A film-like SERS aptasensor for sensitive detection of patulin based on GO@Au nanosheets

Patulin (PAT) commonly contaminates fruits, posing a significant risk to human health. Therefore, a highly effective and sensitive approach in identifying PAT is warranted. Herein, a SERS aptasensor was constructed based on a two-dimensional film-like structure. GO@Au nanosheets modified with SH-cDNA were employed as capture probes, while core-shell Au@Ag nanoparticles modified with 4-MBA and SH-Apt were utilized as signal probes. Through the interaction between capture probes and signal probes, adjustable hotspots were formed, yielding a significant Raman signal. During sensing, the GO@Au-cDNA competitively attached to Au@AgNPs@MBA-Apt, resulting in an inverse relationship between PAT levels and SERS intensity. The acquired results exhibited linear responses to PAT within the range of 1-70 ng/mL, with a calculated limit of detection of 0.46 ng/mL. In addition, the SERS aptasensor exhibited satisfactory recoveries in apple samples, which aligned closely with HPLC. With high sensitivity and specificity, this method holds significant potential for PAT detection.

The small GTPase Ypt7 of Penicillium expansum is required for growth, patulin biosynthesis and virulence

Ypt GTPases are the largest subfamily of small GTPases involved in membrane transport. Here, a PeYpt7 gene deletion mutant of P. expansum was constructed. The ΔPeYpt7 mutant showed reduced colony growth with abnormal mycelial growth, reduced conidiation, and insufficient spore development. The mutation rendered the pathogen susceptible to osmotic stress and cell wall stressors. In addition, the absence of PeYpt7 reduced patulin production in P. expansum and significantly limited gene expression (PatG, PatH, PatI, PatD, PatF, and PatL). In addition, the mutant showed attenuated virulence in infected fruit and reduced expression of pathogenic factors was (PMG, PG, PL, and GH1). Thus, PeYpt7 modulates the growth, morphology, patulin accumulation, and pathogenicity of P. expansum by limiting the expression of related genes.

A Redox Mediator-Free Highly Selective and Sensitive Electrochemical Aptasensor for Patulin Mycotoxin Detection in Apple Juice Using Ni-NiO Pseudocapacitive Nanomaterials

Pseudocapacitive nanomaterials have recently gained significant attention in electrochemical biosensors due to their rapid response, long cycle life, high surface area, biomolecule compatibility, and superior energy storage capabilities. In our study, we introduce the potential of using Ni-NiO nanofilm's pseudocapacitive traits as transducer signals in electrochemical aptasensors. Capitalizing on the innate affinity between histidine and nickel, we immobilized histidine-tagged streptavidin (HTS) onto Ni-NiO-modified electrodes. Additionally, we employed a biolayer interferometry-based SELEX to generate biotinylated patulin aptamers. These aptamers, when placed on Ni-NiO-HTS surfaces, make a suitable biosensing platform for rapid patulin mycotoxin detection in apple juice using electrochemical amperometry in microseconds. The novelty lies in optimizing pseudocapacitive nanomaterials structurally and electrochemically, offering the potential for redox mediator-free electrochemical aptasensors. Proof-of-concept is conducted by applying this surface for the ultrasensitive detection of a model analyte, patulin mycotoxin. The aptamer-functionalized bioelectrode showed an excellent linear response (10-106 fg/mL) and an impressive detection limit (1.65 fg/mL, +3σ of blank signal). Furthermore, reproducibility tests yielded a low relative standard deviation of 0.51%, indicating the good performance of the developed biosensor. Real sample analysis in freshly prepared apple juice revealed no significant difference (P < 0.05) in current intensity between spiked and real samples. The sensor interface maintained excellent stability for up to 2 weeks (signal retention 96.45%). The excellent selectivity, stability, and sensitivity of the electrochemical aptasensor exemplify the potential for using nickel-based pseudocapacitive nanomaterials for a wide variety of electrochemical sensing applications.

