Sensetive electrochemical immunosensor for human chorionic gonadotropin based on gold nanoparticle/graphene-ionic liquid-chitosan nanocomposite film modified glassy carbon electrode

A novel and highly sensitive electrochemical immunosensor was developed to detect human chorionic gonadotropin (hCG) based on immobilization of hCG–antibody (anti-hCG) onto robustnanocomposite containing Graphene (Gr), Chitosan (Chit), 1-methyl-3-octyl imidazolium tetrafluoro borate as ionic liquid (IL) (Gr-IL-Chit) and then Gold nanoparticles (AuNPs) were used as a linker to immobilize hCG antibody onto the modified electrode. The amine groups of theantibody are covalently attached to an AuNPs/Gr-IL-Chit nanocomposite. Cyclic voltammetry(CV), impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were employedto characterize the assembly process and the performance of the immunosensor. Differentialpulse voltammetry (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 incubationtime 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 to 1.484 and 1.484 to 411.28 (mIU/mL). A relatively low detection limit of0.0016 mIU/mL (S/N =3) was calculated from DPV. Satisfactory results were obtained for determination of hCG in human serum samples. Moreover, this immunosensor has dramatic stability and repeatability.

Keywords:

Electrochemical immunosensor , Human chorionic gonadotropin , Nanocomposite , Differential pulse voltammetry , Impedance spectroscopy