Fibroblast responses and antibacterial activity of Cu and Zn co-doped TiO ₂ for percutaneous implants

In order to enhance skin integration and antibacterial activity of Ti percutaneous implants, microporous TiO ₂ coatings co-doped with different doses of Cu ²⁺ and Zn ²⁺ were directly fabricated on Ti via micro-arc oxidation (MAO). The structures of coatings were investigated; the behaviors of fibroblasts (L-929) as well as the response of Staphylococcus aureus (S. aureus) were evaluated. During the MAO process, a large number of micro-arc discharges forming on Ti performed as penetrating channels; O ²⁻ , Ca ²⁺ , Zn ²⁺ , Cu ²⁺ and PO ₄ ³⁻ delivered via the channels, giving rise to the formation of doped TiO ₂ . Surface characteristics including phase component, topography, surface roughness and wettability were almost the same for different coatings, whereas, the amount of Cu doped in TiO ₂ decreased with the increased Zn amount. Compared with Cu single-doped TiO ₂ (0.77 Wt% Cu), the co-doped with appropriate amounts of Cu and Zn, for example, 0.55 Wt% Cu and 2.53 Wt% Zn, further improved proliferation of L-929, facilitated fibroblasts to switch to fibrotic phenotype, and enhanced synthesis of collagen I as well as the extracellular collagen secretion; the antibacterial properties including contact-killing and release-killing were also enhanced. By analyzing the relationship of Cu/Zn amount in TiO ₂ and the behaviors of L-929 and S. aureus, it can be deduced that when the doped Zn is in a low dose (<1.79 Wt%), the behaviors of L-929 and S. aureus are sensitive to the reduced amount of Cu ²⁺ , whereas, Zn ²⁺ plays a key role in accelerating fibroblast functions and reducing S. aureus when its dose obviously increases from 2.63 to 6.47 Wt%.