Synthesis and Identification of Artificial Antigen for Imidacloprid

Rapid screening of imidacloprid residue in grains and medicinal herbs: A newly designed hapten and monoclonal antibody

Three different imidacloprid hapten structures were designed to conjugate with proteins (bovine serum albumin, BSA; ovalbumin, OVA; keyhole limpet hemocyanin, KLH) for screening the optimal immunogen and coating antigen. Among these, an unreported antigen (hapten 6-KLH) was selected as the optimal immunogen and coating antigen. In addition, an imidacloprid-specific and high titer monoclonal antibody (IMIB7C3) was obtained by using the above-selected immunogen. A sensitive ic-ELISA (indirect competitive enzyme-linked immunosorbent assay) with a half-maximal inhibitory concentration (IC₅₀) of 1.3 ng mL^-1 was established by using the IMIB7C3 antibody (only 1.2 ng per well) to detect the residues of imidacloprid in grains (wheat and maize) and different herbs (Notoginseng radix et rhizoma, Dioscoreae rhizoma, Lonicerae japonicae flos, Astragali radix, Jujubae fructus). The detection results of real samples by the developed immunoassay were confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), which proved the accuracy and reliability of the established ic-ELISA. These results indicate that the proposed ic-ELISA method is suitable for rapid and high-throughput detection of imidacloprid residues in agricultural products and medicinal herbs. Furthermore, a quantitative risk assessment was conducted for Lonicerae japonicae flos based on the detection results, which indicates an acceptable risk to human health after the intake of Lonicerae japonicae flos polluted by imidacloprid.

Development of immunochromatographic assays for the detection of imidacloprid in soil chemical barrier

A soil chemical barrier is the most important and common way to control termites; fast and on-site detection methods are significant tools to verify pesticide content meeting the standard requirements. In this study, conventional and enhanced immunochromatographic assays (ICAs) containing two test lines (TLs) were developed to semi-quantitatively detect imidacloprid in soil chemical barrier, and detection results were quantified by a smart phone. According to the results, the disappearance concentrations of first TL (TL-1) and second TL (TL-2) in an enhanced ICA and conventional ICA were 5 and 20 ng/mL and 20 and 80 ng/mL with the naked eye. The sensitivity of TL-2 was four times that of TL-1 in both ICAs, consistent with the maximum and minimum concentration differences for imidacloprid in Jiangsu province's "the technical regulation of assay and evaluation on chemical soil barrier of termite prevention treatment in buildings". The results of TLs can be used to judge whether the amount of imidacloprid in soil chemical barrier meets the standard. Enhanced and conventional ICAs were available for further quantitative testing with a smart phone, and the limit of detection (LOD) was 0.74 and 3.17 ng/mL, respectively. Moreover, some soil chemical barrier samples from several areas in Wuxi, Jiangsu province, were used to test by ICAs and high-performance liquid chromatography (HPLC), and the results of ICAs correlated well with HPLC.

Highly sensitive and specific detection of neonicotinoid insecticide imidacloprid in environmental and food samples by a polyclonal antibody-based enzyme-linked immunosorbent assay

BACKGROUND

Imidacloprid is one of the main neonicotinoid insecticides widely used in agriculture owing its broad spectrum of activity and low bioaccumulation. However, imidacloprid is toxic to honey bees and other beneficial organisms, and its residues may occur in environmental and food samples, posing a potential hazard to consumers. In this study the imidacloprid derivative bearing a three-atom length spacer was synthesized and coupled to carrier proteins. Highly sensitive and specific polyclonal antibodies against imidacloprid were successfully produced and the polyclonal antibody-based enzyme-linked immunosorbent assay (pAb-ELISA) was developed.

RESULTS

The ELISA standard curve was constructed within the concentration range 0.1-100 ng mL(-1). The IC(50) value for nine standard curves was in the range 1.2-3.0 ng mL(-1) and the limit of detection was 0.03-0.16 ng mL(-1). The sensitivity of the assay was one order of magnitude higher than that in most published papers. There was almost no cross-reactivity of the antibody with four structurally related compounds (acetamiprid, nicotine, clothianidin and nitenpyram) and six other compounds, indicating that the assay displays not only high sensitivity but also high specificity. No detectable imidacloprid was found in 11 collected environmental and food samples by the assay. For imidacloprid-spiked samples, acceptable recoveries of 73.4-94.4% and intra-assay coefficients of variation of 2.2-12.8% were obtained. The assay was also validated with high-performance liquid chromatography (HPLC) and a good correlation of ELISA with HPLC was achieved.

CONCLUSION

The proposed ELISA provides a sensitive, specific, simple and cost-effective quantitative/screening method for detecting imidacloprid in environmental and food samples.