Establishment of a Lateral Flow Colloidal Gold Immunoassay Strip for the Rapid Detection of Soybean Allergen β-Conglycinin

A SERS-based immune-nanoprobe for ultrasensitive detection of glycinin via a lateral flow assay

Glycinin is one of the most nutritious ingredients in soybean, but it is also an allergen that can cause allergic reactions in humans and animals, and even endanger life in severe cases. Therefore, it is imperative to develop a rapid and ultrasensitive detection method for glycinin. In order to achieve this goal, this experiment combined surface-enhanced Raman spectroscopy (SERS) technology with an economical, simple, fast and easy-to-carry immunochromatographic test strip, and successfully constructed an efficient sandwich immunochromatographic test strip. The immunoprobe of the test strip was covalently coupled by gold nanostars (AuNSs), Raman molecule 4-aminothiophenol (4-PATP) and rabbit polyclonal antibody. In this experiment, a gold nanostar immunochromatographic test strip for detecting glycinin was established. The detection limit of the test strip was 0.23 ng / mL, the recovery rate was 91.5-96.6 %, and the coefficient of variation was 1.61-6.15 %. In addition, the test strip had no cross reaction with whey protein, wheat protein, peanut protein, sesame protein and β-conglycinin, indicating that the detection method had good specificity and the ability to avoid false positive results. Hence, this experiment successfully prepared a rapid and sensitive test strip for glycinin.

Utilization of a lateral flow colloidal gold immunoassay strip based on surface-enhanced Raman spectroscopy for rapid detection of glycinin

Glycinin is an important storage protein in soybean, but it can also lead to allergic reactions in humans. In this study, based on a low-cost, simple, rapid and portable lateral flow immunoassay test strip, combined with high sensitivity surface enhanced Raman spectroscopy (SERS) technology, a sandwich lateral flow immunochromatographic test strip for rapid detection of soybean allergen glycinin is established. In the experiment, colloidal gold was covalently conjugated with rabbit-derived polyclonal antibodies of glycinin and Raman probe molecule 4-aminothiophenol(4-PATP) to prepare the immunoprobe. The respective optimal PATP and optimal antibody labeling amounts of colloidal gold solution were 1.05 × 10^-2mol/L and 4.6 × 10^-8mol/L. The detection limit of the test strip for glycinin was 4.87 ng/mL. The recovery rate ranged from 91 to 107 % and the CV was between 3 and 10 %. The test strip underwent no cross-reaction with β-conglycinin, sesame protein, peanut protein, wheat protein or whey protein. The results of the experiment showed that this method exhibits high sensitivity and specificity.

An ultrasensitive monoclonal antibody-based lateral flow immunoassay for the rapid detection of xylazine in milk

In this study, a novel hapten was designed and successfully synthesized to prepared the artificial immunogen against xylazine (XYL), then the monoclonal antibody 1H2-2C6 was obtained and applied to a lateral flow immunoassay (LFI) strip for rapid detection of XYL in milk. The visual detection limit (cutoff value) of the LFI strip was 5 ng/mL, the linear regression formula was Y = -0.521lg(X) + 0.382 (R² = 0.995, n = 6), the linear detection range was 0.16-2.23 ng/mL and the detection limit (LOD) was 0.1 ng/mL. The recovery rates were in the range from 88.95% to 91.45%, the highest coefficient of variation was 8.89% (n = 3). The LFI strip was also validated by LC-MS/MS, as revealed, there were no significance differences between the two methods (the confidence interval was 95%). In brief, the LFI strip provides a reliable, sensitive and portable testing tool for screening of XYL on-site.

Preparation of highly sensitive monoclonal antibody against α-zearalanol based on the similar antigen determinant structure to zearalanone

In this study, we report a new method to prepare highly sensitive monoclonal antibody against α-zearalanol (ZAL) based on a similar antigen determinant structure. Zearalanone (ZAN), structural analogs of ZAL, was modified by oximation to obtain ZAN-O. ZAN-O was then coupled with bovine serum albumin using 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide (EDC) to synthesise the artificial complete antigen ZAN-O-BSA. ZAN-O-BSA was used to immunise the BALB/c mice. The splenocytes of the immunised mice were fused with myeloma NS0 cells. During the process of cell fusion, ZAL was used as an inhibitor instead of ZAN to screen the hybridoma cell lines that can secrete monoclonal antibodies against ZAL. The sensitivity (half inhibitory concentration, IC50) of the prepared monoclonal antibody was 0.475 ng/ml, the limit of detection (LOD) was 0.050 ng/ml, the linear range of detection was 0.066-3.399 ng/ml, the affinity constant Kaff was 6.18×107 l/mol, the cross-reactivity rate with structural analogues, such as β-zearalanol, α-zearalenol, β-zearalenol, ZAN and zearalenone were 28.07, 13.16, 15.83, 60.28 and 7.95% respectively. The cross-reactivity with other mycotoxin and carrier proteins were all less than 0.05%. The prepared monoclonal antibody can be used to establish a highly sensitive immunoassay for the detection of ZAL.

