Direct electrochemistry and electrocatalysis of myoglobin immobilized on a hexagonal mesoporous silica matrix

The direct electrochemistry of inyoglobin (Mb) immobilized oil a hexagonal mesoporous silica (HMS)-modified glassy carbon electrode was described. The interaction between Mb and HMS was investigated by using Fourier transfer infrared spectroscopy, nitrogen adsorption isotherm, and cyclic voltammetry. Two Couples of redox peaks corresponding to Fe(III) to Fc(II) conversion of the Mb intercalated in the mesopores and adsorbed on the Surface of the HMS were observed with the formal potentials of -0.167 and -0.029V in 0.1 M, pH 7.0, phosphate buffer solution, respectively. The electrode reaction showed a surface-controlled process with one proton transfer. The immobilized Mb displayed good clectrocatalytic responses to the reduction of both hydrogen peroxide (H2O2) and nitrite (NO2-), which were used to develop novel sensors for H2O2 and NO2-. The apparent Michaelis-Menten constants of the immobilized Mb for H2O2 and NO2- were 0.065 and 0.72 mM, respectively, showing good affinity. Under optimal conditions, the sensors could be used for the determinations of H2O2 ranging from 4.0 to 124 muM and NO2- ranging from 8.0 to 216 muM. The detection limits were 6.2 x 10(-8) and 8.0 x 10(-7) M at 3 sigma, respectively. The HMS provided a novel matrix for protein immobilization and the Construction of biosensors via the direct electron transfer of immobilized protein. (C) 2004 Published by Elsevier Inc.