enhance the stiffness modulation using other chemicals, may be used as a convenient tissue matrice platforms for controlling stem cell expansion and differentiation. [This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2013R1A1A3008484)]

Melanins are a class of pigments with unique physicochemical properties including redox activity, hybrid ionic conductivity, and efficient photon-phonon conversion. Natural eumelanins and synthetic analogs, termed “polydopamine”, have garnered interest in applications including clean energy, functional interfaces, and biomedicine. However, the structural distinctions between natural and synthetic melanins remain elusive. Parsing out these structural deviations is essential in advancing the use of these materials. Here we present a study in which bioinspired surface chemistries are modulated to elucidate the adsorption and deposition of polydopamine precursors.
We have investigated the effect of fundamentally simple differences in surface chemistries on the growth of polydopamine films. Silicon dioxide and self-assembled monolayers of amino, aromatic, or aliphatic moietes produce melanin films with comparable thickness (ca. 10nm) and morphology of adherent islands. Electrostatically neutral aromatic and aliphatic surfaces produce smoother polydopamine films (R_RMS= 0.3-0.7nm) compared to anionic oxide and cationic amine-terminated surface chemistries (R_RMS= 1.1-1.6nm). Additionally, catechol dissociation at higher pH prevents film formation on the oxide and reduces the average roughness of the amine-terminated surface to a value similar to the aromatic and aliphatic (R_RMS= 1.2nm at pH 8 vs. 0.5nm at pH 10). This suggests multiple modes of adsorption that provide polydopamine with its versatile coating capability. These findings are supported by quartz crystal microbalance studies.
These findings have also been extended to understand the nucleation and growth of melanins on Pmel17 template proteins on two-dimensional surfaces. Taken together, these data suggest that two-dimensional SAMs monolayers are an accurate model to replicate aspects of natural melanin synthesis. These findings will aid in elucidating the fundamental mechanisms of in vivo melanogenesis

Water-responsive materials swell and shrink in response to changes in relative humidity (RH) and can be potentially used to harvest energy from evaporating water [1]. Here, we investigated the potential of harvesting energy from naturally evaporating water due to typical weather conditions across the United States. We modeled the power output, the effect on evaporation rate, and the intermittency of the power output. We first performed steady state calculations over a range of 218 locations across the United States and determined the average energy flux and net water savings due to a reduction in evaporation rates. We then used a non-steady state mass and energy balance approach on three test locations of South-East NY, Western TX, and South-East CA to determine daily and yearly variations in power output. Our calculations show that this system can deliver power densities surpassing wind power and comparable to current installed solar systems. These results suggest that further research into water-responsive materials and devices can provide major benefits in developing a novel renewable energy platform.
References:
1. X. Chen, L. Mahadevan, A. Driks, and O. Sahin. Bacillus spores as building blocks for stimuli-responsive materials and nanogenerators. Nature Nanotechnology, 2014. 9(2): p. 137-141.

Metal nanostructures with highly branched morphologies are an interesting and useful new class of nanomaterials due to their plasmonically enhanced optical properties, large surface area and potential as catalytic substrates. In particular, surface plasmon-derived photo-induced therapeutic effect and catalysis are highly dependent on their surface nanostructures, but the control of their branching structures is challenging. Here, we introduce a strategy for the controlled synthesis of plasmonic core-petal nanostructures (CPNs) with highly branched morphologies. The fine nanostructural engineering of CPNs was facilitated by oxidative disassembly of organic biopolymer-corona around spherical Au nanoparticles and successive anisotropic growth of Au nanopetals. We show that CPNs can act as multifunctional nanoreactors that induce protrusion-dependent controllable photodynamic and photothermal dual therapeutic effects as well as ROS generation. NIR laser-activated CPNs can be used to induce the effective destruction of cancer cells via the synergistic combination of benign plasmonic hyperthermia (~42 °C) and ROS-mediated oxidative intracellular damage. It was also shown that CPNs exhibit very strong surface-enhanced Raman scattering (SERS) signals, and this allows for post-mortem probing of ROS-mediated oxidative structural modifications of DNA that could be responsible for the apoptotic fate of cancer cells. Here, we have showcased the well-tunable synergistic plasmon-based catalytic and thermoplasmonic properties of NIR active branched nanostructures for organic photosensitizer-free bimodal photodynamic-photothermal therapeutic ablation of cancer cells. Synthesis of such biocompatible, non-invasive and aesthetic but highly effective nanotherapeutic platforms have great potential for future clinical applications.

Understanding the role of endogenous or exogenous reactive oxygen species (ROS) and reactive nitrogen species (RNS) at molecular, cellular, and organismal level in a range of physiological processes as well as in the pathogenesis of many diseases, is an emerging area of research in redox chemical biology. ROS and RNS often exhibit interdependent production and roles in the complex signal transduction and oxidative pathways; and sometimes direct the activation of distinct signaling mechanisms determining cell fate. Simultaneous and distinguishable monitoring of ROS and RNS is crucial to understanding their biochemistry and effects on signal transduction pathways. Surface-enhanced Raman scattering (SERS)-based biosensing probes have advantages such as highly sensitive molecular finger-printing, multiplexing and non-invasiveness for in-vitro and in-vivo applications. Here, we designed a ‘core-satellite&’ plasmonic nano-assembly with a sub-nanometer thick insulating molecular spacer between core and satellites for functionalization of heme protein. Intense SERS signals corresponding to characteristic Raman bands of Fe-porphyrin reporter moieties located in ‘hot-spot&’ junctions could be obtained due to extensive plasmonic coupling among core and satellite AuNPs. Our SERS probe was found to be highly sensitive towards exposure of ROS and RNS as distinct Raman signals were produced in both the cases. Biological experiments revealed facile internalization of core-shell bioprobes in the living cells and excellent biocompatibility. Finally, we were able to quantitatively and distinctly monitor ROS and RNS in normal and cancer cells using our SERS bioprobes. This method enables sophisticated hot plasmonic assemblies to be used for unraveling the etiology and pathophysiology of many diseases involving alterations of oxidative and nitrosative stress, such as cancer, neurological disorders, pancreatic malfunction, and inflammatory diseases.

Regeneration of complex orthopedic tissues (such as ligaments, bones, and the tendon-to-bone insertion site) is problematic due to a lack of suitable biomaterials with the appropriate chemical and mechanical properties to elicit the formation of tissues with similar structure, organization, and functionality to natural tissues. Additionally, a non-trivial fraction of implanted biomaterials become infected by bacteria, which can lead to implant failure, secondary surgeries, and the spread of infection to other tissues throughout the body. To address these issues, the current study investigated magnesium oxide (MgO) nanoparticles as novel materials to improve orthopedic tissue regeneration and reduce bacterial infection.
Here, MgO nanoparticles and hydroxyapatite (HA) nanoparticles were dispersed within poly (l-lactic acid) (PLLA) composites and then tested for their mechanical properties, surface roughness, antibacterial properties, and their ability to support the adhesion and proliferation of fibroblasts and osteoblasts. Free nanoparticles (MgO and HA) in solution were also exposed to cells and bacteria to characterize the nature of the cellular responses to these materials.
Results showed that MgO nanoparticles in solution enhanced fibroblast and osteoblast proliferation, suggesting that magnesium plays an important role in improving cell functions. When dispersed within PLLA composites, MgO nanoparticles improved osteoblast and fibroblast adhesion and proliferation compared to plain PLLA. Osteoblasts proliferated best on nanocomposites containing both HA and MgO nanoparticles, as MgO nanoparticles were believed to enhance the osteogenic properties of HA nanoparticles. Nanocomposites containing both HA and MgO nanoparticles also exhibited the most suitable mechanical properties for application within cancellous bone. Bacterial experiments with Staphylococcus aureus showed that MgO nanoparticles exhibit powerful bactericidal efficacy, suggesting that MgO nanoparticles should be incorporated into scaffolds for orthopedic tissue engineering to improve cell functions and reduce the risk of bacterial infection.

Organic-inorganic composite particles have attracted much interest due to applications in photonics, electronics and biotechnologies. Especially the applications in biotechnologies, such as contrast agents in magnetic resonance imaging (MRI), drug carriers, heat generators for hyperthermia therapy and so on, are considered to be important in recent years. Organic-inorganic composite particles usually have been prepared by attaching inorganic NPs on polymer particles via electrostatic interaction named heterocoagulation. But since the electrostatic interaction is sensitive for environment of dispersion, the inorganic NPs easily detach from polymer particles at in vivo condition. Therefore preparation of polymer particle platforms for anchoring inorganic NPs stably even in vivo conditions is required.
To prepare that kind of polymer platforms, a catechol group is one of the good candidates. The catechol group is found in the adhesive protein of mussels and high adhesive properties of catechol groups onto many kinds of substrates have been reported. We have reported a synthesis of amphiphilic copolymer containing the catechol group and a simple preparation method of polymer particles by evaporating a good solvent from a polymer solution containing a poor solvent(SORP).
In this report, we show preparation of polymer particles containing catechol groups by using SORP. We found that these particles are successfully anchoring inorganic NPs stably under high salt concentration conditions.
The amphiphilic copolymer containing a catechol group was synthesized from dopamine methacrylamide and N-dodecylacrylamide by free radical polymerization(Polymer 1). Polymer 1 and polystyrene(PS) were respectively dissolved in tetrahydrofuran (THF) to prepare 1 g L^-1 solution. A solution of Polymer 1 (0.5 mL) and that of PS (0.5 mL) were mixed, and then MilliQ membrane filtered water (1 mL) was added to the mixed solution with stirring. THF was evaporated at 25 °C in a water bath. Polymer particles of hydroxy terminated PS (PSOH) were prepared by the same method. Aqueous dispersion of Au NPs was mixed with aqueous dispersion of polymer particles, and then the mixtures were kept at 25 #8451; in a water bath. An aqueous solution of potassium chloride(2M) was added into the mixtures. The mixtures were dialyzed over night and observed by scanning electron microscopy (SEM).
SEM images showed that the AuNPs were attached homogeneously to the surface of the polymer particles containing catechol groups. On the other hand, the aggregated AuNPs were observed on the surface of the PSOH particles and on the grid. These results indicate that catechol groups were localized at the surface of polymer particles and contributed to immobilization of inorganic NPs. We succeeded in preparing polymer particles comprised of PS and amphiphilic copolymers containing catechol groups, and they succeeded in anchoring inorganic NPs stably under high salt concentration conditions.

Colloidal semiconductor nanocrystals, such as quantum dots (QDs), have fascinating physical properties of relevance to biology include high fluorescence quantum yield, narrow and symmetric photoluminescence spectra, broad absorption profiles, remarkable chemical, photonic, and colloidal stability, large effective Stokes shift, and high multiphoton excitation cross sections. The successful conjugation of quantum dots with biological molecules, such as proteins and DNA, is a critical step for their utility as fluorescent bio-probes, engineered biosensors, photodynamic therapy agents or sensitizers, and bio-inspired functional materials for light harvesting. Over the past 15 years, there have been continuous efforts to develop new QD-protein conjugation methods. Among them, carbodiimide crosslinker chemistry, such as 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) /N-Hydroxysuccinimide (NHS), is often used to attach QDs with proteins, typically by amide bond formation between terminal carboxyls on the QD ligands and ubiquitous amines on proteins. However, the presence of the same ubiquitous target groups on target proteins means that this approach can often result in uncontrolled heterogeneous orientation and valence on the QD and undesirable cross-linking. Furthermore, QD conjugates formed with this chemistry require multi-step synthesis and purification, which results in low conjugation efficiency, reduced fluorescence quantum yield, and less colloidal stability. Herein, we developed a new strategy to achieve robust QD-protein conjugates with a single-step synthesis in a short time. Our strategy takes advantage of a two-cysteine/six-HisTag linkage, that are genetically encoded with the SpyCatcher protein expressed by Escherichia coli, and could be directly attached to the QD shell surface during the core/shell QD synthesis in aqueous solution. This synthetic route results in robust core/shell QD-protein conjugates that are highly stable, highly fluorescent, and versatile for a wide range of semiconductor materials with various sizes, compositions and morphologies. We further demonstrated the organization of micron-scale one-dimensional QD chain structures and related heterosystems by specific SpyCatcher-SpyTag chemistry, which is high yield, highly specific and compatible with diverse pH, temperature, and buffer in vitro and in vivo environments. Since the reactive units are conveniently introduced by genetic engineering in either prokaryotic or eukaryotic expression systems, we recognized that the SpyTag-SpyCatcher chemistry is an excellent platform for QD-proteins conjugates with tunable fluorescence properties, and could be used an ideal platform for bacterial cell directed self-assembly of functional devices in large-area. While the present work applies to QD-SpyCatcher, we expect the general applicability of our approach to other materials and recombinant proteins for scalable assembly of multiplexed functional devices.

Metal-coordinate bonds inspired by the tough, ductile mussel fiber have recently been demonstrated to act as the reversible crosslinks in self-adhesive polymer hydrogels. The exchange kinetics of these crosslinks can be tuned across several orders of magnitude simply by using different transition metals as the crosslink center. Thus, with the exact same polymer, we are able to engineer materials with vastly different viscoelastic relaxation times.
We show that the individual relaxation times are modular - we can insert and remove viscoelastic relaxation modes by simply changing the relative concentrations of different transition metals in our gels. Traditionally, the polymer architecture and viscoelastic properties are interdependent, but the modularity of metal-coordination complexes allows us to effectively de-couple the polymer structure from the mechanical behavior of the system, as we can modulate the mechanical properties orthogonally from the polymer backbone. Using bio-inspired metal-coordinate complexes in this manner will allow the creation of model viscoelastic systems to explore fundamental questions in soft materials design, such as how incorporating well-controlled reversible interactions into covalent gel networks can be used to control stiffness, toughness, and ductility in hydrogel systems.

A simple, nontoxic and inexpensive method to prepare mechanically robust surfaces that repels a variety of liquids and solids has immediate relevance in many industrial applications. Unwanted interactions between liquids and surfaces are currently a limiting factor nearly everywhere liquids are handled or encountered. Most state-of-the-art liquid repellent surfaces are modeled after lotus leaves, which are known to exhibit superhydrophobicity and self-cleaning. Despite over a decade of research, these surfaces are still plagued with problems that restrict their practical applications.
Recently, the slippery liquid-infused porous surfaces (SLIPS) technology was introduced by our group. SLIPS technology is inspired by the Nepenthes pitcher plant and provides unique capabilities that are unmatched by any other liquid-repellent surface technologies. SLIPS surfaces function under high pressure conditions, instantly self-heal imperfections, provide optical transparency, repel ice nucleation, and are ultra-repellent to pure and complex fluids such as blood, crude oil, and brine. They also repel solids such as ice and wax. These properties allow the slippery surfaces to be used in a wide variety of applications and environments. Moreover, the slippery surfaces can be constructed from a broad range of simple, inexpensive materials without the need for specialized fabrication facilities.
Here we used a stainless steel, which is widely used in biomedical, household and industrial equipment, surgical instruments, kitchen appliances, transport and architecture, as a substrate. We use an inexpensive and environmentally friendly electrodeposition process to form a thin layer of nanostructured tungsten bronze. Such films are mechanically robust and can be functionalized to increase its hydrophobicity, ideal for integration with SLIPS technology. Moreover, electrochemical deposition provides various control parameters for optimization of the film morphology. We will present that slippery stainless steel surfaces can be optimized to repel simple and complex fluids, reduces ice formation, accelerates frost removal and prevent adhesion of biofilms.

Biopolymer based nanocomposites are great of interest for use as bone scaffolds due to their biocompatibility and adjustable mechanical and biodegradation properties. Mechanical properties of human bone vary tremendously according to location and function (i.e., load or non-load bearing). Therefore, a scaffold's mechanical properties should be tailored to match the demands of the defect site, and to decrease or avoid complications such as stress-shielding. Scaffold properties can be tailored to the particular mechanical and physiologic demands of the host tissue by effectively controlling weight fraction, ratio of the constituents, and morphology.
Current research is focused on investigation of the effects of content parameters of recently developed nanocomposites on mechanical behavior of them were investigated by using factorial design methodology. The poly(L-lactic acid)/microcrystalline cellulose/hydroxyapatite nanoparticles nanocomposites were fabricated using sublimation of polymer solvent and leaching out the porogen out of nanocomposite structure followed by characterization using scanning electron microscopy (SEM), universal compression testing machine. Statistical analysis evaluated the effects of three independent variables on final properties of the nanocomposite. Increasing the concentration of PLLA affected mechanical properties including compressive yield and Young&’s modulus positively. Besides, the higher ratio of MCC/HA ratio (0-4) led to enhancement of compressive yield from 0.32 to 0.87 MPa and Young's modulus from 16.11 to 28.55 MPa. Furthermore, the effect of concentration of PLLA on final compressive properties has been evaluated. Based on optimization with factorial design methodology, by varying the comcentration of PLLA from 10% to 20 %, compressive yield improved from 0.87 to 1.36 MPA, and Young's modulus from 28.55 to 44.64 MPa. The same investigation has been conducted for nanocomposites with the presence of porogen. The comparissive study of nanocomposites with porogen and without porogen revealed that incorporation of porogen during the fabrication of the nanocomposite resulted lower compressive yield in compare with the ones with no porogen. However, SEM images showed that the pore shapes uniformity and interconnectivity were improved. The mechanisms involved for the failour during the compression test also have been discussed.

