Direct electron transfer of protein immobilized on mesoporous molecular sieves matrix

The direct electron transfer of different heme proteins immobilized on mesoporous molecular sieves was studied. The direct electrochemistry of horseradish peroxidase (HRP), hemoglobin (Hb) and myoglobin (Mb) immobilized on hexagonal mesoporous silica (HMS) was described, respectively. The immobilized heme proteins at modified glassy carbon electrodes (GCE) showed good direct electrochemical behaviors, which depended on the specific properties of the HMS. Two couples of redox peaks corresponding to the Fe(III) to Fe(II) conversion of the proteins intercalated in the mesopores and adsorbed on the surface of the HMS in 0.1 mol·L^-1, pH 7.0 PBS (phosphate-buffered saline), respectively, were observed. The amount of proteins intercalated in the mesopores of HMS was proved to be related to the porous size. The result showed the electrode processes to be surface-controlled electrode processes with a single proton transfer. The interactions between proteins and HMS were investigated by using FT-IR, N₂ adsorption isotherms and electrochemical methods, and the new biosensors of hydrogen peroxide (H ₂O₂) and nitrite (NO₂^-) were constructed. These works extended the application of HMS in immobilizing protein, the direct electron transfer of protein and the construction of reagentless biosensors.