Quantitative Rapid Magnetic Immunoassay for Sensitive Toxin Detection in Food: Non-Covalent Functionalization of Nanolabels vs. Covalent Immobilization

In this study, we present a novel and ultrasensitive magnetic lateral flow immunoassay (LFIA) tailored for the precise detection of zearalenone, a mycotoxin with significant implications for human and animal health. A versatile and straightforward method for creating non-covalent magnetic labels is proposed and comprehensively compared with a covalent immobilization strategy. We employ the magnetic particle quantification (MPQ) technique for precise detection of the labels and characterization of their functionality, including measuring the antibody sorption density on the particle surface. Through kinetic studies using the label-free spectral phase interferometry, the rate and equilibrium constants for the binding of monoclonal antibodies with free (not bound with carrier protein) zearalenone were determined to be kon = 3.42 × 105 M-1s-1, koff = 7.05 × 10-4 s-1, and KD = 2.06 × 10-9 M. The proposed MPQ-LFIA method exhibits detection limits of 2.3 pg/mL and 7.6 pg/mL when employing magnetic labels based on covalent immobilization and non-covalent sorption, with dynamic ranges of 5.5 and 5 orders, correspondingly. We have successfully demonstrated the effective determination of zearalenone in barley flour samples contaminated with Fusarium graminearum. The ease of use and effectiveness of developed test systems further enhances their value as practical tools for addressing mycotoxin contamination challenges.

Development of two immunochromatographic test strips based on signal amplification and selenium nanoparticles for the rapid detection of T-2 mycotoxin

Conventional immunochromatographic test strips (ICSs) based on gold nanoparticle (AuNP) probes offer limited sensitivity. Here, AuNPs were separately labeled with monoclonal or secondary antibodies (MAb or SAb). In addition, spherical, homogeneously dispersed, and stable selenium nanoparticles (SeNPs) were also synthesized. By optimizing the preparation parameters, two ICSs based on the dual AuNP signal amplification (Duo-ICS) or SeNPs (Se-ICS) were developed for the rapid detection of T-2 mycotoxin. The detection sensitivities of the Duo-ICS and Se-ICS assays for T-2 were 1 ng/mL and 0.25 ng/mL, respectively, which were 3-fold and 15-fold more sensitive, respectively, than a conventional ICS. Furthermore, the ICSs were applied in the detection of T-2 in cereals, which requires higher sensitivity. Our findings indicate that both ICS systems can be used for rapid, sensitive, and specific detection of T-2 toxin in cereals and potentially other sample types.

Antibody conjugated magnetic nanoparticle based colorimetric assay for the detection and quantification of aflatoxin B1 in wheat grains

Aflatoxin B1 (AFB1) is a most potent carcinogenic secondary metabolite produced by Aspergillus flavus. As a food safety concern, development of a rapid, cost effective, sensitive and easy to use method for the detection of aflatoxin is of prime requirement. In this study, AFB1 was conjugated with bovine serum albumin (BSA), and AFB1-BSA conjugate was purified by HPLC. Purification was confirmed by UV-Vis spectroscopy, FTIR and MALDI-TOF mass spectrometry. The polyclonal antibody was raised against AFB1-BSA conjugate in rabbit and purified by protein A sepharose and BSA sepharose affinity columns. Iron oxide nanoparticles (MNPs) were synthesised by co-precipitation method and their surface was functionalised with (3-aminopropyl) triethoxysilane (APTES). Size of APTES conjugated MNPs was determined by electron microscopy, and characterised by several biophysical techniques. The purified anti-AFB1 antibody was conjugated with surface functionalised MNPs and the conjugation was confirmed by determining the sizes of free and antibody conjugated MNPs by field emission scanning electron microscope where increase of particle sizes from 10-20 to 40-50 nm was observed due to antibody conjugation. Anti-AFB1 antibody conjugated MNPs were used for capturing AFB1 from the aflatoxin spiked wheat grains with a recovery percentage of more than 80% and used effectively five times. The captured AFB1 was then quantified by a sensitive colorimetric assay where colourless AFB1 was first converted into coumaric acid by NaOH. Subsequently, coumaric acid reacted with 2,6-dibromoquinone-4-chloroimide (DBQC) to a green-coloured indophenol product which was quantified spectrophotometrically. AFB1 contamination as low as 2 μg/kg in wheat grains was detected by the developed technique suggesting its potential application for both qualitative and quantitative analysis of aflatoxins present in feed and food materials.

