Aflatoxin B1 In Corn Research Articles

Development of a label-free, sensitive gold nanoparticles-poly(adenine) aptasensing platform for colorimetric determination of aflatoxin B1 in corn.

In this work, a sensitive colorimetric bioassay method based on a poly(adenine) aptamer (polyA apt) and gold nanoparticles (AuNPs) was developed for the determination of aflatoxin B1 (AFB1). The polyA apt, adsorbed on the AuNPs, especially can bind to the analyte while deterring non-specific interactions. This nano aptasensor uses cationic polymer poly(diallyl dimethyl ammonium chloride) (PDDA), as an aggregating agent, to aggregate gold nanoparticles. PolyA apt-decorated gold nanoparticles (AuNPs/polyA apt) show resistance to PDDA-induced aggregation and maintains their dispersed state (red color) with the optical absorbance signal at λ = 520 nm. However, in the presence of AFB1 in the assay solution, the specific aptamer reacts with high affinity and folds into its three-dimensional form. Aggregation of AuNPs induced by PDDA caused their optical signal shift to λ = 620 nm (blue color). AFB1 concentration in the bioassay solution determines the amount of optical signal shift. Therefore, optical density ratio in two wavelengths (A620/520) can be used as a sturdy colorimetric signal to detect the concentration of aflatoxin B1. AFB1 was linearly detected between 0.5 and 20 ng mL-1, with a detection limit of 0.09 ng mL-1 (S/N = 3). The fabricated aptasensor was applied to the detection of AFB1 in real corn samples.

Optimizing the degradation of aflatoxin B1 in corn by Trametes versicolor and improving the nutritional composition of corn.

Corn, being an important grain, is prone to contamination by aflatoxin B1 (AFB1 ), and AFB1 -contaminated corn severely endangers the health of humans and livestock. Trametes versicolor, a fungus that can grow in corn, possesses the ability to directly degrade AFB1 through its laccase. This study aimed to optimize the fermentation conditions for T. versicolor to degrade AFB1 in corn and investigate the effect of T. versicolor fermentation on the nutritional composition of corn. AFB1 -contaminated corn was used as the culture substrate for T. versicolor. A combination of single-factor experiments and response surface methodology was employed to identify the optimal conditions of AFB1 degradation. The optimal conditions of AFB1 degradation were as follows: 9 days of fermentation, a fermentation temperature of 26.7 °C, a moisture content of 70.5% and an inoculation amount of 4.9 mL (containing 51.99 mg of T. versicolor mycelia). With the optimal conditions, the degradation rate of AFB1 in corn could reach 93.01%, and the dry basis content of protein and dietary fiber in the fermented corn was significantly increased. More importantly, the lysine content in the fermented corn was also significantly increased. This is the first report that direct fermentation of AFB1 -contaminated corn by T. versicolor not only efficiently degrades AFB1 but also improves the nutritional composition of corn. These findings suggest that the fermentation of corn by T. versicolor is a promising, environmentally friendly and efficient approach to degrade AFB1 and improve the nutritional value of corn. © 2023 Society of Chemical Industry.

Gd2O3:Eu3+ nanoparticle-based magnetic relaxation switch/fluorescence dual-mode immunoassays for aflatoxin B1 in grain

Breakthroughs in high sensitivity and good anti-interference is crucial for achieving high-efficient detection of trace hazards in food. Here, we report on the development of a magnetic relaxation switch (MRS)/fluorescence (FL) dual-mode sensor based on Gd2O3:Eu3+ nanoparticles for the detection of aflatoxin B1 (AFB1) in grain. With the doping of Eu3+ on Gd2O3, it is interesting that the resulted Gd2O3:Eu3+ exhibit significant concentration-dependent MRS/FL responses, thus is capable to be functioned as a dual-mode signal probe for AFB1. In addition, the AFB1 monoclonal antibody was conjugated with magnetic beads (MB) to act as capture probes to separate and concentrate the targets. Based on the specific immunologic recognition, excellent MRS/FL responses of Gd2O3:Eu3+, and the magnetic separation of MB, a dual-mode Sandwich immunoassay was constructed to detect AFB1 with high sensitivity, strong anti-interference, and involves simple preprocessing steps; Under optimal conditions, the detection limits of the MRS and FL modes by the immunoassay for AFB1 are 0.142 and 0.049 μg/kg, respectively. The developed dual-mode immunoassay can be used to detect AFB1 in corn and wheat samples with consistent results from high-performance liquid chromatography. The designed strategy reveals good performance in detecting AFB1, which can extend also to other hazards detection with interest not only for food safety but also environmental monitoring and diagnostics.