Advances on the rapid and multiplex detection methods of food allergens

With the gradually increasing prevalence of food allergy in recent years, food allergy has become a major public health problem worldwide. The clinical symptoms caused by food allergy seriously affect people's quality of life; there are unknown allergen components in novel food and hidden allergens caused by cross contamination in food processing, which pose a serious risk to allergy sufferers. Thus, rapid and multiplex detection methods are required to achieve on-site detection or examination of allergic components, so as to identify the risk of allergy in time. This paper reviews the progress of high-efficiency detection of food allergens, including enhanced traditional detection techniques and emerging detection techniques with the ability high-throughput detection or screening potential food allergen, such as xMAP, biosensors, biochips, etc. focusing on their sensitivity, applicability of each method in food, along with their pretreatment, advantages, limitation in the application of food analysis. This paper also introduces the challenges faced by these high-efficiency detection technologies, as well as the potential of customized allergen screening methods and rapid on-site detection technology as future research directions.

An electrochemical molecularly imprinted polymer sensor for rapid and selective food allergen detection

Food allergies are a serious and rising public health concern. The potentially fatal consequence of food allergies makes managing them costly and anxiety-inducing. Rapid, on-site detection of allergenic ingredients in foods would greatly improve the health and quality of life of food allergy sufferers. This work demonstrates the feasibility of such a device using molecularly imprinted polymers (MIPs). The MIP sensor can detect allergenic soy markers at concentrations as low as 100 parts-per-billion, two orders of magnitude below clinically relevant thresholds, in both controlled and complex food samples. Sensor performance was qualitatively validated with commercially available soy allergen detection lateral flow devices (LFDs). The outcome of this application will address a long-standing analytical challenge to achieving fast, cost-effective, and scalable methods for direct detection of allergen tracers in food analysis.

The development of lateral flow immunoassay strip tests based on surface enhanced Raman spectroscopy coupled with gold nanoparticles for the rapid detection of soybean allergen β-conglycinin

β-Conglycinin is an important storage protein in soybean, which can potentially cause food allergies in human. In this study, a sensitive mouse monoclonal antibody (3D11 mAb) with a high affinity was prepared, and sandwich lateral flow immunochromatographic detection strips were developed for the rapid detections of the soybean allergen β-conglycinin. The 3D11 mAb was combined with a rabbit polyclonal antibody in order to establish strips. The titer of 3D11 mAb was 1:2.56 × 105. The affinity constant of the 3D11 mAb was 9.6 × 109. The lowest detection limit with the naked eye of the double antibody sandwich strips was 1 μg/mL. In addition, chemical molecules p-aminothiophenol with colloidal gold were used as Raman enhancement signals in order to achieve quantitative detections of the β-conglycinin. It was determined in this study that the practical working range of the β-conglycinin concentrations was between 160 ng/mL and 100 μg/mL with the developed assay.

Broad-spectrum detection of zeranol and its analogues by a colloidal gold-based lateral flow immunochromatographic assay in milk

Based on colloidal gold and broad-spectrum monoclonal antibody that binds to zeranol and its five analogues with high sensitivity, a lateral flow immunochromatographic assay (LFIA) in a competitive format was developed to specifically determine residues of zeranol, an illegal growth promoter in livestock. In this study, the assay had high sensitivity and was broad-spectrum only for zeranol and its five analogues, and the results were obtained within 10 min without needing sophisticated procedures. The cutoff values for zeranol and its five analogues were 10 ng/mL, and the IC₅₀ values for zeranol, β-zearalanol, zearalanone, α-zearalenol, β-zearalenol and zearalenone were 1.250, 1.800, 1.775, 1.225, 1.709 and 1.319 ng/mL, respectively. The recovery rates were ranged from 85.6 to 93.9%, with the coefficient of variations less than 12.4%. The results demonstrated that the LFIA could be used for rapid, simultaneous, semi-quantitative and quantitative detection of residues of zeranol and its five analogous in milk.

