Potential-resolved electrochemiluminescence immunoassay for simultaneous determination of CEA and AFP tumor markers using dendritic nanoclusters and Fe₃O₄@SiO₂ nanoparticles

A potential-resolved electrochemiluminescence (ECL) immunoassay is presented for the simultaneous determination of the tumor markers alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA). It is making use of polyamidoamine dendrimer - quantum dots (PAMAM–QDs) and PAMAM-luminol as the signal probes and Fe₃O₄-SiO₂ as a magnetic bead. The QDs of type CdTe@CdS and luminol in the presence of H₂O₂ generate ECL at an applied voltage of −1.12 V and +0.6 V (vs Ag/AgCl), respectively. The sensitivity of the method can be enhanced by using PAMAM dendrimers as a carrier for immobilizing the QDs. The assay is performed in a sandwich format, and AFP and CEA can be quantified via potential cycling from +0.6 to −1.4 V. Both tumor markers can be detected by this method in the 0.25 fg.mL⁻¹ to 20 pg.mL⁻¹ concentration range with a detection limit as low as 0.10 fg.mL⁻¹. The assay was applied to the determination of both AFP and CEA in (spiked) human serum samples, and the results were found to be in acceptable agreement with the those obtained with an ELISA. .