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 TiO 2 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 TiO 2 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 TiO 2 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 TiO 2 metasurface, which combines antibacterial and bioactive features, has the potential to reduce the risk of postoperative infections and improve clinical outcomes.