Sandwich-structured electrogenerated chemiluminescence immunosensor based on dual-stabilizers-capped CdTe quantum dots as signal probes and Fe3O4-Au nanocomposites as magnetic separable carriers

Abstract

In this work, a promising electrochemiluminescence (ECL) immunosensor, based on dual-stabilizers-capped CdTe quantum dots (QDs) as signal labels and Fe3O4-Au nanocomposites as nanocarriers, was fabricated for the first time. Magnetic Fe3O4-Au nanocomposites served as effective supporters for the primary antibodies (Ab1), due to the high surface area to volume ratio, the ease of bioconjugation, and the convenience of magnetic separation. Au nanoparticles (NPs) on the Fe3O4 surface could not only immobilize Ab1 via coordination and electrostatic interactions, but also supply the good electroconductivity to the immunosensor. The dual-stabilizers-capped CdTe QDs with completely passivated surface exhibited excellent ECL response and stability in the presence of peroxydisulfate (S2O8−), and thus were used as signal labels for the conjugation with secondary antibodies (Ab2). The CdTe QDs-labeled Ab2 was characterized by agarose gel electrophoresis. Successful fabrication of the immunosensor has been proved by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The developed immunosensor showed a wide linear range from 0.005ngmL−1 to 80ngmL−1 for the detection of carcinoembryonic antigen (CEA, as a model). And the detection limitation was 1pgmL−1 (S/N=3). Furthermore, the application of the immunosensor in serum sample verified its accuracy and reliability, indicating that it may open a new avenue for clinical bioassay.