NIR-II photoresponsive antibacterial coatings on titanium implants using strontium titanate metastructures

Implant-associated infections present a significant clinical challenge, exacerbated by the increasing prevalence of antibiotic resistance associated with conventional antibiotic therapies. Photoresponsive antibacterial strategies offer a promising alternative, but their effectiveness in treating deep tissue infections is often limited by the short wavelengths required for activation of most photosensitizers. This study reports the development of a strontium titanate (STO) metastructure coating on titanium alloy implants, engineered for long-wavelength photoresponsive antibacterial activity. We demonstrate that the size of the STO metastructure particles is precisely controlled by modulating the Sr(OH)₂ precursor concentration, enabling tunable optical responses within the 800 nm–1600 nm wavelength range. The resulting coating exhibits excellent antibacterial efficacy upon irradiation with second near-infrared window (NIR-II) light (1064 nm), while demonstrating good biocompatibility and minimal damage to healthy cells after NIR exposure.