Determination of aflatoxin M1 in milk and dairy products using high performance liquid chromatography-fluorescence with post column photochemical derivatization

Sandwich-type aptamer-based biosensors for thrombin detection

Thrombin, a proteolytic enzyme, plays an essential role in catalyzing many blood clotting reactions. Thrombin can act as a marker for some blood-related diseases, such as leukemia, thrombosis, Alzheimer's disease and liver disease. Therefore, its diagnosis is of great importance in the fields of biological and medical research. Biosensors containing sandwich-type structures have attracted much consideration owing to their superior features such as reproducible and stable responses with easy improvement in the sensitivity of detection. Sandwich-type platforms can be designed using a pair of receptors that are able to bind to diverse locations of the same target. Herein, we investigate recent advances in the progress and applications of thrombin aptasensors containing a sandwich-type structure, in which two thrombin-binding aptamers (TBAs) identify different parts of the thrombin molecule, leading to the formation of a sandwich structure and ultimately signal detection. We also discuss the pros and cons of these approaches and outline the most logical approach in each section.

Determination of mycobiota and aflatoxin contamination in commercial bee pollen from eight provinces and one autonomous region of China

The co-occurrence of fungi and mycotoxins in various foods has been frequently reported in many countries, posing a serious threat to the health and safety of consumers. In this study, the mycobiota in five types of commercial bee pollen samples from China were first revealed by DNA metabarcoding. Meanwhile, the content of total aflatoxins in each sample was investigated by high-performance liquid chromatography with fluorescence detection. The results demonstrated that Cladosporium (0.16 %-89.29 %) was the most prevalent genus in bee pollen, followed by Metschnikowia (0-81.12 %), unclassified genus in the phylum Ascomycota (0-81.13 %), Kodamaea (0-73.57 %), and Penicillium (0-36.13 %). Meanwhile, none of the assayed aflatoxins were determined in the 18 batches of bee pollen samples. In addition, the fungal diversity, community composition, and trophic mode varied significantly among five groups. This study provides comprehensive information for better understanding the fungal communities and aflatoxin residues in bee pollen from different floral origins in China.

Aflatoxin detection technologies: recent advances and future prospects

Aflatoxins have posed serious threat to food safety and human health. Therefore, it is important to detect aflatoxins in samples rapidly and accurately. In this review, various technologies to detect aflatoxins in food are discussed, including conventional ones such as thin-layer chromatography (TLC), high performance liquid chromatography (HPLC), enzyme linked immunosorbent assay (ELISA), colloidal gold immunochromatographic assay (GICA), radioimmunoassay (RIA), fluorescence spectroscopy (FS), as well as emerging ones (e.g., biosensors, molecular imprinting technology, surface plasmon resonance). Critical challenges of these technologies include high cost, complex processing procedures and long processing time, low stability, low repeatability, low accuracy, poor portability, and so on. Critical discussion is provided on the trade-off relationship between detection speed and detection accuracy, as well as the application scenario and sustainability of different technologies. Especially, the prospect of combining different technologies is discussed. Future research is necessary to develop more convenient, more accurate, faster, and cost-effective technologies to detect aflatoxins.

Recent Insights into Sample Pretreatment Methods for Mycotoxins in Different Food Matrices: A Critical Review on Novel Materials

Mycotoxins pollution is a global concern, and can pose a serious threat to human health. People and livestock eating contaminated food will encounter acute and chronic poisoning symptoms, such as carcinogenicity, acute hepatitis, and a weakened immune system. In order to prevent or reduce the exposure of human beings and livestock to mycotoxins, it is necessary to screen mycotoxins in different foods efficiently, sensitively, and selectively. Proper sample preparation is very important for the separation, purification, and enrichment of mycotoxins from complex matrices. This review provides a comprehensive summary of mycotoxins pretreatment methods since 2017, including traditionally used methods, solid-phase extraction (SPE)-based methods, liquid-liquid extraction (LLE)-based methods, matrix solid phase dispersion (MSPD), QuEChERS, and so on. The novel materials and cutting-edge technologies are systematically and comprehensively summarized. Moreover, we discuss and compare the pros and cons of different pretreatment methods and suggest a prospect.

