Sandwich-format electrochemiluminescence assays for tumor marker based on PAMAM dendrimer-l-cysteine-hollow gold nanosphere nanocomposites

• Polyamidoamine (PAMAM) dendrimer-l-cysteine-hollow gold nanospheres nanocomposite was prepared.
• An amplification strategy based on PAMAM-l-Cys-HGNPs as promoter for S2O2−8/O2 ECL system.
• A sandwich ECL immunosensor for CEA detection was developed.

In this work, a novel polyamidoamine (PAMAM) dendrimer-l-cysteine-hollow gold nanospheres nanocomposite was fabricated and used as the promoter for the peroxydisulfate/O2 ECL system to detect the concentration of the tumor marker carcinoembryonic antigen (CEA). Herein, the carboxyl-terminated PAMAM dendrimers were decorated with l-cysteine (l-Cys) by EDC/NHS coupling chemistry. Then, the hollow gold nanospheres (HGNPs) were employed as effective nano-carriers for the assembly of PAMAM-l-Cys via thiols-Au bonding, which was used for further loading of detection antibody (Ab2) to form the PAMAM-l-Cys-HGNPs-Ab2 bioconjugates. In the presence of target CEA, the sandwiched immuno-structure can be formed between the capture anti-CEA antibodies (Ab1), which self-assembled on deposited gold modified electrode, and the Ab2 on the PAMAM-l-Cys-HGNPs, thereby resulting in a proportional increase in ECL response, due to the significant enhancement of PAMAM-l-Cys-HGNPs toward peroxydisulfate/O2 ECL system. As a result, a sandwich ECL assay for CEA detection was developed with excellent sensitivity of a large concentration variation from 20 fg/mL to 1.0 ng/mL and a detection limit of 6.7 fg mL−1.