Natural enzymes have been evolved as impressive catalysts for taking a long time. Although they have effective functions in many chemical reactions, it is difficult for researchers to optimize the functions and improve the yield of products because of the complexity and lack of fully understanding of the catalytic mechanism. In our study, to discover efficient peptide biocatalysts and evolve the catalytic functions, (i) we constructed a novel screening methodology that enables the selection of catalytic peptides from sequence libraries based on the phage display technique and (ii) we fused hydrophobic tail of amyloid β mimicking peptide (ABP)¹⁾ at the C-terminus of catalytic peptide which can provide hydrophobic part as well as self-assembling property to accumulate catalytic center. This approach using libraries of M13 phage viruses consists of 10⁹ different phages, each displaying five copies of peptide sequence at the tip. The peptide catalysts in chemical reaction were selected via supramolecular gelation²⁾ of targeted products on phage viruses for the mass-separated panning process. In this methodology, when a phage library is exposed to precursors in aqueous solution, the product is gelated by the activity of catalytic peptide on phages. Based on catalytic gelation combined with phage display we selected several catalytic peptides which can catalyze to bond between two molecules by amide condensation.
To confirm the generated compound by amide condensation occurred in selected peptide display region of phages, transmission electron microscopy (TEM) was carried out. The TEM images showed that the hydrogel was observed in reaction sample including selected catalytic peptide, while no such hydrogel was observed in control sample which is absence of the peptide. We also confirmed the product in the reaction sample by HPLC. In the sequences of the selected peptides, we found some of peptides contain nucleophilic amino acids and also the most common catalytic triads (histidine, serine and aspartic acid or glutamic acid). They might have not only amide condensation activity but also amide hydrolase activity because these catalytic triads are found in a range of amidases. Natural enzymes have hydrophobic pocket to capture substrates in order to enhance catalytic selectivity and activity. By addition of ABP to catalytic peptide, the catalytic activity was increased rather than without ABP peptide. The result showed that the assembly of catalytic peptides is important for evolution of catalytic function.
The discovery of these peptides for mimicking protease has significantly impact because the peptide consisting of the only 12 amino acids is useful and can be designed easier for synthesis of chemical compound such as drug molecules.
1) M. J. Krysmann, V. Castelletto, I. W. Hamley, Soft Matter, (2007), 3, 1401-1406.
2) R. J. Williams, A. M. Smith, R. Collins, N. Hodson, A.K. Das, R. V. Ulijn, Nat Nanotechnol., (2009), 4, 19-24.

A polypeptide-based hydrogel fills the nuclear pore channels embedded in the nuclear membrane of a eukaryotic cell and acts as a selective gate allowing passage of less than 0.1% of all proteins in the cell while translocating over 1,000 molecules per second. The gel-forming proteins are nucleoporins, containing “FG” repeat sequences which are known to associate with one another to construct physical gels and give rise to the hydrogel&’s selective filtering property. This biologically specific selectivity of nucleoporin hydrogels, which is unprecedented in synthetic polymer gels, makes them scientifically interesting materials with a potential for broad impacts on separation technologies. However, major obstacles in utilizing nucleoporin hydrogels for advanced technology include low biosynthetic yield of the natural protein; long gel processing time, delaying immediate use; and incomplete knowledge of sequence-structure property-function relationships of the nucleoporin hydrogel due to the complexity of natural protein sequences, hindering creating tunable selective filters.
Herein, we report for the first time artificially engineered protein hydrogels that mimic the selective permeability of nucleoporin hydrogels, are produced in high yields, and possess reduced gelation times. Analysis of a well-investigated nucleoporin, Nsp1, yielded a pair of consensus sequences for a 19 amino acid nucleoporin repeat which is repeated 16 times in the native protein with extremely high consensus at each position except one. This fundamental repeat unit was cloned into an artificial protein polymer by ligating 16 such units in a row to produce a nucleoporin-like protein (NLP). To facilitate hydrogel formation, NLP sequences were flanked with coiled-coil domains as endblocks of NLPs, creating three dimensional polymer networks.
Simplified NLP sequences allowed investigation of the sequence-structure property-function relationships of nucleoporin hydrogels. Using a combination of techniques including the hydrogel inversion test, selective transport assay, shear rheology, and Raman spectroscopy, we found that only recombinant NLPs with coiled-coil endblocks constructed hydrogels with different levels of selective permeability. A pair of NLPs with a single amino acid replacement within the repeat unit presented significantly different amounts of cargo transportation into the hydrogels and hydrogel relaxation times, suggesting that physicochemical properties of NLP sequences are correlated with the selective permeability and mechanical properties of the hydrogels. Moreover, our findings revealed that not only “FG” sequences but also other sequences of natural nucleoporins would be important for gel structure and the selective filtering function. Tunable mechanical properties and selective permeability of nucleoporin-mimicking hydrogels with high yields can potentially advance the technology in drug delivery, food toxicology, and defense applications.

Wide spread bacteria contamination has been found on various paper products, such as paper towels hanging in sink splash zones or those used to clean surfaces, filter papers used in water and air purifying systems, and wrapping used in the food industry, which may lead to the potential spread of bacteria and consequent health concerns. Due to the porous structure of fibers in all paper products, such materials are prone to bacteria growth and, thus, are sources for continual contamination. Besides, this porous structure provides an environment that favors the attachment of bacteria and makes it more difficult to kill bacteria once forming a biofilm. One of the most promising approaches towards preventing infections is coating paper products with antimicrobial materials. Therefore, in this study, selenium nanoparticles were coated on normal paper towel surfaces through a quick precipitation method, introducing antibacterial properties to the paper towels. Their effectiveness at preventing biofilm formation was tested in bacterial assays involving Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus epidermidis. The results showed that there were significant and continuous bacteria inhibition with about a 90% reduction from 24 to 72 hours for gram-positive bacteria including S. aureus and S. epidermidis. The selenium coated paper towels also showed significant inhibition of gram-negative bacteria like P. aeruginosa and E. coli growth at about 57% and 84%, respectively, after 72 hours of treatment. Therefore, this study suggested that coating paper products with selenium nanoparticles may be an effective way to decrease various gram-positive and gram-negative bacteria growth on paper products, which might be used for potentially important applications for antimicrobial purposes in the food packaging industry and in clinical environments.

3,4-Dihydroxyphenylalanine (Dopa), which is a hydroxylated form of the tyrosine residue, has been suggested to be a key factor for rapid and strong underwater adhesion through its mediation of various interactions, such as bidentate hydrogen bonding, complexes with metals and metal oxides, the cation-pi interaction, and oxidative cross-linking, because it is oxidised to Dopa-quinone. Mussel adhesive proteins (MAPs) are one of examples where Dopa chemistry is the core of their underwater adhesion with extremely high Dopa contents of ~10-25 mol%. The biosynthesis of recombinant MAPs in an Escherichia coli system was a good approach to overcome the availability limitation that results from the extremely low yield of natural extraction of MAPs from mussel feet and to apply MAPs as an universal underwater bioadhesive. However, Dopa incorporation always follows as the biggest problem because lack of Dopa in recombinant MAPs critically limited the underwater adhesion. To transform tyrosine residues into Dopa molecules, an in vitro mushroom tyrosinase treatment has commonly been conducted. However, this process exhibits a low (<~15%) modification yield. Here, we explore the in vivo residue-specific incorporation of Dopa into recombinant MAPs. Because Dopa molecules can be misaminoacylated to tRNA^Tyr by endogenous tyrosyl-tRNA synthetase, the quantitative replacement of tyrosine residues by Dopa was achieved with a yield of over ~90 % via an in vivo residue-specific incorporation strategy, to create, for the first time, engineered mussel adhesive proteins (MAPs) in E. coli with a very high Dopa content close to that of natural MAPs. Using several analyses, we confirmed that Dopa-incorporated engineered recombinant MAPs exhibited the superior surface adhesion and water-resistance abilities by assistance of Dopa-mediated interactions including oxidative Dopa cross-linking. In addition, their underwater adhesive properties were comparable to those of natural MAPs. Our results show their great potential as bioglues for use in practical underwater applications.

Aquatic species in the Phylum Cnidaria, including sea anemone and jellyfish, have special cell organelle called nematocyst. When stimulated, with waving motion of tentacles, coiled tubular structure in charged nematocyst is instantaneously stretches out to capture prey or keep the organism itself from predators. The driving force of this ultra-speedy discharge is high osmotic pressure maintained in charged nematocyst. Therefore, the capsule wall of nematocyst should be tough enough to withstand this internal pressure. Previous researches have shown that minicollagen is a main component of capsule wall, so it can be thought as critical structural material to meet mechanical requirement. However, almost every research treating minicollagen and its experimental analysis has used Hydra as a source organism. In the present work, estuarine sea anemone Nematostella vectensis was chosen as a novel target organism for minicollagen research. Structural analysis found disulfide crosslinking and triple helix formation among minicollagens, which are regarded as main reason of superior mechanical toughness. Measuring mechanical properties of nematocyst capsule wall were also tried to know how exactly strong the wall is. Forming a part applying this nature-inspired structure and power in engineering, recombinant production of sea anemone minicollagen in Escherichia coli expression system was successfully endeavored. Genetically redesigned E. coli for disulfide bond formation and in vivo incorporation of 4-hydroxyproline was used to mimic natural structure of minicollagen. These approaches cannot only help researchers to acquire homogenous minicollagen for basic analysis, but also suggest its possibility as a plentiful biomaterial in engineering.

Gel-based scaffolds have been utilized as space filling agents, delivery vehicles, and three dimensional structures. However, their weak strength and stiffness (elastic modulus) were considered as limitations to endure physiological stimulus. Here, we exploited recombinant silk-like protein (aneroin), originally derived from sea anemone&’s tentacle, as tough gel material. Aneroin consists of decamer repeats and has similar secondary structure of an elastic silk from spider (flagelliform silk). Photo-initiated crosslinking was tried for hydrogel formation. Additionally, disulfide crosslink was also carried out to enhance mechanical property of gel. We found that elastic modulus of aneroin was three times higher than skeletal muscle, and its strength was two-fold stronger than cardiac muscle. In addition to mechanical properties, photo-crosslinked aneroin showed high transmittance in visible light. Thus, durable and transparent aneroin hydrogel would be expanded its applications to biomolecular carrier as well as structural support.

Piezoelectric materials can convert mechanical energy into electrical energy, and piezoelectric devices made of various inorganic materials and organic polymers have been demonstrated. However, synthesizing such materials often requires toxic materials, harsh conditions and/or complex procedures. Recently, it was shown that hierarchically organized natural materials, such as bones, collagen fibrils and peptide nanotubes, can display piezoelectric properties. In my presentation, I will show our innovative approach to produce virus-based piezoelectric energy generation. Recently, we establish that the piezoelectric and liquid crystalline properties of M13 bacteriophage (phage) can be used to generate electrical energy. Using piezoresponse force microscopy, we characterize the structure-dependent piezoelectric properties of phage at the molecular level. We then show that self-assembled thin films of phage can exhibit piezoelectric strengths of up to 7.8 pm/V. We also demonstrate that it is possible to modulate the dipole strength of phage, and hence tune their piezoelectric response by genetically engineering the phage&’s major coat proteins. Finally, we develop a phage-based piezoelectric generator that produces up to 6 nA of current and 400 mV of potential, and use it to operate a liquid crystal display. Because biotechnology techniques enable large-scale production of genetically modified phages, phage-based piezoelectric materials potentially offer a simple and environment-friendly approach to piezoelectricity generation.

Multidomain peptides (MDP) self-assemble into extracellular matrix mimetic nanofibrous hydrogels. These short chain biocompatible matrices, exhibit shear thinning and rapid recovery, allowing for syringe aspiration and directed in situ delivery. Tailoring of terminal residues allows for fined tuned control of molecular, cellular and tissue responses. In this study, we show the development of a hybrid MDP capable of stimulating robust angiogenic responses. A short chain (15 amino acid) peptide sequenced from VEGF 165 was conjugated to a 16 amino acid MDP. Mechanical and ultrastructural characterization showed presence of nanofibrous structure, shear thinning and recovery. Biological function was demonstrated by upregulation of VEGFR1, VEGFR2 and NP-1 activation. Cytocompatibility with HUVEC and hMSCs showed similar cell adhesion, proliferation and scratch wound healing to positive controls. Gross morphology of subcutaneous implants of injectable hydrogels showed large vessels in and around implants, without the development of hemangiomas or leaky vasculature. Histomorphometric analysis showed rapid cellular infiltration as early as 3 days, rapid development of stable blood vessels as early as 7 days suggesting formation of mature blood vessels. These vessels subsequently resorb by 3 weeks. Materials developed in this study may allow for rapid angiogenesis, increased ischemic tissue perfusion, and augmented tissue regeneration.

Despite the widespread utilization of bio-titania interfaces,¹ such as in biomedical implants, drug delivery, biosensors and photovoltaics, biomolecular recognition and interactions at these interfaces remain far from being understood. Predicting and controlling bio-interfacial properties is extremely challenging without a molecular-level comprehension of how biomolecules interact with material surfaces and the factors that influence these interactions. Molecular simulation, using efficient conformational sampling of peptide adsorption to material surfaces is one way of elucidating these mechanisms. Employing advanced sampling techniques is therefore crucial to the understanding, advancement, and optimization of interfacial properties. We utilize cutting-edge techniques such as Replica Exchange with Solute Tempering (REST)² and Metadynamics³ to study, at the negatively-charged aqueous rutile TiO₂ (110) surface, the adsorption of a number of amino acids and titania-binding peptides and calculate their binding free energies.
This is performed by studying analogues of six amino acids (Ala, Arg, Asp, Lys, Phe, and Ser) and two experimentally-identified titania-binding peptides, namely Ti1 (QPYLFATDSLIK) and Ti2 (GHTHYHAVRTQT).⁴ Our results revealed a stronger affinity between charged amino acids and the titania surface compared to uncharged amino acids. In addition, peptides Ti1 and Ti2 were found to have a similar free energy of adsorption but different binding mechanisms. While Ti2 revealed an enthalpic binding, Ti1 showed an entropically-driven binding mechanism.⁵ The contribution of each residue to binding to the titania surface was evaluated in both peptides. Moreover, the effect of using Ca²⁺ counterions, in contrast to Na⁺, on the adsorption of both peptides at aqueous titania was studied. Finally, the impact of His protonation state on the adsorption of Ti2 was evaluated. Our results provide valuable insights into the complex interplay between peptide sequence, structure, and binding at the aqueous TiO₂ interface.
References
¹ Carravetta V and Monti S. Peptide-TiO₂ surface interaction in solution by ab initio and molecular dynamics simulations. J. Phys. Chem. C (2006) 110, 6160-6169.
² Terakawa T, Kameda T and Takada S. On easy implementation of a variant of the replica exchange with solute tempering in GROMACS. J. Comput. Chem. (2010) 32, 1228-1234.
³ Laio A and Parrinello M. Escaping free-energy minima. Proc. Natl. Acad. Sci. U.S.A. (2002) 99, 12562-12566.
⁴ Puddu V, Slocik JM, Naik RR and Perry C. Titania binding peptides as templates in the biomimetic synthesis of stable titania nanosols: Insight into the role of buffers in peptide-mediated mineralization. Langmuir (2013) 29, 9464-9472.
⁵ Tang Z, Palafox-Hernandez JP, Law WC, Hughes ZE, Swihart MT, Prasad PN and Walsh TR. Biomolecular recognition principles for bionanocombinatorics: An integrated approach to elucidate enthalpic and entropic factors. ACS Nano (2013) 7, 9632-9646.

Designing new materials with well-defined structures and desired functions is a challenge in materials science, especially with nanomaterials. Nature, however, solves design of these materials through a self-assembling hierarchically-ordered process. We have investigated how the high- aspect ratio and unique surface chemistry of mutant M13 bacteriophage can give rise to increasingly complex, hierarchically ordered, bundled phage structures with a wide range of material applications. A molecular dynamic simulation of the 3-D structure of an subsection (~80 nm) of wild type (WT) and mutant phage particles were developed based on WT phage crystal structure and ab initio calculations. Simulations of phage particles were then used to examine repulsive and attractive forces of particles in solution. Examination of contact interactions between WT phage indicated an optimal interaction with phage in head to tail orientations. A mutant phage (4E) with a higher negative surface charge than WT also preferentially ordered head to tail in solution. However, a mutant phage (CLP8) with a net positive surface charge had minimal repulsion in a 90-degree orientation. Larger scale interactions were simulated using Discrete Element Modeling where full length, 800 nm, phage were interacted together under different conditions. Understanding the self-assembly process through molecular dynamic simulations and decomposition of fundamental forces driving inter- and intrastrand interactions has provided a qualitative assessment of mechanisms that lead to hierarchical phage bundle structures. We anticipate using this system to further investigate development of hierarchical structures not only from biological molecules but also from synthetic materials.

