Effects of graphene on the structure, properties, electro-response behaviors of GO/PAA composite hydrogels and influence of electro-mechanical coupling on BMSC differentiation.

Electro-responsive Graphene oxide-poly(acrylic acid) (GO-PAA) nanocomposite hydrogels with different concentrations of GO were successfully fabricated via in situ polymerization. The covalently crosslinked PAA network is intertwined with GO sheets by the bridging of hydrogen-bond interactions thus resulting in an integrated and stable hydrogel network. The swelling, mechanical and conductivity properties of the hydrogel are impacted as a result. The influences of different factors on the electro-response behavior of the hydrogels were deeply explored. Because of electrostatic double layer of the GO, the response properties of hydrogels in different voltage, pH, and ionic strength improved significantly. Meanwhile, with the addition of GO, the response performance of hydrogel in biological applications was greatly expanded. Furthermore, GO-PAA hydrogel shows a good compatibility with bone marrow-derived mesenchymal stem cells (BMSCs). The electro-mechanical coupling of the hydrogel can change the morphology of the adhesive cells, and regulate the cytoskeleton of the cell under the condition of electrical stimulation, which can further promote the differentiation of neural stem cells. This electro-responsive hydrogel could be widely used in many fields of biomedical application such as artificial muscle and tissue engineering scaffold.

In situ synthesis of silver-nanoparticles/bacterial cellulose composites for slow-released antimicrobial wound dressing.

Bacterial cellulose has attracted increasing attention as a novel wound dressing material, but it has no antimicrobial activity, which is one of critical skin-barrier functions in wound healing. To overcome such deficiency, we developed a novel method to synthesize and impregnate silver nanoparticles on to bacterial cellulose nanofibres (AgNP-BC). Uniform spherical silver nano-particles (10-30 nm) were generated and self-assembled on the surface of BC nano-fibers, forming a stable and evenly distributed Ag nanoparticles coated BC nanofiber. Such hybrid nanostructure prevented Ag nanoparticles from dropping off BC network and thus minimized the toxicity of nanoparticles. Regardless the slow Ag(+) release, AgNP-BC still exhibited significant antibacterial activities with more than 99% reductions in Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. Moreover, AgNP-BC allowed attachment and growth of epidermal cells with no cytotoxicity emerged. The results demonstrated that AgNP-BC could reduce inflammation and promote wound healing.