The dipeptide of phenylalanine, diphenylalanine (FF), is well known to spontaneously self-assemble into remarkably stable nanotubes when exposed to aqueous environments. We have demonstrated that the modification of FF with boronic acid functionalities can induce dramatic transformations in the self-assembly behavior of this simple peptide. For example, the introduction of a phenylboronic acid moiety onto the N-terminus of FF via simple amide bond formation yields a modified dipeptide that self-assembles into striking, planar nanostructures in water. These nanostructures are crystalline and highly regular in appearance, and are unmistakably distinct from the nanotubes formed by the unmodified FF prepared under identical conditions. The introduction of a boronic acid functionality also provides a synthetic handle for further modification of dipeptides through the formation of boronate esters. The reversible reaction of di-hydroxyl and poly-hydroxyl compounds - in particular saccharides - with boronic acids to form cyclic boronate esters is a universally recognized area of boron chemistry, and it has been exploited for a number of applications, such as saccharide sensing. We have further modified boronic acid-functionalized dipeptides by reaction with a suite of hydroxylated compounds, such as pinacol and fructose. The implications of these reactions on the self-assembly behavior of the peptides will be described and supported by a battery of spectroscopic and microscopic characterization techniques. Our results validate a novel strategy by which the formation of complex, yet precise, nanostructures can be controlled by simple modifications of peptide building blocks.
Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the US Department of Energy&’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

MAX1 is a 20 amino acid peptide that under an exogenous stimulus folds into a beta-hairpin conformation and undergoes rapid self-assembly into a highly crosslinked hydrogel network. Gels formed from MAX1, and its derivatives, are useful in drug delivery and tissue regeneration applications. Subsequent peptide engineering found that truncating the terminal residues of MAX1 afforded a peptide, named SVS-1, which no longer undergoes hydrogelation, but instead selectively binds to, and kills, cancer cells. At high concentrations, SVS-1 binds to the lipid bilayer of cancer cells and folds into a bioactive confirmation capable of disrupting the lipid membrane leading to cell lysis. We find at lower sub-toxic concentrations, although the peptide is unable to kill cancer cells, it acts a potent cell penetrating peptide (CPP) with preferential targeting towards cancer cells. Consequently, this CPP activity allows SVS-1 to serve as an effective drug delivery platform capable of solubilizing hydrophobic drugs and preferentially transporting them into cancer cells. Biophysical studies employing a fluorescently-labeled SVS-1 analog show that the peptide rapidly enters cells via physical translocation across the lipid membrane, and demonstrates that uptake of this peptide occurs preferentially in cancerous cells over non-cancerous phenotypes. To determine its utility in chemotherapeutic delivery, we conjugated the model hydrophobic drug Paclitaxel (PTX) to SVS-1 through a self-immolative disulfide linker designed to be reduced by intracellular glutathione and release the free chemotherapeutic. Conjugation of PTX to the SVS-1 carrier improved drug solubility by nearly 1000 times, and allowed for selective release of the chemotherapeutic in the presence of physiologically relevant glutathione concentrations. In vitro cytotoxicity studies confirmed PTX retained its anticancer potency when conjugated to, and released from, the SVS-1 carrier. In vivo, SVS-1 was found to preferentially localize to tumor tissue in a lung cancer mouse model and deliver PTX, resulting in reduced tumor growth. Moreover, the high solubility of the peptide allowed PTX-SVS-1 conjugates to be administered to mice without the need of toxic solubilizing vehicles commonly required for clinical administration of PTX. These results highlight the broad utility of self-assembling peptides, from monomers in material design to cell-penetrating delivery platforms with potential as anti-cancer therapeutics.

Self-assembled peptides and proteins have received increasing attention in biomedical applications such as cell delivery, tissue engineering, and regenerative medicine. We have found in the past few years that self-assembled peptides are also uniquely immunoreactive, and here we will describe recent studies characterizing the interactions that this class of materials makes with the immune system. Understanding aspects that influence the strength and phenotype of the immune responses raised by these materials will be critical for their translation in vivo, both in “non-immunological” applications such as tissue engineering and in classically immunological applications such as vaccines.
β-sheet fibrillizing peptides can raise strong antibody responses without the addition of supplemental adjuvants, but they do not always elicit a vigorous response. In previous work, we found that peptide fibrillization was essential to this antibody response, as mutated peptides lacking the ability to assemble into nanofibers did not raise responses. Here we will discuss findings that epitope content plays a major role in not only the strength but also the phenotype of the immune response that is raised in mice by β-sheet fibrillized peptides. Using co-assembling peptides that contain either B cell/antibody epitopes or CD4+ T cell epitopes, we found that co-assembly of the two together into integrated nanofibers was critical for strong antibody production. This finding was replicated in two different systems, one using a B cell epitope from methicillin-resistant S. aureus (MRSA) and another using a B cell epitope from TNF-α. Interestingly, as the CD4+ T cell epitope was titrated into the nanofibers, in both systems antibody responses increased to a maximum, then diminished as the T cell epitope content was increased further. Additionally, using flow cytometry and ELISPOT, we found that subtle changes between the ratios of the B cell and T cell epitopes modulated the phenotype of the T cell response, with different epitope ratios favoring Tfh, Th1, and Th2 T cells. In concert with this titratable response, we also observed that the materials were minimally inflammatory, and that they were capable of activating dendritic cells (DCs) in intraperitoneal injections to a much greater degree than macrophages. This targeted engagement of specific antigen-presenting cells contrasts with other particulate adjuvants such as alum, which has a much broader and more inflammatory effect on both DCs and macrophages. Together, these results provide insight for avoiding immune responses to peptide nanofibers, augmenting them, or adjusting them towards specific immune phenotypes.

The need for rational design of effective vaccines against pathogenic infections has been alarmingly increased recently. Rationally designed vaccines, which are safer than conventional vaccines, are generally disadvantaged in terms of immunogenicity. Pathogen-associated molecular patterns (PAMPs), such as CpG motifs in viral/bacterial DNA, have been studied extensively and found to enhance antigen-specific immune response. On the other hand physical patterns of pathogens, which determines the context PAMPs act in nature, have been underemphasized in vaccine design. In this study, we asked how immune system behaves against CpG motifs in the context of two common viral shapes - sphere and fiber. In order to design these shapes, we used self-assembling peptide amphiphiles with varying backbone according to purpose. Immunostimulatory CpG ODNs were mixed with either nanosphere-forming or nanofiber-forming peptide molecules. Cytokine assays indicated that nanofibrous ODNs direct immune response towards Th1 phenoctype stronger than nanospherical and bare ODNs. Surface marker expressions also shifted with whether ODNs delivered alone, bound to spheres or fibers. All these were correlated with differential uptake of nanofibers into dendritic cells. Moreover, both type of nanostructures protected ODNs from enzymatic degradation significantly. In vivo studies indicated that nanofiber-ODN complexes induced more than 10-fold antigen-specific IgG production than naked ODN. All these findings support the nanofiber-ODN system as a potent vaccine formulation.

Peptide-based hydrogels have emerged as potential biomaterials of versatile biomedical and biotechnological applications ranging from tissue engineering and 3D cell culture to drug delivery, thanks to the ease of functionalization, versatility of design, biocompatibility and non-immunogenicity of peptides. In essence, peptide hydrogels are formed through the self-assembly of short “bottom-up” designed peptide sequences to form higher fibrillar/supramolecular structures that above critical gelation concentration (CGC) entangle into a 3D network forming a gel. The molecular self-assembly of peptide-forming hydrogels has involved the formation of various secondary structures including #593;-helix, coiled-coil, β-sheet and β-hairpin depending on the primary sequence design (Dasgupta, A. et al.; RSC Adv. 3: 9117-9149, 2013). The self-assembly of these secondary structures is driven mainly by the non-covalent electrostatic, hydrophobic and/or van der Waal&’s interactions in response to external triggers such as pH, ionic strength, temperature, light or enzymatic-trigger.
In our group, we have long standing efforts in developing a platform for the design of such peptide hydrogels through the exploitation of the self-assembly of the so-called β-sheet forming peptide (Boothroyd, A. et al.; Biopolymers. 106: 669-680, 2014). These hydrogels are stable, biocompatible, biodegradable, sprayable (Tang, C. et al.; Int. J. of Pharm. 465: 427-435, 2014) and injectable (Robert, D. et al.; Langmuir, 28: 16196-16206, 2012) with the ability to recover stiffness after the shear stress of injection. These attributes make those hydrogels potential candidates for use as biocompatible vehicles in drug delivery systems. In this talk, we will report on our recent efforts in designing stimuli-responsive β-sheet forming peptide hydrogels functionalised with protease-activatable pro-drug molecules as a drug delivery system for the controlled targeted release of drugs in various disease models with particular emphasis on cancer. This work also involves various approaches for the engineered conjugation of drugs to peptide hydrogels.
In summary, we will introduce a novel rationally designed β-sheet peptide hydrogel-drug conjugates as a biocompatible and selectively controlled drug release system.

The unique functional properties of proteins have motivated scientists to explore their use, or alternatively mimicking their behavior, in diverse technological applications. Postulating that these unique properties can be preserved even in very short sequences, our group has been aiming using short b-sheet forming peptides to develop novel electronic devices and sensors.
In this talk I will present two distinct examples for the biomimetic approach we undertake. I will present a novel peptide design that embeds a small molecule recognition unit within a b-sheet peptide. Sensitization of nanopores that are prepared in silicon nitride membranes with these b-sheet forming receptor peptides enables the detection of small analytes at the single molecule level.¹ In the second example I will demonstrate the use of peptides derived from the core sequence of b-amyloid peptides for the construction of fibril networks that promote electric conduction. I will show that the conduction in the networks depends both on fibril morphology and on peptide side chains.² Our results demonstrate the great potential of the use of peptides in bioelectronic and sensing applications.
¹ Y. Liebes-Peer, H. Rapaport, and N. Ashkenasy, "Amplification of Single Molecule Translocation Signal Using β-Strand Peptide Functionalized Nanopores", ACS Nano8, 6822 (2014)
² M. Amit, G. Cheng, I. W. Hamley, and N. Ashkenasy, "Conductance of amyloid β based peptide filaments: Structure-function relations". Soft Matter, 8, 8690, (2012).

We show that an amino acid functionalised perylene bisimide (PBI) forms self-assembled structures for the use in photoconductive applications. PBIs are promising materials for the use as n-type materials in organic photovoltaic devices (OPVs) as well as for use in field-effect transistors and organic electronic devices. Their suitability as n-type materials in such devices stems from their absorption, emission and conductivity properties. This conductivity is due to the formation of a radical anion that can be created by using energy from photons of light. π-stacking is important as it influences morphology of PBI aggregates and therefore the electronic pathways of the free electron. The use of gelation offers a controlled route towards well-defined nano- and micro-structures in the aggregates formed. The conductivity and absorption spectra of such materials can be altered by changing morphologies but also by the use additives. Here, we demonstrate that an amino acid based PBI gelator forms self-assembled structures at both high and low pH and shows photoconductive behavior when dried into thin films. This photoconductivity is unusually stable in air for many hours. The thin film&’s properties can be altered by the use of additives in the gelation process giving the potential to tune the photoconductivity.

The self-assembly of organic semiconductors via short peptide sequences has gained a lot of interest in recent years, as extensive organization of the semiconducting material in thin films is crucial for the performance of these materials in organic electronics, such as organic solar cells, organic field-effect transistors and sensors.¹ The multiple hydrogen bonding between the individual peptide sequences influences the orientation and packing of the π-conjugated material resulting for example in antiparallel pleated β-sheets, β-turns, α-helixes, and other structures. The alanyl glycinyl (AG) sequence is known to be the most important repeat sequence in forming β-sheets, forming a silk-like fibroin with hydrogen bonding between the peptides.² For our initial studies towards the self-assembly behaviour of semi-conducting materials, we chose to focus on a simple GAGAG pentapeptide sequence, derived from Bombyx mori silk, a natural product made by silkworms that are the larvae of the domesticated silkmoth.³
In this contribution we present the synthesis of a novel 4,4&’-bis(4-n-hexylphenyl)-2,2&’-bithiophene (PTTP) peptide construct. Using standard peptide coupling conditions we conjugated the N-terminus of the pentapeptide to the carboxylic acid end of a conjugated mesogen, PTTP. The construct rapidly self-assembles in thin films deposited from solution. Atomic force microscopy (AFM) was used to explore the self-assembled morphologies adopted by the material and examined the influence of different solvents, substrates, and fabrication procedures on the formation of the assembled structures. FT-IR spectroscopy clearly showed the formation of an antiparallel pleated β-sheet. Organic field-effect transistors were successfully fabricated and showed state of the art performance for this material using extremely low amounts of material. AFM images recorded in the channel of working transistor devices show a fibrous mat crossing the channel and confirmed that the charge transport is mediated by the self assembly of the semi-conductor peptide conjugate.
[1] a) Sirringhaus, H.; Brown, P. J.; Friend, R. H.; Nielsen, M. M.; Bechgaard, K.; Langeveld-Voss, B. M. W.; Spiering, A. J. H.; Janssen, R. A. J.; Meijer, E. W.; Herwig, P.; de Leeuw, D. M. Nature1999, 401, 685minus;688. b) Hoofmann, R. J. O. M.; de Haas, M. P.; Siebbeles, L. D. A.; Warman, J. M. Nature1998, 392, 54minus;56.
[2] Marsh, R. E.; Corey, R. E.; Pauling, L. Biochim. Biophys. Acta1955, 16(1), 1-34.
[3] Calvert, P. Nature1998, 393, 309-311.

The development of highly functional, tailored soft materials is arguably one of the most important challenges of material science for the next decade. Self-assembling peptides have been highlighted as one of the most promising building blocks for future material design where individual molecules are held together via strong, yet irreversible bonds, imparting strength to the material. Peptides offer a number of advantages to the material scientists. The library of 20 natural amino acids offers the ability to play with the intrinsic properties of the peptide such as structure, hydrophobicity, charge and functionality allowing the design of materials with a wide range of properties. Synthetic peptides are chemically fully defined and easy to purify through standard processes. Being build form natural amino acids they result usually in low toxicity and low immune response when used in-vivo and can be degraded and metabolised by the body. The translation of these soft materials into commercial applications is starting to become a reality with the advent of routine procedures for peptide synthesis and purification in both the lab and industrial scale, thus making them easily accessible at a reasonable cost.
Over the past 10 years our group has focused on the development of a technological platform for the design of novel bio-functional materials, in particular hydrogels, exploiting the self-assembly of β-sheet forming peptides. The β-sheet motif is of particular interest as short peptides can be designed to form β-sheet rich fibers that entangle and consequently form hydrogels. These hydrogels can be functionalized using specific biological signals and can also be made responsive through the use of enzymatic catalysis and/or conjugation with responsive polymers. Through the fundamental understanding of the self-assembly of these peptides we have been able to design hydrogels with tailored properties for a range of applications including 3D scaffold for in-vitro stem cell culture and differentiation, injectable systems for in-vivo cell delivery as well as sprayable systems for topical drug delivery. Our most recent work has focused on the development of peptide based biosensors for the early stage detection of cancers and biocatalysis for fine chemical manufacturing.

Chitosan (CHI) is an excellent biomaterial with antibacterial properties. It has been successfully used against both gram-negative and gram-positive bacteria. Different mechanisms of antibacterial action of CHI have been proposed. In the case of gram-negative bacteria, one of the most accepted mechanisms is the leakage of intracellular constituents of the microorganisms caused by the interaction between positively charged amino groups of CHI and negatively charged microbial cell membranes. On the other hand, in the case of gram-positive bacteria, one accepted mechanism is the membrane polymer formation by the interaction of CHI on the cell membranes, which inhibits nutrients from entering the cell. In order to use the CHI for biomedical applications, to enhance its mechanical properties is necessary. One common strategy is to mix CHI with hyaluronan (HA), a soft, highly hydrated, and nontoxic biopolymer. In this work, we proposed to synthetize antibacterial nanofilms of HA/CHI biopolymers assembled by the layer-by-layer (LbL) technique.
The LbL is a simple botttom-up technique to modify surfaces, synthetize nanocomposites and thin films on different materials. This method consists of alternating physisorption of oppositely charged polyelectrolytes. As hyaluronan (HA) and chitosan (CHI) are oppositely charged biopolymers (negative and positive, respectively), they are excellent candidates to be used for surface coatings obtained by this technique. Besides, in order to test the antibacterial effect of HA/CHI nanofilms assembled by LbL, we used both kind of bacteria Pseudomonas aeruginosa (gram-negative) and Staphylococcus aureus (gram-positive), two human pathogenic microorganisms.
The HA/CHI nanofilms were built on Si substrates covered with an initial polyethylenimine layer. The antibacterial effect of HA/CHI nanofilms was evaluated using optical microscopy and counting bacterial growth. These results were correlated with the morphology of nanofilms (characterized using SEM and AFM), as well as with their chemical properties, studied by FTIR, Raman and XPS. The antimicrobial behavior of HA/CHI nanofilms was observed after a minimum number of HA/CHI bilayers was deposited on the surface.

