Detection of aflatoxin M1 in milk products from China by ELISA using monoclonal antibodies

A field-portable electrochemical immunosensor based on a multifunctional Ag2O/g-C3N4@MA-DBB covalent organic framework receptor interface for single-step detection of aflatoxin M1 in raw milk samples

Aflatoxin M1 (AFM1), a hydroxylated metabolite of aflatoxin B1 (AFB1), contaminates milk and dairy products from livestock via ingestion of feed contaminated with a species of Aspergillus. As AFM1 is a Group-II B carcinogen, it is indispensable to develop novel, easy-to-handle, sensitive, portable and cost-effective strategies for its detection. Herein, a covalent organic framework (COF)-based electroactive nanocomposite, Ag2O/g-C3N4-COOH@MA-DBB-COF (silver oxide/carboxy-functionalized graphitic carbon nitride@melamine-dibromo butane COF), is designed to serve as a multifunctional receptor surface. The Ag2O/g-C3N4-COOH@MA-DBB-COF formation was characterized through X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, micro-Raman spectroscopy (RAMAN), dynamic light scattering (DLS) and thermogravimetric analysis (TGA), and each step of the sensor fabrication was monitored using field emission scanning electron microscopy (FE-SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimal conditions, the designed immunosensor permitted the detection of AFM1 in the linear range of 0.03-1000 fg mL-1, with a 0.01 fg mL-1 limit of detection (LOD). The selectivity of the designed immunosensor was validated via an anti-interference study. The practical applicability of the immunosensor was demonstrated by the detection of AFM1 in real milk samples, and good recovery values (97.28-102.62%) were obtained. Furthermore, the developed immunosensor and high-performance liquid chromatography (HPLC) were employed in parallel to detect AFM1 in local market milk samples from twenty different sites to validate the performance of the newly designed immunosensor. Additionally, the designed immunosensor was stable over an extended period of time. This work reports a single-step field-portable multifunctional innovative electrochemical immunoreceptor design for on-site and label-free detection of AFM1 in milk samples. Hence, the present study is the first report on the fabrication of a multifunctional innovative electrochemical immunoreceptor based on PGE/Ag2O/g-C3N4-COOH@MA-DBB-COF for the detection of AFM1 in milk samples.

Occurrence of aflatoxin M1 in cheese products commonly available in Sri Lankan market

Aflatoxins (AFs) are a group of mycotoxins produced by certain fungi of Aspergillus spp. AFs of major concern are B1 (AFB1), B2 (AFB2), G1 (AFG1), G2 (AFG2), and M1 (AFM1). AFM1 is a hydroxylated metabolite of AFB1 formed inside the animal's body which is excreted into milk of cows that consumed AFB1 contaminated feed. Consumption of AFM1-contaminated milk and subsequent dairy products causes negative health effects in consumers. This study was conducted to determine the occurrence and levels of AFM1 in cheese products available in the Sri Lankan market where AFM1 is not regularly monitored in milk while having an outdated regulatory limit of 1 ppb established for dairy products. Processed cheese (n = 28), hard cheese (n = 14), semi-hard cheese (n = 5), and soft cheese (n = 3) representing seven popular brands were collected. The samples were analyzed by Ultra High-Performance Liquid Chromatography Fluorescence Detection. AFM1 was detected in 40 samples (80 %), while 17 (34 %) and 37 (74 %) of the samples had AFM1 levels exceeding the maximum permitted limit set by Codex Alimentarius Commission (0.5 ppb) and the Netherlands (0.2 ppb). Further, 10 samples violated the Sri Lankan maximum limit of 1 ppb. Thirteen out of the 14 hard cheese (92.9 %, 0.11-14.43 ppb) and all semi-hard cheese samples (100 %, 0.29-0.65 ppb) contained AFM1. Most of the soft (66.7 %, 0.35-0.45 ppb) and processed (71.4 %, 0.11-1.35 ppb) cheese samples had AFM1. Most of the locally manufactured cheese products in Sri Lankan market may pose health risks to consumers. The results highlight the significance of regular monitoring of AFM1 in dairy products and the importance of updating regulations on par with international standards concurrently to ensure consumer safety.

