Bioinspired Synthesis of Hierarchically Porous MoO₂/Mo₂C Nanocrystal Decorated N‑Doped Carbon Foam for Lithium–Oxygen Batteries

The lithium oxygen (Li–O₂) battery is one of the most promising technologies among various electrochemical energy storage systems. The challenge to develop a high-performance Li–O₂ 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–O₂ air electrode materials that are made out of N-doped carbon foams decorated with heteronanostructured MoO₂/Mo₂C nanocrystals (MoO₂/Mo₂C@3D NCF). Here, recombinant proteins (ELK16-FLAG) facilitated the self-assembly of metal precursors and provided a carbon source for Mo₂C formation. The as-prepared MoO₂/Mo₂C@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–O₂ battery. The desirable electrochemical performance can be attributed to the unique hierarchical porous structure of the 3D carbon foam and the intimate contact between MoO₂ and Mo₂C 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

Probing the Role of Integrins in Keratinocyte Migration Using Bioengineered Extracellular Matrix Mimics

Bioengineered extracellular matrix (ECM) mimetic materials have tunable properties and can be engineered to elicit desirable cellular responses for wound repair and tissue regeneration. By incorporating relevant cell-instructive domains, bioengineered ECM mimics can be designed to provide well-defined ECM-specific cues to influence cell motility and differentiation. More importantly, bioengineered ECM surfaces are ideal platforms for studying cell–material interactions without the need to genetically alter the cells. Here, we showed that bioengineered ECM mimics can be employed to clarify the role of integrins in keratinocyte migration. Particularly, the roles of α5β1 and α3β1 in keratinocytes were examined, given their known importance in keratinocyte motility. Two recombinant proteins were constructed; each protein contains a functional domain taken from fibronectin (FN-mimic) and laminin-332 (LN-mimic), designed to bind α5β1 and α3β1, respectively. We examined how patient-derived primary human keratinocytes migrate when sparsely seeded as well as when allowed to move collectively. We found, consistently, that FN-mimic promoted cell migration while the LN-mimic did not support cell motility. We showed that, when keratinocytes utilize α5β1 integrins on FN-mimics, they were able to form stable focal adhesion plaques and stabilized lamellipodia. On the other hand, keratinocytes on LN-mimic utilized primarily α3β1 integrins for migration and, strikingly, cells were unable to activate Rac1 and form stable focal adhesion plaques. Taken together, employment of our bioengineered mimics has allowed us to clarify the roles of α5β1 and α3β1 integrins in keratinocyte migration, as well as further provided a mechanistic explanation for their differences

Synthesis and Cell Adhesive Properties of Linear and Cyclic RGD Functionalized Polynorbornene Thin Films

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 postpolymerization 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