Abstract
This chapter describes the development of a family of sensors based on a well-characterized glucose oxidase membrane and different coupling principles. The sensors are suited for the determination of saccharides, cofactors, and peroxidase substrates as well as for activities of amylases. Coupled enzyme reactions simulate the metabolic situation in organelles and microorganisms, which are frequently employed in biospecific electrodes. However, the application of mixtures of isolated enzymes offers several advantages. Because of the absence of contaminant enzyme activities, the selectivity of enzyme sensors is higher than that of organelle or microbial electrodes. Owing to the higher specific enzyme activity applicable in multienzyme electrodes, these are also superior with regard to sensitivity and response time. Interference caused by different substances (substrates, inhibitors, and activators) is a serious problem for the practical application of enzyme sensors. For coupled enzyme reactions the substrate of each particular enzyme may interfere if present in the sample. These interfering substrates can be eliminated by covering the enzyme sensor with an anti-interference layer. This layer contains immobilized enzymes that convert the disturbing substances to noninterfering products. In all enzyme electrodes using glucose oxidase (GOD), endogenous glucose from biological or food samples will interfere. This problem is overcome by converting the glucose by GOD and catalase to the electrode-inactive products, gluconolactone, and water. The anti-interference layer and the GOD-based enzyme membrane are two spatially separated linear enzyme sequences.
Published Version
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