Direct electrochemistry and electrocatalysis of hemoglobin immobilized in bimodal mesoporous silica and chitosan inorganic-organic hybrid film

Hemoglobin modified electrode was successfully fabricated to realize direct electrochemistry by immobilizing of Hemoglobin (Hb) in bimodal mesoporous silica (BMS) and chitosan (CS) inorganic-organic hybrid film. Here, BMS acted as a support to immobilize Hb due to its large pores and CS acted as a binder to increase film adherence and stabilizer to prevent the leakage of Hb. The resulting electrode (Hb/BMS/CS) gave a well-defined, reversible redox couple for HbFe(III)/Fe(II) with a formal potential of about -0.32 V (vs. Ag/AgCl) in pH 7.0 phosphate buffer solution. Hb/BMS/CS electrode showed a better electrocatalytial performance to HZOZ with wider linear detection range, lower detection limit, and higher sensitivity than that at electrode without BMS. The improved electrocatalytic performance for Hb/BMS/CS electrode was possibly contributed to BMS bimodal structure, whose large pores with 10-40 nm provide favorable conditions for protein immobilization and small pores with 2-3 nm avoid the mass-transfer limitations. In addition, UV-Vis and FTIR spectra indicated that Hb well maintained its native structure in the hybrid film. (C) 2007 Elsevier B.V. All rights reserved.