An area of growing interest is the development of noble-metal metamaterials because of their unique properties[1,2]. Development of versatile generation strategies for production of these metamaterials remains challenging; these materials comprise assemblies of nanoparticles of different compositions, arranged in 3-D arrays; fine control over the interparticle spacings in these arrays is essential. It is also highly desirable that these arrays can be dynamically reconfigured. As the first steps towards realizing these goals, we investigate Au- and Ag-binding peptide sequences conjugated with light-switchable azobenzene moieites, for the purpose of designing stimuli-responsive biomolecule linkers that can ultimately facilitate assembly of different types of nanoparticles into 3D arrays. Here, we use advanced sampling molecular dynamics simulations[3] to investigate the molecular conformations and materials-binding properties of these molecules. These peptide sequences have a light sensitive thiol-maleimide azobenzene thiol-maleimide (MAM) unit conjugated onto either the N- or the C-terminus of the peptide. We have also carried out well-tempered meta-dynamics[4] simulations to estimate the free energy of binding, of the MAM unit alone, at the Au and Ag aqueous interfaces. Our results indicate that the MAM unit binds more strongly at Au compared with Ag, with the trans conformation of the MAM binding more strongly than the cis for both metals. Our simulations of the N- and C-conjugated peptides reveal that the presence of the MAM unit can significantly affect the adsorbed structures and conformational dynamics of the surface adsorbed peptide. Our findings provide guidance in the design and development of a stimuli-responsive biomolecule linker for nanoparticle assembly purposes[5].
[1] P.-Y. Chen, J. Soric and A. Alu, Adv. Mater., 2012, 24, OP281-304.
[2] K. L. Young, M. B. Ross, M. G. Blaber, M. Rycenga, M. R. Jones, C. Zhang, A. J. Senesi, B. Lee, G. C. Schatz and C. A. Mirkin, Adv. Mater., 2014, 26, 653-9.
[3] T. Terakawa, T. Kameda and S. Takada, J. Comput. Chem., 2011, 32, 1228-34.
[4] A. Barducci, G. Bussi and M. Parrinello, Phys. Rev. Lett., 2008, 100, 020603.
[5] K. L. M. Drew, Z. Tang, J. P. Palafox-Hernandez, Y. Li, M. T. Swihart, C. -K. Lim, P. N. Prasad, M. R. Knecht and T. R. Walsh, in preparation.

Developing effective and environmentally friendly oil/water separation methods for cleaning oil spills is a worldwide challenge. One approach to this problem involves designing novel materials with special wetting behavior, inspired by superhydrophobic surfaces of plants and insects, and underwater superoleophobic surfaces of fish scales. Materials with superhydrophobic/superoleophilic surfaces are used to absorb or filtrate oil from oil/water mixtures, while superhydrophilic/underwater superoleophobic materials selectively remove water. We fabricated such materials by structuring conventional and wood-based polymers using a highly scalable low-cost hot pulling technique, in which softened polymers are locally elongated during demolding from heated sandblasted or microstructured plates. The resulting surfaces are covered with dense high aspect ratio nano- and microhairs, and are superhydrophobic and superoleophilic. The as-prepared surfaces absorb crude oil out of the water and separate oil/water mixtures. Moreover, the surface properties of the as-prepared materials can be changed to hydrophilic and underwater superoleophobic by a short argon plasma treatment cycle, making the nano- and microhaired surfaces capable of both ”oil-removing” and ”water-removing” oil/water separation methods. Additionally, by combining hot pulling technique with shape-memory polymers processing the hierarchical special wetting surfaces with increased fluid absorption are created.

Establishing controlled structures of biological molecules on nanomaterials with controllable interfaces is the first step in the development of novel bionanodevices. Single-layer graphene, MoS₂, and other 2-dimensional (2D) nanomaterials are ideal to form such bio/nano systems due to their atomically flat surfaces and unique electronic and optical properties. We have recently selected graphite binding short peptides using combinatorial mutagenesis which also bind to graphene and other single layer 2D nanomaterials. In particular, the selected peptide (GrBP5 with a sequence IMVTESSDYSSY) not only binds to graphene, but also undergoes self-organization to form ordered biomolecular nanostructures on the surface of graphene. Molecular interactions of the peptides with graphene involve binding, surface diffusion and intermolecular interactions followed by self-assembly. Each of these interactions can be controlled by point mutation of the amino acid domains along the sequence of the peptide which incorporates anchoring (underlined), neck and tail domains. Using atomic force microscopy, we demonstrate that engineered dodecapeptides form monolayer-thick ordered architectures on atomically flat surfaces of graphite commensurate with the underlying honeycomb lattice. Furthermore, via the mutation of the anchoring domain, the designed mutant peptides can also be made to bind to BN, and 2D transition metal chalcogenides, such as MoS₂ and WSe₂. Among the nanostructures form on the surface, for example, peptide nanowires have uniform dimensions, typically ~1-nm thick, ~12-nm wide, and micro-meters in length. These results indicate the strong structural correlation between self-organized peptide nanostructures and 2D nanomaterials. The coherent peptide conformation in nanowire structures potentially provides new opportunities to study fundamental interactions at the bio/nano interface towards developing novel bionanodevices. Research was co-sponsored by NSF-MRSEC program via DMR#0520567 at UW and JST-PRESTO program in Japan.

Calcium phosphate ceramics are considered very promising materials for the repair and regeneration of bone defects. Two of the most commonly investigated are Hydroxyapatite (HA) and β-Tricalcium Phosphate (β -TCP), which can be used together to form Biphasic Calcium Phosphates (BCP), combining the properties of both materials. The performance of calcium phosphate materials depends on their composition and structure at multiple length scales from macro to nano levels. However, it has been very difficult to develop effective manufacturing technologies that enable a fine control of architecture and surface topography in practical calcium phosphate ceramics.
This work describes a novel manufacturing process to fabricate calcium phosphate structures and surfaces with complex architectures based on the design of responsive particles (Angewandte Chemie International Edition 52(30): 7805-7808). The method uses a pH-responsive branched copolymer surfactant (BCS) to functionalize surfaces in situ and to create responsive particles that can self-disperse or assemble between themselves or with soft templates (i.e. in emulsified suspensions) under the action of an external trigger (pH). The system enables a careful control of the viscoelastic properties of the ceramic slurry, and may be integrated in additive manufacturing technologies to obtain materials with complex shapes and tailored microstrucures at different length scales. The structures can mimic to some extent the hierarchical architecture of natural materials such as trabecular bone opening new paths for the optimization of their mechanical and biological performance.
As an example we will show how responsive emulsions can be used to fabricate strong materials with porosities ranging between 50 to 80 vol%, pore size between 3 to 50 mu;m and a range of interconnectivities, surface topographies and structural gradients. The rheological response of the emulsions can be controlled to build materials with complex shapes by coagulation casting, tape casting or three-dimensional printing.

Robust synthetic biolubricants have been searched for the coating of implants and the treatment of diseases, such as osteoarthritis, without real success. A mucin known as lubricin, found in the synovial fluid, is believed to be the glycoprotein responsible for the low friction and wear protection of cartilage. However, lubricin cannot yet be obtained recombinantly and is very expensive to extract, hence a suitable lubricin-mimetic molecule is still to be discovered. In this study, we combined Atomic Force Microscopy (AFM) and Surface Forces Apparatus (SFA) spectroscopy to characterize surface coverage as well as normal and friction forces of a lubricin-mimetic pAA-PEG copolymer (pAA-62kDa, PEG-2kDa) interacting with fibronectin (FN), a protein of the extracellular matrix found in the superficial zone of cartilage.
The pAA-PEG polymer coverage, distribution, and roughness were quantified by AFM for three different polymer concentrations, 0.3mg/ml, 1mg/ml, and 3mg/ml. In parallel, both the normal and the lateral (friction) forces of pAA-PEG were recorded using the SFA, in presence and absence of FN. Our AFM data indicated that the pAA-PEG polymer (i) had an average contour length and a diameter of 72nm and 10nm, respectively, and (ii) could self-associate to form a highly interconnected network onto surfaces, at all three concentrations. Our SFA data showed that the pAA-PEG polymer was only weakly adsorbed onto (negatively charged) bare mica surfaces but became firmly attached when FN was added as a polymer linker. FN also appeared to act as an efficient protector against mica surface damage when shear was applied. All our friction data exhibited (i) low friction coefficients (mu; asymp; 0.25) up to applied pressures of circa 3MPa and (ii) Amonton&’s like behavior, although poor wear protection was observed in the absence of FN. Friction coefficients also showed a weak shear velocity dependency. Together, AFM and SFA have allowed us for molecular and microscopic characterization of the pAA-PEG helping us gaining insight into both the lubrication mechanisms and the interactions of the biomimetic polymer with tissue (FN). Collectively, these results indicate that our proposed lubricin-mimetic lubricant might be a promising cheap alternative to lubricin, as it improves lubrication and protects shearing surfaces against wear, in presence of the extracellular matrix proteins present in cartilage.

Lectin recognition by cell surface glycans influences various cellular behaviors, such as adhesion, migration, proliferation, differentiation, and apoptosis, and therapeutics that can modulate these interactions are receiving increased attention. Lectin binding specificity at the cell surface is governed by the action of glycosyltransferases that alter glycan composition, as well as local glycan density, with high-density glycans providing a “glyco-cluster effect” that stabilizes relatively weak monovalent interactions. We proposed that supramolecular assembly of glycopeptides would provide synthetic analogs of natural glycoclusters with tunable lectin binding properties, namely specificity and affinity. In particular, mixing different ratios of glycosylated and non-glycosylated β-sheet fibrillizing peptides in the pre-assembled state can provide nanofibers with tunable glycan density, whereas glycosyltransferases can be used to modify nanofibrillar glycan composition post-assembly. To test this hypothesis, we created a variant of a β-sheet fibrillizing peptide, QQKFQFQFEQQ (Q11), terminated with a monosaccharide, n-acetylgl

Water-responsive materials can swell and shrink in response to changes in relative humidity (RH). Bacillus spores are an example of a water responsive material that has demonstrated large energy density, high reversibility, and fast response speed to variations in relative humidity [1]. Spores can self-assemble into a dense monolayer structure on various substrates, and therefore have the potential to serve as building blocks for stimuli-responsive hybrid materials in actuators and energy harvesting devices. Here, we demonstrate that a hybrid material built with spores and plastics can be used for giant stroke actuation and energy conversion from evaporation. We assemble Bacillus spores on thin polyimide strips with specific geometric patterns. When the RH level changes, the spores curve the polyimide substrate into an approximately sinusoidal shape which results in a large linear motion at both ends of the strip. These hybrid materials experimentally show an actuation strain exceeding 200% and fast response speed to the changes in RH (~ 1 sec). The actuation can be scaled up by packaging these spore/plastic hybrid biomaterials in parallel. By using these packaged hybrid materials and combining them with valves controlling the passage of moisture, we built an oscillator that can harvest the evaporation energy when we place it directly above the surface of water. When liquid water is evaporating into the dry air, the oscillator continually shrinks and expands until the water dries out. The mechanical oscillation can drive a generator to produce electricity continuously when water is present. Our results suggest that these hybrid biomaterials are excellent stimuli-responsive materials for high efficiency actuators and energy harvesting devices.
References:
1. Xi Chen, L Mahadevan, Adam Driks and Ozgur Sahin, Bacillus spores as building blocks for stimuli-responsive materials and nanogenerators, Nature Nanotechnology9, 137-141 (2014).

The formation of complex biological materials with intricate structures is a source of inspiration for biomimetic approaches in solving a wide variety of technological problems in various fields of study. The modular nature of recently developed solid-binding peptides provides a simplified but versatile platform to study the fundamentals of biomolecular self-assembly. Here, we study the surface behavior of peptides, including binding, diffusion and assembly, using combinatorially selected graphite binding dodecapeptides on an atomically flat surface of graphite under a variety of solution conditions to establish the parameters of self-assembly. In particular, the assembly characteristics of the peptides were investigated with respect to ionic strength and pH of the incubating aqueous solution during the deposition process. The assembled nanostructures, ordered or random (amorphous), were found to be sensitive to both salt concentration and solution pH in the case of the negatively charged variants of the peptide, but was unaffected in case of the net neutral mutant. From these results, we conclude that the effect of both ionic strength and pH on the ordered self-assembly of peptides is predominantly due to the modulation of interpeptide Coulombic interactions. While the effect of ionic strength originates from the electrostatic shielding of interpeptide Coulombic interactions, the pH affects the peptide protonation state, greatly increasing the interpeptide Coulombic repulsion and affecting order versus disorder of the peptides that are bound to the graphite surface. Implications of these results in practical applications will be discussed. Research was co-sponsored by NSF-MRSEC program via DMR#0520567 at UW and JST-PRESTO program in Japan.

In spaceships and space stations, bubble generation in the tubes of heat exchangers and pumps is a critical problem. Under microgravity, low buoyancy causes a permanent adhesion of such bubbles on the inner surfaces of tubes, causing pressure losses, erosion of the surface and drop in the heat transfer efficiency. It has been reported that fish scales exhibit a high repellency toward hydrophobic oil droplets and air bubbles underwater, due to its hydrophilic nature and microstructured surface. We previously reported on the fabrication of self-organized honeycomb patterned porous film (HC) using the breath figure technique, which consist of casting a hydrophobic polymer solution containing an amphiphilic polymer under humid conditions. The condensed dew drops on the surface self-organize in a highly ordered hexagonal array and work as a template for the HC structure. Pincushion-like structures (PC) can also be obtained by peeling the top layer of the HC film. In this research, we report on the fabrication of hydrophilic microstructured surfaces with high bubble repellency on the inner surfaces of tubes by the breath figure technique. A HC film with pore diameter of 7-8 mu;m was obtained by casting a chloroform solution of polystyrene (PS) and amphiphilic copolymer on a glass substrate under high humidity. By peeling the top layer of the HC film, a PC film was also obtained. After UV-ozone treatment to make the films hydrophilic, the bubble repellency of the films was measured underwater by placing a bubble of 3mu;L. The contact angles in the case of HC (148.8°) and PC (165.3°) were higher than that of the flat film (128.0°), suggesting that the bubbles on HC and PC are in contact with a composite surface of water and hydrophilized PS. To calculate the contact angle phi; on a composite surface, we employed the Cassie-Baxter equation cosphi; = f_PS costheta;_PS + (1-f_PS) costheta;_water (eq1), where f_PS is the fraction of PS at the interface, theta;_PS the contact angle of air bubble on a flat PS surface, theta;_water the contact angle of air bubble on a layer of water. The calculated values from eq1 matched the measured contact angles, which increased with the decrease of PS fraction in the composite surface. In addition, the sliding angle of the bubble was the lowest for PC film (3.5 °) compared to HC (21. 8°) and flat film (39.1°), suggesting the high bubble repellency of PC structures. To fabricate such surface in a tube, a glass tube with 0.7 mm in diameter was dipped in the polymer solution and humid air was blown inside the tube. As a result, HC structures with pore size of 1-2 mu;m in diameter were observed. Then, the top layer of the HC film was removed by ultrasonic treatment of the tube in water, resulting in PC structures. We showed the fabrication of high bubble repellent surface on the inner surface of the tubes by the breath figure method.

Invertebrates have diverse mechanisms for the sclerotization of body structures. For example, the marine polychaete, Nereis virens, has mechanically robust mandibles composed of Nvjp-1, a histidine-rich protein that is involved in the hardening of the mandible after zinc binding. We have developed methods for the expression, purification and manipulation of Nvjp-1 which has enabled the fabrication of fibers and films. Like the worm jaw, these materials have demonstrated an increase in mechanical strength as a result of zinc binding. Unexpectedly, incubation of Nvjp-1 hydrogels with metal salts results in a ~90% reduction in size. Alternatively, exposure of Nvjp-1 hydrogels to low or high pH conditions results in swelling to ~2.5 times the initial cast size. Here, we present structural analysis of the Nvjp-1 materials after contraction in the presence of a variety of transition metal salts. Additionally, changes in structure are probed after swelling under both high and low pH conditions. We have also created a number of Nvjp-1 truncation mutants with the aim of identifying a minimal region responsible for the actuation properties observed with salt and pH changes. These results will be important in the creation of scalable, synthetic biomimetic materials that have tunable properties directed at the spatial and temporal induction of hydrogel actuation and material hardening.

Abstract
Healthy skin with robust skin regeneration provides the most effective defense against environmental infectants. Silk has been studied for skin regeneration and has been widely used as an additive for cosmetics. Silk improves collagen synthesis, re-epithelialization, wound healing, atopic dermatitis alleviation, and scar reduction. However, purified silk promotes microbial growth. Here, we propose for the first time, an electrospun silk scaffold doped with selenium nanoparticles to address this issue. Electrospun silk scaffolds have smaller interstices and higher surface areas, allowing for efficient nutrient transfer to skin. In addition, selenium nanoparticles have been shown to have excellent antibacterial properties. By incorporating selenium nanoparticles into silk, we expect to retain silk&’s beneficial skin healing properties while improving its antibacterial ability.
Materials and Methods
Silk was extracted from Bombyx mori by Rockwood&’s protocol¹ while selenium nanoparticles were synthesized by Tran&’s protocol² . Extracted silk was dissolved in formic acid at 8-14%, w/v, and spun at a flow rate of 2-3 mL/hr, distance to a collector at 10cm, and at a voltage of 20kV. Staphylococcus aureus (ATCC -10832D-5) was cultured on the substrates with 0, 7.8, 15.5, and 31 mu;g/mL selenium nanoparticles in 0.3% tryptic soy broth (Sigma-Aldrich). After 3-5 hours after inoculation, the plates were read at 562 nm to determine cell density. All experiments were conducted in triplicate and repeated at least three times. The electrospun scaffold was characterized by SEM and goniometry to determine the physical composition of the scaffolds ± selenium nanoparticles. Selenium nanoparticles were characterized by DLS to determine particle size and dispersity.
Results and Discussion
Electrospun scaffolds possessed fiber diameters of 200-300 nm and pore sizes of ~5µm. Surface contact angles were 500, showing a hydrophilic surface. DLS showed that the selenium nanoparticles were monodisperse, with hydrodynamic diameters around 100 nm. Results of this study showed that S. aureus growth was inhibited in the presence of selenium nanoparticles as early as 3 hours, and bacterial viability at 3 hours decreased from 90% in the control group to 60% in the treated groups. In the presence of selenium, the bacteria showed negligible growth while the control demonstrated continued proliferation.
Conclusions
Selenium nanoparticles are effective in decreasing S. aureus growth at even low time periods. Electrospun silk generates fiber diameter ~200 nm and micron sized pore sizes, ideal for cellular adhesion.
Acknowledgements
The authors thank William Fowle, Scott McNamara, and the Northeastern University Department of Chemical Engineering for facilities and funding.
References: 1). Rockwood DN, et al. Nat. Protocols. 2011; 6(10): 1612-1631. 2) Tran PA et al. I J Nanomed. 2011; 6: 1553-1558.