FOXM1 Aptamer-Polyethylenimine Nanoplatform Coated With Hyaluronic Acid And AS1411 Aptamer For Dual-Targeted Delivery of Doxorubicin And Synergistic Treatment of Tumor Cells

The objective of this investigation was to develop a self-assembled, dual-functionalized delivery system that could effectively transport doxorubicin (DOX) to cancer cells through the use of AS1411 aptamer and hyaluronic acid polymer (HA). The ultimate goal is an improved targeting approach for more efficient treatment. The core of this system comprised polyethylenimine (PEI) and FOXM1 aptamer, which was coated by HA. Next, nucleolin targeting aptamers (AS1411) were loaded onto the nanocomplex. Afterward, DOX was added to Aptamers (Apts)-HA-PEI-FOXM1 NPs to create the DOX-AS1411-HA-PEI-FOXM1 NPs for better treatment of cancer cells. The cytotoxic effect of the nanocomplex on L929, 4T1, and A549 cells showed that cell mortality in target cancer cells (4T1 and A549) was considerably enhanced compared to nontarget cells (L929, normal cells). The findings from the flow cytometry analysis and fluorescence imaging demonstrated the cellular absorption of DOX-Apts-HA-PEI-FOXM1 NPs in target cells was significantly enhanced when compared to L929 cells. Furthermore, in vivo antitumor study exhibited that DOX-Apts-HA-PEI-FOXM1 NPs rendered specific tumor accumulation and increasing of the anti-tumor effects.

CRISPR-Cas12a-based colorimetric aptasensor for aflatoxin M1 detection based on oxidase-mimicking activity of flower-like MnO2 nanozymes

Given the highly mutagenic and carcinogenic nature of Aflatoxin M1 (AFM1), the quantity assessment of AFM1 residues in milk and dairy products is necessary to maintain consumer health and food safety. Herein, CRISPR-Cas12a-based colorimetric aptasensor was developed using the catalytic activity of flower-like nanozymes of MnO2 and trans-cleavage property of CRISPR-Cas12a system to quantitatively detect AFM1. The basis of the developed colorimetric aptasensor relies on whether or not the CRISPR-Cas12a system is activated, as well as the contrast in oxidase-mimicking capability exhibited by flower-like MnO2 nanozymes when AFM1 is absent or present. When AFM1 is not present in the sample, single-stranded DNA (ssDNA) is degraded by the activated CRISPR-Cas12a, and the solution turns into yellow due to the catalytic activity of the nanozymes. While, in the attendance of AFM1, ssDNA degradation does not occur due to the inactivation of the CRISPR-Cas12a. Therefore, with the adsorption of the ssDNA on the MnO2 nanozymes, their catalytic activity decreases, and the solution color becomes pale yellow due to less oxidation of the chromogenic substrate. In this aptasensor, the relative absorbance changes increased linearly from 6 to 160 ng L-1, and the detection limit was 2.1 ng L-1. The developed aptasensor displays a selective detection performance and a practical application for quantitative analysis of AFM1 in milk samples. The results of the introduced aptasensor open up the way to design other selective and sensitive aptasensors for the detection of other mycotoxins by substitution of the used sequences.

Polystyrene microsphere-mediated optical sensing strategy for ultrasensitive determination of aflatoxin M1 in milk

Aflatoxin M₁ (AFM₁) contamination poses a serious threat to human health globally. Hence, it is necessary to develop reliable and ultrasensitive methods for the determination of AFM₁ residue in food products at low levels. In this study, a novel polystyrene microsphere-mediated optical sensing (PSM-OS) strategy was constructed to solve the problems of low sensitivity and susceptibility to interference from the matrix in AFM₁ determination. Polystyrene (PS) microspheres have the advantages of low cost, high stability, and controllable particle size. They can be useful optical signal probes for qualitative and quantitative analyses attributed to the fact that they have strong ultraviolet-visible (UV-vis) characteristic absorption peaks. Briefly, magnetic nanoparticles were modified with the complex of bovine serum protein and AFM₁ (MNP₁₅₀-BSA-AFM₁), and biotinylated antibodies of AFM₁ (AFM₁-Ab-Bio). Meanwhile, PS microspheres were also functionalized with streptavidin (SA-PS₉₅₀). In the presence of AFM₁, a competitive immune reaction was triggered leading to the changes in AFM₁-Ab-Bio concentrations on the surface of MNP₁₅₀-BSA-AFM₁. The complex of MNP₁₅₀-BSA-AFM₁-Ab-Bio binds with SA-PS₉₅₀ to form the immune complexes due to the special binding of biotin and streptavidin. The remaining SA-PS₉₅₀ in the supernatant was determined by UV-Vis spectrophotometer after magnetic separation, which positively correlated with the concentration of AFM₁. This strategy allows for ultrasensitive determination of AFM₁ with limits of detection as low as 3.2 pg/mL. It was also successfully validated for AFM₁ determination in milk samples, and a high consistency was found with the chemiluminescence immunoassay. Overall, the proposed PSM-OS strategy can be used for the rapid, ultrasensitive, and convenient determination of AFM₁, as well as other biochemical analytes.

