Immunomodulation and osteointegration of infected implants by ion-riched and hierarchical porous TiO₂ matrix

Infection is a main cause of implant failure. The microenvironment cell experiencing after antimicrobial therapy of infected implants is very crucial for immunomodulation and subsequent osteointegration. Based on the superiority of photothermal therapy in anti-infection, a matrix of nanograined TiO₂ with (Si/P)-dual ions and hierarchical nano/microporous topography is developed on Ti implant by micro-arc oxidation. It shows good photothermal properties due to the lattice distortion induced by ion doping and can kill bacteria with near-infrared (NIR) light irradiation efficiently. Due to the combined action of porous topography and release of Si/P ions, the TiO₂ matrix achieves M1-to-M2 phenotype switch of macrophages timely at different simulating infection stage and accelerates recruitment, proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) in vitro. In vivo, the TiO₂ matrix also shows desired antibacterial performance after photothermal therapy and exhibits outstanding immunomodulatory ability and new bone formation efficiency. This study provides a promising TiO₂ matrix applied in clinic for settling implant infection by NIR light irradiation and promoting bone regeneration through osteoimmunomodulation.