Rapid surface plasmon resonance immunoassay for the determination of deoxynivalenol in wheat, wheat products, and maize-based baby food

A multiplex microarray lateral flow immunoassay device for simultaneous determination of five mycotoxins in rice

Co-occurrence of multiple mycotoxins is a growing global food safety concern due to their harmful effects on humans and animals. This study developed an eco-friendly sample preparation method and an innovative multiplex microarray-based lateral flow immunoassay, using a novel portable reader for on-site simultaneous determination of five regulated mycotoxins-aflatoxin B1, T-2 toxin, zearalenone, deoxynivalenol, and fumonisin B1 in rice. The eco-friendly and ultrafast extraction procedure utilizes a bio-based solvent. Principally, the microarray signals generated through a novel luminescent organic dye were captured to quantify mycotoxin levels in samples using a portable reader installed with a user-friendly interface. The assay demonstrates accurate detection and quantification of these mycotoxins, with recoveries ranging from 77% to 127%. Detection limits ranged from 0.56 to 1.89 μg/kg, which were well below their regulatory limits, with a relative standard deviation below 25%. This analytical system provides an on-site method for detecting multiple mycotoxins in rice.

Multicolor Visual Detection of Deoxynivalenol in Grain Based on Magnetic Immunoassay and Enzymatic Etching of Plasmonic Gold Nanobipyramids

In this study, a multicolor visual method based on a magnetic immunoassay and enzyme-induced gold nanobipyramids (Au NBPs) etching was developed for deoxynivalenol (DON) detection. The magnetic beads modified with high affinity DON monoclonal antibodies were used as a carrier for target enrichment and signal transformation and the Au NBPs with excellent plasmonic optical properties were served as enzymatic etching substrates. The oxidation state TMB, which was generated through catalysis of horseradish peroxidase (HRP), induced the etching of plasmonic Au NBPs, resulting in the longitudinal peak blue-shift of local surface plasmon resonance (LSPR). Correspondingly, Au NBPs with various aspect ratios displayed a variety of individual colors which were visualized by the naked eye. The LSPR peak shift was linearly related to the DON concentration in the range of 0~2000 ng/mL and the detection limit was 57.93 ng/mL. The recovery for naturally contaminated wheat and maize at different concentrations ranged from 93.7% to 105.7% with a good relative standard deviation below 11.8%. Through observing the color change in Au NBPs, samples with overproof DON could be screened preliminarily by the naked eye. The proposed method has the potential to be applied in on-site rapid screening of mycotoxins in grain. In addition, the current multicolor visual method only used for the simultaneous detection of multiple mycotoxins is in urgent need of a breakthrough to overcome the limitation of single mycotoxin detection.

Rapid, Sensitive On-Site Detection of Deoxynivalenol in Cereals Using Portable and Reusable Evanescent Wave Optofluidic Immunosensor

This paper develops an improved portable and reusable evanescent wave optofluidic immunosensor (OIP-v2) for rapid and sensitive on-site determination of deoxynivalenol (DON), one of the most frequently detected mycotoxins mainly produced by Fusarium species. Using the bifunctional reagent N,N'-Disuccinimidyl carbonate, deoxynivalenol-bovine-serum-albumin (DON-BSA) were covalently modified onto a bio-probe surface as biorecognition elements, whose robustness allowed it to perform multiple detections without significant activity loss. An indirect competitive immunoassay strategy was applied for DON detection. Under optimal conditions, the limit of detection of 0.11 μg/L and the linear dynamic detection range of 0.43 to 36.61 μg/L was obtained when the concentration of the Cy5.5-anti-DON antibody was 0.25 μg/mL. The OIP-v2 was also applied to detect DON in various cereals, and the recoveries ranged from 81% to 127%. The correlation between OIP-v2 and enzyme-linked immunosorbent assay (ELISA) through the simultaneous detection of maize-positive samples was in good agreement (R2 = 0.9891).

