[Separation and enrichment of trace aflatoxin B1 in grains by magnetic nanomaterials based on SiO2@Fe3O4]

Aflatoxins in the rice production chain: A review on prevalence, detection, and decontamination strategies

Rice (Oryza sativa L.) is one of the most consumed cereals that along with several important nutritional constituents typically provide more than 21% of the caloric requirements of human beings. Aflatoxins (AFs) are toxic secondary metabolites of several Aspergillus species that are prevalent in cereals, including rice. This review provides a comprehensive overview on production factors, prevalence, regulations, detection methods, and decontamination strategies for AFs in the rice production chain. The prevalence of AFs in rice is more prominent in African and Asian than in European countries. Developed nations have more stringent regulations for AFs in rice than in the developing world. The contamination level of AFs in the rice varied at different stages of rice production chain and is affected by production practices, environmental conditions comprising temperature, humidity, moisture, and water activity as well as milling operations such as de-husking, parboiling, and polishing. A range of methods including chromatographic techniques, immunochemical methods, and spectrophotometric methods have been developed, and used for monitoring AFs in rice. Chromatographic methods are the most used methods of AFs detection followed by immunochemical techniques. AFs decontamination strategies adopted worldwide involve various physical, chemical, and biological strategies, and even using plant materials. In conclusion, adopting good agricultural practices, implementing efficient AFs detection methods, and developing innovative aflatoxin decontamination strategies are imperative to ensure the safety and quality of rice for consumers.

Unveiling the Potential of Bioinoculants and Nanoparticles in Sustainable Agriculture for Enhanced Plant Growth and Food Security

The increasing public concern over the negative impacts of chemical fertilizers and pesticides on food security and sustainability has led to exploring innovative methods that offer both environmental and agricultural benefits. One such innovative approach is using plant-growth-promoting bioinoculants that involve bacteria, fungi, and algae. These living microorganisms are applied to soil, seeds, or plant surfaces and can enhance plant development by increasing nutrient availability and defense against plant pathogens. However, the application of biofertilizers in the field faced many challenges and required conjunction with innovative delivering approaches. Nanotechnology has gained significant attention in recent years due to its numerous applications in various fields, such as medicine, drug development, catalysis, energy, and materials. Nanoparticles with small sizes and large surface areas (1-100 nm) have numerous potential functions. In sustainable agriculture, the development of nanochemicals has shown promise as agents for plant growth, fertilizers, and pesticides. The use of nanomaterials is being considered as a solution to control plant pests, including insects, fungi, and weeds. In the food industry, nanoparticles are used as antimicrobial agents in food packaging, with silver nanomaterials being particularly interesting. However, many nanoparticles (Ag, Fe, Cu, Si, Al, Zn, ZnO, TiO2, CeO2, Al2O3, and carbon nanotubes) have been reported to negatively affect plant growth. This review focuses on the effects of nanoparticles on beneficial plant bacteria and their ability to promote plant growth. Implementing novel sustainable strategies in agriculture, biofertilizers, and nanoparticles could be a promising solution to achieve sustainable food production while reducing the negative environmental impacts.

[Research advances of porous organic framework materials on enrichment and detection of mycotoxins]

Mycotoxins are a class of toxic secondary metabolites produced by fungi. These substances are carcinogenic, teratogenic, and mutagenic, and cause serious harm to the human body; thus, they have attracted wide attention worldwide. Establishing accurate, rapid, and sensitive methods for the detection of mycotoxins is of great significance. Chromatography is a commonly used technology for mycotoxin detection. However, it is challenging to use in the direct analysis of these metabolites because of the wide variety and distribution of mycotoxins, their complex sample matrix, and their very low content in actual samples. Therefore, the development of suitable sample pretreatment methods for the efficient separation and enrichment of mycotoxins is necessary. In recent years, porous organic framework materials, which are represented by metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs), have been widely applied in the sample pretreatment of mycotoxins owing to their many advantages, which include a large specific surface area, high porosity, adjustable pore size, diverse frame structures, uniform active site distribution, and modifiable structures. In addition, MOF/COF materials feature excellent fluorescence and electrochemical properties, rendering them highly suitable for mycotoxin analysis and sensing. In this article, the recent applications of MOF/COF materials in conventional sample pretreatment methods (e. g., solid-phase extraction, dispersive solid-phase extraction, magnetic solid-phase extraction, and immunomagnetic bead separation) for mycotoxin separation and enrichment are reviewed. Research on the use of MOF/COF materials for the fluorescence and electrochemical sensing of mycotoxins is also summarized. Finally, the existing challenges and future development trends of these materials are discussed and prospected to provide a reference for future research on the applications of MOF/COF materials in mycotoxin detection and analysis.