Autonomously generating, renewable, and programmable self-assembling living systems are the next generation of bioinspired advanced materials. Such technologies would integrate synthetic biology and materials science approaches towards reengineering a biomaterial that is both abundant and robust, such as bacterial biofilms. Due to the roles of biofilms in microbial pathogenicity and persistence, the majority of current biofilm research has focused on prevenshy;ting their formation and promoting their disruption, resulting in an overlooked opportunity to develop biofilms as a self-assembling functional material. Herein we present “Biofilm-Integrated Nanofiber Display” (BIND) as a strategy for the programmable functionalization of the E. coli biofilm extracellular matrix by genetically appending various peptide domains to the amyloidogenic protein CsgA, the key biofilm proteinaceous component. We find that these engineered CsgA fusion proteins are successfully secreted by the cellular export machinery and self-assemble into a network of extracellular amyloid nanofibers that displays the peptide of interest in high density. The displayed peptide domains maintain their function and confer various non-natural functions to the biofilms as a whole, including the enhancement of adhesion to specific abiotic surfaces, the biotemplating of nanoparticles, the immobilization of whole proteins throughout the biofilm, or any combination of these functions. Our results suggest that BIND is a novel strategy for the efficient broad functionalization of biofilms via engineered peptide or protein domains. BIND will be a highly versatile nanobiotechnological platform for the development of robust interfacial materials with programmable functions and demonstrates the utility of biofilms as a large-scale designable biomaterial.

In contemporary biotechnology there is a need to develop bioinspired tissues that represent critical features of human organs. Human pluripotent stem cells offer unprecedented potential to develop “organotypic” models for a variety of applications, including drug discovery, toxin screening, and disease modeling. Furthermore, recent studies demonstrate that human pluripotent stem cells may be capable of forming organotypic models via a process we term “biologically driven assembly”, in which cells are encouraged to undergo morphogenesis processes without substantial external control. This talk will describe efforts that use synthetic materials to understand and manipulate the process of human tissue assembly. We will emphasize the use of synthetic materials to promote 3-dimensional stem cell assembly into putative tissues, and to mimic aspects of early tissue morphogenesis. We will also show initial progress toward robust, reproducible, human tissues in a dish for drug discovery and toxin screening. Finally, we will discuss directions that extend from these studies, and progress toward high throughput screening systems based on human tissues in a dish.

Cell transplantation via direct cell injection at the target site is a minimally invasive strategy for treating various injuries and degenerative diseases. However, cell viability is typically only 5% in these procedures, and the therapeutic success critically hinges on the survival and subsequent maintenance of the transplanted cells. To protect these cells, we designed an injectable hydrogel that undergoes two different physical crosslinking mechanisms. The first crosslinking step occurs ex vivo through peptide-based molecular recognition to encapsulate cells within a physical hydrogel. The second crosslinking step occurs in situ through a thermal phase transition to form a reinforcing network. At room temperature, the physical hydrogel is shear-thinning and self-healing to facilitate gentle cell encapsulation and transplantation by syringe injection. At body temperature, the hydrogel forms a secondary network resulting in a 10-fold increase in shear modulus and significantly reduced erosion rates and prolonged retention time. Human adipose-derived stromal cells (hASCs) injected through a 28-gauge syringe needle were significantly protected from disruptive mechanical forces when encapsulated within the hydrogel compared to medium alone. In vivo subcutaneous injection of hASCs in a murine model demonstrated significantly improved cell retention when delivered in a double-network hydrogel compared to a single-network gel or medium alone. These results suggest that in situ formation of a reinforcing network within an already existing hydrogel can enhance mechanical properties and retention time, and thereby improve long-term cell viability. These cell-delivery materials are being further investigated for the ability to support functional tissue regeneration at sites of ischemia.

A remarkable feature of certain biological species is their ability to dramatically alter their shape in response to environmental cues. We focus on photoresponsive polymer gels that contain spirobenzopyran (SP) chromophores. The SP moieties are hydrophilic in the dark in acidic aqueous solutions, but become hydrophobic under illumination with blue light. Hence, with the incorporation of these chromophores into gels, light can be harnessed to control the gel's swelling or shrinking and, thereby, dynamically alter the gel's shape. We recently developed a model for SP-functionalized gels that agrees well with the available experimental data. Herein, we introduce elastic fibers into this model. The introduction of fibers within the gel matrix plays a crucial role in improving the mechanical properties of the matrix, while functionalization of these fibers yields a route to tailoring the functionality of the composite, as well as its optical and electrical properties. We isolate the effects of external stimuli (temperature and light) on gel-fiber interactions and show that variation in the placement of the fibers leads to dramatic changes in the resulting 3D shapes. These composites can be patterned remotely and reversibly by illuminating the samples through photomasks and, thus, molded into a variety of shapes. Furthermore, we show that when the tips of the fibers are extended relatively far from the surface of the hydrogel, the tips motion effectively amplifies small changes in the gel-fiber interactions that are driven by the external stimuli. In addition, by repeatedly rastering the light source over the sample, the system can be driven to exhibit another biomimetic behavior: sustained, directed motion. Our results point to a robust method for controllably reconfiguring the morphology of soft materials, amplifying the effects of external environmental changes (light or temperature) and transferring the signal between the different media, as well as driving the self-organization of multiple reconfigurable pieces into complex architectures.

We present the formulation of coordination materials prepared from Iron(III) and two polyuronic acids: alginate and pectate. These materials are photoactive, showing reduction of Fe(III) to Fe(II) and oxidative decarboxylation of the polysaccharide upon visible light irradiation. The photoreaction also leads to a change in the physical properties of the hydrogel materials, where a gel-sol transition is observed. We report for the first time that the photo-reactivity of these materials depends on the stereochemistry of the building block in the polysaccharide. Polysaccahrides with more Mannuronate were more photoactive than those with guluronate or galactauronate. The observed trend in quantum yields was M-rich alginate>G-rich alginate>Pectate. By combining these photo-responsive polysaccharide systems with other non-reactive polymers, we could create hybrid materials with new mechanical properties that can be tuned upon irradiation. This makes it possible to imprint patterns or gradients of mechanical properties on these substrates. Iron-polyuronates are presented here as a tool for inducing photo-responsive behavior in other hydrophilic polymeric systems. Our work creates guidelines for the formulation of photo-responsive biomaterials, where different aspects, such as the mechanical properties or the photo-reactivity, can be easily tuned.

Future nanoscale soft matter design will be guided to a large extent by the teachings of amphiphile (lipid or surfactant) self-assembly. Ordered nanostructured lyotropic liquid crystalline mesophases, such as lamellar, inverse bicontinuous cubic and inverse hexagonal mesophases, may form in select mixtures of amphiphile and solvent. To reproducibly engineer the low energy amphiphile self-assembly of materials for the future, we must first learn the design principles. Research on the evolution of these design rules will be presented and in particular there will be a discussion of recent key findings regarding (i) what drives amphiphile self-assembly, (ii) what governs the self-assembly structures that are formed, and (iii) how can amphiphile self-assembly materials be used to enhance product formulations, including drug delivery vehicles, medical imaging contrast agents, and integral membrane protein crystallisation media. We will focus upon the generation of 'dilutable' lyotropic liquid crystal mesophases, in other words mesophases (and colloidal particles therefrom) that are thermodynamically stable in excess water, with ordered two- and three-dimensional nanostructured geometries from amphiphilic small molecules.

Polymer vesicles, also coined polymersomes, are among the most attractive systems for drug delivery applications. Actually, vesicles obtained by self-assembly of block copolymers are expected to overcome some of the current limitations in drug delivery, allowing the development of robust nanocontainers of either hydrophilic or hydrophobic species. In addition, the development of macromolecular nanodevices that can be used within the living body implies that sensors detecting chemical signals -such as ions, enzymes or pH changes- and generating internal signals or appropriate responses be integrated in the macromolecular system. The use of peptide and saccharide building blocks in the copolymer structure would allow both controlling the self-assembled structure and the resultant biofunctionality.
We report an overview on the self-assembly in water of amphiphilic block copolymers into polymersomes, and their applications in loading and controlled release of both hydrophilic and hydrophobic molecules and biomolecules. We pay special attention to polysaccharide and polypeptide-based block copolymer vesicles that we have studied these recent years in our group. These newly developed copolymers that mimic the structure and function of glycoproteins represent an example of the effectiveness of a biomimetic strategy in implementing materials design. Exciting and very promising results about their therapeutic evaluation for tumor targeting and in vivo tumor regression studies will be presented.
Finally our recent advances in using “biomimicry approaches” to design complex, compartmentalized materials will be proposed. We demonstrate the formation of compartmentalized polymersomes with an internal “gelly” cavity using an original and versatile emulsion-centrifugation process. Such a system constitutes a first step towards the challenge of structural cell mimicry with both “organelles” and “cytoplasm mimics”. This study constitutes major progress in the field of structural biomimicry and will certainly enable the rise of new, highly interesting properties in the field of high-added value soft matter, especially in controlled cascade (bio)reactions.
¹ C. Bonduelle, S. Lecommandoux. Biomacromolecules 2013, 14, 2976-2983.
² Bonduelle, C. ; Huang, J. ; Ibarboure, E. ; Heise, A. ; Lecommandoux, S. Chem. Commun.2012, 48, 8353.
³ Huang, J. ; Bonduelle, C. ; Thévenot, J.; Lecommandoux, S. ; Heise, A. J. Am. Chem. Soc.2012, 134, 119.
⁴ Upadhyay, KK.; Bhatt, A.N.; Mishra, A.N.; Dwarakanath, B. S.; Jain, S.; Schatz, C.; Le Meins, JF.; Farooque, A.; Chandraiah, G.; Jain, AK.; Misra, AK.; Lecommandoux, S. Biomaterials2010, 31, 2882.
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⁶ Marguet, M. ; Bonduelle, C. ; Lecommandoux, S. Chem. Soc. Rev.2013, 42, 512-529.
⁷ R. J. R. W. Peters, M. Marguet, S. Marais, M. W. Fraaije, J. C. M. Van Hest, S. Lecommandoux. Angew. Chem. Int. Ed.2014, 53, 146-150.

The immobilisation of homogeneous catalysts on supports is a common-place method to increase recoverability. However, the overwhelming majority of work is focused on the design of the catalyst rather than the support. We report that, by considering functionality of the support and incorporating a bioinspired surface barrier containing a light-gated nanovalve, a recoverable and responsive catalysis system can be achieved. By remotely opening and closing the nanovalve, the exposure of the supported catalyst and consequently the catalysis is switched on and off.
The catalyst utilised in this proof-of-concept system is a hydrophilic analogue of Grubb&’s catalyst and is immobilised on spherical mesoporous silica particles. Regulation of the exposure of the catalyst is achieved by a method inspired by a biological cell: a self-assembled lipid bilayer acts as a barrier between the catalyst and the substrate and a reconstituted mutant membrane protein (the mechanosensitive channel of large-conductance (MscL)) acts as a switch by reversibly opening and closing in response to light of different wavelength (365 / 460 nm).
We anticipate that by facile modification of the individual modules (nanovalve, catalyst and barrier), different stimuli can be used to exert similar control on different reactions. Any water-stable silane-containing catalyst can, in principle, be immobilised on the core and by chemical modification of the nanovalve, the switching wavelengths can be tuned. We propose that by combination of multiple different catalasomes one could obtain a programmable system in which numerous reactions can be controlled in a single pot simply by tuning the chronology and frequency of the stimuli.

Polymer coated implants with drug-loading abilities have a high interest for biomedical applications. The control of the retention and release of small hydrophobic compounds as well as structure-dependent biomolecules within these coatings remains a challenge. To this end, we report the use of liposomes embedded in polymer thin films either assembled from interacting polymer layers¹ or made of poly(dopamine)^2-4. The interactions between different cell lines and the composite films were assessed with regards to the capping layer thickness, type of liposomes (e.g. different charge or incorporation of lipophilic dopamine conjugates) and the amount of deposited liposome layers. Cargo from positively charged liposomes was internalized in largest amounts while the lipophilic compound did not have an effect. Deposition of multiple liposome steps led to higher numbers of surface immobilized liposomes and more sustained cargo delivery to adhering cells. By loading the liposomes with a cytotoxic and hydrophobic compound, thiocoraline, we demonstrated the successful delivery of active cargo from the composite film to adhering cells by measuring the cell viability. The uptake mechanism of adhering myoblasts was assessed by loading a fluorescent lipid into the liposomes and treating the cells with chemical inhibitors against distinct endocytosis pathways and was found to be clathrin-mediated. Furthermore, using a microfluidic setup to mimic the dynamic in vivo environment, the cell/surface interactions were assessed showing a decreased uptake from the substrate under the influence of shear stress. In summary, liposomal drug deposits in nature-inspired poly(dopamine) films serve as an excellent coating for biomedical applications.
1. M. E. Lynge, M. B. Laursen, L. Hosta-Rigau, B. E. B. Jensen, R. Ogaki, A. A. A. Smith, A. N. Zelikin and B. Städler, ACS Applied Materials & Interfaces, 2013, 5, 2967-2975.
2. M. E. Lynge, R. Ogaki, A. O. R. Laursen, J. Lovmand, D. S. Sutherland and B. Sta#776;dler, ACS Applied Materials & Interfaces, 2011, 3, 2142-2147.
3. M. E. Lynge, B. M. Teo, M. B. Laursen, Y. Zhang and B. Stadler, Biomaterials Science, 2013, 1, 1181-1192.
4. M. E. Lynge, M. Fernandez-Medina, A. Postma and B. Städler, Macromolecular Bioscience, 2014, DOI: 10.1002/mabi.201400350

Investigations into the diverse and complex, nastic actuation mechanisms that exist in nature, have led to an explosion of work towards the development of stimuli-responsive, biomimetic materials and devices. For example, the same actuation mechanism that drives the folding and unfolding of pinecone scales-the differential swelling of composite, organic tissues—has been exploited in research to demonstrate water-vapor driven locomotion in artificial polymer bilayers, self-rolling, inorganic micro-inductor tubes, and 3D origami that self-folds from structures photolithographically patterned in two dimensions. Despite these notable advances, the scaling of biomimetic mechanics to micron and sub-micron sized objects remains a major challenge. In this work, we demonstrate the design and characterization of colloidal microparticles that store and release energy through mechanical bistability. Inspired by the Venus flytrap, whose snap-actuation is manifested through the built-in curvature of its leaves, we created shell-like polymer bilayer microparticles with pre-programmed curvature. Upon application of a stimulus, these asymmetric particles rapidly snap and invert into a second stable conformation. The bilayer particles consist of a ~300nm thick hydrogel layer, which expands and contracts as pH is increased and decreased, and a ~300nm thick pH-inactive layer which provides the elastic energy storage. The stimuli-induced shape changes are highly elastic and therefore, reversible; however, upon reversal of the applied stimulus, we observe hysteresis in their response, which is strong evidence for mechanical bistability. We report the effect of the polymer bilayers&’ elastic moduli, curvature, and relative thickness on the actuation mechanics, and as a potential route to program bistability into a wide library of particle shapes. We propose mechanical bistability as a new, unexplored means to perturb the self-assembled equilibria of colloidal systems.

In general, mechanical properties and gelation kinetics exhibit a positive correlation with the amount of gelation reagents used. Similarly, for catechol-containing hydrogels, which have attracted significant attention due to their unique dual properties of cohesion and adhesion, increased amounts of crosslinking agents, such as organic oxidants and/or transition metals (Fe³⁺), result in enhanced mechanical strength and more rapid gelation kinetics. Here, we report a new metal-ligand crosslinking chemistry inspired by mussels and ascidians that defies the aforementioned conventional stoichiometric concept. When a small amount of vanadium is present in the catechol-functionalized polymer solution (i.e., [V] << [catechol]), organic radicals are rapidly generated that trigger the gelation reaction. However, when a large amount of the ion is added to the same solution (i.e., [V] >> [catechol]), the catechol remains chemically intact by coordination that inhibits gelation. Thus, a large amount of crosslinking agent is not necessary to prepare mechanically strong, biocompatible hydrogels using this system. This new chemistry may provide insight into the biological roles of vanadium and its interaction with catechol-containing molecules (i.e., determination of the liquid vs. solid state). Excess amounts of vanadium ([V] >> [catechol]) coordinate with catechol, which may result in a liquid state for ascidian blood, whereas excess amounts of catechol ([V] << [catechol]) generate an organic radical-mediated chemical reaction, which may result in solid-state conversion of the mussel byssal threads.

New integrated modelling and experimental approaches are needed to improve biomaterial design and functional outcomes. Scalable computational modelling tools are required to integrate with and guide the experimental design of polymers in order to generate new biomaterials with predictable functions. Toward this goal, we utilize mesoscopic simulations with a coarse-grained description of silk proteins as multiblock copolymers, synergistically integrated with genetic protein sequence bioengineering and bio-inspired shear-flow focusing processing, to systematically demonstrate how biological silk spinning and the resulting features can be understood, predicted, and optimized in silico. Utilizing this approach has enabled us to elucidate key design features, such as molecular weight and the delicate balance between hydrophobic and hydrophilic domains towards the formation of robust silk protein biomaterials, including protein solubility, aggregate size, and polymer network connectivity. This integrated approach provides a path forward to generate well-defined functional protein biomaterials by exploring the sequence-structure-process-property relationship both in silico and experimentally.

