The effect of scanning electrochemical potential on the short-term impedance of commercially pure titanium in simulated biological conditions

The electrochemical history (voltage-time variations) of titanium oxide-solution interfaces can vary widely in vivo, particularly where oxide abrasion is present, and it is important to assess the effects of voltage on the impedance behavior of the interface. Potential step impedance analysis (PSIA) utilizes a time and frequency domain methodology to assess the electrochemical impedance of electrified interfaces over a range of voltages. The PSIA method was used to study the combined effects of scanning electrical potential and the presence of solution-born organic species (protein, amino acids, etc.) on the electrochemical properties of cpTi. The specific solutions used in these scanning PSIA experiments were phosphate buffered saline and cell culture medium supplemented with 10% fetal bovine serum. The results show that electrochemical impedance properties of cpTi are voltage-time history dependent and strongly influenced by electrical potential within the -1000 mV to +1000 mV range studied. Moreover, the presence of biologically relevant molecules in the electrolyte solution alters the impedance properties only at cathodic potentials. Specifically, at cathodic potentials, these organic species have been shown to suppress the cathodic current density, shift the zero current potential in the cathodic direction, and increase the interfacial capacitance, polarization resistance, and the distribution of surface relaxation times. At anodic potentials, the presence of the organic species does not alter any of the electrochemical properties examined. Overall, these results show the importance of understanding of the variation in electrochemical potentials achievable in vivo and the effects voltage history has on interfacial electrochemical behavior.