Development of an immunocolloidal strip for rapid detection of picoxystrobin

A paper-based lateral flow immunochromatographic sensor for the detection of tricyclazole in rice

Tricyclazole is commonly used to prevent rice blast to meet the carbohydrate intake needs of half of the global population, and a large number of toxicological reports indicate that monitoring of tricyclazole is necessary. Here, we analyzed the structure of tricyclazole and designed different hapten derivatization strategies to prepare a high-performance monoclonal antibody (half inhibition concentration of 1.61 ng/mL), and then a lateral flow immunochromatographic sensor based on gold nanoparticles for the detection of tricyclazole in rice, with a limit of detection of 6.74 μg/kg and 13.58 μg/kg in polished and brown rice, respectively. The recoveries in rice were in the range of 84.6-107.4%, no complex pretreatment was required for comparison with LC-MS/MS, and the comparative analysis demonstrated that our method had good accuracy and precision. Therefore, the developed lateral flow immunochromatographic analysis was a reliable and rapid means for the on-site analysis of tricyclazole in rice.

Immunoassay for the detection of cyproconazole in foods: From hapten synthesis to the establishment of a gold immunochromatographic assay

Cyproconazole (CPZ) is extensively used in agricultural production. However, its overuse can lead to high residue problems in crops. Existing detection methods are still dominated by instrumental methods and the development of rapid, sensitive field detection remains a challenge. In this study, we designed a novel hapten synthetic pathway and prepared a monoclonal antibody (mAb) that could specifically recognize CPZ with high sensitivity (half inhibition rate was 0.27 ng/mL). From this, a gold immunochromatographic assay (GICA) for the detection of CPZ was established by combining the mAb with gold nanoparticles, with limits of detection in rice, tomatoes and grapes of 0.02 mg/kg, 0.01 mg/kg and 0.05 mg/kg, respectively. The spiked recoveries ranged from 86.5 % to 115.1 %, and the results showed that the GICA was not significantly different from detection using LC-MS/MS. Therefore, we have successfully developed a GICA method for the reliable in situ, rapid and sensitive detection of CPZ.

Development of a Time-Resolved Fluorescent Microsphere Test Strip for Rapid, On-Site, and Sensitive Detection of Picoxystrobin in Vegetables

Picoxystrobin (PIC) is a fungicide extensively used for disease control in both crops and vegetables. Residues of PIC in vegetables pose a potential threat to human health due to their accumulation in the food chain. In this study, a specific PIC monoclonal antibody (mAb) was developed by introducing a carboxylic acid arm into PIC and subsequently preparing a hapten and an artificial antigen. A sensitive and rapid time-resolved fluorescence immunochromatographic assay (TRFICA) was established based on the mAb. Subsequently, using a time-resolved fluorescent microsphere (TRFM) as signal probe, mAbs and microspheres were covalently coupled. The activated pH, the mAb diluents, the mAb amount, and the probe amount were optimized. Under optimized conditions, the quantitative limits of detection (qLOD) of PIC in cucumber, green pepper, and tomato using TRFICA were established at 0.61, 0.26, and 3.44 ng/mL, respectively; the 50% inhibiting concentrations (IC50) were 11.76, 5.29, and 37.68 ng/mL, respectively. The linear ranges were 1.81-76.71, 0.80-35.04, and 8.32-170.55 ng/mL, respectively. The average recovery in cucumber, green pepper, and tomato samples ranged from 79.8% to 105.0%, and the corresponding coefficients of variation (CV) were below 14.2%. In addition, 15 vegetable samples were selected and compared with the results obtained using ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS). The results revealed a high degree of concordance between the proposed method and UPLC-MS/MS. In conclusion, the devised TRFICA method is a valuable tool for rapid, on-site, and highly sensitive detection of PIC residues in vegetables.

