Visual Measurement of Fumonisin B1 with Bipolar Electrodes Array-Based Electrochemiluminescence Biosensor

Fumonisin B1 (FB1) is a common mycotoxin found in maize and maize-based food products. Although FB1 is relatively heat stable and survives most thermal processes, extrusion cooking has been shown to be effective at reducing levels of the toxin in contaminated maize. This review summarises studies on the chemical and toxicological fate of FB1 in maize extruded under different conditions. Overall, these studies indicate that stability of FB1 depends on the extrusion conditions, e.g. temperature and screw speed, and that the presence of reducing sugars augment apparent loss of the toxin. The chemical fate of FB1 was investigated by measuring FB1, hydrolysed FB1, and N-substituted FB1 compounds with a mass balance approach while the relative toxicity was determined by rat feeding trials. FB1 in contaminated grits was reduced by 21-37% and 77-87% in the absence and presence of 10% (w/w) glucose, respectively, during single-screw extrusion. Greater reductions of 64-72% and 89-94% were achieved by twin-screw extrusion. Mass balance analysis showed that most of the FB1 in grits extruded without glucose was recovered as FB1, whereas the FB1-glucose reaction product, N-(deoxy-D-fructos-1-yl)-fumonisin B1 was the prevalent form after extrusion with glucose. 23 to 38% of FB1 in extruded grits with and without added glucose was bound to component(s) of the maize grits. Only 37-46% of FB1 present in unextruded grits could be recovered as one of the fumonisin species (hydrolysed FB1, N-substituted FB1 compounds) or as matrix-bound forms in extruded grits. Reduced FB1 concentrations in extruded grits and the even lower concentrations in grits extruded with glucose resulted in a dose-dependent reduction of toxicity as shown by the less severe apoptotic lesions and sphingolipid effects that were found in the kidneys of rats. In summary, extrusion processing, especially with glucose supplementation, is potentially useful to reduce FB1 concentrations and toxicity of contaminated maize.

Review on the natural co-occurrence of AFB1 and FB1 in maize and the combined toxicity of AFB1 and FB1

Occurrence of Aflatoxins, Fumonisin B1, and Zearalenone in Foods and Feeds in Botswana

Fumonisins (FBs) and zearalenone (ZEN) are mycotoxins which occur naturally in grains and cereals, especially maize, causing negative effects on animals and humans. Along with the need for constant monitoring, there is a growing demand for rapid, non-destructive methods. Among these, Near Infrared Spectroscopy (NIR) has made great headway for being an easy-to-use technology. NIR was applied in the present research to quantify the contamination level of total FBs, i.e., fumonisin B1+fumonisin B2 (FB1+FB2), and ZEN in Brazilian maize. From a total of six hundred and seventy-six samples, 236 were analyzed for FBs and 440 for ZEN. Three regression models were defined: one with 18 principal components (PCs) for FB1, one with 10 PCs for FB2, and one with 7 PCs for ZEN. Partial least square regression algorithm with full cross-validation was applied as internal validation. External validation was performed with 200 unknown samples (100 for FBs and 100 for ZEN). Correlation coefficient (R), determination coefficient (R2), root mean square error of prediction (RMSEP), standard error of prediction (SEP) and residual prediction deviation (RPD) for FBs and ZEN were, respectively: 0.809 and 0.991; 0.899 and 0.984; 659 and 69.4; 682 and 69.8; and 3.33 and 2.71. No significant difference was observed between predicted values using NIR and reference values obtained by Liquid Chromatography Coupled to Tandem Mass Spectrometry (LC-MS/MS), thus indicating the suitability of NIR to rapidly analyze a large numbers of maize samples for FBs and ZEN contamination. The external validation confirmed a fair potential of the model in predicting FB1+FB2 and ZEN concentration. This is the first study providing scientific knowledge on the determination of FBs and ZEN in Brazilian maize samples using NIR, which is confirmed as a reliable alternative methodology for the analysis of such toxins.

Colorimetric aptasensor for fumonisin B1 detection by regulating the amount of bubbles in closed bipolar platform

This study was designed to develop a sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the simultaneous detection and quantification of 25 mycotoxins in cassava flour, peanut cake and maize samples with particular focus on the optimization of the sample preparation protocol and method validation. All 25 mycotoxins were extracted in a single step with a mixture of methanol/ethyl acetate/water (70:20:10, v/v/v). The method limits of quantification (LOQ) varied from 0.3 μg/kg to 106 μg/kg. Good precision and linearity were observed for most of the mycotoxins. The method was applied for the analysis of naturally contaminated peanut cake, cassava flour and maize samples from the Republic of Benin. All samples analyzed (fifteen peanut cakes, four maize flour and four cassava flour samples) tested positive for one or more mycotoxins. Aflatoxins (total aflatoxins; 10-346 μg/kg) and ochratoxin A (<LOQ-2 μg/kg) were detected in peanut cake samples while fumonisin B(1) (4-21 μg/kg), aflatoxin B(2) (<LOQ-8 μg/kg), aflatoxin B(1) (<LOQ-9 μg/kg), diacetoxyscirpenol (<LOQ-6 μg/kg) and zearalenone (<LOQ-12 μg/kg) were detected and quantified in cassava flour samples. Fumonisin B(1) (13-836 μg/kg), fumonisin B(2) (5-221 μg/kg), fumonisin B(3) (<LOQ-375 μg/kg) and beauvericin (<LOQ-25 μg/kg) were detected in the maize samples.

