Metal vanadium phosphates (MVP), particularly Li3V2(PO4)3 (LVP) and Na3V2(PO4)3 (NVP), are regarded as the next-generation cathode materials in lithium/sodium ion batteries. These materials possess desirable properties such as high stability, theoretical capacity, and operating voltages. Yet, low electrical/ionic conductivities of LVP and NVP have limited their applications in demanding devices such as electric vehicles. In this work, a novel synthesis route for the preparation of LVP/NVP micro/mesoporous 3D foams via assembly of elastin-like polypeptides is demonstrated. The as-synthesized MVP 3D foams consist of microporous networks of mesoporous nanofibers, where the surfaces of individual fibers are covered with MVP nanocrystallites. TEM images further reveal that LVP/NVP nanoparticles are about 100-200 nm in diameter, with each particle enveloped by a 5 nm thick carbon shell. The MVP 3D foams prepared in this work exhibit ultrafast rate capabilities (79 mA h g(-1) at 100C and 66 mA h g(-1) at 200C for LVP 3D foams; 73 mA h g(-1) at 100C and 51 mA h g(-1) at 200C for NVP 3D foams) and excellent cycle performance (almost 100% performance retention after 1000 cycles at 100C); their properties are far superior compared to current state-of-the-art active materials.
Despite the advanced detection and sterilization techniques available today, the sensitive diagnosis and complete elimination of bacterial infections remain a significant challenge. A strategy is reported for efficient bacterial capture (ca. 90%) based on the synergistic effect of the nanotopography and surface chemistry of the substrate on bacterial attachment and adhesion. The outstanding bacterial-capture capability of the functionalized nanostructured substrate enables rapid and highly sensitive bacterial detection down to trace concentrations of pathogenic bacteria (10 colony-forming units mL(-1)). In addition, this synergistic biocapture substrate can be used for efficient bacterial elimination and shows great potential for clinical antibacterial applications.
The lithium oxygen (Li−O 2 ) battery is one of the most promising technologies among various electrochemical energy storage systems. The challenge to develop a highperformance Li−O 2 battery lies in exploring an air electrode with optimal porous structure and high efficient bifunctional electrocatalyst. The present work demonstrates a bioinspired synthesis route for the preparation of high performance Li−O 2 air electrode materials that are made out of N-doped carbon foams decorated with heteronanostructured MoO 2 /Mo 2 C nanocrystals (MoO 2 /Mo 2 C@3D NCF). Here, recombinant proteins (ELK16-FLAG) facilitated the self-assembly of metal precursors and provided a carbon source for Mo 2 C formation. The as-prepared MoO 2 /Mo 2 C@3D NCF showed superior electrocatalytic activity in both oxygen evolution reaction and oxygen reduction reaction mechanisms with a high round-trip efficiency of 89.1% (2.77 V/3.11 V) at 100 mA g −1 as well as exceptional rate performances and good cyclability in Li−O 2 battery. The desirable electrochemical performance can be attributed to the unique hierarchical porous structure of the 3D carbon foam and the intimate contact between MoO 2 and Mo 2 C nanocrystals. We demonstrate that the novel, facile, environmentally friendly bioinspired approaches would open new avenues for the synthesis of 3D nitrogen doped carbon supported advanced functional materials with excellent electrochemical performances.
Described herein is the efficient synthesis and evaluation of bioactive arginine-glycine-aspartic acid (RGD) functionalized polynorbornene based materials for cell adhesion and spreading. Polynorbornenes containing either linear or cyclic RGD peptides were synthesized by ring-opening metathesis polymerization (ROMP) using the well-defined ruthenium initiator [(H2IMes)(pyr)2(Cl)2Ru=CHPh]. The random copolymerization of three separate norbornene monomers allowed for the incorporation of water-soluble polyethylene glycol (PEG) moieties, RGD cell recognition motifs, and primary amines for post-polymerization cross-linking. Following polymer synthesis, thin-film hydrogels were formed by cross-linking with bis(sulfosuccinimidyl) suberate (BS3), and the ability of these materials to support human umbilical vein endothelial cell (HUVEC) adhesion and spreading was evaluated and quantified. When compared to control polymers containing either no peptide or a scrambled RDG peptide, polymers with linear or cyclic RGD at varying concentrations displayed excellent cell adhesive properties in both serum-supplemented and serum-free media. Polymers with cyclic RGD side chains maintained cell adhesion and exhibited comparable integrin binding at a 100-fold lower concentration than those carrying linear RGD peptides. The precise control of monomer incorporation enabled by ROMP allows for quantification of the impact of RGD structure and concentration on cell adhesion and spreading. The results presented here will serve to guide future efforts for the design of RGD functionalized materials with applications in surgery, tissue engineering, and regenerative medicine.
