Immunoassay for carcinoembryonic antigen based on the Zn 2+ -enhanced fluorescence of magnetic-fluorescent nanocomposites

Carbon coated magnetic composite nanoparticles (Fe3O4@C) were prepared and further fabricated into a new kind of the multifunctional core/shell nanoparticles (Fe3O4@C@CdTe) by a self-assembly of CdTe quantum dots. These nanoparticles exhibited good fluorescence (FL) property. In addition, zinc oxide (ZnO) nanowires (NWs) with high surface area were synthesized via solvothermal reaction under a hydrothermal condition. In a sandwich immune-device for the detection of carcinoembryonic antigen (CEA), the Fe3O4@C@CdTe nanoparticles were applied as the solid support for CEA-primary monoclonal antibody (CEA-McAb1) and the ZnO NWs were applied as the label of CEA-secondary monoclonal antibody (CEA-McAb2). The Fe3O4@C@CdTe-McAb1 was collected at the bottom of the quartz cuvette using a magnet. The ZnO NWs bond with Fe3O4@C@CdTe after the immune reaction. The Zn2+ ions are subsequently released from ZnO NWs by dissolution in acidic buffer solution and the enhanced FL intensity is measured. In this way, the proposed FL immune-device displayed excellent analytical performance for the detection of CEA in the range of 0.005–100ngmL−1 with a low detection limit of 1.6pgmL−1, and the assay results of CEA in real serum samples were in a good agreement with the standard enzyme-linked immunosorbent assay (ELISA) tests.