Peptide nanomaterials are an important class of material for the food, cosmetic and biomedical industries. Short self-assembling peptides are extremely attractive due to the simplicity and diverse range of interactions that can be seen. Unfortunately, the self-assembling nature is often hard to predict. The use of very short (e.g. di- and tri-) peptides has advantages of cost, scalability and rational tenability however have been largely restricted to hydrophobic dipeptides, such as FF. ^[1] To date, most self-assembled peptide nanostructures are found serendipitously or by copying/modifying sequences known from biological systems. We are developing computational approaches to enable discovery of new assembling peptides, by predicting their aggregation propensity for tripeptide molecules. ^[2] We previously reported the use of coarse-grained molecule dynamics (CG MD) ^[3] as a tool to predict self-assembly behaviour, which led to the discovery of a new class unprotected tripeptide gelators: KYF, KYY, KYW and KFF. The focus of the current work is to further develop this tool coarse-grained molecular dynamics to show that the introduction of organic solvents will allow the creation of emulsified systems. Using CG MD, we show how the introduction of octane into an aqueous system can change the behaviour of the self-assembled peptides. Results show that these tripeptide molecules can act as surfactants, where they assemble at the interface between the octane and water. Experimental methods, such as confocal microscopy, can allow the tracking of these systems, where labelling of the organic solvent with a fluorescent dye allows visualisation of the emulsion system. In addition, spectroscopic analysis (FTIR, fluorescence) is used to assess the peptide arrangements in the emulsions. 3D images can be obtained of the emulsified particles allowing for a size distribution and overall dispersal of the emulsified particles to be obtained. We have therefore shown that CG MD can also be used for the identification of new emulsifiers comprised wholly of short unprotected peptides.
[1] Gazit et al (2003), Science, 300, 625-627
[2] Frederix PWJM et al (2014), Nat Chem, accepted manuscript
[3] Marrink S et al (2007), J Phys Chem, 111, 7812-7824

Glycoproteins prevalent throughout natural extracellular matrices (ECMs) influence diverse cellular behaviors, including adhesion, migration, growth, differentiation, and apoptosis. Peptide ligands that recapitulate the bioactivity of protein domains from various ECM glycoproteins have been widely explored for creating ECM-mimetic biomaterials. In contrast, glycoprotein carbohydrates remain under-utilized in ECM-mimetic biomaterial design, in part due to challenges associated with glycan synthesis and the absence of defined glycan structure-function relationships. Self-assembled peptide nanofibers have a rich history as ECM-mimetic biomaterials, due to their morphological similarity to natural ECM proteins, and simple integration of ECM-derived peptide ligands at precise concentrations or ratios. We envisioned that self-assembly of carbohydrate-modified “glycopeptides” would provide nanofibers that can recapitulate ECM glycoprotein interactions with carbohydrate-binding proteins (i.e. “lectins”). To test glycosylated peptide nanofibers as glycoprotein mimetics (GPMs), we synthesized a variant of a peptide that self-assembles into nanofibers, QQKFQFQFEQQ (Q11), in which an asparagine residue modified with the monosaccharide n-acetylglucosamine (GlcNAc) was conjugated to its N-terminus, N(GlcNAc)-SGSG-Q11 (GlcNAc-Q11). GlcNAc-Q11 self-assembled into beta-sheet nanofibers under aqueous conditions, similar to Q11. Nanofibrillar GlcNAc moieties were efficiently converted to a disaccharide, n-acetyllactosamine (LacNAc), via beta-1,4-galactosyltransferase and UDP-galactose, without perturbing nanofiber morphology. GlcNAc-modified nanofibers bound to a GlcNAc-binding lectin, wheat germ agglutinin (WGA), LacNAc-modified nanofibers bound to a LacNAc-binding lectin, galectin-1 (Gal1), and nanofiber lectin-binding affinity could be tuned by co-assembling GlcNAc-Q11 and Q11 at different molar ratios. Notably, WGA failed to bind to LacNAc-modified nanofibers, whereas Gal1 bound weakly to GlcNAc-modified nanofibers, demonstrating that nanofibrillar GPMs can selectively bind lectins according to their fine-specificity for distinct glycans. T cells, such as the Jurkat immortalized human T cell line, undergo apoptosis in the presence of WGA or Gal1. WGA- or Gal1-mediated Jurkat T cell apoptosis decreased as nanofiber GlcNAc or LacNAc concentration increased, respectively, indicating that nanofibrillar GPMs can modulate lectin bioactivity similar to natural ECM glycoproteins. Taken together, these results demonstrate that self-assembled glycopeptide nanofibers can act as GPMs with tailored lectin-binding affinity and specificity, which is governed by the type and concentration of glycans integrated into the nanofibers. We anticipate that nanofibrillar GPMs will be broadly applicable as biomaterials to both study the influence of lectin-ECM glycoprotein interactions on cell behavior, and harness these interactions for various biomedical applications.

There is a great need for defined cell culture systems that allow expansion of human pluripotent stem cells (hPSCs) and subsequent controlled differentiation, ideally in an implantable three-dimensional (3D) matrix. Spider silk appears to be an ideal biomaterial, since it is strong, extendible, and has favorable properties when implanted in living tissues. Spiders are difficult to house and therefor methods for recombinant production of spider silk are warranted. We have developed a method for production of recombinant spider silk fibers, films and foams that are used for the design of defined and xeno-free cell culture matrices. The matrices enable long-term expansion of multiple hPSC lines and subsequent differentiation into all three germ layers in 3D. This hPSC culture method provides robust, defined, easily produced and flexible culture environments for hPSCs (1).
These matrices are promising but to realize their full potential, we need to spin continuous fibers in a reproducible way. Spider silk fibers are produced from soluble spidroins under ambient conditions. The spidroins are large and highly repetitive in sequence but capped by non-repetitive N- and C-terminal domains (NT and CT). In the gland, a pH gradient, that goes from 7.6 to <5.7, is generated by active carbonic anhydrase. The terminal domains respond in opposite ways when pH is decreased from 7 to 5: Urea denaturation and temperature stability assays show that NT dimers get significantly stabilized and then lock the spidroins into multimers, while CT on the other hand is destabilized and unfolds into b-sheet amyloid fibrils, which can trigger fiber formation (2,3). There is a high pCO₂ in distal parts of the gland, and a CO₂ analogue interacts with buried regions in CT as determined by NMR spectroscopy. These simultaneous events constitute a novel CO₂ and proton dependent lock and trigger mechanism of spider silk formation that possibly can be harnessed in biomimetic spinning of artificial spider silk.
1. Wu S, Johansson J, Damdimopoulou P, Shahsavani M, Falk A, Hovatta O, Rising A. Spider silk for xeno-free long-term self-renewal and differentiation of human pluripotent stem cells. Biomaterials. 2014 Oct;35(30):8496-502.
2. Kronqvist, N., Otikovs, M., Chmyrov, V., Chen, G., Andersson M., Nordling, K., Landreh, M., Sarr, M., Jörnvall, H, Wennmalm, S., Widengren, J., Meng, Q., Rising, A., Otzen, D., Knight, S. D., Jaudzems, K., Johansson, J. Sequential pH-driven dimerization and stabilization of the N-terminal domain enables rapid spider silk formation Nat Comm. 2014. 10(5):3254.
3. Andersson M, Chen G, Otikovs M, Landreh M, Nordling K, Kronqvist N, Westermark P, Jörnvall H, Knight S, Ridderstraring;le Y, Holm L, Meng Q, Jaudzems K, Chesler M, Johansson J, Rising A. Carbonic Anhydrase Generates CO2 and H+ That Drive Spider Silk Formation Via Opposite Effects on the Terminal Domains. PLoS Biol. 2014 Aug 5;12(8):e1001921

Spiders use specialized glands to make different types of protein-based silks with remarkable biochemical and mechanical properties, and artificial spider silk could be an ideal source for generation of novel biomaterials. Spider silk fibres contain crystalline β-sheet regions, which mediate mechanical stability, but the soluble silk proteins (spidroins) are stored at huge concentrations under physiological conditions, without aggregating prematurely. These properties have so far not been mimicked by recombinant spidroins. Spidroins contain unique repetitive segments, which determine the mechanical properties of the silk, as well as non-repetitive N- and C-terminal domains (NT and CT), which regulate conversion of the dope into fibres. We have recently made important progress in the understanding of the physiological regulation of spider silk formation and the molecular actions of NT and CT.
We now use this knowledge to develop novel miniature spidroins with optimal properties in terms of solubility, yields upon recombinant production, and stability. A first generation of novel, designed minispidroins that show very high expression yields and solubility, and that can convert into fibres using a biomimetic spinning procedure have been generated. In order to enable further rational design of spidroins for generation of biomaterials, we also study spidroin structures in soluble and fibrillar states, and analyse the molecular mechanisms of NT and CT structural conversions from high pH to low pH states.
REFERENCES
[1] Kronqvist, N., Otikovs, M., Chmyrov, V., Chen, G., Andersson M., Nordling, K., Landreh, M., Sarr, M., Jörnvall, H, Wennmalm, S., Widengren, J., Meng, Q., Rising, A., Otzen, D., Knight, S. D., Jaudzems, K., Johansson, J. Sequential pH-driven dimerization and stabilization of the N-terminal domain enables rapid spider silk formation Nat Comm. 2014. 10(5):3254.
[2] Andersson M, Chen G, Otikovs M, Landreh M, Nordling K, Kronqvist N, Westermark P, Jörnvall H, Knight S, Ridderstraring;le Y, Holm L, Meng Q, Jaudzems K, Chesler M, Johansson J, Rising A. Carbonic Anhydrase Generates CO2 and H+ That Drive Spider Silk Formation Via Opposite Effects on the Terminal Domains. PLoS Biol. 2014 Aug 5;12(8):e1001921.

Multi-photon lithography (MPL) is a versatile technique that allows for the direct write, high-resolution fabrication of complex, 3D structures via the spatially controlled polymerization of a variety of monomer chemistries, including proteins. In this method, a focused pulsed laser is translated in a solution containing a photo-activator dye and the protein monomer solution. Within the focus of the laser, the excited dye induces the production of tyrosine radicals that form covalent bonds with nearby (i.e., inter- or intra-protein) Tyr, Lys, or Cys residues. The formation of these covalent bonds produces a small volume of cross-linked protein hydrogel. Solid, 3D structures are produced by translating the laser focus through the sample volume in a controlled pathway. In this work, we have explored the application of MPL for the fabrication protein microstructures from aqueous solutions of regenerated silk fibroin (RSF). The use of RSF in 3D printing is advantageous as this protein contains a high proportion of Tyr residues, exhibits excellent biocompatibility, high toughness, tailorable biodegradability and optical clarity. Furthermore, these precisely patterned protein hydrogels may be used in tissue engineering to control biological interactions, as responsive biosensor elements, as integrated optical devices, and to carry enzymes that catalyze local chemical reactions. The effect of MPL processing and writing parameters on the intrinsic and applied properties of 3D printed silk fibroin will be discussed in this presentation.

Silks are biological polymers that have evolved to be processed by controlled protein denaturation, a process depending on the researchers&’ background, with similarities to amyloidogenesis for some and flow induced crystallisation for others. Hence if we wish to harness the power of silk we must first understand it. Understanding means not only knowing the relevant proteins but also knowing their function and, importantly, their structure - property - processing relationships. And here is a gap in our present knowledge. Silk proteins have been patented by many research groups and companies and been expressed in bacteria, plants and animals. However it is processing that defines a silk, for unlike all other biological materials they are spun, not grown. We provide an overview of Natures 400 million years of R&D into silk and our recent studies into the importance of processing in this fascinating material. We conclude there is more to silk than just a fibre and that Nature may in fact hold unique solutions to the current challenges facing the synthetic polymer industry, i.e. routes towards low embodied energy, sustainable wet processing of polymers.

Self-assembly of block copolymers (BCPs) provides a fascinating approach for creating photonic materials due to their ability to organize into 1D, 2D and 3D periodic microstructures with a long range order. Their periodic dielectric structures allow to modulate the propagation of electromagnetic waves, producing strong structural colors. Here, we demonstrate one-dimensionally periodic block copolymer photonic sensors with full-color tunability as a result of pH changes. The photonic lamellar gels were realized via the self-assembly of a hydrophobic block-hydrophilic block copolymer, polystyrene-b-poly(acrylic acids) (PS-b-PAA). The selective swelling of the PAA domains leads to extremely large tunability of the photonic stop band from blue to red wavelengths as a function of pH changes of aqueous solution. The reversible color changes and swelling behaviors are strongly dependent on the protonation/deprotonation of the acrylic acid groups in the lamellar microdomains. These tunable structural color materials may be attractive for pH-responsive photonic sensors.

The use of non-covalent self-assembly to construct materials has become a prominent strategy in material science offering practical routes for the construction of increasingly functional materials. A variety of molecular building blocks can be used for this purpose. One such block that has attracted considerable attention in the last 20 years is de novo designed peptides. One family of self-assembling peptides which has attracted particular interest are the so-called “β-sheet forming peptides”. Through the appropriate design of the primary amino acid sequence, short peptides can be designed that self-assemble into β-sheet rich fibres that above a critical gelation concentration entangle/associate to form very stable hydrogels. These materials are thought to have potential in a variety of applications such as tissue engineering and drug delivery.
A particular design developed by Zhang and co-workers is based on the alternation of hydrophilic and hydrophobic amino acids. (Zhang, SG et al.; Biopolymers, 1994, 34, 663) Recently significant work was reported on the effect changing the hydrophobic residues has on the gelation properties of these peptides. (Mohammed A., et al.; Macromolecular Symposia 2007, 251, 88) (Bowerman, CJ, et al.; Biomacromolecules 2011, 12, 2735) Less attention has been given though to the effect that the primary amino acid sequence has on gelation.
Here we report on recent work we performed on the effect that the primary amino acid sequence has on the self-assembling and gelation properties of a series of octa-peptides where the hydrophobic amino acids are phenylalanine (F x 2) and alanine (A x 2) and the hydrophilic amino acids are lysine (K x 2) and glutamic acid (E x 2). Using these amino acids a series of peptides with identical hydrophobicity but different sequences were designed to explore the stability of the β-sheet configuration and the effect this has on the gelation capability of these peptides.
It was found that the sequence of the hydrophobic amino acids has a dramatic influence on the capability of the peptides to self-assemble to fibrous structures and form hydrogels. This relates to a number of factors, the primary two being the ability of the peptide to adopt alternate secondary structures other than a β-sheet, and the packing of the hydrophobic amino acids against one another in a β-sheet structure. These results show that while the overall hydrophobicity of β-sheet forming peptides is important the arrangement of amino acids is critical for controlling hydrogel formation. This work brings new insight into the design rules of these β-sheet forming peptides.
ACKNOWLEDGMENTS
The authors would like to thank the EPSRC Fellowship (Grant no: EP/K016210/1) for providing financial support to this project.

The treatment of dental caries (tooth decay) still primarily involves removal of hard mineralized (dentin, enamel) and possibly soft (pulpal) tissues and replacement with synthetic materials. Regeneration via tissue engineering would have many advantages, but fundamental questions remain. During tooth development the mineral producing odontoblast cells (OD) create a micro-tubular structure as they form dentin. Later, in response to a carious lesion or injury, progenitor/stem cells in the dental pulp may differentiate to OD which deposit reparative dentin. We hypothesized that a bioinspired micro-tubular structure would promote differentiation of the pulpal progenitor/stem cells to OD, thus influencing the reparative process. The fundamental effects of this bioinspired design have not been studied, in part because of the difficulty in fabricating the micro-tubular structure. Using a fiber-templating method with PVA sacrificial fibers and a PMMA matrix, we created three groups of 3D biomimetic tubular scaffolds with tubular diameters of 20-40 µm, and varying tubule densities between 200-400 per mm². Cells isolated from primary dental pulp cultures were seeded onto the tubular constructs at 60,000 cells/cm² and maintained for 7d, then continued until 21d with differentiation media. Cell differentiation was evaluated at 21d with immunostaining for nestin and gene expression analysis of OCN, DMP-1 and DSPP, all markers for OD. Results from the 3 experimental groups and non-tubular PMMA and tissue culture plastic controls were compared using one-way ANOVA on ranks. Immunostaining for nestin demonstrated a monotonic increased differentiation to OD with micro-tubule density. The stained cells were elongated and polarized, the typical morphology of OD. Gene expression on all three micro-tubular constructs was increased relative to the planar control, but there was no clear difference among the three micro-tubular groups. Taken together the results demonstrate an increased differentiation of dental pulp cells to OD when cultured on the bioinspired scaffolds designed to mimic the physiological structure of dentin. The diameter and density of the micro-tubular design evaluated here are still about a magnitude of order greater than dentin. Refinement of the fiber templating method or use of other methods may be necessary to mimic dentin more closely, but the results that differentiation increases with micro-tubular density justifies these future efforts. Other work from our laboratory has demonstrated the effect of surface decoration with functional groups on differentiation, and future studies will combine these approaches to create bioinspired structures more consistent with natural dentin. Support: Univ. CT UCIG #KFS-4615490, NIH/NIDCR R01-DE016689 and T90-DE022526, and UCHC Inst. Regen. Eng.

Chitosan, a load-bearing biomacromolecule found in the exoskeletons of crustaceans and insects, is an appealing biopolymer for the replacement of synthetic plastic compounds. Here, interactions of chitosan in aqueous solutions including the effects of pH, contact time, and molecular weight were investigated using a surface forces apparatus (SFA). Chitosan films showed adhesion to mica all tested pH range (3.0~8.5) and the adhesion has a maximum at pH 3.0 with 1 hr contact time (F/R ~30 mN/m). We also found no or only weak cohesion between two opposed chitosan layers on mica in aqueous buffer until the contact time reached to critical contact time for adhesion. Strong cohesion (F/R ~40 mN/m) between the films was measured with increased contact times to 1 hr at pH 3.0, which is equivalent to 50% of the strongest mussel adhesion. Such time-dependent adhesion properties are related to molecular reorientations and interdigitations. At high pH (~8.5), solubility of chitosan changes drastically causing the chitosan-chitosan interaction to be repulsive at all separation distances and contact times. The strong chitosan-chitosan adhesion properties provide new insight into the development of chitosan based load-bearing materials.