Comprehensive Review of Aflatoxin Contamination, Impact on Health and Food Security, and Management Strategies in Pakistan

Aflatoxins (AFs) are the most important toxic, mutagenic, and carcinogenic fungal toxins that routinely contaminate food and feed. While more than 20 AFs have been identified to date, aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1), G2 (AFG2), and M1 (AFM1) are the most common. Over 25 species of Aspergillus have been shown to produce AFs, with Aspergillus flavus, Aspergillus parasiticus, and Aspergillus nomius being the most important and well-known AF-producing fungi. These ubiquitous molds can propagate on agricultural commodities to produce AFs in fields and during harvesting, processing, transportation, and storage. Countries with warmer climates and that produce foods susceptible to AF contamination shoulder a substantial portion of the global AF burden. Pakistan's warm climate promotes the growth of toxigenic fungi, resulting in frequent AF contamination of human foods and animal feeds. The potential for contamination in Pakistan is exacerbated by improper storage conditions and a lack of regulatory limits and enforcement mechanisms. High levels of AFs in common commodities produced in Pakistan are a major food safety problem, posing serious health risks to the population. Furthermore, aflatoxin contamination contributes to economic losses by limiting exports of these commodities. In this review, recent information regarding the fungal producers of AFs, prevalence of AF contamination of foods and feed, current regulations, and AF prevention and removal strategies are summarized, with a major focus on Pakistan.

Comparative Evaluation of Three Commercial Elisa Kits Used for the Detection of Aflatoxins B1, B2, G1, and G2 in Feedstuffs and Comparison with an HPLC Method

Various analytical techniques for detecting mycotoxins have been developed in order to control their concentration in food and feed. Conventional analytical approaches for mycotoxin identification include thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), and gas chromatography (GC). Rapid methods for mycotoxin analysis are also becoming increasingly relevant. One of the most common rapid methods for determining these compounds is the enzyme-linked immunosorbent assay (ELISA). The current study aimed to compare three available ELISA kits for the detection and quantification of aflatoxins B₁, B₂, G₁, and G₂ in spiked feed samples at known quantities. All three ELISA kits were validated and showed good performance with high recovery rates and LOD and LOQ values lower than the MRL. The developed HPLC-FL method was validated for all the compounds determining the accuracy, precision, linearity, decision limit, and detection capability with fairly good results. Unknown feed samples (corn, silage, pellet, barley, wheat, soya, and sunflower) were also tested using the best ELISA kit and HPLC, and the results were compared. Both ELISA and HPLC were proven to be suitable methods for mycotoxin analysis. The analytical technique should be determined primarily by the availability and number of samples.

Lactoferrin Alleviated AFM1-Induced Apoptosis in Intestinal NCM 460 Cells through the Autophagy Pathway

Aflatoxin M1 (AFM1) is the only mycotoxin with maximum residue limit in milk, which may result in serious human diseases. On the contrary, lactoferrin (Lf) is an active protein with multiple functions. Studies have confirmed that Lf has a powerful potential to protect the intestines, but the influence of Lf on mycotoxins is not clear. This study aims to explore whether Lf can protect the cytotoxicity induced by AFM1, and determine the underlying mechanisms in human normal colonic epithelial NCM460 cells. The results indicated that AFM1 decreased the cell viability, and increased the levels of apoptosis and autophagy of NCM460 cells. Lf can alleviate the cytotoxicity induced by AFM1 through enhancing cell viability, significantly down-regulated the expression of apoptotic genes and proteins (BAX, caspase3, caspase9, caspase3, and caspase9), and regulated the gene and protein expression of autophagy factors (Atg5, Atg7, Atg12, Beclin1, ULK1, ULK2, LC3, and p62). Furthermore, interference of the key gene Atg5 of autophagy can reduce AFM1-induced apoptosis, which is consistent with the role of Lf, implying that Lf may protect AFM1-induced intestinal injury by inhibiting excessive autophagy-mediated apoptosis. Taken together, our data indicated that Lf has a mitigating effect on apoptosis induced by AFM1 through the autophagy pathway.

A novel colorimetric aptasensor for ultrasensitive detection of aflatoxin M1 based on the combination of CRISPR-Cas12a, rolling circle amplification and catalytic activity of gold nanoparticles

Colorimetric approaches have received noticeable attention among sensing methods in view of simplicity and watching the color change of sample by the naked eyes. However, developing colorimetric sensing methods which show high sensitivity is still problematic. Herein, based on CRISPR-Cas12a, rolling circle amplification (RCA) and catalytic activity of gold nanoparticles (AuNPs), a colorimetric aptasensor was introduced for highly sensitive detection of aflatoxin M₁ (AFM₁). In the presence of AFM₁, the CRISPR-Cas12a is inactivated and large single-stranded DNA (ssDNA) structures are formed on the surface of AuNPs following the addition of T4 DNA ligase and phi29 DNA polymerase. So, the sample color remains yellow after addition of 4-nitrophenol. However, no huge DNA structure is observed on the surface of AuNPs in the absence of target because of activation of CRISPR-Cas12a and digestion of primer. So, the color of sample switches to colorless. The results indicated that the biosensor had high selectivity toward AFM₁ and the approach achieved a detection limit as low as 0.05 ng/L. In addition, it could sensitively identify AFM₁ in the spiked milk samples. Overall, this approach is highly sensitive and does not require sophisticated equipment. Therefore, it maintains promising potential for other mycotoxins detection in real samples by simply replacing the applied sequences.

