A highly sensitive electrochemical immunosensor was developed to detect hCG based on immobilization of hCG-antibody (anti-hCG) onto robust nanocomposite containing Gr, Chit, 1-methyl-3-octyl imidazolium tetra fluoro borate ionic liquid (IL) (Gr-IL-Chit). AuNPs were used to immobilize hCG antibody on the modified electrode. The amine groups of the antibody are covalently attached to AuNPs/Gr- IL-Chit nanocomposite. CV, EIS and SEM were employed to characterize the assembly process and the performance of the immunosensor. DPV and EIS studies demonstrated that the formation of antibody-antigen complexes decreased peak current and increased Rct of [Fe(CN)6]3−/4− redox pair at the AuNPs/Gr-IL-Chit/GCE. The optimization of the pH of supporting electrolyte and the incubation time were studied in details. Because of the synergistic effect of IL, Chit and Gr and the unique properties of AuNPs, the obtained immunosensor exhibited a wide linear response to hCG in two ranges from 0.005-1.484 and 1.484-411.28 (mIU ml-1). A relatively low detection limit of 0.0016 mIU ml-1 (S/N = 3) was calculated from DPV. Satisfactory results were obtained for determination of hCG in human serum samples.
