[Biosensors and clinical analysis]

Abstract

The determination of organic compounds in blood is important in clinical analysis. Most analysis of organic compounds are based on spectrometric methods. However, these methods involve complicated procedures and require a long time for the reaction to occur. Bioelectrochemical sensors employing immobilized biocatalysts have definite advantages. For medical purposes, miniaturization of enzyme sensors is essential. Miniaturized and highly selective enzyme sensors have been developed by combining enzyme immobilization techniques with silicon technologies. Glucose measurement in blood is the most important and essential assay in the clinical field. For this purpose, we have developed various micro biosensors for glucose measurements. Generally, enzymatic determination of glucose is based on the following reaction (s); (formula; see text) According to the above equation, 4 different micro-glucose sensors were developed; 1) a sensor based on the measurement of produced hydrogen peroxide, 2) a sensor based on the measurement of consumed oxygen, 3) a sensor based on the measurement of enthalpy change during the enzymatic reaction, 4) a sensor based on the measurement of the amount of proton produced, and 5) a sensor based on the measurement of the light emission during enzymatic reaction. For these purposes, various kinds of transducers were used. A micro-hydrogen peroxide electrode, a micro-oxygen electrode, a thermistor, an ISFET (ion selective field effect transistor), and a photon counter. The determination of antibodies, or antigens is also very important in clinical analysis. Several types of immuno-sensors have been developed for these purposes. Considering the integration of immuno-sensors, the miniaturization of immuno-sensors is also required. This review deals with our current study on micro-biosensors for clinical analysis.