Facile Construction of Structural Gradient of TiO2 Nanotube Arrays on Medical Titanium for High Throughput Evaluation of Biocompatibility and Antibacterial Property

A structural gradient of TiO2 nanotube arrays (TiO2 NTAs) on medical titanium has been constructed by pull-stop-pull together with electrochemical anodization. The formation mechanism of TiO2 NTAs with different nanostructures formed on a single titanium surface was discussed. It was found that the structural gradient of TiO2 NTAs showed different properties in wettability translation, crystalline structure evolution, and electrodeposition of octacalcium phosphate (OCP). In vitro study demonstrated that the gradient TiO2 NTAs also behaved significantly different in cell adhesion, extending and propagation of mouse MC3T3-E1, and formation of biofilm of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), respectively. It was found that the MC3T3-E1 cells were of higher bioactivity on the surface of 60 nm diameter TiO2 NTAs, but S. aureus and E. coli preferred to TiO2 NTAs with 90 nm diameter, which was attributable to the different adherent behaviors for cell and bacteria on nanosurfaces. Thus, the construction of structural gradient of TiO2 NTAs can be an efficient technique for high throughput screening of their relationship of structure-properties on medical titanium surface.