BIOPHYSICAL CHEMISTRY,ISSN 0301-4622 Volume 130,Issue 3, 1 Nov 2007, Pages 122-131

Immobilization of hemoglobin on electrodeposited cobalt-oxide nanoparticles: Direct voltammetry and electrocatalytic activity

عبدالله سليمي*1,2 , رحمان حلاج1 , سعيد سلطانيان2

1- دانشگاه کردستان دانشکده علوم گروه شيمي 2- دانشگاه کردستان مرکز تحقيقات فناوري نانو

Abstract: Cyclic voltammetry at potential range ? 1.1 to 0.5 V from aqueous buffer solution (pH 7) containing CoCl2 produced a well defined cobalt oxide (CoOx) nanoparticles deposited on the surface of glassy carbon electrode. The morphology of the modified surface and cobalt oxide formation was examined with SEM and cyclic voltammetry techniques.Hemoglobin (Hb) was successfully immobilized in cobalt-oxide nanoparticles modified glassy carbon electrode. Immobilization of hemoglobin onto cobalt oxide nanoparticles have been investigated by cyclic voltammetry and UV–visible spectroscopy. The entrapped protein can take direct electron transfer in cobalt-oxide film. A pair of well defined, quasi-reversible cyclic voltammetric peaks at about ? 0.08 V vs. SCE (pH 7), characteristic of heme redox couple (Fe(III)/Fe(II)) of hemoglobin, and the response showed surface controlled electrode process. The dependence of formal potential (E0?) on the solution pH (56 mV pH? 1) indicated that the direct electron transfer reaction of hemoglobin was a one-electron transfer coupled with a one proton transfer reaction process. The average surface coverage of Hb immobilized on the cobalt oxide nanoparticles was about 5.2536 × 10? 11 mol cm? 2, indicating high loading ability of nanoparticles for hemoglobin entrapment. The heterogeneous electron transfer rate constant (ks) was 1.43 s? 1, indicating great of facilitation of the electron transfer between Hb and electrodeposited cobalt oxide nanoparticles. Modified electrode exhibits a remarkable electrocatalytic activity for the reduction of hydrogen peroxide and oxygen. The Michaels–Menten constant Km of 0.38 mM, indicating that the Hb immobilized onto cobalt oxide film retained its peroxidases activity. The biosensor exhibited a fast amperometric response < 5 s, a linear response over a wide concentration range 5 ?M to 700 ?M and a low detection limit 0.5 ?M. According to the direct electron transfer property and enhanced activity of Hb in cobalt oxide film, a third generation reagentless biosensor without using any electron transfer mediator or specific reagent can be constructed for determination of hydrogen peroxide in anaerobic solutions.

Keywords:Cobalt-oxide; Nanoparticles; Hemoglobin; Direct voltammetry; Electrodeposition; Biosensor

*Corresponding Auther:  absalimi@uok.ac.ir - absalimi@yahoo.com