Synergistic antibacterial effect of photocatalytic coatings activated by visible light and photodynamic therapy for rapid peri-implantitis treatment

Biofilm accumulation and subsequent implant-related infections pose significant challenges in the biomedical field. Photocatalytic coatings hold promise for antimicrobial efficacy; however, their effectiveness in dynamic polymicrobial infections for clinical use remains a novel and ongoing challenge. To address this, combining visible-light-triggered photocatalytic coatings with methylene blue-mediated photodynamic therapy (MB-PDT) has the potential to optimize treatment efficacy and simplify multifunctional coating designs for diverse implant therapy needs. Herein, a one-step plasma electrolytic oxidation technique is employed to create a photocatalytic coating composed of crystalline titanium dioxide (TiO₂) doped with bismuth (Bi-TiO₂). This coating enhances bioactivity, hardness, and wear resistance, which are favorable properties for an implant biointerface. Furthermore, this coating generates reactive oxygen species (ROS) under visible light, which is robustly boosted when combined with MB-PDT due to the synergistic wavelength absorption between Bi-TiO₂ and methylene blue, leading to highly effective microbial eradication within just 1 min of treatment. Further in vivo assays confirm the antimicrobial efficacy and demonstrate a reduction in inflammatory responses, thereby favoring the wound repair process. Our proof-of-concept data offer a promising solution for peri-implant infections, using visible-light-driven photocatalytic coatings in combination with PDT to combat biofilm-related infections while maintaining the properties that affect the longevity of dental implants.