Developing an ultrasensitive immunochromatographic assay for authentication of an emergent fraud aminopyrine in herbal tea.

Aminopyrine is a nonsteroidal anti-inflammatory drug only for medical purposes, however, it has been illegally added in traditional Chinese herbal teas for fraud activity recently. In this study, a specific antibody against aminopyrine with IC50 of 3.00 ng/mL was obtained for the first time by a rational hapten design. Furthermore, an ultrasensitive gold nanoparticles immunochromatographic assay (AuNPs-ICA) for determination of aminopyrine based on a portable reader was firstly developed, with cut-off value of 100.00 ng/mL, limit of detection (LOD) of 4.80 ng/mL and limit of quantification (LOQ) of 5.71 ng/mL for herbal tea, respectively. The recovery rates ranged from 93.21 % to 105.61 %, with inter-assay coefficient of variation (CV) from 1.08 % to 3.82 %. Additionally, 24 blind samples were examined simultaneously by AuNPs-ICA and LC-MS/MS, demonstrating a good consistency for each other. The proposed AuNPs-ICA is an ultrasensitive and reliable tool for on-site surveillance screening of fraud additives in herbal tea.

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.

A sensitive and quantitative immunochromatographic assay for simultaneous detection of three stimulant laxatives in slimming food.

Bisacodyl, sodium picosulfate and their metabolite bis-(p-hydroxyphenyl)-pyridyl-2-methane (BHPM) are clinically used to treat constipation. In this study, with the rational hapten design, a broad-specific and highly sensitive monoclonal antibody (mAb) was obtained with half of inhibitory concentrations of 0.16, 0.18 and 0.65 ng/mL for bisacodyl, sodium picosulfate and BHPM, respectively. Based on this mAb, a rapid and sensitive lateral flow immunochromatographic assay toward bisacodyl, sodium picosulfate and BHPM in slimming foods was developed. This method can qualitatively and quantitatively screen three stimulant laxatives with cut-off values of 3-6 ng/mL by naked eye and quantitative detection limits of 0.14-0.41 ng/mL by reader. The acceptable recoveries of spiked samples (78.00 %-120.12 %) and consistent results with liquid chromatography with tandem mass spectrometry (LC-MS/MS) in real sample detection confirmed the accuracy of the method. The established method provides a technique for multiplex, sensitive, fast, and on-site detection of three stimulant laxatives in slimming food.

Authenticating Emergent Adulterant 6-Benzylaminopurine in Bean Sprouts: Virtual Hapten Similarity Enhanced Immunoassay.

6-Benzylaminopurine (6-BA), a plant growth regulator with cytokinin-like properties, was recently reported to be illegally used in bean sprouts to increase their commercial appearance. It is still nevertheless challenging to quickly detect this adulteration. In this work, four novel haptens (haptens 1-4) of 6-BA were rationally designed with computer-assisted modeling analysis and then synthesized for use as immunizing haptens to produce antibodies. One of two obtained antibodies showed high sensitivity and specificity toward 6-BA. Based on the most sensitive anti-6-BA antibody, an indirect competitive enzyme-linked immunosorbent assay (icELISA) was performed, which demonstrated a 50% inhibition concentration (IC50) of 1.18 µg/L and a limit of detection of 0.075 µg/L. The average recoveries of this icELISA for 6-BA of spiked samples ranged from 87.2 to 95.0% with a coefficient of variation of less than 8.7%. Furthermore, the blind samples were detected simultaneously by the method and HPLC-MS/MS, and the results showed good agreement with each other. Therefore, the proposed icELISA can facilitate the rapid surveillance screening of adulterated 6-BA in sprout vegetables.

Ultrasensitive Magnetic Assisted Lateral Flow Immunoassay Based on Chiral Monoclonal Antibody against R-(-)-Salbutamol of Broad-Specificity for 38 ß-Agonists Detection in Swine Urine and Pork.

Screening for ″zero tolerance″ ß-agonists requires broad-specificity and sensitivity methods. Herein, R-(-)-salbutamol (SAL) is chirally separated and designed as a hapten, and a monoclonal antibody (mAb) was first prepared with an IC50 of 0.27 ng/mL, which can recognize 38 ß-agonists simultaneously. The broad-specificity of chiral mAb was explored by molecular simulation technology. Magnetic nanoparticles (MNPs) were then synthesized and applied as a signal tracer to develop a lateral flow immunoassay (LFIA). The limits of detection of MNPs-LFIA for SAL in swine urine and pork were 0.05 and 0.09 µg/kg, which was (2-125)-fold lower than that of the reported LFIAs. The recoveries were between 95.8 and 116.7%, with the coefficient of variation from 2.7 to 15.4%. Parallel analysis of 44 samples by commercial ELISA kits confirmed the reliability. Therefore, our work not only provides a broad-specificity and ultrasensitive method for ß-agonists but also suggests that chirality is the new general theory that guided the rational hapten design.