AMPEROMETRIC BIOSENSOR WITH PQQ ENZYME IMMOBILIZED IN A MEDIATOR-CONTAINING POLYPYRROLE MATRIX

An amperometric biosensor for fructose was fabricated by co-immobilizi ng a pyrrolo quinoline quinone (PQQ) enzyme (fructose dehydrogenase, F DH) with mediator in a thin polypyrrole (PP) membrane. Electron transf er between the prosthetic PQQ of FDH and the transducer electrode was promoted through a mediator-containing PP interface. Two methods of se nsor preparation are described. In one, FDH was potentiostatically ads orbed as a monolayer on a transducer electrode, and a very thin (equiv alent to a monolayer of FDH) PP membrane containing a mediator was ele ctrodeposited on the adsorbed FDH. In the other, FDH and mediator [hex acyanoferrate(III) or ferrocene] were co-immobilized on an electrode b y electrochemical polymerization of pyrrole. In the former instance, a highly sensitive and selective response for fructose was obtained wit h a wide detection range of up to 30 mM with a linear range from 10 mu M to 10 mM. However, the stability of the sensor was poor owing to the easy leakage of mediator. The stability of the sensor was significant ly improved in the latter instance, with a dynamic range for fructose detection from 50 muM to 5 mM.