Change of titanium's biological property depending on UVC irradiation energy

Objectives: UVC-mediated photofunctionalization to enhance titanium's osseointegration capability has been discovered recently, which was characterized by the upgraded protein and cellular affinities of titanium. However, the process of UVC-mediated photofunctionalization remains unknown. The objective of this study was to examine influence of UVC irradiation energy on titanium's biological and physicochemical properties. Methods: Osteoblastic cells derived from femoral bone marrow of 8 weeks-old SD rats or bovine serum albumin were incubated on grade II commercially pure titanium desk with turned or acid-etched surface pre-irradiated with 0, 10, 250, 500, 750 or 1000 KJ/cm² of UVC. Attached cell number and protein deposition on titanium surface were quantified with WST-1 and colorimetric protein assays at day 1. Physicochemical change on titanium surface by UVC-irradiation was evaluated by XPS analysis. Data was treated with one-way ANOVA (α=0.05=0.05). Result: There was significant difference in attached cell number and albumin deposition on titanium surface at day 1 among UVC pre-irradiated and non-radiated surfaces. The number was 2.6 and 1.7 times greater on turned and acid-etched surface pre-radiated with 500 and 750 KJ/cm² of UVC than on the non-radiated surface, respectively. However, farther pre-irradiation　energy resulted in a decline in the number on both surfaces. The protein amount increased on UVC pre-radiated surface and plateaued at the turned and acid-etched surface pre-radiated with 500 and 10 KJ/cm² of UVC, where the value was 3.5 and 1.4 times greater than on the non-radiated surfaces, respectively. Amount of carbon on titanium surface decreased with UVC irradiation energy to below 30% of that on the non-irradiated surface. Conclusion: Increase of UVC irradiation energy gradually enhanced protein and osteoblastic affinities of titanium with removal of carbon on titanium surface. However, the biological effect of UVC irradiation weakened due to over-irradiation, suggesting the involvement of other physicochemical alternation in the UVC-mediated photofunctionalization.