Abstract
α-Human atrial natriuretic peptide (ANP), a marker peptide hormone for heart diseases, was determined at femtomolar levels by an electrochemical enzyme immunoassay. Alkaline phosphatase (ALP) was used as a labeling enzyme. Changes in ALP activity were monitored using a lipid-modified glucose oxidase electrode based on bioelectrocatalytic redox recycling as follows. p-Aminophenol (PAP), the product of the ALP enzyme reaction, was electrochemically oxidized at the electrode to p-iminoquinone (PIQ), and then reduced back by glucose oxidase which was stably immobilized on the electrode surface. The consumption/regeneration cycle of p-aminophenol resulted in a great enhancement in the sensitivity of the enzymatic immunoassay.
