Ultrasensitive electrochemiluminescence immunosensor based on nanoporous gold electrode and Ru-AuNPs/graphene as signal labels

In the paper, a simple and sensitive sandwich-type electrochemiluminescence (ECL) immunosensor was proposed for the detection of cancer antigen 125 (CA 125) on a nanoporous gold (NPG) modified glassy carbon electrode (GCE). The NPG was easily prepared by a selective dissolution of silver from silver/gold alloy in nitric acid. The fabrication of Ru(bpy)32+-gold nanoparticles (Ru-AuNPs) aggregates was owing to the electrostatic interactions between citrate-capped AuNPs and Ru in aqueous medium. The Ru-AuNPs composite assembled with poly(diallyldimethylammonium chloride) functionalized graphene nanosheets (GR) (Ru-AuNPs/GR) was used as ECL labels, which has large surface area, good biocompatibility and electronic conductivity. The ECL intensity observed by the application of as-prepared Ru-AuNPs/GR composites was enhanced 6-fold compared to those of Ru-AuNPs. The primary antibody of CA 125 (Ab1) was first immobilized on the NPG modified electrode, then the antigen and the secondary antibody (Ab2) were conjugated to form a sandwich-type immunocomplex through the specific interaction. The proposed ECL immunosensor provided a wide linear response range over 0.01–100 U mL−1 with a detection limit of 0.005 U mL−1. The ECL immunosensor showed high sensitivity, good reproducibility, satisfied regeneration and selectivity, and may exhibit an attractive approach for other analyte determination.