Development of a colloidal gold-based lateral-flow immunoassay for the rapid simultaneous detection of zearalenone and deoxynivalenol

Flap Endonuclease-Induced Steric Hindrance Change Enables the Construction of Multiplex and Versatile Lateral Flow Strips for DNA Detection

A lateral flow strip (LFS) is an ideal tool for point-of-care testing (POCT), but traditional LFSs cannot be used for multiplex detection. Herein, a multiplex and versatile LFS based on flap endonuclease 1 (FEN1)-induced steric hindrance change (FISH-LFS) is proposed. In this method, multiplex PCR coupled with cascade invasive reactions was employed to yield single-stranded flaps, which were target-specific but independent of target sequences. Then, the amplicons were applied for FISH-LFS, and the single-stranded flaps would be efficiently captured by the complementary LFS-probes at different test lines. As flaps were cleaved from the specially designed hairpin probes, competition among flaps and hairpin probes would occur in capturing the probes at test lines. We enabled the hairpin probes to flow through the test lines while the flaps to stay at the test lines by making use of the difference in steric hindrance between hairpin probes and flaps. The assay is able to detect as low as two copies of blood pathogens (HBV, HCV, and HIV), to pick up as low as 0.1% mutants from wild-type gDNA, and to genotype 200 copies of SARS-CoV-2 variants α and β within 75 min at a conventional PCR engine. As the method is free of dye, a portable PCR engine could be used for a cost-effective multiplex detection on site. Results using an ultrafast mobile PCR system for FISH-LFS showed that as fast as 30 min was achieved for detecting three pathogens (HBV, HCV, and HIV) in blood, very suitable for POCT of pathogen screening. The method is convenient in operation, simple in instrumentation, specific in genotyping, and very easy in setting up multiplex POCT assays.

The evolution of multiplex detection of mycotoxins using immunoassay platform technologies

Mycotoxins present serious threats not only for public health, but also for the economy and environment. The problems become more complex and serious due to co-contamination of multiple hazardous mycotoxins in commodities and environment. To mitigate against this issue, accurate, affordable, and rapid multiplex detection methods are required. This review presents an overview of emerging rapid immuno-based multiplex methods capable of detecting mycotoxins present in agricultural products and feed ingredients published within the past five years. The scientific principles, advantages, disadvantages, and assay performance of these rapid multiplex immunoassays, including lateral flow, fluorescence polarization, chemiluminescence, surface plasmon resonance, surface enhanced Raman scattering, electrochemical sensor, and nanoarray are discussed. From the recent literature landscape, it is predicted that the future trend of the detection methods for multiple mycotoxins will rely on the advance of various sensor technologies, a variety of enhancing and reporting signals based on nanomaterials, rapid and effective sample preparation, and capacity for quantitative analysis.

Simple manipulation of enzyme-linked immunosorbent assay (ELISA) using an automated microfluidic interface

Among lateral flow immunoassay (LFIA) platforms, enzyme-based LFIAs provide signal amplification to improve sensitivity. However, most enzyme-based LFIAs require multiple timed steps, complicating their utility in point-of-care testing (POCT). Here, we report a microfluidic interface for LFIAs that automates sample, buffer, and reagent addition, greatly simplifying operation while achieving the high analytical stringency associated with more complex assays. The microfluidic interface also maintains the low cost and small footprint of standard LFIAs. The platform is fabricated from a combination of polyester film, double-sided adhesive tape, and nitrocellulose, and fits in the palm of your hand. All reagents are dried on the nitrocellulose to facilitate sequential reagent delivery, and the sample is used as the wash buffer to minimize steps. After the sample addition, a user simply waits 15 min for a colorimetric result. This manuscript discusses the development and optimization of the channel geometry to achieve a simple step enzyme amplified immunoassay. As a proof-of-concept target, we selected lipoarabinomannan (LAM), a WHO identified urinary biomarker of active tuberculosis, to demonstrate the device feasibility and reliability. The results revealed that the device successfully detected LAM in phosphate buffer (PBS) as well as spiked urine samples within 15 min after sample loading. The minimum concentration of color change was achieved at 25 ng mL-1.

Monoclonal Antibodies Application in Lateral Flow Immunochromatographic Assays for Drugs of Abuse Detection

Lateral flow assays (lateral flow immunoassays and nucleic acid lateral flow assays) have experienced a great boom in a wide variety of early diagnostic and screening applications. As opposed to conventional examinations (High Performance Liquid Chromatography, Polymerase Chain Reaction, Gas chromatography-Mass Spectrometry, etc.), they obtain the results of a sample's analysis within a short period. In resource-limited areas, these tests must be simple, reliable, and inexpensive. In this review, we outline the production process of antibodies against drugs of abuse (such as heroin, amphetamine, benzodiazepines, cannabis, etc.), used in lateral flow immunoassays as revelation or detection molecules, with a focus on the components, the principles, the formats, and the mechanisms of reaction of these assays. Further, we report the monoclonal antibody advantages over the polyclonal ones used against drugs of abuse. The perspective on aptamer use for lateral flow assay development was also discussed as a possible alternative to antibodies in view of improving the limit of detection, sensitivity, and specificity of lateral flow assays.

