Sol-gel TiO2-based coatings in 3D printed porous Ti-6Al-4V alloy structures as efficient antibacterial drug delivery systems: Thorough structural and biological characterization

The application of sol-gel coatings on titanium-based materials offers a promising approach for enhancing their bioactivity, antibacterial properties, and adhesion, particularly for biomedical applications. This study focuses, for the first time, on the preparation and characterization of sol-gel TiO₂-based coatings containing hydroxyapatite and silver in 3D-printed porous gyroid and dodethick structures. TiO₂-based coatings on the standard wrought Ti-Al-V alloy rods were used as a reference. The coatings were applied via the specific dip-coating process developed by the author team. The microstructural analysis revealed that the sol-gel coatings on the reference wrought rod samples were homogeneous and well-adhered. The coatings on the porous gyroid and dodethick structures exhibited some localized cracking due to the complex geometry of the porous structures. Bioactivity was evaluated through the standard in vitro simulated body fluid tests, confirming hydroxyapatite precipitation on HA-containing coatings. Antibacterial properties were assessed against Escherichia coli, demonstrating nearly 100 % bacterial inhibition for Ag-containing coatings. Cytotoxicity tests with L929 fibroblast cells indicated that coatings with lower Ag concentrations in sol were non-toxic, while higher Ag concentrations in sol resulted in reduced cell viability, particularly in gyroid structures.