Determination of Aflatoxin M1 in Raw Milk Using an HPLC-FL Method in Comparison with Commercial ELISA Kits-Application in Raw Milk Samples from Various Regions of Greece

The highly toxic Aflatoxin M1 (AFM1) is most often detected in milk using an Enzyme-Linked-Immunosorbent Assay (ELISA) for screening purposes, while High-Performance Liquid Chromatography with Fluorescence Detector (HPLC-FL) is the reference method used for confirmation. The aim of the present study was the comparison between three commercially available ELISA kits and a newly developed HPLC-FL method for the determination of the AFM1 in milk samples. The developed HPLC-FL method was validated for the AFM1 and Aflatoxin M2 (AFM2), determining the accuracy, precision, linearity, decision limit, and detection capability with fairly good results. All three ELISA kits were also validated and showed equally good performance with high recovery rates. Moreover, the Limit Of Detection (LOD) and Limit Of Quantification (LOQ) values were found to be significantly lower than the Maximum Residue Limit (MRL) (50 ng kg-1). After the evaluation of all three commercial kits, the ELISA kit with the optimum performance along with the HPLC method was used for the determination of AFM1 in raw cow's, goat's, and sheep's milk samples (396) obtained from producers in different regions of Greece. The evaluation of both methods showed that this ELISA kit could be considered as a faster and equally reliable alternative method to HPLC in routine analysis for the determination of AFM1 in milk.

Combination of solvent extraction with deep eutectic solvent based dispersive liquid-liquid microextraction for the analysis of aflatoxin M1 in cheese samples using response surface methodology optimization

A new extraction procedure based on combination of a solvent extraction and deep eutectic solvent based dispersive liquid-liquid microextraction has been introduced for the extraction of aflatoxin M₁ from cheese samples. In this method, acetonitrile, deionized water, and n-hexane are added onto the sample and vortexed. Owning to different affinities of the substances in cheese toward the mentioned solvents, an efficient and selective extraction of the analyte is done in the acetonitrile phase. After centrifugation, the acetonitrile phase is removed and mixed with a new hydrophobic deep eutectic solvent prepared from N,N-diethanol ammonium chloride and carvacrol as an extraction solvent. The mixture is injected into deionized water, and a cloudy solution is obtained. Eventually, an aliquot of the organic phase is injected into high-performance liquid chromatography-fluorescence detection. After optimizing the effective parameters with the response surface methodology and a quadratic model, limits of detection and quantification were 0.74 and 2.56 ng/kg, respectively. The obtained extraction recovery and enrichment factor were 94% and 94, respectively. Also, intra- (n = 6) and interday (n = 4) precisions were less than or equal to 8.6% at a concentration of 5 ng/kg. The suggested method was applied to determine aflatoxin M₁ in different cheese samples.

Aflatoxin M1 detection by ELISA in raw and processed milk in Bangladesh

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Immunologically aflatoxin M1 was detected in raw and processed milk in Bangladesh.

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Aflatoxin M1 mean level was found to be highest in raw milk (699.07 ng/kg).

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EC and US regulations exceeded in 75 % and 43 % of contaminated samples, respectively.

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Aflatoxin M1 existence level in milk can be detrimental to human health.

An analysis was accomplished to get information regarding presence of highly toxic and carcinogenic aflatoxin M1 (AFM1) in raw and processed samples of milk applying ELISA (enzyme linked immunosorbent assay). Investigation of a set of 100 samples (n=100) taken from different regional small-scale farms as well as grocery stores of Bangladesh containing three groups of milk including raw (n=50), pasteurized (n=25) and UHT (n=25), exhibited in total 53% AFM1 contamination where 70% contamination was found in raw milk ranging from 22.79−1489.28 ng/kg (mean value 699.07 ng/kg), 52% in pasteurized milk ranging from 18.11−672.18 ng/kg (mean value 99.77 ng/kg) and 20% in UHT milk ranging from 25.07−48.95 ng/kg (mean value 35.46 ng/kg). Among all the positive samples, 75% contaminated samples were above the European Communities prescribed limits (50 ng/kg) while having 25% samples still below this limit whereas 43% samples crossed the accepted limit of US regulations/Codex Alimentarius Commission regulations (500 ng/kg). Thus the findings of this study may lead to increase awareness regarding health impact of aflatoxin M1 and implementation of strict regulations by law enforcement bureaus of Bangladesh.

