A coating strategy on titanium implants with enhanced photodynamic therapy and CO-based gas therapy for bacterial killing and inflammation regulation

Antimicrobial photodynamic therapy (aPDT) has been considered a noninvasive and effective modality against the bacterial infection of peri‑implantitis, especially the aPDT triggered by near-infrared (NIR) light due to the large penetration depth in tissue. However, the complexity of hypoxia microenvironments and the distance of aPDT sterilization still pose challenges before realizing the aPDT clinical application. Due to the long lifespan and transmission distance of therapeutic gas molecules, we design a multi-functional gas generator that combines aPDT as well as O2 and CO gas release function, which can solve the problem of hypoxia (O2) in PDT and the problem of inflammation regulation (CO) in the distal part of peri‑implant inflammation under near-infrared (NIR) irradiation. In the composite nanoplatform that spin-coated on the surface of titanium implants, up-conversion nanoparticles (UCNPs) were involved in converting the NIR to visible, which further excites the partially oxidized stannic sulfide (SnS2), realizing the therapeutic gas release. Indocyanine green (ICG) was further integrated to enhance the aPDT performance (Ti-U@SnS2/I). Therefore, reactive oxygen species (ROS), CO, and O2 can be controllably administered via a composite nano-platform mediated by a single NIR light (808 nm). This implant surface modification strategy could achieve great self-enhancement antibacterial effectiveness and regulate the lingering questions, such as relieving the anoxic microenvironment and reaching deep infection sites, providing a viable antibiotic-free technique to combat peri‑implantitis.