A nanozyme-engineered implant surface for sequential photodynamic antibacterial and cytoprotective functions

Addressing the dual challenges of bacterial infection and poor osseointegration in titanium implants is hindered by the "bactericidal vs. osteogenic" conflict. Here, we present a hierarchical nano-architecture with an "attack-defense" strategy to achieve temporal synergy. We first constructed an NIR-responsive TiO_2-x optical superstructure for potent photodynamic killing. On top of this, a CoMn₂O₄ nanozyme layer with high catalase-like activity was anchored to provide a defensive function. Upon NIR irradiation, the surface first unleashes a powerful bactericidal ROS burst, which is then rapidly scavenged by the nanozyme layer. This process not only ensures high antibacterial efficacy but also transforms the oxidative microenvironment into one conducive to healing. Consequently, osteoblasts cultured on the surface were protected from oxidative damage and exhibited significant upregulation of osteogenic differentiation markers. By temporally decoupling these antagonistic functions, our work provides a novel pathway for developing next-generation intelligent implants.