Reduction of Staphylococcus aureus initial attachment on UVC-irradiated titanium surface

Objective: Contamination of implant surface by wound pathogen such as Staphylococcus aureus causes implant failure. UVC irradiation to titanium enhances titanium's osseointegration capability by changing physicochemical characteristics on the surface including an induction of superhydrophilicity which possibly influences bacterial attachment. The objective of this study was to evaluate the effect of UVC irradiation to titanium on Staphylococcus aureus attachment on the surface compared to UVA irradiation which was a well-known technique to photocatalytically induce superhydrophilicity on titanium surface. Methods: Grade II commercially pure titanium disks with turned or acid-etched surface pre-irradiated with or without 500 KJ/cm2 of UVC or UVA were incubated in BHI broth containing 1x107 Staphylococcus aureus . After 0, 0.5, 1, 2, 4 and 8 hours incubation, bacterial attachment on titanium surface was evaluated by CTC staining for viable bacteria and fluorescence microscopic quantification. Wettability on the surface was measured before and after UVA or UVC irradiation. Data was treated with Bonferroni correction after two-way ANOVA (a=0.05).Results: Regardless of surface topography, the percentage of CTC positive area on UVC pre-irradiated titanium surfaces was lower than that on non-radiated surfaces at each incubation time (p<0.05). The value was 34 and 44% on the turned and acid-etched surface without UV irradiation at 8 hour incubation, which was down to 25 and 16% with UVC pre-irradiation. UVA pre-irradiation reduced bacterial attachment on turned surface to a level equivalent to UVC pre-irradiation. However, the bacterial reduction on acid-etched surface with UVA pre-irradiation was inferior to that with UVC pre-irradiation. Both UVA and UVC irradiation changed the wettability on both turned and acid-etched surfaces from hydrophobic status to superhydrophilicity.Conclusion: UVC irradiation to titanium surface reduced Staphylococcus aureus attachment on the titanium surface, rivaling or surpassing UVA irradiation. The mechanism involved an induction of superhydrophilicity and possibly other physicochemical event on the surface.