A magnetic nanoparticle based immunoassay for alternariol monomethyl ether using hydrogen peroxide-mediated fluorescence quenching of CdTe quantum dots

The authors describe a fluorometric immunoassay for alternariol monomethyl ether (AME). It is making use of magnetic nanoparticles and quenching of the fluorescence of mercaptopropionic acid-capped CdTe quantum dots (MPA-CdTe QDs) by H 2 O 2 . Catalase (CAT) was labeled with AME as a competitive antigen to competitively bind to magnetic nanoparticles carrying monoclonal antibodies (mAbs) with free AME in samples. The effects of the concentration and pH value of buffer, the concentrations of H 2 O 2 and CAT-AME, and the incubation time of H 2 O 2 and MPA-CdTe QDs were optimized. Under optimal conditions and in combination with magnetic separation, the quenching of the fluorescence of the MPA-CdTe QDs (excitation at 310 nm, emission at 599 nm) can be used to quantify AME with a detection limit of 0.25 pg·mL −1 and the linear range from 0.25 to 7.5 pg·mL −1 . The immunoassay also has a lower cross-reactivity to AME analogues. It was evaluated by analyzing fruit samples spiked with AME. The recoveries from spiked fruits ranged from 87.2% to 92.0%. Graphical abstract Schematic presentation of a fluorometric immunoassay for alternariol monomethyl ether (AME) using magnetic nanoparticles (MNPs) for the rapid separation and purification. The method is based on quenching of the fluorescence of mercaptopropionic acid-capped CdTe quantum dots (MPA-CdTe QDs) by H 2 O 2 for the fluorescence signal output, and on the use of catalase (CAT) with its high catalytic activity.