Enzyme-linked immunosorbent assay for triclocarban in aquatic environments

A Novel Lateral Flow Immunochromatographic Assay for Rapid and Simultaneous Detection of Aflatoxin B1 and Zearalenone in Food and Feed Samples Based on Highly Sensitive and Specific Monoclonal Antibodies

Simultaneous aflatoxin (AFB1) and zearalenone (ZEN) contamination in agro-products have become widespread globally and have a toxic superposition effect. In the present study, we describe a highly sensitive and specific dual lateral flow immunochromatographic assay (dual test strip) for rapid and simultaneous detection of AFB1 and ZEN in food and feed samples based on respective monoclonal antibodies (mAbs). Two immunogens AFB1-BSA (an AFB1 and bovine serum albumin (BSA) conjugate) and ZEN-BSA (a ZEN and BSA conjugate) were synthesized in oximation active ester (OAE) and amino glutaraldehyde (AGA). The molecular binding ratio of AFB1:BSA was 8.64:1, and that of ZEN:BSA was 17.2:1, identified by high-resolution mass spectrometry (HRMS) and an ultraviolet spectrometer (UV). The hybridoma cell lines 2A11, 2F6, and 3G2 for AFB1 and 2B6, 4D9 for ZEN were filtered by an indirect non-competitive enzyme-linked immunosorbent assay (inELISA) and an indirect competitive enzyme-linked immunosorbent assay (icELISA), respectively. As AFB1 mAb 2A11 and ZEN mAb 2B6 had the lowest 50% inhibitive concentration (IC50) and cross-reactivity (CR), they were selected for subsequent experiments. By systematically optimizing the preparation condition of gold nanoparticles (AuNPs), AuNPs-labeled mAbs, and detection condition, the visual limit of detection (LOD) of the dual test strip was 1.0 μg/L for AFB1 and 5.0 μg/L for ZEN, whereas that of the test strip reader was 0.23 μg/L for AFB1 and 1.53 μg/L for ZEN. The high reproducibility and stability of the dual test were verified using mycotoxin-spiked samples. The dual test strips were highly specific and sensitive for AFB1 and ZEN, which were validated using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Thus, the proposed AFB1 and ZEN dual test strip is suitable for rapid and simultaneous detection of AFB1 and ZEN contamination in food and feed samples.

Development of a Direct Competitive ELISA Kit for Detecting Deoxynivalenol Contamination in Wheat

This study was conducted to develop a self-assembled direct competitive enzyme-linked immunosorbent assay (dcELISA) kit for the detection of deoxynivalenol (DON) in food and feed grains. Based on the preparation of anti-DON monoclonal antibodies, we established a standard curve with dcELISA and optimized the detection conditions. The performance of the kit was evaluated by comparison with high-performance liquid chromatography (HPLC). The minimum detection limit of DON with the kit was 0.62 ng/mL, the linear range was from 1.0 to 113.24 ng/mL and the half-maximal inhibition concentration (IC₅₀) was 6.61 ng/mL in the working buffer; there was a limit of detection (LOD) of 62 ng/g, and the detection range was from 100 to 11324 ng/g in authentic agricultural samples. We examined four samples of wheat bran, wheat flour, corn flour and corn for DON recovery. The average recovery was in the range of 77.1% to 107.0%, and the relative standard deviation (RSD) ranged from 4.2% to 11.9%. In addition, the kit has the advantages of high specificity, good stability, a long effective life and negligible sample matrix interference. Finally, wheat samples from farms in the six provinces of Henan, Anhui, Hebei, Shandong, Jiangsu and Gansu in China were analyzed by the kit. A total of 30 samples were randomly checked (five samples in each province), and the results were in good agreement with the standardized HPLC method. These tests showed that the dcELISA kit had good performance and met relevant technical requirements, and it had the characteristics of accuracy, reliability, convenience and high-throughput screening for DON detection. Therefore, the developed kit is suitable for rapid screening of DON in marketed products.

An Immunoaffinity Purification Method for the Simultaneous Analysis of Triclocarban and Triclosan in Foodstuffs by Liquid Chromatography Tandem Mass Spectrometry

Triclocarban (TCC) and triclosan (TCS) have been simultaneously detected in five kinds of foodstuffs using an immunoaffinity purification method coupled with ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) for the first time. Two highly specific monoclonal antibodies against TCC and TCS were produced and coupled to N-hydroxysuccinimide-activated Sepharose 6B gel to prepare the immunosorbent. Under the optimal conditions, mean recoveries from spiked samples by the IAC-UHPLC-MS/MS method were 70.1-92.8% for TCC and 76.6-102.5% for TCS. Intraday relative standard deviations were below 14.5%. The limits of quantification (LOQs) of TCC were 1 ng/L for beverage samples and 0.01-0.02 μg/kg for food samples. The LOQs of TCS were 0.03 μg/L for beverage samples and 0.2-0.3 μg/kg for food samples. The applicability of the method has been proven by analyzing TCC and TCS in different samples from supermarkets in Beijing. The proposed method is sufficiently sensitive and reliable for monitoring trace concentrations of TCC and TCS in food samples.

Survey of Deoxynivalenol Contamination in Agricultural Products in the Chinese Market Using An ELISA Kit

A total of 328 agricultural product samples highly suspected to be contaminated, from flour companies, feed companies, and livestock farms throughout China, were surveyed for deoxynivalenol (DON) contamination using a self-assembly enzyme-linked immunosorbent assay (ELISA) kit. An ELISA kit for DON was developed with a 4.9 ng mL-1 limit of detection (LOD) in working buffer and a 200 ng g-1 LOD in authentic samples. The DON contamination detection rate was 88.7%, concentrations ranged from 200.9 to 6480.6 ng g-1, and the highest DON contamination was found in distillers' dried grains with solubles with an average of 3204.5 ng g-1. Wheat bran and wheat were found to be the most commonly contaminated samples, and the corn meal samples had the lowest average DON level. This ELISA kit is a powerful alternative method for the rapid, sensitive, specific, accurate, and high-throughput determination of DON and can meet the maximum requirement levels. This survey suggests that DON contamination in the Chinese market is serious, and the contamination risk deserves attention. Essential preventive measures should be implemented to ensure food safety and human health.