We present prototypes of a new and unique class of high-performance bioinspired thermochromic “motheye smart windows”. These interfaces passively regulate the solar induced green-house warming effect inside buildings in response to ambient temperature. Our method of fabrication exploits langmuir-blodgett colloidal self-assembled lithographic templates to create functional 3-D nanostructured surfaces over large areas. This technique is low-cost and environmentally friendly when compared with top-down approaches used to create similar structures.
The presence of nature inspired graded refractive index antireflection surface structures induce two key benefits. Firstly, an enhancement of the optical properties of vanadium dioxide, the thermochromic modulation material. The windows are designed to efficiently transmit visible light over a wide range of angles (insensitive to the light&’s polarisation) whilst maintaining strong solar-thermal energy modulation. This facilitates effective energy harvesting. Secondly, the high aspect ratio structures modify the hydrophobicity of the surface making it robustly super-hydrophobic; enabling the window to self-clean in the same way the leaves of many plant species are kept dust-free. Thus, the window surface inherits key functionality through biomimicry.
Our bioinspired approach increases the maximum solar energy transmission modulation (the critical factor in assessing energy harvesting potential) from 10% to almost 25% when benchmarked against traditional planar geometries. This ranks the motheye geometry amongst the very highest performing classes of VO₂ smart window. In addition to discussing our self-assembly fabrication techniques, we will examine the theoretical performance boundaries and design rules for these natural and functional structures with reference to electromagnetic FDTD simulations.

Peptides as a gatekeeper for payloads of mesoporous silica nanoparticles (MSNs) would exhibit triggered release properties of guests by various biological stimuli. We investigated the effect of the peptide conformation on their gatekeeping capability by employing two model peptides with a turn or a random structure. The conformation-dependent gatekeeping properties provided an opportunity to utilize the conformational conversion of peptides as a valuable motif for stimuli-responsive gatekeepers. We demonstrated that the gatekeeping capability of the peptides, Fmoc-CPGC and Fmoc-CGGC, was highly dependent on the secondary structure. These results led us to utilize the conformational conversion of peptides as a valuable motif for stimuli-responsive peptide gatekeepers for MSNs. As a model system, we prepared Fmoc-CGGC-SS-Si which exhibited a zero-release property without any stimuli in physiological condition due to a turn-like conformation induced by the intramolecular disulfide bond. Upon addition of GSH, the guest molecules in the MSN were triggered to release by the conformational conversion from a turn-like to a random structure induced by reduction of the disulfide bond. We further demonstrated that the conversion of the secondary structure of Fmoc-CGGC by Zn(II) ion can also be utilized as a useful trigger for stimulus-responsive gatekeeper. These results provide valuable information for optimized design of stimuli-responsive multifunctional peptide gatekeepers which would be useful delivery vehicle with on-demand release characteristics.

Lipids are important components of many biological entities, such as cellular membranes, intracellular organelles, and adipose tissue, and engineered materials, such as lipid-based drug delivery vehicles and lipid membrane biosensors. We describe the self-assembly, structure, and function of an important lipid system, the intercellular lipids of the outermost layer of human skin, the stratum corneum (SC). Functionally, the intercellular lipids are the main barrier to water through the SC and have also long been compared to “mortar” holding the cellular “bricks” together. However, it is unclear how much cohesion the lipids actually provide and how lipid composition alters the structure and function of the barrier.
The nature inspired lipid structures we synthesized were composed of ceramides, free fatty acids, and cholesterol in equimolar ratios. They self-assemble to form bilayers with two lamellar phases with periodicities of approximately 6 nm (short periodicity phase, SPP) and 13 nm (long periodicity phase, LPP), where formation of the LPP depends upon the presence of ceramide EOS. We quantitatively determined the cohesion of model lipid films and explored the effects of varying ceramide and fatty acid content on structure. The SPP structures exhibited significantly lower cohesion compared to LPP structures. Overall, the lipid cohesion was quite low compared to the cellular cohesion of stratum corneum, indicating the intercellular lipids are a weak contributor to cohesion. We also found that varying the free fatty acid chain length had a much smaller effect on cohesion than altering the ceramide content, although the movement of permeants through the lipids was altered.
Understanding how lipid self-assembly and the resulting structure and function of lipid films depends on lipid content will enable better treatment of skin diseases involving lipid abnormalities. Furthermore, fundamental understanding of the origin of cohesion in lipid membranes will aid development of bio-inspired lipid-based technologies such as tissue engineering, biosensing, and drug delivery.

A form of self-assembly, "self-folding" presents an alternative approach to the creation of reconfigurable, responsive materials with applications ranging from robotics to drug design. However, the complexity of interactions present in biological and engineered systems that undergo folding makes it challenging to isolate the main factors controlling their assembly and dis-assembly. Here we use computer simulations of simple, minimalistic self-foldable structures and investigate their stochastic folding process. By dynamically accessing thousands of states that lead to, or inhibit, successful folding, we find correlations between the geometry of the initial 2 dimensional sheet and the folding propensity.

Polymersomes formed by the self-assembly of amphiphilic block copolymers are one of the most versatile vesicular architecture among the self-assembling systems. These structures possess prominent interest for various applications varying from biomedical to material science engineering. The scope of the polymersomes for these utilizations is highly related to their membrane attributes that can be controlled by tuning the block copolymer design and by functionalization with biomolecules.
Here we demonstrate the synthesis of ABA triblock copolymer using various mix and match click approach for varying the length of each block. This decides the interfacial tension between the blocks that determines the packing parameter of the individual molecules forming polymersome. Our combinatorial synthesis approach provides the diversity to make block copolymers with various block-length combinations that leads to the formation of diverse structures. In this study we focused on constructing biocompatible triblock copolymers of polydimethylsiloxane (PDMS) as the hydrophobic middle block and polyoxazoline (POx) at both ends and evaluated the molecular dynamic driving forces for formation of the polymersome architectures. ABA triblock molecules with controlled molar mass of each block and polydispersity play an important role on the vesicle size and their distribution. The curvature energy of the formed vesicles seems to be influenced by the block length of the hydrophilic units thereby enabled us to tune the structural formation from spherical to rod and further elongated to tubular spaghetti shapes up to 2 mm in length.
Biologically inspired membrane is a major application area in which polymersomes find its role by incorporating membrane proteins or other biomolecules in to the vesicular walls. This approach can determine its permeability to different species, depending on the nature of protein. Rafting these functionalized vesicles by an appropriate linker or anchor them on to a substrate is the generally accepted method for membrane construction. Alternatively, utilizing these tubular polymersomes for the incorporation of biomolecules leads to new way for fabricating bio-membranes offering selective permeability.

Peptidic bolaamphiphilic moelcule is a amphiphilic molecule with two hydrophilic, peptidic moieties at ends of central hydrophobic chain. Self-assembly of the peptidic bolaamphiphilic molecules received attention in the past decades because of their structural and chemical properties can be adjusted by the amino acid. In this presentation, synthesis and applications of a simple tyrosyl bolaamphiphilic molecule, bis(N-alpha-amido-tyrosine)-1,7-heptane dicarboxylate (Tyr-C7 hereafter) are to be delivered. This molecule self-assembled to create spherical structure in an aqueous solution with exposure of carboxylic acid and phenolic groups on the surface. Exploiting the surface-exposed functional groups, the self-assemblies were applied as a reactive catalyst support and photoluminescent sensors. Firstly, the biochemical reactivity of tyrosine phenol was utilized to create Pd catalyst on the self-assembly. Ag ions reduced to solid clusters by the deprotonation of the surface-exposed phenol moieties at the basic condition and subsequent reduction of Pd ions to create Pd catalysts on the self-assembly. The Pd catalyst-deposited self-assembly was examined its catalytic performance. A model reaction of dichromate reduction was performed using the Pd catalyst with investigation on the reaction kinetics. Secondly, the self-assembly associated with a photoluminescent lanthanide ion and a photosensitizer was used as an optical sensor probe for the detection of nitroaromatic compounds. The tyrosyl group showed an antenna effect enhancing photoluminescence and functioned as a selective binding moiety for a target nitroaromatic compound. The photoenergy transfer and molecular interaction between the photoluminescent compounds and bolaamphiphile molecule were investigated through optical and spectroscopic techniques. Outcomes of this study indicated that the peptidic bolaamphiphile self-assembly can be used as a soft platform with a variety of biochemical functionalities.

Carbon dioxide (CO₂) release in the atmosphere has been controlled in past few decades because it is a major global warming gas and has economic viability. Various chemical and biological methodologies have been explored for the CO₂ capture and sequestration. Among many biological techniques, use of carbonic anhydrase (CA) as an biocatalyst is most promising for CO₂ sequestration. CA catalyzes the hydration of CO₂ to transform into bicarbonate ion in water. However, thermal instability and high cost made difficult to use CA for industrial use. In order to overcome this hurdles, development of CA-mimetic catalysts is needed. Here, we synthesized a novel CA-mimetic catalyst through the self-assembly of histidyl bolaamphiphilic molecules. Since the active site of CA is made of a zinc ion coordinated with three histidine imidazoles, self-assembly of histidyl bolaamphiphile creates molecular arrangement of imidazoles, and subsequent association with Zn ion can create catalytic analogues easily. The catalytic activity of the prepared catalyst was tested under the variations of kind of zinc salt, zinc concentration, PH, and temperature. The catalytic performance was differentiated by the Zn-pairing anion that disordered the Zn-hydroxide coordination. From the thermodynamic analyses, the dissociation energy of the pairing ion from Zn cation was turned out to be inversely proportional to the catalytic activity. For the practical application, recycling of the biomimetic catalyst and CaCO₃ precipitation by CO₂ sequestration were examined. This study clearly demonstrated the successful creation catalytic analogues of CA active sites through the self-assembly of bolaamphiphilic molecule with designer amino acid moiety.

Pyrrole is a heterocyclic compound used for the preparation of conducting polymers. With increasing usages of the conducting polymer in various applications in daily life, development of the detection and monitoring methods of pyrrole and other heterocyclic compounds is needed in recent years. In this study, photoluminescent microrods were prepared here through the self-assembly of Nprime;1,Nprime;6-bis(3-(1-pyrrolyl)propanoyl) hexanedihydrazide (DPH) for the optical detection of pyrrole among the heterocyclic compounds. This molecule is composed of two pyrrole rings that are conjugated through amide bonds with a alkyl chain. In the presence of a photosensitizer and a lanthanide ion, DPH molecule created photoluminescent microrods through evaporation-induced self-assembly (EISA). Rod-like self-assembly of DPH molecules functioned not only as a host matrix holding photoluminescent compounds but also as a photosensitizer enhancing luminescence from lanthanide ions. The photosensitizing function induced by the molecular self-assembly is distinguished property of DPH compared to other amphiphilic molecules reported. To certify the photosensitizing effect of DPH microrods, fluorescence spectroscopy with the consideration on the photon energy transfer was carried out. Exploiting the photoluminescent microrods as optical probes, selective detection of pyrrole was achieved among similar hetero cyclic compounds. Photoluminescence from the microrods was quenched when the DPH microrods were associated with pyrrole, which might be promoted by the structural similarity between DPH and pyrrole. Dynamic quenching mechanism explained the pyrrole quenching of the DPH microrod fluorescence. Limit of detection for the pyrrole monomer was 3.5 mM, which is considerably low comparing to other methods reported. Photoluminescence quenching was increased proportional to the pyrrole concentration making the DPH microrod promising as an quantitative optical sensor. In summary, we report a facile way to prepare a photoluminescent microrod sensor probe through the EISA of a self-assembling molecule.

Over hundreds of thousands of people all over the world are suffered from traumatic peripheral nerve injuries caused by foreign object penetration and/or blunt trauma[1]. These injuries often involved in complete or partial transection of the nerve which lead to muscle paralysis or cripple. The traditional suture techniques for the nerves anastomosis often face the problems of repetitious epineurium damage and structural disturbance in the nerves interfering the axon regeneration, and therefore impairing the nerve physiological function[2]. Besides, the surgery procedure is too complicated and time consumed to handle very well.
The adhesives, such as cyanoacrylates or fibrin-based surgical glues, have been clinically studied as alternatives to suture in end-to-side nerve regeneration, but they remain several noteworthy limitations for their inadequate adhesion and/or biocompatibility [3,4]. Thus the adhesives with nerve biocompatibility and high adhesion strength are urgently needed. Recently a polyethylene glycol containing semi-interpenetrating hydrogel based on Azidobenzamide grafted chitosan was reported. The graft of Azidobenzamide facilitated the quick gelation of chitosan under UV light to seal the transected nerve. While the interpenetration of polyethylene glycol increased the adhesion strength about 1.56 times higher than that of the commercial fibrin glues [5].
Ideal nerve adhesive materials should be nerve biocompatible with fast curing speed, high adhesion strength, and little damage and irritation to nerve trunk. To achieve this goal, we designed an in situ forming nerve adhesive hydrogel which mimicked the polysaccharides/polypeptide structure of natural epineurium matrices with preferable adhesive ability. Catechol groups were introduced onto ε-polylysine molecules to fabricate a mussel-inspired peptide to enhance the interfacial adhesive force between the hydrogel and epineurium. Maleimide groups were also grafted on this peptide to guarantee the fast hydrogel formation speed (curing speed) with thiolated chitosan via mild Michael-type addition. The hydrogel gelation occurred within 10 s which is quick enough to seal the transected nerve promptly. The storage modulus of hydrogel was over 2400 Pa and their adhesion strength was 8 times higher than that of the fibrin glue through the nerve tensile test after anastomosis. The in vitro cell experiment and animal experiments demonstrated the compatibility of hydrogels with nerve tissues. After 8 weeks of adhesion with the hydrogel, sciatic nerves of rats showed axonal recovery and the functions of the nerves were almost restored. Thus the in situ hydrogel designed by us offered enough cohesive and adhesive force and could be a promising adhesive for the repair of severed peripheral nerve.

The ability to remotely manipulate interactions between biomolecules and nanomaterial surfaces is an important goal to achieving reconfigurable materials with enhanced properties and precise nanostructures for sensing, catalysis, and biomedical applications. However, this is dependent on understanding the effects of peptide secondary structure on binding, designing peptides that adopt multiple different conformational states, and/or incorporating stimuli responsive elements that trigger reversible structural changes. In nature, for example, biological systems exert control over protein structure and function in response to light for signaling, UV protection, and regulating circadian cycles. Consequently, this photo control has been imparted to a small helical peptide in the form of an optical trigger to reversibly switch its structural conformation. We have used a photo-isomerizable azobenzene cross-linker to modulate the binding affinity of peptides to a palladium surface using light. In this case, the optical trigger of the modified peptide promotes a conformational/structural change and lowers binding affinity to the palladium surface. Ultimately, this presents a general approach to replace biomolecular recognition elements from a sensor surface, or control the biofunctionalization of surfaces using an optical stimulus.

Human mesenchymal stem cells (hMSCs) are adult multipotent progenitor cells able to differentiate into a broad number of therapeutically important cell types such as muscle, bone, and cartilage. Due to their ease of acquisition, their favorable immunoregulatory properties, and their differentiation potential, they are prime candidates for autologous cell therapy. When cultured ex vivo, hMSCs have been shown to be highly responsive to their substrate material. Factors such as substrate stiffness, cell shape, and integrin mediated adhesion to the extracellular matrix (ECM) are key to regulating MSC multipotency and differentiation to specific target lineages.
While much work has focused on examining these regulatory factors independently, not many model systems have been developed that can study combinatorial factors for cell shape and ligand affinity. Using microcontact printing of azido-functionalized alkanethiolates on gold, we report a model platform on which we can regulate cell shape and specifically control ligand affinity. Using copper-catalyzed alkyne-azide cycloaddition (CuAAC), we functionalize RGD peptide ligands with low and high affinity to MSCs in various aspect ratios. We note that there seem to be competing effects of ligand affinity with cell aspect ratio in respect to smooth muscle differentiation of the MSCs. At low aspect ratio, ligand affinity seems to be the prime determinant for smooth muscle phenotype, while at high aspect ratio, ligand affinity seems to have little effect. We investigate the pathways involved and report the influence of Rac1, ROCK, and calpain on the smooth muscle differentiation of MSCs. This new tool thus enables a systematic study of how cell shape and ligand affinity can influence fate decisions.

The beak of the squid is a unique natural nanocomposite. The sharp tip of the beak is one of the hardest fully organic materials, with the rest of it gradually evolves into a soft, compliant wing. The squid beak is composed of a chitin nanofiber network embedded within a protein matrix containing dopamine. The gradient in mechanical properties is achieved with spatially controlled tanning. Tanning is the oxidation catechol groups in dopamine, which further polymerize into polydopamines and cross-link with primary amine groups of chitin. Inspired by the squid beak, we develop a dopamine cross-linked self-assembled chitin nanofiber composite that mimics both chemistry and structural components of squid beak, exhibiting large gradient of mechanical strength and stiffness. With extraordinary mechanical properties and tunability, the presented biomimetic composite may find useful in biocompatible coating and lightweight defense under hydrated conditions.

