An innovative hapten and monoclonal antibody-based immunoassay for determining tebuconazole residues in aqueous samples

Development of an immunochromatographic assay for the rapid screening of torasemide in health food

Torasemide is a new loop diuretic agent added illegally to health foods for weight loss, which can result in serious health risks for consumers. A rapid and sensitive immunochromatographic assay for detection of torasemide (ICA) based on a new monoclonal antibody (mAb) was developed. The mAb IC50 for torasemide was 0.93 ng/mL, and the mAb did not cross-react with other analogues. In PBS, the cut-off value and limit of detection were 1 ng/mL and 0.11 ng/mL, respectively, with a linear range between 0.61 and 6.13 ng/mL. In slimming tablet and capsule samples, the cut-off value was 5 ng/g. Recoveries were 101.1% ± 1.7%-106.1% ± 1.3% in tablet samples and 101.2% ± 2.2%-109.1% ± 3.9% in capsule samples, with coefficients of variation 2.1%-3.1% and 1.8%-3.6%, respectively, consistent with existing LC-MS/MS methods. Therefore, the ICA is suitable for use in slimming tablet and capsule samples.

Identifying fungicide difenoconazole as illegal growth regulator in vegetable: Computer-aided hapten similarity to enhance immunoassay sensitivity

Difenoconazole, a fungicide with broad-spectrum properties, has recently been found to have been used illegally used as a plant growth regulator in Brassica campestris, with the intent of inducing thick stems and dark green leaves. However, analysts have encountered challenges in implementing a rapid surveillance screening approach for this purpose. In this study, a novel hapten was designed to improve the analytical performance of difenoconazole immunoassay. Specifically, the triazole of the original hapten was replaced with a benzene ring, guided by molecular simulation. This led to the development of a very sensitive antibody and the subsequent development of a competitive indirect enzyme linked immunosorbent assay (ciELISA) for the detection of difenoconazole in vegetable samples. The assay exhibited a working range of 0.16 ng mL^-1 to 9.64 ng mL^-1, with a detection limit of 0.05 ng mL^-1. Upon analysis of blind samples, a strong correlation was observed between the ciELISA and HPLC-MS/MS methods. As a result, the proposed technique may prove to be an excellent tool for the rapid detection of difenoconazole overuse and adulteration in vegetables.

Ultrasensitive immunochromatographic strip for the detection of cyhalothrin in foods

In this study, a highly specific and sensitive monoclonal antibody (mAb) against lambda-cyhalothrin (LCT) was prepared. The half maximal inhibitory concentration (IC₅₀) in the ic-ELISA was 1.2 ng mL^-1 and the limit of detection (LOD) value was 0.2 ng mL^-1. Based on the mAb, an immunochromatographic strip (ICS) was developed to qualitatively and quantitatively detect LCT in cabbage, parsley, spinach, and green tea samples. The results from the qualitative test can be observed with the naked eye within 10 min, and from quantitative detection experiments the linear detection ranges for cabbage, parsley, spinach, and green tea samples were 2.3-122.0, 1.5-98.2, 2.1-145.5, and 6.6-129.7 ng g^-1, respectively. Furthermore, recovery experiments were carried out at three spiked concentrations of LCT (5, 20, and 80 ng g^-1), and the recoveries of the ICS in vegetable samples ranged from 81.2% to 96.7%, with a coefficient of variation (CV) of less than 8.1%. For green tea, the recoveries of the ICS were from 80.4% to 90.7%, with a CV of less than 8.7%. The ICS assay established in this study can be used for the qualitative and quantitative determination of LCT residues in foods and agricultural products.

Highly Specific Monoclonal Antibody and Sensitive Quantum Dot Beads-Based Fluorescence Immunochromatographic Test Strip for Tebuconazole Assay in Agricultural Products

A monoclonal antibody (mAb) was raised against tebuconazole (TEB) using a hapten where the p-chloro substituent of the TEB molecule was replaced with a long-chain carboxylic acid. The resulting mAb showed high sensitivity and specificity against TEB characterized by ELISA with a half-maximal inhibitory concentration (IC50) of 0.19 ng mL-1 and with cross-reactivity (CR) values below 0.01% to several analogues of triazole fungicides. On the basis of the mAb produced, a quantum dot beads-based fluorescence immunochromatographic test strip assay (QBs-FITSA) was developed for rapid and sensitive detection of TEB in agricultural product samples. The QBs-FITSA exhibited a linear detection range from 0.02 to 1.25 ng mL-1 with a limit of detection (LOD) of 0.02 ng mL-1. Furthermore, using produced mAb, multiple high-throughput rapid immunoassay formats could be achieved as a convenient monitoring tool for evaluation of human and environmental exposure to TEB.