Facile Construction of Structural Gradient of TiO 2 Nanotube Arrays on Medical Titanium for High Throughput Evaluation of Biocompatibility and Antibacterial Property.

A structural gradient of TiO 2 nanotube arrays (TiO 2 NTAs) on medical titanium has been constructed by pull-stop-pull together with electrochemical anodization. The formation mechanism of TiO 2 NTAs with different nanostructures formed on a single titanium surface was discussed. It was found that the structural gradient of TiO 2 NTAs showed different properties in wettability translation, crystalline structure evolution, and electrodeposition of octacalcium phosphate (OCP). In vitro study demonstrated that the gradient TiO 2 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 TiO 2 NTAs, but S. aureus and E. coli preferred to TiO 2 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 TiO 2 NTAs can be an efficient technique for high throughput screening of their relationship of structure-properties on medical titanium surface.