An immunochemical test for rapid screening of zearalenone and T-2 toxin

Direct and Competitive Optical Grating Immunosensors for Determination of Fusarium Mycotoxin Zearalenone

Novel optical waveguide lightmode spectroscopy (OWLS)-based immunosensor formats were developed for label-free detection of Fusarium mycotoxin zearalenone (ZON). To achieve low limits of detection (LODs), both immobilised antibody-based (direct) and immobilised antigen-based (competitive) assay setups were applied. Immunoreagents were immobilised on epoxy-, amino-, and carboxyl-functionalised sensor surfaces, and by optimising the immobilisation methods, standard sigmoid curves were obtained in both sensor formats. An outstanding LOD of 0.002 pg/mL was obtained for ZON in the competitive immunosensor setup with a dynamic detection range between 0.01 and 1 pg/mL ZON concentrations, depending on the covalent immobilisation method applied. This corresponds to a five orders of magnitude improvement in detectability of ZON relative to the previously developed enzyme-linked immonosorbent assay (ELISA) method. The selectivity of the immunosensor for ZON was demonstrated with structural analogues (α-zearalenol, α-zearalanol, and β-zearalanol) and structurally unrelated mycotoxins. The method was found to be applicable in maize extract using acetonitrile as the organic solvent, upon a dilution rate of 1:10,000 in buffer. Thus, the OWLS immunosensor method developed appears to be suitable for the quantitative determination of ZON in aqueous medium. The new technique can widen the range of sensoric detection methods of ZON for surveys in food and environmental safety assessment.

Immunoaffinity Extraction and Alternative Approaches for the Analysis of Toxins in Environmental, Food or Biological Matrices

The evolution of instrumentation in terms of separation and detection allowed a real improvement of the sensitivity and analysis time. However, the analysis of ultra-traces of toxins in complex samples requires often a step of purification and even preconcentration before their chromatographic analysis. Therefore, immunoaffinity sorbents based on specific antibodies thus providing a molecular recognition mechanism appear as powerful tools for the selective extraction of a target molecule and its structural analogs to obtain more reliable and sensitive quantitative analysis in environmental, food or biological matrices. This review focuses on immunosorbents that have proven their efficiency in selectively extracting various types of toxins of various sizes (from small mycotoxins to large proteins) and physicochemical properties. Immunosorbents are now commercially available, and their use has been validated for numerous applications. The wide variety of samples to be analyzed, as well as extraction conditions and their impact on extraction yields, is discussed. In addition, their potential for purification and thus suppression of matrix effects, responsible for quantification problems especially in mass spectrometry, is presented. Due to their similar properties, molecularly imprinted polymers and aptamer-based sorbents that appear to be an interesting alternative to antibodies are also briefly addressed by comparing their potential with that of immunosorbents.

Electrochemical Immuno- and Aptasensors for Mycotoxin Determination

Modern analysis of food and feed is mostly focused on development of fast and reliable portable devices intended for field applications. In this review, electrochemical biosensors based on immunological reactions and aptamers are considered in the determination of mycotoxins as one of most common contaminants able to negatively affect human health. The characteristics of biosensors are considered from the point of view of general principles of bioreceptor implementation and signal transduction providing sub-nanomolar detection limits of mycotoxins. Moreover, the modern trends of bioreceptor selection and modification are discussed as well as future trends of biosensor development for mycotoxin determination are considered.

Gold nanoparticles of different shape for bicolor lateral flow test

Spherical gold nanoparticles are the most commonly used marker in lateral flow assays. However, the widespread practice of using identical coloration for the test and control zones of test strips can lead to erroneous interpretations of the assay's results. We propose an immunochromatographic test strip with lines of different colors. For this purpose, gold nanoparticles of different shapes were used, namely blue nanoflowers in the test zone and red gold nanospheres in the control zone. A detailed synthesis procedure for nanoparticles and their conjugates is considered and design parameters for optimal results are described. For the first time, nanoparticles of different shapes have been combined in the test strip with indirect labeling of specific antibodies (via their interaction with labeled secondary antibodies). Using the T-2 toxin (T2T) as an example, an instrumental detection limit of 30 pg/ml and a working range 0.06-0.9 ng/mL were achieved in an analysis of water-organic corn extracts.

