Recent progress in determination of ochratoxin a in foods by chromatographic and mass spectrometry methods

Shark anti-idiotypic variable new antigen receptor specific for an alpaca nanobody: Exploration of a nontoxic substitute to ochratoxin A in immunoassay

Nontoxic substitutes to mycotoxins can facilitate the development of eco-friendly immunoassays. To explore a novel nontoxic substitute to ochratoxin A (OTA), this study screened shark anti-idiotypic variable new antigen receptors (VNARs) against the alpaca anti-OTA nanobody Nb28 through phage display. After four rounds of biopanning of a naïve VNAR phage display library derived from six adult Chiloscyllium plagiosum sharks, one positive clone, namely, P-3, was validated through a phage enzyme-linked immunosorbent assay (phage ELISA). The recombinant anti-idiotypic VNAR AId-V3 was obtained by prokaryotic expression, and the interactions between Nb28 and AId-V3 were investigated via computer-assisted simulation. The affinity of AId-V3 for Nb28 and its heptamer Nb28-C4bpα was measured using Biacore assay. Combining Nb28-C4bpα with AId-V3, a novel direct competitive ELISA (dcELISA) was developed for OTA analysis, with a limit of detection of 0.44 ng/mL and a linear range of 1.77-32.25 ng/mL. The good selectivity, reliability, and precision of dcELISA were confirmed via cross-reaction analysis and recovery experiments. Seven commercial pepper powder samples were tested using dcELISA and validated using high-performance liquid chromatography. Overall, the shark anti-idiotypic VNAR was demonstrated as a promising nontoxic substitute to OTA, and the proposed method was confirmed as a reliable tool for detecting OTA in food.

Ready-to-use ratiometric bioluminescence immunosensor for detection of ochratoxin a in pepper

Rapid, portable, and accurate detection tools for monitoring ochratoxin A (OTA) in food are essential for the guarantee of food safety and human health. Herein, as a proof-of-concept, this study proposed a ratiometric bioluminescence immunosensor (RBL-immunosensor) for homogeneous detection of OTA in pepper. The construct of the RBL-immunosensor consists of three components, including the large fragment of the split nanoluciferase (NanoLuc)-tagged nanobody (NLg), the small fragment of the split NanoLuc-tagged mimotope peptide heptamer (MPSm), and the calibrator luciferase (GeNL). The specific nanobody-mimotope peptide interaction between NLg and MPSm induces the reconstitution of the NanoLuc, which catalyzes the Nano-Glo substrate and produces a blue emission peak at 458 nm. Meanwhile, GeNL can produce a green emission peak at 518 nm upon substrate conversion via bioluminescent resonance energy transfer (BRET). Therefore, the concentration of OTA can be linked to the variation of the bioluminescence signal (λ458/λ518) measured by microplate reader and the variation of the blue/green ratio measured by smartphone via the competitive immunoreaction where OTA competes with MPSm to bind NLg. The immunosensor is ready-to-use and works by simply mixing the components in a one-step incubation of 10 min for readout. It has a limit of detection (LOD) of 0.98 ng/mL by a microplate reader and an LOD of 1.89 ng/mL by a smartphone. Good selectivity and accuracy were confirmed for the immunosensor by cross-reaction analysis and recovery experiments. The contents of OTA in 10 commercial pepper powder samples were tested by the RBL-immunosensor and validated by high-performance liquid chromatography. Hence, the ready-to-use RBL-immunosensor was demonstrated as a highly reliable tool for detection of OTA in food.

Tuning the planarity of molecularly imprinted covalent organic frameworks for selective extraction of ochratoxin A in alcohol samples

Here, we report a monomer planarity modulation strategy for room-temperature constructing molecularly imprinted-covalent organic frameworks (MI-COFs) for selective extraction of ochratoxin A (OTA). 2,4,6-triformylphloroglucinol (Tp) was used as basic building block, while three amino monomers with different planarity were employed as modulators to explore the effect of planarity on the selectivity of MI-COFs. The MI-TpTapa constructed from Tp and the lowest planarity of monomer Tapa gave the highest selectivity for OTA, and was further used as the adsorbent for dispersed-solid phase extraction (DSPE) of OTA in alcohol samples. Coupling MI-TpTapa based DSPE with high-performance liquid chromatography allowed the matrix-effect free determination of OTA in alcohol samples with the limit of detection of 0.023 μg kg-1 and the recoveries of 91.4-97.6%. The relative standard deviation (RSD, n = 6) of intra and inter day was <3.2%. This work provides a new way to construct MI-COFs for selective extraction of hazardous targets.