Dual-quenching effects of methylene blue on the luminophore and co-reactant: Application for electrochemiluminescent-electrochemical ratiometric zearalenone detection

The fumonisin B1 content of 69 visibly mouldy and 23 mould-free maize samples grown in Hungary in 1993-1995 was determined by high-performance liquid chromatography (HPLC). Fumonisin B1 was found to occur in 70-73% of the mouldy samples. The mycotoxin level increased from year to year: the highest fumonisin B1 concentration was 75.1 mg/kg. The samples that were mould-free on visual inspection showed a much lower prevalence of fumonisin B1 contamination (30%) and contained fumonisin B1 in markedly lower concentrations (average, 1.52 mg/kg; maximum concentration, 5.1 mg/kg). Using the Fusarium moniliforme strain designated 14/A, isolated from the sample that had the highest mycotoxin concentrations, fumonisin B1 toxin was produced on maize by an internationally accepted procedure. Subsequently, two weaned piglets were fed a diet containing 330 mg fumonisin B1 per kg of feed. The experimental animals developed hydrothorax and pulmonary oedema, and died in 5-6 days. The clinical symptoms and pathological lesions were consistent with those of porcine pulmonary oedema (PPE) diagnosed in the USA in 1989-1990, as well as with those of a disease entity that had already been described in Hungary in the 1950s as the so-called fattening or unique pulmonary oedema of pigs but considered to be of unknown aetiology. The results of the feeding trial confirm that this pig disease, which has occurred in Hungary for a long time, is caused by the mycotoxin fumonisin B1.

High resolution and intense signal are challenges in electrochemiluminescence (ECL) imaging analysis. In this study, two novel color-potential-discriminated nanoreactor luminophores with high intensity ECL were innovatively prepared via a nanoconfinement effect, which was used to construct a sensitive bipolar electrode (BPE)-ECL biosensor by electrocatalyst amplification for ECL detection and imaging of mecA and ARGAMP gene. First, a new ZrMOF with a porous structure was employed as a microreactor to accommodate abundant luminophor, Ru(bpy)32+ or luminol molecules, which not only produced an amplified high-strength ECL signal but also realized sensitive color discrimination. Thus, the two nanoreactor luminophors were combined with an outstanding electrocatalyst, Pt@PMOF(Fe), to fabricate a color-discriminated BPE biosensor for ECL sensing of dual targets. The amplification product output DNA 1 of target mecA introduced Pt@PMOF(Fe) into the A hole of channel 1 in BPE. During positive potential scan, the polarity of A hole was negative, so the excellent electrocatalytic performance promoted the decomposition of H2O2 and accelerated the electron transfer of BPE, which greatly improved the red ECL signal of RuMOFs for mecA detection. In negative-potential sweep, the amplification product of ARGAMP introduced the electrocatalyst into B-hole with negative polarity in channel 2, so the blue ECL signal of L@ZrMOFs was enhanced for ECL detection and phone imaging assay of ARGAMP. This work is for the first time to apply the color-potential-resolved nanoreactor luminophore into BPE-ECL sensing imaging analysis, which opened new techniques and applications in BPE-ECL analysis.

