Enhanced Long-Term Antibacterial and Osteogenic Properties of Silver-Loaded Titanium Dioxide Nanotube Arrays for Implant Applications

Objective: This study explored constructing silver-loaded titanium dioxide nanotube (TiO₂ NT) arrays on titanium surfaces using anodic oxidation combined with ion implantation. We assessed the cytocompatibility, antibacterial properties, and osteogenic potential of these silver-loaded TiO₂ NT arrays, along with the underlying mechanisms. Methods: We utilized anodization to create TiO₂ NT arrays and employed ion implantation to load silver ions, categorizing samples into groups NT-Ag-II-L, NT-Ag-II-M, and NT-Ag-II-H based on different Ag ion dosages. Characterization was performed via scanning electron microscopy (SEM). We evaluated cell compatibility and assessed the antimicrobial performance and Ag ion release profiles. The osteogenic ability of the samples was measured, and the effects on ERK5 and osteogenesis-related factors were analyzed. To clarify the role of ERK5 in osteogenesis, we inhibited the ERK5 pathway using BIX02188 and subsequently re-evaluated osteogenic capacity in co-cultured cells. Results: SEM analysis showed that in the NT-Ag-II-M group, Ag ions exhibited a flake-like distribution atop the TiO₂ NTs, while NT-Ag-II-L and NT-Ag-II-H groups presented clustered grid structures. Energy-filtered transmission electron microscopy (EFTEM) confirmed orderly Ag ion arrangements within the lumens of the nanotubes. Notably, the silver-loaded TiO₂ NT arrays did not inhibit MC3T3-E1 cell proliferation and enhanced early cellular adhesion. All samples displayed significant antimicrobial activity initially, which decreased after seven days; however, Ag ion release decreased gradually over the first 14 days before stabilizing. Additionally, the samples increased alkaline phosphatase activity, collagen secretion, and extracellular matrix mineralization, up-regulating ERK5 and other osteogenic factors. Inhibition of the ERK5 pathway suppressed the osteogenic capabilities of the samples. Conclusion: Anodization and ion implantation successfully produced silver-loaded TiO₂ NT arrays on titanium surfaces, demonstrat-ing no cytotoxicity, sustained antimicrobial properties, and enhanced osteogenic potential. The antimicrobial effect relates to silver ion release, whereas osteogenesis is promoted by ERK5 signaling triggered by silver ions.