Rabbit-Derived Monoclonal Antibody Based on Single B Cell Technology for Ultra-Sensitive and Specific Detection of Nicosulfuron in Soil and Agricultural Products

Nicosulfuron, a sulfonylurea herbicide, is primarily used to control annual weeds in corn fields in China. Residues of nicosulfuron in soil can easily cause phytotoxicity in subsequent crops, such as wheat and cabbage. It has become urgent for growers to analyze nicosulfuron residue in soil and plan subsequent crops based on the results of this analysis. In this study, rabbit monoclonal antibodies with high sensitivity and specificity were prepared by using single B-cell technology based on the synthesized haptens from our previous study. Rapid analysis methods using enzyme-linked immunosorbent assay (ELISA) and lateral flow immunochromatography assay (LFIA) were established to detect nicosulfuron in soil and agricultural products with ultra-sensitivity. The linear detection range of ELISA was 0.09770–5.808 ng/mL, with a half-maximum inhibitory concentration (IC50) of 0.753 ng/mL. LFIA achieved semi-quantitative analysis with a detection limit of 1.25 ng/mL and a cut-off value of 5 ng/mL. Spike recovery and real samples analysis indicated that results obtained from the immunoassay and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) were consistent. Molecular docking simulations revealed that antibody 6D8 formed multiple hydrogen bonds (SER-433 and SER-466) and hydrophobic interactions with nicosulfuron through its complementarity-determining regions (CDRs), thus achieving high specificity and strong binding force. The two complementary immunoassays developed in this study are important for the rapid analysis of nicosulfuron in environmental samples, and for guiding the correct and rational use of this herbicide.