Fast Deoxynivalenol Determination in Cereals Using a White Light Reflectance Spectroscopy Immunosensor

Deoxynivalenol (DON) is a mycotoxin produced by certain Fusarium species and found in a high percentage of wheat and maize grains cultured worldwide. Although not so toxic as other mycotoxins, it exhibits both chronic and acute toxicity, and therefore methods for its fast and accurate on-site determination are highly desirable. In the current work, we employ an optical immunosensor based on White Light Reflectance Spectroscopy (WLRS) for the fast and sensitive immunochemical label-free determination of DON in wheat and maize samples. The assay is completed in 12 min and has a quantification limit of 2.5 ng/mL in buffer corresponding to 125 μg/kg in whole grain which is lower than the maximum allowable concentrations set by the regulatory authorities for grains intended for human consumption. Several extraction protocols have been compared, and the highest recovery (>90%) was achieved employing distilled water. In addition, identical calibration curves were received in buffer and wheat/maize extraction matrix providing the ability to analyze the grain samples using calibrators in buffer. Recoveries of DON from spiked wheat and maize grain samples ranged from 92.0(±4.0) to 105(±4.0)%. The analytical performance of the WLRS immunosensor, combined with the short analysis time and instrument portability, supports its potential for on-site determinations.

Current trends in rapid tests for mycotoxins

There are an ample number of commercial testing kits available for mycotoxin analysis on the market today, including enzyme-linked immunosorbent assays, membrane-based immunoassays, fluorescence polarisation immunoassays and fluorometric assays. It can be observed from the literature that not only are developments and improvements ongoing for these assays but there are also novel assays being developed using biosensor technology. This review focuses on both the currently available methods and recent innovative methods for mycotoxin testing. Furthermore, it highlights trends that are influencing assay developments such as multiplexing capabilities and rapid on-site analysis, indicating the possible detection methods that will shape the future market.

A rapid Raman detection of deoxynivalenol in agricultural products

Mycotoxin results in financial damage and considerable safety risks. In this paper, the possibility of portable Raman system-based surface-enhanced Raman scattering (SERS) for a rapid detection of deoxynivalenol (DON) a mycotoxin in cereals was investigated. Under an optimized condition, SERS analysis for pure DON solution has a wide dynamic concentration range from 10^-7M to 10^-2M with the limit of detection (LOD) down to 100nM. Density functional theory (DFT) analysis at the level of B3LYP/6-311++G(d, p) was also preformed for vibrational assignment. For practical application, the LOD of the proposed Raman method for both DON-contaminated corns and kidney beans were validated as 10^-6M and the LOD for DON-contaminated oats was 10^-4M. As a perspective, the SERS-based technology could be developed into an alternatively promising assay for on-field detection of DON residues at various cereals due to it high sensitivity and selectivity.

Advances in Biosensors, Chemosensors and Assays for the Determination of Fusarium Mycotoxins

The contaminations of Fusarium mycotoxins in grains and related products, and the exposure in human body are considerable concerns in food safety and human health worldwide. The common Fusarium mycotoxins include fumonisins, T-2 toxin, deoxynivalenol and zearalenone. For this reason, simple, fast and sensitive analytical techniques are particularly important for the screening and determination of Fusarium mycotoxins. In this review, we outlined the related advances in biosensors, chemosensors and assays based on the classical and novel recognition elements such as antibodies, aptamers and molecularly imprinted polymers. Application to food/feed commodities, limit and time of detection were also discussed.

Rapid surface plasmon resonance immunoassays for the determination of mycotoxins in cereals and cereal-based food products

In recent times surface plasmon resonance has demonstrated its applicability to the detection of a wide range of contaminants in food and feed including mycotoxins in cereals and cereal-based food products. Commercially available, laboratory-based systems have exploited high affinity polyclonal, monoclonal and recombinant antibodies and robust sensing surfaces to provide rapid, accurate and sensitive means of determining these toxins. In addition many custom-built, prototype devices have shown a great deal of potential for this particular application and have included the combination of surface plasmon resonance with enzyme-derivatised sensors, molecularly imprinted polymers, fluorescence spectroscopy and the use of gold nanoparticles for signal enhancement. Of note is the lack of available devices that allow the detection of multiple mycotoxins simultaneously and portable devices that could be used in the field, therefore future research and development should focus on these areas to deliver cost-effective miniaturised devices with multiplexing capabilities.

