Direct electrochemistry and electrocatalytic properties of hemoglobin immobilized on a carbon ionic liquid electrode modified with mesoporous molecular sieve MCM-41

The direct electron transfer and electrocatalysis of hemoglobin (Hb) entrapped in the MCM-41 modified carbon ionic liquid electrode (CILE) were investigated by using cyclic voltammetry in 0.10 M pH 7.0 phosphate buffer solution (PBS). Due to its uniform pore structure, high surface areas and good bio-compatibility, the mesoporous silica sieve MCM-41 provided a suitable matrix for immobilization of biomolecule. The MCM-41 modified CILE showed significant promotion to the direct electron transfer of Hb, which exhibited a pair of well defined and quasi-reversible peaks for heme Fe(III)/Fe(II) with a formal potential of -0.284V (vs. Ag/AgCl). Additionally, the Hb immobilized on the MCM-41 modified carbon ionic liquid electrode showed excellent electrocatalytic activity toward H2O2. The electrocatalytic current values were linear with increasing concentration of H2O2 in a wide range of 5-310 mu M and the corresponding detection limit was calculated to be 5 x 10(-8) M (S/N = 3). The surface coverage of Hb immobilized on the MCM-41 modified carbon ionic liquid electrode was about 2.54 x 10(-9) mol cm(-2). The Michaelis-Menten constant K-m(app) of 214 mu M indicated that the Hb immobilized on the modified electrode showed high affinity to H2O2. The proposed electrode had high stability and good reproducibility clue to the protection effect of MCM-41 and ionic liquid, and it would have wide potential applications in direct electrochemistry, biosensors and biocatalysis. (C) 2010 Elsevier B.V. All rights reserved.