A smartphone-assisted fluorescent sensing platform for ochratoxin A using Mn-doped CsPbBr3 perovskite quantum dots embedded in the mesoporous silica as a ratiometric probe

Food sources are susceptible to contamination with ochratoxin A (OTA), which is a serious threat to human health. Thus, the construction of novel, simple sensing platforms for OTA monitoring is of utmost need. Manganese-doped lead halide perovskite quantum dots encapsulated with mesoporous SiO2 (Mn-CsPbBr3 QDs@SiO2) were prepared here and used as a ratiometric fluorescent probe for OTA. Mn-CsPbBr3 QDs, synthesized at room temperature, exhibit dual emission with maximum wavelengths of 440 and 570 nm and, when embedded in the SiO2 layer, produce a stable and robust photoluminescence signal. By adding OTA to the probe, emission at 440 nm increases while emission at 570 nm decreases, so a ratiometric response is obtained. Experimental variables affecting the probe signal were studied and optimized and the mechanism of sensing was discussed. This ratiometric sensor demonstrated excellent selectivity and low detection limit (4.1 ng/ml) as well as a wide linear range from 5.0 to 250 ng/ml for OTA. A simple portable smartphone-based device was also constructed and applied for the fluorescence assay. With different OTA concentrations, the multicolor transition from pink to blue under a UV lamp led to simple visual and smartphone-assisted sensing of OTA by using a color analyzing application. Satisfactory recoveries in black tea, coffee, moldy fig and flour samples confirmed the reliability of the assay. The accuracy of the probe was proved by comparison of the results with high-performance liquid chromatography (HPLC).

Decoding chronic rhinosinusitis: A metabolomics-based approach

BACKGROUND

Chronic rhinosinusitis (CRS) is a common and intractable disease in otorhinolaryngology, laying a heavy burden on healthcare systems. The worldwide researchers are making efforts to find solutions to this disease. Metabolomics has recently gained more and more traction, and might become a promising tool to unravel the complexity of CRS. This paper provides an overview of current studies on the metabolomics of various CRS subtypes.

METHODS

We conducted a comprehensive literature search in PubMed, Web of Science, EMBASE, Google Scholar, and Cochrane Library, up to May 25, 2023. Search strategies incorporated key terms such as "chronic rhinosinusitis" and "metabolomics" with relevant synonyms and MeSH terms. Titles and abstracts of 86 screened articles were assessed for relevance to CRS and metabolomics. Methodological robustness, data reliability, and relevance were considered for shortlisted articles.

RESULTS

After the refined process, a total of 26 articles were included in this study and sorted out by research themes, methodology and pivotal discoveries. These included studies identified the metabolic pathways and markers related to the pathophysiology in each subtype of CRS.

CONCLUSIONS

Metabolomics helps to shed light on the complexity of CRS. The mentioned findings highlight the importance of specific metabolic pathways and markers in understanding the pathophysiology of CRS. Despite that, challenges and future directions in metabolomics research for CRS would be worth being further explored.

Barcode-style lateral flow immunochromatographic strip for the semi-quantitative detection of ochratoxin A in coffee samples

Ochratoxin A (OTA) is a mycotoxin contaminating agricultural products produced by fungi, associated with important toxic effects. Thus, the development of fast, sensitive, and economical approaches for OTA detection is crucial. In this study, a barcode-style lateral flow assay for the semi-quantitative detection of OTA in coffee samples was developed. To achieve this goal, a BSA-OTA complex was immobilized in three test zones to compete with OTA molecules in the sample for binding with anti-OTA antibodies labeled with gold nanoparticles. Different concentrations of OTA in the sample produced distinct colour patterns, allowing semi-quantification of the analyte. The assay exhibited high sensitivity, with a limit of detection of 2.5 µg.L-1, and high reproducibility, with variation coefficient values between 2% and 13%. Moreover, the colour patterns obtained in the analysis with coffee samples were similar to the results obtained with standard OTA solutions, demonstrating a reliable applicability in real samples.

