A novel sandwiched electrochemiluminescence immunosensor for the detection of carcinoembryonic antigen based on carbon quantum dots and signal amplification

- The nanocomposite of polydopamine and Ag nanoparticles (PDA-AgNPs) provided an effective matrix for the immobilization of primary antibody (Ab1).
- Carbon quantum dots (CQDs), the electrochemiluminescence material, were immobilized on the poly(ethylenimine) functionalized graphene oxide (PEI-GO) to link secondary antibody (Ab2).
- The ECL signals of CQDs were greatly amplified under the synergistic effect of AgNPs, polydopamine, AuNPs and PEI-GO.
- The proposed ECL immunosensor can be used for the detection of CEA in real human serum samples.

In this study, a novel sandwiched electrochemiluminescence (ECL) immunosensor for the detection of carcinoembryonic antigen (CEA) was developed. The nanocomposite of polydopamine and Ag nanoparticles (PDA-AgNPs) was prepared by the redox reaction between Ag+ and dopamine. This nanocomposite not only provided an effective matrix for the immobilization of primary antibody (Ab1) but also enhanced the conductivity of the electrode. Carbon quantum dots (CQDs) were immobilized on the poly(ethylenimine) functionalized graphene oxide (PEI-GO) through amido-bond. Then Au nanoparticles were decorated on the CQDs modified PEI-GO matrix, and the resulted complex AuNPs/CQDs-PEI-GO was introduced to link secondary antibody (Ab2). The CQDs can be connected to the electrode surface through the combination of CEA with Ab1 and Ab2, and then the amplified electrochemiluminescence signal of CQDs was obtained with the synergistic effect of AgNPs, polydopamine, AuNPs and PEI-GO. Under the optimal conditions, the ECL intensity was proportional to the logarithm value of CEA concentration in the linear range from 5 pg mL−1 to 500 ng mL−1 with a detection limit of 1.67 pg mL−1 for CEA detection. The immunosensor was applied for the CEA detection in real samples with satisfactory results. The proposed ECL immunosensor showed good performance with high sensitivity, specificity, reproducibility, stability and will be potential in clinical detection.