Silk fibroin-based coating with pH-dependent controlled release of Cu2+ for removal of implant bacterial infections

[Display omitted] •A coating with pH-dependent Cu2+ release was granted on the Ti.•The coating was composed of polydopamine and silk protein, exhibiting outstanding biocompatibility in vivo and in vitro.•While simulating a large gathering of bacteria (slightly acidic conditions), the coating could set free abundant Cu2+ to strongly kill bacteria and achieve self-defense. The implantation of medical devices is frequently accompanied by the invasion of bacteria, which may lead to implant failure. Therefore, an intelligent and responsive coating seems particularly essential in hindering implant-associated infections. Herein, a self-defensive antimicrobial coating, accompanied by silk fibroin as a valve, was successfully prepared on the titanium (Ti-Cu@SF) for pH-controlled release of Cu2+. The results showed that the layer could set free massive Cu2+ to strive against E. coli and S. aureus for self-defense when exposed to a slightly acidic condition. By contrary, a little Cu2+ was released in the physiological situation, which could avoid damage to the normal cells and showed excellent in vitro pH-dependent antibiosis. Besides, in vivo experiment confirmed that Ti-Cu@SF could work as an antibacterial material to kill S. aureus keenly and display negligible toxicity in vivo. Consequently, the design provided support for endowing the layer with outstanding biocompatibility and addressing the issue of bacterial infection during the implantation of Ti substrates.