Solid-phase extraction techniques based on nanomaterials for mycotoxin analysis: An overview for food and agricultural products

Mycotoxin contamination is a globally concerned problem for food and agricultural products since it may directly or indirectly induce severe threats to human health. Sensitive and selective screening is an efficient strategy to prevent or reduce human and animal exposure to mycotoxins. However, enormous challenges exist in the determination of mycotoxins, arising from complex sample matrices, trace-level analytes, and the co-occurrence of diverse mycotoxins. Appropriate sample preparation is essential to isolate, purify, and enrich mycotoxins from complicated matrices, thus decreasing sample matrix effects and lowering detection limits. With the cross-disciplinary development, new solid-phase extraction strategies have been exploited and integrated with nanotechnology to meet the challenges of mycotoxin analysis. This review summarizes the advance and progress of solid-phase extraction techniques as the methodological solutions for mycotoxin analysis. Emphases are paid on nanomaterials fabricated as trapping media of SPE techniques, including carbonaceous nanoparticles, metal/metal oxide-based nanoparticles, and nanoporous materials. Advantages and limitations are discussed, along with the potential prospects. This article is protected by copyright. All rights reserved.

Construction of a magnetic covalent organic framework for magnetic solid-phase extraction of AFM1 and AFM2 in milk prior to quantification by LC-MS/MS

A magnetic covalent organic framework (M-COF) was designed and selected as sorbent for magnetic solid-phase extraction (MSPE) of AFM1 and AFM2 in milk, followed by LC-MS/MS analysis. The application of 2,5-Dihydroxy-1,4-benzenedicarboxaldehyde (Dt) and 4',5'-bis(4-aminophenyl)-[1,1':2',1″-terphenyl]-4,4″-diamine (BAPTPDA) as monomers endows M-COF excellent properties for adsorbing AFM1 and AFM2. The morphology, structure, stability, and magnetism of the Fe₃O₄@COF(BAPTPDA-Dt) were characterized by various techniques including scanning electron microscopy, transmission electron microscopy, FTIR, thermogravimetric analysis, and vibrating sample magnetometer. The Fe₃O₄ microspheres were covered by COF shells. Fe₃O₄@COF exhibited excellent magnetism and stability. Some parameters that may influence the adsorption efficiency of MSPE were also optimized, making the extraction process more effective, time-saving (about 3 min), and less organic-reagent-consuming (only 4 mL of acetonitrile required). It is noteworthy that the Fe₃O₄@COF(BAPTPDA-Dt) can be reutilized more than 8 times. The AFM1 and AFM2 were determined by LC-MS/MS. The LODs for AFM1 and AFM2 were in the range 0.0069 to 0.0078 μg kg^-1. A wide linearity range (0.01-100 μg kg^-1) with coefficients of determination (R²) ranging from 0.9998 to 0.9999 was obtained. The recoveries at four spiked concentrations (0.05, 0.5, 5, and 50 μg kg^-1) in the milk matrix ranged from 85.2 to 106.5%. The intraday RSDs and the interday RSDs were in the range 1.74-4.58% and 2.65-6.69%, respectively. The matrix effect (9.3% for AFM1 and 6.7% for AFM2) was also significantly lower than that observed in other work . Overall, the established method has provided a powerful tool for rapid pretreatment and sensitive determination of AFM1 and AFM2 in milk with negligible matrix effect, presenting important value in toxicant determination.

