A sandwich-type electrochemical immunosensor for ultrasensitive detection of CEA based on core–shell Cu2O@Cu-MOF@Au NPs nanostructure attached with HRP for triple signal amplification

A novel sandwich-type electrochemical immunosensor based on cuprous oxide (Cu2O)@copper-metal organic framework (Cu-MOF)@gold nanoparticles (Au NPs) core–shell structure was proposed. Cu2O@Cu-MOF@Au attached with horseradish peroxidase (HRP) triple-catalyzed hydrogen peroxide (H2O2) for detecting CEA antigen. In this work, 50 nm Cu2O nanospheres were prepared. Using Cu2O nanospheres as the core, Cu-MOF was coated on the surface of Cu2O nanospheres by reaction of Cu2O and ligands. Subsequently, chloroauric acid was reduced to Au NPs without adding any reducing agent and Au NPs dispersed on the surface of Cu-MOF. Finally, the Cu2O@Cu-MOF@Au-HRP-Ab2 nanoprobe was successfully prepared. Immunosensors had good performance due to the following reasons. Firstly, Cu2O, Cu-MOF and HRP have excellent catalytic properties for hydrogen peroxide. In addition, the synergistic effect of Cu2O, Cu-MOF and HRP promoted the reduction of hydrogen peroxide and tripled amplification of electrical signals. Here, the successfully prepared immunosensor detected carcinoembryonic antigen (CEA) sensitively, the detection range was 50 fg/mL–80 ng/mL, and the detection limit was 17 fg/mL. Besides, the proposed immunosensor had good stability, selectivity and specificity. Detection in human serum samples had good results without matrix effect. This provided a new idea for the clinical detection of tumor markers: "metal oxide—metal organic framework—precious metal nanoparticles" (MMP).