Analytical Sciences

Simultaneous Quartz Crystal Microbalance-Electrochemical Impedance Spectroscopy Study on the Adsorption of Anti-human Immunoglobulin G and Its Immunoreaction at Nanomaterial-modified Au Electrode Surfaces

Xueen JIA, Qingji XIE, Youyu ZHANG, and Shouzhuo YAO

Key Laboratory of Chemical Biology & Traditional Chinese Medicine Research (Ministry of Education), Hunan Normal University, Changsha 410081, P. R. China

The quartz crystal microbalance method (QCM), in combination with electrochemical impedance spectroscopy (EIS), has been utilized to monitor in situ anti-human IgG adsorption on several Au-based surfaces, bare Au, nanogold/4-aminothiophenol (4AT)/Au, and multi-walled carbon nanotubes (MWCNT)/Au, and succeeding human IgG reactions. Also, the immobilization protocol of anti-human IgG via its glutaraldehyde (GA) cross-linking with self-assembled 4AT on an Au electrode and the subsequent surface immunoreaction were examined. The resonant frequency (f₀) and the motional resistance (R₁) of the piezoelectric quartz crystal (PQC) as well as electrochemical impedance parameters were measured and discussed. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) of the ferricyanide/ferrocyanide couple were examined before and after electrode modification, the antibody adsorption and antibody-antigen reactions. We found that the amount for antibody adsorption was the greatest on the colloid Au modified surface, and that at MWCNT ranked the second, while specific bioactivity was almost identical on the four kinds of surfaces. Two parameters simultaneously obtained at the colloid Au modified surface, Δf₀ and ΔC_s (interfacial capacitance), have been used to estimate the association constant of the immunoreaction.

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