UV photofunctionalization differentially modulates fibroblast–epithelial dynamics on titanium: a cellular ecology rebalancing strategy for soft tissue sealing

Abstract Purpose Peri-implant soft tissue sealing depends on the coordinated behavior of epithelial cells and fibroblasts at the titanium abutment interface. However, their differential and potentially imbalanced responses on titanium may compromise formation of a stable biologic barrier. This study aimed to compare the behavior of human oral epithelial cells and fibroblasts on machined titanium and to determine whether UV photofunctionalization can rebalance their dynamics to promote a more favorable soft tissue environment. Methods Machined titanium plates were used as model abutment surfaces, with or without UV photofunctionalization. Surface physicochemical properties were characterized by contact angle measurement and X-ray photoelectron spectroscopy. Human oral epithelial cells and fibroblasts were evaluated in monoculture, co-culture, and transmigration models. Cell attachment (WST-1, microscopy), proliferation (BrdU), collagen production, and adhesion (mechanical detachment assay) were assessed. Co-culture experiments quantified relative cell population dynamics, and titanium-to-titanium transmigration assays evaluated the ability of cells to colonize new surfaces. Results On untreated titanium, epithelial cells exhibited significantly greater proliferation, whereas fibroblasts demonstrated higher collagen production and stronger adhesion. UV photofunctionalization reduced surface carbon and converted titanium from hydrophobic to hydrophilic. UV treatment enhanced attachment and growth of both cell types, with a greater increase observed in fibroblasts, thereby reducing the epithelial growth advantage. Collagen production was further augmented in fibroblasts, while epithelial cells showed a more pronounced improvement in adhesion, narrowing the adhesion gap between the two cell types. In co-culture, the population imbalance was significantly diminished on UV-treated surfaces. In transmigration assays, fibroblasts showed minimal migration on untreated titanium but extensive migration and surface colonization on UV-treated titanium, whereas epithelial cells exhibited robust migration under both conditions with less relative enhancement by UV. Conclusion UV photofunctionalization differentially modulates fibroblast–epithelial dynamics on titanium by enhancing fibroblast growth and migration while strengthening epithelial adhesion. By targeting the biologically limiting factors of each cell type, this compensatory effect rebalances cellular ecology at the interface. Collectively, these findings identify UV photofunctionalization as a rational surface-activation strategy with potential to create a smart titanium interface for promoting peri-implant soft tissue sealing.