NIR-Activated Antibacterial and Bioactive Mn-Doped TiO ₂ /Ti ₃ C ₂ Composite Coatings

Implant-associated infections and insufficient osseointegration remain major challenges that limit long term clinical performance of orthopedic implants. In recent years, near infrared (NIR) light triggered photothermal and photodynamic strategies have attracted increasing attention as efficient and controllable antibacterial approaches. In this work, a Mn-doped TiO 2 coating was fabricated on a Ti substrate via micro arc oxidation, followed by surface assembly of Ti 3 C 2 nanosheets using polydopamine as an interfacial mediator, thereby constructing a multifunctional MT@Ti 3 C 2 composite coating with combined antibacterial and osteogenic potential. The resulting coating exhibits enhanced hydrophilicity, improved corrosion resistance, and stable interfacial adhesion, providing a favorable surface environment for biological interactions. The incorporation of Ti 3 C 2 nanosheets endows the coating with pronounced NIR responsiveness. Under 808 nm NIR irradiation, the MT@Ti 3 C 2 coating exhibits a pronounced photothermal response and significantly enhanced reactive oxygen species generation, including singlet oxygen and hydroxyl radicals, compared with the MT coating, which synergistically contributes to strong antibacterial activities with efficiencies of 98.4% against Escherichia coli and 96.8% against Staphylococcus aureus. In vitro simulated body fluid tests demonstrate that the coating effectively induces the formation of bone like hydroxyapatite, indicating enhanced bioactivity. Further in vitro cell studies reveal good cytocompatibility of the MT@Ti 3 C 2 coating, along with promoted early cell adhesion and enhanced cell proliferation, highlighting its potential for multifunctional surface modification of orthopedic implants.