The potential of lactic acid bacteria isolated from ikan budu (fermented fish) to inhibit the growth of pathogenic fungi and detoxify aflatoxin B1.

Market demand for safe feed and food supply and consumer preferences for safe and healthy products are increasing. Control measures to counter threats to the feed supply need to be implemented as early as possible to prevent economic losses. Mycotoxins produced by certain groups of fungi are a problem that can disrupt the feed supply or pose a threat to the health of animals and humans. Biological control to detoxify contaminated feed ingredients can be carried out on a large scale economically. For example, lactic acid bacteria (LAB) can act as biological agents for eliminating mycotoxins. This study aimed to clarify the value of screening LAB to inhibit Aspergillus flavus growth and detoxify aflatoxin B1 (AFB1). In this study, using a completely randomized design with three replications, five isolates of LAB (LA.1, LA.6, LA.8, LA.12, and LA.22) along with their supernatants were tested qualitatively and quantitatively for their ability to counter mycotoxins using A. flavus and corn kernels. The isolates with the best activity were identified by sequencing 16S rDNA. The results showed that the five LAB isolates can inhibit the growth of A. flavus and detoxify AFB1. Among these isolates, LA.12 showed the best performance, followed by LA.22, LA.8, LA.6, and then LA.1. The sequencing results confirmed that LA.12 was Lactobacillus harbinensis strain 487. All of the isolates in this study have the potential as biological agents for detoxifying AFB1, with isolate LA.12 appearing to be the most promising biodetoxification agent for feed (AFB1 in corn) based on its ability to inhibit pathogenic fungi.

Optimization of aflatoxin B1 degradation in corn by Ganoderma sinense through solid-state fermentation

Corn is a staple cereal worldwide, but it is frequently contaminated with aflatoxin B1 (AFB1) due to extreme weather or poor storage conditions. The consumption of AFB1-contaminated corn poses a significant health risk to humans and livestock. To address this issue, an environmentally friendly, cost-effective, and efficient method for eliminating AFB1 from corn is needed. In this study, Ganoderma sinense strain Gs-1 with the ability to secrete laccase was used to ferment AFB1-contaminated corn to degrade AFB1. The degradation conditions of AFB1 in corn were optimized through single factor experiments and response surface methodology under solid-state fermentation. The optimal conditions for G. sinense to degrade AFB1 were 12 days of fermentation, a moisture content of 65.2% in the corn substrate, an inoculation amount of 5 mL of G. sinense culture (containing 51.85 mg of G. sinense mycelia), and a fermentation temperature of 27.9 °C. Under these optimal conditions, the degradation rate of AFB1 in corn reached 94.03% through solid-state fermentation with G. sinense. This study provides an economical, environmentally friendly, and efficient strategy for degrading AFB1 in corn, which has great application potential in the food and feed industries.