A Sensitive Two-Analyte Immunochromatographic Strip for Simultaneously Detecting Aflatoxin M1 and Chloramphenicol in Milk

A two-analyte immunochromatographic strip (immunostrip) was developed for the simultaneous detection of aflatoxin M1 (AFM1) and chloramphenicol (CAP) in milk. Protein conjugates (AFM1-ovalbumin (OVA) and CAP-OVA) and goat anti-rabbit IgG were respectively drawn on nitrocellulose membrane as two test lines (T₁ and T₂) and a control line (C). The immunostrip was dipped into a well that contained a 200 μL milk sample, 5 μL AFM1 antibody-gold conjugates, and 8 μL CAP antibody-gold conjugates; the whole assay was completed in 15 min and the results could be interpreted visually or using a reader. This immunostrip has cut-off levels of 0.1 ng/mL and 0.5 ng/mL for AFM1 and CAP, respectively. Analysis of CAP and AFM1 in milk samples revealed that data from the immunostrip test agreed closely with those obtained from ELISA. The two-analyte immunostrip is a rapid way for on-site simultaneous detection of AFM1 and CAP in milk.

Current research and prevention of aflatoxins in China

Since their discovery in the 1960s, aflatoxins were found to have a considerable impact on the health of humans and animals as well as the country’s economy and international trade. Aflatoxins are often found in nuts, cereals and animal feeds, which has a significant danger to the food industry. Over the years, several steps have been undertaken worldwide to minimise their contamination in crops and their exposure to humans and animals. China is one of the largest exporters and importers of food and animal feed. As a result, many studies have been carried out in China related to aflatoxins, including their distribution, pollution, detection methods, monitoring, testing and managing. Chinese scientists studied aflatoxins in microbiological, toxicological, ecological effects as well as policies relating to their controlling. China has thus put into practice a number of strategies aiming at the prevention and control of aflatoxins in order to protect consumers and ensure a safe trade of food and feed, and the status and enlargement of these strategies are very important and useful for many consumers and stakeholders in China. Therefore, this article aims at the detriment assessments, regulations, distribution, detection methods, prevention and control of aflatoxins in China. It equally provides useful information about the recent safety management systems in place to fight the contamination of aflatoxins in food and feed in China.

Development of an Escherichia coli-based electrochemical biosensor for mycotoxin toxicity detection

Mycotoxin contamination in food and feed is a global concern because mycotoxin contamination can cause both acute and chronic health effects in humans and animals. In the present work, an Escherichia coli-based biosensor is described for the toxicity assessment of aflatoxin B₁ (AFB₁) and zearalenone (ZEN). In this electrochemical biosensor, E. coli is used as the signal recognition element, p-benzoquinone is used as the mediator, and a two-step reaction procedure has been developed to separate the mediator from the mycotoxins. The current value of the as-prepared microbial biosensor exhibits a linear decrease with concentrations of AFB₁ and ZEN in the range of 0.01-0.3 and 0.05-0.5 μg/mL, with detection limits reaching 1 and 6 ng/mL, respectively. The IC₂₅ values obtained by the present method are 0.25 and 0.40 μg/mL for AFB₁ and ZEN, which shows that the cytotoxicity of AFB₁ to E. coli is more severe than the cytotoxicity of ZEN to E. coli. The combined toxic effect of these two mycotoxins has also been explored, and synergistic biotoxicity has been observed. Moreover, the biosensor is successfully applied to the toxicity evaluation of mycotoxins in real samples, including peanut and corn oils. This work could provide new insight into mycotoxin and microorganism interactions and could establish a new approach for future mycotoxin detection.

An electrochemical immunosensor based on a combined amplification strategy with the GO–CS/CeO2–CS nanocomposite for the detection of aflatoxin M1

Herein, a sensitive electrochemical immunosensor modified with graphene oxide–chitosan (GO–CS) and cerium oxide–chitosan (CeO₂–CS) using screen-printed electrodes (SPEs) was developed for the determination of aflatoxin M₁(AFM₁) in milk.

