Comparison of two fluorescence quantitative immunochromatographic assays for the detection of amantadine in chicken muscle

Multifunctional nanoenzyme lateral flow immunoassay strip for rapid and ultrasensitive detection of carbofuran in vegetables

A lateral flow immunoassay strip (LFIAS) is one of the most frequently rapid test technologies for carbofuran (CAR). Nevertheless, the LFIAS has a poor quantitative capability and low sensitivity. And, it also requires often complex sample handling steps, making testing time longer. In this study, Fe3O4 nanoparticles were successively modified with MIL-100(Fe)-based metal-organic framework (MOF) and chloroplatinic acid hexahydrate to obtain a core-shell complex of Fe3O4-MOF-Pt. The complex had a peroxidase-mimicking activity catalytic function that enabled signal amplification and sensitivity enhancement. Upon coupling with carbofuran monoclonal antibody (CAR-mAb), the magnetic separation properties of the probe enabled target-specific enrichment. The LFIAS based on Fe3O4-MOF-Pt nanocomposites could detect CAR in the range of 0.25-50 ng mL-1 with a limit of detection (LOD) of 0.15 ng mL-1, enabling colorimetric and catalytic analysis. In addition, the method showed high specificity and stability for detecting CAR in various vegetables, and recovery rates of the spiked samples were 91.40%-102.40%. In conclusion, this study provided one-stop detection of "target enrichment-visual inspection". While lowering the LOD, it reduced the detection time and improved the detection efficiency. The multifunctional Fe3O4-MOF-Pt nanocomposite provides an idea for the construction of novel multifunctional probes to improve the detection performance of conventional LFIAS.

Rapid and sensitive quantitation of amitraz in orange, tomato, and eggplant samples using immunochromatographic assay

Amitraz (AMT) is a broad-spectrum formamidine insecticide and acaricide. In this study, we produced an anti-AMT monoclonal antibody (mAb) with high performance. The half-maximal inhibitory concentration of the anti-AMT mAb was 4.418 ng/mL, the cross reactivity with other insecticides was negligible, and an affinity constant was 2.06 × 109 mmol/L. Additionally, we developed an immunochromatographic assay for the rapid detection of AMT residues in oranges, tomatoes, and eggplants. The cut-off values were 2000 μg/kg in oranges and tomato samples and 1000 μg/kg in eggplant samples and the calculated limits of detection were 14.521 μg/kg, 6.281 μg/kg, and 3.518 μg/kg in oranges, tomatoes, and eggplants, respectively, meeting the detection requirements for AMT in fruits and vegetables. The recovery rates ranged between 95.8 % and 105.2 %, consistent with the recovery rates obtained via LC-MS/MS. Our developed immunochromatographic assay can effectively, accurately, and rapidly determine AMT residues in oranges, tomatoes, and eggplants.

Highly Efficient Fabrication of Fluorescent "Turn-On" Lateral Flow Strips for Highly Sensitive Detection of Small Molecules Based on Self-Assembly of AuAg Nanoclusters

Currently, fluorescent "turn-on" lateral flow assay (FONLFA) has shown enhanced "naked eye" detection sensitivity for small molecules, while it is urgent to adopt biocompatible fluorescent nanomaterials and needs new strategies to simplify the preparation process. In this study, a highly effective method was proposed to produce FONLFA strips for the detection of small molecules. The gold-silver nanoclusters (AuAgNCs) were immobilized onto the nitrocellulose membrane of the strips by the self-assembly of poly(sodium 4-styrenesulfonate), antigen, and AuAgNCs. The immobilization process entails a straightforward mixing of the three components, taking merely 1 min, thereby bypassing the necessity for chemical modification of fluorescent nanomaterials. The strategy offers a significantly simplified process, which substantially enhances the efficiency of the strip fabrication. Utilizing this method, a FONLFA was developed for carbendazim with a visual limit of detection (vLOD) reduced by 40-fold compared with the conventional colorimetric lateral flow assay (LFA). Furthermore, the approach demonstrates versatility by enabling the immobilization of AuAgNCs and streptavidin, which facilitates the development of aptamer-based FONLFAs. The designed aptamer-based FONLFA for kanamycin exhibited a 50-fold reduction in the vLOD compared with conventional colorimetric LFAs. Therefore, FONLFA holds promising potential for widespread applications in the analysis of small molecules.

