Magnetic assisted fluorescence immunoassay for sensitive chloramphenicol detection using carbon dots@CaCO3 nanocomposites.

• Carbon dots-encapsulated calcium carbonate nanospheres are facilely synthesized. • Hapten-labeled MNPs are prepared and used as the nano-carrier for the immunoassay. • Fluorescent immunoassay takes a short assay time and has satisfactory performance. Analytical methods with high sensitivities and short assay times are urgently required for the screening of "zero tolerance" hazardous substances in food. Herein, we propose a fluorescent immunoassay for the highly sensitive and rapid analysis of chloramphenicol (CAP) based on carbon dots (CDs)-encapsulated CaCO 3 nanospheres and magnetic nanoparticles (MNPs). The fluorescent immunoprobes were prepared by coupling the anti-CAP antibodies to carboxymethyl cellulose-functional CDs@CaCO 3 nanospheres. Chitosan-modified MNPs with "core–shell" structures were prepared and then conjugated to the CAP hapten, acting as the nano-carrier and interface for the immunoreaction. With the assistance of MNPs, the established fluorescent immunoassay achieved the sensitive detection of CAP in chicken with a limit of detection of 0.03 μg kg−1 and recoveries ranging from 83.7%–105.0%. The analysis results of the fluorescent immunoassay were evaluated by the enzyme-linked immunosorbent assay, having a correlation coefficient of 0.981. Our work provides a rapid, facile, and reliable strategy for the highly sensitive analysis of food contaminants based on "green" fluorescent nanoprobes. [ABSTRACT FROM AUTHOR]