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Polymer nanocomposites containing metal nanoparticles can be prepared by different methods: mechanical mixing of a polymer with metal nanoparticles; in situ polymerization of a monomer in the presence of metal nanoparticles; or in situ reduction of metal salts or complexes in a polymer [8,9] . These polymer nanocomposites have attracted a great deal of attention due to their unique properties and applications [10,11] . The literature describes many methods to prepare ultrafine silver powders [12][13][14][15] including the formation of Ag nanoparticles attached to bacterial cellulose [2,3] . In this work, we developed an easy method to produce composites with homogeneous size distribution of silver nanoparticles. This structure provides a robust, highlyporous and self-sustaining structure with large surface area, which is essential to facilitate incorporation of the silver ions in the metallization process to give a high silver loading content. Furthermore, the in situ direct metallization method was adopted to obtain a high loading content and strong bonding force of silver nanoparticles on the BC surface, thereby avoiding the Ag + contamination problem. The combination of the antibacterial efficacy of the silver nanoparticles and the biodegradability of the BC fibers in the composite fibers can make them practical for use as antimicrobial membranes in medical applications. Experimental MaterialsThe bacterial cellulose (BC) membranes were supplied by Fibrocel -Produtos Biotecnológicos Ltda. (Ibiporã, Brazil). Polyvinylpyrrolidone (PVP, MW = 29,000), gelatin,

The quest for an ideal biomaterial perfectly matching the microenvironment of the surrounding tissues and cells is an endless challenge within biomedical research, in addition to integrating this with a facile and sustainable technology for its preparation. Engineering hydrogels through click chemistry would promote the sustainable invention of tailor-made hydrogels. Herein, we disclose a versatile and facile catalyst-free click chemistry for the generation of an innovative hydrogel by combining chondroitin sulfate (CS) and polyethylene glycol (PEG). Various multi-armed PEG-Norbornene (A-PEG-N) with different molecular sizes were investigated to generate crosslinked copolymers with tunable rheological and mechanical properties. The crosslinked and mechanically stable porous hydrogels could be generated by simply mixing the two clickable Tetrazine-CS (TCS) and A-PEG-N components, generating a self-standing hydrogel within minutes. The leading candidate (TCS-8A-PEG-N (40 kD)), based on the mechanical and biocompatibility results, was further employed as a scaffold to improve wound closure and blood flow in vivo. The hydrogel demonstrated not only enhanced blood perfusion and an increased number of blood vessels, but also desirable fibrous matrix orientation and normal collagen deposition. Taken together, these results demonstrate the potential of the hydrogel to improve wound repair and hold promise for in situ skin tissue engineering applications.