Lateral flow immunoassay based on gold nanoparticles for rapid and sensitive detection of zoxamide in grape, tomato and cucumber samples

In the study, we discovered zoxamide hapten (ZOX-hapten) by introducing a carboxyl extension chain, combined it with protein to make a complete antigen to immunize mice, and generated a monoclonal antibody (mAb) against ZOX. To identify ZOX residues in grape, tomato, and cucumber samples, we used our anti-ZOX mAb to develop a lateral flow immunoassay (LFIA) strip. In grape, tomato, and cucumber samples, the calculated detection limit of the LFIA strip in grape, tomato and cucumber samples was 3.44, 4.78 and 3.53 ng/g, respectively. Using the LFIA strip, the recovery rate from grape samples was 96.4-106.8%, and that from tomato samples was 98.4-107.5%, while the recovery from cucumber samples was 99.4-111.3%. These results showed that our LFIA strip could be expected to achieve rapid screening of ZOX residues in fruits and vegetables.

Immunochromatographic assay for the analysis of methomyl in cabbage and tomato

In this study, a hapten of methomyl was designed and used to produce monoclonal antibodies (mAbs) against methomyl. Based on these mAbs, we developed an enzyme-linked immunosorbent assay (ELISA) and immunochromatographic assay (ICA) strip for the determination of methomyl residues. Results from the ELISA showed that mAb 1D10 exhibited higher affinity with an affinity constant of 2.76 × 10¹⁰ L/mol and higher sensitivity with a limit of detection (LOD) was 8.12 ng/mL. After optimizing the ICA, a visible limit of detection (vLOD) was found to be 100 ng/g and the cut-off value was 500 ng/g for methomyl in cabbage and tomato. The calculated LODs were 3.2 ng/g and 5.4 ng/g in cabbage and tomato, respectively. Moreover, results from the ICA were consistent with those of the ELISA in our recovery assay using spiked samples. Hence, the ICA method has a bright future and great prospects for the detection of methomyl in food samples.

An Immunochromatographic Assay for the Rapid and Qualitative Detection of Mercury in Rice

Mercury is a major pollutant in food crops. In this study, we synthesized an anti-mercury monoclonal antibody (mAb; IC₅₀ was 0.606 ng mL⁻¹) with high sensitivity and specificity and different immunogens and coating antigens and developed an immuno-chromatographic assay (ICA) for the detection of mercury in rice. The ICA strip had a visible detection limit of 20 ng g⁻¹ and a cut-off value of 500 ng g⁻¹ in rice. The performance of the ICA strip was consistent with that of ICP-MS and ic-ELISA. The recoveries of mercury in rice ranged from 94.5% to 113.7% with ic-ELISA and from 93.6% to 116.45% with ICP-MS. Qualitative analysis by ICA can be obtained with the naked eye. The ICA strip is an effective and practical method for the rapid and high-throughput determination of mercury in rice.

Ultrasensitive paper sensor for simultaneous detection of alpha-amanitin and beta-amanitin by the production of monoclonal antibodies

Amanitin (AMA) is responsible for human fatalities after ingestion of poisonous mushrooms, thus, a rapid and accurate detection method is urgently needed. Here, gold nanoparticle-based immunosensor with monoclonal antibody against AMA was constructed for rapid detection of alpha- and beta-amanitin (α- and β-AMA) in mushroom, serum and urine samples. Under optimized conditions, the visual limits of detection (vLOD) and calculated LOD for α-AMA and β-AMA in mushroom were 10 ng/g, 20 ng/g, and 0.1 ng/g, 0.2 ng/g, respectively. Analysis of wild mushroom samples was also performed using a strip scan reader in the 10 min range. Furthermore, in mushrooms containing amatoxins results were confirmed and compared with those determined by liquid chromatography tandem mass spectrometry. Thus, this immunosensor provided a useful monitoring tool for rapid detection and screening of mushroom samples and in serum and urine from subjects who accidentally consumed AMA-containing mushrooms.