With small diameters and pore sizes, a large surface area to volume ratio, and tunable properties, nanofibers are an ideal scaffold material for tissue engineering and textile manufacturing. When spun from different polymers, nanofibers can exhibit a range of elasticities and scaffold mechanics necessary to mimic the mechanical properties of the skin. Using a perforated reservoir that uses centrifugal forces to extrude fibers, automated Rotary Jet Spinning (aRJS) has been demonstrated as a rapid and efficient method to produce nanofibers of varying mechanical strength with controlled fiber deposition. Currently, stiff bandages and clothing manufacturing lack a biomimetic range of motion. Although sewing different materials together has been utilized to mimic skin biomechanics in clothing, the seams in multi-material clothing are restrictive and likely points of failure. There is a need for a seamless multi-material solution that can more accurately recapitulate the dynamic properties of the skin. We hypothesize aRJS can be used to create a multi-material sleeve that enables and enhances a full range of motion for the end user in wound dressings and high performance applications. To test this hypothesis, we performed a biomechanical analysis of arm movement to motivate the design of our zoned scaffold. During flexural movement, we show that sections of the human arm experience heterogeneous extension and compression from the forearm to the shoulder. Based on these results, we zoned a soft polyurethane and stiff nylon onto a single cylindrical mandrel to create a seamless textile and tested its mechanical properties biaxially. Using 3D printing technology, we manufactured a scaled model of a human arm mandrel to test our ability to zone different materials at specific sections on the arm. Our results show that aRJS spun seamless materials have integrity at their interface as the structure remained intact when strained along the stitch-free material interface. aRJS can be used to create a multi-material, seamless sleeve to allow for therapeutic compression on the forearm and full range of motion at the elbow and upper arm. Without the need of additional sewing or stitching, zoning materials in this method provides a path to increasing the efficiency of textile manufacturing.

Compared with conventional top-down photo-cleavage method, we described a facile bottom-up ink-combination method to in-situ and rapidly achieve water wettability and adhesion transition with a great contrast on the superamphiphobic TiO₂ nanostructured film. Moreover, such combination method are suitable for various kinds of superamphiphobic substrate. Oil-based ink covering or removing changes not only the topographical morphology but also surface chemical composition, and these resultant topographical morphology and composition engineering realize the site-selectively switchable wettability varying from superamphiphobicity to amphiphilicity, and water adhesion between sliding superamphiphobicity and sticky superamphiphobicity in micro-scale. Additionally, positive and negative micro-pattern can be achieved by taking advantage of the inherent photocatalytic property of TiO₂ with the assistance of an anti-UV light ink mask. Finally, the potential applications of the site-selectively sticky superamphiphobic surface were demonstrated. In a proof-of-concept study, the microdroplets manipulation (storage, mixing, and transportation), specific gas sensing, wettability template for positive and negative ZnO patterning, and site-selective cell immobilization have been demonstrated. This study will give an important input to the field of advanced function materials surface with special wettability.

Micro-/nanomotors have fascinating capabilities to pick up, transport, and release various micro/nanocargoes because of their autonomous motion behaviors in liquid media, and can be used to perform complex tasks, including drug delivery, protein and cell separation, microsurgeries and environmental remediation, etc.. However, these tasks are difficult at microscale because it is still a great challenge to develop the high-speed micromotors with reversible and wirelessly tunable motion behaviors. In this work, other than the low-speed light-driven micromotors by diffusiophoresis, we have demonstrated the first example of the high-speed light-controlled micromotors by bubble propulsion, that is, the amorphous TiO₂/Au (Am-TiO₂/Au) Janus micromotors propelled by O₂ bubble thrust generated from the photocatalytic decomposition of H₂O₂ by TiO₂ under UV irradiation. The power conversion of the micromotor experiences a process from UV light power, to chemical power and finally to mechanical power. The quantum efficiency of O₂ bubble evolution from photocatalytic decomposition of H₂O₂ reaches 33%, and the power conversion efficiency reaches 3.2×10^-9, which make the micromotor generate a strong bubble thrust that propels itself forward with the maximum speed of 135 mu;m s^-1. The light-controlled TiO₂-based micromotors developed in this work may have promising applications in protein and cell separation, drug delivery, and water remediation etc..

Peptide vesicles are a new class of biocompatible vectors that display conformation-specific self-assembly. Vesicles composed of helix peptides have drawn attention of the drug delivery community lately because they offer high membrane stability due to helix bundling as well as conformation triggered disassembly.
We synthesized poly(ethylene glycol)-block-poly(γ-(4,5-dimethoxy-2-nitrobenzyl)-_L-glutamate) (PEG-b-PDMNBLG), a short lipid-mimic amphiphilic diblock rod-coil copolymer containing an hydrophobic, α-helical and photo-responsive polypeptide segment. The peptides self-assemble into quasi-spherical vesicular aggregates of ca 400nm in diameter, which is a suitable dimension for drug delivery applications. We unexpectedly observed by Cryo-EM that the vesicles have a dense membrane of roughly 40nm thicknesses. In order to get the structural details of these membranes we employed both Wide-Ange and Small-Angle X-ray Scattering (WAXS/SAXS) on concentrated solutions of peptide vesicles.
In this presentation we will reveal our WAXS/SAXS studies of peptide vesicle membranes. The systems displayed a few Bragg reflections that are consistent with the presence of a layered membrane structure with nematic ordering composed of four monomers as building blocks. In order to fully understand the driving force of this multilamellar membrane structure, we prepared three helices attached to PEG of different lengths. When short PEG molecules were used, multilayer membrane structures were formed with PEG buried between polypeptide layers, while the nematic alignment of helices was observed in the lateral direction. Longer PEG copolymers form membranes analogous to those typically obtained in lipid bilayers. In addition to the length of the PEG, the length of helix domain also plays a key role in the overall vesicle shape. It is found that there is an optimum length and ratio of each domain to achieve spherical aggregates. From these observations it is believed that short hydrophilic domains combined with an appropriate length of rigid hydrophobic parts are the key for the stabilization of multilamellar spherical peptide vesicles.

Nature provides us with numerous defense concepts in order not to be eaten. In plants, secondary metabolites often act as toxins.¹ For example, over 3000 species of higher plants use cyanogenesis. They are able to release HCN (hydrogen cyanide) from a cyanogenic precursor.² When the plant tissue is crushed, the cyanogenic glycosides are exposed to enzymes, which results in HCN-formation.³ HCN itself is known for its toxicity and ability to protect the plant from herbivores.
~600 million tons of wheat are harvested per year. This makes it one of the world&’s predominant crops.⁴ Pest infestation of cereal grains, such as wheat, still constitutes a worldwide issue, especially in developing countries.
In this work, a nature-inspired protection concept was developed.⁵ Seeds unable of cyanogenesis are intended to get more resistant against herbivore attack by a compartment strategy. Grains were coated with materials that allow HCN-production. These multi-layered seeds were prepared by dip coating and presented the following layers: (1) mandelonitrile lyase, (2) PLA (polylactic acid), (3) mandelonitrile in PLA, (4) pure PLA. As a proof of concept the obtained seeds were brought to germination within 4 days in a closed container. HCN was detected in concentrations (1.1 mmol kg^-1) known to have an effect on herbivores.^{5, 6}
1. Ibanez, S.; Gallet, C.; Despres, L., Plant insecticidal toxins in ecological networks. Toxins 2012, 4, 228-243.
2. Poulton, J. E., Cyanogenesis in plants. Plant Physiology 1990, 94, 401-405.
3. Conn, E. E., Cyanogenic glycosides. Academic Press, Inc.: 1981; p 479-500.
4. Ekboir, J., CIMMYT 2000-2001 world wheat overview and outlook: developing no-till packages for small-scale farmers. 2002.
5. Halter, J. G.; Chen, W. D.; Hild, N.; Mora, C. A.; Stoessel, P. R.; Koehler, F. M.; Grass, R. N.; Stark, W. J., Induced cyanogenesis from hydroxynitrile lyase and mandelonitrile on wheat with polylactic acid multilayer-coating produces self-defending seeds. J. Mat. Chem. A 2014, 2, 853-858.
6. Patton, C. A.; Ranney, T. G.; Burton, J. D.; Walgenbach, J. F., Natural pest resistance of Prunus taxa to feeding by adult Japanese beetles: Role of endogenous allelochemicals in host plant resistance. Journal of the American Society for Horticultural Science 1997, 122, 668-672.

Wetting behavior of biological surfaces such as the leaves of lotus, wings of morpho butterfly or legs of water strider insects have inspired the design of artificial water repellent surfaces. Over the past decade, we have witnessed many impressive reports demonstrating design and fabrication of superhydrophobic surfaces and explaining the mechanisms behind the non-wetting behavior (i. e. Cassie state of wetting) of such surfaces. Nevertheless, our understanding about the stability of Cassie state of wetting in superhydrophobic surfaces against external stimuli (e. g. pressure, droplet impact and droplet evaporation) is still quite limited. In fact, currently available self-cleaning surfaces generally fail in preserving the stability of non-wetting properties (i. e. transition to sticky Wenzel state) over time, especially in outdoor applications, in contrast with successful examples in natural surfaces. Therefore, improving the stability of Cassie state of wetting in self-cleaning coatings is a prerequisite for utilizing self-cleaning surfaces in real life applications. In addition, many applications of water repellent surfaces require optical transparency, such as self cleaning windows and solar cells in terms of appearance and device performance.
Here we report a facile large area sol-gel method to obtain bioinspired micro/nano structured transparent coatings with enhanced stability against external pressure. Three different organically modified silica (ormosil) coatings; i) nano-porous hydrophobic coating , ii) micro-porous superhydrophobic coating, and iii) double layer superhydrophobic coating with nano-porous bottom and micro-porous top layers were prepared on glass surfaces. We investigated stability of the Cassie state in coatings with droplet compression and evaporation experiments, where external pressures as high as a few thousands of Pa is generated at the interface. The resistance of the micro/nano-porous surface against Wenzel transition during the experiments was higher than of lotus leaves.
The outcomes of this study may provide researchers an adequate ground for designing robust superhydrophobic coatings for outdoor and underwater applications where surfaces are exposed to high external pressures.

Injuries to the nervous system often result in permanent disabilities including sensory deficit, loss of motor function, and development of debilitating neuropathies. Each year, there are approximately 1 million new cases of traumatic peripheral nerve injuries (PNI) and 12,000 new cases of spinal cord injuries (SCI) in the United States alone. Current treatment options for PNIs yield sub-optimal functional recovery, with only 50% of patients recovering useful function, due to design limitations of clinically available nerve conduits. Scaffolds manufactured by freeze casting exhibit a biomimetic structure which overcomes the physical limits of nerve conduits by providing a natural bridge for nerve regeneration. In this contribution we show how structural, mechanical and chemical cues can be custom-designed to produce freeze-cast scaffolds with aligned porosity and reproducible topographies. This biocompatible manufacturing process can be used to incorporate key structural and bioactive components to bridge the gap in nerve repair.#8203;

During the last few decades, research on biological materials such as abalone shell, fish armor, turtle shell, and human bone revealed that those biological systems possess a carefully arranged multilayered structure whereby each layer comprises unique subscale structures to achieve properties of high strength, high ductility, and light weight, which are far superior to any man-made materials and systems. In this research finite element modeling was used to investigate the delamination resistance for the bio-laminate structures. The Atractosteus spatulas (Alligator gar) was used as the model structure.
The Alligator gar possess a flexible dermal armor consisting of overlapping ganoid scales. Each scale is a bilayer hydroxyapatite and collagen-based bio-laminate and is thought to be used for protection against its predators. The exoskeleton fish scale is comprised of a stiff outer ganoine layer, a characteristic “sawtooth” pattern at the interface and a compliant bone inner layer with all materials exhibiting a decreasing elastic modulus, yield strength and density through the thickness. Experimental testing on ganoid scales display properties such as damage mitigation, tortuous crack path propagation, and energy dissipation that are unique to biological dermal armor. The main objective of this investigation is to quantify the effects of the material grading as a function of depth as well as the influence of the geometrically anisotropic interface between the ganoine and bone layers on the elastic properties. The fish scale interface was modeled using the finite element method. Preliminary results were based on an idealized elastic-perfectly plastic mathematical model. The mathematical model was used to infer the effects of the nonlinear material response in terms of in terms of energy dissipation and stress redistribution at the ganoine-bone interface. The results indicate that at the ganoine-bone interfaces stress is reduced and energy is dissipated across the saw tooth junction points.
Keywords: Biological Materials, Delamination Resistance, Alligator gar, Energy Dissipation

Biomolecular unit cells may be described as cell-inspired building blocks, whose repetition forms the basis of a novel biomolecular material system. The unit cell considered herein consists of a lipid bilayer interface formed at the contact of two aqueous droplets encased in lipid monolayers in an oil reservoir -- a technique known as the Droplet Interface Bilayer (DIB). The droplets are fixed on Ag/AgCl electrodes for measurements and characterization through patch-clamp methods. Various biomolecules can self-assemble in these interfaces, granting additional functionalities and sensitivities to the unit cell. Accordingly, the DIB has been extensively used to systematically study the activity of many biomolecules including voltage activated channels alamethicin, light activated proteins bacteriorhodopsin, and many others. This research focuses on the addition of mechanosensitive (MS) channels, which are able to respond to a tension in the lipid membrane. MS channels found in the E. Coli respond to a mechanical tension in the cell membrane helping the cell to survive hypo-osmotic shocks. In previous work, a low-threshold gain-of-function V23T mutant of MscL generated reliable activities as a response to micron-size droplet oscillations. The activities included sub-conductive states, as well as full-opening events, which are identical to those recorded using patch-clamp from intact inner E. coli membranes and liposomes reconstituted with the purified V23T MscL. This paper presents a parametric study to better understand the gating mechanism of MscL in the DIB. The MscL activities in the DIB are found to be dependent on the applied electrical potential, the oscillation amplitude, and the frequency of oscillations. Each of these parameters is studied separately in order to understand their effect on the membrane tension and changes in the droplet-interface bilayer properties. The variation in transmembrane potential has always been associated with a variation in the membrane tension as Lippmann&’s equation describes. A series of experiments are conducted where the transmembrane potential is increased and the bilayer area, angle, and capacitance are recorded. The results are combined with analytical models to track the tension variation in the membrane as a function of the voltage. The experimental setup used, allows the application of dynamic tension to the membrane by axially oscillating the motion of one droplet, producing deformation in both droplets, and an area change at the DIB interface. Another set of experiments are conducted where the amplitude and the frequency of oscillations are separately addressed. The results show that the bilayer angle decreases as the amplitude is increased, suggesting a rise in the membrane tension as shown by Young&’s equation. On another note, the frequency of oscillation is attributed to the rate of zipping of the bilayer in the compression stroke, which might create additional tension in the membrane.

In this work we have fabricated light-responsive hydrogel actuators using elastin-like polypeptide (ELP) and graphene nanocomposites. ELPs are biocompatible smart protein-based polymers. The incredible elasticity of ELP along with their thermal responsiveness makes the proteins valuable as components for scaffolds useful in tissue engineering and drug delivery. Another advantage of using ELPs is that functional modules can be genetically fused into the peptide chains instead of using intricate chemical modifications. We have fused ELPs with an aromatic amino acid containing sequence, ‘HNWYHWWPH&’ that can bind to graphene and its derivatives. The resulting ELP/graphene nanocomposites are light sensitive as graphene can absorb light and generate heat that stimulates ELP to collapse from a hydrated to a condensed state. A hydrogel composed of the ELP/graphene nanocomposites is also light responsive as they undergo deswelling and thus contraction as light is converted to heat by graphene.
By making the light-responsive hydrogels anisotropic with a porous and a solid layer, we alter the swelling/deswelling properties of each of the layers. The porous layer can exchange water efficiently causing a fast contraction and creating a stress in that layer. The stress is enough to cause the entire gel to undergo flexing motion. Using a modified Stoney equation with Atkinson correction factor, we will calculate stresses involved in gel flexing with respect to the power density of stimulating light. We can characterize forces generated by the gels and form a model useful to predict the amount of load that can be applied by these hydrogel actuators. These measurements will help characterize the capabilities of the gels and determine their utility as biocompatible soft robotic actuators.

