The effect of cathodic electrochemical potential of Ti-6Al-4V on cell viability: Voltage threshold and time dependence

The biocompatibility of metallic biomaterials is dependent on the redox state of the surface and its effect on cellular redox equilibrium. When metallic biomaterials experience mechanically assisted corrosion such as fretting, there is a drop in the voltage of its surface. Studies have demonstrated that cell viability is significantly degraded by sustained cathodic excursion in voltage of metallic biomaterials below a critical potential between -300 and -600 mV on commercially pure titanium. Cells cultured at above -300 mV showed little loss in viability whereas cells cultured on -600 mV Ti were almost 100% killed at 24 h. The goal of this study is to concisely define the voltage threshold and time-dependence of the cell killing effect seen on titanium surfaces. MC3T3 cells were cultured on electrochemically controlled Ti-6Al-4V surfaces at voltages ranging from -300 to -1000 mV for time periods ranging from 1 to 24 h. Cell viability and morphology was monitored with live-dead assay and scanning electron microscopy. Cell viability decreased from -300 to -400 mV and exhibited time-dependence where the more cathodic the potential, the faster the drop-off of viability. Hundred percent cell killing took as little as 4 h at -1000 mV and required 24 h at -400 mV. Sustained net cathodic currents with densities as low as 0.1 μA/cm² are observed during cell killing. This work shows reduction reactions are an important element of cellular viability in a time and potential dependent way and may explain why mechanically assisted corrosion reactions may lead to increased cell killing in metallic implants. Note: All voltages are versus Ag/AgCl © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 101B: 1489-1497, 2013.