Aptamers for nanobodies: A nontoxic alternative to toxic ochratoxin A in immunoassays

To measure toxins using immunoassays, hazardous toxin standards need to be added for quantification. To solve this problem, we propose to use aptamers as competitors to replace toxin standards. In this work, aptamers specific for ochratoxin A (OTA) nanobodies were selected using a DNA library containing a 36 nucleotide random region. The obtained sequences were highly aligned and the best competitor was identified to be a sequence named apt2-OT based on an indirect competitive enzyme-linked immunosorbent assay (ELISA). The Kd of apt2-OT was measured to be 2.86 μM using local surface plasmon resonance spectroscopy. The optimal apt2-OT was identified to substitute the OTA standard with a concentration needed for 50% inhibition of binding (IC50) of 3.26 μM based on a nontoxic direct competitive ELISA. The equivalence relationship between the aptamer and OTA was established in a flour sample, and a recovery experiment was performed. The detection limit for this method was 0.23 ng/mL, with a linear range from 0.25 to 10.50 ng/mL. The recovery rate was 97.5%-115.5%. This study provides a low-cost, rapid and environmentally friendly alternative to the development of immunoassays for toxins.

Quantification and health risk assessment of ochratoxin A in dried fruit, spices, and coffee

Ochratoxin A (OTA) is a stable toxin produced by fungal strains of Aspergillus and Penicillium. It is commonly found in a variety of food products, including dried fruit, coffee, and spices, raising concerns about their safety. This study was aimed to quantify OTA levels in different food products using HPLC with fluorescence detection. The pre-treatment process was optimised by employing immunoaffinity columns with Tween 20 to effectively remove interfering substances. An analytical method was developed, validated, and applied for OTA analysis in dried fruit, spices, and coffee samples. The validation procedure included determining detection and quantification limits, linearity, precision, and accuracy, as per the criteria specified by AOAC International. The validated method was successfully applied for OTA analysis in the selected food samples. Furthermore, health risk assessment was conducted based on the average intake and body weight of the Korean population. From the results, concentrations of OTA in the samples were found to be very low and therefore concluded not to pose significant threats to consumer health.

A simple and robust aptasensor assembled on surfactant-mediated liquid crystal interface for ultrasensitive detection of mycotoxin

Here, a simple aptasensing approach is represented to sensitively detect ochratoxin A (OTA) as one of the most perilous mycotoxins with carcinogenic, nephrotoxic, teratogenic, and immunosuppressive sequels on human health. The aptasensor is based on the alteration in the orientational order of liquid crystal (LC) molecules at the surfactant-arranged interface. Homeotropic alignment of LCs is achieved by the interaction of the surfactant tail with LCs. By perturbing the alignment of LCs due to the electrostatic interaction of the aptamer strand with the surfactant head, a colorful polarized view of the aptasensor substrate is induced drastically. While OTA causes the re-orientation of LCs to a vertical state by forming an OTA-aptamer complex that induces darkness of the substrate. This study shows that the length of the aptamer strand impacts the efficiency of the aptasensor; longer strand results in the greater disruption of LCs, and therefore, increases the aptasensor sensitivity. Hence, the aptasensor can determine OTA in the linear concentration range of 0.1 fM-1 pM as low as 0.021 fM. The aptasensor is capable to monitor OTA in grape juice, coffee drink, corn, and human serum real samples. The proposed LC-based aptasensor provides a cost-effective, easy-to-carry, operator-independent, and user-friendly array with great potential to develop portable sensing gadgets for food quality control and health care monitoring.