Bipolar electrochemistry is promising in realizing simultaneous multiplexed detection. In open bipolar systems, a potential gradient is formed in a solution. When an isolated electrode (bipolar electrode: BPE) that is not in contact with an external device is placed in the potential gradient, interfacial potential difference develops between the BPE and the solution (Figure 1A). As a result, oxidation and reduction reactions occur simultaneously on both poles (Figure 1B) [1]. The progress of the reduction reaction on the cathodic pole can be measured by coupling the reaction with a reaction that generates electrochemiluminescence (ECL) [2]. However, a problem with this method is that the interfacial potential difference on the BPE is not precisely controlled. In other words, the potential profile with respect to the electrode potential changes (Figure 1C). To solve this problem, we used an ion-selective membrane (ISM) on a part of the BPE. The ISM has an effect to fix the interfacial potential difference at the location without current generation through the interface (Figure 1D).Arrays of BPEs were formed with gold and Na+ ISM was formed on a part of each BPE. The surface of the BPE was insulated with a polyimide layer except for the anodic and cathodic poles and the active area of the ISM. To form the ISM, a layer of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT/PSS) was first coated on an exposed area of the BPE. The Na+ ISM was formed on the PEDOT/PSS layer. The solution to form the ISM contained 43.97 wt% polyvinyl chloride (PVC) dissolved in 1 mL tetrahydrofuran (THF). 53.38 wt% of nitrophenyl octyl ether (NPOE), 2.04 wt% of sodium ionophore X, and 0.61 wt% (w/w) of sodium tetrakis(4-fluorophenyl)borate (NaTFPB) were added to the PVC solution and mixed well. After forming the ISM, its peripheries were fixed with a silicone adhesive.In the experimental setup shown in Figure 1A, platinum wires (diameter: 0.5 mm) were used for the driving electrodes. The distance between the driving electrodes was 30 mm. To cause the ECL reaction, 10 mM phosphate buffer solution (pH 6.9) containing 5.0 mM tripropylamine (TPA) and 1.0 mM [Ru(bpy)3]2+ was used. Oxygen dissolved in the solution was used as an analyte. The experiments were conducted at 25°C.To control the potential of the BPEs, we previously used Ag/AgCl for the potential control. However, a problem was that current flowed through the non-polarizable metal/solution interface, affecting the ECL intensity. With regard to this, the ISM is superior because current does not flow. The effect of placing the ISM on a part of the BPE was first examined using BPEs of the same length and changing the location of the ISM (Figure 2). The ion selective electrode (ISE) was effective and the ECL intensity changed by changing the location of the ISE. The effect of the ISM was also demonstrated using folded double BPE structures with the ISM formed at either or both ends. Brighter ECL was observed with the folded structure compared with a single BPE. From these experiments, the effect of placing the ISM on BPEs was clearly observed. As an application to biosensing, we also tested the detection of glucose by immobilizing glucose oxidase and osmium polymer on the cathodic pole. The ECL was also observed accompanying the production of hydrogen peroxide by glucose oxidase and following the reduction of hydrogen peroxide.The effect of placing the ISM was also examined in closed bipolar systems. In the closed bipolar systems, solutions in the cathode and anode side are separated in different compartments. In this study, 15 mm-long electrodes were used and the electrodes extended in the two compartments. The anodic pole was exposed to the solution for ECL, whereas the cathodic pole was immersed in a Na2SO4 solution. A voltage (2.4 V) was applied between the driving electrodes immersed at the end of the solutions. The brightest ECL was observed on the BPE with the ISM nearest to the cathodic pole. The result indicates that the ISM is also effective in controlling the potential for closed bipolar systems.[1] S. E. Fosdick, K. N. Knust, K. Scida, R. M. Crooks. Bipolar electrochemistry. Angewandte Chemie International Edition, 52 (2013) 10438-10456. doi:10.1002/anie.201300947[2] K. F. Chow, F. Mavré, R. M. Crooks. Wireless electrochemical DNA microarray sensor. Journal of the American Chemical Society, 130 (2008) 7544-7545. doi:10.121/ja802013q Figure 1

Development of immune-affinity 96 spots monolith array for multiple mycotoxins detection in food samples.

Twenty five samples of maize intended for human or animal consumption coming from North, Central and South Vietnam were analysed for fungal contamination and for the presence of aflatoxin B1 and fumonisin B1. The total fungal load was found to be greater in maize intended for animal feed than for human consumption with average levels of 4x106 and 7x105 CFU/g, respectively. Identification of fungal strains revealed that Aspergillus was the most frequent genus, found in all maize samples whatever their intended use or their geographic origin. Among the Aspergillus species, A. flavus was the most frequent contaminant, observed in more than 90% of the samples. Other fungal strains found in the Vietnamese maize samples belonged to Penicillium species, Fusarium verticillioides and to the Mucorales, and were found in up to 53, 33 and 23% of the samples, respectively. All samples were tested for both aflatoxin and fumonisin contamination. Aflatoxin B1 was found in 17 samples (68%). Five of these samples showed aflatoxin B1 levels below 10 µg/kg, ten samples were found to be contaminated in a range of 11.3 to 47.2 µg/kg, and 2 samples showed contamination levels of 98.4 and 126.5 µg/kg, respectively. The maize samples for human consumption were found frequently contaminated with aflatoxin B1 (77%), but the level of contamination was lower than those for animal consumption. Fumonisin B1 contamination was found in 8 out of 25 samples (32%). Detected amounts of fumonisin B1 ranged from 0.4 to 3.3 mg/kg.

Co-contamination and interactions of multiple mycotoxins and heavy metals in rice, maize, soybeans, and wheat flour marketed in Shanghai City

Detection of Fumonisins in Fusarium Cultures, Corn, and Corn Products by Polyclonal Antibody-Based ELISA: Relation to Fumonisin B1 Detection by Liquid Chromatography

Hydrogen peroxide regulated split-type electrochemiluminescence sensing platform for non-invasive detection of gastric cancer-associated D-amino acids.