AbstractThe authors describe a fluorometric "off-on-off" method for the determination of the activity of acetylcholine esterase (AChE). Molybdenum oxide quantum dots (QDs) are used as a fluorescent probe having excitation/emission peaks at 405/525 nm. It is found that the photoluminescence of such QDs is quenched by Cu(II) ion but that it can be restored by acetylcholine which is formed by AChE-catalyzed hydrolysis of acetylthiocholine. The effect is due to the strong affinity between Cu(II) and the thiol group of acetylthiocholine. Hence, quenching is increasingly reversed with increasing concentrations of AChE. However, fluorescence is not restored if the activity of AChE is inhibited by an inhibitor. Under optimal conditions, a linear relationship is founded in the 0.05 to 15 mU·mL−1 AChE activity range, with a limit of detection of 35 μU·mL−1 (applying the 3σ/k criterion). Three organophosphate pesticides and propazine were used to validate the assay. All showed strong inhibition, with IC50 values (the concentration required for 50% inhibition to occur) to be 52, 221, 48 and 9 nM for diazinon, chlorpyriphos, monocrotophos and propazine. Benefitting from its sensitivity, specificity and simplicity, the assay in our perception provides a valuable tool for detection of AChE activity and in screening for its inhibitors. Graphical abstractA novel “off-on-off” assay is constructed for acetylcholine esterase (AChE) activity and inhibitor screening benefitting from the phenomenon that the photoluminescence of molybdenum oxide quantum dots (MoOx QDs) is quenched by Cu2+ and that the quenched photoluminescence can be restored due the strong affinity between Cu2+ and thiocholine (Tch) which is the hydrolysis product formed due to catalysis by AChE.

中文翻译：

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使用 MoOx 量子点作为光致发光探针检测乙酰胆碱酯酶及其抑制剂的活性

摘要作者描述了一种用于测定乙酰胆碱酯酶 (AChE) 活性的荧光“断断续续”方法。氧化钼量子点 (QD) 用作荧光探针，在 405/525 nm 处具有激发/发射峰。发现这种量子点的光致发光被 Cu(II) 离子淬灭，但它可以被乙酰胆碱恢复，乙酰胆碱是由乙酰胆碱催化水解形成的。该效应是由于 Cu(II) 与乙酰硫代胆碱的硫醇基团之间的强亲和力。因此，猝灭随着 AChE 浓度的增加而逐渐逆转。然而，如果 AChE 的活性被抑制剂抑制，则荧光不会恢复。在最佳条件下，在 0.05 至 15 mU·mL−1 AChE 活性范围内建立线性关系，检测限为 35 μU·mL−1（应用 3σ/k 标准）。三种有机磷农药和丙嗪用于验证该测定。所有都显示出强抑制作用，二嗪农、毒死蜱、久效磷和丙嗪的 IC50 值（发生 50% 抑制所需的浓度）分别为 52、221、48 和 9 nM。受益于其灵敏度、特异性和简单性，我们认为该测定为检测 AChE 活性和筛选其抑制剂提供了有价值的工具。