Surface activation of Ti6Al4V via vacuum versus conventional ultraviolet photofunctionalization: physicochemical and biological insights

BACKGROUND: Ultraviolet (UV) photofunctionalization has been proposed as a means of removing hydrocarbon accumulation, which causes aging of titanium surfaces. Recent vacuum-UV (VUV) technologies exhibit faster, and more efficient surface activation compared with conventional UV protocols. The aim of the current work was to compare surface rejuvenation of grade V titanium alloy (Ti-6Al-4 V) using conventional UV and VUV photofunctionalization with physicochemical analyses and biological assays. METHODS: Ti6Al4V discs were divided into four groups: Group I (control), Group II (12 min TheraBeam Super Osseo), Group III (15 min TheraBeam Affiny), and Group IV (20 s DIO UV Activator). Surface characteristics were evaluated with SEM, EDS, XRD, TOF-SIMS, and contact angle goniometry. Human bone marrow mesenchymal stem cells (BM-MSC/TERT292) were cultured on discs. Cell viability (MTT), morphology (confocal microscopy, SEM), ALP activity, and osteogenic gene expression (Runx2, BSP, OPN, OCN) were assessed. RESULTS: AFM revealed no changes in surface roughness across groups. EDS, XRD, and TOF-SIMS confirmed progressive hydrocarbon removal with UV treatment, with Groups III and IV showing the lowest carbon levels (p < 0.001 vs. control). The contact angle decreased significantly from 76.9° ± 2.58 in controls to 26.9° ± 1.04 after VUV activation (p < 0.001). Biologically, UV treatment enhanced proliferation, cytoskeletal organization, ALP activity, and osteogenic gene expression, with Groups III and IV showing significantly greater responses compared with Group II (p < 0.001) though not significantly different from each other. CONCLUSION: Both conventional UV and VUV photofunctionalization rejuvenated titanium surfaces and improved osteogenic responses. VUV devices, particularly the DIO UV Activator, achieved equivalent activation in seconds compared with several minutes with conventional UV, suggesting a clinically advantageous, rapid chairside application.