Development of immunocolloidal strip for rapid detection of pyrimethanil

Novel litchi-like Au-Ag nanospheres driven dual-readout lateral flow immunoassay for sensitive detection of pyrimethanil

Pyrimethanil (PYR) is a fungicide that is harmful to consumers when present in foods at concentrations greater than maximum permitted residue levels. High-performance immunoprobes and dual-readout strategy may be useful for constructing sensitive lateral flow immunoassay (LFIA). Herein, the prepared litchi-like Au-Ag bimetallic nanospheres (LBNPs) exhibited high mass extinction coefficients and fluorescence quenching constants. Benefiting from LBNPs and dual-readout mode, the limits of detection of LBNPs-CM-LFIA and LBNPs-FQ-LFIA for PYR were 0.957 and 0.713 ng mL-1, which were 2.54- and 3.41-fold lower than that of gold nanoparticles-based LFIA, respectively. The limits of quantitation of LBNPs-CM-LFIA and LBNPs-FQ-LFIA were 3.740 and 1.672 ng mL-1, respectively. LBNPs-LFIA was applied to detect PYR in cucumber and grape samples with satisfactory recovery (90%-111%). LBNPs-LFIA showed good agreement with LC-MS/MS for the detection of PYR in the samples. Accordingly, this sensitive and accurate dual-readout LFIA based on LBNPs can be effectively applied for food safety.

Development of monoclonal antibodies for the detection of diuron in water and sugarcane and their application in immunochromatographic strips

Diuron (DR) as a chemical herbicide persists in soil and water for a long time and causes extensive harm to humans. We have produced an excellent monoclonal antibody (mAb) with the ability to sensitively and specifically recognize DR in water and sugarcane samples. The semi-inhibitory concentration (IC₅₀) of this mAb was 0.28 ng mL^-1, and the limit of detection (LOD) was 0.07 ng mL^-1. Based on the mAb, an immunochromatographic assay (ICA) strip was developed. The visual detection limits of the strip assay were estimated, and the critical values of DR in water and sugarcane samples were determined to be 5 and 10 ng mL^-1, respectively, when assessed by the naked eye. The ICA strip was validated by HPLC-MS for water and sugarcane samples which had been spiked with DR. This ICA strip could be a useful tool for in-site and rapid detection of DR in water and sugarcane samples.

Gold-based immunochromatographic strip assay for detecting dimethomorph in vegetables

Gold-based immunochromatographic strip assay for detecting dimethomorph in vegetables.

Fluorescence-based immunochromatographic test strip for the detection of hyoscyamine

Hyoscyamine (HSM), which acts as an antagonist of the acetylcholine muscarinic receptor and can induce a variety of distinct toxic syndromes in mammals (anti-cholinergic poisoning), is hazardous to human health. Therefore, it is urgent to develop a rapid, sensitive, and cost-effective method to determine HSM. A fluorescent microsphere based immunochromatographic assay was developed for this analyte and gold nanoparticles (AuNPs) were used as a comparison. A monoclonal antibody against HSM was prepared with a 50% inhibition concentration (IC₅₀) of 1.17 ng mL^-1, with no cross-reactivity with five drugs. Under optimized conditions, the cut off limits using the fluorescence-labeled monoclonal antibody strips were 10 ng mL^-1 in 0.01 M PBS and 20 ng mL^-1 in pork, pig urine, and honey samples, and the assay could be completed within 10 min. In comparison with a AuNP immunochromatographic assay, the developed method offered a higher coupling rate and lower amounts of antibodies. This approach could be used for simple, sensitive and rapid screening, and is suitable for on-site screening applications.

An ic-ELISA and immunochromatographic strip assay for the detection of 2,4-dichlorophenoxyacetic acid in bean sprouts and cabbage

The compound 2,4-dichlorophenoxyacetic acid (2,4-D) is a synthetic plant growth regulator, which is widely used in agricultural production. Consequently, it is necessary to establish a rapid and sensitive detection method to monitor its use and prevent the environmental and human health problems caused by overuse. In this study, a monoclonal antibody (mAb) 2D5 against 2,4-D was prepared, and based on it, an ic-ELISA and an immunochromatographic strip assay (ICA) were developed for rapid detection. The 50% inhibitory concentration (IC ₅₀) of the mAb against 2,4-D was 1.7 ng mL^-1 and the mAb showed no cross-reactivity with other plant growth regulators with similar structures to 2,4-D. Under optimum conditions, the ICA showed a visual detection limit (vLOD) of 20 ng mL^-1 and a cut-off value of 200 ng mL^-1 in bean sprouts, and cabbage samples gave the same results. The quantitative detection showed the linear detection ranges for bean sprouts and cabbage samples were 6.3-73.0 and 5.4-132.6 ng mL^-1, respectively. The ICA was successfully applied to detect 2,4-D in bean sprouts and cabbage samples and achieved good recoveries ranging from 94.7% to 104.3% with a coefficient of variation (CV) less than 8.3%. Hence, the ICA provides a sensitive, efficient and reliable detection method, which has broad application prospects in the detection of a large number of samples.

Gold-based immunochromatographic assay strip for the detection of quinclorac in foods

In this study, a highly specific and sensitive monoclonal antibody (mAb) against quinclorac (Qui) was prepared. Based on the selected mAb, 2G3, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and an immunochromatographic strip assay were established for the detection of Qui in actual samples. The 50%-inhibitory concentration of mAb 2G3 against Qui was 48.763 ng mL^-1. No cross-reaction with other quinolines indicated that mAb 2G3 had high specificity. The recovery of the established ic-ELISA method was in the range of 85.6% to 98.9%. The cut-off value of Qui in cucumber and tomato by immunochromatographic strip was 200 ng g^-1. The analysis results of ic-ELISA and immunochromatographic strip assay were consistent with the results of LC-MS/MS, which further proved that the established ic-ELISA and immunochromatographic strip assay could provide valuable tools for the rapid detection of Qui residues in cucumber and tomato samples.

