Cytocompatibility and antibacterial activity of nanostructured H₂Ti₅O₁₁·H₂O outlayered Zn-doped TiO₂ coatings on Ti for percutaneous implants

To improve skin-integration and antibacterial activity of percutaneous implants, the coatings comprising an outer layer of H₂Ti₅O₁₁·H₂O (HTO) nanoarrays and an inner layer of microporous Zn-doped TiO₂ were fabricated on Ti by micro-arc oxidation (MAO) followed with hydrothermal treatment (HT). During HT process, a large proportion of Zn²⁺ migrated out from TiO₂ layer. TiO₂ reacted with OH^- and H₂O, resulting in the nucleation of HTO. The nuclei grew to nanoplates, nanorods and nanofibres with HT process prolonged. Simultaneously, the orientation of nanoarrays changed from quasi-vertical to parallel to substrate. Compared to Ti, adhesion and proliferation of fibroblasts were enhanced on as-MAOed TiO₂ and HTed coatings. The phenotype, differentiation and extracellular collagen secretion were obviously accelerated on vertical nanorods with proper interspace (e.g. 63 nm). HTed coatings showed enhanced antibacterial activity, which should be ascribed to the nano-topography of HTO.