Fig. 3

Label-free impedimetric immunosensor for GFAP detection. L-cys was explored as a substrate for the immunization of GFAP antibodies because it enables the guided and stable immobilization of GFAP antibodies. In addition, it served as a linker between GFAP antibodies and Au NPs/SPCE. Additionally, the combination of L-cys and Au NPs is likely to exhibit high effective surface area and stability. Furthermore, 1% BSA was adsorbed on the surface to block the –COOH groups and the non-interacting –NH₂ groups of the GFAP antibody, and prevent non-specific binding. In this label-free impedance immunosensor, testing samples can immobilize anti-GFAP antibodies via covalent attachment onto L-cys/ Au NPs that were modified with anti-GFAP/L-cys/Au Nps/SPCE for the detection of GFAP. Finally, using EIS to measure the ΔRct, which had a linear correlation with GFAP concentration. BSA was adsorbed on the surface to block the activated carboxyl group and prevent non-specific binding. L-cys L-cysteine, GFAP glial fibrillary acidic protein, Au NPs gold nanoparticles, SPCE screen printed electrode, EIS electrochemical impedance spectroscopy, ΔRct transfer resistance differences