An enzyme-linked chemiluminescent immunoassay developed for detection of Butocarboxim from agricultural products based on monoclonal antibody

Highly selective monoclonal antibody-based fluorescence immunochromatographic assay for the detection of fenpropathrin in vegetable and fruit samples

Fenpropathrin (FPT) is a typical pyrethroid pesticide that can cause chronic toxicity to humans. Herein, an anti-FPT monoclonal antibody (mAb) was elicited via a novel hapten synthesized by introducing a carboxyl-containing spacer arm in the cyclopropane moiety of FPT. Characterized by enzyme-linked immunosorbent assay (ELISA), the mAb exhibited high affinity and selectivity to FPT with a half-maximal inhibitory concentration of 31.05 μg/L and negligible cross-reactivities with analogs of pyrethroids. Based on the mAb, a fluorescence immunochromatographic assay (FICA) for FPT detection was firstly developed. The detection limit of the FICA is 0.012 mg/kg which is much lower than the maximum residue limit of FPT for food samples. The average recoveries of FPT from spiked food samples by the FICA were 85.0-105.0%, and the obtained results were in good agreement with those of gas chromatography-tandem mass spectrometry. Overall, this work provided a reliable tool suitable for the detection of FPT residue for large-scale samples in a rapid and cost-effective manner.

Ultrasensitive antibody production strategy based on hapten property for simultaneous immunoassay

A high-quality antibody production strategy is significant for immunoassay. In this work, four general haptens were proposed based on the 3D structure and surface electrostatic potential of molecular modeling. It was found that the sensitivity and specificity of polyclonal antibodies (pAbs) mainly depended on the bond angle of shapes liked "V" between haptens and proteins and hydrophobic parts of haptens. The quantified process was employed to obtain pAbs against cyhalofop-butyl and its metabolites (CAFs), with the IC₅₀ value of 4.9 μg·L^-1 under optimal conditions. The limit of quantization (LOQ) of the ultrasensitive icELISA in brown rice was 2 μg·kg^-1. The recoveries were 74%-110%, with a coefficient of variation (CV) less than 10%. This study indicated that the hapten property approach led to an improved immunoassay.

Development of enzyme linked immunosorbent assay and lateral flow immunoassay for the rapid detection of dapsone in milk

High-throughput rapid detection of dapsone in milk without pretreatment.

Ag@WS2 quantum dots for Surface Enhanced Raman Spectroscopy: Enhanced charge transfer induced highly sensitive detection of thiram from honey and beverages

Novel SERS substrates is urgently in demand for rapid and sensitive analysis of toxic agrochemicals from food. In this work, a monodispersed tungsten disulfide quantum dots modified silver nanosphere (Ag@WS₂QD) was prepared and used as SERS substrate. Ag@WS₂QD generated uniform and stable SERS signals within 2 min, displaying great promise in "mixing and reading" detection. Compared to unmodified colloidal silver nanoparticles, 4 times higher analytical enhancement factor was found in Ag@WS₂QD. Density functional theory calculation verified the enhanced charge transfer within the coupling systems of molecule-Ag@WS₂QD. Besides, the unique surface properties are beneficial for the enrichment of specific molecule. Both the chemical extraction and enhanced charge transfer contributes to rapid and sensitive SERS detection of Ag@WS₂QD. A "mixing and reading" SERS method for thiram from honey and four kinds of juice was developed from Ag@WS₂QD, showing great promise for rapid and direct SERS detection for toxic agrochemicals and further applications.

Quantitative Determination of Acetamiprid in Pollen Based on a Sensitive Enzyme-Linked Immunosorbent Assay

A sensitive biotinylated indirect competitive enzyme-linked immunosorbent assay (Bic-ELISA) was developed to detect acetamiprid pesticides in pollen, based on the heterogeneous coating antigen and biotinylated anti-acetamiprid monoclonal antibody. Under optimized experimental conditions, the detection limit for the Bic-ELISA was 0.17 ng/mL and the linear range was 0.25–25 ng/mL. The cross-reactivities could be regarded as negligible for the biotinylated antibodies with their analogues except for thiacloprid (1.66%). Analyte recoveries for extracts of spiked pollen (camellia pollen, lotus pollen, rape pollen) ranged from 81.1% to 108.0%, with intra-day relative standard deviations (RSDs) of 4.8% to 10.9%, and the average reproducibility was 85.4% to 110.9% with inter-assay and inter-assay RSDs of 6.1% to 11.7%. The results of Bic-ELISA methods for the Taobao’s website samples were largely consistent with HPLC-MS/MS. Therefore, the established Bic-ELISA methods would be conducive to the monitoring of acetamiprid in pollen.

Development of an immunochromatographic assay for the specific detection of Bacillus thuringiensis (Bt) Cry1Ab toxin

Cry1Ab has been widely used in genetically modified (GM) crops and its amino acid sequence had high identity to Cry1Ac toxin. Existing nanogold immunochromatographic strips cannot distinguish Cry1Ab from Cry1Ac toxin. In this study, a rapid (5-6 min), qualitative nanogold immunochromatographic strip was successfully developed for the specific detection of Cry1Ab toxin. The assay was based on double antibody sandwich format with the visual detection limit (vLOD) of 0.1 μg mL^-1. The results of immunochromatographic assay were all positive validated against the DAS-ELISA (recoveries between 109.6 and 111.8%). In addition, 10%, 5% and 0% error probability results were found in 20 times repeated tests for Cry1Ab concentration of 0.1, 0.2, 0.5 and 1 μg mL^-1, respectively, demonstrating the reproducibility of the test strip. Furthermore, the test strip could be stored for 3 months under dry conditions without significant loss of sensitivity. Furthermore, the practical sample analysis results showed that the test strip was able to detect the presence of Cry1Ab in GM materials containing as low as 0.5% MON 810 Bt maize which indicated the practical value of the test strip. To our knowledge, this is the first report on the detection of Cry1Ab by immunochromatographic assay without interference from Cry1Ac toxin.