In nature, there are many creatures which have functional structures on their body. Self-cleaning structure, unique mechanical structure, photonic crystal structure is such a cases. Among nature structures, photonic crystal structure which generates structure color have a lot of potential for various interesting application. Fascinating and eye-catching blue color of Butterfly Morpho didius is one of example of structure color by photonic crystal structure. Coherent scattering of white light by periodic three dimensional structure on wing scales of Morpho didius produces constructive interference of blue light. In addition to structure color, pigment layer which reflects wavelength of blue color plays important role for vivid color generation. Because of outstanding performance of nature structures, tremendous researches are performed to mimic these structures. Unfortunately, however, almost every nature&’s photonic crystal structure is three dimension like that of Morpho didius and, what was worse, sometimes quasi-ordered. In nature, these useful functional structures are constructed by complex interaction between proteins which is encoded in gene sequence of creature. Artificial fabrication of these complex structures have been important challenge for engineers. It is difficult, expensive and time consuming to fabricate complex three dimensional structure with common Top-down technology such as photolithography. Bottom-up technology such as self-assembly of primary building block have dealt with proper alternative of photolithography in this case. Here, we describe quasi-ordered three dimensional photonic crystal which is composed of M13 bacteriophage. Furthermore, by adopting microheater chip as a substrate of M13 bacteriophage photonic crystal, we fabricated efficient colour pixels.

Self-assembly technique has taken a great attention to develop more thinner and micro-constructive devices, which satisfy our diverse demands in miniaturizations. Recently, this technique has been widely used and investigated to design and build up nanostructures and self-assembled micropatterns to fabricate bio-devices at the nano- or micro-scales. Significant effort has been made in this area to design such bio-chemical building blocks at the molecular scales to lead new directions for high performance bio-technologies. In this work, we employed a novel bio-sensing material, “Molecularly Imprinted Polymer (MIP),” which has molecular recognition functions to detect specific targeting molecules. The molecularly imprinted polymer can be synthesized by “Molecular Imprinting Technique,” which is a general protocol for the creation of synthetic receptor sites or binding sites with specific recognitions. MIP&’s nano- or micro-patterns can be also fabricated by self-assembly molecular building blocks. MIP&’s thin layers can be generated on a variety of substrates including the surfaces of glasses, flexible substrates, silicon rubbers (poly dimethyl siloxane-PDMS), and silicon wafers. Especially, this study will introduce a molecular construction of MIP&’s layers for flexible electronics of bio-chemical sensors.

We report a generally applicable strategy based on mussel-inspired polydopamine (PDA) for rational design and tailored synthesis of core-shell nanohybrids. Self-polymerization of dopamine in the presence of virtually any solid substrate leads to a stable and conformal PDA coating that is bound to the substrate through covalent and/or non-covalent interactions. A unique combination of physicochemical characteristics of PDA plays critical roles in the success of our strategy. First, the adhesive nature and controllable growth kinetics of PDA makes it possible to form a conformal layer of PDA with controlled thickness on a wide spectrum of nanoparticles of different chemical identities and functionalities. Second, the PDA coating endows the nanoparticle cores with excellent colloidal stability. Besides, the benzene rings coupled with catechol and amine groups in PDA offer the potential to allow PDA-coated nanoparticle to self-assemble at the oil-water interface. Third, the metal-chelating activity and redox reactivity of PDA enables localized reduction of metal precursors, providing unique opportunities for constructing multifunctional nanohybrids. By taking advantages of above virtues, we have successfully developed a novel stepwise synthesis for core-shell bimetallic nanocrystals, which can act as recyclable heterogeneous catalysts.¹ We envision that the full potential of this strategy in emerging fields such as nanomedicine and catalysis has yet to be realized with the emergence of new building blocks, fueled by recent advances in tailored synthesis of nanocrystals.
(1) Zhou, J. J.; Duan, B.; Fang, Z.; Song, J. B.; Wang, C. X.; Messersmith, P. B.; Duan, H. W. Adv. Mater.2014, 26, 701.

Colorectal cancer (CRC) remains one of the leading causes of cancer-related deaths worldwide. Incidence of CRC is increasing annually in both sexes, ranking second and third in 2011 for cancers in men and women, respectively. CRC has a high post-operative recurrence rate achieving a radical cure is difficult because of a strong invasiveness in the progressive stage. Consequently, there is an increasing demand for the development of more efficient CRC treatment systems. Gene therapy is a potential novel treatment modality for treatments of tumors. In particular, branched polyethylenimines (bPEI) are effective cationic polymers that are widely used for gene delivery. They form a nano-sized complex (polyplex) with negatively-charged DNA by electrostatic interaction which leads to efficient cell internalization and easier endosomal escape Previously, in order to achieve high transfection efficiency while maintaining low cytotoxicity, we introduced disulfide (-S-S-) linkage to form bioreducible bPEI (SS-bPEI) containing a multiple amine backbone. Introducing disulfide linkage not only increased gene transfection, but also provided biodegradable capabilities via endogenous enzymes such as glutathione reductase. The cancer-targeting moiety of a delivery vehicle can also play an important role in efficient treatment by reducing unwanted systemic toxicity and overcoming dose limitation CPIEDRPMC (RPM) peptide which was firstly introduced as a molecular probe for early detection of colon cancer in 2003, targets invasive colorectal cancer. The RPM peptide has a RPM conserved motif and binds specifically to integrin α5β1 in human invasive colon cancer cells. However, RPM peptide is yet to be tested as a potential vector for targeting therapy or for use in other RPM-conjugated applications.
In this study, we exploited RPM peptide as a targeting ligand to produce a novel and efficient gene delivery system that could potentially be used to treat invasive colon cancer. In order to achieve enhanced specificity to colon cancer cells, the RPM peptide was conjugated to a bioreducible gene carrier consisting of a reducible moiety of disul#64257;de-crosslinked low molecular weight polyethylenimine, IR820 dye, and polyethylene glycol. Here, we examined the physiochemical properties, cytotoxicity, in vitro transfection efficiency, and in vivo biodistribution of the RPM-conjugated polyplex. Our results showed that the RPM-conjugated gene carrier formed a compact polyplex with pDNA that had low toxicity. Furthermore, the RPM-conjugated polymer not only had higher cellular uptake in invasive colon cancer than the non-targeted polymer, but also showed enhanced transfection efficiency in invasive colon cancer cells in vitro and in vivo. Taken together, our results suggest that RPM-conjugated bioreducible polyethylenimine systems could be exploited as an efficient gene delivery carrier to treat colorectal cancer.

Natural patterns have always been fascinating and a constant source of inspiration for researchers in developing new structural designs and synthesis of new materials for technologically important systems. As far as patterning is concerned, it has found its great potential in various fields such as microelectronics, micro-fluidics and micro-biology. The most common process used for micro-fabrication is lithography- which involves the formation of 3d structures from 2d patterns (subtractive technique) using various etching techniques. These 3d structures are generally in the form of excavated regions or raised portions. However, these 3d structures can also be produced using printing (additive technique) such as inkjet printing, screen printing, gravure printing, but in this case, the height of the patterns is short compared to the lateral dimension.
Present work, draws its inspiration from a tree where scratched features on its bark, as a result of self healing process, get transformed into protrusions rather than indentations which are generally seen on other trees. An attempt has been made, to mimic this process on a reasonable length and time scale by growing microbes, which is routinely done in a biological laboratory.
A novel approach has been developed for producing patterns of significant height after printing microbes in a two dimensional fashion. We employ the property that microbes can be rapidly grown on a solidified nutrient media to form microbial colonies. Customized patterns of these colonies can be obtained by using growth supporting or growth inhibiting agents. The customized patterns thus obtained can find its applications in various fields. We demonstrate them in two specific applications- fabrication of micro-lenses for enhancing light extraction from organic light emitting diodes and producing braille texts on an ordinary paper sheets. Micro-lenses with height and diameter in the range of hundred microns have been fabricated leading to luminous enhancement of 20%. For Braille texts, braille dots with diameter 1.5 mm and height 0.5mm have been achieved. In the first application, this process has the capability to replace expensive lithography process for generating master template on silicon. In the later, this process provides a substitute for the mechanical processes used for printing braille text, which requires special paper, instead of ordinary paper used in this work.

Natural structural materials such as insect cuticles, crustacean shells and mollusk nacre often owe their unusual outstanding mechanical properties to the intimate interactions of chitin nanofibers with silk-like proteins. Here, we introduce a biomimetic nanocomposite produced by the solution self-assembly of chitin nanofibers co-assembled with a silk fibroin matrix. This chitin nanofiber-silk composite is unique in that it closely mimics the nanostructure and composition of the organic phase of the arthropod cuticle. Like its natural counterpart, our biomimetic composite has excellent mechanical properties and it is even stiffer than chitin, the stiffest component. FTIR shows that these mechanical properties in the blend of chitin and silk fibroin are a result of a strong hydrogen-bonding motif between them. Further, we study the crosslinking of chitin and silk fibroin with enzymatic reactions to achieve enhanced mechanical properties.

Viscoelastic polymer-colloid gel systems play a key role in natural biological organism, tissue engineering, and nanomedicine. A fundamental study of viscoelastic hybrid gel systems can provide new opportunities for the development of stimuli responsive functional materials that utilize biological self-assemblies for practical applications.¹ To the best of our knowledge, an experimental realization coupled with a theoretical approach of polymer-colloid systems has not been performed due to the difficulty of creating three-dimensional (3D) colloid connections within polymer networks. Here, we present the synthesis and characterization of a novel 3D viscoelastic polymer-colloid composite hydrogel consisting of fibrin network (protein responsible for human blood clots) densely and homogeneously decorated with polystyrene colloidal particles. The fibrin/colloid composite hydrogel was fabricated by polymerizing fibrinogen with the addition of thrombin in tris-buffered solution, followed by driving carboxylate modified latex (CML) particles into the as-fabricated fibrin network by means of constant-potential electrophoresis method. Confocal microscopy images taken from the wet-state of the sample and scanning electron microscopy images acquired from the dry-state both indicated that the particles passed through the large mesh fibrin network and were homogeneously distributed on the fibrin, indicating the fibrin and colloids have 3D connectivity. Furthermore, we investigated the viscoelastic response of our fibrin-colloid hydrogels by means of observing the oscillatory shear strain-stress behavior so that we can predict how the fibrin-colloid system would respond when exposed to external mechanical stimuli. We expect the fabrication and rheological understanding of this fibrin-colloid hybrid system will open a new possible way to employ viscoelastic polymer-colloid gels in practical applications for biotechnology.
Keywords: viscoelastic polymer-gel systems, dynamically reconfigurable behaviors, fibrin/colloid composite hydrogel, constant-potential electrophoresis, 3D connectivity, viscoelastic response
[1] Hall, L. M.; Jayaraman, A.; Schweizer, K. S., Molecular theories of polymer nanocomposites. Curr Opin Solid St M 2010,14, 38.

Proton conducting materials play a central role in a diverse array of renewable energy and bioelectronics technologies. Thus, a great deal of research effort has been expended to develop improved artificial proton conducting materials, including ceramic oxides, solid acids, porous solids, polymers, and metal-organic frameworks. Within this context, proton conductors from naturally occurring proteins have received relatively little scientific attention, despite advantages that include intrinsic biocompatibility, structural modularity, tunable physical properties, ease and specificity of functionalization, and generalized expression/purification protocols. We have recently discovered unexpected protonic conductivity for the cephalopod structural protein reflectin.¹ By characterizing this material with a diverse array of electrical and electrochemical techniques, we have found that its electrical figures of merit compare favorably to those of artificial proton conductors.¹ Moreover, reflectin&’s favorable electrical properties enable the fabrication of protein-based protonic devices.¹ Our findings may hold implications for the development of the next generation of biologically-inspired polymeric proton conductors.
1. Ordinario, D. D.; Phan, L.; Walkup IV, W. G.; Jocson, J.-M.; Karshalev, E.; Hüsken, N.; Gorodetsky, A. A. Bulk protonic conduction in a cephalopod structural protein. Nat. Chem. 2014,6, 596-602.

The successful reproduction of the microstructures found in biological specimens has created synthetic materials with remarkable properties. In this study, we aimed to gain a deeper understanding of the microstructural characteristics that are responsible for the rhinoceros beetle's elytra optical properties, characterize its mechanical properties and conducted experiments to create a synthetic material that mimics the reflectivity control. The hardened forewing of the rhinoceros beetle, Dynastes Hercules, is known to suffer color changes, from yellow-green to black, under diverse humidity conditions. This property has been attributed to the existence of a porous layer that absorbs water. In this study, we characterized the reflectance spectra of the porous layer in the visible and shortwave infrared regions, under dry and wet conditions, and determined the layer&’s mechanical properties. Optical and Scanning Electron Microscopy along with focused ion beam cross-sectional analysis were used to examine the pores and tubular structures that allow water into the sponge-like layer, leading to the color changes. Tensile tests were used to determine Young&’s Modulus and the tensile strength of the elytra. Hardness and density measurements were also performed. In addition, attempts to mimic the porous layer using anodizing techniques to fabricate tubular inorganic structures are reported. This work provides the foundation for a longer-term objective: design and generate synthetic materials that reproduce the functionality of biological materials. In this particular case, the new multifunctional material could find application as lightweight camouflage effective under visible and shortwave infrared conditions.

The cytoskeleton of living cells contains many types of crosslinkers. Some compliant crosslinkers allow energy-free rotations between filaments and the noncompliant crosslinkers do not. And the elasticity of disordered filamentous networks with compliant crosslinks is very different from networks with rigid crosslinks. Here, we model and analyze filamentous networks as a collection of randomly oriented flaments with thermal undulations, besides entropy, connected to each other by crosslinks that are modeled as force springs and angular springs. For relatively large extensions we allow for breakage of the crosslinkers. We show that the thermal fluctuation would affect the elastic response of networks at low strain. With the network strain increasing, the internal force would become strong enough to resist the thermal fluctuation. The elastic moldulus would diverge with different types of crosslinkers. We further demonstrae that introducing the breakage of crosslinkers results in different fracture energy of the whole networks which have never been done in other simulation. Our resluts can impact upon fibrin networks in biological and bioengineered tissues.

As synthesis cost and delivery time for synthetic DNAs have been significantly reduced, interesting DNA-based structures and materials were reported, many of which have been exploited applications in biosensing, drug delivery and regenerative medicine. Previously, we reported an enzyme-free, self-assembly strategy of two-dimensional fluorescent DNA dendrimer-like structure triggering by a specific DNA analyte [1]. This approach mimics a non-linear version of hybridization chain reaction and offers promises for ultrasensitive biosensing platform rivaled with PCR sensitivity. In this new study, we have exploited the assembly of hybrids of peptide nucleic acid (PNA) and DNA using nonlinear hybridization chain reaction approach. Unlike most other nucleic acid self-assembly containing electrostatically repulsive DNA strands, the assembly of PNA/DNA would exhibit higher affinity due to the neutral charge of PNA and thus the assembled structure should be more thermodynamically favorable and present interesting assembly characteristics. To validate this hypothesis, we have specially designed a set of DNA strands such that only PNA is kinetically favorable enough to continue the ongoing growth of dendritic hybrid as well as a cascade of toehold mediated strand displacement reactions once triggered by a target sequence. Using PNA/DNA dendrimer strategy, we further develop an ultrasensitive electrochemical nucleic acid sensing platform. By labelling the PNA with ferrocene (Fc-PNA), an electrochemical signal for detection, we are able to detect the presence of target sequence based on the signal reduction of free Fc-PNA. This method does not only take merits in controlled system leakage, but also achieving a non-linear amplified signal-off detection. Differential pulse voltammetry (DPV) scanning result shows that this approach offers high sensitivity with detection limit down to 100fM and an inherently high specificity for detecting single nucleotide polymorphisms. Utilizing a similar self-assembly strategy, we believe our approach could lead to a highly sensitive sensing method for disease-specific miRNA marker and a new biomaterial synthesis strategy for drug delivery applications.
Acknowledgements
We thank the Research Grants Council of the Hong Kong SAR Government for funding support (RGC 601212).
References
[1] Feng Xuan and I-ming Hsing, "Triggering Hairpin-Free Chain-Branching Growth of Fluorescent DNA Dendrimers for Nonlinear Hybridization Chain Reaction," JACS, vol. 136, pp. 9810-9813, 2014.