Detection of Potential Microbial Contaminants and Their Toxins in Fermented Dairy Products: a Comprehensive Review

Fermented dairy products are dominant constituents of daily diets around the world due to their desired organoleptic properties, long shelf life, and high nutritional value. Probiotics are often incorporated into these products for their health and technological benefits. However, the safety and possible contamination of fermented dairy products during the manufacturing process could have significant deleterious health and economic impacts. Pathogenic microorganisms and toxins from different sources in fermented dairy products contribute to outbreaks and toxicity cases. Although the health and nutritional benefits of fermented dairy products have been extensively investigated, safety hazards due to contamination are relatively less explored. As a preventive measure, it is crucial to accurately identify and determine the associated microbiota or their toxins. It is noteworthy to highlight the importance of detecting not only the pathogenic microbiota but also their toxic metabolites so that putative outbreaks can thereby be prevented or detected even before they cause harmful effects to human health. In this context, this review focuses on describing techniques designed to detect potential contaminants; also, the advantages and disadvantages of these techniques were summarized. Moreover, this review compiles the most recent and efficient analytical methods for detecting microbial hazards and toxins in different fermented dairy products of different origins. Causative agents behind contamination incidences are also discussed briefly to aid in future prevention measures, as well as detection approaches and technologies employed. Such approach enables the elucidation of the best strategies to control contamination in fermented dairy product manufacturing processes.

Multiclass Comparative Analysis of Veterinary Drugs, Mycotoxins, and Pesticides in Bovine Milk by Ultrahigh-Performance Liquid Chromatography-Hybrid Quadrupole-Linear Ion Trap Mass Spectrometry

A multiclass and multiresidue method for simultaneously screening and confirming veterinary drugs, mycotoxins, and pesticides in bovine milk was developed and validated with ultrahigh-performance liquid chromatography–hybrid quadrupole–linear ion trap mass spectrometry (UHPLC-Qtrap-MS). A total of 209 targeted contaminants were effectively extracted using an optimized QuEChERS method. Quantitative and qualitative confirmation were achieved simultaneously by multiple reaction monitoring–information-dependent acquisition–enhanced product ion (MRM-IDA-EPI) scan mode. The validation results exhibited a good sensitivity with the LOQs of 0.05–5 μg/kg, which was satisfactory for their MRLs in China or EU. The recoveries of in-house spiked samples were in the range of 51.20–129.76% with relative standard deviations (RSD) between replicates (n = 3) 0.82% and 19.76%. The test results of 140 milk samples from supermarkets and dairy farms in China showed that cloxacillin, aflatoxin M1, acetamiprid, and fipronil sulfone were found with lower concentrations. Combined with the residue results from the literature, penicillin G and cloxacillin (beta-lactams), enrofloxacin and ciprofloxacin (fluoroquinolones), and sulfamerazine (sulfonamides) were more frequently detected in different countries and need to receive more attention regarding their monitoring and control.

Assessment of aflatoxin M1 and B1 in some dairy products with referring to the analytical performances of enzyme-linked immunosorbent assay in comparison to high-performance liquid chromatography

Background and Aim:

Aflatoxin M₁ (AFM₁) is a major fungal metabolite found in milk coming from aflatoxin B₁ (AFB₁) contaminated rations and is subsequently present in milk-based products demonstrating a serious public health hazard. This study aimed to investigate the levels of AFM₁ and AFB₁ in milk and some dairy products consumed widely by infants and children.

Materials and Methods:

This study investigated the incidence of AFM₁ in 105 samples of processed cheese, Ras cheese, and raw milk (35 of each) retailed in the Egyptian markets. The degree of sensitivity and accuracy was evaluated using the enzyme-linked immunosorbent assay (ELISA) method followed by the estimation of the positive samples using the high-performance liquid chromatography (HPLC) with fluorescence detection. Mold count was determined in the examined samples by investigating AFB₁ content using HPLC.

Results:

AFM₁ was found in all investigated Ras cheese, raw milk, and 82.86% of the processed cheese samples with mean values of 51.05±6.19, 40.27±3.996, and 10.77±1.39 ng/kg, respectively. Moreover, there was statistically no significant difference between AFM₁ levels in the core and crust parts of the tested Ras cheese. AFM₁ contaminated Ras cheese and raw milk samples were 48.57% and 25.71%, which exceeded the European and Egyptian tolerance levels. Results showed an acceptable correlation between ELISA and HPLC methods with no significant difference (p>0.05). Alternatively, none of the examined samples proved to be contaminated with AFB₁ despite the presence of mold with mean counts of 3.79±3.29, 4.39±4.34, and 4.84±4.29 log CFU/g in the examined processed cheese, Ras cheese, and raw milk samples, respectively.