Development and perspectives of rapid detection technology in food and environment

Food safety become a hot issue currently with globalization of food trade and food supply chains. Chemical pollution, microbial contamination and adulteration in food have attracted more attention worldwide. Contamination with antibiotics, estrogens and heavy metals in water environment and soil environment have also turn into an enormous threat to food safety. Traditional small-scale, long-term detection technologies have been unable to meet the current needs. In the monitoring process, rapid, convenient, accurate analysis and detection technologies have become the future development trend. We critically synthesizing the current knowledge of various rapid detection technology, and briefly touched upon the problem which still exist in research process. The review showed that the application of novel materials promotes the development of rapid detection technology, high-throughput and portability would be popular study directions in the future. Of course, the ultimate aim of the research is how to industrialization these technologies and apply to the market.

Occurrence, Impact on Agriculture, Human Health, and Management Strategies of Zearalenone in Food and Feed: A Review

Mycotoxins represent an assorted range of secondary fungal metabolites that extensively occur in numerous food and feed ingredients at any stage during pre- and post-harvest conditions. Zearalenone (ZEN), a mycotoxin categorized as a xenoestrogen poses structural similarity with natural estrogens that enables its binding to the estrogen receptors leading to hormonal misbalance and numerous reproductive diseases. ZEN is mainly found in crops belonging to temperate regions, primarily in maize and other cereal crops that form an important part of various food and feed. Because of the significant adverse effects of ZEN on both human and animal, there is an alarming need for effective detection, mitigation, and management strategies to assure food and feed safety and security. The present review tends to provide an updated overview of the different sources, occurrence and biosynthetic mechanisms of ZEN in various food and feed. It also provides insight to its harmful effects on human health and agriculture along with its effective detection, management, and control strategies.

Detection of Mycotoxins in Food Using Surface-Enhanced Raman Spectroscopy: A Review

Mycotoxins are toxic metabolites produced by fungi that contaminate many important crops worldwide. Humans are commonly exposed to mycotoxins through the consumption of contaminated food products. Mycotoxin contamination is unpredictable and unavoidable; it occurs at any point in the food production system under favorable conditions, and they cannot be destroyed by common heat treatments, because of their high thermal stability. Early and fast detection plays an essential role in this unique challenge to monitor the presence of these compounds in the food chain. Surface-enhanced Raman spectroscopy (SERS) is an advanced spectroscopic technique that integrates Raman spectroscopic molecular fingerprinting and enhanced sensitivity based on nanotechnology to meet the requirement of sensitivity and selectivity, but that can also be performed in a cost-effective and straightforward manner. This Review focuses on the SERS methodologies applied to date for qualitative and quantitative analysis of mycotoxins based on a variety of SERS substrates, as well as our perspectives on current limitations and future trends for applying this technique to mycotoxin analyses.

Deep Learning on chromatographic data for Segmentation and Sensitive Analysis

Lateral flow immunoassay (LFIA) is one of the most common methods in point-of-care testing, which is widely applied in some conditions for various applications. Image segmentation is an increasingly popular experimental paradigm to efficiently test the target area in LFIA. However, due to process pollution, and problems related to the experimental operation and irregular structure of the background of the reaction, currently available tools cannot be used to extract correct signals from these images, which affects the accuracy of detection. Machine learning has significantly improved modern biochemical analysis by pushing the limits of traditional techniques for the recognition and processing of images. In this paper, the U-Net, a variant of the convolutional neural network (CNN) is used for the quantitative analysis of LFIA images for the accurate quantification of single- and multi-target images. By graying, binarizing, and labeling different concentrations of test strips, the target area of LFIA images containing the T-/C-lines is extracted and obtained. Then it provides updated trends and directions for the development of LFIA technology. Several indicators are introduced to evaluate the proposed U-Net structure to verify the feasibility and effectiveness of its image processing capability. When the trained U-Net model was used to process images, the peak signal-to-noise ratio was 22.4 dB, significantly higher than prevalent methods in the area that have reported only a 4 dB improvement in the quality of the graphics. The intersection-over-union between samples also increased to above 93%. Our results show that the proposed method has significant potential for detecting a segmented target in an LFIA area, especially weak positive signals and multichannel detection. With other modifications, this deep learning method can be applied as a powerful tool to study rapid detection devices, systems, and biological images.

