The luminol-H 2 O 2 system is widely applied in electrochemiluminescence (ECL) assays but has limited stability. We are presenting an alternative immunosensing strategy by making use of Au@Ag nanorods that mimic the enzyme peroxidase. It also makes use of the supercapacitive supporter NH 4 CoPO 4 as a supporter substrate that facilitates ion movement due to its many nanogaps between the assembled nanoplates. It also plays a vital role for stabilizing the ECL signal of luminol. The immunosensor was constructed by first placing a chitosan film containing NH 4 CoPO 4 , Au@Ag and luminol on a glassy carbon electrode (GCE), and the immobilizing anti-CEA on its surface. ECL is generated via electrochemical reaction of luminol on the surface of the Au@Ag-luminol film in the presence of H 2 O 2 . The assay was evaluated with respect to effects of pH value, time and temperature of incubation, specificity, reproducibility, and stability in a lab setting. A linear relationship between ECL intensity and CEA concentration is found for the 0.1 pg·mL −1 to 380 ng·mL −1 range, and the lower detection limit is as low as 30 fg·mL −1 . In our perception, this immunoassay has a large scope in that numerous other immunoassays will become feasible by using other antibodies and, possibly, aptamers.

The common drawbacks of most traditional electrochemiluminescence (ECL) immunoassays are the strict storage conditions for the ECL electrode and the steric hindrance caused by bovine serum albumin and antigen. The strict storage conditions require that the modified electrode must be stored at 4 °C before measurement, which may cause the degradation of protein molecules and low reproducibility as the time goes by. The steric hindrance can hinder electron transfer between the electrode and the electrochemical active substance unable to transmit proteins on the electrode surface. The current study takes a 96-well microtiter plate (MTP) as a bridge for analyte pre-treatment and Au@Pd nanorods as a peroxidase mimic to assemble a simple and robust ECL immunoassay. Advantages of such assay include not only high sensitivity but also robust detection circumstance. We demonstrated the method by detecting carcinoembryonic antigen from human serum and obtained a good detection limit of 3 fg mL(-1).

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