Osteogenic and long-term antibacterial properties of Sr/Ag-containing TiO₂ microporous coating in vitro and in vivo

Bacterial infection and poor osseointegration are two critical issues that need to be solved for long-term use of titanium implants. As such, Sr/Ag-containing TiO2 microporous coatings were prepared on a Ti alloy surface in the current study via a single-step microarc oxidation technique. The coatings showed both good cytocompatibility in vitro and biosafety in vivo. Sr/Ag incorporation brought no significant change in the surface micromorphology and physicochemical properties, but endowed the coating with strong osteogenic activity and long-term antibacterial capability in vitro. Furthermore, the osteogenic and antibacterial capability of the coating was also confirmed in vivo. In a rat osseointegration model, new bone formation, implant-bone contact, removal torque and bone mineralization were all significantly increased in the M-Sr/Ag group when compared with those in group M, although they were slightly lower than those in group M-Sr. In a periimplantitis model, no rats suffered infection in the M-Sr/Ag group after 3 months of osseointegration and 5 weeks of bacterial inoculation period, when compared to 100% and 75% infection rates in M and M-Sr groups, respectively. In addition, active bone remodeling and many mesenchymal cells were observed in the M-Sr group, suggesting good bone regeneration potential in Sr-containing coatings in the case of controlled periimplantitis. Overall, the Sr/Ag-containing TiO2 microporous coating is valuable for preventing periimplantitis and improving implant reosseointegration, and is therefore promising for long-term and high quality use of titanium implants.