ORIGINAL PAPER Potential-resolved electrochemiluminescence immunoassay for simultaneous determination of CEA and AFP tumor markers using dendritic nanoclusters and Fe 3 O 4 @SiO 2 nanoparticles Bahareh Babamiri 1 & Rahman Hallaj 1,2 & Abdollah Salimi 1,2 & Keivan Akhtari 3 Received: 7 March 2017 /Accepted: 14 June 2017 # Springer-Verlag GmbH Austria 2017 Abstract A potential-resolved electrochemiluminescence (ECL) immunoassay is presented for the simultaneous deter- mination 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 Fe 3 O 4 -SiO 2 as a magnetic bead. The QDs of type CdTe@CdS and luminol in the presence of H 2 O 2 generate ECL at an applied voltage of -1.12 V and +0.6 V (vs Ag/AgCl), respectively. The sensitiv- ity 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 detec- tion 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 agree- ment with the those obtained with an ELISA. Keywords Electrochemiluminescence . Simultaneous determination . Alpha-fetoproteinantigen . Carcinoembryonic antigen . CdTe@CdS quantum dots . Luminol . Hydrogen peroxide . Dendrimer . Magnetic nanoparticles Introduction Credible detection of tumor markers continues to be an important issue for the prediction and diagnosis of cancer. Since most cancers have more than one marker associated, a single marker immunoassay often is not sufficient for specific cancer diagnosis [1, 2]. For example, the presence of the carcinoembryonic antigen (CEA) is associated with colorectal cancer, pancreatic cancer and liver cancer, while alpha- fetoprotein (AFP) is associated with epithelial ovarian tumors and liver cancer. Thus, the development of simultaneous multi- analyte immunoassay with high sensitivity and specificity has a great significance in the clinical diagnosis. Multiplexed im- munoassay (MIA) as an effective analytical method provided a high sensitivity in the timely screening of cancers and led to reduce analytical time, detection cost and false results com- pared to single-analyte assays. [3, 4] Analytical methods such as fluorescence, [5] electrochemistry, [6, 7] chemilumines- cence [8] and electrochemiluminescence [9] have been report- ed for the simultaneous determination of tumor markers. Among the different immunological techniques for the simul- taneous tumor markers analysis, the electrochemiluminescent (ECL) immunoassay shows high sensitivity, fast detection, low background, wide dynamic detection range, simple controlla- bility and cost-effectiveness [10–12]. So, as a powerful analyt- ical technique, ECL is one of the most important tools for multiplexed immunoassay. It is known that the multiplexed immunoassay needs different labels with specific signal for each target. Accordingly, ECL multiplexed immunoassay Electronic supplementary material The online version of this article (doi:10.1007/s00604-017-2386-x) contains supplementary material, which is available to authorized users. * Rahman Hallaj Rhallaj@uok.ac.ir; Rhallaj@yahoo.com * Abdollah Salimi absalimi@uok.ac.ir; absalimi@yahoo.com 1 Department of Chemistry, University of Kurdistan, Sanandaj 66177-15175, Iran 2 Research Center for Nanotechnology, University of Kurdistan, Sanandaj 66177-15175, Iran 3 Department of Physics, University of Kurdistan, P.O. Box 416, Sanandaj, Iran Microchim Acta DOI 10.1007/s00604-017-2386-x