Direct electrochemistry and enzymatic activity of hemoglobin immobilized in ordered mesoporous titanium oxide matrix

The novel highly ordered mesoporous titanium oxide (mesoTiO2) materials, prepared by the “acid–base pairs” route, were firstly used for the immobilization of hemoglobin (Hb) and its bioelectrochemical properties were studied. FTIR and UV–vis spectroscopy demonstrated that Hb in the mesoTiO2 matrix could retain its native secondary structure. The CV results of Hb/mesoTiO2-modified electrode showed a pair of well-defined and quasi-reversible redox peaks centered at approximate −0.158 V (vs. SCE) in pH 6.0 phosphate buffer solution. It reflects the characteristic of Hb heme Fe (III)/Fe(II) redox couple with fast heterogeneous electron transfer rate. The immobilized Hb also displayed its good electrocatalytic activity for the reduction of hydrogen peroxide. The results demonstrate that the mesoTiO2 matrix may improve the protein loading with the retention of bioactivity and greatly promote the direct electron transfer, which can be attributed to its high specific surface area, uniform three-dimensional well-ordered porous structure, suitable pore size and biocompatibility.