Occurrence and Seasonal Variations of Aflatoxin M1 in Milk from Punjab, Pakistan

The manifestation of aflatoxins in feed and food is a major issue in the world as its presence leads to some health problems. This study investigates the incidence of aflatoxin M₁ (AFM₁) contamination in raw milk samples which were collected from Punjab, Pakistan. The Cluster Random Sampling technique was used to collect 960 milk samples from five different regions, and samples were collected every month. The AFM₁ level in raw milk was analyzed by the ELISA technique. The findings demonstrate that 70% of samples exceeded the United States permissible maximum residue limits (MRL 0.50 µg/L), with an overall AFM₁ level that ranged from 0.3 to 1.0 µg/L. AFM₁ contamination varied with the season: The highest average contamination was detected in winter (0.875 µg/L), followed by autumn (0.751 µg/L), spring (0.654 µg/L), and summer (0.455 µg/L). The Eastern region exhibited the highest average AFM₁ contamination (0.705 µg/L). Milk samples from the Northern region were found to be widely contaminated, as 86.9% samples exceeded the US MRL, followed by the Eastern region, with 72.3% samples being contaminated with >0.5 µg/L AFM₁. The study indicated that the raw milk supply chain was heavily contaminated. Recommendations and remedial measures need to be developed by regulatory authorities to improve the raw milk quality.

A Novel Graphene Oxide-Based Aptasensor for Amplified Fluorescent Detection of Aflatoxin M1 in Milk Powder

In this paper, a rapid and sensitive fluorescent aptasensor for the detection of aflatoxin M1 (AFM1) in milk powder was developed. Graphene oxide (GO) was employed to quench the fluorescence of a carboxyfluorescein-labelled aptamer and protect the aptamer from nuclease cleavage. Upon the addition of AFM1, the formation of an AFM1/aptamer complex resulted in the aptamer detaching from the surface of GO, followed by the aptamer cleavage by DNase I and the release of the target AFM1 for a new cycle, which led to great signal amplification and high sensitivity. Under optimized conditions, the GO-based detection of the aptasensor exhibited a linear response to AFM1 levels in a dynamic range from 0.2 to 10 μg/kg, with a limit of detection (LOD) of 0.05 μg/kg. Moreover, the developed aptasensor showed a high specificity towards AFM1 without interference from other mycotoxins. In addition, the technique was successfully applied for the detection of AFM1 in infant milk powder samples. The aptasensor proposed here offers a promising technology for food safety monitoring and can be extended to various targets.

Multi-mycotoxins analysis in liquid milk by UHPLC-Q-Exactive HRMS after magnetic solid-phase extraction based on PEGylated multi-walled carbon nanotubes

A simple and rapid magnetic solid-phase extraction (MSPE) method using PEGylated multi-walled carbon nanotubes magnetic nanoparticles (PEG-MWCNTs-MNP) as absorbents is proposed for isolation and enrichment of aflatoxin B₁ (AFB₁), aflatoxin B₂ (AFB₂), aflatoxin G₁ (AFG₁), aflatoxin G₂ (AFG₂), aflatoxin M₁ (AFM₁), aflatoxin M₂ (AFM₂), ochratoxin A (OTA), zearalenone (ZEA), zearalanone (ZAN), α-zeralanol (α-ZAL), β-zeralanol (β-ZAL), α-zeralenol (α-ZOL), and β-zeralenol (β-ZOL) from liquid milk. Combined with ultra-high performance liquid chromatography Q-Exactive high resolution mass spectrometry, simultaneous qualification of these mycotoxins was achieved with sensitivity and specificity. The proposed method showed a good linearity (R² ≥ 0.995), high sensitivity (limit of detection in the range of 0.005-0.050 μg/kg and limit of quantification in the range of 0.015-0.150 μg/kg), adequate recovery (81.8-106.4%), and good repeatability (intra-day precision in the range of 2.1-8.5% and inter-day precision in the range of 3.9-11.7%). It has been successfully applied to the determination of 13 mycotoxins in real liquid milk samples.

Determination of aflatoxin M1 using an aptamer-based biosensor immobilized on the surface of dendritic fibrous nano-silica functionalized by amine groups

Aflatoxins are potential food pollutants produced by fungi. Among them, aflatoxin M1 (AF M1) is the most toxic. A great deal of concern is associated with AF M1 toxicity. Aflatoxins are potential food pollutants produced by fungi. Among them, aflatoxin M1 (AF M1) is the most toxic. A great deal of concern is associated with AF M1 toxicity. In the present work, a novel aptamer-based bioassay was developed for monitoring aflatoxin M1 (AF M1) in real samples. A chitosan-modified graphene quantum dot (GQD-CS) nanocomposite was used as a biocompatible substrate coated with dendritic fibrous nanosilica functionalized by amine groups (KCC-1-NH₂-Tb). Accordingly, an innovative biocompatible polymeric matrix was prepared for aptamer immobilization. The unique oligonucleotide of AF M1 (5'-ATC CGT CAC ACC TGC TCT GAC GCT GGG GTC GAC CCG GAG AAA TGC ATT CCC CTG TGG TGT TGG CTC CCG TAT) labelled by toluidine blue was immobilized on the engineered interface. Hence, a novel aptamer-based bioassay was formed for the highly sensitive quantitation of AF M1 using cyclic voltammetry and differential pulse voltammetry techniques. The structure and morphology of GQDs-CS/KCC-1-NH₂-Tb was investigated by Fourier transform infrared spectroscopy, X-ray diffraction, atomic force and scanning electron microscopy and energy-dispersive X-ray spectroscopy. The toxicity tests, which were performed by MTT assays, revealed the biocompatible nature of KCC-1-NH₂-Tb. The engineered aptasensor demonstrated excellent behaviour toward the determination of AF M1, where the low limit of quantification was 10 fM. The proposed aptamer-based bioassay was successfully used for the monitoring of AF M1 in milk samples. This work provides a beneficial reference for the sensing of other toxins in food/pharmaceutical assays and veterinary medicine.

