Simultaneous Rapid Detection of Aflatoxin B1 and Ochratoxin A in Spices Using Lateral Flow Immuno-Chromatographic Assay

Dual-mode detection of Ochratoxin A based on silver nanocluster and phosphate

Ochratoxin A (OTA) is widely present in the environment and has great harm to human safety. Therefore, a simple and sensitive method for OTA detection is urgently needed. Herein, a fluorescence and colorimetric dual-mode immunoassay based on glutathione silver nanocluster (GSH-AgNCs) and phosphate colorimetry was established. For fluorescence mode, the pyrophosphate ion (PPi) can reduce the fluorescence of GSH-AgNCs@Al3+ by chelating Al3+. Meanwhile, the fluorescence can be recovered when PPi is hydrolyzed to phosphate ion (Pi) by alkaline phosphatase (ALP.) For colorimetric mode, Pi can be quantitatively analyzed by MoSb colorimetric method. The linear range of fluorescence mode was 1.25-35 ng/mL with limit of detection (LOD) of 0.54 ng/mL. For colorimetric mode, the linear range and LOD was 6.25-250 ng/mL and 3.13 ng/mL. The detection limits are much lower than the European Union's regulations. And this dual-mode immunoassay showed a satisfactory recovery rate and specificity in detecting real samples.

Triple-readout immunoassay based on copper ion trigger for the detection of ochratoxin A

BACKGROUND

Ochratoxin A (OTA) is a widespread mycotoxin with nephrotoxic, neurotoxic and immunotoxic properties. It exhibits elevated thermal stability and a prolonged half-life and is resistant to removal. Long-term exposure to OTA increases the risk of carcinogenesis and influences human health. The detection methods of single signal mode had poor anti-interference ability and were prone to false positive results, while the detection method of multi-signal mode has higher adaptability to conditions and can offset environmental interference through self-correction. Therefore, proposing multi-signal and high-sensitivity strategies to detect OTA levels in various foods is all-important.

RESULTS

A triple-readout immunoassay based on copper ions trigger was developed for detecting Ochratoxin A. The ascorbic acid 2-phosphate (AAP) was hydrolyzed to ascorbic acid (AA) by alkaline phosphatase (ALP). The unreacted AAP rapidly coordinated with Cu2+ to produce green Cu2+-AAP complexes which emitted blue/green (B/G) signals. Meanwhile, Cu2+ oxidized AA to produce dehydroascorbic acid (DHAA) which reacted with o-phenylenediamine (OPD) to form the blue-fluorescence quinoxaline derivative (DFQ). Simultaneously, Cu2+ oxidized the unreacted OPD to form yellow 2,3-diaminophenazine (DAP) which produced yellow signals (Y). The B/G and Y was read by a smartphone. The limits of detection (LOD) of B/G, fluorescence and Y value readout models were 0.13 ng/mL, 0.16 ng/mL and 0.15 ng/mL. Their linear ranges were 6.25-100 ng/mL, 6.25-200 ng/mL and 3.13-12.5 ng/mL. Besides, all three readout models showed excellent specificity for OTA, and the recovery rates were satisfactory from 94.79 % to 112.68 %.

SIGNIFICANCE

A triple-readout immunoassay based on copper ions trigger for the detection of ochratoxin A was constructed. The materials for detection are accessible and economical. Triple signal modes not only complement and verify each other to improve the reliability of the results but also can be selected according to the detection scenes to increase the freedom of detection. It can be used to detect other targets by altering the coated antigen and its corresponding antibody.