Simultaneous Determination of Zearalenone and Aflatoxin B1 in Maize by High Performance Liquid Chromatography

This experiment established a method for the simultaneous detection of Zearalenone (ZEN) and Aflatoxin B1 (AFB1) in corn using High-Performance Liquid Chromatography with fluorescence detector. The sample was extracted with acetonitrile: 0.2% formic acid water (volume ratio: 80:20) and passed through a Prime HLB 3cc purification column. Liquid phase detection conditions: The chromatographic column is Agilent C18 (150mm×4.6mm,5μm) The mobile phase is acetonitrile: water (volume ratio: 80:20). The retention time is qualitative and the external standard method is quantitative. The results showed that the correlation coefficients for ZEN 20～1000ng/mL and AFB1 1～50ng/mL were 0.9989 and 0.9976, respectively, and the detection limits were 5μg/kg and 0.8 μg/kg, with an average spiked recovery of 92.7% to 106.2%. This study combines the detection methods in the current two national standards into one, which can simultaneously achieve rapid and synchronous detection of ZEN and AFB1 in corn. The required extraction and detection time is reduced from 60 minutes to 30 minutes, which is 50% less than the original time. The detection results have high accuracy and good stability.

Edible fungi efficiently degrade aflatoxin B1 in cereals and improve their nutritional composition by solid-state fermentation

Aflatoxin B1 (AFB1) is extremely harmful to human and livestock. Laccase, a green catalyst, has been shown to effectively degrade AFB1 and can be obtained from edible fungi. The objective of this study was to screen edible fungi with high laccase activity and determine their effects on the degradation of AFB1 in cereals and the nutritional composition of the cereals through solid-state fermentation. Results from plate assays confirmed that 51 of the 55 tested edible fungi could secrete laccase. Submerged fermentation results showed that 17 of the 51 edible fungi had maximum laccase activity exceeding 100 U/L. The growth of different edible fungi varied significantly in corn, rice and wheat. More importantly, 6 edible fungi with high laccase activity and good growth could efficiently degrade AFB1 in cereals. We found for the first time that Ganoderma sinense could not only secrete highly active laccase and efficiently degrade AFB1 in corn by 92.91%, but also improve the nutritional quality of corn. These findings reveal that solid-state fermentation of cereals with edible fungi is an environmentally friendly and efficient approach for degrading AFB1 in cereals and improving the nutritional composition of cereals.

Aptasensor-based assay for dual-readout determination of aflatoxin B1 in corn and wheat via an electrostatic force-mediated FRET strategy.

Arapid and sensitive aptasensor was established for the dual-readout determination of aflatoxin B1 (AFB1) utilizing an electrostatically mediated fluorescence resonance energy transfer (FRET) signal amplification strategy. In the presence of AFB1, the aptamer preferentially bound to AFB1, resulting in the aggregation of bare gold nanoparticles (AuNPs) induced by NaCl, accompanied by a change of AuNP solution from wine-red to purple. This color change was used for colorimetric channel analysis. Then, the positively charged quantum dots were introduced into reaction system and interacted with negatively charged AuNPs, which successfully converted the color signal into a more sensitive fluorescence signal through FRET. The fluorescence quenching efficiency decreased with increasing concentrations of AFB1, and the fluorescence of aptasensor gradually recovered. Thevariation of fluorescence intensity was employed for fluorometric channel analysis. Under the optimal conditions, the color and fluorescence signals exhibited excellent response to AFB1 concentration within the ranges 10-320 ng·mL-1 and 3-320 ng·mL-1,respectively, and the limit of detection was as low as 7.32 ng·mL-1 and 1.48 ng·mL-1, respectively. The proposed aptasensor exhibited favorable selectivity, good recovery (85.3-113.4% in spiked corn and wheat samples), stable reproducibility (RSD<13.3%), and satisfactory correlation with commercial kits (R2=0.998). The aptasensor developed integrates advantages of modification-free, dual-readout, self-calibration, easy operation, and cost-effectiveness, while providing a simple and universal strategy for rapid and sensitive detection of mycotoxins in foodstuffs.