[Simultaneous determination of 36 mycotoxins in fruits by QuEChERS coupled with ultra performance liquid chromatography-tandem mass spectrometry]

Mycotoxins are secondary metabolites produced by toxigenic fungi under specific environmental conditions. Fruits, owing to their high moisture content, rich nutrition, and improper harvest or storage conditions, are highly susceptible to various mycotoxins, such as ochratoxin A (OTA), zearalenone (ZEN), patulin (PAT), Alternaria toxins, etc. These mycotoxins can cause acute and chronic toxic effects (teratogenicity, mutagenicity, and carcinogenicity, etc) in animals and humans. Given the high toxicity and wide prevalence of mycotoxins, establishing an efficient analytical method to detect multiple mycotoxins simultaneously in different types of fruits is of great importance. Conventional mycotoxin detection methods rely on high performance liquid chromatography (HPLC) coupled with mass spectrometry (MS). However, fruit sample matrices contain large amounts of pigments, cellulose, and minerals, all of which dramatically impede the detection of trace mycotoxins in fruits. Therefore, the efficient enrichment and purification of multiple mycotoxins in fruit samples is crucial before instrumental analysis. In this study, a reliable method based on a QuEChERs sample preparation approach coupled with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established to determine 36 mycotoxins in fruits. In the optimal extraction method, 2.0 g of a sample was extracted with 10 mL of acetic acid-acetonitrile-water (1∶79∶20, v/v/v) in a 50 mL centrifuge tube, vortexed for 30 s, and ultrasonicated for 40 min. The mixture was then salted out with 2.0 g of anhydrous MgSO4 and 0.5 g of NaCl and centrifuged for 5 min. Next, 6 mL of the supernatant was purified using 85 mg of octadecylsilane-bonded silica gel (C18) and 15 mg of N-propylethylenediamine (PSA). After vigorous shaking and centrifugation, the supernatant was collected and dried with nitrogen at 40 ℃. Finally, the residues were redissolved in 1 mL of 5 mmol/L ammonium acetate aqueous solution-acetonitrile (50∶50, v/v) and passed through a 0.22 μm nylon filter before analysis. The mycotoxins were separated on a Waters XBridge BEH C18 column using a binary gradient mixture of ammonium acetate aqueous solution and methanol. The injection volume was 3 μL. The mycotoxins were analyzed in multiple reaction monitoring (MRM) mode under both positive and negative electrospray ionization. Quantitative analysis was performed using an external standard method with matrix-matched calibration curves. Under optimal conditions, good linear relationships were obtained in the respective linear ranges, with correlation coefficients (R2) no less than 0.990. The limits of detection (LODs) and quantification (LOQs) were 0.02-5 and 0.1-10 μg/kg, respectively. The recoveries of the 36 mycotoxins in fruits ranged from 77.0% to 118.9% at low, medium, and high spiked levels, with intra- and inter-day precisions in the range of 1.3%-14.9% and 0.2%-17.3%, respectively. The validated approach was employed to investigate mycotoxin contamination in actual fruit samples, including strawberry, grape, pear, and peach (15 samples of each type). Eleven mycotoxins, namely, altenuene (ALT), altenusin (ALS), alternariol-methyl ether (AME), tenuazonic acid (TeA), tentoxin (Ten), OTA, beauvericin (BEA), PAT, zearalanone (ZAN), T-2 toxin (T2), and mycophenolic acid (MPA), were found in the samples; three samples were contaminated with multiple mycotoxins. The incidence rates of mycotoxins in strawberry, grape, pear, and peach were 27%, 40%, 40%, and 33%, respectively. In particular, Alternaria toxins were the most frequently found mycotoxins in these fruits, with an incidence of 15%. The proposed method is simple, rapid, accurate, sensitive, reproducible, and stable; thus, it is suitable for the simultaneous detection of the 36 mycotoxins in different fruits.

