Ultrasensitive detection of carcinoembryonic antigen based on electrochemiluminescence quenching of Ru(bpy)32+ by quantum dots

An ultrasensitive electrochemiluminescence (ECL) immunosensor for the detection of carcinoembryonic antigen (CEA) in serum and saliva was developed. Ru(bpy)32+-graphene-Nafion composite was first coated on the glassy carbon electrode surface in this ECL immunosensor. The sandwich-type immunoreactions between the first antibody and the second antibody bridged the donors Ru(bpy)32+ and acceptors QDs, which led to the occurrence of ECL quenching of Ru(bpy)32+ by QDs. Based on the efficient ECL quenching, ultrasensitive CEA detection was realized. Under optimal conditions, the ECL signal depended linearly on the logarithm of the CEA concentration within a range from 0.005 to 0.5 pg/mL, and the detection limit of CEA was 0.002 pg/mL. Moreover, the proposed ECL immunosensor provides a stable, specific, and highly sensitive immunoassay protocol for CEA detection at very low levels, which might hold a promise for clinical application.