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 H₂O₂ 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.