Microarray-Based Immunoassay for Parallel Quantification of Multiple Mycotoxins in Oat

Because multianalyte methods are highly desirable in order to keep analysis time and costs low, the biosensor development increasingly focuses on parallel analysis of several mycotoxins. Here, we describe an indirect competitive immunoassay on regenerable, reusable glass microchips for the parallel determination of aflatoxins, ochratoxin A, deoxynivalenol, and fumonisin B1 in oat extracts, using a fully automated flow-through device with chemiluminescence readout.

Multiplex Lateral Flow Immunoassays Based on Amorphous Carbon Nanoparticles for Detecting Three Fusarium Mycotoxins in Maize

The detecting labels used for lateral flow immunoassays (LFAs) have been traditionally gold nanoparticles (GNPs) and, more recently, luminescent nanoparticles, such as quantum dots (QDs). However, these labels have low sensitivity and are costly, in particular, for trace detection of mycotoxins in cereals. Here, we provided a simple preparation procedure for amorphous carbon nanoparticles (ACNPs) and described multiplex LFAs employing ACNPs as labels (ACNP-LFAs) for detecting three Fusarium mycotoxins. The analytical performance of ACNPs in LFA was compared to GNPs and QDs using the same immunoreagents, except for the labels, allowing for their analytical characteristics to be objectively compared. The visual limit of detection for ACNP-LFAs in buffer was 8-fold better than GNPs and 2-fold better than QDs. Under optimized conditions, the quantitative limit of detection of ACNP-LFAs in maize was as low as 20 μg/kg for deoxynivalenol, 13 μg/kg for T-2 toxin, and 1 μg/kg for zearalenone. These measurements were much lower than the action level of these mycotoxins in maize. The accuracy and precision of the ACNP-LFAs were evaluated by analysis of spiked and incurred maize samples with recoveries of 84.6-109% and coefficients of variation below 13%. The results of ACNP-LFAs using naturally incurred maize samples showed good agreement with results from high-performance liquid chromatography-tandem mass spectrometry, indicating that ACNPs were more sensitive labels than and a promising alternative to GNPs used in LFAs for detecting mycotoxins in cereals.

Sensitive Flow-through Immunoassay for Rapid Multiplex Determination of Cereal-borne Mycotoxins in Feed and Feed Ingredients

An easy-to-operate membrane-based flow-through test for multiplex screening of four mycotoxins (zearalenone, deoxynivalenol, aflatoxin B₁, and ochratoxin A) in a variety of cereal-based feed ingredients and compound feeds, such as wheat, barley, soybean, wheat bran, rice, rice bran, maize, rapeseed meal, and sunflower meal, and various types of complete feed (duckling feed, swine feed, broiler feed, piglet feed) was developed and validated. First, the antibodies were evaluated by enzyme-linked immunosorbent assay and then employed in the membrane rapid test. The cutoff levels for zearalenone, deoxynivalenol, aflatoxin B₁, and ochratoxin A were 50, 200, 1, and 10 μg/kg, respectively, based on European regulations and consumers' requirements. As sample pretreatment, consecutive steps of extraction, dilution, solid-phase extraction by addition of C18 sorbent, and final filtration of supernatant were followed. Both the sample preparation and the analysis procedure were simple, cost-effective, and easy to perform on-site in a nonlaboratory environment. The impact of sample processing on the result of the experiment was investigated supported by experimental design. The validation procedure was performed on the basis of Commission Regulation 2006/401/EC. The numbers of false-positive and false-negative outcomes were <5%, going along with the Commission Decision 2002/657/EC. Liquid chromatography-tandem mass spectrometry was performed as a confirmatory technique.

