Temporal Characterization of Perfluorinated Ion Exchange Coated Microvoltammetric Electrodes for In Vivo Use

Abstract

The temporal response of perfluorinated Ion exchange (PFIE) coated, microvoltammetric electrodes to rectangular concentration changes has been evaluated. These devices, with micrometer tip dimensions, have been designed for use as In vivo probes of electroactive neurotransmitters such as dopamine. The permeation of dopamine at electrodes with PFIE films thinner than 200 nm is sufficiently fast that distortion of the concentration pulse Is not apparent. The permeation rate of Ru(bpy)32+ Into these films varies with the applied potential waveform. At constant applied potential the measured permeation rate Increases with repetitive exposures. However, with fast-scan cyclic voltammetry (200 V s-1) repeated at 1-s intervals the permeation time for Ru(bpy)32+ remains relatively constant with repetitive exposures. Physical diffusion through these films predominates for this complex when sampled in this manner. The thickness of each Individual film can be determined from the permeation rates. The diffusion coefficient for dopamine in these thin PFIE films is found to decrease with a decrease in sodium ion concentration in solution. Voltammograms of dopamine In PFIE films are similar to those in solution except at high loading of the film where the buffer capacity can be exceeded. The electrodes are found to respond rapidly to the stimulated secretion of dopamine in the brain of an anesthetized rat. © 1987, American Chemical Society. All rights reserved.