Antibacterial properties and biological activity of 3D-printed titanium alloy implants with a near-infrared photoresponsive surface

Abstract Purpose SLM 3D printing technology is one of the most widely used implant-making technologies. However, the surfaces of the implants are relatively rough and bacteria can easily adhere to them; this increases the risk of postoperative infection. Therefore, we prepared a near-infrared photoresponsive nano-TiO₂ coating on the surface of an SLM 3D-printed titanium alloy sheet (Ti6Al4V) via a hydrothermal method to evaluate its antibacterial properties and biocompatibility. Methods Using SLM technology, titanium alloy sheets were 3D printed, and a nano-TiO₂ coating was prepared on its surface via a hydrothermal method to obtain Ti6Al4V@TiO₂. The surface morphology, physicochemical properties, and photothermal response of the samples were observed. The Ti6Al4V groups and Ti6Al4V@TiO₂ groups were cocultured with S. aureus and E. coli and exposed to 808 nm NIR light (0.8 W/cm²) and viable plate count experiments and live/dead bacterial staining were used to assess their in vitro antibacterial properties. Results The hydrophilicity of the nano-TiO₂ coating sample significantly improved and the sample exhibited an excellent photothermal response. The temperature reached 46.9°C after 15 min of irradiation with 808 nm NIR light (0.8 W/cm²). The Ti6Al4V group showed significant antibacterial properties after irradiation with 808 nm NIR light, and the Ti6Al4V@TiO₂ group also had partial antibacterial ability without irradiation. After irradiation with 808 nm NIR light, the Ti6Al4V@TiO₂ group showed the strongest antibacterial properties, reaching 90.11% and 90.60% against S. aureus and E. coli, respectively. Conclusions A nano-TiO₂ coating prepared via a hydrothermal method produced synergistic antibacterial effects after NIR light irradiation.