Conclusion:

Therefore, it is urgent to regularly inspect the contamination of animal feeds with AFB₁ and apply special measures and novel techniques to protect the feed and food from public health hazards.

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.

An ultrasensitive, homogeneous fluorescence quenching immunoassay integrating separation and detection of aflatoxin M1 based on magnetic graphene composites

A homogeneous fluorescence quenching immunoassay is described for simultaneous separation and detection of aflatoxin M₁ (AFM₁) in milk. The novel assay relies on monoclonal antibody (mAb) functionalized Fe₃O₄ decorated reduced-graphene oxide (rGO-Fe₃O₄-mAb) as both capture probe and energy acceptor, combined with tetramethylrhodamine cadaverine-labeled aflatoxin B₁ (AFB₁-TRCA) as the energy donor. In the assay, AFB₁-TRCA binds to rGO-Fe₃O₄-mAb in the absence of AFM₁, quenching the fluorescence of TRCA by resonance energy transfer. Significantly, the immunoassay integrates sample preparation and detection into a single step, by using magnetic graphene composites to avoid washing and centrifugation steps, and the assay can be completed within 10 min. Under optimized conditions, the visual and quantitative detection limits of the assay for AFM₁ were 50 and 3.8 ng L^-1, respectively, which were significantly lower than those obtained by fluorescence polarization immunoassay using the same immunoreagents. Owing to its operation and highly sensitivity, the proposed assay provides a powerful tool for the detection of AFM₁.

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.

Rapid and Sensitive Detection of Aflatoxin B1, B2, G1 and G2 in Vegetable Oils Using Bare Fe3O4 as Magnetic Sorbents Coupled with High-Performance Liquid Chromatography with Fluorescence Detection

This paper reports a simple, sensitive and reliable method for the simultaneous detection of aflatoxin B1, B2, G1 and G2 in vegetable oils. Aflatoxins were extracted by magnetic solid phase extraction followed by high-performance liquid chromatography, then postcolumn photochemical derivatization and finally detected by fluorescence detector. Vegetable oil samples were first diluted with hexane and then commercial bare Fe3O4 nanoparticles were directly employed as sorbents to extract aflatoxins from complex vegetable oil samples, which significantly simplified the procedure of sample preparation and largely improved the sample analysis throughput. The effects of various parameters such as the amount of sorbent, loading, washing and eluting conditions were carefully optimized to improve the extraction efficiencies of aflatoxins. Under the optimal conditions, the limits of detection of four aflatoxins ranged from 0.01 μg/kg to 0.16 μg/kg, and squared regression coefficients (R2) >0.9990 were obtained within the linear range of 0.1-20 μg/kg (except for aflatoxin G2 with 0.5-20 μg/kg). Furthermore, the recoveries spiked at four concentration levels in a blank vegetable oil sample were from 82.6 to 106.2%, with inter- and intraday relative standard deviations <9.8%, indicating good accuracy and precision of the proposed method.

Detection Methods for Aflatoxin M1 in Dairy Products

Mycotoxins are toxic compounds produced mainly by fungi of the genera Aspergillus, Fusarium and Penicillium. In the food chain, the original mycotoxin may be transformed in other toxic compounds, reaching the consumer. A good example is the occurrence of aflatoxin M1 (AFM1) in dairy products, which is due to the presence of aflatoxin B1 (AFB1) in the animal feed. Thus, milk-based foods, such as cheese and yogurts, may be contaminated with this toxin, which, although less toxic than AFB1, also exhibits hepatotoxic and carcinogenic effects and is relatively stable during pasteurization, storage and processing. For this reason, the establishment of allowed maximum limits in dairy products and the development of methodologies for its detection and quantification are of extreme importance. There are several methods for the detection of AFM1 in dairy products. Usually, the analytical procedures go through the following stages: sampling, extraction, clean-up, determination and quantification. For the extraction stage, the use of organic solvents (as acetonitrile and methanol) is still the most common, but recent advances include the use of the Quick, Easy, Cheap, Effective, Rugged, and Safe method (QuEChERS) and proteolytic enzymes, which have been demonstrated to be good alternatives. For the clean-up stage, the high selectivity of immunoaffinity columns is still a good option, but alternative and cheaper techniques are becoming more competitive. Regarding quantification of the toxin, screening strategies include the use of the enzyme-linked immunosorbent assay (ELISA) to select presumptive positive samples from a wider range of samples, and more reliable methods-high performance liquid chromatography with fluorescence detection or mass spectroscopy-for the separation, identification and quantification of the toxin.