Both biological and synthetic hierarchical materials involve the (self-) assembly of building subunits across multiple size scales - such as in bone, neurons, membranes. Fundamental understanding of the structure-property relationship for these complex systems is crucial, but quantifying structural characteristics across orders-of-magnitude differences in length scale is challenging. In this work, we use nondestructive X-ray scattering to quantitatively map the structural order in hierarchically self-organized CNT forests. We use CNT forests because 1) they have a biomimetic/hierarchically self-organized structure, which can be synthetically tuned, making them an interesting model system/scaffold; and 2) composites based on CNT forests are promising for high-flux membranes, heat dissipation systems, and electrically conductive elements. However, we uniquely focus on highly breathable and protective composite skin layers where the CNTs act as a biomimetic pores for moisture vapor transport.
Using a suite of novel X-ray beamlines at the Advanced Light Source (ALS) and Linac Coherent Light Source (LCLS), we quantitatively map structural characteristics in CNT forests both spatially within the CNT material and across several length scales (~10^⁰-10^⁴Å) - ranging from the sp²-hybridized (graphitic) carbon to large micron-scale corrugations in the forest structure. Notably, we recently advanced our capabilities by demonstrating simultaneous small-/wide-angle X-ray scattering (SAXS/WAXS) spatial mapping of CNT forests with a 1.5-µm beamspot for unprecedented spatial resolution. We find distinct hierarchical relationships between the different length scales, and importantly connect the origin of these relationships to the synthesis/self-organization of these materials, guided by insights from in situ X-ray scattering during CNT synthesis.
In our scattering images, the azimuthal distribution of scattered intensity about the beamcenter is an ordinal measure of structural order, with which we draw quantitative relationships between order at different length scales to reveal the cascading decrease in order as characteristic feature size gets smaller. Furthermore, we observed scattering reflections along the vertical direction (i.e., meridian), producing scattering patterns reminiscent of those from collagen fibers. We performed electron microscopy and simulated scattering to confirm that these features resulted from regular corrugations along the length of the CNTs at nearly a micrometer pitch.
Ongoing and parallel work in our group is aimed toward expanding our X-ray methods to probe the structure of composite materials based on these CNT arrays. While we focused on exploiting these techniques to understand the self-organization of CNTs, our X-ray toolbox is expected to be equally impactful for the development and understanding of many other hierarchically ordered biomaterial systems.

3D-Assemblies of plasmonic nanoparticles (NPs) are highly interesting for their potential applications in the fields of plasmonic sensors, thin photovoltaic, light harvesting and optical metamaterials. In particular, assemblies of NPs into defined 3D-clusters of controlled sizes and optical properties are highly desired. In general, there is a variety of methods to produce plasmonic clusters, employing either electrostatic interactions [1] or molecular linking strategies including DNA-hybridization [2] or aptamer recognition. [3] However, most of these methods arduous in synthesis and yield only 2D structures on flat substrates or in bulk they suffer from low colloidal stability, bad reproducibility, low yields and high costs. In this work, we present a simple, upscalable and modular synthesis route for plasmonic nanoclusters in dispersion using protein coated NPs. [4-6] Such 3D plasmonic clusters exhibit high colloidal stability and reproducibility with tunable optical properties. Combining colloidal building blocks of different sizes and shapes, a variety of different core-satellite nanoclusters can be achieved, thus allowing for a fine-tuning of the optical properties at the nanoscale. The optical properties of the nanoclusters have been studied by using UV-Vis-NIR spectroscopy and dark-field optical microscopy and spectroscopy and were compared and correlated with finite difference time domain (FDTD) calculations. The morphology and size of the nanoclusters have been investigated by scanning and transmission electron microscopy
[1] R. G. Freeman, K. C. Grabar, K. J. Allison, R. M. Bright, J. A. Davis, A. P. Guthrie, M. B. Hommer, M. A. Jackson, P. C. Smith, D. G. Walter and M. J. Natan, Science, 1995, 267, 1629-1632.
[2] Y. H. Zheng, T. Thai, P. Reineck, L. Qiu, Y. M. Guo and U. Bach, Adv. Funct. Mater., 2013, 23, 1519-1526.
[3] N. H. Kim, S. J. Lee and M. Moskovits, Adv. Mater., 2011, 23, 4152-4156.
[4] M. Chanana, M.A. Correa-Duarte, and L.M. Liz-Marzán, Small, 2011, 7, 2650
[5] M. S. Strozyk, M. Chanana, I. Pastoriza-Santos, J. Pérez-Juste and L. M. Liz-Marzán, Adv. Funct. Mater., 2012, 22, 1436.
[6] M. Chanana, P. Rivera_Gil, M. A. Correa-Duarte, L. M. Liz-Marzán and W. J. Parak, Angew. Chem. Int. Ed., 2013, 52, 4179

One dimensional inorganic nanowire enables the realization of fabricating electronic devices at nanoscale. It is widely recognized that the spatial constrain inherited from organic template offers a promising route to directing inorganic nanocrystal growth with desired architecture. Among organic templates, biotemplates (e.g., virus, peptide and DNA) display numerous advanced nanostructures in large quantities, and thus stand out as a unique approach to one dimensional nanomaterials. In particular, DNA has been highly regarded as an ideal biotemplate for generating metallic nanowires due to its remarkably large aspect ratio (i.e., 2 nm in diameter and micrometers in length). Metallic nanowires including a broad range of materials (e.g. Au, Pt, Co, and Pd) have been successfully produced using DNA as biotemplates. However, the dramatic increase in stiffness and pronounced aggregations of metallized DNA molecules make it difficult to immobilize and precisely position the metallized DNAs on solid substrate. Thus, to achieve well-ordered and continuous metallic nanowires, an alternative and facile approach is to first craft regularly aligned DNA nanowire patterns on substrate, followed by in-situ metallization of DNA nanowires.
Here, we report in-situ metallization of well-ordered DNA nanowire patterns crafted by controlled evaporative self-assembly (CESA) and flow-enabled self-assembly (FESA). By constraining DNA aqueous solution in between two nearly parallel plates that were composed of a fixed upper plate and a lower substrate mounted on a programmable translational stage, DNA nanowires with unprecedented regularity were crafted over large area. A swelling induced transfer printing (SITP) strategy was used to transfer continuous DNA nanowires onto the desired substrate. The in-situ metallization of DNA nanowires were then enabled by exposing DNA nanowires loaded with metal salt under oxygen plasma. Moreover, DNA nanowires were used as template to align gold nanoparticles and nanorods. Such CESA and FESA of DNA are simple, remarkably controllable, and easy to implement, promising new opportunities in crafting bioinspired self-assembled structures for functional materials and devices.

Peptoids are a promising class of bioinspired polymers, which have several unique properties that bridge the gap between proteins and bulk polymers, such as sequence specificity, thermal stability, and resistance to protease digestion. Studies have shown that certain sequences can form 1D fibers and 2D sheets, thus they are promising candidates to develop self-assembling protein-like materials. The purpose of this research is to understand the mechanisms and controls on peptoid self-assembly and relate them to the underlying sequence.
Several peptoids with different sequences of hydrophilic and hydrophobic side chains were synthesized and shown to self-assemble into 2D or 3D structures ranging from bi-layer sheets to 2D fiber arrays to 3D porous networks. Their assembly pathways on mica surfaces were characterized in real time using in situ atomic force microscopy (AFM) and related to solution species observed through dynamic light scattering and TEM. During the assembly of porous networks, 3nm-high “proto-fibers” were found to be the basic building blocks. These extended laterally to create an initial 3-fold symmetric array of fibers one molecule in width. These grew outward in 3nm increments to ultimately form a 3D porous network. However, the nucleation of the proto-fibers occurred through transformation of a population of 5Å-high clusters having no apparent order and coexisting with monomers on the surface. Based on these results and XRD analysis of peptoid fibers and sheets, we propose a model to describe self-assembly of this peptoid. Initially, peptoid molecules adsorb onto the mica surface and aggregate to form the 5Å-high clusters in which the molecules are randomly arranged and “lying down”. Over time, these clusters undergo a transformation in which the molecules “stand up” and are joined by others, possibly from solution, to form 3nm-high bi-layer particles. The bi-layer particles then grow in length by addition of molecules to the fiber ends (x direction) and nucleation of new bilayers on the top (z direction).
The kinetics of peptoid assembly was also investigated. We found that the nucleation rate of 3 nm proto-fibers was initially constant, but dramatically increased after an incubation time that increased with peptoid concentration and decreased with calcium concentration. In contrast, formation of the 5Å clusters was initially constant and rapid by comparison, but their number reached a maximum before rapidly decreasing due to their conversion into 3 nm proto-fibers. We constructed a kinetic model that considers the competing rates of the various deposition, nucleation, and transformation processes. The predicted behavior agrees qualitatively with the observations and places bounds on the magnitude of the kinetic terms controlling the assembly pathway.

Biomaterial scaffolds are new class of soft materials that have shown great potential for the replacement of human tissues including bones, joints and ligaments. An ideal candidate should have biomechanical strength and tunable porosity that provides support, adherence and growth of cells under physiological conditions. A major problem in the area of tissue regeneration is necrosis (cell death) generally found in the center of most scaffolds due a limited or inexistent control of mass transport (nutrients, gases, waste management). The tuning of internal morphology of scaffolds (pores, pore networks) is not only sought to eliminate cell death but to enhance cell proliferation. We have developed smart responsive liquid crystal (LC) elastomer scaffolds with tunable internal morphology and porosity as non-toxic, biocompatible elastomer scaffolds for tissue regeneration.[1] The new e-caprolactone based elastomers, modified with liquid crystals are used as viable candidates for tissue regeneration to which cells can attach, differentiate and proliferate. As further extension of this work we have synthesized new systems that can enhance the mechanical properties of the elastomers and promote superior, stimuli-responsive surface properties for cell attachment.[2] These materials are currently tested in our labs as ideal platforms for 3D and 4D (3D + time) cell culture models as well as implantable cell supports due to the unique response of these LC elastomers to external mechanical stimuli.
References:
[1] A. Sharma, A. Neshat, C.J. Mahnen, A.d. Nielsen, J. Snyder, T.L. Stankovich, B.G. Daum, E.M. LaSpina, G. Beltrano, Y. Gao, S. Li, B.-W. Park, R.J. Clements, E.J. Freeman, C. Malcuit, J.A. McDonough, L.T.J. Korley, T. Hegmann, and E. Hegmann, Macromolecular Bioscience, 2014, DOI: 10.1002/mabi.201400325.
[2] A. Sharma, C. J. Mahnen, H. R. Everson, A. d. Nielsen, M. Leslie, B. Barnard, B. Kinsel, E. LaSpina, C. Malcuit, L. T. J. Korley, T. Hegmann, and E. Hegmann, Synthesis and mechanical studies of highly tunable biocompatible, biodegradable liquid crystal elastomers as template for tissue regeneration, 2014, manuscript in preparation.

Self-assembly at 2D interfaces is fundamentally different from assembly in bulk 3D systems. The cell&’s lipid membrane is a biological interface where proteins such as clathrin self-assemble into extended networks. The triskelion form of clathrin clearly follows its biological function of endocytosis and inspires potential designs for other complex self-assembled geometries. However, it is difficult to modify and synthesize biological molecules and nanoparticles with precise structure. Lithography and surface functionalization present a simple route to exploring a large variety of self-assembling sub-units that can be rationally designed, offering insight into interfacial self-assembly. We have focused on the assembly of micron scale sub-units mimicking clathrin, using surface tension at 2D interfaces to investigate the assembly of networks of mimics. Due to the precision and adaptability of lithography as a fabrication method, we are able to iterate different shapes as rational extensions of clathrin&’s structure and observe the effects that these changes have on the self-assembly. We can also explore the effect of changing the surface functionalization of the mimics and the impact on their self-assembly, offering insight into designing self-assembly at interfaces.

The interest in light activated materials for releasing small molecules has risen due to the ability to control the timing, location, and amount of release. One example of a small molecule that benefits from photochemical release is Nitric Oxide (NO). NO is a signaling molecule involved in many biological processes, and depending on the concentration, the biological activity changes. High concentrations of NO can signal tumor cell apoptosis; however, low concentration can result in tumor proliferation. Therefore, materials that show light-controlled release of NO are advantageous due to the ability to easily modulate NO release by changing the timing and intensity of light irradiation. Complexes of ruthenium, iron, and manganese have been reported as light activated NO releasing moieties. However, in order for them to be used inside the body, they have to release NO upon red light activation since is the only type of light that can get deep into the skin. Red-light initiated NO release is difficult since the amount of energy provided by the red light is usually not enough to generate the photochemical dissociation.
We are focused on developing metallopolymers that release NO upon red light activation. In order to address the photosensitization of the material toward the red light, we have synthetized several complexes by modifying the ligand frame with specific substituent groups in key positions to lower the energy needed to give release of NO. We then create metallopolymers that contain these metal- ligand moieties. We report new Ru-NO Schiff-base compounds that release NO upon red light activation. These materials can also be regenerated for NO release after exposure to a saturated solution of nitrite. Future work is focused on changing the mechanical properties of the Ru-NO metallopolymers by modifying the polymer matrix.

In the field of nucleic-acid based therapeutics, two major categories are inhibition of the production of deleterious proteins and enhancing gene expression. To date, the most effective way of enhancing protein expression is considered to be the delivery of plasmid DNA although the delivery of messenger RNA (mRNA) has several advantages over the delivery of plasmid DNA in production of therapeutic proteins. Nuclear localization and transcription become unnecessary with utilizing mRNA as gene delivery module, and gene expression can be achieved without a risk of integration into the host genome. These advantages result in rapid expression and cell cycle-independent transfection, which is essential for non-dividing cells. However, messenger RNA-based therapies has been hampered by mRNA susceptibility to nuclease degradation and inability to achieve sufficient expression level. Inspired by methods that can generate extremely long DNA or RNA strands, we report a novel strategy for efficient mRNA delivery by generating nanoparticles made up of mRNA strands with high potency for the production of desired proteins in cells. mRNA nanoparticles (mRNA-NPs) showed enhanced stability of mRNA in physiological conditions and successful expression of green fluorescence protein. Moreover, this approach requires only one-step process to synthesize particles with minimized plasmid DNA to produce RNA transcripts via rolling circle transcription^* for efficient delivery and high cargo capacity. With all these benefits of utilizing mRNA-NPs as a delivery module, it is expected that the mRNA-NP approach will allow the labile nature of mRNA to be overcome in future clinical developments.
*Reference: Han, D., Park, Y., Kim, H. & Lee, J. B. Self-assembly of free-standing RNA membranes. Nature Commun. 5, 4367 (2014).

Metal removal from soil and liquid streams is important in agriculture, mining and many industries for the remediation of heavy metals from wastewater and, increasingly, for recycling valuable metals from mine tailings. However, conventional metal removal methods that rely on physicochemical separation or biosorption suffer from high operational costs, the generation of toxic by-products, and inefficient or non-specific metal capture. We present an alternative strategy for metal removal called BIND (Biofilm-Integrated Nanofiber Display), which uses genetically engineered E. coli biofilms capable of displaying functional peptides at high density on self-assembled extracellular protein nanofibers. We expressed a small library of lanthanide binding peptides with BIND, and developed a biofilm-based assay to examine peptide properties that affected the binding of rare earth metals. Preliminary results showed that the modified biofilms adsorbed lanthanide ions in solution, and we are working on recovering the bound metals with minimal disruption to the biofilm. This approach for selective metal binding using BIND is broadly applicable to the recovery of other precious metals, and to the bioremediation of heavy metals, thus offering a potentially low-cost and sustainable means of metal capture and recovery.

Inspired by nature, researchers have paid increasing attention to bio-molecules as regard to their application in synthesis of inorganic materials nanostructures. Particularly, bio-routes are extremely promising in energy storage area. However, previous works are mainly on anode materials. Rare work has been reported using bio-route for cathode materials synthesis. Monoclinic Li₃V₂(PO₄)₃ (LVP) and Na₃V₂(PO₄)₃ (NVP) are regarded promising as cathode materials in lithium/sodium ion batteries because of their high stability, high theoretical capacity and high operating voltage. However, the low electronic conductivity of LVP and NVP constrained their large-scale application in electric vehicles (EVs). In this work, we demonstrated an artificial-polypeptides-enabled synthesis of ultrafast 3D Li₃V₂(PO₄)₃ and Na₃V₂(PO₄)₃ foam-like porous structures. The artificial polypeptides and LVP/NVP precursors were dissolved in water and mixed on ice, lyophilized, and annealed at 750 #8451; for 10 h in Ar. Techniques such as FESEM, TEM, and XRD were used to characterize the as-synthesized materials. FESEM images showed that the polypeptides are arrayed in an highly ordered crossed way forming macro-pores around 3 µm. LVP/NVP particles are embedded on the inside walls of the porous 3D structure. XRD patterns confirmed that pure well-crystallized Li₃V₂(PO₄)₃ (JCPDF no. 04-012-2044) and Na₃V₂(PO₄)₃ (JCPDF no. 96-222-5133) were obtained. TEM images showed that LVP/NVP spheres were around 100-200 nm and were encased by an amorphous carbon shell which was around 5 nm thick. The overall carbon content derived from the artificial polypeptides was determined by TGA and was found to be about 25 wt%. Control experiments and FTIR results suggested that phosphate ions played an important role in regulating the self assembly of the artificial polypeptides used. This is the first time to report the application of self-assembly of artificial polypeptides in solution rather than aggregation. Unlike 3D graphene, it is a self-linked 3D structure for ultra fast charge/discharge performance to meet the demand of EVs.

