GO-SELEX strategy in aptamer-based competitive lateral flow assay for the high-sensitivity detection of omethoate.

Omethoate (OMT) is a highly effective organophosphorus insecticide that progressively accumulates in the food chain, posing serious risks to human health and ecosystem. Therefore, it is essential to establish a detection method for OMT that combines high sensitivity with strong specificity to support food safety and environmental monitoring. In this study, we used a non-immobilized targeting method based on graphene oxide-based systematic evolution of ligands by exponential enrichment (GO-SELEX) to screen aptamers (APTs) of OMT. After 12 rounds of screening, we successfully obtained APTs with high affinity and specificity. We further verified the binding characteristics of the candidate APTs through fluorescence competition assays, molecular docking simulations, and sequence truncation and optimization. APT-8-1 was identified as the optimal candidate sequence (Kd=22.79±1.13 nM). Using it as a recognition element, we developed a competitive lateral flow assay (LFA) for detection of OMT. Under the optimized conditions, the limit of detection (LOD) was 0.69 μg/L, the detection range was 5-1000 μg/L. For the determination of OMT in vegetable samples, recovery rates were 94.21%-109.70%. These results indicate that the proposed LFA provides a rapid, sensitive, and reliable means for monitoring OMT residues in vegetables, offering a practical tool for food safety surveillance.