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.

Quantum bead-based fluorescence-linked immunosorbent assay for ultrasensitive detection of aflatoxin M1 in pasteurized milk, yogurt, and milk powder

Herein, we reported a novel direct competitive fluorescence-linked immunosorbent assay (dcFLISA) for the ultrasensitive detection of aflatoxin M₁ (AFM₁) in pasteurized milk, yogurt, and milk powder using 150-nm quantum dot beads (QB) as the carrier of competing antigen. Large QB were applied to decrease the binding affinity of the competing antigen to antibody and enhance the fluorescent signal intensity. The aflatoxin B₁ molecule was used as the surrogate of AFM₁ to label with BSA on the surface of QB because of its 63% cross reaction to anti-AFM₁ mAb. The binding affinity of the competing antigen to mAb was tuned by changing the labeled molar ratios of aflatoxin B₁ to BSA. Through combining the advantages of QB as the carrier of the competing antigen, including low binding affinity to mAb and highly fluorescent signal output, the proposed dcFLISA exhibited an ultrahigh sensitivity for AFM₁ detection, with a half-maximal inhibitory concentration of 3.15 pg/mL in 0.01 M phosphate-buffered saline solution (pH 7.4), which is substantially lower than that of the traditional horseradish peroxidase-based ELISA. The proposed method also exhibited very low detection limitations of 0.5, 0.6, and 0.72 pg/mL for real pasteurized milk, yogurt, and milk powder, respectively. These values are considerably below the maximum permissible level of the European Commission standard for AFM₁ in dairy products. In summary, the proposed dcFLISA offers a novel strategy with an ultrahigh sensitivity for the routine monitoring of AFM₁ in various dairy products.

Liquid Chromatography Analysis of Common Nutritional Components, in Feed and Food

Food and feed laboratories share several similarities when facing the implementation of liquid-chromatographic analysis. Using the experience acquired over the years, through application chemistry in food and feed research, selected analytes of relevance for both areas were discussed. This review focused on the common obstacles and peculiarities that each analyte offers (during the sample treatment or the chromatographic separation) throughout the implementation of said methods. A brief description of the techniques which we considered to be more pertinent, commonly used to assay such analytes is provided, including approaches using commonly available detectors (especially in starter labs) as well as mass detection. This manuscript consists of three sections: feed analysis (as the start of the food chain); food destined for human consumption determinations (the end of the food chain); and finally, assays shared by either matrices or laboratories. Analytes discussed consist of both those considered undesirable substances, contaminants, additives, and those related to nutritional quality. Our review is comprised of the examination of polyphenols, capsaicinoids, theobromine and caffeine, cholesterol, mycotoxins, antibiotics, amino acids, triphenylmethane dyes, nitrates/nitrites, ethanol soluble carbohydrates/sugars, organic acids, carotenoids, hydro and liposoluble vitamins. All analytes are currently assayed in our laboratories.

