In situ fabrication of NIR-II responsive TiO2 bio-metasurface for photothermal antibacterial and enhanced osseointegration

Titanium implants, widely used in orthopedic and dental applications, often face challenges due to inadequate osseointegration and the risk of postoperative infections, which can potentially lead to implant failure. To address this issue, we developed a titanium implant with an in-situ fabricated anatase TiO2 metasurface, characterized by a subwavelength thickness and a preferential orientation of the (001) facets. This metasurface, which consists of uniformly distributed nano-crystallites of approximately 30 nm in size, aims to enhance both osseointegration and antibacterial properties. The addition of isopropanol (IPA) to the precursor solution used in the fabrication process played a crucial role in controlling the grain size and coating thickness of the metasurface. This process led to a redshift of the light absorption peak into the near-infrared (NIR)-II region, thereby increasing the penetration depth of photothermal therapy. The implants with TiO2 metasurface exhibited increased hydrophilicity, rapid apatite formation in simulated body fluid, and an effective photothermal response under NIR-II light, showing significant antibacterial activity against E. coli and S. aureus. In vivo experiments in rabbits indicated superior bone regeneration and osseointegration around the implants with TiO2 metasurface compared to the control titanium implants. At 4 weeks postoperatively, the bone volume to tissue volume (BV/TV) ratio within the implant was 53.94%, and by 8 weeks, the implants were nearly entirely filled with new bone, with a BV/TV ratio of approximately 70%. The findings suggest that the TiO2 metasurface, which combines antibacterial and bioactive features, has the potential to reduce the risk of postoperative infections and improve clinical outcomes.