A label-free electrochemical biosensor for highly sensitive detection of GM2A based on gold nanoparticles/conducting amino-functionalized thiophene polymer layer

In this study, a new immunosensor based on an indium tin oxide (ITO) substrate functionalized with gold nanoparticles (GNPs)/amino-functionalized thiophene polymer P(ThiAmn) multilayer was fabricated for impedimetric determination of GM2 activator protein (GM2A). To engineer the biosensor, a relatively simple approach composed of GNPs electrodeposition and ThiAmn electropolymerization was utilized. The use of GNPs and P(ThiAmn) increased the substrate surface area, which was beneficial to immobilize a large amount of antiGM2A biorecognition elements. The designed bifunctional layer served as a promising matrix material and provided an innovative sensor fabrication. Electrochemical techniques were employed to investigate the specific immuno-interaction process between biorecognition anti-GM2A antibodies and GM2A antigens. Apart from these techniques, spectral techniques were utilized for the characterization of different modified electrode surfaces. Under optimum conditions, GM2A was determined in a linear concentration range from 0.0185 to 111 pg/mL with a detection limit (LOD) of 5.8 fg/mL by electrochemical impedance spectroscopy (EIS) technique. This biosensor exhibited good reproducibility, long storage-stability, and excellent specificity for GM2A antigens. Additionally, this immunosensor was applied to quantify GM2A in commercial serum samples, and satisfactory results were obtained.