A critical review of the specifications and performance of antibody and DNA-based methods for detection and quantification of allergens in foods

Despite the availability of a large number of antibody and DNA based methods for detection and quantification of allergens in food there remain significant difficulties in selecting the optimum technique to employ. Published methods from research groups mostly contain sufficient detail concerning target antigen, calibration procedures and method performance to allow replication by others. However, routine allergen testing by the food industry relies upon commercialised test kits and frequently the suppliers provide disappointingly little specification detail on the grounds that this is proprietary information. In this review we have made a critical assessment of the published literature describing the performance of both commercial and non-commercial test kits for food allergens over the period 2008-2018. Mass spectrometric methods, which have the potential to become reference methods for allergens, are not covered in this review. Available information on the specifications of commercial ELISA and LFD test kits are tabulated for milk, egg and peanut allergens, where possible linking to publications concerning collaborative studies and proficiency testing. For a number of commercial PCR test kits, specifications provided by manufacturers for detection of a small selection of allergen are tabulated. In conclusion we support the views of others of the critical need for allergen reference materials as the way forward to improve the comparability of different testing strategies in foods.

Rapid Antibody Selection Using Surface Plasmon Resonance for High-Speed and Sensitive Hazelnut Lateral Flow Prototypes

Lateral Flow Immunoassays (LFIAs) allow for rapid, low-cost, screening of many biomolecules such as food allergens. Despite being classified as rapid tests, many LFIAs take 10⁻20 min to complete. For a really high-speed LFIA, it is necessary to assess antibody association kinetics. By using a label-free optical technique such as Surface Plasmon Resonance (SPR), it is possible to screen crude monoclonal antibody (mAb) preparations for their association rates against a target. Herein, we describe an SPR-based method for screening and selecting crude anti-hazelnut antibodies based on their relative association rates, cross reactivity and sandwich pairing capabilities, for subsequent application in a rapid ligand binding assay. Thanks to the SPR selection process, only the fast mAb (F-50-6B12) and the slow (S-50-5H9) mAb needed purification for labelling with carbon nanoparticles to exploit high-speed LFIA prototypes. The kinetics observed in SPR were reflected in LFIA, with the test line appearing within 30 s, almost two times faster when F-50-6B12 was used, compared with S-50-5H9. Additionally, the LFIAs have demonstrated their future applicability to real life samples by detecting hazelnut in the sub-ppm range in a cookie matrix. Finally, these LFIAs not only provide a qualitative result when read visually, but also generate semi-quantitative data when exploiting freely downloadable smartphone apps.

A Lateral Flow Immunochromato-graphic Strip Test for Rapid Detection of Oseltamivir Phosphate in Egg and Chicken Meat

A lateral flow immunochromatographic strip test (LFIST) based on a competitive format was developed for rapid and sensitive on-site detection of oseltamivir phosphate (OP) residues in poultry product. The sensitivity (half inhibitory concentration, IC₅₀) of the LFIST in the detection of egg and chicken meat samples was confirmed to be 2.56 and 2.63 µg/kg, and the limit detection (LOD) value were 0.43 and 0.42 µg/kg, respectively. For intra-assay and inter-assay reproducibility, recoveries of OP spiked samples ranged between 82.8% and 91.2% with coefficients of variations (CV) less than 5.67% (intra-assay) and 6.52% (inter-assay). The performance of LFIST was comparable to high-performance liquid chromatography (HPLC) in a parallel testing of egg samples and chicken samples. LFIST takes less than 5 minutes, eliminates the dependency on professional personnel, and thus can be used as a surveillance tool for on-site detection of OP residues.

A lateral flow immunochromatographic strip test for rapid detection of hexoestrol in fish samples

A lateral flow immunochromatographic strip test was developed for rapid and sensitive on-site detection of hexoestrol (HES) residues in fish samples with colloidal gold labelling of the anti-HES monoclonal antibody. The strip is composed of a sample pad, a conjugate reagent pad, an absorbent pad and a test membrane containing a control line and a test line. The sensitivity (half inhibitory concentration, IC50) of the strip in the detection of fish extract samples was confirmed to be 1.86 µg kg-1, and the limit of detection value was 0.62 µg kg-1. For intra-assay and inter-assay reproducibility, recoveries of HES-spiked samples ranged from 86.3% to 92.3% and 85.8% to 93.4%, coefficients of variation were 2.91-4.64% and 4.24-5.17%, respectively. High-performance liquid chromatography was employed to confirm the performance of the strip. The strip test takes less than 10 min, and thus provides a repaid method for on-site detection of HES residues.