Amperometric biosensor with PQQ enzyme immobilized in a mediator-containing polypyrrole matrix

Abstract

An amperometric biosensor for fructose was fabricated by co-immobilizing a pyrrolo quinoline quinone (PQQ) enzyme (fructose dehydrogenase, FDH) with mediator in a thin polypyrrole (PP) membrane. Electron transfer between the prosthetic PQQ of FDH and the transducer electrode was promoted through a mediator-containing PP interface. Two methods of sensor preparation are described. In one, FDH was potentiostatically adsorbed as a monolayer on a transducer electrode, and a very thin (equivalent to a monolayer of FDH) PP membrane containing a mediator was electrodeposited on the adsorbed FDH. In the other, FDH and mediator [hexacyanoferrate(II) or ferrocene] were co-immobilized on an electrode by electrochemical polymerization of pyrrole. In the former instance, a highly sensitive and selective response for fructose was obtained with a wide detection range of up to 30 mM with a linear range from 10 μm to 10 mM. However, the stability of the sensor was poor owing to the easy leakage of mediator. The stability of the sensor was significantly improved in the latter instance, with a dynamic range for fructose detection from 50 μM to 5 mM.