UV photocatalytic activity of titanium dioxide (TiO₂) surface contaminated with bacterial biofilm: Implications for photo-restoration of osteoconductivity

Ultraviolet (UV) light-mediated activation of titanium dioxide (TiO₂) cleans the surface microenvironment through photocatalysis, but it is unknown whether this occurs when TiO₂ surfaces is contaminated with bacterial biofilms. We therefore formed bacterial biofilms on TiO₂ surfaces through culture with oral microorganisms from rats, which were subsequently exposed to high-intensity broadband UV light for 12 min. Osteoblast attachment, proliferation, and phenotypes were significantly compromised on biofilm-contaminated TiO₂ surfaces, but UV treatment restored these biological activities to native baselines of TiO₂ surfaces. The strength of bone-implant integration was 18.3 N for original implants, 1.5 N for biofilm-contaminated implants, and 30.5 N for biofilm-contaminated/UV-treated implants in a rat femur model after two weeks of healing. Histologically, there was limited, fragmented bone formation around biofilm-contaminated implants separated by thick fibrous tissue, while biofilm-contaminated/UV-treated implants induced robust bone formation with extensive direct bone-implant contact. Lipopolysaccharide (LPS) deposited on biofilm-contaminated TiO₂ surfaces which was decomposed and removed by UV treatment. Notably, biofilm-contaminated TiO₂ surfaces became superhydrophilic after UV treatment despite the persistence of carbon and nitrogen compounds, and UV treatment significantly restored the surface morphology of the innate titanium on the biofilm-contaminated TiO₂ surfaces. In summary, bacterial biofilm severely compromised titanium osteoconductivity, but treatment of contaminated titanium with UV light significantly restored osteoconductivity through substantially decreased accumulation of carbon, nitrogen, and LPS; the re-emergence of micro-topography; and the induction of superhydrophilicity, paving the way for photoenergy-mediated debridement of TiO₂ surface for clinical benefit.