The Reaction Centers (RCs) of photosynthetic organisms are efficient billion-of-years optimized photoenzimes for conversion of absorbed light into charge separated states. Combining RCs with tailored π-conjugated molecules is an intriguing approach to a new generation of versatile functional bio-nanomaterials for application ranging from photoconversion to photocatalysis and sensing.
We present here the design and synthesis of hybrid bio-organic photosynthetic complexes by combination of the Reaction Center (RC) of the photosynthetic bacterium Rhodobacter sphaeroides R26 with tailored molecular semiconductors. The organic molecules can act as antennas to extend the light harvesting capability of the RC, thus enhancing its photoconversion performances [1] and also accelerating charge transfer processes to external electron acceptors.
We also demonstrate that such hybrid architectures can be incorporated in the functional membrane of tailored polymersomes, still maintaining their full functionality, or even be anchored on electrode surfaces.
References
[1] F. Milano, R.R. Tangorra, O. Hassan Omar, R. Ragni, A. Operamolla, A. Agostiano, G.M. Farinola, M. Trotta Angew. Chem. Int. Ed. 51, 11019 (2012)

Engineering surfaces that promote rapid drop detachment is of importance to a wide range of applications including anti-icing, dropwise condensation, and self-cleaning.^1,2 Despite over a decade of intensive research, these surfaces are still plagued with problems that restrict their practical applications: during the dynamic impact, the interaction between the drop and the solid surface is constant, which is independent of the impact velocity for the following classical dynamic process demonstrated by many researchers. The drop first undergoes an inertia-dominant horizontal spreading, retracts on the liquid-repellant surface to minimize the surface energy, and finally takes off in the vertical direction. Meanwhile, common wisdom holds that the contact time is dominated by the retraction process which accounts for ~75% of the whole time.³ Using the integrated mechanical-cutting/chemical-etching methods, we recently fabricated superhydrophobic surfaces patterned with lattice arrays of submillimetre-scale posts decorated with uniformed nanotextures designed to eliminate the retraction process of the drop, allowing the drop to bounce off the surface with a fourfold reduction in contact time compared to that in conventional complete rebound. Such a bouncing is characterized by drop detachment from the surface close to its maximum lateral extension, a behaviour that we shall term pancake bouncing.⁴ In particular, through elaborate control of the chemical-etching cycle, a kind of tapered arrays were obtained which behave as harmonic springs to further enhance the pancake bouncing, allowing the occurrence of pancake bouncing and rapid drop detachment in a wide range of impact velocities. We also found that, on the tilted surface with an appropriate tilt angle, the impacting drop bounced off the surface in a pancake shape with a much shortened contact time and left the field of view before bouncing again. We believe that the discovery of pancake bouncing which can achieve significantly shortened contact times through manipulating the surface structure not only enriches our fundamental understanding of wetting dynamics, but will also stimulate new applications^1,2,4.
References:
1. Blossey, R. Self-cleaning surfaces - virtual realities. Nat Mater2, 301-306 (2003).
2. Bird, J. C., Dhiman, R., Kwon, H. M. & Varanasi, K. K. Reducing the contact time of a bouncing drop. Nature503, 385-388 (2013).
3. Richard, D., Clanet, C. & Quere, D. Surface phenomena: Contact time of a bouncing drop. Nature417, 811 (2002).
4. Liu, Y. et al. Pancake bouncing on superhydrophobic surfaces. Nat Phys, doi:10.1038/nphys2980 (2014).

The structural organization of matter is determined by the interplay of interaction forces, entropic effects, and the system&’s dynamic. Unlike atoms, colloidal systems can be tuned over the broad spectrum of sizes, shapes, and interactions, which is promising for the by-design self-assembly of these systems. Despite the diversity of discovered phases and assembly strategies, it has been challenging to establish a broadly applicable assembly platform for “a la carte” creations of structures from nano-objects of different types. Moreover, our abilities to regulate the structural transformations remain limited.
One of the promising assembly strategies relies on the incorporation of biomolecules into a nano-object. Bio-encoding provides a unique opportunity to establish selective and reversible interactions between nano-objects. Thus, complex multicomponent systems can be potentially fabricated via self-assembly: biomolecules act as site-specific scaffolds, smart assembly guides, and reconfigurable structural elements. I will discuss our advances in addressing the challenges of by-design nanoparticle self-assembly using the DNA-guided interactions. Our work explores the leading parameters determining a structure formation from DNA-encoded nanoparticles, including three-dimensional superlattices, two-dimensional membranes and finite-sized clusters. New effective strategies for the creation of superlattices with pre-defined crystallographic symmetries and particle clusters with prescribed architectures will be demonstrated. Finally, DNA-programmable systems with regulated transformation pathways will be discussed.
Research is supported by the U.S. DOE Office of Science and Office of Basic Energy Sciences under contract No. DE-AC-02-98CH10886.

De novo design and shaping inorganic nanostructures is a key foundation in nanotechnology and promises diverse applications in photovoltaics, plasmonics, and electronics. Particularly, using preformed polymeric patterns as templates, researchers have achieved the shape-specific engineering of diverse inorganic materials. However, it is still a challenge for scalable constructing inorganic nanostructures with arbitrarily prescribed, asymmetric architecture at sub-10 nm resolution.
Recently, DNA self-assembly has emerged as a powerful method to generate nanopatterns with arbitrary defined shapes. Particularly, scaffolded DNA origami strategy, assembling a structure by folding a long single-stranded DNA scaffold (7-8-kb long M13 viral genome) via its hybridization with hundreds of short synthetic ‘staple strands&’, has produced 100-nm scale complex prescribed 2D/3D structures with 3 nm. Limited by its scaffold length, it&’s generally difficult to achieve micron-scale patterns made from DNA origami.
Using a different modular building block, known as single-stranded DNA bricks, we previously reported the construction of more than 100 2D/3D structures with intricate cavities and tunnels, with the help of computer-aided design software. The modularity of DNA bricks further enables a general approach to engineer micron-sized two-dimensional patterns with prescribed thickness and complex surface features. Successful transfer of spatial information encoded within the DNA templates, self-assembled from DNA bricks, to diverse 2D/3D materials will enable simple and versatile approaches to produce inorganic nanomaterials of prescribed architectures over large dimensions. Here we report two different ways to use DNA brick structures for rational engineering of inorganic materials. In solution, DNA brick-based structures direct the positioning of metal nanoparticles into 2D/3D prescribed plasmonic architectures. Additionally, not only symmetric architectures, but also asymmetric ones can be assemled onto DNA brick structures, owing to their single-strand addressability. In extreme conditions, DNA brick structures perform as lithographic masks, to direct the one-step etching of prescribed 2D/3D patterns onto inorganic structures, such as graphene and Si. Using DNA brick structures, engineering inorganic materials can be achieved at a spatial positioning resolution of 3 nm, which is beyond most of the existing top-down and bottom-up approaches.

We developed a method to assemble magnetic, high-performance, DNA comprising nanocomposites.¹ The nanoengineered particles consist of Fe₂O₃ cores, a silica shell, and dsDNA sequences layered in between. Fe₂O₃ nanoparticles were synthetized by a technique based on co-precipitation, and decorated with ammonium groups. DNA was adsorbed on this support, further coated with a dense silica layer grown by sol-gel chemistry. The iron oxide accounts for the magnetic properties of the obtained particles. The outer silica matrix offers surface functionality and provides DNA stability in harsh conditions, mimicking the protective hermetic diffusion barrier of fossils.² DNA encapsulated within the particles was preserved for 2 years at room temperature, and its degradation was prevented at high temperatures (up to 160°C). DNA could be recovered unharmed upon particle dissolution in fluoride comprising buffers, and analyzed by qPCR and Sanger sequencing.
The produced hybrid nanomaterial is an optimal tool for in-product labeling. The use of DNA-based barcodes ensures high versatility of coding. The particles are inert, resistant, invisible (at concentrations lower than 1 mg/L), and harmless, since iron oxide and silica are used as food additives. The magnetic core facilitates particle handling/separation, and allows for sample pre-concentration prior to analysis. Therefore, we developed a potent and low-cost platform for tracing/tagging liquid items. The nanocomposites are dispersed in the liquid media of interest and further retrieved by magnetic separation, followed by particles dissolution and DNA analysis by qPCR.
We decided to utilize the novel nanotag against oil counterfeiting, fuel stealing and smuggling, an issue in many countries. To this aim, the nanocomposites were functionalized with hydrocarbon chains to achieve dispersibility in hydrophobic liquids. Magnetic separation allowed DNA analysis out of oils, otherwise prevented. The procedure was tested with a fuel (gasoline), a cosmetic oil (bergamot oil), and a food grade oil (extra virgin olive oil). We could successfully retrieve and detect the tags by qPCR in organic solvents (toluene, decalin) and in the oils. We statistically discriminated 10 fold dilution steps of the oil suspensions, down to a concentration of 1 µg taggant per liter of oil (i.e. ppb levels). Therefore, the developed high-performance nanocomposite tag enables to discriminate adulterated items (e.g. fake, diluted products) and determine oil origin/legitimacy.
1. Puddu, M.; Paunescu, D.; Stark, W. J.; Grass, R. N. Magnetically Recoverable, Thermostable, Hydrophobic DNA/Silica Encapsulates and their Application as Invisible Oil Tags. ACS Nano2014, 8, 2677-2685.
2. Paunescu, D.; Puddu, M.; Soellner, J. O. B.; Stoessel, P. R.; Grass, R. N. Reversible DNA Encapsulation in Silica to Produce Ros-Resistant and Heat-Resistant Synthetic DNA 'Fossils'. Nat. Protoc. 2013, 8, 2440-2448.

Aptamers are single-stranded oligonucleotide sequences that exhibit high affinity and specificity for particular non-nucleotide targets including, but not limited to small molecules, proteins, and even whole cells. Aptamers are conventionally identified using a multi-round screening approach called "Systematic Evolution of Ligands by Exponential Enrichment" (SELEX) in which a pool of approximately 10⁹ random candidate sequences is continuously enriched with amplified copies of “winning” sequences or adsorbates from prior selection rounds. While SELEX has revolutionized the discovery of numerous DNA and RNA-based aptamers for a variety of targets, we have developed a non-SELEX screening approach to identify single-stranded DNA aptamers for gold substrates. One of the key differences in our non-SELEX screening approach is the elimination of intermittent elution and amplification steps of random sequences that can (1) introduce undesired PCR side products (e.g. partially elongated duplexes) into the candidate pool and (2) bias the candidate pool towards early winners that may simply outnumber higher affinity aptamer candidates introduced at later selection rounds. Following aptamer selection against our gold substrate, we then evaluate sequences to identify base consensus as well as shared structural elements such as hairpins, internal loops, and bulges to reveal any shared patterns in the primary and secondary structures of the aptamer sequences. As aptamers continued to be pursued as potential analogs and even substitutes for antibodies in the broader materials community, we continue to adapt our unconventional screening approach to hopefully enable faster and easier aptamer identification for a rich range of non-nucleotide targets.

We build branched DNA species that can be joined using Watson-Crick base pairing to produce N-connected objects and lattices. We have used ligation to construct DNA topological targets, such as knots, polyhedral catenanes, Borromean rings and a Solomon's knot.
Nanorobotics is a key area of application. We have made robust 2-state and 3-state sequence-dependent devices and bipedal walkers. We have constructed a molecular assembly line using a DNA origami layer and three 2-state devices, so that there are eight different states represented by their arrangements. We have demonstrated that all eight products can be built from this system.
One of the major aims of DNA-based materials research is to construct complex material patterns that can be reproduced. We have built such a system, which can reach 2 generations of replication. In a new system that demonstrates exponential growth, we are progressing towards selection of self-replicating materials.
Recently, we have self-assembled a 3D crystalline array and reported its crystal structure to 4 Å resolution. We can use crystals with two molecules in the crystallographic repeat to control the color of the crystals. Rational design of intermolecular contacts has enabled us to improve crystal resolution to better than 3 Å. We are now doing strand displacement in 3D to change the color of crystals. Thus, structural DNA nanotechnology has fulfilled its initial goal of controlling the internal structure of macroscopic constructs in three dimensions. A new era in nanoscale control awaits us.

With increasing energy demand and the environmental effects of fossil fuel consumption, much effort has focused on discovering alternate sources of renewable energy. One approach has been to mimic the photosynthesis process by using photocatalysts to run oxidation and reduction reactions. Due to their ability to absorb light in the visible region, semiconducting nanostructures or quantum dots (QDs) have been studied extensively as materials for photocatalysis. Since single-component semiconductor systems suffer from photodegradation and slow hole transfer kinetics, heterogeneous systems that couple oxidation/reduction catalysts to QDs have also been studied in recent years. To date, most of these have either grown a particular type of catalyst on a semiconducting nanocrystal or used electrodeposition. In this presentation I will show an alternate method that uses electrostatic and DNA interactions to assemble CdS nanorods and Co₃O₄ nanoparticles into photocatalytic systems that simultaneously oxidize water and mediate electron transfer. We first demonstrate that layered films of CdS nanorods and Co₃O₄ nanoparticles can efficiently generate high photocurrents electrochemically as opposed to CdS or Co₃O₄ alone. We then show that dispersed clusters of CdS nanorods and Co₃O₄ nanoparticles held together by acid-base or DNA interactions can efficiently oxidize water and reduce methylene blue in solution. The lessons obtained from this research will enable designing and assembling new photocatalytic systems for producing high-energy products from reactants such as H⁺ or CO₂. If time permits, I will also demonstrate recent work in my group on using purely biological systems to produce technologically important chemicals such as butyraldehyde by utilizing a specific microbe in conjunction with a water-soluble catalyst.

Lanthanide-doped nanoparticles exhibit unique luminescent properties, including a large Stokes shift, a sharp bandwidth of emission, high resistance to optical blinking, and photobleaching. Uniquely, they can also convert long-wavelength stimulation into short-wavelength emission. These attributes offer the opportunity to develop alternative luminescent labels to organic fluorophores and quantum dots. In recent years, researchers have taken advantage of spectral-conversion nanocrystals in many important biological applications, such as highly sensitive molecular detection and autofluorescence-free cell imaging. With significant progress made over the past several years, we can now design and fabricate nanoparticles that display tailorable optical properties. In particular, we can generate a wealth of color output under single-wavelength excitation by rational control of different combinations of dopants and dopant concentration. We can obtain unprecedented single-band emissions by careful selection of host matrices. By incorporating a set of lanthanide ions at defined concentrations into different layers of a core-shell structure, we have expanded the emission spectra of the particles to cover almost the entire visible region, a feat barely accessible by conventional bulk phosphors. Importantly, we demonstrate that an inert-shell coating provides the particles with stable emission against perturbation in surrounding environments, paving the way for their applications in biological systems.

In this talk I will survey a large number of experiments performed in recent years in my group as well as in other groups on the interactions of mixed-ligand lnoble-metal nanoparticle with cell membranes and lipid bilayers. It will be shown that ambiphilic mixed-ligand gold nanoparticles posses a negative free energy of interactions with lipid bilayers that leads to the spontanoues fusion of these two objects. This property is of central importance in determining the interactions of these particles with cell membranes. If fact it allows the presence of a parallel non-endocytotic pathway of internalization of these partilces with most cells. A physical-chemical explanation for this phenomenon will be provided, together with numerous example of interactions. Pathways for exploiting this phenomenon in various bio-medical applications will be illustrated.

An artificial virus model system is introduced here, comprising glycosphingolipid containing liposome wrapped around an 80nm Au nanoshpere. The artificial virus nanoparticle was applied to probe the specific interaction between sialic acid containing glycosphingolipids and sialoadhesin for the initial capture of virus particles by dendritic cells or sialoadhesin expressing Hela cells. Unlike the same sized Au nanoparticles or same composited liposomes which are endocytosed by cells, the artificial virus nanoparticles mimics HIV-1&’s behavior, redistributing to confined compartments in peripheral cell areas. Upon the formation of DC-T cell conjugates, the artificial virus nanoparticles further relocate towards the infection synapse, which is a crucial step for HIV-1 transmission into T cells.
Noble metal nanoparticles provide excellent contrast for electron microscopic investigation of the spatial nanoparticle distribution, especially when combined with focused ion beam milling. FIB-SEM studies revealed artificial virus nanoparticle clustering in direct vicinity of the cell membrane. The unique spatial sequestration of nanoparticles was observed for glycosphingolipid containing membranes assembled around a solid noble metal nanoparticle core but for liposomes, indicating that the mechanical properties of the artificial virus nanoparticles play a role in triggering a specific cell response.

Lipid bilayers are ubiquitous in nature and are being implemented in sensors by engineers and researchers in lipidomics and proteomics. A lipid bilayer serves as a fluid matrix into which a large variety of transmembrane peptides and proteins anchor for signaling and transport. Interactions between membranes and peptides are also responsible for many diseases. For example, amyloid-β (Aβ) peptide interactions with bilayers cause neural cell death, a critical factor in Alzheimer&’s and Huntington&’s diseases and Down&’s syndrome. While it is known that phospholipid composition affects peptide-bilayer interactions, a majority of bilayers used to study protein-membrane interactions utilize simple lipid mixtures that do not closely mimic the heterogeneous composition of natural biological membranes. Thus, there is motivation to develop simple methods for assembling better model membranes in order to elicit native peptide conformation and function. Recently, we demonstrated that controlled heating could be used to promote monolayer assembly for droplet interface bilayer (DIB) formation with total lipid extract from E. coli.
Herein, we pursue a similar protocol to form DIBs using brain total lipid extract (BTLE) to create model membranes that mimic the structure and composition of neural cell membranes. The significance of lipid composition is investigated by using BTLE bilayers to study membrane permeation by Aβ peptides. Electrical measurements of resistance, capacitance, and rupture potential will be performed to compare the sealing properties of BTLE DIBs to those commonly formed with 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) lipids. Effects of differences in lipid composition on Aβ insertion will be studied using both electrophysiology measurements and spectroscopic techniques. Electrical measurements made at low Aβ concentrations will be used to visualize Aβ-associated poration of DIBs at a resolution capable of detecting single ion channels. To study Aβ-associated changes at higher peptide concentrations, we will investigate the ensemble conductance of Aβ-doped bilayers with cyclic voltammetry (CV). Incorporating fluorescent Aβ will also allow optical tracking of Aβ localization and migration in DIBs. The secondary structure of Aβ peptides in the presence of both BTLE and DPhPC lipids will be compared using circular dichroism (CD). Further, we aim to explore the role temperature on Aβ-bilayer interactions since temperature is known to affect Aβ self-assembly kinetics and also significantly affects bilayer mechanical properties and phase. The ability to control temperature is easily implemented with CD measurements and DIB experiments. Thus, Aβ-bilayer interactions will be studied at room temperature to compare with previous literature and also at 37°C, which is more biologically relevant for humans.

