NEW ELECTROPOLYMERIZABLE AMPHIPHILIC VIOLOGENS FOR THE IMMOBILIZATIONAND ELECTRICAL WIRING OF A NITRATE REDUCTASE

A new series of amphiphilic viologens functionalized by one or two pyr role groups have been synthesized and electrochemically characterized. This functionalization has allowed the preparation of poly(pyrrole-vi ologen) films by oxidative electropolymerization. The electropolymeriz ation of nitrate reductase (NR) + amphiphilic pyrrole viologen mixture s previously adsorbed on electrode surfaces provides the immobilizatio n of the enzyme in N-substituted viologen polypyrrole films generated in aqueous solution. Furthermore, the electrogenerated redox polymers simultaneously entrap the enzyme and establish an electrical communica tion between IVR and the electrode surface. Since NR catalyzes the red uction of nitrate to nitrite mediated by the viologen redox couple (V2 +/.+), the resulting bioelectrodes potentiostated at -0.7 V act as a b iosensing device for the amperometric detection of nitrate. The influe nce of the degree of cross-linking of the host polymers as well as the bulkiness of the viologen groups have been correlated to the bioelect rode performance for nitrate determination. In addition, different pol ymer-enzyme configurations have been compared, the highest sensitivity for nitrate being 13.8 mA M-1 cm(-2). (C) 1997 Elsevier Science B.V.