Mass changes and dissolution of platinum during electrical stimulation in artificial perilymph solution

The electrochemistry of platinum electrodes in artificial perilymph solutio n subjected to cyclic and steady-state potentials was studied by a quartz c rystal electrochemical microbalance and by analysis of electrolyte for diss olved platinum. The effect of amino acid adsorption appears to be one of bl ocking sites for platinum oxidation and oxide reduction, a process in which the amino acid competes with chloride from phosphate-buffered saline. For amino acids such as cysteine, which are known to interact strongly with pla tinum, the voltammograms became nearly featureless and only a small change in mass was observed during cycling of the potential. There were no mass ch anges of an electrode in solution containing human serum albumen, but its p resence did inhibit dissolution of platinum. The overall magnitudes of diss olved platinum found in the buffered solutions were low, remaining below 5 ppb in most cases. Dissolution was greatest in solutions containing high co ncentrations of cysteine. Extrapolation of the results to implanted auditor y prosthesis electrodes indicated that platinum dissolution would not lead to toxic concentrations in the body. (C) 2000 Elsevier Science Ltd. All rig hts reserved.