Integrin based adhesion has been shown to participate in numerous processes in living cells, which sense, via their adhesions, multiple environmental cues, integrate them, and develop a complex, multi-parametric response. However, due to their intrinsic molecular complexity the specific functional roles of different components of the adhesion site are still poorly understood. To address this issue, we utilize current knowledge of the modular nature of focal adhesions and related integrin-mediated extracellular matrix contacts, to develop “synthetic cell” models, consisting of large lipid vesicles, functionalized by transmembrane integrins, various integrin-binding proteins, and specific sets of scaffolding and signaling proteins of the adhesion sites. The one-by-one loading of these vesicles by micro-injection technology with these proteins allows us to tightly control the composition and the complexity of the system and test the effect of compositional and environmental variations on the adhesion and signaling features.

For future regenerative medicine using human Embryonic Stem Cell (hESC), development of chemically defined culture platform is essential. Numerous materials such as proteins, peptides, and synthetic polymers have been explored for the replacement of chemically undefined Matrigel and others. However, few of those attempts have been successful to replace Matrigel and the development of inexpensive, scalable, and chemically defined material still remains as a challenging subject. So far, studies about functional polysaccharides as potential candidates for the chemically defined platform to culture hESCs have been rather under performed. Here, we introduce a new class of polysaccharide derivative called hepamine for feeder-free maintenance of hESC. The hepamine is dopamine conjugated heparin (heparin + dopamine) in which the conjugated dopamine plays an important role in robust surface adhesion inspired by marine mussels. Surface plasmon resonance spectroscopy showed that hepamine easily functionalizes polystyrene dishes to from thin nanolayer whereas chemically unmodified heparin (as a control) was not adsorbed on the culture dish. On the hepamine-coated substrate, 80 % of the colonies robustly adhered and maintained expressions of pluripotency markers, Oct4, Sox2, and Nanog even after four passages. Interestingly, we found that the expressions of differentiation markers for three-germ layers were more suppressed for hepamine-coated dishes than Matrigel-functionalized ones. More importantly, when the hepamine was coated with collagen type Ι, it was able to support long-term growth of hESC over 18 passages and the passage experiments are still on going. The hESCs obtained from eighteen-passaged samples maintained their pluripotency, exhibited normal karyotype, and showed significant suppression of three-germ layer differentiations. Considering the fact that collagen itself generally cannot support long-term, undifferentiated growth of hESC, we propose that hepamine played a crucial role in suppressing the differentiation of hESC during such a long-period culture (i.e. 18 passages) on the hepamine/collagen-functionalized substrate. We attributed this unprecedented capability of hepamine supporting undifferentiated hESC growth to, in part, its high binding affinity for vitronectins, one of the important adhesion proteins in extracellular matrix.

The droplet interface bilayer (DIB) is a convenient method to mimic the lipid bilayer structure of cell membranes found in living organisms. In this technique, two lipid-coated aqueous droplets placed under suitable solvent are brought into contact to form a lipid bilayer at the region of contact. This platform has been used to study the electrical properties of several transmembrane proteins such as alamethicin, α-hemolysin, and other transmembrane proteins. This platform has also been used to make bioinspired batteries and electrical rectifiers using proteins as the functional elements. The convenient property of DIB technique to separately control the lipid composition of the either leaflet of the bilayer and the aqueous phase compositions across the membrane provides a tremendous advantage over other techniques.
In a vision to develop a renewable bioinspired solar cell that converts light energy into electrical energy, we seek to incorporate Photosystem I (PSI) - a membrane protein complex involved in the photochemistry of photosynthesis seen in algae, plants, and cyanobacteria - into DIBs. In native cells, PSI transfers electrons from the luminal side to the stromal side of the membrane upon absorption of light. Previous works in this field suggest that proper insertion and orientation of PSI in the lipid bilayer is crucial for its functionality in artificial environments. Moreover, negatively charged lipids such as phosphatidylglycerol (PG) are known to promote the insertion of PSI in its native membrane.
In this work, we pursue creating a thylakoid model membrane using DIBs. Specifically, we aim to fine-tune the phospholipid composition (PG/PC tail lengths and ratio) of the bilayer and the chemical composition of the droplets (electron donor and acceptor choices) on either side of the membrane to facilitate insertion and correct orientation of PSI complexes. Electrical properties of such charged-DIBs will be characterized based on their response to applied voltage. Understanding the electrical properties of these charged DIBs is an essential step before introducing PSI to study its behavior. Finding the right combination of lipid mixture and chemical composition of the aqueous droplet will take us one step closer to making bioinspired solar cell using PSI a reality.

The incorporation of hydrophilic regions into a superhydrophobic surface can impart additional functionality that significantly enhances the performance of the material. For example, the hydrophilic regions on the floating water fern Salvinia molesta helps trap and retain air bubbles¹ and so stabilizes the plant near the surface even in the presence of flowing water. Although low energy surface chemistry is generally considered a requirement to achieve stable superhydrophobic properties, the behavior of S. molesta, demonstrates that selective regions of hydrophilicity can stabilize the solid-liquid-gas triphasic interface.
In this paper we demonstrate a stable synthetic superhydrophobic surface that incorporates hydrophilic TiO₂ nanoparticles. The addition of TiO₂ particles, positioned at the tips of flexible posts, provides a photocatalytically active surface that maintains the long-term stability of the Cassie state when the surface is exposed to UV light. By partially embedding the particles into a high aspect ratio polydimethylsiloxane (PDMS) surface², sufficient hierarchical roughness is achieved to insure stable superhydrophobicity under continuous UV irradiation, even when the surface is fully coated with particles. This stability of the plastron stands in sharp contrast to other superhydrophobic surfaces based on TiO₂ that undergo a Cassie-Wenzel transition when exposed to UV light^3,4.
The multifunctional properties of the surface also contribute to its stability. Contamination from organic molecules and proteins renders most surfaces hydrophilic such that superhydrophobicity is lost. Protein layers are also known to promote the growth of biofilms. We show that reactive oxygen species generated on the TiO₂ surface effectively photo-oxidize model contaminants (Rhodamine B and Bovine Serum Albumin), maintaining the cleanliness as well as the surface roughness. Moreover, the relatively course pitch of the printed PDMS posts, enables the surface to be supported on a porous substrate. Thus oxygen in the plastron, that is consumed during photocatalysis, can be easily replenished thus insuring high photooxidation rates over long times.
The low-cost printing process used to fabricate these surfaces should facilitate applications for water purification and medical devices where Cassie stability is required.
References
1. Barthlott, W., Schimmel, T. Wiersch, S., Koch, K., Brede, M., Barczewski, M., Walheim, S., Weis, A., Kaltenmaier, A., Leder, A., Bohn, H.F. Adv. Mater. 2010, 22, 2325-2328.
2. Zhao, Y., Liu, Y., Xu, Q. F., Barahman, M., Bartusik, D., Aebisher, D., Greer, A., Lyons, A. J. Phys. Chem. A. 2014. doi/pdf/10.1021/jp503149x.
3. Xu, Q. F., Liu, Y., Lin, FJ., Mondal, B., Lyons, A.M. ACS Appl. Mater. Interfaces, 2013, 5, 8915-8924.
4. Sun, W., Zhou, S., Chen, P., Peng, L. Chem. Commun. 2008, 5, 603-605.

A dense gel constitutes the intracellular matrix of living cells. There biochemical reactions involving reactive enzymes, nucleic acids or proteins originate life functions. Those reactions induce conformational movements of the biopolymers. Thus, the reaction induced conformational movements of myosin or actin are the basic motors for any macroscopic (muscular) or microscopic movement in living beings. Today chemical and biochemical models are based on reactions taking place in gas phase or in dilute solutions. During the last 30 years reactive (electrochemically active) gels are available from conducting polymers and other carbon based molecules and structures. Using conducting polymer films as working electrodes in electrochemical cells, consecutive electrons are extracted from each constitutive polymeric chain under oxidation by flow of anodic currents generating consecutive radical-cations along every chain. Counterions (anions) and water are forced to penetrate into the film from the solution for charge and osmotic balance. A dense gel constituted by reactive polymeric chains, ions and solvent is originated, becoming a material model of the intracellular matrix (in its simplest expression) of living cells. The magnitude of any material property being a function of its composition (volume, stored charge, stored ions, porosity, color, conductivity, and so on) will shift in a reversible way during the gel oxidation/reduction. Most of those properties mimic biological functions originating biomimetic devices (artificial muscles, all organic batteries and supercapacitors, smart windows, smart membranes, artificial chemical synapse, smart drug delivery) here presented. Any variable acting on the driving reaction rate will be sensed by the device potential or consumed energy during actuation: those devices are sensing -actuators and several tools work simultaneously in one device.
Acknowledgments: Authors acknowledge financial support from Spanish Government (MCI) Project MAT2011-24973, Jose G. Martinez acknowledges to the Spanish Education Ministry for a FPU grant (AP2010-3460).
References
[1] TF Otero, JG Martinez, J Arias-Pardilla, Biomimetic electrochemistry from conducting polymers. A review: Artificial muscles, smart membranes, smart drug delivery and computer/neuron interfaces. Electrochim. Acta 84, 112-128, (2012)
[2] T. F. Otero and J. G. Martinez, Biomimetic intracellular matrix (ICM) materials, properties and functions. Full integration of actuators and sensors. J. Mater. Chem. B, 1, 26-38 (2013).
[3] TF Otero, Reactions drive conformations. Biomimetic properties and devices, theoretical description. . J. Mater. Chem. B, 1, 3754-3767 (2013).

Many biomaterials combine disparate properties such as exceptional strength, toughness and extensibility with tenability, mutability and a functionality that is unmatched by most man-made materials. This functionality emerges often from simple and abundant constituents that allow the adaption to changing environmental conditions through various feedback loops. Many constituents used in biology are in terms of their properties inferior to current synthetic materials because energy as well as material quality and availability are scarce. The excellent performance of many biomaterials originates from a combination of hard and soft building blocks in a multilevel hierarchical structure. A hard inorganic component serves as the reinforcing part and the soft biopolymer allows dissipating energy.
We have exploited the structure-function relation of nanoscale assembly to synthesize hard and tough multilayered DOPA polymer/metal oxide nanoparticles (Fe₃O₄ and TiO₂) nanocomposites. With Young&’s moduli of 25 and 17 GPa, respectively, and a hardness of approximately 1.1 GPa the resulting materials exhibit high resistance against elastic as well as plastic deformation. The cross-linked composites are highly uniform, flexible, and transparent. Thermogravimetric analysis revealed a polymer content of approx. ~30 wt %. These results can be explained from the nanoscale dimensions of the inorganic phase and the close packed arrangement of the nanoparticles. The lamellar nanocomposites contain distinct alternating layers of metal oxide nanoparticles and polymer, strongly cemented together by chelation through infiltration of the polymer between the oxide nanoparticle mesocrystals.
Therefore many strong metal polymer bonds have to be broken prior to mechanical failure. The individual nanoparticles are too small to break. In essence, the strong crosslinking between the particles and a multidentate polymer ligand help the matrix resist deformation and make the composite hard and strong. The resulting structure has the characteristics of adhesion and high tensile strength, the hallmark of the original biocomposites in nature. Annealing of the hybrid materials induces oxidative hardening through temperature-induced crosslinking. Metal-mediated catechol crosslinking leads to an increase of the Young&’s moduli compared to the non-reinforced polymer. The E-moduli of the DOPA polymer/metal oxide nanocomposites range among the highest reported for inorganic nanoparticle/polymer composites. In conventional particle-reinforced composites the particle size are in the micron range, and the particles carry a major portion of the load. They strengthen the material by impeding slip and dislocation, but do not react with the matrix. In our approach an ordered arrangement of hard metal oxide nanoparticles is infiltrated with “sticky” polymers that cross-link many nanoparticles.

Nanostructured metallic materials, such as silicon and titanium, represent promising building blocks for the construction of electrodes in several energy-related devices. Currently, the methods employed for patterning metallic thin films are energy-intensive, and produce micro-scale patterns, as opposed to nanoscale structures. Here, we report the assembly of fine nanoporous silicon and titanium structures using various biotemplates. Several micro-organisms exhibit fascinating and unique shapes that cannot be easily reproduced synthetically and are relevant for energy applications, such as the high aspect ratio M13 bacteriophage and the coil-shaped spirulina algae. These microorganisms can further be assembled into tridimensional porous networks and thin films. Via sol-gel syntheses, metal oxide nanoparticles are nucleated onto the surface of the microorganisms to produce nanowires, nanonetworks, microsprings and other rationally-designed composite nanostructures. Natural and abundant sources of silica, like frustules of diatoms, can also be used as starting nanostructured silica material.
After burning off the organic biotemplates, a magnesiothermal reduction process is used to reduce the metal oxide structures to metals, while preserving their shape. The process thus allows us to capture shapes constructed via self-assembly prior to reduction, controllably generating metallic nanoscale features. These novel metallic materials find applications in devices such as thin film photovoltaic devices and lithium-ion batteries.

The chiton radula is a ribbon-like rasping tongue with many rows of extremely hard, wear resistant, and self-sharpening teeth that are designed to withstand the stresses of grazing on rocky substrates.¹ These remarkable properties result from the incorporation of nanocrystalline magnetite (Fe₃O₄) in a nanofibrous chitin scaffold of surprising chemical and structural complexity.² However, magnetite is not formed directly from solution. Instead, mineralization of the scaffold commences with formation of metastable ferrihydrite (Fh) nanoparticles. Fh transforms into magnetite only in a second step, presumably by a reductive transformation. Obviously, the chiton has mastered the structural polymorphism of iron oxides and their complex chemistry, which has been difficult to reproduce in the laboratory, particularly under mild conditions. Controlling and understanding the mechanisms governing phase transformations of iron oxides and in particular Fh, is also of great importance for a broad range of nanomaterials synthesis for industrial applications, environmental science, and geology. Using a combination of X-ray absorption and electron paramagnetic resonance spectroscopy we show that, prior to Fh formation in the chiton tooth, iron ions are complexed by the organic matrix. In vitro experiments demonstrate that such complexes facilitate the formation of Fh under physiological conditions. These results indicate that acidic molecules may be integral to controlling Fh formation in the chiton tooth. This biological approach to polymorph selection is not limited to specialized proteins and can be expropriated using simple chemistry.
[1] Weaver, J. C., Wang, Q., Miserez, A., Tantuccio, A., Stromberg, R., Bozhilov, K. N., Maxwell, P., Nay, R., Heier, S. T., DiMasi, E., Kisailus, D., Materials Today 2010, 13, 42-52. "Analysis of an ultra hard magnetic biomineral in chiton radular teeth."
[2] Gordon, L. M., Joester, D., Nature 2011, 469, 194-197. "Nanoscale chemical tomography of buried organic-inorganic interfaces in the chiton tooth."

Magnetite (Fe₃O₄) is a widespread magnetic iron oxide encountered in both geological and biomineralizing systems. As it is the most magnetic naturally occurring material, it has many technological applications, e.g. in ferrofluids, inks and as contrast agents in magnetic resonance imaging. As its magnetic properties depend largely on the size and shape of the crystals, control over crystal morphology is an important aspect in the application of magnetite nanoparticles, both in biology and synthetic systems. Indeed, in nature organisms such as magnetotactic bacteria demonstrate a precise control over the magnetite crystal morphology, resulting in uniform and monodisperse nanoparticles. Synthetic strategies to magnetite with controlled size and shape exist, but involve high temperatures and rather harsh chemical conditions. In contrast, aqueous synthesis at room temperature generally yields poor control over the morphology and the magnetic properties of the obtained crystals.
It was recently demonstrated that careful control over the reaction kinetics allows the self-similar growth of magnetite nanocrystals[1]. Now we fine tune reaction conditions to achieve polymer-directed biomimetic control over the size and shape of magnetite crystals but also over their organization in solution as well as their magnetic properties. We employ amino acids-based polymers to direct the formation of magnetite in aqueous media at room temperature via both the co-precipitation and the partial oxidation method. By using 2D and 3D (cryo)TEM we shown that it is the net charge of the polymers that determines their activity in nucleation and growth. By changing the composition of the polymers we can tune the morphology, the dispersibility as well as the magnetic properties of these nanoparticles.

