DEVELOPMENT AND APPLICATIONS OF AMPEROMETRIC BIOSENSORS

Abstract

Recent studies have led to the development of practical methods for making intimate connections between the redox centres of oxidoreductases and conductors, for example, the use of mediators such as ferrocenes or tetrathiafulvalenes. Based upon these advances, second generation enzyme sensors of simple, cheap construction able to operate on crude, untreated samples have been developed. For example, a small pen-type pocket glucose sensor has been developed for the market by Genetics International. The device shows considerable advantages over competing technologies, especially with respect to user-friendliness. Developments of such technology for non-medical applications, especially meat freshness monitoring and in situ monitoring of substrate levels in fermenters and bioreactors is described. Using related methods of electrochemical mediation, we have recently developed an advanced prototype biosensor for rapid assessment of microbial contamination of materials, including foodstuffs and industrial lubricants. This device which is simple and cheap to manufacture, allows measurement of microbial activity within two minutes. A major goal is exploitation of immunospecificity and DNA hybridisation. We have demonstrated substantially improved performance of commercial enzyme amplified ELISA methodology by replacing the end colour reaction by mediated amperometric systems. Methods for the electrochemical detection and measurement of antibodies labelled with non redox enzymes, especially alkaline phosphatase are also available. For example, appropriate phosphorylated derivatives of ferrocene are substrates for this enzyme and therefore facilitate sensitive mediated amperometric detection. Related amperometric DNA probes can be constructed by coupling such electrochemical methodology with for example, the avidin-biotin approach using peroxidase labelling. A new method for rapid determination of iron in physiological fluids exploiting the chelating agent desferrioxamine B is described.