Millisecond Time Resolved Electrochemical Detection of Non-Electroactive Neurotransmitter Release

Abstract

Acetylcholine and glutamate are highly important non-electroactive neurotransmitter in the mammalian central nervous system. A fast, sensitive method to detect the release of acetylcholine and glutamate at the surface of a single cell is needed to gather data about the kinetics of exocytosis events in pathways involving these signaling molecules.To this end, carbon fiber electrodes have been modified with electrodeposited gold nanoparticles to increase the effective electrode surface area and provide a high curvature surface for enzyme attachment. For detection of acetylcholine, acetylcholine esterase and choline oxidase were deposited onto the nanoparticle coated electrode surfaces to catalyze acetylcholine to hydrogen peroxide for electrochemical detection. The functionalized electrodes have been characterized to determine the KM and Vmax of the enzymes as well as the total enzyme coverage and gold nanoparticle surface area. This information was further used to evaluate the conditions for optimal retained enzyme activity of the sensor surface. Similarly, glutamate oxidize was placed onto the surface of electrodes plated with nanoparticles. The sensors were tested for acetylcholine and glutamate release from a synthetic cell model for exocytosis, and providing time resolved detection of single vesicle release events on the order of millisecond time scale.