A NITRITE BIOSENSOR BASED ON A MALTOSE-BINDING PROTEIN NITRITE REDUCTASE FUSION IMMOBILIZED ON AN ELECTROPOLYMERIZED FILM OF A PYRROLE DERIVED BIPYRIDINIUM

The preparation and electrochemical characterization of glassy carbon electrodes (GCEs) modified with electropolymerized films of the cation N-(3-pyrrol-1-yl-propyl)-4,4'-bipyridine (PPB) are described. The beh avior of a new biosensor, which exhibits a high catalytic activity for nitrite reduction and which consists of a maltose binding protein nit rite reductase fusion (MBP-Nir) immobilized on an electropolymerized f ilm of PPB as an electrocatalyst, is also described, The insoluble per chlorate salt of the poly-(benzylviologen) dication was used to immobi lize MBP-Nir onto an electrode previously modified with an electropoly merized film of PPB, The electropolymerized film of PPB on the GCE is redox active and exhibits special electron-transfer properties toward the MBP-Nir layer but not toward Nit (Nir without MBP fusion attached) , suggesting an intimate interaction between the PPB film and the MBP- Nir layer. The kinetics of the catalytic reaction between the biosenso r and nitrite anion were characterized using cyclic voltammetry and ro tated disk electrode techniques, and a value of (4.6 +/- 0.5) x 10(3) M-1 s(-1) was obtained for the rate constant.