In vivo and in vitro comparison of the charge injection capacity of platinum macroelectrodes

Abstract

Platinum (Pt) is the most commonly used metal for stimulating electrodes. This study aims to determine the amount of charge that can be delivered without causing irreversible electrochemical reactions (charge injection capacity, Qinj) of Pt macroelectrodes (geometric surface area >0.001 cm2) in vitro and in vivo using voltage transient measurements. Pt macroelectrodes were stimulated with biphasic charge-balanced cathodic-first constant-current pulses in phosphate buffered saline. Potential excursions were measured (versus AgAgCl electrode) and used to determine Qinj. The in vitro Qinj were compared to those measured in vivo following: acute and chronic implantation close to the retina; chro..