Structural switching aptamer-based electrochemical sensor for mycotoxin patulin detection

In this study, an electrochemical and aptamer-based aptasensor was developed for the sensitive detection of patulin, a mycotoxin commonly found in fruits and fruit-based products. The aptasensor used an innovative structural switching signal-off platform for detecting patulin. The aptamer immobilization on screen-printed carbon electrodes was achieved through Au electrodeposition and thiol group (-SH) route. Response surface methodology was used to determine the optimal incubation times for the aptamer, blocking agent, and target molecule, which were found to be 180 min, 40 min, and 89 min, respectively. The response of the aptamer to different concentrations of patulin was measured using square wave voltammetry by exploiting the structural switching mechanism. The sensor response was determined by quantifying differences in the aptasensor's background current. The aptasensor exhibited a linear working range of 1-25 μM and a low detection limit of 3.56 ng/mL for patulin. The aptasensor's relative standard deviation and accuracy were determined to be 0.067 and 94.4%, respectively. A non-specific interaction was observed at low concentrations of two other mycotoxins, ochratoxin A and zearalenone. The interference from ochratoxin A in the measurements was below 10%. In real sample tests using apple juice, interference, particularly at low concentrations, had changed the recovery of patulin negatively with a significant effect on the structural switching behavior. Nevertheless, at a concentration of 25 ng/mL, the interference effect was eliminated, and the recovery standard deviation improved to 6.6%. The aptasensor's stability was evaluated over 10 days, and it demonstrated good performance, retaining 13.12% of its initial response. These findings demonstrate the potential of the developed electrochemical aptasensor for the sensitive detection of patulin in fruit-based products, with prospects for application in food safety and quality control.

New insights into searching patulin degrading enzymes in Saccharomyces cerevisiae through proteomic and molecular docking analysis

Global warming has increased the contamination of mycotoxins. Patulin (PAT) is a harmful contaminant that poses a serious threat to food safety and human health. Saccharomyces cerevisiae biodegrades PAT by its enzymes during fermentation, which is a safe and efficient method of detoxification. However, the key degradation enzymes remain unclear. In this study, the proteomic differences of Saccharomyces cerevisiae under PAT stress were investigated. The results showed that the proteins involved in redox reactions and defense mechanisms were significantly up-regulated to resist PAT stress. Subsequently, molecular docking was used to virtual screen for degrading enzymes. Among 18 proteins, YKL069W showed the highest binding affinity to PAT and was then expressed in Escherichia coli, where the purified YKL069W completely degraded 10 μg/mL PAT at 48 h. YKL069W was demonstrated to be able to degrade PAT into E-ascladiol. Molecular dynamics simulations confirmed that YKL069W was stable in catalyzing PAT degradation with a binding free energy of - 7.5 kcal/mol. Furthermore, it was hypothesized that CYS125 and CYS101 were the key amino acid residues for degradation. This study offers new insights for the rapid screening and development of PAT degrading enzymes and provides a theoretical basis for the detoxification of mycotoxins.

Ratiometric fluorescence aptasensor for the detection of patulin in apple juice based on the octahedral UiO-66-TCPP metal-organic framework and aptamer systems

Patulin (PAT) is a potentially harmful mycotoxin to human health and is known to contaminate apple juice. In this work, we developed a ratiometric fluorescence aptasensor using tetrakis(4-carboxyphenyl)porphyrin (H2TCPP)-treated octahedral UiO-66-NH2 (defined as UiO-66-TCPP) to detect PAT. This 2-aminoterephthalic acid and H2TCPP functionalized metal-organic framework showed multiple adsorption effects (hydrogen bonding and π-π stacking) on the aptamer (Apt) and served as a quenching material. When the target PAT bound specifically to the Apt, the fluorescence of the 6-carboxyfluorescein-labeled Apt would recover, and the fluorescence of the H2TCPP ligand remained unchanged. This ratiometric fluorescence property improved the accuracy of PAT detection. Moreover, the introduction of the H2TCPP ligand enhanced the quenching efficiency of UiO-66-NH2, thus improving the sensitivity of the fluorescent aptasensor (UiO-66-TCPP vs. UiO-66-NH2: 0.0162 ng/mL vs. 1.8 ng/mL). In addition, we used UiO-66-TCPP to detect PAT in apple juice samples. This work provides a good paradigm for the construction of ratiometric fluorescence aptasensors with high sensitivity and accuracy.

WSC1 Regulates the Growth, Development, Patulin Production, and Pathogenicity of Penicillium expansum Infecting Pear Fruits

In this study, the role of WSC1 in the infection of pear fruit by Penicillium expansum was investigated. The WSC1 gene was knocked out and complemented by Agrobacterium-mediated homologous recombination technology. Then, the changes in growth, development, and pathogenic processes of the knockout mutant and the complement mutant were analyzed. The results indicated that deletion of WSC1 slowed the growth rate, reduced the mycelial and spore yield, and reduced the ability to produce toxins and pathogenicity of P. expansum in pear fruits. At the same time, the deletion of WSC1 reduced the tolerance of P. expansum to cell wall stress factors, enhanced antioxidant capacity, decreased hypertonic sensitivity, decreased salt stress resistance, and was more sensitive to most metal ions. Our results confirmed that WSC1 plays an important role in maintaining cell wall integrity and responding to stress, toxin production, and the pathogenicity of P. expansum.

