Development a monoclonal antibody-based enzyme-linked immunosorbent assay for screening pyrimethanil in fruits and vegetables

Immunochromatographic visualization detection platform for bitertanol in foods

As a widely used fungicide in agriculture, bitertanol (BIT) significantly affects hormone regulation leading to imbalance of homeostasis in vivo, which makes it necessary to monitor BIT residues in foods. In this research, a novel hapten derivation scheme was designed by analyzing the chemical structure of BIT to prepare an anti-BIT monoclonal antibody with high affinity, specificity and sensitivity (half inhibitory concentration of 4.78 ng/mL). Subsequently, a visualized gold immunochromatographic assay (GICA) platform was established based on antigen-antibody specific recognition, with a limit of detection of 0.06 mg/kg and 0.18 mg/kg in cucumber and tomato, respectively. GICA has spiked recoveries of 84.3 %-114.1 %, determines results are not significantly different from those of LC-MS/MS, and the complex purification treatments can be reduced during the detection process. Therefore, the developed GICA is a reliable, rapid, and sensitive method for on-site rapid monitoring of BIT in foods.

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.

Gold-based lateral-flow strip for the detection of penconazole in watermelon and cucumber samples

As a typical triazole fungicide, penconazole (PEN) is widely used in agriculture but has been proven to be toxic. In this study, we designed a new hapten to prepare a highly sensitive and specific anti-PEN monoclonal antibody (mAb) and established a gold nanoparticle-based lateral-flow immunoassay (LFIA) for the detection of PEN residues in watermelon and cucumber. The 50% inhibitory concentration (IC50) of the mAb was 0.42 ng/mL and the LFIA strip had a visual limit of detection (vLOD) of 2.5 ng/g and a cut-off value of 10 ng/g in watermelon and cucumbers. The calculated limit of detection (LOD) of the LFIA strip was 0.36 ng/g for watermelon and 0.29 ng/g for cucumber. The LFIA strip also gave a recovery rate of 92.5–109.0% for watermelon samples and 92.5–106.7% for cucumber samples. These results using the LFIA strip are highly consistent with those seen using LC-MS/MS. Thus our developed LFIA strip represents a potentially reliable tool for the rapid on-site screening for PEN in watermelons and cucumbers..

Development of immunochromatographic strips for the detection of dicofol

In this study, a monoclonal antibody (mAb) against dicofol was developed to prepare immunochromatographic strips (ICAs) for the detection of dicofol residues in fruit and vegetables. The mAb exhibited high affinity and high sensitivity, with an affinity constant of 2.96 × 10¹⁰ and a limit of detection of 3.142 ng mL^-1. A cross reactivity test revealed that the mAb also had good specificity for dicofol. This ICA method gave a visible limit of detection of 50 ng g^-1, and a cut-off value of 500 ng g^-1 for the detection of dicofol in both apple and cucumber with the naked eye. Importantly, the results here are consistent with results obtained using liquid chromatography mass spectrometry and ic-ELISAs indicating that this ICA method is reliable and practical when used for the detection of dicofol in fruit and vegetables.

Visible and eco-friendly immunoassays for the detection of cyclopiazonic acid in maize and rice

Cyclopiazonic acid (CPA) is an indole-tetramine mycotoxin commonly produced by Penicillium and Aspergillus and is widely found in agricultural products, fermented food, and feed. Food contaminated with CPA poses a substantial health risk to consumers. Therefore, eco-friendly immunoassays, including an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and a lateral flow immunochromatographic strip (LFICS), were developed to monitor CPA in maize and rice samples. For this purpose, a monoclonal antibody (3H12) posed highly resistant to pH (5.6 to 9.6) and ethanol (≤50%) was generated by mouse immunization. Negative maize and rice samples or samples spiked with CPA were extracted with ethanol/0.01 M sodium borate buffer (4/1, v/v, pH 8.4). For ic-ELISA analysis, the limits of detection (LODs) were 0.48 and 0.28 ng/g for maize and rice samples, respectively. The recovery for spiked maize was 76.9% to 83.5% with the highest variable coefficient (CV_max ) being 9.32%. For spiked rice, the recovery was 85.3% to 105.1% with a CV_max of 8.56%. For LFICS analysis, the visible LODs were 2.5 and 1 ng/g and cutoff values were 5 and 2.5 ng/g for maize and rice samples, respectively. The LFICS method gave results within 5 to 10 min, providing an auxiliary analytical tool for the rapid, sensitive, and portable screening of the massive samples onsite.