Quantitative immunochromatographic assay for rapid and cost-effective on-site detection of benzo[a]pyrene in oilfield chemicals

Contamination of oilfield chemicals (OFCs) by benzo[a]pyrene (B[a]P) is increasingly becoming a severe environmental security issue. There is an urgent need to develop a rapid and accurate method for B[a]P detection in OFCs. In this study, B[a]P hapten was designed using computer aided molecular design. A high-affinity, specific, and matrix-insensitive monoclonal antibody (mAb) with IC50 values of 6.77 ng/mL was obtained. Based on this mAb, we developed a rapid gold nanoparticle-based immunochromatographic strip assay (GICA) with double T-line mode for on-site detection of B[a]P in OFCs samples. The GICA exhibited excellent detection performance in OFCs samples with strong acidity, strong alkalinity, and deep color. Under optimal conditions, the proposed method detected B[a]P in OFCs at 0.42-300 mg/kg, and limit of detection was 0.23-1.07 mg/kg. The recovery rate was 88-106% with a coefficient of variation of 1.46-6.35%. Confirmed by natural positive OFCs samples and high-performance liquid chromatography, this GICA is accurate and reliable, with great potential for rapid and cost-effective on-site detection.

Highly Sensitive Magnetic-Nanoparticle-Based Immunochromatography Assay for Rapid Detection of Amantadine in Chicken and Eggs

Amantadine (AMD) is an antiviral drug that is prohibited for use in livestock and poultry. In this study, carboxyl-modified magnetic nanoparticles (MNPs) were synthesized using the solvothermal method in one step with harmless and inexpensive regents, and they were used to label monoclonal antibodies (mAbs) of AMD in microwells with electrostatic adsorption. Then, a magnetic immunochromatography assay (MICA) method was successfully established. Under optimal conditions, the MICA showed a good performance, with a linear range of 0.2~10.0 µg/L. The limit of detection (LOD) was 0.068 µg/L with the instrument, and the visual LOD (vLOD) was 0.5 µg/L. There was no cross-reaction with rimantadine and ribavirin. The vLOD in real samples was 1.0 µg/kg. The developed MICA has the advantages of convenience, speed, and sensitivity, which make it suitable for the on-site rapid detection of AMD residues in chicken tissues and eggs.

Toward the Development of Simplified Lateral Flow Assays Using Hydrogels as the Universal Control Line

Lateral flow assays (LFA) have been widely utilized as point-of-care testing devices in diverse fields. However, it is imperative to preprint costly bioreceptors onto the lateral flow nitrocellulose membrane at the control line. The complex manufacturing process and relatively limited detection capabilities of LFA have impeded their utilization in more challenging fields. Here, we propose a novel and simple strategy to simplify the manufacture of LFA while simultaneously improving the sensitivity by modifying the hydrogel line (HL). In our study, it was observed that the sensitivity of commercial LFA strips could be enhanced by 2-5-fold by incorporating an extra HL. Particularly, a universal control line was developed to accommodate multiple LFA detection modes by substituting the conventional antibody control line with a hydrogel control line (HCL). As a proof of concept, the HCL performance could be associated with the slowdown and interception effect toward fluid, which are dependent on the permeation and hydrophilicity of the hydrogel with varying concentrations in the nitrocellulose membrane. This new design builds the foundation to enhance the sensitivity and develop the simplified LFA sensing platform without additional complicated processes.

Recent Advances in the Recognition Elements of Sensors to Detect Pyrethroids in Food: A Review

The presence of pyrethroids in food and the environment due to their excessive use and extensive application in the agriculture industry represents a significant threat to public health. Therefore, the determination of the presence of pyrethroids in foods by simple, rapid, and sensitive methods is warranted. Herein, recognition methods for pyrethroids based on electrochemical and optical biosensors from the last five years are reviewed, including surface-enhanced Raman scattering (SERS), surface plasmon resonance (SPR), chemiluminescence, biochemical, fluorescence, and colorimetric methods. In addition, recognition elements used for pyrethroid detection, including enzymes, antigens/antibodies, aptamers, and molecular-imprinted polymers, are classified and discussed based on the bioreceptor types. The current research status, the advantages and disadvantages of existing methods, and future development trends are discussed. The research progress of rapid pyrethroid detection in our laboratory is also presented.