An ultrasensitive quenched electrochemiluminescent immunoassay based on the peroxidase-like activity of ZnFe2O4@Au nanoparticles

We reported here the synthesis of zinc ferrite (ZnFe2O4), which was further fabricated into gold nanoparticles (AuNPs) functionalized ZnFe2O4 (ZnFe2O4@Au) through a layer-by-layer (LBL) self-assembly method. The prepared ZnFe2O4@Au showed excellent catalytic performance to the reduction reaction procedure of hydrogen peroxide (H2O2), and the coated AuNPs provided the nanoparticles with good biocompatibility. In addition, the CdTe quantum dots dotted graphene (G–CdTe) was prepared and was found with good electrochemiluminescence (ECL) property. The prepared ZnFe2O4@Au and G–CdTe were applied in a simple sandwich-type ECL immunosensor for carcinoembryonic antigen (CEA). In the immunosensor, G–CdTe acted as the solid support for CEA primary antibody and ZnFe2O4@Au was employed as the supporter of CEA secondary antibody. The ZnFe2O4@Au could quench the ECL signal of the G–CdTe and the quenching ECL intensity could be obtained. The proposed immunosensor enabled CEA concentrations to be determined in the 0.01–50 ng mL−1 concentration range, with a detection limit of 4 pg mL−1.