Non-electrode biosensors in clinical biochemistry

This review covers biosensors based on piezoelectric crystals, optical systems, field effect transistors and thermistors. Piezoelectric crystal or microgravimetric biosensors have been used for immunoassay. Optical biosensors are described in which waveguides are used to transmit changes in optical characteristics or, in an innovative mode, the evanescent wave component of a completely internally-reflected light beam is used to study optical changes. Optical biosensors have been used in immuno and in enzyme-based assays. Field effect transistors detect changes in ion concentrations and have been applied to the detection of biochemical reactions which involve a change in concentration of a specific ion. Thermistors are used to monitor the heat produced as the result of an exothermic enzymatic reaction and this has been applied to the assay of compounds or enzymes of interest. Biosensors may find a role in clinical biochemistry in low volume testing, patient self-testing and in vivo monitoring.