Electrochemical biosensor based on composite of gold nanoparticle/reduced-graphene oxide/graphitic carbon nitride and a caprolactone polymer for highly sensitive detection of CEA.

Carcinoembryonic antigen (CEA) is a broad-spectrum biomarker, and its accurate detection and analysis is important for early clinical diagnosis and treatment. This study aimed to develop a highly sensitive and selective sandwich-type immunosensor based on electrochemical impedance spectroscopy (EIS) for the accurate detection of CEA. A novel composite material, gold nanoparticle/reduced-graphene oxide/graphitic carbon nitride (AuNPs/rGO/g-CN), was synthesized with excellent electrical conductivity and a large specific surface area to immobilize biological probes. And ab1-CEA-ab2 formed a sandwich structure of 'antibody-antigen-antibody', which ensured the high selectivity of the biosensor. Furthermore, the introduction of caprolactone polymer (DMPA-PCL) significantly amplifies the impedance signal and improves the sensitivity of the analytical method. Scanning electron microscopy, x-ray diffraction, transmission electron microscopy Fourier transform infrared spectroscopy, and ultraviolet-visible spectrophotometry were used to characterise the prepared AuNPs/rGO/g-CN and DMPA-PCL. Under the optimal conditions, the sensor showed good analytical performance for the detection of CEA with a linear range of 100 fg mL-100 ng mL and a detection limit of 83.2 fg mL. And the sandwich-type immunosensor showed good selectivity and stability for the recognition of CEA in real samples.