Comportamento eletroquímico de derivado piridínico diazônio para funcionalização de eletrodo

The electrochemical reduction of aryl diazonium salt is an efficient strategy to modify electrode surfaces once the mechanistic aspects of covalent bond between the electrode surface and aryl group have been widely studied [1].On the other hand, it was reported that the maltose binding protein (MBP) tag domain interacts strongly with N-(3-pyrrol-1-ylpropyl)-4,4′-bipyridinium electropolymerized film (PPB) [2]. In this work we described the electrochemical reduction of 1-[2-(diazoniophenyl)ethyl]-4,4’-bipyridinium, a derived pyridinium diazonium salt, onto glassy carbon electrodes (GCE). Consecutive cyclic voltammograms (CV) between 0.0 and -0.6 V were obtained in HCl 0.5 M solution containing the diazonium salt and the first peak showed a reduction at-0.47 V related to the diazonium group. Subsequent cathodic potential scans showed a displacement to smaller values followed by a significant decrease in current values. This behavior suggests that the GCE surface was modified. Studies using the cationic probe [Ru(NH3)6]3+ and the anionic probe [Fe(CN)6]3- confirmed the modification of the electrode surface and the positively charged of film. To demonstrated that the nonquaternized nitrogen of the 4,4’-bipydidyl group was available after modification, we investigated its coordination with [RuCl5(H2O)]2-. Therefore, the modified GCE was submerged in [RuCl5(H2O)]2- 50 mM solution for one hour, after that, CV were obtained in phosphate buffer solution 0.1 M pH 7.4 between -0.5 and 0.5 V until stabilization. The reduction and oxidation peaks formed at 0.13 and 0.24 V, respectively, were related to the RuII/RuIII redox process, as certain the coordination. These peaks were used to calculate the electrode cover of a monolayer. All modification steps were followed by Electrochemical Impedance Spectroscopy (EIS) and the results were converted in capacitance to best interpretation. Results obtained in this work suggest a promising methodology for future immobilization of MBP fusion proteins.