A Polydopamine-Coated Gold Nanoparticles Quenching Quantum Dots-Based Dual-Readout Lateral Flow Immunoassay for Sensitive Detection of Carbendazim in Agriproducts.

In this study, a fluorometric and colorimetric dual-readout lateral flow immunoassay (LFIA) using antibody functionalized polydopamine-coated gold nanoparticles (Au@PDAs) as a probe was developed for the detection of carbendazim (CBD). Colloidal gold nanoparticles (AuNPs) were coated with polydopamines (PDA) by the oxidation of dopamine to synthesize Au@PDA nanoparticles. The Au@PDA nanoparticles mediated ZnCdSe/ZnS quantum dots (QDs) fluorescence quenching and recovery, resulting in a reverse fluorescence enhancement detection format of CBD. The CBD detection was obtained by the competition between the CBD and the immobilized antigen for Au@PDAs labelled antibody binding, resulting in a significant fluorescence increase and colorimetry decrease corresponded to the concentration of CBD. Dual readout modes were incorporated into the LFIA using the colorimetry signal under natural light and the fluorescence signal under UV light. The cut-off value in the mode of the colorimetric signal and fluorometric signal for CBD detection was 0.5 µg/mL and 0.0156 µg/mL, respectively. The sensitivity of LFIA of the fluorescence mode was 32 times higher than that of the colorimetry mode. There was negligible cross reactivity obtained by using LFIA for the determination of thiabendazole, benomyl, thiophanate-methyl, and thiophanate-ethyl. Consistent and satisfactory results have been achieved by comparing the results of Au@PDAs-QDs-LFIA and liquid chromatography-tandem mass spectrometry (LC-MS/MS) testing spiked cucumber and strawberry samples, indicating good reliability of the Au@PDAs-QDs-LFIA.

Ecosystem impact and dietary exposure of polychlorinated biphenyls (PCBs) and heavy metals in Chinese mitten crabs (Eriocheir sinensis) and their farming areas in Jiangsu, China.

This study investigated the presence of 18 dioxin-like and non-dioxin-like polychlorinated biphenyls (dl- and ndl-PCBs), heavy metals (Cd, Hg, Pb, and As) in Chinese mitten crabs (Eriocheir sinensis) and their distribution in Jiangsu, China. Risk assessment and source apportionment were employed for evaluating the eco-toxicological impact and human exposure. It was found that the compositions of PCBs varied spatially, suggesting different sources of pollutants, whilst PCB 28, 105, 114, and 126 were consistently found in all sample types, suggesting a common pollution source remained, and the bio-accumulation process was in effect. The total PCBs in sediment were found much higher than in water, and brown meat had the highest and most diverse PCB congeners among all tissues. The presence of heavy metals was found in all samples in descending order of As>Cd>Pb>Hg and in the order of shell>brown meat>white meat>gill for crabs. The results of risk assessment indicated that the potential carcinogenic and non-carcinogenic risks were within the acceptable range for long-term consumption of the crabs overall. However, the highest toxic equivalent (TEQ), carcinogenic, and non-carcinogenic risks were all recorded in Location C, where dl-PCB 126, 169, and As contributed to the majority of the risks. The ecological risk posed by all HMs was low, but cases of serious point source pollution have been found in the investigated regions, and risks caused by Cd individually should raise concerns. Source apportionment study revealed that the contaminants mostly originated from anthropogenic activities. Natural deposition and transportation played an important role as well.

Sensitive Immunochromatographic Assay Using Highly Luminescent Quantum Dot Nanobeads as Tracer for the Detection of Cyproheptadine Hydrochloride in Animal-Derived Food.

Cyproheptadine hydrochloride (CYP), used as human and veterinary drug, has been used illegally as feed additive for food-producing animals, which could remain in food and jeopardize human health. There is a need for on-site detection of CYP residue in animal-derived food. In this study, a hapten was designed, and a specific monoclonal antibody (mAb) was developed to detect CYP with an IC50 of 1.38 ng/mL and negligible cross-reactivity (CR) for other analogs. Forthermore, a high sensitive immunochromatographic assay (QBs-ICA) was developed using quantum dot nanobeads as reporters. The assay showed the linear detection range (IC20-IC80) of 0.03-0.52 ng/mL, the limit of detection (LOD) and visual detection limit (VDL) reached to 0.01 and 0.625 ng/mL, respectively. Spiked recovery study in pig urine and pork confirmed that the QBs-ICA was applicable for on-site testing. This assay showed better sensitivity and speedy than the reported instrumental analysis and immunoassays.

Production and characterization of a single-chain variable fragment antibody from a site-saturation mutagenesis library derived from the anti-Cry1A monoclonal antibody.

There are plenty of applications of Cry1A toxins (Cry1Aa, Cry1Ab, Cry1Ac) in genetically modified crops, and it is necessary to establish corresponding detection methods. In this study, a single-chain variable fragment (scFv) with high affinities to Cry1A toxins was produced. First, the variable regions of heavy (VH) and light chain (VL) were amplified from hybridoma cell 5B5 which secrete anti-Cry1A monoclonal antibody (mAb) and then spliced into scFv-5B5 by overlap extension polymerase chain reaction (SOE-PCR). Subsequently, site-saturation mutagenesis was performed after homology modeling and molecular docking, which showed that asparagine35, phenylalanine36, isoleucine104, tyrosine105, and serine196, respectively, located in VH complementarity-determining region (CDR1 and CDR3) and VL framework region (FR3) were key amino acid sites. Then, the mutagenesis scFv library (1.35 × 105 CFU/mL) was constructed and a mutant scFv-2G12 with equilibrium dissociation constant (KD) value of 9.819 × 10-9 M against Cry1Ab toxin, which was lower than scFv-5B5 (2.025 × 10-8 M) was obtained by biopanning. Then, enzyme-linked immunosorbent assay (ELISA) was established with limit of detection (LOD) and limit of quantitation (LOQ) of 4.6-9.2 and 11.1-17.1 ng mL-1 respectively for scFv-2G12, which were lower than scFv-5B5 (12.4-22.0 and 23.6-39.7 ng mL-1). Results indicated the promising prospect of scFv-2G12 used for the detection of Cry1A toxins.