Ultrasensitive amperometric immunoassay for carcinoembryonic antigens by using a glassy carbon electrode coated with a polydopamine-Pb(II) redox system and a chitosan-gold nanocomposite

The authors describe an immunoassay for the determination of carcinoembryonic antigen (CEA) tumor markers by depositing a polydopamine-Pb(II) nanocomposite on the surface of a glassy carbon electrode. The nanocomposite acts as a redox system that displays a large specific surface and provides a strong current signal at ?0.464 V (vs. Ag/AgCl). After the deposition of PDA-Pb²⁺ on glassy carbon electrode, the electrode was additionally coated with a chitosan-gold nanocomposite. The immunoassay platform was obtained by immobilization of antibodies against carcinoembryonic antigens by using glutaraldehyde and blocking with bovine albumin. Owing to its large surface, good electrical conductivity and powerful current response, the immunoassay has a wide linear range that extends from 1 fg·mL^?1 to 100 ng·mL^?1, with a detection limit as low as 0.26 fg·mL^?1. The results obtained with this immunoassay when determining CEAs in human serum were found to be consistent with those obtained by ELISAs.

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Graphical abstract Schematic of an ultrasensitive electrochemical immunosensor for the carcinoembryonic antigen. It is based on a glassy carbon electrode modified with a polydopamine-Pb(II) nanocomposite acting as a signal-inherent substrate.