Effect of different self-assembled monolayers for MP-11 funzionalized electrodes

Immobilization of protein to solid surfaces is crucial in the development of solid-phase based bioanalytical techniques, biosensors and biofuelcells [1-4]. In recent years, one of the most widely employed procedures to immobilize enzymes onto solid electrodes has been the binding of these proteins to self-assembled monolayers (SAMs) constituted by bifunctional compounds. Microperoxidase 11 (MP-11) is an oligopeptide consisting of 11 amino acids and a covalently linked Fe(III)-protoporphyrin IX heme site, that reveals several advantages over usual peroxidases for the reduction of peroxides. It has a much smaller size, high stability and exhibits direct electrical communication with electrodes since its heme is exposed to the solution. In this work different self-assembled monolayer of cystamine (CYS), mercaptopropionic acid (MPA) and cysteamine (CYST) were used for MP-11 immobilization on a polycrystalline gold electrode. The adsorption and desorption of the SAM and the electrochemical behaviour of the MP-11 funzionalized electrodes were characterized by cyclic voltammetries. It was demonstrated that it is possible to develop cathodes based on MP-11 immobilization. The observed cathodic current using MP-11 functionalized electrode in the presence of hydrogen peroxide indicates the effective electro-biocatalyzed reduction of hydrogen peroxide by the modified cathode.