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.