Detection of ochratoxin A by quantum dots-based fluorescent immunochromatographic assay

Ochratoxin A (OTA) is a toxic metabolite produced mainly by Aspergillus and Penicillium species. A quantitative method was developed for the rapid, simple, and sensitive detection of OTA in corn by quantum dots-based fluorescent immunochromatographic assay (QDs-ICA). The CdSe/ZnS QDs-labelled anti-OTA monoclonal antibody (mAb) conjugates were designed as the fluorescent signal probe. The QDs-ICA included the designation of test line (T line) and control line (C line), which were sprayed with optimal concentrations of the OTA-OVA and staphylococcal protein-A (SPA), respectively. Under the optimal experimental conditions, the QDs-ICA exhibited excellent specificity and good accuracy and precision. For qualitative detection, the cut-off value for the T line of the visual detection method was 2.5 ng/mL. For quantitative detection, the linear regression equation of the standard curve was y = 0.366x + 0.514 with a reliable correlation coefficient (R² = 0.992). Moreover, the 50% inhibition value (IC₅₀) of the QDs-ICA was 0.91 ng/mL, the limit of detection (LOD) was 0.07 ng/mL, and the detection range was 0.05 to 10 ng/mL. In addition, the recovery rates ranged from 91.82 to 100.35% with a coefficient of variation (CV) below 3% for intra-assay, whereas the recovery rates for inter-assay changed from 94.29 to 104.62% with a CV below 10%. These results indicate that the QDs-ICA can serve as a potential large-scale preliminary device for rapid determination of OTA. Using CdSe/ZnS QDs as the fluorescent signal for quantum dots-based fluorescent immunochromatographic assay, the QDs-ICA provided a novel method for the rapid simultaneous qualitative and quantitative determination of OTA.

An immunochromatographic strip sensor for sildenafil and its analogues

In this study, a new hapten of sildenafil (Sild) was successfully synthesized and a sensitive monoclonal antibody (mAb) against Sild was produced based on this new hapten. The subclass of the mAb was IgG2a, and the half-maximal inhibitory concentration (IC50) of the mAb was 0.53 ng mL-1. Next, an immunochromatographic assay (ICA) was established for detecting Sild and its analogues in functional foods, where the visual detection limit (vLOD) and cut-off values were 0.5 and 20 μg kg-1, respectively. With the aid of a strip scan reader, the ICA can measure Sild with an LOD of 0.7 μg kg-1 and a line range of detection between 1.40 and 13.11 μg kg-1. The whole test process takes only 15 min. Therefore, the ICA provides a useful tool for the on-site detection and rapid initial screening of Sild in functional food samples.

Analysis of multiple mycotoxins-contaminated wheat by a smart analysis platform

This study describes a smart analysis platform capable of quantitative measurements using a multiplex lateral flow strip. Using the multi-mycotoxin strip, five fungal toxins were simultaneously and quantitatively detected in naturally contaminated wheat. First, a matrix-based standard curve was established for the detection of aflatoxin B1 (AFB1), fumonisin B1 (FB1), T-2, deoxynivalenol (DON), and zearalenone (ZEN). Established on an open android system, the platform is able to read 6 lines on the strip simultaneously. The platform is equipped with a Quick Response code scanning model, which reads the established standard curves, and then rapidly quantify mycotoxins in naturally contaminated wheat. All the data and sample information are stored on a central server through the platform which is linked to the cloud. The limits of detection (LOD) for AFB1, FB1, T-2, DON, and ZEN in wheat were 4, 20, 10, 200, and 40 μg/kg and the visual cut off values was 20, 1000, 200, 4000, and 400 μg/kg, separately. To validate the platform and the multi-mycotoxin detection method, 10 wheat samples were analyzed and the results were in a good agreement with those obtained by LC-MS/MS. The platform will be a powerful tool for crop monitoring services.

Rapid and sensitive detection of mycotoxins by advanced and emerging analytical methods: A review

Quantification of mycotoxins in foodstuffs is extremely difficult as a limited amount of toxins are known to be presented in the food samples. Mycotoxins are secondary toxic metabolites, made primarily by fungal species, contaminating feeds and foods. Due to the presence in globally used grains, it is an unpreventable problem that causes various acute and chronic impacts on human and animal health. Over the previous few years, however, progress has been made in mycotoxin analysis studies. Easier techniques of sample cleanup and advanced chromatographic approaches have been developed, primarily high-performance liquid chromatography. Few extremely sophisticated and adaptable tools such as high-resolution mass spectrometry and gas chromatography-tandem MS/MS have become more important. In addition, Immunoassay, Advanced quantitative techniques are now globally accepted for mycotoxin analysis. Thus, this review summarizes these traditional and highly advance methods and their characteristics for evaluating mycotoxins.

