The potential of biosensor technology in clinical monitoring and experimental research

Glucose or lactate biosensors are very useful for monitoring metabolism. Continuous monitoring of glucose is for example very important in diabetic patients. The measurement of lactate, a marker for oxygen deficiency, is used in the intensive care unit to monitor the patients' condition. In our laboratory we have developed two types of on-line biosensors to measure in vivo glucose and lactate: a sandwich-type biosensor and, very recently, a miniaturized flow-through biosensor. These biosensors are not placed in the body itself, but are connected to implanted microdialysis or ultrafiltration probes. Both types of biosensors are based on the oxidation of substrate using glucose oxidase or lactate oxidase and electrochemical detection. In the sandwich-type sensor, the enzymes are physically immobilized between two cellulose nitrate filters, and operate with ferrocene as a mediator. In the miniaturized biosensor, with an internal volume of 10-20 nanolitres, the enzymes are immobilized on the electrode via in situ encapsulation in poly(1,3-phenylenediamine). In this review we shall explain the working of these biosensors, and describe their application in clinical monitoring and experimental research.