Competitive fluorometric assay for the food toxin T-2 by using DNA-modified silver nanoclusters, aptamer-modified magnetic beads, and exponential isothermal amplification

The authors describe an aptamer based assay for the mycotoxin T-2. The method is making use of exponential isothermal amplification reaction (EXPAR) and fluorescent silver nanoclusters (AgNCs). Free T-2 and cDNA (which is a DNA that is partially complementary to the aptamer) compete for binding to aptamer-modified magnetic beads. The cDNA collected by magnetic separation can be used as a primer to trigger EXPAR to obtain ssDNA. The C-base-rich ssDNA binds and reduces Ag(I) ion to form fluorescent AgNCs. Fluorescence is measured at excitation/emission wavelengths of 480/525 nm. T-2 can be detected by fluorometry with a detection limit as low as 30 fg·mL^-1. The method was applied to analyse spiked oat and corn, and the average recoveries ranged from 97.3 to 102.3% and from 95.9 to 107.5%, respectively. The results were in good agreement with data of the commercial ELISA kit. The assay is highly sensitive, has a wide analytical range, good specificity and reliable operation. It provides a promising alternative for the standard method for quantitative detection of T-2. Graphical abstract Schematic presentation of fluorometric assay for T-2 based on aptamer-functionalized magnetic beads exponential, isothermal amplification reaction (EXPAR) and fluorescent silver nanoclusters (AgNCs).

Nanoparticles as a Solution for Eliminating the Risk of Mycotoxins

Mycotoxins are toxic secondary metabolites produced by certain filamentous fungi. The occurrence of mycotoxins in food and feed causes negative health impacts on both humans and animals. Clay binders, yeast cell walls, or antioxidant additives are the most widely used products for mycotoxin elimination to reduce their impact. Although conventional methods are constantly improving, current research trends are looking for innovative solutions. Nanotechnology approaches seem to be a promising, effective, and low-cost way to minimize the health effects of mycotoxins. This review aims to shed light on the critical knowledge gap in mycotoxin elimination by nanotechnology. There are three main strategies: mold inhibition, mycotoxin adsorption, and reducing the toxic effect via nanoparticles. One of the most promising methods is the use of carbon-based nanomaterials. Graphene has been shown to have a huge surface and high binding capacity for mycotoxins. Attention has also been drawn to polymeric nanoparticles; they could substitute adsorbents or enclose any substance, which would improve the health status of the organism. In light of these findings, this review gives new insights into possible future research that might overcome challenges associated with nanotechnology utilization for mycotoxin elimination from agricultural products.

Three kinds of lateral flow immunochromatographic assays based on the use of nanoparticle labels for fluorometric determination of zearalenone

Colloidal gold, quantum dots and polystyrene microspheres were used as labels in three kinds of lateral flow immunochromatographic assays (ICAs) for the detection of zearalenone (ZEN) in cereal samples. The assays allow ZEN to be quantified within 20 min. The LODs are 10 μg·L^-1 of ZEN for the colloidal gold-based ICA, and 1 μg·L^-1 for both the quantum dot and polystyrene microsphere based ICAs. The respective data are 60 μg·kg^-1, 6 μg·kg^-1 and 6 μg·kg^-1, respectively, for spiked samples and cereals. Only minor cross-sensitivity occurred between ZEN and fusarium toxins, and no cross-sensitivity if found for aflatoxin B₁, T-2 mycotoxin, ochratoxin A, deoxynivalenol, and fumonisin B₁. LODs of the three assays are lower than the maximum limits of ZEN set by most standardization agencies. Graphical abstract Schematic presentation of three lateral flow immunochromatographic assays (ICAs) based on the use of (a) colloidal gold (CG), (b) fluorescent quantum dots (QD), and