Infiltration of porcine pancreatic lipase into magnetic hierarchical mesoporous UiO-66-NH2 metal-organic frameworks for efficient detoxification of patulin from apple juice

Patulin (PAT) is a mycotoxin known to globally contaminate fruits. The economic losses and health hazards caused by PAT desires a safe and efficient strategy for detoxifying PAT. Here, a magnetic core-shell hierarchical mesoporous metal-organic framework (Fe3O4@HMUiO-66-NH2) was synthesized via a salt-assisted nanoemulsion guided assembly method. This mesoporous structure (centered at 4.25 nm) allowed porcine pancreatic lipase (PPL) to infiltrate into the MOF shell at an immobilized amount of 255 mg/g, providing protection for PPL and enabling rapid separation and recovery. Compared with free PPL, PPL/Fe3O4@HMUiO-66-NH2 at 70 °C possessed 4.7 folds improved thermal stability in terms of half-life. The detoxification rates of immobilized enzyme for PAT in neutral water, acidic water, and apple juice were 99.6%, 60.9%, and 52.6%, respectively. Moreover, the so designed PPL/Fe3O4@HMUiO-66-NH2 showed extraordinary storage stability, reusability, and biocompatibility. Crucially, the quality of apple juice did not change significantly after PPL/Fe3O4@HMUiO-66-NH2 treatment, which facilitated its application in apple juice. The magnetic core-shell mesoporous structure along with the revealed mechanism of immobilized enzyme detoxification of PAT provide tremendous opportunity for designing a safe and efficient PAT detoxification method.

Simultaneous detection of patulin and ochratoxin A based on enhanced dual-color AuNCs modified aptamers in apple juice

Patulin (PAT) and ochratoxin A (OTA) are the two main mycotoxins present in apples. Herein, a sensitive aptasensor for simultaneous detection of PAT and ochratoxin OTA was developed. Dual-color gold nanoclusters (AuNCs) with enhanced fluorescence properties were synthesized and employed as fluorescence amplifiers. Two separated fluorescence peaks at 650 nm and 530 nm were monitored simultaneously by employing single excitation (405 nm), corresponding to the aptamer probes of Cys@BSA-AuNCs-AptPAT and Arg@ATT-AuNCs-AptOTA, respectively. The fluorescent aptasensor demonstrated satisfying specificity, storage ability and accuracy. Under the optimal experimental conditions, the linear detection range for PAT and OTA was 0.10-50 ng/mL, with the limit of detection of 0.09 ng/mL and 0.06 ng/mL, respectively. Most importantly, practicability of the constructed aptasensor were confirmed by conducting the determination of PAT and OTA in apple juice sample, indicating the great potential of the aptasensor in practical detection applications.

The fate of mycotoxins in oranges during storage and processing

To evaluate the safety of orange consumption induced by mycotoxins, 'Newhall' navel oranges were artificially inoculated with P. expansum and A. tenuissima, followed by an evaluation of the distribution and migration patterns of corresponding mycotoxins (patulin [PAT], tentoxin [Ten], altenuene [ALT], alternariol monomethyl ether [AME], alternariol [AOH] and tenuazonic acid [TeA]) during orange storage and processing. The concentration of mycotoxins decreased as the increase of distance from the lesion, and mycotoxins could be detected throughout the orange when the lesion extended to 8 mm in diameter. AOH and AME pose the primary source of dietary risk with high concentrations and low thresholds of toxicological concern. Orange juice and pectin processing could remove 43.4-98.7% of mycotoxins, while tangerine peelprocessing might lead to significant enrichment of mycotoxins with the processing factors (PFs) of 2.8-3.5. The findings may offer scientific insights into mitigating the dietary risk of mycotoxin exposure from oranges and their derivatives.

Development of a novel fluorescent aptasensor based on the interaction between hexagonal β-Co(OH)2 nanoplates and nitrogen-doped carbon dots for ultrasensitive detection of patulin