[Determination of four aflatoxins in feeds by high throughput automated immunoaffinity magnetic beads purification-ultra performance liquid chromatography]

Aflatoxin (AFT) is an extremely toxic and highly toxic carcinogenic substance. This is particularly problematic due to the risk of aflatoxin contamination in raw feed materials and products during production, transportation, and storage. In this study, immunoaffinity magnetic beads (IMBs) were prepared for the purification of four aflatoxins (aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1) and aflatoxin G2 (AFG2)). The aflatoxin contents were then determined rapidly and accurately using ultra performance liquid chromatography (UPLC). More specifically, the coupling ratio of magnetic beads (MBs) to the aflatoxin monoclonal antibody was initially optimized, wherein an MB volume of 1 mL and an antibody content of 2.0 mg was found to meet the purification requirements of this method. The magnetic properties of the MBs and the IMBs were then investigated using a vibrating sample magnetometer (VSM) at room temperature. As a result, the maximum saturation super magnetizations of the MBs and the IMBs were determined to be 28.61 and 23.22 emu/g, respectively, indicating that the saturation magnetization intensity of the IMBs was reduced by coupling with a non-magnetic antibody. However, the saturation magnetization intensity remained sufficiently high to permit magnetic separation from the solution. In addition, the appearance of the IMBs was examined using a biomicroscope, and it was clear that the magnetic cores were wrapped in agarose gel. Furthermore, the reaction time between the IMBs and the aflatoxins was investigated, and the optimal reaction time for meeting the purification requirements was determined to be 2 min. The stability of the IMBs was then evaluated under refrigerated storage conditions at 4 ℃. It was found that the prepared IMBs maintained a high aflatoxin enrichment capacity for at least eight months. Through the examination of three different extraction solutions, a mixture of acetonitrile and water (70∶30, v/v) was found to be optimal for the extraction of aflatoxins from the feed samples. Moreover, five sample dilutions and purification effects were also examined, and phosphate-buffered saline (containing 0.5% Tween-20) was selected as the preferred sample dilutant. With the optimized conditions, the effectiveness of using IMB for the purification of different feed samples was investigated. The resulting UPLC chromatogram showed no spurious peaks close to the target peaks, demonstrating a good purification performance. Following matrix spiking (5, 20, and 40 μg/kg, calculated based on AFB1) of the four feed samples (i. e., soybean meal, distillers dried grains with solubles, pig feed, and chicken feed), the spiked recoveries of the four aflatoxins ranged from 91.1% to 119.4% with a relative standard deviation (RSD) of <6.9%. In addition, the inter-day precision was 4.5% to 7.5%, and the method exhibited a good reproducibility. Subsequently, the developed method was used to detect AFB1 using reference materials. The test value was 18.6 μg/kg with an accuracy of 110.3%, thereby constituting satisfactory results. Upon testing 21 randomly purchased feed samples using this method, four of these samples contained AFB1, and the test results obtained using the developed method and stable isotope dilution LC-MS/MS were comparable. It was therefore apparent that the IMB purification method combined with UPLC analysis exhibited a good accuracy for aflatoxin determination. Thus, an automatic purification system was established to facilitate the operation and use of IMBs. This system was able to purify 24 samples simultaneously in 30 min. An IMB purification kit for was also designed and produced for aflatoxin detection in feed samples. The kit contained the sample dilutant, IMBs, the washing solution, and the eluent. After extraction of the feed sample, the extraction solution was added to the sample wells provided in the kit, and the purification system automatically completed the steps of aflatoxin enrichment, impurity washing, and elution of the target toxin. It should be noted that the purification process does not require the operator to manually add the solution, thereby simplifying operation. Overall, the purification method established in this study achieved the high-throughput and automatic purification of the four aflatoxins in feed samples.