A monoclonal antibody-based colloidal gold immunochromatographic strip for the analysis of novobiocin in beef and chicken

In this study, a monoclonal antibody (mAb) 1G5 against novobiocin with high sensitivity and specificity was prepared from a newly-designed hapten. According to the results of an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA), the 50%-inhibitory concentration of the anti-novobiocin mAb was 6.9 ng/mL and the cross-reactivity was less than 0.1% to its analogues. Furthermore, a rapid colloidal gold immunochromatographic assay (ICA) was successfully developed for the determination of novobiocin in spiked samples. Two calibration curves were established respectively, for beef and chicken samples. The ICA results showed a visual colorimetric value of 50 ng/mL and a cut-off value of 300 ng/mL in beef samples. The ICA results of chicken samples were almost the same as that of beef. When quantitative detection was performed using a strip reader, the detection ranges for quantitative analysis in beef and chicken were 23.7-287.5 and 19.7-263.8 µg/kg respectively. Recoveries were between 82.7 and 95.3% for beef samples with the coefficient of variation (CV) ranging from 2.5 to 5.1%. Recoveries were in the range of 89.6-105.5% with the CV ranging from 2.9% to 6.3% for chicken samples. Importantly, these results from the ICA were highly consistent with the results obtained by LC-MS/MS. Therefore, this ICA could be used as an alternative means for the rapid determination of NOV in a large number of beef and chicken samples.

Gold nanoparticle-based immunoassay for the detection of bifenthrin in vegetables

We have developed a sensitive and rapid gold nanoparticle-based immunochromatographic strip (GNP-ICS) for the detection of bifenthrin (BF) using an anti-BF monoclonal antibody (mAb). When used in indirect competitive enzyme-linked immunosorbent assay (icELISA), the specific anti-BF mAb (3D1) had a half-maximal inhibitory concentration (IC₅₀) and limit of detection (LOD) of 59 and 15 ng mL^-1 respectively. Additionally, its cross-reactivity (CR) with other pyrethroids was negative. The developed GNP-ICS assay based on the GNP-labelled mAb was specific and sensitive for determining BF, with a cut-off value of 1,000 ng mL^-1, and a visual LOD (vLOD) value of 50 ng mL^-1. Furthermore, the developed icELISA and GNP-ICS were applied with a simple pre-treatment to determine BF-spiked vegetable samples, and the recoveries were validated using gas chromatography-mass spectrometry (GC-MS). The results revealed that the developed GNP-ICS was reliable for the detection of BF in practical samples.

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..

Simultaneous detection of phenacetin and paracetamol using ELISA and a gold nanoparticle-based immunochromatographic test strip

We have developed a sensitive and rapid gold nanoparticle-based immunochromatographic strip (GNP-ICS) for the detection of phenacetin (PNCT) and paracetamol (PAP) using an anti-PNCT monoclonal antibody (mAb). The sensitive anti-PNCT mAb (2D6) had a half maximal inhibitory concentration (IC₅₀) and limit of detection (LOD) of 3.51 and 0.21 ng mL^-1, respectively. Additionally, its cross-reactivity with PAP was approximately 10.1%. The developed GNP-ICS assay based on GNP-labeled mAb was sensitive for the detection of PNCT with vLOD and cut-off values of 2.5 and 50 ng mL^-1 respectively and a vLOD value of 25 ng mL^-1 for PAP. Furthermore, the developed icELISA and GNP-ICS assays were applied to determine PNCT-spiked beverage samples without pretreatment, in addition to a kind of PAP-containing drug. The recoveries were validated using high performance liquid chromatography (HPLC). The results revealed that the developed GNP-ICS assay was reliable for the detection of PNCT in practical samples.

A gold-based strip sensor for the detection of benzo[a]pyrene in edible oils

This report describes the development of a sensitive and broadly specific indirect competitive enzyme-linked immunosorbent assay (icELISA) and a gold nanoparticle-based immunochromatographic strip (GNP-ICS) assay for the detection of benzo[a]pyrene (B[a]P), using an anti-B[a]P monoclonal antibody (mAb). A broad-specific anti-B[a]P mAb (4E8) was raised from two types of haptens, with half maximal inhibitory concentrations and limits of detection (LOD) values of 2.51 and 0.54 ng mL-1, respectively. In addition, the cross-reactivity was up to 390% with structurally related compounds. The GNP-ICS assay based on a GNP-labeled mAb showed broad specificity in the detection of B[a]P and its analogues, with cut-off and visual LOD values of 100 and 10 ng mL-1, respectively. Furthermore, the recoveries from the developed icELISA and GNP-ICS assay in edible oil samples spiked with B[a]P were validated by high-performance liquid chromatography-fluorescence detection. The results revealed that the icELISA could reliably detect B[a]P in edible oils.