There is an urgent need to develop an economical and convenient method for the ultrasensitive detection of patulin (PAT), a mycotoxin that can potentially harm human health when it is found in fruits and their derivatives. In this study, we have developed a novel fluorescent aptasensor that utilizes nitrogen-doped carbon dots (N-CDs) as the fluorescent donor and hexagonal β-Co(OH)2 nanoplates as the fluorescent acceptor. N-CDs were synthesized through the hydrothermal method, resulting in spherical particles with a diameter of 7.6 nm. These nanoparticles exhibited excellent water solubility and displayed a vibrant blue emission at 448 nm when excited at 360 nm. Cobalt hydroxide nanoplates with a beta crystal structure [β-Co(OH)2] were synthesized using a simple co-precipitation method, exhibiting hexagonal plate-like shapes with uniform lateral sizes of 4-5 μm. The fluorescence of N-CDs can be efficiently quenched by hexagonal β-Co(OH)2 nanoplates through Förster resonance energy transfer mechanism. The maximum quenching-recovery capability can be achieved when the concentrations of N-CDs-Apt and β-Co(OH)2 nanoplates are 150 nmol/L and 100 μg/mL, respectively. The pH of the TE buffer should be 8.0, and the incubation time should be 10 min at 25 °C. The developed fluorescent aptasensor displayed an excellent selectivity for PAT determination with a detection limit of 0.57 pg/mL in the linear range of 1.25 pg/mL-100 ng/mL. The rapid PAT determination in fruit juice samples was realized with good recoveries (96.9-105.8%). The developed fluorescent aptasensor based on the interaction between N-CDs and hexagonal β-Co(OH)2 nanoplates can be a promising method for the rapid and ultrasensitive detection of PAT in agricultural products.

Honey analysis in terms of nicotine, patulin and other mycotoxins contamination by UHPLC-ESI-MS/MS - method development and validation

Fifty-seven samples of honey of different types and origins were screened for nicotine and nine mycotoxins (aflatoxin B1, aflatoxin B2, fusarenon X, ochratoxin A, penicillic acid, zearalenone, sterigmatocystin, gliotoxin, and patulin). The sample set consisted of monofloral, multifloral, nectar, honeydrew, cream, and artificial honey originating mainly from Poland. The physicochemical characterization of honey was performed by determining colour (by Pfund method), water content (by refractometry), total phenolics and flavonoids content (by spectrophotometry). For nicotine and mycotoxins determination a QuEChERS-based UHPLC-ESI-MS/MS method was developed and validated. Analyses were carried out in alkaline conditions to ensure patulin-methanol adduct formation and facilitate this mycotoxin detection. About 33% of tested honey samples were contaminated by nicotine or/and mycotoxins. However, the presence of mycotoxins was not related to herein evaluated physicochemical parameters of honey samples.

[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.

Isolation and characterization of filamentous fungi capable of degrading the mycotoxin patulin

Patulin is a toxic secondary metabolite synthesized by various fungal strains. This mycotoxin is generally toxic to microorganisms as well as mammals due to its reactivity with the important cellular antioxidant glutathione. In this study, we explored the presence of microorganisms capable of degrading patulin. Microorganisms were screened for the ability to both grow in culture medium containing patulin and reduce its concentration. Screening of 510 soil samples resulted in the isolation of two filamentous fungal strains, one of which, Acremonium sp. TUS-MM1 was characterized in detail. Liquid chromatography-mass spectrometry and nuclear magnetic resonance analyses revealed that TUS-MM1 cells degraded patulin to desoxypatulinic acid. In addition, extracellular components of strain TUS-MM1 also exhibited patulin-transforming activity. High-performance liquid chromatography analysis revealed that the extracellular components generated several products from patulin. Disc diffusion assay using Escherichia coli cells revealed that the patulin-transformation products by the extracellular components are less toxic than patulin. We also demonstrated that a thermostable, low-molecular-weight compound within the extracellular components was responsible for the patulin-transforming activity. These results suggest that strain TUS-MM1 transforms patulin into less-toxic molecules by secreting a highly reactive compound. In addition, once patulin enters the cells, strain TUS-MM1 can transform it into desoxypatulinic acid to reduce its toxicity.

Immobilized short-chain dehydrogenase/reductase on Fe3O4 particles acts as a magnetically recoverable biocatalyst component in patulin bio-detoxification system

Patulin is one of the most important mycotoxins that contaminates fruit-derived products and causes acute or chronic toxicity in humans. In the present study, a novel patulin-degrading enzyme preparation was developed by taking a short-chain dehydrogenase/reductase and covalently linking it to dopamine/polyethyleneimine co-deposited magnetic Fe₃O₄ particles. Optimum immobilization provided 63% immobilization efficiency and 62% activity recovery. Moreover, the immobilization protocol substantially improved thermal and storage stabilities, proteolysis resistance, and reusability. Using reduced nicotinamide adenine dinucleotide phosphate as a cofactor, the immobilized enzyme exhibited a detoxification rate of 100% in phosphate-buffered saline and a detoxification rate of more than 80% in apple juice. The immobilized enzyme did not cause adverse effects on juice quality and could be magnetically separated quickly after detoxification to ensure convenient recycling. Moreover, it did not exhibit cytotoxicity against a human gastric mucosal epithelial cell line at a concentration of 100 mg/L. Consequently, the immobilized enzyme as a biocatalyst had the characteristics of high efficiency, stability, safety, and easy separation, establishing the first step in building a bio-detoxification system to control patulin contamination in juice and beverage products.

