Coupling of immunoassays with enzymatic recycling electrodes

Enzymatic substrate regeneration is a tool to enhance the sensitivity of enzyme electrodes both for substrate analysis and immunoassays. The combination of immunoreactions and electrode based substrate recycling connects specific recognition of an analyte with highly sensitive detection. Most important for this field of application is the sensitivity, which permits to detect a label at very low concentration. Enzymatic substrate regenerating systems are reviewed which are based on sensors using acceptor dependent dehydrogenases in combination with phenol oxidases and the lactate oxidase/lactate dehydrogenase couple and applied as sensitive label detectors in electrochemical immunoassays. Label compounds are either redox-active dyes or enzymes. The label enzymes measured so far are alkaline phosphatase and beta -galactosidase.