Understanding the residues and degradation of organophosphorus pesticides (OPs) in crops has attracted increasing attention. Herein, we designed a sensitive fluorescence immunoassay (FIA) by employing nanobody-linked alkaline phosphatase (Nb-ALP) and gold nanoclusters anchored manganese dioxide (AuNCs-MnO₂) composite. In immunoassay protocol, Nb-ALP is used to competitively recognize the coating antigen and pesticide. After competitive immunoreaction, alkaline phosphatase catalyzes L-ascorbic acid-2-phosphate to produce ascorbic acid that can trigger the decomposition of the AuNCs-MnO₂ composite, regulating the fluorescence response. As a proof-of-concept, fenitrothion (FNT) is chosen as the target analyte. As a result, the developed FIA exhibits high detection sensitivity (IC₁₀ = 5.78 pg/mL), which is about 56-times higher than that of the conventional enzyme-linked immunosorbent assay. The developed FIA has been successfully applied for precisely monitoring the degradation of FNT in Chinese cabbage with excellent anti-interference ability and reproducibility, paving the way for the determination of pesticide residues in real food samples.

了解有机磷农药 (OP) 在作物中的残留和降解已引起越来越多的关注。在此，我们通过使用纳米抗体连接的碱性磷酸酶 (Nb-ALP) 和金纳米团簇锚定的二氧化锰 (AuNCs-MnO 2 ) 复合材料设计了一种灵敏的荧光免疫测定 (FIA ₎。在免疫测定方案中，Nb-ALP 用于竞争性识别涂层抗原和农药。_{竞争性免疫反应后，碱性磷酸酶催化L-抗坏血酸-2-磷酸生成抗坏血酸，抗坏血酸可触发AuNCs-MnO 2}复合物的分解，调节荧光响应。作为概念验证，选择杀螟松 (FNT) 作为目标分析物。因此，开发的 FIA 具有高检测灵敏度（IC₁₀ = 5.78 pg/mL)，比传统酶联免疫吸附试验高约 56 倍。所开发的FIA已成功应用于大白菜中FNT降解的精确监测，具有优异的抗干扰能力和重现性，为实际食品样品中农药残留的测定铺平了道路。