DNA tetrahedral scaffold-corbelled 3D DNAzyme walker for electrochemiluminescent aflatoxin B1 detection

The reaction efficiency of surface-based DNA walker can directly affect the properties of a biosensor. Herein, three-dimensional (3D) DNAzyme walker were first fixed on the top of DNA tetrahedral scaffold to improve the immobilization efficiency. Ferrocene (Fc) that labeled at substrate strand ends effectively quenched the electrochemiluminescence (ECL) signal of Ru(bpy)2(cpaphen)2+, yielding the sensor in a “signal-off” state. Upon the addition of aflatoxin B1 (AFB1), 3D DNAzyme walker was activated and fueled by Na+, accordingly releasing Fc and recovering the ECL signal of Ru(bpy)2(cpaphen)2+. Due to the high movement efficiency of such 3D DNAzyme walker, ultrasensitive detection of AFB1 was achieved in the range of 1.0 fg mL−1–10 ng mL−1, with a detection limit of 0.58 fg mL−1. Moreover, satisfactory results were obtained while detecting AFB1 in corn and peanut samples, suggesting it has a potential application in food safety analysis.

Determination of aflatoxin B1 value in corn based on Fourier transform near-infrared spectroscopy: Comparison of optimization effect of characteristic wavelengths

Aflatoxin B1 (AFB1) is an important cause of human liver cancer. This study proposes a quantitative detection method for the AFB1 in corn based on Fourier transform near-infrared (FT-NIR) spectroscopy technology. First, we acquired spectral data of corn samples with different degrees of mildew using FT-NIR spectrometer; then, we used the ant colony optimization (ACO) and the NSGA-Ⅱ algorithms to optimize the characteristic wavelengths of the spectra after SNV treatment respectively; Finally, the back propagation neural network (BPNN) models were established using the optimized characteristic wavelengths to realize the accurate detection of the AFB1 in corn. The results obtained showed that the prediction performance of the BPNN model established using the four characteristic wavelength variables optimized by NSGA-Ⅱ algorithm is the best, and the best NSGA-Ⅱ-BPNN model's correlation coefficient of prediction (RP) is 0.9951, the root mean square error of prediction (RMSEP) is 1.5606 μg ⋅ kg−1. The overall results demonstrate that the quantitative detection of AFB1 in corn by FT-NIR technique is feasible; in addition, the NSGA-Ⅱ algorithm has its unique advantages in the optimization of spectral characteristics, and it can obtain characteristic wavelength variables with strong pertinence and a small number.

Ratiometric Luminescence Aptasensor Based on Dual-Emissive Persistent Luminescent Nanoparticles for Autofluorescence- and Exogenous Interference-Free Determination of Trace Aflatoxin B1 in Food Samples.

Sensitive and accurate determination of aflatoxin B1 (AFB1) is of great significance to food safety and human health as it is recognized as the most toxic mycotoxin and carcinogenic. Herein, we report a ratiometric luminescence aptasensor based on dual-emissive persistent luminescent nanoparticles (PLNP) for the accurate determination of trace AFB1 in complex food samples without autofluorescence and exogenous interference. Dual-emissive PLNP ZnGa2O4:Cr0.0001 was prepared first and acted as the donor for energy transfer as well as the signal unit with phosphorescence at 714 and 508 nm (the detection and the reference signal, respectively). AFB1 aptamer was then bonded on the surface of PLNP to offer specific recognition ability. Aptamer complementary DNA modified with Cy5.5 was employed as the acceptor for energy transfer and the quenching group to eventually develop a turn-on ratiometric luminescence aptasensor. The developed ratiometric luminescence aptasensor combined the merits of long-lasting luminescence, in situ excitation and autofluorescence-free of PLNP, exogenous interference-free and self-calibration reading of ratiometric sensor, as well as the high selectivity of aptamer, holding great promise for accurate determination of trace AFB1 in complex matrix. The developed ratiometric aptasensor exhibited excellent linearity (0.05-70 ng mL-1), low limit of detection (0.016 ng mL-1), and good precision (2.3% relative standard deviation for 11 replicate determination of 1 ng mL-1 AFB1). The proposed ratiometric aptasensor was successfully applied for the determination of AFB1 in corn, wheat, peanut, millet, oats, and wheat kernels with recoveries of 95.1-106.5%.

