An amperometric inhibitor biosensor for the determination of reduced glutathione (GSH) without any derivatization in some plants

In this study, an amperometric biosensor based on cucumber tissue homogenate was developed for the determination of glutathione. Cucumber (Cucumis sativus L.) tissue homogenate was used as the biological material. The cucumber tissue homogenate was cross-linked with gelatine using glutaraldehyde and fixed on a pretreated teflon membrane. The principle of the measurements was based on the determination of the decrease in the differentiation of oxygen level which had been caused by the inhibition of ascorbate oxidase in the biological material by glutathione. Determinations were carried out by standard curves which were obtained by the measurement of the decrease in the consumed oxygen level related to glutathione concentration. Optimization and characterization studies of the biosensor were carried out and a linearity in the gamma-L-glutamyl-L-cysteinyl-glycine (GSH) concentration range 0.1-2 muM was obtained when 600 muM ascorbic acid was used as a substrate. The repeatability experiments (n = 7) revealed that for 1.5 muM GSH, the average value ((x) over bar), standard deviation (S.D.) and variation coefficient (C.V.) were 1.517 muM, 4.72 x 10(-5), 3.11%, respectively. The biosensor useful lifetime was at least 2 months. The results of some plant samples analyzed with the presented biosensor agreed well with the spectrophotometric method (Ellman's reagent) used as a reference. (C) 2003 Elsevier B.V. All rights reserved.