▎ 摘　　要

We develop a highly sensitive electrochemical immunosensor for the detection of a cluster of differentiation-44 (CD44) antigen, a breast cancer biomarker. The hybrid nanocomposite consists of graphene oxide, ionic liquid, and gold nanoparticles (GO-IL-AuNPs) immobilized on a glassy carbon electrode. GO favors the immobilization of antibodies because of the availability of oxygen functionalities. However, 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM.BF4) and AuNPs facilitate electron transfer and increase the effective surface area, which enhances the performance of the immunosensor. Furthermore, UV-visible, fourier transform infrared and Raman spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, voltammetry, and electrochemical impedance spectroscopy characterization techniques have been employed to investigate the structural and chemical properties of the nanomaterials. The quantitative detection of CD44 antigen has been accomplished via differential pulse voltammetry and EIS detection techniques. It has been quantified that the proposed immunosensor offers excellent detection ability in both phosphate-buffered saline (PBS) and serum samples. Under optimum conditions, the linear detection range of the immunosensor for CD44 antigen is 5.0 fg mL(-1) to 50.0 mu g mL(-1) and the limit of detection is 2.0 and 1.90 mu g mL(-1) as observed via DPV and EIS, respectively, in PBS. Additionally, the immunosensor has high sensitivity and specificity and can be successfully applied for the detection of CD44 antigen in clinical samples.