Input features and parameters optimization improved the prediction accuracy of support vector regression models based on colorimetric sensor data for detection of aflatoxin B1 in corn

A new method for quantitative detection of aflatoxin B1 (AFB1) in corn based on colorimetric sensor technology was proposed in this study. First, we chose 12 kinds of color sensitive materials to make the colorimetric sensor array. The prepared colorimetric sensor array was used to collect the olfactory sensory information of corn samples with different degrees of mildew, and the information was characterized in the form of images, and using a new unsupervised feature selection with multi-subspace randomization and collaboration (SRCFS) algorithm combined with support vector machine regression (SVR) to optimize the image features of the colorimetric sensor to determine the best color components combination. The SVR model was established by using the best color components combination to achieve rapid quantitative analysis of the AFB1 in corn; in the process of SVR model calibration, optimization of SVR parameters C and g using particle swarm optimization (PSO). The research results showed that compared with the PSO-SVR model, the mean of correlation coefficient of prediction (RP) of the SRCFS-PSO-SVR model has increased from 0.97 to 0.98, and the mean of root mean square error of prediction (RMSEP) has decreased from 4.8 μg·kg−1 to 3.5 μg·kg−1; the RP of the best SRCFS-PSO-SVR model was 0.99 and the RMSEP was 2.8 μg·kg−1. The results reveal that the quantitative detection of the AFB1 in corn can be achieved by using colorimetric sensor technology combined with chemometric methods. Moreover, the SRCFS algorithm can efficiently find the feature combination of colorimetric sensor.

Corn silage as a source of aflatoxin B1 in feed for dairy cattle

Nutrition of dairy cattle is based on two components, concentrates and forages. The main forages in Vojvodina, north province of Serbia is silage made from the whole plant of corn. After the outbreak of aflatoxin B1 in corn in 2012, the occurrence of aflatoxin B1 in corn as a source of contamination of aflatoxin M1 in milk was very broadly investigated. There is no data regarding the occurrence of aflatoxin B1 in silage and how much silage can contribute to the overall intake of aflatoxin B1 in this region. This work is an attempt to estimate how much silage, in condition and practice used in Vojvodina, contributes to the intake of aflatoxin B1, and consequently aflatoxin M1 in milk. In total, 82 samples of corn grain and 72 samples of corn silage were analyzed on the occurrence of aflatoxin B1 during 2017-2018 period. Aflatoxin B1 was found in 13.41% of corn samples in the range from 6.82 to 187.5 ppb (average 63.5 ppb). All positive samples were from 2017, while no positive samples were found during 2018. Incidence of aflatoxin B1 in silage was 54.17% in the range of 3.5-58.0 ppb (12% moisture content) or 0.95-16.1 ppb in the fresh matter. Results suggest that silage can be a significant factor to overall intake of aflatoxin B1 and that further research is needed.

Direct competitive ELISA enhanced by dynamic light scattering for the ultrasensitive detection of aflatoxin B1 in corn samples

Compared with absorbance, scattering-based dynamic light scattering (DLS) signal has higher sensitivity because its light-scattering intensity is very sensitive to changes in size, thereby enhancing the sensitivity. Herein, we first developed a DLS-enhanced direct competitive enzyme-linked immunosorbent assay (DLS-dcELISA) for ultrasensitive detection of aflatoxin B1 (AFB1) in corn. By using hydroxyl radical-induced gold nanoparticle (AuNP) aggregation to amplify AuNP scattering signals, the developed DLS-dcELISA exhibited ultrahigh sensitivity for AFB1. The detection limit was 0.12 pg mL−1, which was 153- and 385-fold lower than those obtained using plasmonic and colorimetric dcELISA. In addition, the DLS-dcELISA exhibited excellent selectivity, high accuracy, and strong practicality. Overall, this work presented a simple and universal strategy for improving the sensitivity of traditional ELISA platform only by using the sensitive DLS signals. This technique can replace absorbance-based plasmonic or colored signals as immunoassay signal output for enhanced competitive detection of mycotoxins.

