Electrical Responsive Coating with a Multilayered TiO2–SnO2–RuO2 Heterostructure on Ti for Controlling Antibacterial Ability and Improving Osseointegration

The bacterial infection and poor osseointegration of Ti implants could significantly compromise their applications in bone repair and replacement. Based on the carrier separation ability of the heterojunction and the redox reaction of pseudocapacitive metal oxides, we report an electrically responsive TiO₂-SnO₂-RuO₂ coating with a multilayered heterostructure on a Ti implant. Owing to the band gap structure of the TiO₂-SnO₂-RuO₂ coating, electron carriers are easily enriched at the coating surface, enabling a response to the endogenous electrical stimulation of the bone. With the formation of SnO₂-RuO₂ pseudocapacitance on the modified surface, the postcharging mode can significantly change the surface chemical state of the coating due to the redox reaction, enhancing the antibacterial ability and osteogenesis-related gene expression of the human bone marrow mesenchymal stem cells. Owing to the attraction for Ca²⁺, only the negatively postcharged SnO₂@RuO₂ can promote apatite deposition. The in vivo experiment reveals that the S-SnO₂@RuO₂-NP could effectively kill the bacteria colonized on the surface and promote osseointegration with the synostosis bonding interface. Thus, negatively charging the electrically responsive coating of TiO₂-SnO₂-RuO₂ is a good strategy to endow modified Ti implants with excellent antibacterial ability and osseointegration.