Isolation of the Main Pathogens Causing Postharvest Disease in Fresh Angelica sinensis during Different Storage Stages and Impacts of Ozone Treatment on Disease Development and Mycotoxin Production

Angelica sinensis, a Chinese herbal medicine, is susceptible to molds during storage, reducing its quality, and even generating mycotoxins with toxic effects on human health. Fresh A. sinensis was harvested from Min County of Gansu Province in China and kept at room temperature. Naturally occurring symptoms were observed during different storage stages. Molds were isolated and identified from the diseased A. sinensis using morphological and molecular biology methods. The impact of ozone treatment on postharvest disease development and mycotoxin production was investigated. The results indicated that A. sinensis decay began on day 7 of storage and progressed thereafter. Nine mold species were isolated and characterized: day 7, two Mucormycetes; day 14, Clonostachys rosea; day 21, two Penicillium species and Aspergillus versicolor; day 28, Alternaria alternata and Trichoderma atroviride; and day 49, Fusarium solani. Ozone treatment markedly inhibited the development of postharvest disease and the mycotoxin production (such as, patulin, 15-acetyl-deoxynivalenol, and sterigmatocystin) in the rotten tissue of A. sinensis inoculated with the nine isolates.

The Mycotoxin Patulin Inhibits the Mitochondrial Carnitine/Acylcarnitine Carrier (SLC25A20) by Interaction with Cys136 Implications for Human Health

The effect of mycotoxin patulin (4-hydroxy-4H-furo [3,2c] pyran-2 [6H] -one) on the mitochondrial carnitine/acylcarnitine carrier (CAC, SLC25A20) was investigated. Transport function was measured as [³H]-carnitine_ex/carnitine_in antiport in proteoliposomes reconstituted with the native protein extracted from rat liver mitochondria or with the recombinant CAC over-expressed in E. coli. Patulin (PAT) inhibited both the mitochondrial native and recombinant transporters. The inhibition was not reversed by physiological and sulfhydryl-reducing reagents, such as glutathione (GSH) or dithioerythritol (DTE). The IC₅₀ derived from the dose-response analysis indicated that PAT inhibition was in the range of 50 µM both on the native and on rat and human recombinant protein. The kinetics process revealed a competitive type of inhibition. A substrate protection experiment confirmed that the interaction of PAT with the protein occurred within a protein region, including the substrate-binding area. The mechanism of inhibition was identified using the site-directed mutagenesis of CAC. No inhibition was observed on Cys mutants in which only the C136 residue was mutated. Mass spectrometry studies and in silico molecular modeling analysis corroborated the outcomes derived from the biochemical assays.

Recent Progress in Electrochemical Nano-Biosensors for Detection of Pesticides and Mycotoxins in Foods

Pesticide and mycotoxin residues in food are concerning as they are harmful to human health. Traditional methods, such as high-performance liquid chromatography (HPLC) for such detection lack sensitivity and operation convenience. Efficient, accurate detection approaches are needed. With the recent development of nanotechnology, electrochemical biosensors based on nanomaterials have shown solid ability to detect trace pesticides and mycotoxins quickly and accurately. In this review, English articles about electrochemical biosensors in the past 11 years (2011-2022) were collected from PubMed database, and various nanomaterials are discussed, including noble metal nanomaterials, magnetic metal nanoparticles, metal-organic frameworks, carbon nanotubes, as well as graphene and its derivatives. Three main roles of such nanomaterials in the detection process are summarized, including biomolecule immobilization, signal generation, and signal amplification. The detection targets involve two types of pesticides (organophosphorus and carbamate) and six types of mycotoxins (aflatoxin, deoxynivalenol, zearalenone, fumonisin, ochratoxin A, and patulin). Although significant achievements have been made in the evolution of electrochemical nano-biosensors, many challenges remain to be overcome.