Detection and quantification of Aflatoxin B1 in corn and corn-grown soils in the district of Anuradhapura, Sri Lanka

Aflatoxin B1 contamination adversely affects human health by impairing long-term physical and cognitive development. Several crops have been associated with aflatoxin B1 contamination and corn is one of them. In the Anuradhapura district of the North Central Province of Sri Lanka, corn is one of the main agricultural produce. Due to poor farming practices in this area, it is possible that aflatoxin B1 is somehow transported from soil to the corn ears. This study was carried out to detect and quantify aflatoxin B1 in corn and corn-grown soils in Anuradhapura. Corn (n = 60) and corn-grown soil (n = 60) samples were randomly collected from 20 minor-scale corn-grown fields with three random replicates. Each sample was prepared for the measurement of aflatoxin B1 levels using the Enzyme-Linked Immunosorbent Assay (ELISA). Though 20 ppb is considered as the poisonous or deleterious level for corn consumption, there were toxin contaminations of up to 60–70 ppb in the corn kernel, while majority of soil had 350–400 ppb of aflatoxin B1 levels. Fifteen corn samples had exceeded the acceptable level while 22 samples were free of aflatoxin B1 and 23 samples were within the acceptable level. The results showed that the presence of aflatoxin B1 in corn is not habitually distributed throughout Anuradhapura district and it increased with the soil aflatoxin B1 concentration. It appears that there is a relationship between corn kernel and corn-grown soil aflatoxin B1 levels.

Reduction of Aflatoxin B1 in Corn by Water-Assisted Microwaves Treatment and Its Effects on Corn Quality.

Aflatoxin B1 (AFB1) is one of the most commonly found mycotoxin in corn, which is highly toxic, carcinogenic, teratogenic, and mutagenic for the health of humans and animals. In order to reduce the AFB1 in corn, corn kernels were processed with Water-assisted Microwaves Treatment (WMT) and the feasibility of WMT processing on AFB1 reduction and its effects on corn quality were analyzed. Increasing the treatment time and microwave power could increase the reduction of AFB1, and the maximum reduction rate could reach 58.6% and 56.8%, respectively. There was no significant correlation between the initial concentration of AFB1 and the reduction rate of AFB1. During WMT, the main toxigenic molds were sterilized completely, and the moisture content of corn climbed up and then declined to the initial level. WMT could obviously increase the fatty acid value and pasting temperature of corn and reduce the all paste viscosity of corn. However, it had little effect on the color of corn. The results indicated that WMT could reduce AFB1 effectively and avoid the vast appearance of heat-damaged kernels simultaneously. Undoubtedly, water played an important role in WMT. This result provides a new idea for the reduction of AFB1 by microwave.

Detoxification of aflatoxin B1 in corn by chlorine dioxide gas

Chlorine dioxide (ClO2) gas was utilized for detoxifying aflatoxin B1 (AFB1) in corn for the first time. Four degradation compounds were identified by LC–MS as C17H13O8, C17H15O10, C16H15O10, and C15H11O8. Structurally, the biological activity of ClO2-treated AFB1 was removed due to the disappearance of C8-C9 double bond in the furan ring and the modification of cyclopentanone and methoxy after ClO2 treatment. The cell viability assay on human embryo hepatocytes confirmed little toxicity of the degradation products. The degradation efficiency of AFB1 on corn peaked near 90.0% under the optimized conditions and reached 79.6% for low initial contamination of AFB1 at 5–20 μg/kg. Accordingly, ClO2 has the potential to be developed into an effective, efficient, and economic approach to detoxify AFB1 in grains.