Using commercial immunoassay kits for mycotoxins: ‘joys and sorrows’?

Rapid test methods are widely used for measuring mycotoxins in a variety of matrices. This review presents an overview of the current commercially available immunoassay rapid test formats. Enzyme linked immune-sorbent assay (ELISA), lateral flow tests, flow through immunoassay, fluorescent polarisation immunoassay, and immunoaffinity columns coupled with fluorometric assay are common formats in the current market. The two existing evaluation programs for commercial testing kits by United State Department of Agricultural Grain Inspection, Packers & Stockyards Administration (USDA-GIPSA) and AOAC Research Institute are introduced. The strengths and weaknesses of these test kits are discussed with regard to the application scope, variance, specificity and cross reactivity, accuracy and precision, and measurement range. Generally speaking, the current commercially available testing kits meet research and industrial needs as ‘fit-for-purpose’. Furthermore, quality assurance concerns and future perspectives are elaborated for broader application of commercial test kits in research, industry and regulatory applications. It is expected that new commercial kits based on advanced technologies such as electrochemical affinity biosensors, molecularly imprinted polymers, surface plasmon resonance, fluorescence resonance energy transfer, aptamer-based biosensors and dynamic light scattering might be available to users in the future. Meanwhile, harmonisation of testing kit evaluation, incorporation of more quality assurance into the testing kit utilisation scheme, and a larger variety of kits available at lower cost will expand the usage of testing kits for food safety testing worldwide.

Cross-reactivity of rapid immunochemical methods for mycotoxins detection towards metabolites and masked mycotoxins: the current state of knowledge

The cross-reactivity of antibodies employed within immunochemistry-based analytical methods may lead to overestimation of the results. Under certain conditions, specifically when controlling mycotoxin maximum limits serious problems can be encountered. Not only the structurally related mycotoxins, such as their masked (conjugated) forms, but also the unidentified matrix components are responsible for concentration overestimation of respective target analytes. The cross-reactivity phenomenon may also pose a risk of miss-interpretation of the proficiency tests results, when the assigned value becomes influenced by over-estimated results reported by users of immunochemical tests. In this paper, the current state of the knowledge on trueness problems associated with the rapid screening immunochemical methods have been reviewed. Special attention is focused on discussion of cross-reactivity in the ELISA tests, because this rapid test dominates the routine screening practice. However, the cross-reactions reported in lateral flow test strips, fluorescence polarisation immunoassay, or immunosensors have also been addressed.

Simultaneous screening for T-2/HT-2 and deoxynivalenol in cereals using a surface plasmon resonance immunoassay

This manuscript describes a rapid surface plasmon resonance (SPR) immunoassay for the simultaneous determination of the sum of T-2/HT-2 toxins (T-2/HT-2) and deoxynivalenol (DON), in cereals and cereal-based products. The assay is based on an inhibition format employing a monoclonal antibody raised against HT-2 with cross reactivity to T-2 and a polyclonal antibody raised against DON, thereby enabling the detection of the three trichothecene mycotoxins (types A and B). The surface chemistry involved an equal mixture of HT-2 and DON covalently coupled onto a high capacity COOH5 sensor chip. Using the specified antibodies and a mixed toxin sensor surface, and running calibration curves (HT-2 and DON) and samples in parallel it has been proven that it is feasible to develop a multiplex assay on this SPR platform. In-house validation has shown limits of detection of 12, 1 and 29 μg/kg for DON and 31, 47 and 36 μg/kg for HT-2 in wheat, breakfast cereal and maize-based baby food, respectively. Both intra-assay and inter-assay precision were calculated using fortified DON and HT-2 samples. Durum wheat, wheatbased breakfast cereal and maize-based baby food were spiked at various concentration levels and the coefficients of variation calculated ranged from 1.1% to 9.9% for DON and from 1.4% to 11.3% for HT-2. A high correlation was observed between the screening assay and confirmatory mass spectrometry.

