Biosensors. From the Glucose Electrode to the Biochip

Abstract

The biosensor was born over forty years ago, when Clark and Lyons [1] had the idea of carrying out specific glucose concentration measurements by detecting the oxygen consumed during the enzymatic oxidation of this metabolite, catalysed by glucose oxidase, using an electrochemical sensor. The enzyme was used in solution, confined to the end of the sensor. In parallel, during the 1960s, more and more studies were being carried out on the properties of immobilised enzymes and their use. Then in 1967 an enzyme electrode for specific glucose assays was described by Updike and Hicks [2]. In this work, glucose oxidase was incorporated in a polyacrylamide gel. In 1969, by immobilising urease in the same type of matrix, Guilbault and Montalvo [3] described the first enzyme electrode associated with a potentiometric measurement for assaying urea by detecting ammonium ions (NH⁺ ₄ produced during the reaction. This founding research opened the way to many developments associating not only enzymes and electrochemical detection, but also other types of biomolecules and other detection methods [4–6]. A biosensor can thus be defined more precisely as any measurement device in which the sensitive component is of a biological nature. The sensitive biological element, or bioreceptor, is able to specifically recognise a target substance present in a complex medium. This specific recognition generates a physicochemical signal which is then transformed by a transducer into a measurable and interpretable electrical signal (see Fig. 16.1).