Breast cancer preferentially metastasizes to bone and induces pathological remodeling. Although the exact mechanisms of this process remain unclear, there has been evidence suggesting that the nanoscale properties of the bone mineral may play an important role in breast cancer metastasis. Hydroxyapatite (HAP, Ca₁₀(PO₄)₆(OH)₂) is a calcium phosphate mineral whose structural and mechanical properties are closely related to bone apatite properties. In this study we seek to understand whether HAP materials properties alter the mineral/organic interface in bone, in particular, the deposition and conformation of adsorbed fibronectin (FN), a major extracellular matrix protein. We have first synthesized HAP nanoparticles with controlled materials properties through a wet precipitation reaction followed by hydrothermal aging to investigate FN deposition and conformation as a function of size, shape and crystallinity of HAP nanoparticles. Powder x-ray diffraction (pXRD) was then used to determine particle phase and size (Scherrer analysis). Fourier Transform Infrared Spectroscopy (FTIR) was used to assess the crystallinity of the particles. The size and shape of the HAP nanoparticles were determined by Transmission Electron Microscopy (TEM). Zeta potential of nanoparticles in phosphate buffered saline was measured using Laser Doppler Electrophoresis (LDE). Finally, we have mixed varying ratios of HAP nanoparticles and FN together and analyzed FN conformation via F#1255;ster Resonance Energy Transfer (FRET), while varying specific properties of HAP, such as size, shape and crystallinity. Our FRET analysis revealed that more FN adsorbed in a more compact conformation on HAP nanoparticles that had a smaller size, plate-like shape, lower crystallinity and more negative zeta potential. Furthermore, FN adsorption was enhanced and conformation became more compact with increasing HAP concentration, probably due to changes in morphology of nanoparticle aggregates. Collectively, these results have important implications in our understanding of both breast cancer bone metastasis and hydroxyapatite-related inflammation.

Orthopedic surgeries are extremely common in the United States, with over a million occurring annually to replace load bearing regions suffering from degeneration with implant materials. These implant procedures, such as hip, knee, and tooth replacement, have high initial success rates. However, 10% of these implants fail within 15 years, costing the healthcare industry $10B per year for revision surgeries. The leading cause of implant failure is loosening due to poor osseointegration. To address this need, we have developed a protein-engineered biomaterial to be used as a functional implant coating. Our recombinant protein contains two domains: a structural elastin-like sequence and the cell-adhesive RGD domain derived from fibronectin. This bioactive, cytocompatible coating is used to promote cell adhesion at the implant interface and enhance mineralization. We hypothesize this will lead to improved osseointegration and fewer incidents of premature implant failure.
Our elastin-like protein (ELP) was functionalized with a photoactive crosslinker through site-specific conjugation. Our photoactive ELP is processable by a variety of methods, including spin and dip coating, drop casting, soft lithography patterning, and 3D bulk mold casting, allowing it to be applied to numerous implant geometries prior to immobilization upon UV light exposure. Inclusion of the bioactive RGD domain elicited sequence-specific adhesion of 91% of MG-63 osteoblast-like cells and 90% of primary human mesenchymal stem cells (hMSCs) compared to 38% of MG-63s and 77% of MSCs on non-adhesive, control ELP films after 24 hours in full-serum studies. MG-63s on the bioactive ELP produced 60% more mineralization than cells on non-adhesive ELP after 18 days in a calcium-supplemented medium, demonstrating the ability to produce new mineralization directly on the coated surface.
ELP coatings on Ti6Al4V, a common orthopedic implant material, demonstrated long-term stability over the course of 21 days in buffer. MG-63s maintained their viability on ELP-coated Ti6Al4V substrates and showed improved adhesion compared to uncoated Ti6Al4V substrates. Furthermore, the cells produced 80% more mineralization after one week versus cells on uncoated Ti6Al4V.
For in vivo testing, commercially pure Ti dental screws were coated with either the cell-adhesive ELP or the non-adhesive ELP. The coated screws were implanted into a rat femur model along with uncoated dental screw controls. Removal torque measurements were taken post-surgery, with the ELP-coated screws requiring higher torque for removal after 1 week. Current work is focused on the delivery of antimicrobial peptides from the ELP coating to confer local resistance to infection, which is the second leading cause of premature implant failure. By combining our ability to improve mineral deposition directly on the implant surface and provide defense against local infection, we hope to greatly reduce the failure rate of orthopedic implants.

We present a new, 3D-printable material system, Hyperelastic Bone (HB), comprised of 90 wt.% hydroxyapatite (HA) ceramic particles and 10 wt.% biocompatible elastomer. Unlike other high HA-content biomaterials, which are brittle, require high temperature processing, and have limited bioactivity, HB is hyperelastic, and can be quickly fabricated at room temperatures into complex, implantable structures using an extrusion-based 3D-printing system. Structures as small as 1 mm³ or as large as many cm³ can be fabricated with ease and manipulated post printing via rolling, folding, cutting, or fusing with other HB parts. The constructs can be cyclically compressed at least up to 55% and return to their net original form after unloading. These properties are due to the presence of the elastomer along with a characteristic porous microstructure resulting from the specific ink formulation and 3D printing process, The microstructure not only permits rigid HA particles to translate upon mechanical loading and return to their original position upon unloading, but it also presents a composition and nano- and micro-porosity biomimetic of natural osseus tissues. The mechanisms that enable such a high content ceramic construct to be 3D-printed via room-temperature extrusion as well as those responsible for the hyperelastic mechanical properties will be discussed along with the surface properties of the 3D-printed HB. In vitro studies using human mesenchymal and adipose derived stem cells reveal that HB is highly supportive of cell viability and function. Seeded stem cells readily proliferate to quickly coat all available surfaces and fill the inter-scaffold pore volume. HB is also inherently osteoinductive, promoting osteogenic differentiation of stem cells, including extracellular matrix (ECM) deposition and de novo mineralization without the need for additional osteogenic chemical or mechanical factors. Histological and electron microscopy imaging of subcutaneously implanted HB scaffolds in a mouse model, compared to hot-melt 3D-printed HA-polymer scaffolds, reveal that host tissue more readily integrates within and vascularizes throughout the HB scaffolds. Additional results from a variety of functional in vivo studies, including a spinal fusion model will also be discussed. 3D-printed hyperelastic bone&’s unique mechanical and biological properties, combined with the ease of fabrication, potential for scalability, and low material and processing costs make this material system a promising candidate for orthopaedic, dental, and cranial-facial tissue regeneration applications. Its unique microstructure enabled through the 3D-printing process also opens the door for the creation and study of new 3D-printable material systems with unique physical, chemical, biological, and mechanical properties.

Crystals in nature often demonstrate curved morphologies rather than classical faceted surfaces. Inspired by biogenic curved single crystals, we demonstrate that gold single crystals exhibiting curved surfaces can be grown with no need of any fabrication steps¹. These gold crystals grow from the confined volume of a droplet of a eutectic composition melt. We can control their curvature by controlling the environment in which the process is carried out, including several parameters, such as the contact angle of the drops on the specific substrate, and the surface tension of the liquid drop during crystal growth. We will present an energetic model that explains this phenomenon and predicts why and under what conditions crystals will be forced to grow with the curvature of the micro-droplet even though the energetic state of a curved single crystal is very high.
¹ Koifman-Khristosov M, Kabalah-Amitai L, Burghammer M, Katsman A, Pokroy B. ACS Nano 2014 8 (5), 4747-4753.

Supramolecular self-assembly of materials is an exciting strategy to design soft materials with functions that benefit from the molecular versatility of organic matter. Such functional systems can utilize small molecules, polymers, or hybrid compositions that contain inorganic structures. This lecture will first describe supramolecular systems that emulate the biological photosynthetic machinery to generate solar fuels. These systems co-localize light harvesting structures with catalysts in highly hydrated environments emulating some aspects of the internal architecture of choloroplasts. In a second energy relevant example templated hybrid materials using supramolecular structures will be described which exhibit supercapacitor function. The third system to be discussed is relevant to regenerative medicine and shows how Watson-Crick pairing of peptide-DNA hybrids promotes the differentiation of neural stem cells into neurons as a result of supramolecular shape and specific biological signals.

The bio-inspired approach of growing crystals in hydrogels is not easily translated to oxide compounds due to the ease with which bio-polymer hydrogels melt at the temperatures required to form oxides under hydrothermal conditions. By moving to an inorganic hydrogel system based on silica, we have successfully formed hematite (α-Fe₂O₃) by a matrix-mediated, bio-inspired approach with FeCl₃ as a precursor at 100 0C. By Scherrer analysis of powder X-ray diffraction (pXRD) patterns, we find that the sphere-like hematite particles (d~3 µm) formed in this way are composed of coherent crystalline domains that are an average of 181±57 Å in length. Using transmission electron microscopy (TEM) and selected-area electron diffraction (SAED) on thin sections of the sphere-like mosaic crystals, we find that adjacent coherent domains have a high degree of registry, causing the hematite lattice to exhibit a net orientation with respect to the sphere-like particles. Polar transformation analysis of SAED patterns was used to quantify the mosaic internal structure to be in the small angle tilt range (<150). As compared to the more commonly formed hematite pseudocubes in solution, the hydrogel-grown hematite spheres contain lower mosaic spreads, and higher aspect ratio coherent domains, that are elongated along [hk0] directions. The presence of silica in the hematite spheres was studied by Rietveld refinements to powder X-ray diffraction patterns. The expansion of the hematite lattice along the c-axis in the hydrogel-grown samples is consistent with silica as a tetrahedral occupant in the vacant interstices of the hematite lattice. We hypothesize that suppression of growth of the coherent domain along [001] is a consequence of increased lattice strain in this direction due to silicon interstitials. These lattice-level implications propagate to the whole particle level, such that the net orientation of the c-axis within the sphere-like particles is along the shortest direction of the sphere. We have demonstrated in this work that growth of oxides in hydrogels is a viable method to achieve control over the atomic, nano- and microscale structure of hierarchical crystals with potential applications in catalysis and energy technologies.

Lipid membrane vesicles are organelles used by cells for many functions, including the mineralization of hard tissues. At their most fundamental, vesicles establish a privileged environment in which chemical and precipitation reaction conditions can be regulated with high spatial control. Previously, we have shown that synthetic liposomes ranging from 50 nanometers to 50 microns are an excellent platform to study the synthesis of mineral nanoparticles in confinement.[1,2] The spatial delineation and semi-permeability that liposomes provide make them unique nano- and micro reactors. Recent experiments on the formation of CaCO3 within liposomes will be presented. Some of the limitations of synthetic liposomes will also be discussed, including the inability of most liposome synthesis methods to efficiently encapsulate large species of biological interest like proteins, DNA, and foreign nanoparticles. This greatly reduces their effectiveness as a means to exert control over material synthesis at the nanoscale. To overcome this limitation, microfluidically produced and surfactant stabilized water-in-oil drops were employed as liposome analogues for CaCO3 precipitation. The relative ease of synthesis and high encapsulation efficiency of microfluidically-produced emulsions makes them a powerful system for the study of additives and interfacial interactions in nanomaterials synthesis. Recent work on CaCO3 formation in the presence of additives will be discussed.
1. Tester, Chantel C. et al. Faraday Discussions 159 (2012): 345-356.
2. Tester, Chantel C. et al. Chemical Communications 50.42 (2014): 5619-5622.

The mesocrystal hypothesis has been used extensively to qualify the single crystalline nature of synthetic crystals of unusual morphology, high surface area and nanoparticulate granularity. Peak broadening from X-ray diffraction studies has been attributed to the presence of nano-sized, discreet; yet identically orientated, grains as opposed to a high density of defects. Firstly, we critically evaluate current data obtained from scanning/transmission electron microscopy (SEM/TEM) surface area measurements (BET) and X-ray diffraction (XRD) techniques which have resulted in hallmark evidence for mesocrystals. Secondly, we discuss high-resolution XRD measurements of calcite mesocrystals and the rationalisation of peak broadening as a product of lattice strain as opposed to nanoscale grain size. Thirdly, we discuss electron backscattered X-ray diffraction (ESBD) measurements to identify contrasts between the structure of biogenic and synthetic calcite crystals. Finally, we conclude that microscopic and structural characterisation must be conducted and interpreted with great care.

Abstract not available

The value of mass production of cheap and high-quality oligonucleotides can&’t be overemphasized in the field of synthetic biology, functional genomics, bioengineering nanostructure fabrication and the development of bio-nanotechnology related industry in general. The megaclones on next generation sequencing (NGS) platform have potential to be a rich and cost-effective source of sequence-verified DNAs as a precursor to construct large DNA molecule such as artificial gene circuit or DNA origami nanostructure. However, it is still very challenging to retrieve target clonal DNA from high-density NGS platform. Here, I would like to present an enabling technology called 'Sniper Cloning' that enables the precise mapping of target clone features on NGS platform and rapid retrieval of the target by shooting a small laser pulse on the targeted spot. We developed a ‘diffusion-like local mapping algorithm&’ to precisely map the target clone locations. A custom-made pulse laser opto-mechanical device uses radiation or ablation plasma pressure to transfer the target clones from the microscale NGS substrate to users in a high-throughput and non-contact manner. The use of radiation pressure or ablational plasma pressure to drive the separation via focused light enables us to target very small size of clonal features up to the diffraction limit (~1mu;m), including bead, micro-circuit and even small DNA cluster debris of the substrate itself, so most second-generation sequencing platforms with higher capacity are potentially available for the ‘Sniper Cloning&’ technique whether they involve microstructure(GS series - Roche 454 Life Sciences, Iontorrent - Life technologies) or not(MiSeq, NextSeq, HiSeq, - Illumina). Furthermore, with the help of image processing technique, our optomechanical retrieval system separates individual abnormal cell (tumor cell) from heterogeneous population (cancer tissue) to separate genetic information of single cell. I believe proposed optomechnical retrieval technology not only stimulate the development of synthetic biology and nanostructure fabrication but also provides new ways to investigate heterogeneity of individual tumor cells with a goal of uncovering the molecular mechanism of carcinogenesis, establishing personalized cancer therapy.

Nanotheranostic methods combine therapeutic and diagnostic/monitoring capabilities within individual, highly targeting nanocarriers (also called nanoplatforms). There have been various nanocarriers developed so far for nanotheranostics—namely, polymer conjugates, dendrimers, micelles, liposomes, metallic and other inorganic nanoparticles, carbon nanotubes, and nanoparticles of biodegradable polymers—for sustained, controlled and targeted co-delivery of diagnostic and therapeutic agents for enhanced theranostic benefits with fewer side effects. Properly designed theranostic nanomedicines can achieve wide systemic circulation, evade host defenses and deliver drug and diagnostic agents to targeted sites for diagnosis and treatment at cellular and molecular levels. These therapeutic/diagnostic agents are formulated using versatile, standardized theranostic platforms that can be customized by conjugation to biological ligands for targeting. Nanotheranostics can also enable stimulus-responsive release, synergetic and combination therapy, siRNA co-delivery, multimodal therapies, oral delivery, delivery across the blood-brain barrier, and escape from intracellular autophagy. This talk will highlight our recent progress in applying hyaluronic acid-5β-cholanic acid conjugate (HACA) based nanoformulas to deliver both lipophilic drug molecules and siRNA for the treatment of multidrug resistant tumors. Specifically, the nanoformula is composed of the following: 1) hyaluronan-5β-cholanic acid (HA-CA) nanoparticle which can selectively target tumors not only by passive accumulation in the leaky vasculature of tumor tissues, but also by active binding onto and penetration into cancer cells via receptor-mediated endocytosis after binding to HA receptor, CD44, which is overexpressed on various tumors. 2) A layer of Zn(II)-dipicolylamine (Zn-DPA) complexes, which have high affinity for RNAs via specific interactions between coordinated zinc ions of DPA and anionic phosphates of the RNA on the surface of HA-CA nanoparticle. 3) Calcium phosphate (CaP) coating by in situ mineralization of sequentially added calcium and phosphate ions, secures RNAs under phosphate-rich physiological conditions and facilitates pH-dependent RNA release and endosomal escape. We substantiated the versatility of this delivery system by demonstrating its effective delivery of both chemotherapeutics and MDR-1 siRNA in cultured cells in vitro and tumor targeting after systemic administration.

Plasmonic metal nanoparticles have been attracting enormous attention in recent years, particularly for the strong plasmonic coupling between nanoparticles with very narrow nanogaps. The excitement of localized surface plasmon resonance within hot-spot junctions generates a huge enhancement factor of the surface-enhanced Raman scattering (SERS) signal. However, the fabrication of an ultrasmall nanogap (~1-nm gap) between nanoparticles with high precision and high yield remains a challenge in developing an ultrasensitive and quantitative SERS sensor. Recently, we have developed ~1-nm interior nanogap within gold nanoparticles (AuNP) exhibiting a core-shell structure. This nanogap was mediated by the DNA-modified AuNP core and the surrounding Au shell, and this nanogap produced a strong (enhancement factor >10⁸) and a highly homogeneous SERS signal, particle by particle. The ~1-nm interior nanogap inside these Au-nanobridged nanogap particles (Au-NNPs) was formed by the unusual lateral growth of the Au shell on the surface of DNA-modified AuNP. Interestingly, thiolated-DNA strands immobilized on the surface of core AuNPs play a key role in the formation of this interior nanogap. By introducing various DNA molecules to the core with different sequences (poly A, poly T, poly G and poly C), length, sequence order, and DNA grafting density, we found that different DNA bases and binding features directed the Au-NNP synthesis, and thus controlled the generation of the interior nanogap. DNA sequences near the Au-thiol attachment were especially influential on this nanogap structure, which furthermore influenced the plasmonic coupling and SERS signal enhancement.