Biosensors for the analysis of microbiological and chemical contaminants in food

Increases in food production and the ever-present threat of food contamination from microbiological and chemical sources have led the food industry and regulators to pursue rapid, inexpensive methods of analysis to safeguard the health and safety of the consumer. Although sophisticated techniques such as chromatography and spectrometry provide more accurate and conclusive results, screening tests allow a much higher throughput of samples at a lower cost and with less operator training, so larger numbers of samples can be analysed. Biosensors combine a biological recognition element (enzyme, antibody, receptor) with a transducer to produce a measurable signal proportional to the extent of interaction between the recognition element and the analyte. The different uses of the biosensing instrumentation available today are extremely varied, with food analysis as an emerging and growing application. The advantages offered by biosensors over other screening methods such as radioimmunoassay, enzyme-linked immunosorbent assay, fluorescence immunoassay and luminescence immunoassay, with respect to food analysis, include automation, improved reproducibility, speed of analysis and real-time analysis. This article will provide a brief footing in history before reviewing the latest developments in biosensor applications for analysis of food contaminants (January 2007 to December 2010), focusing on the detection of pathogens, toxins, pesticides and veterinary drug residues by biosensors, with emphasis on articles showing data in food matrices. The main areas of development common to these groups of contaminants include multiplexing, the ability to simultaneously analyse a sample for more than one contaminant and portability. Biosensors currently have an important role in food safety; further advances in the technology, reagents and sample handling will surely reinforce this position.

Imaging surface plasmon resonance for multiplex microassay sensing of mycotoxins

A prototype imaging surface plasmon resonance-based multiplex microimmunoassay for mycotoxins is described. A microarray of mycotoxin-protein conjugates was fabricated using a continuous flow microspotter device. A competitive inhibition immunoassay format was developed for the simultaneous detection of deoxynivalenol (DON) and zearalenone (ZEN), using a single sensor chip. Initial in-house validation showed limits of detection of 21 and 17 ng/mL for DON and 16 and 10 ng/mL for ZEN in extracts, which corresponds to 84 and 68 μg/kg for DON and 64 and 40 μg/kg for ZEN in maize and wheat samples, respectively. Finally, the results were critically compared with data obtained from liquid chromatography-mass spectrometry confirmatory analysis method and found to be in good agreement. The described multiplex immunoassay for the rapid screening of several mycotoxins meets European Union regulatory limits and represents a robust platform for mycotoxin analysis in food and feed samples.

A comparative study of qualitative immunochemical screening assays for the combined measurement of T-2/HT-2 in cereals and cereal-based products

Many different immunochemical platforms exist for the screening of naturally occurring contaminants in food from the low cost enzyme linked immunosorbent assays (ELISA) to the expensive instruments such as optical biosensors based on the phenomenon of surface plasmon resonance (SPR). The primary aim of this study was to evaluate and compare a number of these platforms to assess their accuracy and precision when applied to naturally contaminated samples containing HT-2/T-2 mycotoxins. Other important factors considered were the speed of analysis, ease of use (sample preparation techniques and use of the equipment) and ultimately the cost implications. The three screening procedures compared included an SPR biosensor assay, a commercially available ELISA and an enzymelinked immunomagnetic electrochemical array (ELIME array). The qualitative data for all methods demonstrated very good overall agreements with each other, however on comparison with mass spectrometry confirmatory results, the ELISA and SPR assay performed slightly better than the ELIME array, exhibiting an overall agreement of 95.8% compared to 91.7%. Currently, SPR is more costly than the other two platforms and can only be used in the laboratory whereas in theory both the ELISA and ELIME array are portable and can be used in the field, but ultimately this is dependent on the sample preparation techniques employed. Sample preparative techniques varied for all methods evaluated, the ELISA was the most simple to perform followed by that of the SPR method. The ELIME array involved an additional clean-up step thereby increasing both the time and cost of analysis. Therefore in the current format, field use would not be an option for the ELIME array. In relation to speed of analysis, the ELISA outperformed the other methods.