Methods for quantifying phenolphthalein in slimming tea

Because of increasing levels of obesity and the development of social network platforms, the online sale of slimming beverages has become very common. However, such beverages are often reported to contain hazardous drugs, such as phenolphthalein. In the present study, we established a rapid and sensitive immunochromatography gold-labeled monoclonal antibody (mAb) (IGM) method and a fluorescence-labeled mAb (IFM) method for determining phenolphthalein in ten types of slimming tea. The monoclonal antibodies and coating antigens were produced in our laboratory. Under optimal conditions, the cut-off limits were 250 ng mL-1 (IFM strip) and 500 ng mL-1 (IGM strip) in both 0.01 M phosphate-buffered saline (PBS) and samples of slimming tea. The mean recoveries were 96.2 to 104.7% for the IGM strip and 90.7 to 104.7% for the IFM strip. The data showed that the IFM strip was more sensitive than the IGM strip and that results could be generated within 10 min. Consequently, this novel technique represents a rapid and convenient method with which to detect phenolphthalein.

Lateral flow immunoassay for the simultaneous detection of fipronil and its metabolites in food samples

We developed a sensitive and rapid lateral flow immunochromatographic (LFI) assay for the simultaneous detection of fipronil and its metabolites in eggs and cucumbers using gold nanoparticle (GNP)-labeled monoclonal antibodies (mAbs). Anti-fipronil mAbs (1B6) were produced using two haptens and identified by heterologous indirect competitive enzyme-linked immunosorbent assay (icELISA) with half maximal inhibitory concentration (IC₅₀) and limit of detection (LOD) values of 0.46 ± 0.07 and 0.05 ± 0.01 ng mL^-1, respectively. The developed LFI strip showed high sensitivity and specificity in the detection of fipronil with cut-off and visual limit of detection (vLOD) values of 10 and 0.25 ng mL^-1, respectively. Furthermore, the application of LFI in the detection of fipronil-spiked egg and cucumber samples was validated by liquid chromatography tandem mass spectrometry (LC-MS/MS). Our developed LFI assay is suitable for detection of fipronil and its metabolites in real samples.

Fluorescence based immunochromatographic sensor for rapid and sensitive detection of tadalafil and comparison with a gold lateral flow immunoassay

Tadalafil (TDL) is an illegal additive drug found in drinks and functional foods that could threaten public health. There was a great concern whether the adulteration occurred in coffee added with similar type of herbs. Here we have developed a rapid, simple, sensitive, and semi-quantitative lateral flow immunoassay (LFIA) based on gold and fluorescence labelled monoclonal antibody (mAb) for detection of TDL in coffee sample. Under optimal conditions, the cut off limits using gold nanoparticles labelled mAb (GLM) was found to be 250 ng/mL and 100 ng mL using fluorescent labelled mAb (FLM) in coffee samples. The coffee samples were spiked with TDL, and the LFIA with GLM gave average recoveries of 92-105.3% (intra-assay) and 96.6-105.9% (inter-assay), meanwhile with FLM gave recoveries 97.9-107.3% (intra-assay) and 98.3-108.9% (inter-assay). Results gave LFIA with FLM more sensitive than with GLM and all the test can be completed within 10 min, which would be an option for convenient and rapid assay of TDL detection.

On-spot quantitative analysis of dicamba in field waters using a lateral flow immunochromatographic strip with smartphone imaging

Dicamba herbicide is increasingly used in the world, in particular' with the widespread cultivation of genetically modified dicamba-resistant crops. However, the drift problem in the field has caused phytotoxicity against naive, sensitive crops, raising legal concerns. Thus, it is particularly timely to develop a method that can be used for on-the-spot rapid detection of dicamba in the field. In this paper, a lateral flow immunochromatographic strip (LFIC) was developed. The quantitative detection can be conducted by an app on a smartphone, named "Color Snap." The tool reported here provides results in 10 min and can detect dicamba in water with a LOD (detection limit) value of 0.1 mg/L. The developed LFIC shows excellent stability and sensitivity appropriate for field analysis. Our sensor is portable and excellent tool for on-site detection with smartphone imaging for better accuracy and precision of the results. Graphical abstract.

Rapid and Sensitive Immunochromatographic Method-Based Monoclonal Antibody for the Quantitative Detection of Metalaxyl in Tobacco

In this study, we prepared a monoclonal antibody (mAb) against metalaxyl (Met) with a half-maximum inhibitory concentration (IC₅₀) of 0.54 ng/mL based on a new hapten, and a gold nanoparticle-based immunochromatographic assay (GICA) was developed for the rapid detection of Met residues in tobacco. Under optimal conditions, even with the naked eye, one can see the semiquantitative analysis results. The naked eye detection limit of Met in tobacco is 25 μg/kg, and the detection threshold is 100 μg/kg. In addition, the cross-reactivity test shows that the mAb has good specificity for Met, and the GICA results have a good correlation with the indirect competitive enzyme-linked immunosorbent assay and liquid chromatography with tandem mass spectrometry test results, which show that the method is feasible and reliable and are more convenient and quicker than the methods using instrumentation for detection. Therefore, GICA may provide a useful tool for the rapid screening and detection of Met residues in tobacco.