An enhanced gold immunochromatographic assay ( GICA ) with simplicity, rapidity and high sensitivity was developed to detect imidaclothiz by using the high affinity between biotin and streptavidin. The 13-nm AuNPs were double-labeled with anti-imidaclothiz antibody and biotinylated DNA, and the 41-nm AuNPs were labeled with streptavidin to prepare an enhanced gold immunochromatographic test strip for imidaclothiz. The working conditions of the strip were systematically optimized, and the sensitivity, specificity, precision and accuracy were assessed by testing the cross-reactivity ( CR) , spiked recovery and validation with high performance liquid chromatography ( HPLC) . Under the optimal conditions, the detection could be completed in 10 min with visual result, and the limit of detection ( LOD ) was 25 ng/mL. The analysis showed no cross-reactivity with analogues of imidaclothiz except for imidacloprid. The detection results of GICA agreed with the spiked concentrations of imidaclothiz at spiked levels of 0 . 05 , 0 . 5 and 5 μg/g in river water, rice, cucumber, tomato, pear, cabbage and apple samples. The detection results of GICA for imidaclothiz in unknown concentration river water and pear samples were consistent with that of HPLC.

To produce high-affinity monoclonal antibodies against pesticide imidacloprid, we synthesized the haptens 1-[(6-Carboxylethylthio-3-pyridinyl) methyl] -N-nitro-imidazolidinimine (named as H1) and 1-[(6-Chloro-3-pyridinyl) methyl]-3-carboxylpropyl-N-nitro-2-imidazolidinimine (termed as H2). And then the haptens were coupled to bovine serum albumin (BSA) and ovalbumin (OVA) for immunogen (H1-BSA) and coating antigen (H2-OVA) respectively by NHS ester method. BALB/c mice were immunized with H1-BSA conjugate. We obtained two hybridoma cell lines 2F11/A9 and 2G6/G12 secreting antibody specific for imidacloprid from the conventional hybridoma technology. The result showed that the subtypes of obtained monoclonal antibodies were IgG3 and IgG1, respectively, and the titers of ascites were up to 1:128 000. The indirect competitive ELISA indicated the IC50 values of 5.3 and 28.3 ng/mL with detection limits of 1.1 ng/mL and 7.7 ng/mL, respectively. Two monoclonal antibodies had no apparent cross reactivity with six analogous compounds. Thus, two prepared monoclonal antibodies had a very high affinity and specificity, and it could be used to develop ELISA for rapid determination of imidacloprid residue and laid a solid foundation for research and development of products for immunoassay.
Animals ; Antibodies, Monoclonal ; biosynthesis ; Antibody Specificity ; Hybridomas ; metabolism ; Imidazoles ; immunology ; Insecticides ; immunology ; Mice ; Mice, Inbred BALB C ; Neonicotinoids ; Nitro Compounds ; immunology