Characterization of a Glutamate Biosensor Based on a Novel Glutamate Oxidase Integrated into a Redox Hydrogel

Abstract

A newly isolated and purified glutamate oxidase was used to construct amperometric biosensors for glutamate monitoring. The enzyme-producing microorganism belongs to the genus of Streptomyces – Streptomyces sp. Z-11-6 – and is capable of producing extracellular L-glutamate oxidase. The microorganism was obtained by mutagenesis with HNO2 from a parent strain isolated from soil of Lypetskaya region, Russia, followed by conventional screening methods. The developed biosensor is based on a coupled enzyme system (glutamate oxidase and horseradish peroxidase), the enzymes being crosslinked to a redox polymer (PVI19-dmeOs) using poly(ethylene glycol) diglycidyl ether as crosslinker. The characteristics of the obtained biosensors were compared with those obtained for similarly constructed electrodes based on a commercially available glutamate oxidase from Yamasa Corp., Japan. The biosensors were operated at −50 mV (vs. Ag/AgCl 0.1 M KCl) in a flow injection system. Special attention has been focused on the selectivity of the biosensors, evaluating their responses in the presence of several potentially interfering substances, possibly present in brain microdialysates (ascorbic acid, aspartate, cysteine, dopamine, DOPAC, GABA, glutamine, glycine, 5-HIAA, HMPG, HVA, serotonin, tryptophan, tyrosine and uric acid). The biosensors based on the two enzymes displayed similar bioanalytical characteristics but different selectivity patterns.