Flow-injection Electrochemical Biosensors with Multiple Functions

Abstract

As analytical reagents, enzymes offer two characteristics of paramount importance: high selectivity (and occasionally specificity) and the capability of self-regeneration via the catalytic cycle. The first of these properties is widely recognized and used; the second normally requires the use of immobilized enzymes. In addition, if the immobilized enzymes are used in the flow systems, handling is minimized and reproducibility is enhanced. On the other hand, electrochemical detection eliminates many of the difficulties encountered in photometric detection, such as the overlap of adsorbing species and turbidity. Therefore, highly selective flow-sensor systems for biochemical analysis are proposed by coupling immobilized enzymes with electrochemical sensors. In principle, they can be divided into two types. The first of these types is the enzyme electrode in which the immobilized enzyme is in direct contact with the electrochemical sensor. In the second type, the enzyme, immobilized on a solid support (enzyme reactor), is incorporated in the flow line into which the analyte is injected and the product generated is detected with an electrochemical sensor downstream.A general view of these applications and recent developments is given here with the hope of providing a practical perspective of the use of enzymes in the various flow-injection systems.