The processes of wound healing and collective cell migration have been studied for decades. Intensive research has been devoted to understanding the mechanisms involved in wound healing, but the role of cell-substrate interactions is still not thoroughly understood. Here we probe the role of cell-substrate interactions by examining in vitro the healing of monolayers of human corneal epithelial (HCE) cells cultured on artificial extracellular matrix (aECM) proteins. We find that the rate of wound healing is dependent on the concentration of fibronectin-derived (RGD) cell-adhesion ligands in the aECM substrate. The wound closure rate varies nearly sixfold on the substrates examined, despite the fact that the rates of migration and proliferation of individual cells show little sensitivity to the RGD concentration (which varies 40-fold). To explain this apparent contradiction, we study collective migration by means of a dynamic Monte Carlo simulation. The cells in the simulation spread, retract, and proliferate with probabilities obtained from a simple phenomenological model. The results indicate that the overall wound closure rate is determined primarily by the rate at which cells cross the boundary between the aECM protein and the matrix deposited under the cell sheet.biomaterials | integrins | elastin T he collective migration of cells is fundamental to wound healing, morphogenesis, and many bioengineering applications. Wound healing in particular involves the migration of cell sheets over adhesive surfaces. Two mechanisms of migration have been identified in wound healing (1). First is the "purse string" mechanism in which a marginal actomyosin cable develops along the wound edge, and wound closure proceeds with contraction of the actin belt (2). The second mechanism involves active spreading and migration of cells at the wound edge, known commonly as "lamellipodial crawling." The latter mechanism is more frequently observed in vitro and has been characterized by using scratch-wound models. In these models, cells experience an injury, which triggers cell migration through various biochemical signaling events (3). It has also been argued that the availability of free space is sufficient to initiate cell migration in the absence of mechanical injury (4-6). Upon wounding, proliferation is up-regulated (7).Adhesive cell-substratum interactions are required for sustained migration into the wound area (8, 9). The rates of migration of individual cells are governed by surface adhesivity in a biphasic fashion, at least under certain conditions (10). Surfaces modified with adhesion ligands such as fibronectin (FN) (11-13) and Arg-Gly-Asp (RGD) peptides have been shown to facilitate wound healing, and it is reasonable to infer that the observed increases in healing rates arise primarily from faster migration of individual cells. We show here that other factors can be more important.The substrates used in this work were prepared from artificial extracellular matrix (aECM) proteins that combine domains derived from fibronec...
Keywords wound healing; PHSRN; RGD; extracellular matrix; artificial proteinsThe discovery of the cell-adhesive properties of the Arg-Gly-Asp (RGD) sequence located in the 10 th type III domain of fibronectin triggered widespread use of RGD-functionalized materials for directing cell behavior. [1][2] In studies of cell adhesion and migration, however, cell responses on RGD surfaces are never identical to those observed on fibronectin.[3] For example, we recently examined the attachment and patterning of Rat-1 fibroblasts on elastin-based artificial extracellular matrix (aECM) proteins bearing a fibronectin-derived RGD sequence, and found the average projected area of such cells to be approximately 60% of those spread on fibronectin.[4] We wondered whether it might be possible to elicit more nearly authentic cell responses by engineering aECM proteins that preserve the domain structure of fibronectin. Fibronectin type III domains 9 and 10 are ideal for such studies; the domains are relatively small (ca. 90 amino acids), and the PHSRN sequence derived from domain 9 has been reported to increase cell adhesion to RGD peptides derived from domain 10.[5] Garcia and coworkers have reported enhanced cell adhesion strength, signaling and proliferation on surfaces bearing tethered fibronectin fragments comprising domains 7-10, [6] and Ratner and Jiang have observed striking differences in the orientation and functionality of such fragments adsorbed on positively and negatively charged monolayer surfaces. [7] Fusion proteins containing fibronectin fragments have also been prepared. Mardon and Grant showed in 1994 that domains 9 and 10 support cell adhesion when fused to glutathione S-transferase.[8] More recently, Mrksich and coworkers completed a thorough study of cell adhesion to domains 9 and 10 immobilized as cutinase fusions on self-assembled alkanethiol monolayers.[9]Here we report a genetic strategy to prepare elastin-based aECM proteins bearing full-length fibronectin domains. Each aECM protein carries a central cell-binding domain (CBD) flanked by relatively long (125-amino acid) elastin-like domains (Figure 1a) that contain lysine residues to facilitate crosslinking and fabrication of viscoelastic materials with tunable moduli. [10][11][12] For simplicity, each aECM protein is identified by its CBD.
Cell-matrix interactions play critical roles in regulating cellular behavior in wound repair and regeneration of the human skin. In particular, human skin keratinocytes express several key integrins such as alpha5beta1, alpha3beta1, and alpha2beta1 for binding to the extracellular matrix (ECM) present in the basement membrane in uninjured skin. To mimic these key integrin-ECM interactions, artificial ECM (aECM) proteins containing functional domains derived from laminin 5, type IV collagen, fibronectin, and elastin are prepared. Human skin keratinocyte cell responses on the aECM proteins are specific to the cell-binding domain present in each construct. Keratinocyte attachment to the aECM protein substrates is also mediated by specific integrin-material interactions. In addition, the aECM proteins are able to support the proliferation of keratinocyte stem cells, demonstrating their promise for use in skin tissue engineering.
A facile approach for the synthesis of 3D hybrid metal fluoride@N,F-carbon foams using metal-binding elastin-like recombinant proteins as the template is demonstrated.
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