A universal multi-wavelength fluorescence polarization immunoassay for multiplexed detection of mycotoxins in maize

Multi-analyte immunoassays have attracted increasing attention due to their short assay times, low sample consumption, and reduced detection costs per assay. In this work, we describe a homologous and high-throughput multi-wavelength fluorescence polarization immunoassay (MWFPIA) for the multiplexed detection of mycotoxins. Three typical Fusarium mycotoxins, deoxynivalenol (DON), T-2 toxin and fumonisin B1 (FB1), were labeled with different dyes. Tracers and specific monoclonal antibodies (mAbs) were employed in the MWFPIA to simultaneously detect the three mycotoxins. Under optimal conditions, the limits of detection using MWFPIA were 242.0 μg kg(-1) for DON, 17.8 μg kg(-1) for T-2 toxin and 331.5 μg kg(-1) for FB1, providing sufficient sensitivity to meet the action levels of these three contaminants in maize as set by the European Union. The use of a methanol/water (2:3, v/v) mixture for sample pretreatment allowed recoveries ranging from 76.5-106.3%, with coefficients of variation less than 21.7%. The total time of analysis, including sample preparation, was less than 30 min. Twenty naturally contaminated maize samples were tested using MWFPIA and HPLC-MS/MS, with correlation coefficients (R(2)) of 0.97 for DON and 0.99 for FB1. By changing the targets of interest, homologous MWFPIA, a method with high sensitivity, a simple procedure and a short analysis time, can easily be extended to other chemical contaminants. Thus, MWFPIA represents a versatile strategy for food safety analysis.

Development and Application of a Gel-Based Immunoassay for the Rapid Screening of Salbutamol and Ractopamine Residues in Pork

Salbutamol (SAL) and ractopamine (RAC) have been illegally used to promote protein synthesis and to increase the feed conversion rate in livestock. However, the residues of SAL and RAC could cause potential hazards for human health. The Ministry of Agriculture of China banned the use of SAL and RAC as growth promoters. In this paper, we provide detailed information on developing a rapid and sensitive gel-based immunoassay for on-site screening of SAL and RAC residues in pork. The detection time was shortened to 20 min. The limits of detection were 0.5 μg/kg for both SAL and RAC by visual detection, whereas the quantitative gel-based immunoassay enabled the detection of SAL (0.051 μg/kg) and RAC (0.020 μg/kg) in spiked pork samples. The gel-based immunoassay showed promise as a multiplexed immunoassay for on-site surveilling of SAL and RAC residues in pork.

Use of cloneable peptide-MBP fusion protein as a mimetic coating antigen in the standardized immunoassay for mycotoxin ochratoxin A

The quality of mycotoxin conjugates is essential to the development of reliability of immunoassays for mycotoxins. However, conventional mycotoxin conjugates are usually synthesized by chemical methods, which are harmful to the environment and yield unwanted cross-reactions. In this study, using ochratoxin A (OTA) as a model system, a selected OTA mimotope (phage-displayed peptide) that specifically binds to anti-OTA antibody was expressed as soluble and monovalent fusions to maltose binding protein (MBP). These prepared fusion proteins can serve as a mimetic coating antigen in both a quantitative chemiluminescent enzyme-linked immunoassay (CLEIA) and a qualitative dot immunoassay for OTA. One of the prepared mimetic coating antigen (L12-206-MBP)-based CLEIAs exhibited a half-inhibition concentration (IC50) of 0.82 ng/mL and a working range of 0.30-2.17 ng/mL, which resemble those of the conventional OTA-OVA conjugate-based immunoassay. The dot immunoassay developed with both the OTA-OVA conjugate and the mimetics showed identical visual cutoff values of 5 ng/mL. The mimetic coating antigen proposed here is an OTA-free product and can be prepared reproducibly as a homogeneous product and facilitates standardization of immunoassays for the mycotoxin OTA.