Brazilian Table Olives: A Source of Lactic Acid Bacteria with Antimycotoxigenic and Antifungal Activity

Food and feed contamination by fungi, especially by toxigenic ones, is a global concern because it can pose serious health problems when the production of mycotoxins is involved. Lactic acid bacteria (LAB), well-known for fermenting foods, have been gaining attention for their antifungal and anti-mycotoxin properties. This work tested 14 LAB strains isolated from naturally fermented Brazilian table olives for growth inhibition of Aspergillus flavus, Aspergillus carbonarius, Penicillium nordicum, and Penicillium expansum. The strains Lacticaseibacillus paracasei subsp. paracasei CCMA 1764, Levilactobacillus brevis CCMA 1762, and Lactiplantibacillus pentosus CCMA 1768 showed the strongest antifungal activity, being more active against P. expansum. Aflatoxin B1 (AFB1), ochratoxin A (OTA), and patulin (PAT) production was reduced essentially by mycelia growth inhibition. The main organic acids detected in the cell free supernatant (CFS) were lactic and acetic acids. Tested LAB exhibited adsorption capacity against AFB1 (48-51%), OTA (28-33%), and PAT (23-24%). AFB1 was converted into aflatoxin B2a (AFB2a) by lactic and acetic acids produced by the strain CCMA 1764. A similar conversion was observed in solutions of these organic acids (0.1 M). These findings demonstrate the potential of isolated LAB strains as natural agents to control toxigenic fungi and their mycotoxins in fermented products, such as table olives.

Development and validation of a label-free colorimetric aptasensor based on the HCR and hemin/G-quadruplex DNAzyme for the determination of patulin in fruits and fruit-based products from Xinjiang (China)

In this study, a simple, novel and practical label-free colorimetric aptasensor was successfully prepared for the ultrasensitive detection of patulin, based on the hybridization chain reaction (HCR) and hemin/G-quadruplex DNAzyme-signal amplification strategy. In this aptasensor, a detection probe was designed consisting of the aptamer sequence for the patulin and an initiator sequence to trigger the HCR. Two hairpin structures (H1 and H2) that included the G-quadruplex sequences in inactive configuration were used as functional elements. The presence of patulin triggered the opening of the hairpin structure and the beginning of the HCR. After the addition of hemin, G-rich DNA self-assembled into the peroxidase-mimicking hemin/G-quadruplex DNAzymes, which catalyzed a colorimetric reaction. Under optimized conditions, patulin was measured within a linear range of 0.1-200 ng mL^-1, and the detection limit was 0.060 ng mL^-1. The recovery rates ranged from 91.4 to 105% for fruits and fruit-based products. Subsequently, a total of 311 samples comprising fruits, fruit-based products and dried fruits were collected from supermarkets, production bases and farmers' markets in Xinjiang, and analyzed for patulin using the proposed aptasensor. Patulin was detected in 16 samples (5.14%) at concentrations ranging from 1.23 to 16.4 μg kg^-1. None of the samples exceeded the maximal level set by the EU commission (50 μg kg^-1). The positivity in fresh fruits (7.69%) was significantly higher than that of fruit-based products (4.00%) and dried fruits (1.25%). In summary, the proposed aptasensor can quickly detect patulin in food samples, thus providing a warning for mycotoxin contamination.

Bio-Layer Interferometry-Based SELEX and Label-Free Detection of Patulin Using Generated Aptamer

This study reports a novel bio-layer interferometry (BLI)-based SELEX for generation of high affinity aptamers against patulin. Unlike conventional SELEX, the present method enabled real-time monitoring of increasing affinity of the oligonucleotides to the toxin. After seven rounds of selection cycles, the enriched pool of aptamers was characterized by cloning and sequencing and clustered into two families based on similarity. Two sequences, PAT C3 and PAT C4, each belonging to different clades, were further evaluated for their binding affinity. SPR studies determined the dissociation constants (K_D) of 8.2 × 10^-8 and 1.9 × 10^-7 M for aptamer PAT C3 and PAT C4, respectively. The highest affinity PAT C3 aptamer was used to develop a patulin BLI aptasensor, which indicated a linear detection range from 0.045 to 100 ng/mL [limit of detection (LOD) = 0.173 ng/mL; limit of quantification (LOQ) = 0.526 ng/mL]. The aptasensor displayed no cross-reactivity with its structural analogue isopatulin or any of the other mycotoxin groups tested. Spiking studies in simulated apple juice samples showed recoveries in the range of 82.11 to 100.23%, indicating good sensor performance. The study is the first report of BLI-based SELEX for a non-protein toxin, which resulted in the generation of high affinity aptamers and development of an aptasensor which can have wide application in the food industry for high throughput screening of samples for patulin contamination within a short span of time.

