A novel label-free impedimetric immunosensor for sensitive detection of prostate specific antigen using Au nanoparticles/MWCNTs- graphene quantum dots nanocomposite

In this study, a novel impedimetric immunosensor based on Au nanoparticles@ multiwall carbon nanotubesgraphene quantum dots (AuNPs@MWCNTs-GQDs) was designed for the detection of prostate cancer biomarker with high sensitivity and selectivity in human serum. This label-free immunosensor was constructed by glassy carbon electrode surface coating with AuNPs@MWCNTs-GQDs as a signal amplifier and then an antibody against 'Prostate specific antigen)PSA(was immobilized on the modified electrode. The constructed immunosensor was characterized using transmission electron microscopy (TEM), Energy dispersive spectrometry (EDS), X-ray diffraction (XRD), Fourier transform infrared (FTIR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques. EIS measurements were applied to investigate the specific immunointeractions at the immunosensor surface utilizing redox probe [Fe (CN)(6)](3-/4-) to detect prostate specific antigen (PSA). The label-free immunosensor was successfully used to improve the analytical performance significantly and the impedance increment was linearly related to the PSA concentration in a wide linear range of 1-10,000 pg/mL and a low detection limit of 0.48 pg/mL. The responses of the proposed immunosensor in the real samples were compared with the commercial enzyme-linked immunosorbent assay (ELISA) method. The obtained were in good agreement with those obtained by the reference ELISA method. Therefore, this sensor with high sensitivity, selectivity and repeatability, could be utilized for early clinical diagnosis of prostate cancer in the clinical laboratories.