Development and application of an immunoaffinity column enzyme immunoassay for mycotoxin zearalenone in complicated samples

The zearalenone (ZEA) monoclonal antibody (mAb) 2D3, one of the highest sensitivity antibodies, was developed. Based on this mAb, it was established of an immunoaffinity column (IAC) coupled with an indirect competitive enzyme-linked immunosorbent assay (icELISA). After optimization, the icELISA allowed an IC₅₀ against ZEA of 0.02 µg L⁻¹. The mAb 2D3 exhibited a high recognition of ZEA (100%) and β-zearalenol (β-ZOL, 88.2%). Its cross-reactivity with α-zearalenol (α-ZOL) and β-zearalanol (β-ZAL) were found to be 4.4% and 4.6%, respectively. The IAC-icELISA method was employed to analyze ZEA contamination in food samples, compared with high-performance liquid chromatography (HPLC). The spiked assay for ZEA demonstrated the considerable recoveries for IAC-icELISA (83–93%) and HPLC (94–108%) methods. Results showed that the mAb 2D3 and IAC-icELISA method posed potential applications in sensitively determination of ZEA in maize.

Automated regenerable microarray-based immunoassay for rapid parallel quantification of mycotoxins in cereals

An automated flow-through multi-mycotoxin immunoassay using the stand-alone Munich Chip Reader 3 platform and reusable biochips was developed and evaluated. This technology combines a unique microarray, prepared by covalent immobilization of target analytes or derivatives on diamino-poly(ethylene glycol) functionalized glass slides, with a dedicated chemiluminescence readout by a CCD camera. In a first stage, we aimed for the parallel detection of aflatoxins, ochratoxin A, deoxynivalenol, and fumonisins in cereal samples in a competitive indirect immunoassay format. The method combines sample extraction with methanol/water (80:20, v/v), extract filtration and dilution, and immunodetection using horseradish peroxidase-labeled anti-mouse IgG antibodies. The total analysis time, including extraction, extract dilution, measurement, and surface regeneration, was 19 min. The prepared microarray chip was reusable for at least 50 times. Oat extract revealed itself as a representative sample matrix for preparation of mycotoxin standards and determination of different types of cereals such as oat, wheat, rye, and maize polenta at relevant concentrations according to the European Commission regulation. The recovery rates of fortified samples in different matrices, with 55-80 and 58-79%, were lower for the better water-soluble fumonisin B1 and deoxynivalenol and with 127-132 and 82-120% higher for the more unpolar aflatoxins and ochratoxin A, respectively. Finally, the results of wheat samples which were naturally contaminated with deoxynivalenol were critically compared in an interlaboratory comparison with data obtained from microtiter plate ELISA, aokinmycontrol® method, and liquid chromatography-mass spectrometry and found to be in good agreement.

Rapid Determination of Fumonisin B1 in Food Samples by a Clean-Up Tandem Immunoassay Column

An immunochemistry-based assay for non-instrumental simultaneous detection of fumonisins in food was developed. The method was based upon the direct competitive immuno-reaction and the horse radish peroxidase enzymatic reaction. The assay was developed to show a visual detection result, according to a yes/no response to the LOD of fumonisins. The limit of detection (LOD) was 40 μg L-1. The assay could be accomplished within 15 min in all and 4 min for chromogenic substrate application. The fumonisin contaminations in different kinds of food were analyzed by the proposed method and the results were confirmed by ELISA. Avoiding time-consuming reaction steps and complicated pre-treatment procedures, this assay was demonstrated as a promising tool for on-site sample detections.

Developments in mycotoxin analysis: an update for 2009-2010

This review highlights developments in mycotoxin analysis and sampling over a period between mid-2009 and mid-2010. It covers the major mycotoxins aflatoxins, Alternaria toxins, ergot alkaloids, fumonisins, ochratoxin, patulin, trichothecenes, and zearalenone. New and improved methods for mycotoxins continue to be published. Immunological-based method developments continue to be of wide interest in a broad range of formats. Multimycotoxin determination by LC-MS/MS is now being targeted at the specific ranges of mycotoxins and matrices of interest or concern to the individual laboratory. Although falling outside the main emphasis of the review, some aspects of natural occurrence have been mentioned, especially if linked to novel method developments.