Testing the extraction of 12 mycotoxins from aqueous solutions by insoluble beta-cyclodextrin bead polymer

Mycotoxins are toxic metabolites of filamentous fungi; they are common contaminants in numerous foods and beverages. Cyclodextrins are ring-shaped oligosaccharides, which can form host-guest type complexes with certain mycotoxins. Insoluble beta-cyclodextrin bead polymer (BBP) extracted successfully some mycotoxins (e.g., alternariol and zearalenone) from aqueous solutions, including beverages. Therefore, in this study, we aimed to examine the ability of BBP to remove other 12 mycotoxins (including aflatoxin B1, aflatoxin M1, citrinin, dihydrocitrinone, cyclopiazonic acid, deoxynivalenol, ochratoxin A, patulin, sterigmatocystin, zearalanone, α-zearalanol, and β-zearalanol) from different buffers (pH 3.0, 5.0, and 7.0). Our results showed that BBP can effectively extract citrinin, dihydrocitrinone, sterigmatocystin, zearalanone, α-zearalanol, and β-zearalanol at each pH tested. However, for the removal of ochratoxin A, BBP was far the most effective at pH 3.0. Based on these observations, BBP may be a suitable mycotoxin binder to extract certain mycotoxins from aqueous solutions for decontamination and/or for analytical purposes.

Cryptic Biosynthesis of the Berkeleypenostatins from Coculture of Extremophilic Penicillium sp

Coculture fermentation of Penicillium fuscum and P. camembertii/clavigerum yielded berkeleypenostatins A-G (1-7) as well as the previously reported berkeleylactones A-H, the known macrolide A26771B, citrinin, and patulin. As was true with the berkeleylactones, there was no evidence of the berkeleypenostatins in either axenic culture. The structures were deduced from analyses of spectral data, and the absolute configuration of berkeleypenostatin A (1) was determined by single-crystal X-ray crystallography. Berkeleypenostatins A (1) and E (5) inhibited migration of human pancreatic carcinoma cells (HPAF-II). Both compounds were tested by the NCI Developmental Therapeutics Program. In the NCI 60 cell five-dose screen, berkeleypenostatin E (5) was the more active of the two, with 1-10 μM total growth inhibition (TGI) of all leukemia cell lines, as well as the majority of colon, CNS, melanoma, ovarian, prostate, renal, and breast cancer cell lines.

Patulin Contamination of Citrus Fruits from Punjab and Northern Pakistan and Estimation of Associated Dietary Intake

This research aims to assess the natural occurrence of patulin (PAT) in selected citrus fruits from central cities of Punjab and Pakistan's northern cities. A total of 2970 fruit samples from 12 citrus cultivars were examined using liquid chromatography fitted with a UV detector. The detection limit (LOD) and quantification limit were 0.04 and 0.12 µg/kg, respectively. About 56% of samples of citrus fruits from Punjab's central cities, Pakistan, were found to be contaminated with PAT, with values ranging from 0.12 to 1150 µg/kg in samples from central Punjab cities. Furthermore, 31.7% of samples of citrus fruits from northern cities of Pakistan were contaminated with PAT, with values ranging from 0.12 to 320 µg/kg. About 22.1% of citrus fruit samples had PAT levels greater than the suggested limits established by the European Union (EU). The dietary intake levels of PAT ranged from 0.10 to 1.11 µg/kg bw/day in the central cities of Punjab, Pakistan, and 0.13 to 1.93 µg/kg bw/day in the northern cities of Pakistan.

Mitigation of Patulin in Fresh and Processed Foods and Beverages

Patulin is a mycotoxin of food safety concern. It is produced by numerous species of fungi growing on fruits and vegetables. Exposure to the toxin is connected to issues neurological, immunological, and gastrointestinal in nature. Regulatory agencies worldwide have established maximum allowable levels of 50 µg/kg in foods. Despite regulations, surveys continue to find patulin in commercial food and beverage products, in some cases, to exceed the maximum limits. Patulin content in food can be mitigated throughout the food processing chain. Proper handling, storage, and transportation of food can limit fungal growth and patulin production. Common processing techniques including pasteurisation, filtration, and fermentation all have an effect on patulin content in food but individually are not sufficient safety measures. Novel methods to remove or detoxify patulin have been reviewed. Non-thermal processing techniques such as high hydrostatic pressure, UV radiation, enzymatic degradation, binding to microorganisms, and chemical degradation all have potential but have not been optimised. Until further refinement of these methods, the hurdle approach to processing should be used where food safety is concerned. Future development should focus on determining the nature and safety of chemicals produced from the breakdown of patulin in treatment techniques.

