Double-enzymes-mediated fluorescent assay for sensitive determination of organophosphorus pesticides based on the quenching of upconversion nanoparticles by Fe3+

Herein, a new double-enzymes-modulated fluorescent assay based on the quenching of upconversion nanoparticles (UCNPs) by Fe3+ was constructed for sensitive determination of OPs. OPs can inhibit the activity of acetylcholinesterase to reduce the production of choline and further lead to the lack of H2O2 in the presence of choline oxidase. Therefore, Fe2+ cannot be converted into Fe3+, resulting in turn-on fluorescence of UCNPs. Under optimal conditions, an excellent linear correlation between the inhibition efficiency and the logarithm of the chlorpyrifos concentration was achieved with a detection limit (LOD) of 6.7 ng/mL in the range of 20-2000 ng/mL. The recovery for chlorpyrifos in apples and cucumbers was 89.5-97.1%. The results were consistent with those obtained by GC-MS. Overall, the integration of UCNPs into the double-enzymes-mediated Fe3+/Fe2+ conversion endows this method with desirable rapidity, sensitivity, selectivity, stability, operational simplicity, and strong anti-interference capability, holding great potential in the application of food safety.

Automated summary

A new double-enzymes-modulated fluorescent assay based on the quenching of upconversion nanoparticles by Fe3+ was developed for sensitive determination of organophosphorus pesticides. The method showed rapidity, sensitivity, selectivity, stability, ease of operation, and strong anti-interference capability, making it promising for applications in food safety.