The Electrochemical Detection of Ochratoxin A in Apple Juice via MnCO3 Nanostructures Incorporated into Carbon Fibers Containing a Molecularly Imprinting Polymer

A novel electrochemical sensor based on MnCO3 nanostructures incorporated into carbon fibers (MnCO3NS/CF), including a molecularly imprinting polymer (MIP), was developed for the determination of Ochratoxin A (OTA). In this study, a sensitive and selective sensor design for OTA detection was successfully performed by utilizing the selectivity and catalysis properties of MIP and the synthesized MnCO3NS/CF material at the same time. MnCO3 nanostructures incorporated into carbon fibers were first characterized by using various analytical techniques. The sensor revealed a linearity towards OTA in the range of 1.0 × 10-11-1.0 × 10-9 mol L-1 with a detection limit (LOD) of 2.0 × 10-12 mol L-1. The improved electrochemical signal strategy was achieved by high electrical conductivity on the electrode surface, providing fast electron transportation. In particular, the analysis process could be finished in less than 5.0 min without complex and expensive equipment. Lastly, the molecular imprinted electrochemical sensor also revealed superior stability, repeatability and reproducibility.

Sensitive microscale thermophoresis assay for rapid ochratoxin A detection with fluorescently labeled engineered aptamer

Ochratoxin A (OTA) is a widespread mycotoxin that causes contamination in a variety of foodstuffs and environments, inducing great health risks to humans and animals. Rapid and sensitive detection of OTA is necessary for food safety, environmental health, and risk assessment. Herein, we report an aptamer microscale thermophoresis (MST) assay for OTA, with the unique merits of ratiometric analysis, rapid measurement, simple operation, high sensitivity, low sample consumption, and high throughput. A fluorescein (FAM)-labeled high-affinity DNA aptamer with a G-quadruplex and duplex structure was used as the recognition element for OTA, and MST, which measures the fluorescence responses of the sample solution inside capillaries to a mild temperature increase generated by infrared laser heating, was employed for signal generation. Upon OTA binding, the FAM-labeled aptamer probe underwent changes in conformation and stability, and the bound and unbound aptamer probes showed significant differences in their MST signals. To achieve sensitive detection of OTA with a large signal change, we systematically characterized aptamers with different stem lengths, which had large effects on the MST responses of the aptamer probes to OTA. We found that a 32-mer aptamer with FAM label at the 3' end gave a sensitive MST response to OTA, allowing OTA detection within seconds with a detection limit of 0.98 nM under optimal experimental conditions. This aptamer MST assay shows potential in real sample analysis and broad applications.

Nanobody-based magnetic chemiluminescence immunoassay for one-pot detection of ochratoxin A

Ochratoxin A (OTA) contamination seriously threatens food safety and human health and requires sensitive and rapid tools for monitoring. In this study, a convenient enzyme-linked immunosorbent assay based on Avi-labeled nanobody Nb-2G/streptavidin-alkaline phosphatase and magnetic beads (MBS-ELISA) was established for the sensitive detection of OTA, which could be used for one-pot detection without immobilization. After optimization, the 50% inhibitory concentration (IC50) and the lowest limit of detection value of the MBS-ELISA was 1.17 ng/mL and 0.07 ng/mL and the linear range was 248.8 pg/mL-5.28 ng/mL, respectively, which accords with state criteria for food safety. The developed one-step MBS-ELISA was almost 20-times more sensitive than the classic BA-ELISA and could generate results within 15 min, which was significantly less than the classic BA-ELISA at approximately 3 h. The MBS-ELISA indicated good recovery (86.4-114.3%) in spiked sorghum, buckwheat, and mung bean. Thus, MBS-ELISA represents a very promising strategy for the simple, rapid, and accurate detection of OTA and other toxic and hazardous contaminants.

Research progress of ochratoxin a bio-detoxification

Ochratoxins (OTs) is an extremely toxic mycotoxin in which Ochratoxin A (OTA) is the most toxic and prevalent in the ochratoxin family. OTA is among the five most critical mycotoxins that are subject to legal regulations. Animals and humans may be exposed to OTA through dietary intake, inhalation, and dermal contact. OTA is considered nephrotoxic, genotoxic, cytotoxic, teratogenic, carcinogenic, mutagenic, immunotoxic, and myelotoxic. So, intake of OTA contaminated foods and feeds can impact the productivity of animals and health of people. According to this review, several studies have reported on the approaches that have been established for OTA removal. This review focused on the control approaches to mitigate OTA contamination, OTA bio-detoxification materials and their applicable techniques, recombinant strains for OTA bio-detoxification, and their detoxification effects, recombinant OTA-degrading enzymes and their sources, recombinant fusion enzymes for OTA, ZEN and AFB1 mycotoxins detoxification, as well as the current application and commercialized OTA bio-detoxification products. However, there is no single technique that has been approved to detoxify OTA by 100% to date. Some preferred current strategies for OTA bio-detoxification have been recombinant degrading enzymes and genetic engineering technology due to their efficiency and safety. Therefore, prospective studies should focus on standardizing pure enzymes from genetically engineered microbial strains that have great potential for OTA detoxification.