A facile and robust method to align one-dimensional (1D) nanoparticles (NPs) in large scale has been developed. Using flow assembly, representative rod-like nanoparticles, including tobacco mosaic virus (TMV), gold nanorods, and bacteriophage M13, have been aligned inside glass tubes by controlling flow rate and substrate surface properties. The properties of 1D NPs, namely rigidity and aspect ratio, play a critical role in the alignment. Furthermore, these hierarchically organized structures can be used to support cell growth and control the cell orientation. C2C12 myoblasts were cultured on surfaces coated with aligned TMV. The topographic features were able to promote myogenic differentiation and guide the myotubes orientation. Moreover, genetically modified TMV mutants with reported cell adhesion sequences aligned in capillaries were able to promote and guide neurite outgrowth in differentiating N2a neuroblastoma cells. Given that this method could be achieved in biodegradable polymer capillaries, it has the potential application in the repair of peripheral nerve injury, as a neural conduit.

The functionality of live tissue includes muscle actuation and neural transduction accomplished by ionic currents through hydrogel-like media and metabolite delivery through embedded vascular “microfluidic” networks. We will discuss the results of studies, aimed at replicating such principles of ionic and fluidic transport into hydrogel-based biomimetic devices. Earlier, we reported a new class of gel diodes with rectifying junction formed by interfacing water-based gels doped with polyelectrolytes of opposite charge and operating on the basis of (counter)ionic conductance. We also showed how water-based gels doped with polyelectrolytes can be used as the core of novel photovoltaic cells. We will discuss how these concepts were recently applied in the making of bioinspired “artificial leaves” with microvascular channel networks embedded in permeable hydrogel, and will illustrate them with experimental and modelling results. They allowed construction of self-regenerating dye sensitized solar cells (Sci. Rep. 2013, 3:2357) and leaf-like photocatalytic hydrogel reactors (J. Mater. Chem. A 2013, 1:11106). Ionic conduction principles can also find applications in novel hydrogel actuators and soft robotic components. We will discuss two strategies for using ionic transport and binding in hydrogel actuators that repeatedly change shape when subjected to electric fields. One is the "ionoprinting" technique that we reported earlier (Nat. Comm. 2013, 4:2257) and that allows directed and reversible gel bending. The other one is hydrogel actuation through electroosmotic ion redistribution (Soft Matter 2014, 10:1337). We will present the ongoing work on biomimetic hydrogel actuation demonstrating new principles with potential applications in soft robotics.

Polyphenols are found in both plant and animal tissues, where they serve a variety of functions including mechanical adhesion, structural support, pigmentation, radiation protection, and chemical defense. In animals, polyphenols are found in the adhesive proteins secreted by sessile marine organisms. In mussels, the adhesive proteins are known to contain high levels of 3,4-dihydroxy-L-alanine (DOPA), an amino acid that is believed to be important in adhesion to substrates. In plants, polyphenolic compounds containing benzenediol (catechol) and/or benzenetriol (gallol) functional groups are widely distributed secondary metabolites with a variety of biochemical and physical functions. Included among these are anti-inflammatory and anti-oxidant properties. Consumption of foods and beverages rich in polyphenols, such as chocolate, tea and wine, are claimed to be beneficial to one&’s health.
This talk will focus on selected biological polyphenols that are rich in catechol or gallol functional groups, which are abundant in and can be extracted from tea, coffee beans, cacao beans and wine. Exploiting their natural interfacial adhesion properties, we have engineered a method to form thin adherent polymerized films on substrates immersed in solutions of natural plant polyphenols. Deposition is facile from an aqueous polyphenol solution onto a variety of solid, porous and nanoparticulate metals, ceramics and polymers. In addition to possessing inherent antibacterial and antioxidant properties, the deposited polyphenol films serve as versatile ‘primers&’ facilitating secondary modifications of the primer coating such as metallization and covalent grafting of biomolecules and synthetic polymers. These coatings can be exploited for a variety of practical applications, including antibacterial, antioxidant and fouling resistant coatings on medical devices, metal deposition, plasmonic tuning and surface functionalization of nanoparticles.

The virus like particle (VLP) derived from bacteriophage P22 presents a unique platform for constructing catalytically functional nanomaterials by directed encapsulation of enzymes into the interior volume of the icosahedral capsid. Enzyme encapsulation has been engineered to be genetically programmed allowing “one pot” biosynthesis and directed self-assembly of desired enzymes within the roughly 60 nm diameter P22 capsid. The resulting nano-reactors comprise multiple copies of the cargo enzymes, densely packaged within the capsid at local concentrations that mimic predicted high intracellular macromolecule concentrations. Using enzymes derived from many different organisms, we have encapsulated multi-enzyme pathways within the P22 capsid through a process of directed self-assembly. The resulting nanoreactors demonstrate the bioengineering of robust and complex coupled catalytic nanomaterials.
The system provides a platform with which to interrogate the effects of crowding on enzyme activity, the importance of catalyst adjacencies, the diffusion of intermediate species between partner catalysts in model synthetic metabolic pathways, and the effects of the capsid as a potential barrier limiting substrate access to the encapsulated enzymes. Aspects of the structure and kinetic behavior of these systems have been elucidated and a diffusion-based model for coupled cascade reactions has been developed.
Using P22 nanoreactors as individual building blocks, with single or multi-enzyme systems encapsulated within them, we can extend the utility of the system towards the fabrication of long-range ordered materials that exhibit complex coupled catalytic behavior.

Several living organisms exhibit impressive moisture-resistant adhesion to a variety of substrata. Artificial adhesives that can achieve the strong wet bonding strength, robustness, and structural and functional complexity of their natural counterparts would have broad applications in both technological and medical fields. Here, we harness biomimetic underwater adhesives by rationally recombining genes encoding two natural adhesive domains via a modular design. This design is based upon the adhesive components of natural living organisms, such as mussel foot proteins (Mfp) from mollusks and functional amyloid adhesives from E. coli (curli). These hybrid proteins are able to self-assemble into hierarchical structures composed of cross β-strand fibrils, with disordered Mfp domains displayed external to the amyloid cores dominated by the CsgA domains, as supported by molecular dynamics simulations. These hybrid nanomaterials are intrinsically fluorescent and exhibit greater underwater adhesion and robustness at higher pHs than Mfps or curli on their own. Furthermore, the co-assembly of two different monomers produces copolymer structures that have greater underwater adhesion than all bio-derived and bio-inspired protein-based underwater adhesives reported thus far. We envision that the design of adhesive biomaterials based on combinatorial and modular assembly of diverse functional domains will find broad applications and provide insights into the mechanisms underlying natural adhesive systems.

The directed self-assembly of nanostructured building blocks, such as nanowires, provides an efficient means for generating mesoscale materials with unique and emergent properties. The ability to precisely orchestrate self-assembly, however, necessitates an understanding of how one can program and regulate a diverse set of interactions among the individual component, enabling the fabrication of complex structures. In the present work, microtubule filaments are used as a model system to study the directed self-assembly of nano-rods into mesoscopic 1D nano-arrays (NAs). Microtubules are formed through the polymerization of alpha/beta tubulin heterodimers into filaments that are ~25 nm diameter and 10s of microns in length. Here, we describe the mesoscopic assembly of microtubules in which individual filaments self-assemble in a “head-to-tail manner” to generate macromolecular NAs with lengths exceeding 200 microns. In our system, the microtubules are conceptualized as anisotropic rigid rods with aspect ratios exceeding 100:1, persistence lengths of 2 mm, linear charge densities of 256 e^- per micron, and electrostatically attractive ends. We establish that the directed self-assembly of these rods involves diffusion-limited interactions among microtubule ends, followed by weak adhesion via electrostatic interactions between a and b tubulin subunits at the opposing ends of the rod. Following head-to-tail adhesion, the junction undergoes dynamic rearrangement and/or addition of tubulin dimers to remove lattice defects/vacancies that exist between the filaments. Lastly, we demonstrate that this direct self-assembly process follows second-order reaction kinetics, and characterize the entropic and enthalpic contributions underlying NA assembly. The knowledge from this model system provides a framework that may be broadly applied to designing and developing a variety of nanoengineered building blocks capable of directed self-assembly into larger, mesoscale materials.
*Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Self-assembling peptides have recently attracted significant interest for the design of hydrogels for a wide range of applications: from tissue engineering to drug delivery. The main challenge is being able to rationally design these peptides so as to engineer their physical properties, in particular mechanical. This requires an in depth understanding of the self-assembling processes at all length scales as the properties of the final materials will not only depend on the intrinsic properties of the fibres themselves but also on how they assemble and ultimately on the properties of the network formed.
β-sheet forming peptides are very attractive for the design of biomaterials in particular hydrogels due to the “simplicity” of the structure formed at the molecular level, the relative robustness of the β-sheet assembly and the ease of functionalisation. We have investigate the self-assembly of a family of b-sheet forming octa-peptides based on the alternation of hydrophobic and hydrophilic residues (Saiani et al., Soft Matter, 5, 193, 2009). Using a range of techniques including FTIR, TEM, AFM, SAXS, SANS and rheometry we have investigate how the primary structure of the peptide affects the fibrillar assembly as well as the topology of the network formed and ultimately the mechanical properties of the resulting hydrogel. We have shown that the promotion of self-consistent heterogeneities within the fibrillar network by promoting the lateral aggregation of the fibres strongly affect the mechanical properties of the hydrogels. This was achieved by either controlling the properties of the surrounding media or by specifically designing the primary structure of the peptide so as to promote fibre aggregation (S Boothroyd et al., Faraday Discussions, 166, 195-207 2013).
The in-depth understanding of the factors affecting the mechanical properties of these materials has allowed us to design hydrogels with tailored mechanical properties that we have used in a range of application including as 3D-scaffolds for cell culture (Acta Biomat., 9, 4609, 2013), injectables for the delivery of cell and drugs (D Roberts at al. Langmuir, 28, 16196-16206 2012), as well as sprayable muco-adhesive hydrogels for topical drug delivery (C. Tang et al. Int. J. of Pharm., 465, 427, 2014).

Proteins exhibit a wealth of structures and functions that can be harnessed to design novel functional materials. But the same properties that afford proteins such unique characteristics, namely their chemical and physical complexity, make the task of designing materials out of them challenging and computationally expensive. One central approach for the design of protein materials (Which can be frequently observed in nature) is based on hierarchical assembly of symmetrical structures.^1-2 Integrating this concept with the Rosetta protein engineering software has facilitated accurate, atomic scale, design of 1D and 2D materials.³ Here, we further extend these tools to design multi-component 2D protein materials, dramatically increasing design degrees of freedom, providing control over the assembly process, and potentially providing a route to engineer a wealth of new structures.
The hierarchical design methodology of 2D sheets is based on the crystallographically allowed planar symmetry groups (wallpaper groups), out of which 13 can be constructed by positioning molecules with cyclic symmetry, the simplest of those are the cyclic (C_x) and the dihedral (D_x) homooligomers. Such design focuses on creating a single interface between two monomers, each belonging to a different homooligomers with cyclic symmetry, wherein the designed interface positions the homooligomers with the precise geometry required to yield a higher order symmetric assembly in 2D. The use of two different homooligomers per design (multi-component) and the pool of thousands of natural homooligomers that are currently structurally well characterized, form a huge combinatorial library of potential building blocks/surfaces for design. The design methodology is then comprised of a number of steps that maximizes the potential space of configurations that is covered while at the same time it minimizes personal intervention and computational effort.
The goal of this work is to provide a practical computational tool to design multi-component 2D molecular materials, as those would provide control over the assembly process and potentially overcome issues related to biological production of large assemblies. It harnesses nature&’s variety of structures but is not bound by those and can also accommodate de novo structures, as these are gradually becoming more robust; a number of examples for those are already available. Finally, these 2D soft crystalline structures being prone to design at the atomic level are ideal for design of physically and chemically patterned surfaces, smart membranes, and functional 2D materials.
References
1. King NP, et al. (2014) Accurate design of co-assembling multi-component protein nanomaterials. Nature 510(7503):103-108
2. Lanci CJ, et al. (2012) Computational design of a protein crystal. Proceedings of the National Academy of Sciences
3. King NP, et al. (2012) Computational design of self-assembling protein nanomaterials with atomic level accuracy. in Science

The efficient separation and purification of (bio)molecules from mixture fluids are important for a variety of purposes ranging from target characterization in (bio)chemistry to environmental analysis and biomedical diagnostics. Inspired by biological processes that efficiently and seamlessly synchronize transport and localization of biomolecules from one compartment in the body to another through hierarchical sense-and-response structures, we integrated chemo-mechanical, responsive structures and chemistries into a robust dynamic system demonstrating concerted catch and release of biomolecule targets from a solution mixture. By synchronizing the chemical responsiveness of structurally configurable aptamers and volume changing hydrogels in a biphasic microfluidic regime, we show effective biomolecule catch and release with 95% sorting efficiency upon multiple solution recycling. The novel chemo-mechanically modulated reusable platform employing “smart”, responsive hydrogel shows advantages over conventional complex, costly separation methods on the non-destructive, energy efficient, programmable sequential separation and purification, with great potential for numerous bio(medical) and environmental applications.

Growing evidence supports a critical role of metal-coordination in soft biological material properties such as self-healing, underwater adhesion and autonomous wound plugging. Using bio-inspired metal-coordinating polymers, initial efforts to mimic these properties have shown promise. In addition, with polymer network mechanics dictated by coordinate crosslink dynamics, material properties can be easily tuned from visco-elastic fluids to elastic solids. Given their exploitation in desirable material applications in nature, metal-coordinate crosslinking provides an opportunity to advance synthetic polymer materials design. Early lessons from this pursuit are presented.

In nature, proteins guide the formation of hierarchically-ordered, lightweight, inorganic-organic composites such as corals, seashells, and bones. M13 phage is a bacteria-infecting virus that has a rigid, nanoscale rod-like morphology. Liquid-crystalline monolayers of genetically engineered phage have been used to template crystallization of thin layers of inorganic and metallic materials. Thin films of M13 phage therefore represent a potential material for mimicking natural processes in composite synthesis. We have created thin films composed of engineered M13 phage capable of binding different inorganic components (hydroxyapatite, silica, or calcium carbonate). We employed both a dip-cast and a drop-cast film fabrication method on both smooth and rough gold, silica and glass casting surfaces to create thin films and 3D structures of various degrees of hierarchical order. We have found the engineered M13 phage and the inorganic mineral significantly affected both film morphology and the mechanical properties of the film. Similarly, film fabrication parameters such as solution chemistry, temperature, and pulling speed affected film properties. Using a calcium phosphate biomineralized 4E phage, film thickness increased linearly with the number of layers/dips in the phage solution. The strength of these composites (Young's modulus) were >80 gPa for both single and multilayer films. These materials are an order of magnitude stronger than the biological equivalent collagen. Strength, however, does not appear to increase in a multilayer film compared to a single layer. Ultimately, we have developed a platform for phage-based bio-composites for developing high performance materials.

Cephalopods are known for their remarkable camouflage abilities. They can modify their skin&’s coloration, texture, pattern, and reflectivity to blend into the surrounding environment. We have drawn inspiration from nanostructures found in cephalopod skin to fabricate dynamically tunable biomimetic camouflage coatings on transparent and flexible substrates. Our substrates can adhere to arbitrary surfaces, and we can reversibly modulate their reflectance from the visible to the near infrared regions of the electromagnetic spectrum. Thus, common objects can be endowed with tunable camouflage capabilities. Our work represents a first step towards a disposable, dynamically reconfigurable infrared stealth technology.¹
[1] L. Phan, W.G. Walkup IV, D. D. Ordinario, E. Karshalev, J-M. Jocson, A. M. Burke, A. A. Gorodetsky. Reconfigurable Infrared Camouflage Coatings from a Cephalopod Protein. Adv. Mater.201325, 5621.

Artificial protein hydrogels have attracted interest as reinforcing tissue fillers, matrices for cell-instructive regeneration, and delivery platforms for cellular or molecular cargo. Engineering the mechanical performance of these gels to meet the variety of complex processing constraints of the clinic, such as minimally-invasive delivery and resistance to mechanical degradation post-implantation, is an ongoing challenge. Through the genetic engineering and biosynthesis of telechelic proteins and modular protein block copolymers, we are able to responsively control the molecular and nanoscale structure of artificial protein hydrogels. By synthesizing genetic fusions of elastin-like polypeptides (ELPs), self-associating α-helices, and soluble linker sequences, we have prepared hydrogels that thermoresponsively self-assemble into nanostructured materials consisting of close-packed spherical or cylindrical micelles with associative coronae. This approach produces hydrated biomaterials whose stiffness, yield stress, creep compliance, extensibility, and erosion rate can be improved significantly at physiological temperatures. By changing the primary sequence of the ELP endblocks, while holding all other parameters constant, ABA and ABC block copolymer hydrogels can be prepared with nearly a three-fold difference in stiffness and large changes in their longest stress relaxation time. In addition, we have produced thermoresponsive ELP-based hydrogels that are thin liquids at low temperatures, and assemble into gels with shear elastic moduli greater than 1 MPa at 37 ^oC at 20% (w/w). These ELPs can be chain-extended via reversible coupling of terminal cysteine residues, leading to oxidatively-responsive increases in gel extensibility and overall toughness. Finally, we have investigated cell morphology, proliferation, and differentiation on these biofunctionalized protein gels. Fine structural control, achieved through precision biosynthesis and protein self-assembly, enable the responsive toughening of these hydrogels suitable for a number of applications including fillers and scaffolds for the engineering of stiff tissues.