Assorted Methods for Decontamination of Aflatoxin M1 in Milk Using Microbial Adsorbents

Aflatoxins (AF) are carcinogenic metabolites produced by different species of Aspergillus which readily colonize crops. AFM1 is secreted in the milk of lactating mammals through the ingestion of feedstuffs contaminated by aflatoxin B1 (AFB1). Therefore, its presence in milk, even in small amounts, presents a real concern for dairy industries and consumers of dairy products. Different strategies can lead to the reduction of AFM1 contamination levels in milk. They include adopting good agricultural practices, decreasing the AFB1 contamination of animal feeds, or using diverse types of adsorbent materials. One of the most effective types of adsorbents used for AFM1 decontamination are those of microbial origin. This review discusses current issues about AFM1 decontamination methods. These methods are based on the use of different bio-adsorbent agents such as bacteria and yeasts to complex AFM1 in milk. Moreover, this review answers some of the raised concerns about the binding stability of the formed AFM1-microbial complex. Thus, the efficiency of the decontamination methods was addressed, and plausible experimental variants were discussed.

Immunotoxicity of aflatoxin M1 : as a potent suppressor of innate and acquired immune systems in a subacute study

BACKGROUND

Although, to date, there have been several in vitro and in vivo studies of immunomodulatory effects of aflatoxin M₁ (AFB₁ ), little is known about the effect of AFM₁ on various aspects of innate and acquired immunity. In the present study, AFM₁ was administered intraperitoneally, at doses of 25 and 50 μg kg^-1 , body mass for 28 days and various immunological parameters were measured.

RESULTS

Several parameters related to immune function were suppressed: organ mass, cellularity of spleen, proliferation response to lipopolysaccaride and phytohemagglutinin-A, hemagglutination titer, delayed type of hypersensitivity response, spleen cell subtypes, serum hemolytic activity, serum immunoglobulin G level and cytokine production. AFM₁ did not cause changes in body mass, hematological parameters or the concentration of immunoglobulin M in blood serum.

CONCLUSIONS

Overall, the data suggested that AFM₁ suppressed innate and acquired immunity. Therefore, with respect to consumer safety, it is extremely important to further control the level of AFM₁ in milk, and this should be considered as a precedence for risk management actions. © 2018 Society of Chemical Industry.

Design of a redox-active surface for ultrasensitive redox capacitive aptasensing of aflatoxin M1 in milk

Herein, we report the design of a novel label-free aptasensor based on ferrocene and silicon nanoparticles (SiNPs) for ultrasensitive detection of aflatoxin M1 (AFM1) in milk. Given that silicon nanomaterials stand out by their high capacitive power, we used them to develop a novel capacitive transduction system based on electrochemical capacitance spectroscopy (ECS). This strategy relies on the changes of the redox capacitance signal owed to the surface-tethered ferrocene film, by performing electrochemical impedance spectroscopy (EIS) measurements without using an external redox probe. The redox capacitance variation was found to correlate well with the increasing concentrations of AFM1 in the linear range from 10 to 500 fmol⋅L^-1 with a sensitivity of 0.46 μF*fM-1*cm - 2. Furthermore, the aptasensor allowed to reach very low limits of detection and quantification equal to 4.53 fM and 14.95 fM, respectively. The platform revealed a high selectivity toward the target analyte, and it was applied to quantify very low concentrations of AFM1 in commercial pasteurized milk. Finally, the results of real sample analysis were successfully gauged against those obtained using commercially available enzyme-linked immunoassay (ELISA) kits.