Rhizopus oligosporus Activity in Crude Extract and Powder Form to Reduce Aspergillus flavus and Aflatoxin Contamination in Corn

Rhizopus oligosporus (RO) in isolate culture was known to reduce contamination toxigenic mold Aspergillus flavus (AF) and aflatoxin B1 in chicken feed. Application in culture form was not effective. The aim of this research was to evaluate RO activities in extract and inoculum form to reduce contamination of AF and aflatoxin B1 in corn. RO was harvested from agar plate, blended, added with water (ratio 1:1 (w/v)) and centrifuged. Supernatant was filtered using Whatman 41. Inoculum was made by inoculation RO in soy powder and incubated at 28oC for 5 days. Inoculum was dried at 40oC for 24-28 hours. Assay was conducted by addition extract or inoculum to corn. Extract and corn ratio were 1:1 (v/w), while inoculum doses were 5, 25, 50, 1000 dan 200 g/kg corn. Assay for aflatoxin B1 was done using kit ELISA aflatoxin. The result of this research showed that extract was able to reduce AF contamination up to 1 log 10, while the less concentration of inoculum which able to inhibit AF up to 6 log 10 was 100 g/kg corn. Extract RO 125 and 250 mL/kg corn was able to reduce aflatoxin contamination by 93.69 % and 85.84 %. Inoculum at dose 5 and 100 g/kg corn was able to reduce aflatoxin 57.58% and 85%. Based on the result, it could be concluded that RO in extract or inoculum form was able to reduce contamination of AF and aflatoxin B1 in corn. Rhizopus as inoculum was easier to be applied than in extract form.

Versicolorin A is a potential indicator of aflatoxin contamination in the granary-stored corn

ABSTRACTThe objective of this study was to evaluate the feasibility of the predictive monitoring of aflatoxin B1 (AFB1) under granary conditions, since mycotoxin contamination of the stored grain represents an important issue. Using the storage test, we investigated the relationship between versicolorin A (Ver A, an intermediate in AFB1 biosynthesis) levels and the levels of aflatoxigenic fungi, and their relationship with aflatoxin production. All samples, except for one, were found to be contaminated with aflatoxigenic fungi using PCR analyses, while their AFB1 levels were not detectable before the storage test using an enzyme-linked immunosorbent assay (ELISA) method with an LOD of 2 μg/kg. Aflatoxigenic fungi levels were analysed, as well as Ver A levels prior to the accumulation of AFB1 (Levels were ≥5 μg/kg; the permissible levels of AFB1 in corn intended for direct consumption are <5 μg/kg (EC)). Statistical analyses demonstrated that aflatoxin levels after both actual storage and safe storage (AFB1˂5μg/kg) times are significantly correlated with the Ver A levels and the changes in Ver A levels (ΔVer A). Both high and variable Ver A levels were indicative of the vigorous metabolic activity of aflatoxigenic fungi. In contrast, steady Ver A levels showed that aflatoxin production by the fungi was not active. Monitoring Ver A levels and their changes may allow an earlier detection of harmful aflatoxin contamination in the stored grain. Additionally, the toxicity of Ver A should be further examined. The results of our study indicate that the monitoring of Ver A levels, even when the AFB1 levels are very low, may increase the safety of grain consumption, especially considering Ver A toxicity.

A novel electrochemical immunosensor for highly sensitive detection of aflatoxin B1 in corn using single-walled carbon nanotubes/chitosan

A sensitive electrochemical immunosensor for aflatoxin B1 (AFB1) detection based on single-walled carbon nanotubes/chitosan was presented. The immunosensor was based on an indirect competitive binding to a fixed amount of anti-AFB1 between free AFB1 and AFB1-bovine serum albumin, which conjugate immobilized on covalently functionalized nanotubes/chitosan laid on the glass carbon electrode. Then, the anti-mouse immunoglobulin G secondary antibody labeled with alkaline phosphatase was bound to the electrode surface through reacting with primary antibody. Finally, alkaline phosphatase catalyzes the hydrolysis of the substrate α-naphthyl phosphate, which produced electrochemical signal. Compared with conventional methods, the established immunosensor was more sensitive and simple. Under optimal conditions, this method could quantitatively detect AFB1 from 0.01 to 100ngmL−1 with a detection limit of 3.5pgmL−1. Moreover, the immunosensor was successfully applied to assay AFB1 in corn powder, which showed good correlation with the results obtained from high performance liquid chromatography.