Measurement of Glutamate Neurotransmitter in the Brain of Male Rat Using Glutamate Oxidase-Based Electrochemical Biosensor

Glutamate oxidase (GluOx; EC 1.4.3.11), as an oxidoreductase enzyme, catalyzes the oxidation of glutamate to α-ketoglutarate, ammonia, and hydrogen peroxide (H2O2). In this reaction, the amount of H2O2 is proportional to the concentration of glutamate and its concentration can be measured by using an electrochemical biosensor. The same as other enzyme-based biosensors, glutamate oxidase is one of the key elements in the construction of glutamate biosensors. Such biosensors are fully capable of identifying biological analytes, such as glutamine, ammonia, and creatinine. In addition, glutamate oxidase-based biosensors have many applications in quantitative and qualitative measurements in analytical chemistry, determining the quality of food products, as well as early detection of heart and liver disorders in clinical biochemistry. Considering the importance of the glutamate neurotransmitter in various brain functions, this study investigated its measurement in the brain of male Wistar rats by using a glutamate oxidase-based biosensor.

In order to measure glutamate, initially, a glutamate oxidase-based biosensor was made by simultaneously immobilizing the enzyme and chitosan on the platinum electrode surface. Then, the animals were sacrificed, and their brains were removed and placed in a phosphate buffer. Afterward, the contents of the brain were centrifuged to create a completely uniform mixture. Finally, the concentration of glutamate in the prepared brain samples was measured using the fabricated biosensor by the cyclic voltammetry technique.

The results of cyclic voltammetry experiments showed that the cathodic peak current of the fabricated biosensor was 0.812 µA. Moreover, the calibration curve indicated that the biosensor response was linear up to 1 mM and glutamate concentration in brain samples was also equal to 63.5 µM.

The cyclic voltammetry experiments showed that the concentration of H2O2, which is produced during the catalytic activity of glutamate oxidase, is completely proportional to the concentration of glutamate oxidase. Furthermore, this study showed that, despite the very low concentration of glutamate neurotransmitters, the glutamate oxidase-based electrochemical biosensor can precisely identify it qualitatively and quantitatively in biological samples, such as brain samples.