Risk assessment of aflatoxin in Iowa corn post-harvest using an event tree analysis: A case study

Mycotoxins are secondary metabolites produced by fungi found in corn and are anticipated to increase globally due to enhanced weather extremes and climate change. Aflatoxin (AFL) is of concern due to its harmful effects on human and animal health. AFL can move through complex grain supply chains in the United States, including multiple stakeholders from farms, grain elevators, grain and ethanol processors, and feed mills, before reaching end users, putting numerous entities at risk. Since corn is an essential food and feed product, risk management of AFL must be considered. This case study aimed to (1) calculate the probabilities of pivotal events with AFL in corn at Food Safety Modernization Act-regulated entities using an event tree analysis (ETA) and (2) propose recommendations based on factors identified through the ETA for AFL risk management. The ETA was based on historical AFL prevalence data in Iowa above a 20-part per billion (ppb) threshold (2.30%). Results showed four single-point failures in feed safety systems, where countermeasures did not function as designed. Failure is defined as the type 2 error of corn being infected with AFL <20 ppb, when it is >20 ppb, and the overall system fails to detect this with contaminated corn reaching end users. The success rate is defined as detecting the corn samples correctly >20 ppb. The average success rate was 50.14%, and the failure rate was 49.86%. It was concluded that risk-informed decisions are a critical component of effective AFL monitoring in corn, with timely intervention strategies needed to minimize the overall effects on end users.

Detection of Total Aflatoxins in Herbal Medicines Based on Lateral Flow Assay with Contamination Ratio Model

In this study, we developed a colloidal gold immunochromatographic strip (CGIS) method that used the matrix-matched calibration curves of contamination ratio models to quantitatively determine the total aflatoxin in five herbal medicines. This approach addresses issues related to false results and poor accuracy associated with conventional methods. The CGIS was analyzed using a Vertu touch reader, and the matrix-matched calibration was established based on the absorbance ratios of the T and C lines, as well as the logarithmic values of the total aflatoxin concentrations. The total aflatoxins could be accurately and digitally detected from 2.5 to 40 μg/kg, and the LOD of total aflatoxins was 1 μg/kg in the five herbal medicines. The recovery rates from the spiked samples ranged from 65.1% to 98.6%, and the RSD was less than 16.9%. A total of 229 samples were analyzed by both CGIS and HPLC-FLD, with agreement ranging from 78.4% to 132.6% (Arecae semen), 82.6% to 133.0% (Nelumbinis semen), 79.9% to 117.9% (Coicis semen), 78.1% to 119.0% (Platycladi semen), and 76.1% to 123.0% (Ziziphi spinosae semen). This process for the discrimination of the CGIS results was established to assess if samples met the requirement of aflatoxin limits, which could save approximately 75% in time and reduce the workload of retesting by a designated confirmatory reference method to less than 10%. This study demonstrated that the application of matrix-matched calibration curves based on contamination ratio models to CGIS can effectively enhance the rapid quantitative determination capability of total aflatoxins in herbal medicine matrices.

Comprehensive Review of Aflatoxin and Ochratoxin A Dynamics: Emergence, Toxicological Impact, and Advanced Control Strategies

Filamentous fungi exhibit remarkable adaptability to diverse substrates and can synthesize a plethora of secondary metabolites. These metabolites, produced in response to environmental stimuli, not only confer selective advantages but also encompass potentially deleterious mycotoxins. Mycotoxins, exemplified by those originating from Alternaria, Aspergillus, Penicillium, and Fusarium species, represent challenging hazards to both human and animal health, thus warranting stringent regulatory control. Despite regulatory frameworks, mycotoxin contamination remains a pressing global challenge, particularly within cereal-based matrices and their derived by-products, integral components of animal diets. Strategies aimed at mitigating mycotoxin contamination encompass multifaceted approaches, including biological control modalities, detoxification procedures, and innovative interventions like essential oils. However, hurdles persist, underscoring the imperative for innovative interventions. This review elucidated the prevalence, health ramifications, regulatory paradigms, and evolving preventive strategies about two prominent mycotoxins, aflatoxins and ochratoxin A. Furthermore, it explored the emergence of new fungal species, and biocontrol methods using lactic acid bacteria and essential mustard oil, emphasizing their efficacy in mitigating fungal spoilage and mycotoxin production. Through an integrative examination of these facets, this review endeavored to furnish a comprehensive understanding of the multifaceted challenges posed by mycotoxin contamination and the emergent strategies poised to ameliorate its impact on food and feed safety.