Development of a Gold Nanoparticle-Based Lateral-Flow Immunoassay for Pneumocystis Pneumonia Serological Diagnosis at Point-of-Care

Pneumocystis jirovecii pneumonia (PcP) is a major human immunodeficiency virus (HIV)-related illness, rising among immunocompromised non-HIV patients and in developing countries. Presently, the diagnosis requires respiratory specimens obtained through invasive and costly techniques that are difficult to perform in all patients or implement in all economic settings. Therefore, the development of a faster, cost-effective, non-invasive and field-friendly test to diagnose PcP would be a significant advance. In this study, recombinant synthetic antigens (RSA) of P. jirovecii's major surface glycoprotein (Msg) and kexin-like serine protease (Kex1) were produced and purified. These RSA were applied as antigenic tools in immunoenzymatic assays for detection of specific anti-P. jirovecii antibodies (IgG and IgM) in sera of patients with (n = 48) and without (n = 28) PcP. Results showed that only IgM anti-P. jirovecii levels were significantly increased in patients with PcP compared with patients without P. jirovecii infection (p ≤ 0.001 with both RSA). Thus, two strip lateral flow immunoassays (LFIA), based on the detection of specific IgM anti-P. jirovecii antibodies in human sera samples, were developed using the innovative association of P. jirovecii's RSA with spherical gold nanoparticles (AuNPs). For that, alkanethiol-functionalized spherical AuNPs with ca. ~40 nm in diameter were synthetized and conjugated with the two RSA (Msg or Kex1) produced. These AuNP-RSA conjugates were characterized by agarose gel electrophoresis (AGE) and optimized to improve their ability to interact specifically with serum IgM anti-P. jirovecii antibodies. Finally, two LFIA prototypes were developed and tested with pools of sera from patients with (positive sample) and without (negative sample) PcP. Both LFIA had the expected performance, namely, the presence of a test and control red colored lines with the positive sample, and only a control red colored line with the negative sample. These results provide valuable insights into the possibility of PcP serodiagnosis at point-of-care. The optimization, validation and implementation of this strip-based approach may help to reduce the high cost of medical diagnosis and subsequent treatment of PcP both in industrialized and low-income regions, helping to manage the disease all around the world.

Paper-Based Microfluidic Device (DON-Chip) for Rapid and Low-Cost Deoxynivalenol Quantification in Food, Feed, and Feed Ingredients

Mycotoxin contamination causes over $5 billion of economic loss per year in the North American food and feed industry. A rapid, low-cost, portable, and reliable method for on-site detection of deoxynivalenol (DON), a representative mycotoxin predominantly occurring in grains, would be helpful to control mycotoxin contamination. In this study, a paper-based microfluidic chip capable of measuring DON (DON-Chip) in food, feed, and feed ingredients was developed. The DON-Chip incorporated a colorimetric competitive immunoassay into a paper microfluidic device and used gold nanoparticles as a signal indicator. Furthermore, a novel ratiometric analysis method was proposed to improve detection resolvability. Detection of DON in the aqueous extracts from solid food, feed, or feed ingredients was successfully validated with a detection range of 0.01-20 ppm (using dilution factors from 10 to 10⁴). Compared with conventional methods, the DON-Chip method could greatly reduce the cost and time of mycotoxin detection in the food and feed industry.

Synthesis and application of magnetic-surfaced pseudo molecularly imprinted polymers for zearalenone pretreatment in cereal samples

Zearalenone (ZEA) is a fungal contaminant widely found in grains. In cereal samples, trace zearalenone was extracted and enriched using magnetic-surfaced pseudo molecularly imprinted polymers (SPMIPs) and detected. SPMIPs were prepared with Fe₃O₄ as the magnetic core, modified halloysites nanotubes as supporting materials, and selective imprinted polymers as shells. Vinyl was modified on the surface of halloysites nanotube. SPMIPs were synthesized with pseudo templates. SPMIPs as the adsorbent of dispersed-solid phase extraction (μ-SPE) were used to purify and enrich ZEA from maize samples. After optimized, the pretreatment method was evaluated. The linearity of the method was ranged within 10-200 ng mL^-1. LOD and LOQ were 2.5 ng mL^-1 and 8 ng mL^-1 respectively. The ZEA spiking recoveries in maize samples ranged within 74.95-88.41% were with good RSDs lower than 4.25%. The developed method was successful applied in maize, oat, and wheat sample treatments and compared.

