Immobilized Enzyme Technology

IMMOBILIZED ENZYME TECHNOLOGY

Enzymes also form the basis of many diagnostic tests used in clinical medicine. For example, glucose oxidase, an enzyme used in blood glucose analysis, is obtained commercially from Aspergillus niger. Although the design of glucose blood monitoring test strips has become more refined, the basic design remains the same. Glucose oxidase is sandwiched between polycarbonate and cellulose acetate membranes. When a pinprick volume of blood is applied, the polycarbonate membrane allows the diffusion of glucose into the sandwich but limits entry of larger molecules thus reducing background contaminants. The enzyme oxidizes the glucose, resulting in the formation of hydrogen peroxide. The hydrogen peroxide diffuses through the cellulose membrane where it is measured amperometrically following interaction with a platinum electrode. More recently, several types of implantable glucose oxidase electrodes have been developed experimentally for continuous monitoring of blood glucose levels in diabetics. While there are challenges relating to enzyme inactivation in vivo, glucose calibration, and immune response there are, nevertheless, a number of major research efforts in this area and indeed the US Food and Drug Administration (FDA) has recently approved a wireless subcutaneous sensor that continuously monitors patient glucose levels for 7 days. It is likely that biosensors employing immobilized enzymes which are potentially useful for monitoring many substances of clinical importance will become readily available in the not-too-distant future.