Dietary intake of some important mycotoxins by the Swedish population

To estimate the intake of some mycotoxins from food in Sweden, approximately 600 samples were collected and analysed for aflatoxins, ochratoxin A, patulin and trichothecenes. Intakes were calculated for average and high consumers among adults and children and compared with the tolerable daily intake (TDI) of the respective toxin. Mycotoxin levels in the food samples were generally below the European/national maximum limits. However, high levels of aflatoxins were found in some samples of Brazil nuts and pistachios. The intake of ochratoxin A, patulin and trichothecenes was found to be below the temporary, TDI values (tTDI) proposed for these toxins by international expert groups, although the intake of trichothecenes (expressed as T-2 toxin equivalents) in children with a high consumption of cereals was close to the tTDI for T-2 toxin. Since there is to date no established numerical tTDI for aflatoxins, such a value was estimated for use within the project. The calculated intake of aflatoxins in high consumers exceeded this tTDI by a factor of two. In conclusion, the exposure to mycotoxins in Sweden did not generally, give rise to any major health concerns in the present study. However, the high levels of aflatoxins in certain commodities emphasize the need for preventive measures and improved control of toxin levels in these food items. Furthermore, the need for regulatory levels for trichothecenes in cereal products should be evaluated.

Procedures for destruction of patulin in laboratory wastes

Patulin is immunosuppressive and there is limited evidence of its carcinogenicity in experimental animals. The International Agency for Research on Cancer (IARC) initiated a programme for the development of degradation techniques for the commonly investigated mycotoxins. As a part of this programme, the following techniques were tested for the degradation of patulin: treatment with ammonia, treatment with ascorbic acid, and treatment with potassium permanganate in acidic or in alkaline conditions. Patulin analysis was performed by using HPLC with UV detection. Mutagenic activity of degradation residues was tested by in Salmonella typhimurium strains TA 97a, TA 98, TA 100, and TA 102. Complete disappearance of patulin was not achieved after 92 h of treatment with ascorbic acid. All the other methods tested led to complete removal of the molecule. However, the technique using potassium permanganate in acidic conditions produced residues which were mutagenic without activation to Salmonella typhimurium strains TA 100 and TA 102, which was attributed later to Mn2+. The two other techniques gave satisfactory results and were selected for further validation studies.

Strand scissions of DNA by patulin in the presence of reducing agents and cupric ions

In the presence of NADPH and CuCl2, patulin induced the cleavage of ColE1 DNA and lambda phage DNA in vitro. The DNA-cleaving activity of patulin was concentration dependent. At the lowest concentration of patulin, ColE1 supercoiled DNA was relaxed and the highest concentration induced linearization of the DNA. This activity was inhibited by superoxide dismutase, catalase and radical scavengers, showing involvement of free radicals in the DNA-cleavage. lambda Phage DNA was also degraded by patulin under the same conditions.

Toxicity of mycotoxins for the rat pulmonary macrophage in vitro

The presence of mycotoxins in grains is well documented. Workers in grain handling occupations are commonly exposed to grain dust aerosols. Work in our laboratory has shown that T-2 toxin is highly toxic to rat alveolar macrophages in vitro, causing loss of viability, release of radiolabeled chromium, inhibition of macromolecular synthesis, inhibition of phagocytosis, and inhibition of macrophage activation. Similarly, patulin caused a significant release of radiolabeled chromium, decrease in ATP levels, significant inhibition of protein and RNA synthesis, and inhibition of phagocytosis. The data show that both T-2 toxin and patulin are highly toxic to rat alveolar macrophages in vitro. The data further suggest that the presence of these mycotoxins in airborne respirable dust might present a hazard to exposed workers.

Trimming as a means of removing patulin from fungus-rotted apples

Penicillium expansum 1071, 1172, NRLL 973, and Penicillium patulum ATCC 24550 were inoculated into Red Delicious, Golden Delicious, and McIntosh apples. The decayed tissue was trimmed from the sound tissue, each fraction was weighed, and the patulin concentration in the juice was assayed by thin layer chromatography. The quantity of patulin in the whole apples and in decayed tissues was calculated and these values were used to determine the percentage of total patulin removed by trimming. The patulin content ranged from 140 to 4880 mug/apple. Trimming removed 93-99% of the total patulin, regardless of incubation temperature, fungus strain, or apple variety. Trimming of defective tissue from fungus-rotted apples could substantially reduce the patulin concentration.

Trimethylsilylation of penicillic acid and patulin, and the stability of the products

Penicillic acid and patulin have been effectively silylated by N,O-bis(trimethylsilyl)acetamide, alone or with trimethylchlorosilane in benzene. The silylation products are stable, if stored under refrigeration, for at least 15 days.