AChE and CoFe NPs-initiated cascade amplification for sensitive detection of organophosphorus pesticides.

Traditional methods for pesticide residue detection often rely on expensive instruments, are time-consuming, and lack cost efficiency. This investigation developed a fluorescence-based assay that utilizes cascade amplification through cholinesterase hydrolysis and thiamine (TH) oxidation for the detection of organophosphorus pesticides (OPs). A Prussian blue analog (CoFe NPs) with high catalytic activity for TH oxidation was synthesized. Cholinesterase hydrolyzes acetylthiocholine to produce thiocholine, which subsequently inhibits the CoFe NPs-catalyzed oxidation of TH. In the presence of paraoxon, acetylcholinesterase activity is inhibited, leading to restored TH oxidation and generating a strong fluorescence signal. The increase in fluorescence intensity is proportional to paraoxon concentration. This novel assay demonstrates a linear detection range of 0-10 ng/mL, achieving a limit of detection (LOD) of 0.5 ng/mL, indicating sensitivity superior to that reported in previous studies. This work presents a sensitive and innovative strategy for OPs detection.