Fabricating an Acetylcholinesterase Modulated UCNPs-Cu²⁺ Fluorescence Biosensor for Ultrasensitive Detection of Organophosphorus Pesticides-Diazinon in Food

In this study, a highly sensitive upconversion fluorescence (FL) biosensor was developed for the detection of organophosphorus pesticides (OPs) based on an acetylcholinesterase (AChE) modulated FL “off–on–off” strategy. The luminescence of synthesized UCNPs could be quenched strongly by Cu²⁺ due to an energy transfer effect. Upon addition of AChE and acetylthiocholine (ATCh), the enzymatic hydrolysate (thiocholine) could seize Cu²⁺ from UCNPs-Cu²⁺ mixture, resulting in the quenched FL triggered on. OPs could irreversibly impede the activity of AChE, which caused the formation of thiocholine to decrease, thus, reduced the recovery of FL. Under the optimum conditions, a linear detection range from 0.1 to 50 ng/mL was achieved for the representative OPs (diazinon) with LOD of 0.05 ng/mL. Furthermore, the ability of the biosensor to detect OPs was also confirmed in adulterated environmental and agricultural samples. In validation analysis, the proposed sensor showed satisfactory results (p > 0.05) with GC–MS.