An aptamer-based colorimetric lateral flow assay for the detection of human epidermal growth factor receptor 2 (HER2)

An aptamer-based colorimetric lateral flow assay was developed for the detection of human epidermal growth factor receptor 2 (HER2). In this study, two approaches were examined using HER2 binding aptamers and gold nanoparticles. The first method used was a solution-based adsorption-desorption colorimetric approach wherein aptamers were adsorbed onto the gold nanoparticle surface. Upon the addition of HER2, HER2 binds specifically with its aptamer, releasing the gold nanoparticles. Addition of NaCl then induces the formation of gold nanoparticle aggregates. This leads to a color change from red to blue and a detection limit of 10 nM was achieved. The second method used an adsorption-desorption colorimetric lateral flow assay approach wherein biotin-modified aptamers were adsorbed onto the gold nanoparticle surface in the absence of HER2. In the presence of HER2, HER2 specifically binds with its aptamer leading to release of the gold nanoparticles. These solutions were applied to the lateral flow assay format and a detection limit of 20 nM was achieved. Both colorimetric and lateral flow assays are inexpensive, simple, rapid to perform and produce results visible to the naked-eye.

Lateral Flow Immunoassay Based on Polydopamine-Coated Gold Nanoparticles for the Sensitive Detection of Zearalenone in Maize

In this work, polydopamine-coated gold nanoparticles (Au@PDAs) were synthesized by the oxidative self-polymerization of dopamine (DA) on the surface of AuNPs and applied for the first time as a signal-amplification label in lateral flow immunoassays (LFIAs) for the sensitive detection of zearalenone (ZEN) in maize. The PDA layer functioned as a linker between AuNPs and anti-ZEN monoclonal antibody (mAb) to form a probe (Au@PDA-mAb). Compared with AuNPs, Au@PDA had excellent color intensity, colloidal stability, and mAb coupling efficiency. The limit of detection of the Au@PDA-based LFIA (Au@PDA-LFIA) was 7.4 pg/mL, which was 10-fold lower than that of the traditional AuNP-based LFIA (AuNP-LFIA) (76.1 pg/mL). The recoveries of Au@PDA-LFIA were 93.80-111.82%, with the coefficient of variation of 1.08-9.04%. In addition, the reliability of Au@PDA-LFIA was further confirmed by the high-performance liquid chromatography method. Overall, our study showed that PDA coating can chemically modify the surface of AuNPs through a simple method and can thus significantly improve the detection sensitivity of LFIA.

Zearalenone Contamination in Corn, Corn Products, and Swine Feed in China in 2016-2018 as Assessed by Magnetic Bead Immunoassay

In total, 405 samples of corn, corn products, and swine feed from China in 2016-2018 were surveyed for zearalenone (ZEN) contamination using a magnetic bead immunoassay-coupled biotin-streptavidin system (BAS-MBI). The developed BAS-MBI had a limit of detection (LOD) of 0.098 ng mL-1, with half-maximal inhibition concentration (IC50) of 0.71 ng mL-1 in working buffer, and an LOD of 0.98 ng g-1; the detection range was from 0.98 to 51.6 ng g-1 in authentic agricultural samples. The BAS-MBI has been demonstrated to be a powerful method for the rapid, sensitive, specific, and accurate determination of ZEN. The ZEN positivity rate reached the highest level of 40.6% in 133 samples in 2016; ZEN levels ranged from 1.8 to 1100.0 ng g-1, with an average level of 217.9 ng g-1. In 2017, the ZEN positivity rate was the lowest at 24.5% in 143 samples; ZEN levels ranged from 1.1 to 722.6 ng g-1, with an average of 166.7 ng g-1. In 2018, the ZEN positivity rate was 31.8% in 129 samples; ZEN levels ranged from 1.3 to 947.8 ng g-1, with an average of 157.0 ng g-1. About 20% of ZEN-positive samples exceeded maximum limit levels. An alternative method of ZEN detection and a valuable reference for ZEN contamination in corn and its related products in China are provided. This survey suggests the need for prevention of serious ZEN contamination, along with management for food safety and human health.

Multiplex Detection of Nucleic Acids Using Recombinase Polymerase Amplification and a Molecular Colorimetric 7-Segment Display

