The effect of fretting associated periodic cathodic potential shifts on the electrochemistry and in vitro biocompatibility of commercially pure titanium

This study explored how periodic cathodic polarization of commercially pure titanium (cpTi) alters its electrochemical properties and biocompatibility. MC3T3-E1 preosteoblast cells were cultured directly on cpTi samples and maintained at open circuit potential (OCP) for 24 h followed by an additional 24-h sequence of periodic cathodic polarization to −1000 or −750 mV (vs. Ag/AgCl) for 1 s followed by a 5-s recovery at OCP. Control experiments were performed where the samples were maintained at OCP throughout the entire test. Subsequent electrochemical impedance spectroscopy revealed both of the periodic cathodic polarization conditions significantly reduced the polarization resistance (R_p), while only the −1000 mV condition significantly increased the capacitance (C) as compared to the controls. Scanning electron micrographs showed that the cells were fragmented and balled up on the samples periodically shifted to −1000 mV as compared to the cells that were well spread on the controls and samples periodically shifted to −750 mV. Additionally, live/dead fluorescence microscopy revealed that periodic polarizations to −1000 mV reduced cell viability to around 12% as compared to the greater than 95% cell viability observed on the controls and samples periodically polarized to −750 mV. This work showed that periodic cathodic potential shifts can notably alter the electrochemical behavior of cpTi and the viability and morphology of cells seeded directly onto its surface.