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In this study, a new kind of sustained-release silver-loaded chitosan-based sponge was developed by a simple and green method as a long-lasting antimicrobial dressing. The embedded silver nanoparticles (AgNPs) were prepared by catechol-conjugated chitosan (CCS). The CCS-coated AgNPs (CCS-AgNPs) were incorporated into the chitosan (CS) matrix through interactions between the catechol and amino groups of CS. Well-dispersed and unaggregated CCS-AgNPs were observed in the composite sponges. Due to an interconnected multi-porous structure, the composite sponges exhibited excellent flexibility and water absorption capability, which is beneficial to remove excess exudates effectively. In silver release tests, CCS-AgNPs/CS showed sustained release, whereas the control group without catechol exhibited burst release. As a bridge to bind AgNPs into the CS matrix, catechol extended the silver release time from 1 day to at least 4 days. The prolonged silver release endows CCS-AgNPs/CS sponges with long-lasting bacteriostatic effects against both Gram positive and negative bacteria. Bacterial growth was completely inhibited for up to 3 days. Meanwhile, the embedded CCS-AgNPs significantly improved the bactericidal effect. More than 99.99% bacteria could be killed by the composite sponges, which completely satisfies antibacterial requirements for wound healing. As a double-edged sword, an excessively high silver content induced cytotoxicity in MC3T3 cells. In general, the CCS-AgNPs/CS sponge with appropriate silver content (0.63 wt%) is considered as a potential candidate for wound healing dressings due to its long-lasting bacteriostatic effect, powerful bactericidal activity, and excellent biocompatibility.

A novel chitosan (CS)-based asymmetric scaffold composed of a dense layer and a loose layer was fabricated via the self-deposition approach. The micro-structure and mechanical properties were verified to satisfy the criteria for the guided tissue regeneration (GTR) membrane. The in vitro biocompatibility of the scaffold was verified by the CCK-8 assays of MC3T3 osteoblastic cells. The rat skull defect model was applied to estimate the in vivo bone regeneration performance. The micro-CT and histological results manifested its outstanding bone regenerative ability and superior degradability over the Bio-gide® membrane. Considering the relative low expense and simple fabrication process, the prepared asymmetric CS scaffold is a prospective candidate for GTR therapy.

In this study, catechol-conjugated chitosan (CSS) was synthesized to prepare silver nanoparticles in aqueous solution as both a reducing and stabilizing agent. The entire reaction process complied with the principles of green chemistry. The stability and physicochemical properties of CSS-coated silver nanoparticles (CSS–Ag NPs) were well characterized by a series of techniques. A narrow diameter distribution and excellent stability were observed in the target CSS–Ag NPs. Determination of the minimum inhibitory concentration (MIC) and the disk diffusion test were applied to evaluate the antibacterial activities with respect to quantity and quality, respectively. The cytotoxic effects on HepG2 cells were also evaluated with a series of assays. The resulting CSS–Ag NPs combined the unique properties of chitosan and silver nanoparticles, showing effective antibacterial activities and low cytotoxicity. The effective toxic concentration of CSS–Ag NPs towards E. coli and S. aureus is too low to damage HepG2 cells. The results demonstrated that CSS–Ag NPs could be a potential candidate for use in biological and pharmaceutical areas to prevent infections caused by microorganisms.