Nucleic acid analysis has become highly relevant for point-of-care (POC) diagnostics since the advent of isothermal amplification methods that do not require thermal cycling. In particular, recombinase polymerase amplification (RPA) combined with lateral flow detection offers a rapid and simple solution for field-amenable low-resource nucleic acid testing. Expanding POC nucleic acid tests for the detection of multiple analytes is vital to improve diagnostic efficiency because increased multiplexing capacity enables higher information density combined with reduced assay time and costs. Here, we investigate expanding RPA POC detection by identifying a generic multiplex RPA format that can be combined with a generic multiplex lateral flow device (LFD) to enable binary and molecular encoding for the compaction of diagnostic data. This new technology relies on the incorporation of molecular labels to differentiate nucleic acid species spatially on a lateral flow membrane. In particular, we identified additional five molecular labels that can be incorporated during the RPA reaction for subsequent coupling with LFD detection. Combined with two previously demonstrated successful labels, we demonstrate potential to enable hepta-plex detection of RPA reactions coupled to multiplex LFD detection. When this hepta-plex detection is combined with binary and molecular encoding, an intuitive 7-segment output display can be produced. We note that in all experiments, we used an identical DNA template, except for the 5' label on the forward primer, to eliminate any effects of nucleic acid sequence amplification bias. Our proof-of-concept technology demonstration is highly relevant for developing information-compact POC diagnostics where space and time are premium commodities.

Lateral flow assays for Ochratoxin A using metal nanoparticles: comparison of "adsorption-desorption" approach to linkage inversion assembled nano-aptasensors (LIANA)

Nano-aptamer probes were prepared and used in lateral flow colorimetric assays for the detection of Ochratoxin A (OTA). In this study, two approaches were examined using 5'-biotin-modified OTA aptamers and silver or gold nanoparticles (AgNP or AuNP). The first method used an "adsorption-desorption" approach wherein aptamers were adsorbed onto the metal nanoparticle surface. Upon the addition of OTA, the aptamer binds specifically to the target, releasing the NPs. The above solutions were applied on a lateral flow assay (LFA) and a detection limit of 6.3 nM was achieved with both metal nanoparticles. The second method used a labelled approach based on Linkage Inversion Assembled Nano-Aptasensors (LIANAs) using a DNA linker containing a 5'-5' linkage inversion (5'-5' linker) to assemble biotinylated aptamer-functionalized metal nanoparticles. In the presence of target, OTA specifically binds with its aptamer leading to release of the linker and disassembly of LIANA aggregates into dispersed nanoparticles. The same solutions were applied in LFA format and the lowest detection limit of 0.63 nM was achieved. The results indicated that the LIANA-based LFA strips were more sensitive than the "adsoprtion-desorption" LFAs. Both lateral flow assays are inexpensive, simple, and rapid to perform and produces results visible to the naked-eye.

Dual flow immunochromatographic assay for rapid and simultaneous quantitative detection of ochratoxin A and zearalenone in corn, wheat, and feed samples

A one-step dual flow immunochromatographic assay (DICGA), based on a competitive format, was developed for simultaneous quantification of ochratoxin A (OTA) and zearalenone (ZEN) in corn, wheat, and feed samples. The limit of detection for OTA was 0.32 ng/ml with a detection range of 0.53‒12.16 ng/ml, while for ZEN it was 0.58 ng/ml with a detection range of 1.06‒39.72 ng/ml. The recovery rates in corn, wheat, and feed samples ranged from 77.3% to 106.3% with the coefficient of variation lower than 15%. Naturally contaminated corn, wheat, and feed samples were analyzed using both DICGA and liquid chromatography-tandem mass spectrometry (LC-MS/MS) and the correlation between the two methods was evaluated using a regression analysis. The DICGA method shows great potential for simple, rapid, sensitive, and cost-effective quantitative detection of OTA and ZEN in food safety control.

Quantitative and rapid detection of amantadine and chloramphenicol based on various quantum dots with the same excitations

Herein, we developed a sensitive and quantitative flow assay for simultaneous detection of amantadine (AMD) and chloramphenicol (CAP) in chicken samples based on different CdSe/ZnS quantum dots (QDs). In contrast to other reports, the QDs could be excited by the same excitations that lowered the requirements for the matching instruments. Under the optimal conditions, the strategy permitted sensitive detection of AMD and CAP in a linear range of 0.23 to 1.02 ng/g and 0.02 to 0.66 ng/g. The limits of detection were 0.18 ng/g and 0.016 ng/g, respectively. Moreover, the whole detection process could be completed within 20 min with no additional sophisticated instruments and complicated operations. Spiked samples were analyzed using both QD-based lateral flow immunoassay (QD-LFIA) and commercial ELISA kits with good correlation (R² = 0.96). Moreover, this study laid the foundation and simplified the development of the requisite instrument. Graphical abstract ᅟ.

