Ceramic-Based Multisite Platinum Microelectrode Arrays: Morphological Characteristics and Electrochemical Performance for Extracellular Oxygen Measurements in Brain Tissue

Ceramic-based multisite Pt microelectrode arrays (MEAs) were characterized for their basic electrochemical characteristics and used for in vivo measurements of oxygen with high resolution in the brain extracellular space. The microelectrode array sites showed a very smooth surface mainly composed of thin-film polycrystalline Pt, with some apparent nanoscale roughness that was not translated into an increased electrochemical active surface area. The electrochemical cyclic voltammetric behavior was characteristic of bulk Pt in both acidic and neutral media. In addition, complex plane impedance spectra showed the required low impedance (0.22 Mω; 10.8 ω cm²) at 1 kHz and very smooth electrode surfaces. The oxygen reduction reaction on the Pt surface proceeds as a single 4-electron reduction pathway at -0.6 V vs Ag/AgCl reference electrode. Cyclic voltammetry and amperometry demonstrate excellent electrocatalytic activity toward oxygen reduction in addition to a high sensitivity (-0.16 ± 0.02 nA μM^-1) and a low limit of detection (0.33 ± 0.20 μM). Thus, these Pt MEAs provide an excellent microelectrode platform for multisite O₂ recording in vivo in the extracellular space of the brain, demonstrated in anaesthetized rats, and hold promise for future in vivo studies in animal models of CNS disease and dysfunction.