From Hapten Design to Mechanism Exploration: Developing a High-Specificity Immunochromatography Strip for Fluridone Detection

Fluridone (FLU), a commonly used aquatic herbicide in water environmental management, poses threats to aquatic ecosystems and aquatic product safety due to issues of misuse, abuse, and residues. Therefore, it is necessary to develop highly sensitive detection methods. Here, two novel FLU haptens with distinct spacer arms were rationally designed, and the best scheme was selected through computer-aided chemical simulations. Through mouse immunization and cell fusion techniques, a high-affinity, specific antibody against FLU (mAb-2B2) was obtained. The affinity constant (<i>K</i>_a) and maximal half-inhibitory concentration (IC₅₀) of mAb-2B2 were 3.72 × 10⁹ L/mol and 0.50 ng/mL, respectively, with negligible cross-reactivity to six other analogues. Molecular docking analysis revealed that the key amino acid residues mediating the specific recognition of mAb-2B2 were primarily ARG 99 (at distances of 2.47, 3.88, and 2.80 Å), ARG 96 (at 3.56 Å), ARG 100 (at 5.32 Å), and TYR 91 (at 3.79 Å). Based on mAb-2B2, a gold nanoparticles-immunochromatographic strips (GNPs-ICS) method for detecting FLU residues in river water, crayfish, and fish samples was established for the first time, with detection ranges of 4.22-31.55 ng/mL, 13.61-65.01 μg/kg, and 5.51-35.40 μg/kg, respectively. This method was demonstrated to be suitable for rapid primary screening of FLU residues in environmental and aquatic products.