Response of the nuclear receptors PXR and CAR and their target gene mRNA expression in female piglets exposed to zearalenone

A study was conducted to determine the effects of zearalenone (ZEN) on the mRNA expression of pregnane X receptor (PXR), constitutive and rostane receptor (CAR), and phase I and II enzymes as well as the toxicity in the liver of female weanling piglets. Thirty-two female weanling piglets (Duroc × Landrace × Large white, 12.27 ± 0.30 kg)were divided into four groups (n = 8 piglets/group) that were supplemented with 0 (control), 0.5, 1 or 2 mg/kg ZEN. The trial period lasted for 28 d. The results showed that the ZEN supplementation in the diets (0.5-2 mg/kg) had no effect on growth performance but dose-dependently increased serum aspartate aminotransferase, alanineaminotransferase, alkaline phosphatase, and γ-glutamyltransferase activities (P < 0.05). The ZEN residue in the liver (P < 0.01) was also linearly and dose-dependently increased. Furthermore, the mRNA expression of PXR, CAR, phase I enzymes (i.e., cyp2e1, cyp3a5, cyp2a6, cyp1a1, and cyp1a2), and phase II enzymes (i.e., gsta1, gsta2, ugt1a3) significantly increased linearly in a dose-dependent manner (P < 0.05). However, the spleen relative weight and the glutathione peroxidase activity in the liver (P < 0.05) linearly decreased as the dietary ZEN concentration increased; the mRNA expression of the nuclear receptors PXR and CAR is responsive to ZEN in female piglets, and ZEN increases the mRNA expression of their target genes. This finding shows that the nuclear receptor signaling system plays an important role in the defense against ZEN.

Development of an immunochromatographic lateral flow strip for the simultaneous detection of aminoglycoside residues in milk

A colloidal gold-based immunochromatographic strip with a competitive format has been developed for the rapid, simultaneous, semi-quantitative and quantitative detection of several aminoglycoside residues in milk, including gentamicin sulfate (GM), neomycin sulfate (NEO) and kanamycin sulfate (KN). Three monoclonal antibodies against the three corresponding aminoglycosides were conjugated to colloidal gold particles and applied to the conjugate pads of the strip. The competitors [GM-bovine serum albumin (GM-BSA), NEO-BSA and KN-BSA conjugates] of GM, NEO and KN were immobilized onto a nitrocellulose (NC) membrane at three detection zones, T1, T2, and T3, respectively. The minimal cut-off values of the strip were 10 ng mL-1 for GM, and 100 ng mL-1 for NEO and KN, which are lower than the maximum residue levels (MRLs) established for aminoglycosides. The IC50 values of the strip were 0.737 ng mL-1, 8.971 ng mL-1 and 11.110 ng mL-1 for GM, NEO and KN respectively. In conclusion, the immunochromatographic lateral flow strip could be used for rapid, simultaneous, semi-quantitative and quantitative detection of GM, NEO and KN residues in milk.

An On-Site Simultaneous Semi-quantification of Aflatoxin B1, Zearalenone, and T-2 Toxin in Maize- and Cereal-based Feed via Multicolor Immunochromatographic Assay

Multiple-mycotoxin contamination has been frequently found in the agro-food monitoring due to the coexistence of fungi. However, many determination methods focused on a single mycotoxin, highlighting the demand for on-site determination of multiple mycotoxins in a single run. We develop a multicolor-based immunochromatographic strip (ICS) for simultaneous determination of aflatoxin B1 (AFB1), zearalenone (ZEN) and T-2 toxin in maize- and cereal-based animal feeds. The nanoparticles with different colors are conjugated with three monoclonal antibodies, which serve as the immunoassay probes. The decrease in color intensity is observed by the naked eyes, providing simultaneous quantification of three mycotoxins. The visible limits of detection for AFB1, ZEN and T-2 are estimated to be 0.5, 2, and 30 ng/mL, respectively. The cut-off values are 1, 10, and 50 ng/mL, respectively. Considerable specificity and stability are found using real samples. The results are in excellent agreement with those from high-performance liquid chromatography/tandem mass spectrometry. The multi-color ICS boasts sensitive and rapid visual differentiation and simultaneous semi-quantification of aflatoxin B1, zearalenone and T-2 toxin in maize- and cereal-based feed samples within 20 min.

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.

Development of a Rainbow Lateral Flow Immunoassay for the Simultaneous Detection of Four Mycotoxins

A multiplex lateral flow immunoassay (LFIA) for the determination of the mycotoxins deoxynivalenol, zearalenone, and T2/HT2-toxin in barley was developed with luminescent quantum dots (QDs) as label. The synthesized QDs were hydrophilized by two strategies, that is, coating with an amphiphilic polymer or silica. The water-soluble QDs were compared with regard to their bioconjugation with monoclonal antibody (mAb) and were tested on a LFIA. Silica-coated QDs that contained epoxy groups were most promising. Therefore, green, orange, and red epoxy-functionalized silica-coated QDs were conjugated with anti-ZEN, anti-DON, and anti-T2 mAb, respectively. The LFIA was developed in accordance with the European Commission legal limits with cutoff limits of 1000, 80, and 80 μg/kg for deoxynivalenol, zearalenone, and T2/HT2-toxin, respectively. The LFIA gave a fast result (15 min) with a low false-negative rate (<5%), and the results were easy to interpret without any sophisticated equipment.

