tThis study aims at developing an innovative electrochemical immunoassay system for an ultrasensitivedetection of human chorionic gonadotropin (hCG). hCG is a secretion of the placenta during pregnancyand gestational trophoblastic diseases. It increases as a consequence of abnormal placental invasion andplacental immaturity. Thus, an exact diagnosis of the concentration of hCG in urine or serum plays animportant role in monitoring trophoblastic diseases in all modern immunological pregnancy tests. Inthis work, a novel immunosensor is constructed by covalent immobilization of Pt nanoparticles (PtNPs)onto robust nanocomposite containing graphene (Gr), chitosan (Chit) and 1-methyl-3-octyl imidazoliumtetrafluoroborate as ionic liquid (IL) (Gr–IL–Chit). The nanocomposite not only led to increase the elec-trode surface area and accelerate the electron transfer kinetics, but also it could provide a highly stablematrix to enhance the loading amount of the nanoparticles. PtNPs acts as a linker to immobilize hCG anti-body onto the modified electrode. The amine groups of the antibody are covalently attached to PtNPs.Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spec-troscopy (EIS) were employed to trace the assembly process of the immunosensor. In this study, we usedRutin (RU) for the first time as the redox probe in the development of the electrochemical immunosensor.Upon biorecognition hCG to its antibody, peak current of RU decreased due to the formation of hCG–antihCG complex. Through differential pulse voltammetry (DVP) experiments, it was found that proposedimmunosensor could detect hCG at two broad linear ranges: 0.00106–2.12 and 2.12–350 mIU/mL and alow detection limit of 0.00035 mIU/mL. The immunosensor was found stable, reproducible, and highlyspecific for hCG detection.
