Protein A immunosensor for the detection of immunoglobulin G by impedance spectroscopy.

A novel highly sensitive electrochemical impedimetric Protein A immunosensor for the determination of immunoglobulin G (IgG) was developed by immobilization of Protein A within a newly synthesized, and characterized polymer, poly(maleicanhydride-alt-decene-1). TiO2 nanoparticles (10-30 nm) were synthesized, characterized with X-ray diffraction, transmission electron microscopy and Brunauer-Emmett-Teller surface analysis. The electron transfer between IgG and the poly(maleicanhydride-alt-decene-1)-TiO2-Protein A is quasireversible with a formal potential of 225 mV vs Ag|AgCl. The response of the poly(maleicanhydride-alt-decene-1)-TiO2-Protein A immunosensor was proportional to IgG concentration with a correlation coefficient of 0.9963. The detection limit and linear range was 0.57 ng mL(-1) and 0.0062-500 μg mL(-1), respectively. Impedance measurments showed that synthesized TiO2 nanoparticles have better conducting properties compared with commercial degussa P25 TiO2 nanoparticles. The nonspecific binding of anti-MBP was 10 %. The label-free impedimetric immunosensor provided a simple and sensitive detection method for the specific determination of IgG in human serum.