Optimization of the Design and Operating Conditions of an Amperometric Biosensor for Glutamate Concentration Measurements in the Blood Plasma

Today, the concentration of glutamate in the patient ' s blood is an important indicator in medical diagnostics; therefore, it is necessary to have a simple, accurate, and fast tool to obtain the data. Here, a recently developed amperometric glutamate-sensitive biosensor was optimized to improve its characteristics. The platinum disk electrode was used as a transducer. As a bioselective element we used the enzyme glutamate oxidase, covalently crosslinked with bovine serum albumin by glutaraldehyde. Circumstances of enzyme immobilization on the transducer's surface were optimized (enzyme and glutaraldehyde concentrations and immobilization duration). To test the ability of this biosensor to work in biological environments containing complex biological substances, the influence of the working solution was investigated (concentration of the working buffer, its temperature, presence of the protein in the analyzed sample). The linear range of biosensor was from 5 to 600 mu M of glutamate and the sensitivity was 150-200 nA/mM. Measurements of glutamate concentrations in the blood plasma were performed by biosensor and glutamate dehydrogenase assay. The linear correlation between the methods was found in a range of 50.4-182.5 mu M (R-2=0.99). Thus, it has been shown that the developed biosensor makes it possible to measure the concentration of glutamate in blood plasma.