Possessing a prominent behavior of reversibly altering its physicochemical characteristics in response to change in temperature, Poly(N-isopropylacrylamide), PNIPAAm, has been thoroughly investigated and its versatility has applied in macroscopic gels, microgels, membranes, sensors, biosensors, thin films, drug delivery, and especially tissue engineering. The cascade of research activities scrutinizing the immense potential of cell sheet engineering has revealed numerous and various methods of fabricating healthy cell sheets for diverse kinds of purpose. However, it is still arduous to manipulate cell sheets during the transplantation process without damaging them. In this regard, we suggest a novel idea of fabricating a transformable hydrogel sheet that can be utilized to eliminate the deterioration of cell sheet product during the transplantation procedure by minimizing human error or contamination.
#8203;In this study, a high-concentrated N-isopropylacrylamide, NIPAAm, monomer solution was polymerized and cross-linked to polyNIPAAm, (PNIPAAm) in a curve-shaped PDMS master mold under the exposure of UV light to inherit its permanent geometrical shape. A fabricated PNIPAAm hydrogel sheet was immersed in warm water for few seconds to temporally change its permanent geometrical shape and the PNIPAAm hydrogel sheet with a temporal shape was then hardened in a standard ambient condition. A finally realized PNIPAAm hydrogel sheet was found to successfully transform from a temporal shape to permanent shape when immersed in water above low critical solution temperature (LCST), 32°C. And lastly, the cell viability on fabricated PINIPAAm hydrogel sheet and the detachment of produced cell sheet were examined. To this end, we herein, with an eager to assuage the grief of patients in modern society, suggest a novel method of utilizing a transformable PNIPAAm hydrogel to precisely transplant cell sheets on a desired area of human body.

In the last two decades, significant efforts have been made to develop soft materials exploiting the self-assembly of short peptides for biomedical applications. So-called β-sheet forming peptides are very attractive for the design of biomaterials, in particular hydrogels [Saiani et al., Soft Matter, 5, 193, 2009]. Due to the “simplicity” of the structure formed at the molecular level, the relative robustness of the β-sheet assembly and the ease of functionalization very stable functional hydrogels can be designed with potential application in a range of fields from tissue engineering [Mujeeb et al. Acta Biomat 2013, 9, 4609 & C Diaz et al. J Tissue Eng 2014, 5, 1-12] and cell culture [Szkolar et al. J Pept Sci 2014, 20, 578] to drug delivery [Roberts at al. Langmuir 2012, 28, 16196 & Tang et al. Int J Pharm 2014, 465, 427]. One particular aspect which has attracted significant interest is the ability to use these systems to design 3D injectable scaffolds for in vivo cell delivery.
Here we present our recent work done on the design of an injectable peptide based hydrogel for the in vivo delivery of cell in the heart. First we have investigated the gelation properties, including injectability, of a β-sheet forming octa-peptide based on the alternation of hydrophobic and hydrophilic residues(FEFEFKFK). Subsequently the suitability of the hydrogel to sustain rat Cardiac Progenitor Cells (CPCs) biological properties was tested in vitro in terms of biocompatibility, cell adhesion and survival. Finally a small animal model was used to explore the potential of this hydrogel as a cell delivery vehicle.
Our work clearly showed that these materials can be used both as 2D and 3D scaffolds for the in vitro culture of CPCs. More interestingly, our in vivo work clearly showed the hydrogel good injectability and the potential of this material as a topical delivery vehicle. Using rhodamine nanoparticles we documented that the hydrogels is retained at the site of injection for at least 7-days. In order to investigate the suitability of the injected hydrogel as a vehicle for CPCs delivery in the heart we used a fluorescent peptide (10mg/ml) loaded with Quantum Dot® labelled cells (10⁵ cell/ml). We documented that the peptide gel was able to retain the “cargo” at the site of injection. Moreover, Quantum Dot® labelled CPCs were detected within the myocardium suggesting the ability of the peptide gel to also support cell homing.
Our work clearly shows the potential of these materials as a 2D and 3D scaffold for the in vitro culture of cardiac progenitor cells. In addition, this peptide gel displays proper injectability as well as good properties for the topical delivery of cells, or even drugs, in the host myocardium. These characteristics suggest a possible future application of this biomaterial as scaffold for cardiac regeneration.
Acknowledgements: The authors are grateful to the EU commission (Grant n0: NMP3-LA-2009-21539 BIOSCENT) for financial support.

The delivery of siRNA for practical nucleic acid-based therapeutics needs to overcome several limitations associated with the nature of RNA. The degradation of RNA by ribonuclease is the one of difficulty for the delivery of siRNA. To address these issues, the carriers for loading siRNA, such as liposomes and cationic polymers, have been used. These carriers can enhance the cellular uptake and protect siRNA from nuclease degradation by forming a complex with siRNA or encapsulating siRNA. Despite these developments, several issues, such as the potential toxicity of complexation agents, non-specific delivery, still remain as problems need to be solved. Here, we report a novel enzymatically synthetic method to produce self-assembled DNA-guided RNA nanovectors for carrier-free siRNA delivery. By novel rolling circle replication method, we can successfully generate nucleic acid-based structures composed of DNA-RNA hybrids. The size and morphology of our products also can be easily controlled by manipulating temperature and time of the reaction. The DNA-RNA hybrids contained within the RNA nanovector can enhance the resistance to nuclease degradation helping to overcome the limitations related to the nature of RNA. In addition to DNA-RNA hybrids, RNA and DNA strands are designed to contain siRNA precursors and aptamers that bind specifically to the target molecules, respectively. The multi-functions from RNA and DNA are readily used for target-specific siRNA delivery by binding to a target cell-surface receptor. With these nucleic acid-based nanostructures, siRNA can be delivered without using transfection agents such as cationic polymers or liposomes.
*Reference: Han, D., Park, Y., Kim, H. & Lee, J. B. Self-assembly of free-standing RNA membranes. Nature Commun. 5, 4367 (2014).

The study of self-assembled rosette nanotubes (RNTs) generated from the guanine-cytosine (GΛC) motif 1 (J. Am. Chem. Soc. 2001, 123, 3854-3855) is an active area in our research group. We have developed an efficient synthetic strategy and self-assembly protocols for Mascal&’s GΛC motif 2, an analogue of 1 that differs by the substitution at the N-atom in the G-ring with a C-atom (J. Org. Chem. 2013, 78, 11421-11426). Here we present the synthesis of the tricyclic GΛC base 3 from R₃ functionalized motif 2 that can form fluorescent RNTs in dimethylformamide. The self-assembly of 3 into RNTs was characterized using scanning electron microscopy, transmission electron microscopy, atomic force microscopy and ultraviolet-visible spectroscopy. The fluorescence properties of self-assembled RNTs in dimethylformamide will also be presented.

The phylum Cnidaria includes marine organisms such as sea anemones, corals and jellyfish. All members of this phylum possess specialized stinging cells, termed nematocysts, used for prey capture, defense and locomotion. Upon stimulation, the nematocyst undergoes explosive release of a lancet-like structure enabled by very high osmotic pressure stored stably in the nematocyst capsule. Past proteomic analysis of the capsule inner wall indicated the presence of small molecular weight structural proteins, termed minicollagens, which organize into a proteinaceous scaffold stabilized by fibril formation and intermolecular crosslinking through disulfide bonds. In order to determine how a crosslinked protein network may function to form an elastic material capable of withstanding extreme pressures, we examine the structural properties of minicollagen-1. Our studies indicate unusual structural features and thermostability, where the stability of minicollagen-1 is modulated through disulfide bond formation. Additionally, striated nanoribbons, with a ~5 nm periodicity, were found to spontaneously form in minicollagen-1 films. These studies show that Cnidarian minicollagen-1 can generate anisotropic, self-organizing materials whose mechanical properties may be modulated by the protein&’s oxidation state.

During implant surgeries, antibacterial agents are needed to prevent bacterial infections, which can cause the formation of biofilms between implanted materials and tissue. Silver nanoparticles, which release silver ions, have been considered to be a promising antibacterial agent because of their broad antibacterial activity. Mussel adhesive proteins (MAPs) derived from marine mussels are bioadhesives that show strong adhesion and coating ability on various surfaces even in wet environment. Here, we proposed a novel surface-independent antibacterial coating biomaterial by incorporating the strong adhesion ability of recombinant mussel adhesive protein into a silver-binding peptide. This sticky recombinant fusion protein enabled the efficient coating on target surface and the easy generation of silver nanoparticles on the coated-surface. The synthesized silver nanoparticles showed excellent antibacterial efficacy against both Gram-positive and Gram-negative bacteria, and also revealed good cytocompatibility with mammalian cells. Moreover, the silver nanoparticles were fully synthesized on various surfaces including metal, plastic, and glass by a simple, surface-independent coating manner, and they were also successfully synthesized on a nanofiber surface fabricated by electrospinning of the fusion protein. Thus, this facile surface-independent silver nanoparticle-generating antibacterial coating biomaterial has great potential to be used for the prevention of bacterial infection in diverse biomedical fields.

Osteoarthritis is a chronic and degenerative condition that causes the structural and functional failure of synovial joints. In particular, a loss in the glycoaminoglycans (GAGs) content occurs, together with the wearing of cartilage tissue. To develop a treatment that could restore the lubrication properties of an injured joint, we took inspiration from the natural components of the synovial fluid. Among them, the main responsible for lubrication are hyaluronic acid and lubricin. The latter shows a central brush-like region extensively modified by O-linked oligosaccharide side chains. Furthermore it binds the cartilage surface and protects it from adsorption of proteins and cells.
Polymer brushes are synthetic analogs of these lubricating components. Brush films obtained from graft-copolymer adsorbates with a polyelectrolite backbones, such as poly-L-lysine (PLL), and polyethylene glycol (PEG) side chains were investigated on metal oxide surfaces as friction reducers. Nevertheless, in vivo applications of PEGs are limited by their thermal enzymatic degradation in physiological media. To overcome these disadvantages we have developed new lubricin-like graft-copolymer adsorbates featuring a biodegradable polyglutamic acid (PGA) backbone, poly-2-(methyl-2-oxazoline) (PMOXA) side chains and oxidized oligosaccharides functions as tissue-adhesive units. In particular, PMOXA presents enhaced stability compared to PEG analougues and forms a biopassive and lubricating brush at the interface. In addition, oxidized oligosaccharides presenting aldehyde functions provide selective anchors for aminolized natural tissue surfaces (i.e. cartilage) via Schiff-base formation.
A series of PGA-α-PMOXAx-β-aldehyde copolymers with different side chain lengths (x) and PMOXA(α)/oligosaccharides(β) grafting densities were successfully synthesized, employing NMR and UV-Vis spectroscopy to precisely address the copolymer architecture.
Graft-copolymer adsorption on aminolized surfaces was investigated at different pH values and temperatures. In order to determine the dry and the hydrated thicknesses of the different films ellipsometry and Quartz Crystal Microbalance with Dissipation (QCM-D) were used. Finally, the interaction of the graft-copolymer films with human serum proteins was studied with QCM-D and the lubricating properties of the formed films were investigated by Colloidal Probe Atomic Force Microscopy (CP-AFM).
Depending on the adsorption conditions and on the graft-copolymer architecture, different film thicknesses were achieved and very low coefficients of friction were observed for the thicker hydrated coatings. In addition, enhanced antifouling properties resulted for the films featuring longer PMOXA side chains. The combination of selective anchoring to aminolized surfaces with high lubricating properties, biocompatibility and protein resistance makes these PGA-α-PMOXAx-β-aldehyde graft-copolymers promising biolubricants for natural tissues.

Photochemical nitric oxide releasing materials were prepared with the complex trans-[Cr(ONO)₂cyclam]C₂₄H₂₀B (CrONO) that had been encapsulated in biocompatible polymer composites (e.g. polydimethylsiloxane, polyurethane). We have demonstrated that effective, biologically relevant amounts of NO can be released upon light irradiation for both controlled (20-100 pmoles/s) and extended durations (>30 hours). Experimental studies focused on modifying methods of encapsulating CrONO into the polymer and quantifying NO release and quantum yield (QY). Modifications included factors such as curing time, curing temperature, and polymer choice. Upon light irradiation with 405nm, measurable nitric oxide (NO) release was detected from these composites in aerated and nitrogen environments. Due to CrONO&’s differing photochemistry in these separate environments, we can gather both a realistic (aerated) and ideal (nitrogen) measurement of NO release. It was determined that porosity of different polymer types greatly influenced the QY of NO release. Furthermore, for these different polymer choices, modifications in film preparation were also highly significant in influencing the QY. Results show that effective, biologically relevant amounts of NO can be released from the solid composite films. In addition, composite materials were prepared with upconverting nanoparticles (UCNPs) and CrONO. Irradiation of these materials showed controlled release of NO after near infra-red (NIR) light excitation. Future work will focus on creating new implantable devices for photochemical NO release in actual biological systems, and testing the materials in actual tissue to evaluate them as a reliable option for nitric oxide release in vivo.

The efficient immobilization of antibodies onto solid surfaces is a vital factor for the sensitivity and specificity of various immunoassays and immunosensors. In the present work, we designed and produced a novel linker protein, BC-MAP, in Escherichia coli by genetically fusing mussel adhesive protein (MAP) with two domains (B and C) of protein A (antibody binding protein) for efficient antibody immobilization on diverse surfaces. Through direct surface coating analyses, we found that BC-MAP successfully coated diverse surfaces including glass, polymers, and metals, but the BC domain alone did not. Importantly, antibodies were efficiently immobilized on BC-MAP-coated surfaces, and the immobilized antibodies interacted selectively with their corresponding antigen. Quartz crystal microbalance analyses showed that BC-MAP has excellent antibody-binding ability compared to BC protein on gold surfaces. These results demonstrate that the MAP domain, with uniquely strong underwater adhesive properties, plays a role in the direct and efficient coating of BC-MAP molecules onto diverse surfaces lacking any additional surface treatment, and the BC domain of BC-MAP contributes to the selective and oriented immobilization of antibodies on BC-MAP-coated surfaces. Thus, our BC-MAP fusion protein could be a valuable novel linker material for the facile and efficient immobilization of antibodies onto diverse solid supports.

With the advent of DNA-progammable assembly techniques, nanoparticle superlattices with well-defined geometries, easily tunable lattice parameters, and distinct three-dimensional supercrystals can be synthesized. Despite being constructed from semi-flexible polymers (i.e. oligonucleotides), these materials are extraordinarily well-defined; particles are positioned in these crystals with angstrom-level precision. This implies that DNA-nanoparticle superlattices might be well suited for a platform to elucidate detailed structural and thermodynamic information about the interactions between small molecules and the oligonucleotides that hold the lattices together. In this work, a novel method is introduced for probing the molecular intercalation interactions between DNA and a family of [Ru(dipyrido[2,3-a:3&’,2&’-c]phenazine)]²⁺-based compounds using DNA-programmable nanoparticle superlattices. Using small angle X-ray scattering, the extent of elongation upon intercalation of the DNA is resolved with sub-nanometer resolution. In addition to structural information, these materials are also suitable for revealing thermodynamic information, as DNA-nanoparticle superlattices exhibit characteristically sharp melting transitions that are sensitive to subtle changes in the nature of the DNA duplex. Small molecule intercalation is known to enhance DNA duplex stability. By systematically studying a series of intercalators with ancillary ligands that differ in electrostatic and steric character, we show that the relative contributions of each with respect to the intercalation event can be determined. In our study, we demonstrate that the identity of the ancillary ligands affects the relative affinity of the compounds for DNA duplexes. Comparing the stability of superlattices after intercalation with varying concentrations of complex, we demonstrate that DNA-nanoparticle crystals intercalated with compounds containing the least bulky ligand and highest overall charge were stabilized to the greatest extent. This platform also offers the ability to easily tailor the DNA to study the effect of sequence and length on intercalation. This technique can be a highly versatile tool that can aid in the rational design of intercalator-based chemical probes and sensors useful for investigating a variety of biochemical processes.

Collagen is the main component of many very robust natural materials and some manufactured materials. The strength of the material is normally one of the key properties required in the natural or technological application. The basis for strength in collagen materials is not fully understood. We used small angle X-ray scattering to investigate the collagen fibril structure in leather, pericardium, and surgical scaffold collagen matrix materials and to compare this with tear strength of these materials. This is combined with atomic force microscopy, histology, electron microscopy and other techniques. We discover a complex relationship between strength and a number of structural factors including fibril orientation, fibril diameter and cross linking. These can be related to tissue type, species, and age of the animal. While the picture is far from complete we have made progress on models for structure and strength in collagen materials that can assist in the preparation of synthetic analogues of natural tissue.

Self-assembled peptides that undergo hydrogelation via β-sheet fibrillization are a well-described platform for creating synthetic mimics of the extracellular matrix (ECM), and they are also attractive as peptide-based vaccines. However, these materials have been significantly limited by their being composed primarily of short peptides, lacking the precise biofunctionality afforded by folded proteins. Recently, we developed a new strategy for creating self-assembled materials from defined sets of expressed proteins based on a self-assembling fusion domain we term a “β-tail”, which enables the integration of expressed proteins into β-sheet peptide nanofibers. In the present study, we demonstrate two new applications using this hybrid protein/peptide self-assembling platform: integrating folded cell attachment domains into peptide nanofibers and gels for 3D cell culture, and integrating immunomodulating cytokines into the materials. The first example focused on prostate cancer cells, which are both difficult to culture and inefficient at establishing tumors in mice. Matrigel, commonly used for the 3D cell culture of prostate cancer cells, has many shortcomings including its lack of chemical definition and its lack of fibronectin (FN), a major ECM protein present in stromal tissues that mediates cell attachment and is known to be important for the survival of many prostate cancer cell lines. To generate defined peptide gels containing precise quantities of FN domains, we designed β-tail-FNIII(9-10) by molecular cloning. The proteins were expressed in E. coli and characterized by SDS-PAGE and Western blotting. β-tail-FN was capable of integrating within self-assembled peptide nanofibers, illustrated with pulldown assays, SDS-PAGE, and western blots. For LNCaP, a human prostate cancer cell line, β-tail-FN improved both cell attachment and spreading compared to surfaces lacking β-tail-FN. Towards a second application using β-tail proteins for immunomodulation, we designed nanofibers that displayed interferon-γ (IFN-γ) using the β-tail platform. IFN-γ is an important cytokine for the polarization of T cells and is potentially useful for augmenting immune responses to peptide vaccines. β-tail-IFN-γ was cloned and expressed, and it co-assembled into peptide nanofibers via the the β-tail tag, as determined by ELISA. The bioactivity of the materials was verified in macrophage cultures. This work illustrates a strategy for the production of self-assembled nanofibers that contain proteins retaining their native folds and biological activities. This platform is likely to enable the development of protein-presenting self-assembled hydrogels for diverse biomedical and biotechnological applications ranging from vaccine development to tissue engineering.