Bifunctional M13 Phage as Enzyme Container for the Reinforced Colorimetric-Photothermal Dual-Modal Sensing of Ochratoxin A

"Point of care" (POC) methods without expensive instruments and special technicians are greatly needed for high-throughput analysis of mycotoxins. In comparison, the most widely used screening method of the conventional enzyme-linked immunosorbent assay (ELISA) confronts low sensitivity and harmful competing antigens. Herein, we develop a plasmonic-photothermal ELISA that allows precise readout by color-temperature dual-modal signals based on enzymatic reaction-induced AuNP aggregation for highly sensitive detection of ochratoxin A (OTA). The bifunctional M13 phage carrying OTA that mimics the mimotope on the end of p3 proteins and abundant biotin molecules on the major p8 proteins is adopted as an eco-friendly competing antigen and enzyme container for amplifying the signal intensity. Under optimal conditions, both colorimetric and photothermal signals enable good dynamic linearity for quantitative OTA detection with the limits of detection at 12.1 and 8.6 pg mL-1, respectively. Additionally, the proposed ELISA was adapted to visual determination with a cutoff limit of 78 pg mL-1 according to a vivid color change from deep blue to red. The recoveries of OTA-spiked corn samples indicate the high accuracy and robustness of the proposed method. In conclusion, our proposed strategy provides a promising method for eco-friendly and sensitive POC screening of OTA. Moreover, it can be easily applied to other analytes by changing the involved specific mimotope sequence.

The Occurrence and Contamination Level of Ochratoxin A in Plant and Animal-Derived Food Commodities

Ochratoxin A (OTA) is a highly toxic mycotoxin and poses great threat to human health. Due to its serious toxicity and widespread contamination, great efforts have been made to evaluate its human exposure. This review focuses on the OTA occurrence and contamination level in nine plant and animal derived food commodities: cereal, wine, coffee, beer, cocoa, dried fruit, spice, meat, and milk. The occurrence and contamination level varied greatly in food commodities and were affected by many factors, including spices, geography, climate, and storage conditions. Therefore, risk monitoring must be routinely implemented to ensure minimal OTA intake and food safety.

Enzyme cascade-amplified immunoassay based on the nanobody-alkaline phosphatase fusion and MnO2 nanosheets for the detection of ochratoxin A in coffee

Ochratoxin A (OTA) is a common food contaminant with multiple toxicities and thus rapid and accurate detection of OTA is indispensable to minimize the threat of OTA to public health. Herein a novel enzyme cascade-amplified immunoassay (ECAIA) based on the mutated nanobody-alkaline phosphatase fusion (mNb-AP) and MnO2 nanosheets was established for detecting OTA in coffee. The detection principle is that the dual functional mNb-AP could specifically recognize OTA and dephosphorylate the ascorbic acid-2-phosphate (AAP) into ascorbic acid (AA), and the MnO2 nanosheets mimicking the oxidase could be reduced by AA into Mn2+ and catalyze the 3,3',5,5'-tetramethyl benzidine into blue oxidized product for quantification. Using the optimal conditions, the ECAIA could be finished within 132.5 min and shows a limit of detection of 3.38 ng mL-1 (IC10) with an IC50 of 7.65 ng mL-1 and a linear range (IC20-IC80) of 4.55-12.85 ng mL-1. The ECAIA is highly selective for OTA. Good recovery rates (84.3-113%) with a relative standard deviation of 1.3-3% were obtained and confirmed by high performance liquid chromatography with a fluorescence detector. The developed ECAIA was demonstrated to be a useful tool for the detection of OTA in coffee which provides a reference for the analysis of other toxic small molecules.