Recent advancements in lateral flow immunoassays: A journey for toxin detection in food

Biotechnology embraces various physical and chemical phenomena toward advancement of health diagnostics. Toward such advancement, detection of toxins plays an important role. Toxins produce severe health impacts on consumption with high mortality associated in acute cases. The most prominent route of infection and intoxication is through food matrices. Therefore, rapid detection of toxins at low concentrations is the need of modern diagnostics. Lateral flow immunoassays are one of the emergent and popularly used rapid detection technology developed for detecting various kinds of analytes. This review thus focuses on recent advancements in lateral flow immunoassays for detecting different toxins in agricultural food. Appropriate emphasis was given on how the labels, recognition elements, or detection strategy has laid an impact on improvement in immunochromatographic assays for toxins. The paper also discusses the gradual change in sensitivities and specificities of assays in accordance with the method of food processing used. The review concludes with the major challenges faced by this technology and provides an outlook and insight of ideas to improve it in the future.

Fluorescence Polarization Immunoassay Based on a New Monoclonal Antibody for the Detection of the Zearalenone Class of Mycotoxins in Maize

To develop a sensitive fluorescence polarization immunoassay (FPIA) for screening the zearalenone class of mycotoxins in maize, two new monoclonal antibodies with uniform affinity to the zearalenone class and four fluorescein-labeled tracers were prepared. After careful selection of appropriate tracer-antibody pairs in terms of sensitivity and specificity, a FPIA that could simultaneously detect the zearalenone class with similar sensitivity was developed. Under optimum conditions, the half maximal inhibitory concentrations of the FPIA in buffer were 1.89, 1.97, 2.43, 1.99, 2.27, and 2.44 μg/L for zearalenone, α-zearalenol, β-zearalenol, α-zearalanol, β-zearalanol, and zearalanone, respectively. The limit of detection of FPIA for the zearalenone class was around 12 μg/kg in maize, and the recoveries ranged from 84.6 to 113.8%, with coefficients of variation below 15.3% in spiked samples. Finally, the FPIA was applied for screening naturally contaminated maize samples, and the results indicated a good correlation with that of high-performance liquid chromatography-tandem mass spectrometry.

Development of an immunochromatographic test strip for simultaneous qualitative and quantitative detection of ochratoxin A and zearalenone in cereal

BACKGROUND

Ochratoxin A (OTA) and zearalenone (ZEN) are natural products of filamentous fungi that are harmful to humans and animals exposed to them even in extremely low concentration. The immunochromatographic test strip has become a popular diagnostic tool for detecting analytes. Its major advantages are that results can be obtained within 5-10 min, all needed reagents are included in the strip and it can be used to detect OTA and ZEN contamination in spots. In this study a colloidal gold-based immunochromatographic test strip of competitive format was developed for the rapid simultaneous qualitative and quantitative detection of OTA and ZEN in corn and other cereals.

RESULTS

The test strip results with the naked eye showed that the sensitivities were 6 µg kg(-1) OTA and 20 µg kg(-1) ZEN in cereal, while those with a TSR3000 membrane strip reader showed that the IC50 values of OTA and ZEN were 1.7905 and 4.3514 ng mL(-1) and the lower detection limit (LDL) values were 0.7697 and 1.2000 µg kg(-1) respectively. These results were confirmed by high-performance liquid chromatography.

CONCLUSION

The immunochromatographic test strip developed in this study could be used for the rapid simultaneous, qualitative and quantitative screening of OTA and ZEN in corn samples. © 2015 Society of Chemical Industry.

Opportunities and challenges for the application of microfluidic technologies in point-of-care veterinary diagnostics

There is a growing need for low-cost, rapid and reliable diagnostic results in veterinary medicine. Point-of-care (POC) tests have tremendous advantages over existing laboratory-based tests, due to their intrinsic low-cost and rapidity. A considerable number of POC tests are presently available, mostly in dipstick or lateral flow formats, allowing cost-effective and decentralised diagnosis of a wide range of infectious diseases and public health related threats. Although, extremely useful, these tests come with some limitations. Recent advances in the field of microfluidics have brought about new and exciting opportunities for human health diagnostics, and there is now great potential for these new technologies to be applied in the field of veterinary diagnostics. This review appraises currently available POC tests in veterinary medicine, taking into consideration their usefulness and limitations, whilst exploring possible applications for new and emerging technologies, in order to widen and improve the range of POC tests available.