Advances in Aptamer-Based Conjugate Recognition Techniques for the Detection of Small Molecules in Food

Small molecules are significant risk factors for causing food safety issues, posing serious threats to human health. Sensitive screening for hazards is beneficial for enhancing public security. However, traditional detection methods are unable to meet the requirements for the field screening of small molecules. Therefore, it is necessary to develop applicable methods with high levels of sensitivity and specificity to identify the small molecules. Aptamers are short-chain nucleic acids that can specifically bind to small molecules. By utilizing aptamers to enhance the performance of recognition technology, it is possible to achieve high selectivity and sensitivity levels when detecting small molecules. There have been several varieties of aptamer target recognition techniques developed to improve the ability to detect small molecules in recent years. This review focuses on the principles of detection platforms, classifies the conjugating methods between small molecules and aptamers, summarizes advancements in aptamer-based conjugate recognition techniques for the detection of small molecules in food, and seeks to provide emerging powerful tools in the field of point-of-care diagnostics.

Evaluating aflatoxins and Sudan dyes contamination in red chili and turmeric and its health impacts on consumer safety of Lahore, Pakistan

Spices are contaminated with aflatoxins (AFs) and Sudan dyes which are classified as class Group 1 and Group 3 human carcinogens by the International Agency for Research on Cancer (IARC) respectively and their prolonged exposure may raise a human health concern. A total of 474 samples of red chili and turmeric were collected from Lahore city and were subjected to quantitative and qualitative AFs and Sudan dyes analysis by thin layer chromatography (TLC) respectively. The number of red chili and turmeric samples with ≥10 μg/kg of total AFs (European Union standard limit) were 70% and 33% respectively and considered unfit for human consumption. The presence of Sudan dyes in red chili and turmeric samples was 67% and 27% respectively. The mean estimated daily intake (EDI) among females and males was 0.0019 μg/kg bw/day, 0.0012 μg/kg bw/day for red chili, and 0.0008 μg/kg bw/day, 0.0006 μg/kg bw/day for turmeric respectively. The mean value of margin of exposure (MOE) among females and males for ingestion of AFs-contaminated red chili and turmeric was 210.25, 332.13, 501.02, and 699.31 respectively. Therefore, the current study demands a continuous monitoring plan and the implementation of novel techniques to enhance the product's quality and protect public health.

Evaluation of ELISA and immunoaffinity fluorometric analytical tools of four mycotoxins in various food categories

Mycotoxins (MTs) are secondary toxic metabolites that can contaminate food, impacting quality and safety, leading to various negative health effects and serious pathological consequences conferring urgent need to evaluate and validate the currently standard methods used in their analysis. Therefore, this study was aimed to validate ELISA and VICAM immunoaffinity fluorometric, the two common methods used to monitor the level of MTs according to the Egyptian Organization for Standardization and Quality Control. A total of 246 food samples were collected and tested for Aflatoxins (196 samples), Ochratoxin A (139), Zearalenone (70), and Deoxynivalenol (100) using both analytical methods. Results showed that aflatoxins exceeded limits in 42.9, 100, and 13.3% of oily seeds, dried fruits, and chili and spices, respectively. For ochratoxin A, 3.9% of Gramineae and 8% of spices and chili (locally sourced) exceeded the limits, while 17.6% of imported pasta and noodles exceeded the limits for deoxynivalenol. Significant differences for the aflatoxins and ochratoxin A detection among different categories of chocolate, dried fruits, and oily seeds (p-value < 0.05). No zearalenone contamination was detected in the exported, imported, and locally sourced categories. No deoxynivalenol contamination was detected in the tested Gramineae category. In contrast, for pasta and noodles, the imported samples exhibited the highest contamination rate (above the upper limit of 750 µg/kg) with 17.6% of the samples testing positive for deoxynivalenol with no significant difference among different sample categories of Gramineae, pasta, and noodles (p-value > 0.05). In conclusion, our study found no significant differences between the ELISA and immunoaffinity fluorometric analysis in the detection of the respective MTs in various food categories and therefore, they can substitute each other whenever necessary. However, significant differences were observed among different food categories, particularly the local and imported ones, highlighting the urgent need for strict and appropriate control measures to minimize the risk of MTs adverse effects.