Bioinspired trans-membrane channels have been developed using various techniques, such as peptide chemistry, DNA origami, or nanotubes cutting, but challenges still remain to achieve the desired affinity, transport properties and biocompatibility. We have recently developed ultra-short biocompatible artificial channels based on carbon nanotubes with the dimension of 5-15 nm in length and 1.5 nm in diameters. These CNT porins incorporate into model lipid bilayer and live cell membranes, and form a well-defined trans-membrane channel. We also explored the concentration-dependent interaction of the CNT porins with CHO cells using microscopy and OmniLog phenotype microarray system. Interestingly, the CNT porins didn&’t inhibit the cell viability at low concentration over a 72 hr co-incubation period. CNT porins could be established as a promising biomimetic platform for developing cell interfaces, studying transport in biological channels, and creating stochastic sensors.

The main bottleneck of current polymeric porous membranes is to simultaneously optimize flux and selectivity for molecular separations. It was proposed that a thin membrane consisting of a high-density array of functionalized through-channels oriented normal to the film&’s surface could achieve enhanced transport and separation properties. We recently developed a one step process to direct the growth of polymer-conjugated cyclic peptide nanotubes (CPNs) within a cylindrical morphology block copolymer (BCP) template for fabricating membranes with sub-nanometer interiors. Moreover by replacing the backbone sequence of the cyclic peptides (CPs) with artificial amino acids, the channel size and the interior functionalities of the CPNs can be modified, thus allowing molecular control over the separation process. Here we report recent efforts to modulate the thickness of the resultant BCP/CPN selective layer while maintaining the vertical orientation of the cylinders to control the membrane thickness and the CPN density simultaneously. Being able to tune the membrane thickness adds flexibility to the design and allows for increased mechanical stability and integrity.

Recently, there has been great interest in the potential use of biomolecules, DNA in particular, to facilitate the assembly of functional nanostructures. DNA is a natural nanoscale material that self-assembles according to precise base pairing rules. This property, coupled with DNA&’s structural features, has recently been exploited to create a wide range of DNA nanostructures for a variety of different applications in nanoscience and nanotechnology. In order to fully exploit the potential of DNA as a structural material, and in particular as a template for building working devices at the nanoscale, it is of crucial importance to control the position and orientation of DNA nanostructures on substrates.
Here we present different approaches towards the controlled and ordered assembly of 1D nano-objects from solutions to surfaces. This is achieved via the combination of high resolution patterning with selective end-functional chemistry. In particular we have used a 1D rigid DNA motif as a model for studying directed assembly at the molecular scale onto lithographically patterned nanodot anchors. By matching the inter-nanodot spacing to the length of the DNA nanostructure, we achieved nearly 100% placement yield. By varying the length of single-stranded DNA linkers bound covalently to the nanodots, we were able to study the binding selectivity as a function of the strength of the binding interactions. We further analyzed the binding in terms of a thermodynamic model which provides insight into the bivalent nature of the binding. Moreover, using the same basic approach, we have begun studying the precise organization of nanotubes on surfaces, via their selective binding to nanoscale anchors.
Our findings are of general interest for the controlled assembly of a broad range of functional nanostructures, towards the fabrication of solution-processable nanoscale devices.

DNA is an attractive candidate for nanoparticle assembly, due to its length, sequence, and chemical programmability. To date, lattices of over 20 different well-defined symmetries of varying nanoparticle composition and lattice parameter have been designed and constructed using DNA-directed assembly techniques. Moreover, high quality, three-dimensional crystal habits (i.e. rhombic dodecahedra supercrystals from body-centered cubic superlattices) can be assembled through slow cooling of solutions of DNA-functionalized nanoparticles with complementary sequences. In all cases, the thermal stability of these structures is dictated by the strength of hybridization interactions occurring between the oligonucleotides that hold the lattices together. While structures with high thermal stability are desirable for certain applications (e.g., catalysis, optics, biological detection), the formation of well-ordered superlattices is dependent upon oligonucleotide interactions that are sufficiently weak so as to allow for dynamic reorganization during thermal annealing. Thus, in general superlattices are unstable above 50°C. In this work, we present the use of ruthenium(II) based DNA intercalators to post-synthetically modify the DNA-assembled superlattices in a non-covalent manner, dramatically increasing their resistance to thermal degradation. Crucially, these intercalated crystal lattices retain order at temperatures up to 60% higher than when unintercalated. In addition, it is possible to tune the intercalator-DNA interaction strength through structural modulation of the intercalator molecule. This effect translates globally into DNA-nanoparticle superlattices of increasing thermal stability. Finally, we demonstrate the use of this method to chemically “staple” DNA-nanoparticle superlattice single crystals for the synthesis of core-shell superlattices. In a method analogous to seed-mediated nanoparticle growth, intercalated superlattices are overgrown with subsequent layers of particles through thermal annealing. This technique enables the synthesis of increasingly sophisticated supercrystals with properties potentially useful for plasmonic, photonic and catalytic applications.

Single-stranded oligonucleotides called aptamers bind to non-nucleotide targets with a specificity and affinity that rival that of antibodies. Numerous DNA aptamers have been identified for biological targets such as soluble proteins and immobilized cell receptors for applications ranging from drug delivery to biosensors. Nonbiological materials such as colloidal particles, however, have received far less attention as a potential target species for aptamer screening and implementation. Furthermore, 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. Here, efforts towards screening, identification and characterization of DNA aptamers that bind to (1) gold nanorods or (2) gold nanospheres are highlighted. In contrast to conventional SELEX-based screening, we employ a non-SELEX screening approach to enable faster screening and minimize any bias towards early rounds of winning candidates. Analysis of the resulting aptamer sequences for gold nanorods and nanospheres reveals that consensus motifs are not common. Analysis of the predicted intrastrand or secondary structures of all identified aptamers, however, reveals common structural motifs that are shared among seemingly unrelated sequences. Ultimately, by extending our aptamer screening efforts to include colloidal materials that can serve as drug carriers or as sensor substrates, we hope to broaden the implementation of aptamers as bio-inspired ligands in materials-related applications.

Cells consist of organized assemblies of macromolecules that dynamically rearrange to execute their functions. Considerable research progress has been made towards constructing synthetic nanostructures that assemble molecular components with different functionalities. But to achieve the level of versatility that cells exhibit, these synthetic nanostructures need to be capable of dynamic behavior. In this work we present the experimental characterization of RNA nanotubes with the potential for dynamically controllable assembly and disassembly.
The use of nucleic acids to build materials has primarily focused on DNA as it is well characterized, easy to synthesize, and low in cost. However, RNA can be encoded into genes and produced by cells, enabling us to program and control intracellular assembly processes¹. RNA is similar to DNA structurally and chemically: we can use it to create nanostructures similar to those built with DNA and utilize the rich variety of tertiary motifs to produce complex and functional nanostructures² and RNA aptamers that can target wide variety of ligands³.
We created, for the first time, double-crossover (DX) tiles made out of purely RNA strands that assemble into nanotubes, starting from previously proposed DNA/RNA hybrid DX tiles⁴. The tiles interact through#8232; Watson-Crick base pairing at “sticky end” domains in a tessellating manner and form RNA nanotubes. We were able to produce RNA nanotubes not only with gel extracted and purified RNA strands, but also with a one-pot co-transcriptional anneal protocol, without extractions. We found that these structures have a unique kind of chirality and are left-handed. This feature presents us with greater potential for spatial control that could be achieved using these nanotubes. Furthermore, we created RNA tiles with toeholds that assemble into tubes to permit toehold-mediated branch migration⁵. This concept has been widely used to create dynamics in DNA circuits and we aim to use it to generate dynamics in RNA nanostructures. Suitable RNA strands acting as “decay” and “recovery” inputs will govern the disassembly and reassembly of RNA nanotubes, a pathway we already demonstrated in DNA nanotubes. Implementing dynamics in chiral RNA nanotubes will allow us to create optically active and inactive material by combining tube growth-decay dynamics with gold nanoparticles⁶. These dynamic nanomaterials may be eventually produced in cellular microfactories.
References
1. Delebecque, CJ., et al. Science 333.6041 (2011): 470-474.
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One-dimensional organic nanowires have emerged as idealized model systems for investigating charge transport mechanisms at molecular length scales. However, there are significant difficulties associated with the synthesis and electrical characterization of well-defined organic nanowires. By drawing inspiration from oligonucleotide synthesis, we have developed a facile strategy for the assembly of organic semiconductor building blocks in predetermined arrangements on a DNA-like backbone. Not only can the resulting constructs be purified/processed under partially aqueous conditions via known biochemical techniques, but also they feature many of the advantages of standard oligonucleotides, including a well-defined length, geometry, and sequence context. We have self-assembled monolayers of our nanowires on gold substrates and investigated their charge transport properties with electrochemical techniques. Our findings hold significance both for fundamentally understanding nanoscale charge transport phenomena and for the development of new types of biological and molecular electronic devices.

Protein self-assembly is a commonplace phenomenon in living systems and is frequently responsible for building molecular machines that carry out the vast array of functions, such as molecular separation and selective ion transport. Inspired by in nature, various proteins and peptides have been designed and exploited for self-assembly of functional materials in vitro. However, the application of these protein- and peptide-based materials is limited because of their poor stabilities against thermal and chemical degradation. Therefore, there is a great need to develop protein-like synthetic polymers that can function like proteins and peptides for molecular recognition and self-assembly, but exhibit high stabilities. There are several known chemical systems that can create non-natural, sequence-specific polymers, such as b-peptides and peptoids (poly-N-substituted glycines). Peptoids have received particular attention because they can be cheaply and efficiently synthesized, and several hundred commercially available amines can be used to build their large side-chain diversity. We recently demonstrated that peptoids were able to mimic peptides commonly present in natural biominerals for unprecedented control over both calcite morphology and growth kinetics.
In this presentation, we report our progress in exploiting peptoids to mimic proteins and peptides for self-assembly. Specifically, we demonstrate that 12-mer peptoids are able to self-assemble into highly-ordered membrane-like materials both in solution and on substrate surfaces. In aqueous solution, these peptoids self-assemble into highly-crystalline and free-floating nanosheets through a solvent-driven crystallization process. These nanosheets have single-bilayer thickness (3.2 nm) and large area (up to mm²). X-ray diffraction data indicate that these peptoids are highly packed through π-π stacking and peptoid side-chain hydrogen bonding. These results represent the smallest peptoid oligomers that self-assemble into free-floating nanosheets and do not require the compression of monolayers formed at the water-air interface. The formation of single-bilayer-thick nanosheets also occurs on various substrate surfaces. For example, on freshly-cleaved mica surface, we observed that nanosheets were formed through a heterogeneous nucleation process. Similar nanosheets were assembled even when 12-mer peptoids were specifically conjugated with functional groups, indicating that self-assembly of 12-mer peptoids into nanosheets is robust, and these nanosheets can serve as a well-defined 2D platform for post-functionalization. Peptoid self-assembly is highly sequence-specific, and pH sensitive. When the diblock-like 12-mer peptoids are switched to an alternative motif, the resulting 12-mers only self-assemble into fiber-like materials. Multi-scale simulations are also used to provide insights into peptoid-assembly mechanisms.

Introduction
Mesenchymal stem cells (MSCs) have potential use as cell-based therapies in regenerative medicine for promotion of angiogenesis through the secretion of pro-angiogenic factors. The MSC secretome has been shown to be modulated by a variety of factors¹, including mechanical properties. We have shown previously that extracellular matrix stiffness and composition has a considerable effect on the MSC secretome and its pro-angiogenic properties². Here, we extend this work using a dynamic magnetically-tunable hydrogel to study the effects of modulation of hydrogel physical properties on MSCs and their angiogenic potential.
Materials and Methods
MSCs were cultured on hybrid hydrogels consisting of magnetic iron oxide particles embedded in a polyacrylamide matrix with fibronectin chemically tethered to the surface. The hydrogels were 'switched' between soft and stiff conditions by placing them under a magnetic field as shown previously³. Conditioned media from these surfaces was used in a functional angiogenesis assay using human microvascular endothelial cells (hMVECs) on matrigel^2,4. MSC morphology and marker expression were studied using fluorescence microscopy. HMVEC angiogenesis was analyzed by quantitating tubulogenesis in a 3D matrigel assay in the presence of conditiond media for MSCs. The conditioned media was also analyzed for cytokine expression using western blotting and real time PCR.
Results
The introduction of a magnetic field, stiffening the hybrid hydrogels, caused a marked increase in cultured MSC area. This change is shown to be reversible after removal of the magnetic field. Long term culture showed magnetic field had an effect on MSC differentiation outcomes.
Conditioned media from MSCs cultured under a magnetic field showed higher angiogenic potential than those cultured without. Analysis of the conditioned media from these conditions showed differences among the secretory profiles of the MSCs.
Discussion and Conclusions
There is a large potential for the therapeutic use of MSCs, however their full potential remains unrealized. The extracellular environment of MSCs affects their behavior and dynamically modulated hydrogels give a chance to further investigate the role of mechanical environment especially with the ability to introduce temporal and reversible changes to that environment. This system may further be useful in optimizing the secretory profile of MSCs for cellular therapies for angiogenesis.
References
1. S. H. Ranganath, O. Levy, M. S. Inamdar, and J. M. Karp, Cell Stem Cell, 2012, 10, 244-258.
2. A. A. Abdeen, J. B. Weiss, J. Lee, and K. A. Kilian, 2014, 20, 2737-2745.
3. T. Mitsumata, A. Honda, H. Kanazawa, and M. Kawai, J. Phys. Chem. B, 2012, 116, 12341-8.
4. G. Kasper, N. Dankert, J. Tuischer, M. Hoeft, T. Gaber, J. D. Glaeser, D. Zander, M. Tschirschmann, M. Thompson, G. Matziolis, and G. N. Duda, Stem Cells, 2007, 25, 903-910.

Protein-based biomaterials have emerged as powerful tools for tissue engineering applications. Recombinant DNA techniques can be used to precisely tune material properties at the molecular level, and multiple peptide modules can be incorporated into a single material. In our work, we have developed a family of modular protein biomaterials composed of bioactive domains and resilin structural repeats. Resilin is an elastic protein with high resilience, low stiffness, and a high fatigue lifetime, which makes it ideal for use in repetitive environments. We have included a number of bioactive peptides to promote cell adhesion or stem cell differentiation. In particular, we have created a family of proteins containing a peptide derived from bone morphogenetic protein-2 (BMP-2) and have shown that these protein microenvironments accelerate bone differentiation. Another family of proteins include a peptide that mimics vascular endothelial growth factor (VEGF), and these engineered proteins promote endothelial differentiation of mesenchymal stem cells. Thus, our studies demonstrate that cell responses, such as cell differentiation, can be modulated through the design of our protein-engineered microenvironments.

Here we reveal the first generation of custom 3D virus materials capable of control over various length scales. Columns, boxes, cantilevers, arches and bridges, among other virus architectures, are produced via a 3D writing technique utilizing a capillary filled with virus suspension. Virus architectures are generated from the tip by contacting a substrate to form a liquid bridge and freely moving the tip to leave behind a dynamic front of solidified virus. At high virus concentration, the inherent nematic, cholesteric and smectic ordered liquid crystal phase is enriched to provide enhanced stability, thereby allowing the architectures to be fabricated even at fast writing speeds. By varying the tip speed and virus concentration, we find that the morphology can adopt surface modes including smooth cylinders, peristaltic undulations, as well as helices. Using this unique class of 3D virus material, actuating and sensing applications are demonstrated, thus offering the combined benefits of both biochemical and micro electromechanical systems. Furthermore, we were trying to substantiate photo responsive switching structures from modified virus. Using chemical coupling of azobenzene derivatives to M13 virus allowed for UV-driven changes in confirmation and hence structures built from these virus building for nano scale switching (actuating) applications.

Natural structural materials often exhibit novel properties including high strength, energy absorption, flexibility and biocompatibility due to unique physical and chemical interactions among their bimolecular components. In the same way, chitin-containing structural materials such as insect cuticles and crustacean shells owe their outstanding properties to the intimate interactions of chitin nanofibers with proteins such as fibroin, elastin, abductin, and collagen. Reproducing these novel properties through engineering the bioinspired composites has been difficult due to the insolubility of chitin in common solvents. In the present work, we introduce high performance composite elastic substrates produced by the solution self-assembly of 3nm chitin nanofibers co-assembled in bovine gelatin matrix derived from collagen. These elastic chitin nanofiber-gelatin substrates are unique in that they have higher strength compared to pure gelatin yet maintaining its flexibility and elasticity. These reinforced hydrogels may find applications in tissue engineering.