Ultrasensitive photoelectrochemical immunosensor based on a g-C3N4/SnS2 nanocomposite for prostate-specific antigen detection

Abstract Herein, a novel amplified photoelectrochemical immunosensor based on a g-C3N4/SnS2 nanocomposite was constructed and applied to detect prostate-specific antigen (PSA). The prepared nanocomposite materials were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), ultraviolet–visible absorption spectroscopy (UV–vis), and Fourier transform infrared spectroscopy (FT-IR). The results indicate that g-C3N4/SnS2 nanocomposite materials were successfully synthesized. In a typical assembly process, the immunosensor was constructed by embellishing fluorine-doped tin oxide (FTO) electrode with g-C3N4/SnS2 nanocomposite, chitosan (Chito), monoclonal antibody (Ab1), blocking agent bovine serum albumin (BSA), prostate-specific antigen (PSA), and polyclonal antibody-CdS (Ab2-CdS) bioconjugate in turn. The bioconjugate served as a signal amplification factor, and greatly enhanced the sensitivity of PSA detection. In this sensing strategy, the target PSA detection was based on the change in the amount of the signal amplification factor Ab2-CdS bioconjugate, which caused the change of photocurrent intensity. In the presence of PSA, the Ab2-CdS bioconjugate was specifically binding with PSA, then the signal amplification factor Ab2-CdS bioconjugate was incubated on the sensor electrode surface, increasing the photocurrent intensity significantly. Accordingly, under optimal conditions, a novel enhanced photoelectrochemical immunosensor was constructed, and it exhibited excellent sensitivity, selectivity and repeatability for detecting PSA. The detection limit was 1.3 fg·mL−1, and the range was 10 fg·mL−1 – 10 ng·mL−1. Simultaneously, the sensor also provides a likely sensing device for detecting other protein targets, which is of great significance for early clinical diagnosis.