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 behavior of a new biosensor, which exhibits a high catalytic activity for nitrite reduction and which consists of a maltose binding protein nitrite reductase fusion (MBP-Nir) immobilized on an electropolymerized film of PPB as an electrocatalyst, is also described, The insoluble perchlorate salt of the poly-(benzylviologen) dication was used to immobilize MBP-Nir onto an electrode previously modified with an electropolymerized 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 biosensor and nitrite anion were characterized using cyclic voltammetry and rotated disk electrode techniques, and a value of (4.6 +/- 0.5) x 10(3) M-1 s(-1) was obtained for the rate constant.