Determination of nitenpyram and 6-chloronicotinic acid in environmental samples by ion chromatography coupled with online photochemically induced fluorescence detector

A simple, cost-effective, sensitive, and quick method for the determination of nitenpyram and its metabolite 6-chloronicotinic acid in environmental samples was developed by coupling an ion chromatograph with a fluorescence detector and a post-column photochemical reactor. This developed analytical method involved a rapid sample extraction by modified and miniaturized quick, easy, cheap, effective, rugged, and safe method followed by isocratic ion chromatographic separation of nitenpyram and 6-chloronicotinic acid into an IonPac^™ AS11-HC column protected by IonPac^™ AG11A guard column by running 30 mM NaOH + 10% acetonitrile mobile phase. A homemade post-column photochemical reactor was also integrated with the ion chromatographic system for online transformation of both analytes into their respective highly fluorescent photoproduct in basic media without using an extra pump. The developed method was validated by following SANTE/11945/2015 guidelines on analytical quality control and validation procedures. The method showed a good linear response (r > 0.999), improved limit of detection (0.101-0.132 μg/L), minimum or no matrix effect, excellent recoveries (90.2-100.10%) and relative standard deviations were found to be ≤6.50%.

Nanobody Technology for Mycotoxin Detection in the Field of Food Safety: Current Status and Prospects

Mycotoxins, which are toxic, carcinogenic, and/or teratogenic, have posed a threat to food safety and public health. Sensitive and effective determination technologies for mycotoxin surveillance are required. Immunoassays have been regarded as useful supplements to chromatographic techniques. However, conventional antibodies involved in immunoassays are difficult to be expressed recombinantly and are susceptible to harsh environments. Nanobodies (or VHH antibodies) are antigen-binding sites of the heavy-chain antibodies produced from Camelidae. They are found to be expressed easily in prokaryotic or eukaryotic expression systems, more robust in extreme conditions, and facile to be used as surrogates for artificial antigens. These properties make them the promising and environmentally friendly immunoreagents in the next generation of immunoassays. This review briefly describes the latest developments in the area of nanobodies used in mycotoxin detection. Moreover, by integrating the introduction of the principle of nanobodies production and the critical assessment of their performance, this paper also proposes the prospect of nanobodies in the field of food safety in the foreseeable future.

Achievements and Prospects in Electrochemical-Based Biosensing Platforms for Aflatoxin M₁ Detection in Milk and Dairy Products

Aflatoxins, which are mainly produced by Aspergillus flavus and parasiticus growing on plants and products stored under inappropriate conditions, represent the most studied group of mycotoxins. Contamination of human and animal milk with aflatoxin M₁, the hydroxylated metabolite of aflatoxin B₁, is an important health risk factor due to its carcinogenicity and mutagenicity. Due to the low concentration of this aflatoxin in milk and milk products, the analytical methods used for its quantification have to be highly sensitive, specific and simple. This paper presents an overview of the analytical methods, especially of the electrochemical immunosensors and aptasensors, used for determination of aflatoxin M₁.

Palladium Nanoparticles-Based Fluorescence Resonance Energy Transfer Aptasensor for Highly Sensitive Detection of Aflatoxin M₁ in Milk

A highly sensitive aptasensor for aflatoxin M₁ (AFM₁) detection was constructed based on fluorescence resonance energy transfer (FRET) between 5-carboxyfluorescein (FAM) and palladium nanoparticles (PdNPs). PdNPs (33 nm) were synthesized through a seed-mediated growth method and exhibited broad and strong absorption in the whole ultraviolet-visible (UV-Vis) range. The strong coordination interaction between nitrogen functional groups of the AFM₁ aptamer and PdNPs brought FAM and PdNPs in close proximity, which resulted in the fluorescence quenching of FAM to a maximum extent of 95%. The non-specific fluorescence quenching caused by PdNPs towards fluorescein was negligible. After the introduction of AFM₁ into the FAM-AFM₁ aptamer-PdNPs FRET system, the AFM₁ aptamer preferentially combined with AFM₁ accompanied by conformational change, which greatly weakened the coordination interaction between the AFM₁ aptamer and PdNPs. Thus, fluorescence recovery of FAM was observed and a linear relationship between the fluorescence recovery and the concentration of AFM₁ was obtained in the range of 5–150 pg/mL in aqueous buffer with the detection limit of 1.5 pg/mL. AFM₁ detection was also realized in milk samples with a linear detection range from 6 pg/mL to 150 pg/mL. The highly sensitive FRET aptasensor with simple configuration shows promising prospect in detecting a variety of food contaminants.