Voltage-controlled cellular viability of preosteoblasts on polarized cpTi with varying surface oxide thickness

Cathodic voltage shifts of metallic biomaterials were recently shown to induce cell apoptosis in-vitro. The details of the reduction-based physico-chemical phenomena have not yet been fully elucidated. This study shows how surface oxide thickness of commercially pure titanium affects the voltage viability range, and whether anodic oxidation can extend this range. Cell viability, cytoskeletal organization, and cellular adhesion on bare and anodized Ti, at -500, -400mV(Ag/AgCl) and open circuit potential were assessed. Surfaces were characterized using contact angle measurement and atomic force microscopy, and the observed cellular response was related to the changes in electrochemical currents, and impedance of the samples. Results show that anodization at 9V in phosphate buffer saline generates a compact surface oxide with comparable surface roughness and energy to the starting bare surface. The anodized surface extends the viability range at 24h from -400mV(Ag/AgCl) by about -100mV, which corresponds to an increase in impedance of the surface from 58kΩcm² to 29MΩcm² at -400mV(Ag/AgCl) and results in low average current densities below 0.1μAcm^-2. The results demonstrate that the voltage range for cell viability under cathodic polarization is expanded due to anodization of the surface oxide and lowering of cathodic currents.