Platinum for neural stimulation: voltammetry considerations

Abstract

The underlying cause of electrical stimulation-induced tissue trauma is debated. Our focus has been to study effects of generating electrochemical by-products at the electrode-electrolyte interface, using the pulse-clamp technique coupled with voltammetry to analyze charge transfer. The platinum-H(2)SO(4) system has been a standard for analyzing electrochemistry on platinum-stimulating electrodes, even though the chemical differences between H(2)SO(4) and the living body are obvious. Experiments were designed to determine whether phosphate-buffered saline (PBS) could serve as a more accurate emulation of living tissue. It had been rumored that platinum's performance in PBS deviates from that in H(2)SO(4) at larger potentials. Voltammetry in PBS was performed in two potential ranges. In a conventional potential range (-0.6 V to +0.9 V versus Ag/AgCl), characteristic peaks appear very similar to published voltammograms of platinum in H(2)SO(4). However, in an extended range (-1.0 V to +1.7 V versus Ag/AgCl), platinum exhibited additional electrochemical activity: one oxidation peak and two reduction peaks. Therefore, voltammetry was performed in NaCl and a sodium phosphate mixture (i.e. PBS components) to separate their activity. The altered electrochemical performance of platinum in PBS suggests that certain reactions on platinum at potentials outside the water window will not reflect what happens in vivo.

Electrochemical detection of hydrogen peroxide on platinum-containing tetrahedral amorphous carbon sensors and evaluation of their biofouling properties

“…This was suggested to arise from oxidation of chloride ions and oxidation/reduction of phosphate ions [46]. Despite the narrower potential range similar reactions are proposed to occur on the surface of the Pt sample above 1.0 V vs. Ag/AgCl.…”

“…Hudak et al [46] studied cyclic voltammograms of Pt recorded in PBS (pH 7.2). Although between -0.6 V and 0.9 V vs. Ag/AgCl the response was well in line with the standard H2SO4 curves often used in the study of Pt electrochemistry, in the extended potential range from -1.0 V to 1.7 V vs.…”

Electrochemical and optical band gaps of bimetallic silver-platinum varying metal ratios nanoparticles

“…GCE/Pt NPs exhibited several oxidation changes; Peaks denoted a and b observed at more negative voltages of -465 and -250 mV are due to platinum's excess electrons, which resulted in hydrogen atoms bonding to Pt. Whereas the small peak c at 515 mV is a result of PtO formation (Hudak et al, 2010). Each Pt atom could be bound to a maximum of two oxygen atoms, resulting in Pt…”

High-density 3D pyramid-shaped microelectrode arrays for brain-machine interface applications

“…The setup of the electrodes (reference, working, and counting) was the same as the one used in the impedance measurement. The potential on the working electrode was swept between -0.6 and 0.8 V. The maximum cathodic (Emc) and anodic potentials on the electrode during electrical stimulation, should stay within the "water window" (-0.6 to 0.9 V versus Ag/AgCl in PBS) to prevent electrolysis of water [154,155]. A scan rate of 50 mV/s was used.…”