Direct electron transfer and electrocatalysis of hemoglobin adsorbed on coralloid gold nanostructures

Three-dimensional (3D) coralloid gold nanostructures (CGNs) have been fabricated by using an electrochemical growth method on the ITO glass substrates coated with agarose gel. Characterization by a variety of complementary techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-vis spectroscopy confirmed the distribution of CGNs on the ITO glass substrates. The adsorption behaviors of hemoglobin (Hb) on the CGNs-modified ITO (CGNs/ITO) electrodes were investigated by UV-vis spectroscopy and electrochemical methods, and the results demonstrated that 3D CGNs could provide good microenvironment for loading biomolecules and retaining their biological activity. Direct electron transfer of the adsorbed Hb exhibited a couple of stable and well-defined redox peaks centered at about -0.121 V and -0.041 V (vs. SCE) in 0.1 mol L(-1) pH 7.0 PBS. The electron transfer rate constant is 0.78 s(-1) at a scan rate of 0.1 V (s-1). The adsorbed Hb in the CGNs displayed a rapid amperometric response to the reduction of hydrogen peroxide (H2O2) for a broad linear range from 1.0 x 10(-6) mol LV(-1) to 5.0 x 10(-3) mol L(-1) with the detection limit of 3.0 x 10(-7) mol L(-1) (S/N = 3).