Electrochemical investigation of peripheral nerve stimulation electrodes in vivo and in vitro during 53 days

The objective of the study was to investigate the electrochemical properties of porous titanium nitride electrodes in vivo and in vitro for a period of 53 days. Four electrodes were implanted in two pigs and four electrodes were kept in phosphate buffered saline at 37.5 °C. Electrochemical impedance spectroscopy, voltage transient measurements, cyclic voltammetry and electrical stimulation were applied in vivo and in vitro. In vivo, electrical stimulation was successful, using stable currents below the safe limits. However, increasing voltage transients and decreasing charge storage capacity (CSC) were observed, which was likely related to wound healing. In vitro, decreasing CSC and increasing electrode impedance were observed, which was likely related to electrode deterioration.