Evaluation of different competitive immunoassays for aflatoxin M1 determination in milk samples by means of inductively coupled plasma mass spectrometry

Haptens (i.e. biomolecules which molecular weight is lower than 10 kDa) determination by inductively coupled plasma mass spectrometry (ICP-MS) is usually performed by means of competitive immunoassays. In these immunoassays, analyte quantification is indirectly carried out using two different tracer species (i.e. antibodies or antigen-protein conjugates). However, the benefits (and drawbacks) derived from using a given tracer species have not been systematically investigated so far. The goal of this work is to evaluate the influence of the tracer species employed in competitive immunoassays on the analytical figures of merit for aflatoxin M₁ (AFM₁) determination in milk samples. To this end, three different strategies have been developed and evaluated, namely: (i) antibody binding inhibition assay (ABIA); (ii) capture inhibition assay (CIA); and (iii) capture bridge inhibition assay (CBIA). Experimental results show that the use of the antibody as tracer species (as in the ABIA approach) affords better analytical figures of merit for AFM₁ determination than using the antigen-protein conjugate as the tracer one (as in the CIA and CBIA strategies). The limit of detection afforded by ABIA strategy (i.e. 0.1 ng kg^-1) for AFM₁ determination was 1000-fold and 50-fold lower regarding the CIA and CBIA strategies, respectively. In the case of the ABIA approach, the characteristics of the metal nanoparticle label employed to detect the tracer species is critical on the analytical figures of merit. However, when the hapten-protein conjugates are used as tracer species, immunocomplex formation is severely hampered by steric effects caused by the protein moiety and, consequently, the characteristics of the metal nanoparticle label is not critical in the immunoassay performance. The different immunoassay strategies were successfully validated for AFM₁ determination in milk samples using a certified reference material of whole milk powder (ERM-BD283) according to European Conformity guidelines for analytical methods of food contaminants and mycotoxins. Compared to ELISA, the immunoassay developed for AFM₁ determination in milk samples improve limits of detection up to 10-fold.

Rapid detection of four mycotoxins in corn using a microfluidics and microarray-based immunoassay system

Mycotoxins threaten human health seriously because they usually exist in food, fodder and commodities. In this study, a rapid and sensitive immunoassay system for commonly encountered mycotoxins was established based on microfluidics and protein microarrays. Four mycotoxins (T-2 toxin, aflatoxin B1, ochratoxin A, and zearalenone) can be automatically detected in a custom-made microdevice within 30 min under the assistance of a prototype of the instrument with a fluid control system and an imaging system. Once the microdevices are fabricated, they are small-sized and user-friendly. Standard curves for each of the studied mycotoxins were generated with a good logistic correlation (R² > 0.98). Working ranges from 0.1 to 20 ng/ml were employed in the immunoassay being the limit of detection achieved between 0.03 and 1.24 ng/ml. These values were calculated when the four mycotoxins were present in samples at the same time. Samples of spiked water and field corn were tested to assess the performance of our microfluidic-based detection technique for the mycotoxins. Recovery rates of mycotoxins from spiked water and corn samples were accessed and the results ranged from 80% to 110%, where the intra-assay coefficients of variation were under 15%. In summary, the system can realize rapid and reliable detection of multiple contaminants in actual samples automatically.

Aspergillus-specific antibodies - Targets and applications

Aspergillus is a fungal genus comprising several hundred species, many of which can damage the health of plants, animals and humans by direct infection and/or due to the production of toxic secondary metabolites known as mycotoxins. Aspergillus-specific antibodies have been generated against polypeptides, polysaccharides and secondary metabolites found in the cell wall or secretions, and these can be used to detect and monitor infections or to quantify mycotoxin contamination in food and feed. However, most Aspergillus-specific antibodies are generated against heterogeneous antigen preparations and the specific target remains unknown. Target identification is important because this can help to characterize fungal morphology, confirm host penetration by opportunistic pathogens, detect specific disease-related biomarkers, identify new candidate targets for antifungal drug design, and qualify antibodies for diagnostic and therapeutic applications. In this review, we discuss how antibodies are raised against heterogeneous Aspergillus antigen preparations and how they can be characterized, focusing on strategies to identify their specific antigens and epitopes. We also discuss the therapeutic, diagnostic and biotechnological applications of Aspergillus-specific antibodies.

Volumetric registration of magnetic nanoparticles for optimization of quantitative immunochromatographic assays for detection of small molecules

Precise quantitative and highly sensitive detection of small molecules (haptens) is highly demanded in medicine, food quality control, in vitro diagnostics, criminalistics, environmental monitoring, etc. In the present work, the magnetic method of particle quantification and the optical methods of spectral correlation and spectral phase interferometry complement each other for optimization of a quantitative assay for measuring concentrations of small molecules. The assay employs magnetic nanoparticles as labels in rapid immunochromatographic format. The approach was demonstrated with fluorescein as a model molecule. The interferometric label-free biosensors were employed for selection of optimal reagents that produced high specificity and sensitivity. The method of magnetic particle quantification counted the magnetic labels over the entire volume of the immunochromatographic membrane to provide their distribution along the test strip. Such distribution was used for optimization of such parameters as concentrations of the used reagents and of antibody immobilized on the labels, amount of the labels and conjugates of haptens with protein carriers to realize the advanced quantitative immunochromatographic assay.