ArticleChemistryDouble signal amplification sandwich-structured immunosensor based on TiO2 nanoparticles enhanced CdSe@ZnS QDs electrochemiluminescence and the dramatic quenching effect of Au@polydopamine nanoparticles

In this work, a double signal amplified immunosensor based on the enhanced CdSe@ZnS quantum dots (QDs) electrochemiluminescence (ECL) via TiO2 nanoparticles (TiO2 NPs) and the outstanding quencher of polydopamine (PDA) decorated Au nanoparticles (Au@PDA NPs) for ultrasensitive detection of carcinoembryonic antigen (CEA) has been successfully achieved. The ECL of CdSe@ZnS QDs with different sizes has been investigated carefully, especially cooperation with TiO2 NPs. Au@PDA NPs have been synthesized and characterized by transmission electron microscopy (TEM) and UV-Vis spectrum, which acted as ECL quenchers to label the secondary antibody (Ab2) of CEA to form Ab2/Au@PDA NPs conjugates. The sandwich-structured immunosensor was formed between capture antibody (Ab1) on CdSe@ZnS QDs/TiO2 NPs/glassy carbon electrode, CEA and Ab2/Au@PDA NPs conjugates, resulting in a proportional ECL quenching signal relevant to the CEA concentration. Thus, CEA as a model biomarker has been detected in the linear range from 0.001 to 100 ng mL−1 with a limit of detection of 0.35 pg mL−1 (S/N = 3).