An electrochemical amperometric immunobiosensor for label-free detection of α-fetoprotein based on amine-functionalized graphene and gold nanoparticles modified carbon ionic liquid electrode

A sensitive label-free amperometric immunosensor was developed based on the amine-functionalized graphene (GR-NH2) and gold nanoparticles (AuNPs) composite modified carbon ionic liquid electrode (CILE). CILE was fabricated by using an ionic liquid of 1-octyl-3-methylimidazolium hexafluorophosphate as binder. The nanocomposite AuNPs/GR-NH2 had prominent biocompatibility, good electron transfer ability, large specific surface area, and primarily excellent adsorption. The negatively charged AuNPs could be adsorbed on the positively charged GR-NH2 modified CILE surface by electrostatic adsorption, and then to immobilize α-fetoprotein antibody (anti-AFP) for the assay of α-fetoprotein (AFP). The fabricated procedures and electrochemical behaviors of the immunosensor were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The anti-AFP/AuNPs/GR-NH2 modified CILE was sensitive to AFP in linear relation between 1 and 250 ng mL−1 with the correlation coefficient of 0.995, and the detection limit (S/N = 3) was 0.1 ng mL−1 under the optimal conditions. In addition, the proposed immunosensor exhibited good sensitivity, selectivity, stability and long-term maintenance of bioactivity and it may be used to immobilize other biomoleculars to develop biosensor for the detection of other antigens or biocompounds.