Chromatographic methods for rapid aflatoxin B1 analysis in food: a review

Aflatoxin B1 (AFB1) is a mycotoxin and is the most carcinogenic of all known chemicals. In view of the AFB1 characteristics of widespread distribution, serious pollution, great harm to humans, and animals and difficult to remove, it is urgent to develop a convenient and sensitive detection method. Moreover, chromatographic test strips (CTSs) are a rapid detection technology that combines labeling technology with chromatography technology. CTSs have been widely used in the fields of environmental monitoring, medical diagnosis, and food safety analysis in recent years. Different from other immune assays, they have the advantages of short measuring time, low cost, high efficiency and no need for professionals to operate. In addition, the introduction of nanomaterials has laid a good foundation for the detection of high sensitivity, high specificity and high efficiency via CTSs. Herein, we tend to comprehensively introduce the applications of chromatographic methods in AFB1 detection and pay attention to the signal detection modes based on nanomaterials in antibody-based immunochromatographic strips (ICSs), such as colorimetric, fluorescent, chemiluminescent, and Raman scattering sensing. Some typical examples are also listed in this review. In the end, we make a summary and put forward prospects for the development of CTSs.

Development of a Lateral Flow Strip with a Positive Readout for the On-Site Detection of Aflatoxin B1

Aflatoxin B₁ is one of the contamination indicators for food safety monitoring. The rapid and effective assessment and determination of AFB₁ in food is of great importance to dietary safety. The lateral flow assay shows advantages in its simplicity, and rapidity, and provides a visual readout, while the available lateral flow assay for AFB₁ requires a competitive format that produces readings inversely proportional to the AFB₁ concentration, which is counterintuitive and may lead to a potential misinterpretation of the results. Herein, we developed a positive readout aptamer-based lateral flow strip (Apt-strip) for the detection of AFB₁. This Apt-strip relies on the competition between AFB₁ and fluorescein-labeled complementary DNA strands (FAM-cDNA) for affinity binding to limited aptamers against AFB₁ (AFB₁-Apt). In the absence of AFB₁, AFB₁-Apt hybridizes with FAM-cDNA. No signal at the T-line of the Apt-strip was observed. In contrast, AFB₁-Apt binds to AFB₁ in the sample, and then a part of the FAM-cDNA is hybridized with the free AFB₁-Apt, at which time the other unreacted FAM-cDNA is captured by A35-Apt on the T-line. The signal was observed. This method achieved fast detection of AFB₁ with a detection limit (DL) of 0.1 ng/mL, positive readout, and increased sensitivity.

Editorial to Special Issue-Research on Isolation and Intelligent Detection Methods of Foodborne Pathogens

Foodborne illnesses pose a significant threat worldwide to public health [...].

Mineral and Microbiological Analysis of Spices and Aromatic Herbs

Spices and aromatic herbs have always had great historical importance in human nutrition. Their use has been documented for centuries as a rich source of bioactive compounds; they have been used for their health benefits and also for flavoring or coloring food. However, despite the many health properties linked to the use of spices and aromatic herbs, these can represent biological hazards and can contain chemical substances of concern. Certainly, monitoring potential health hazards in spices and aromatic herbs includes microbiological safety and also the content of inorganic substances: both represent a key step. This research aims at monitoring the compliance of various spices and aromatic herbs from a non-European country market (namely: black cumin seeds, Iranian Tokhme Sharbati, clove buds, Shahjeera, Abbaszadeh saffron, organic fenugreek, whole black pepper, cinnamon, Abthul Ahmar (Asario), Ajwan seeds, whole coriander seeds, black sesame seeds, Sabja seeds) with the current European Union (EU) and WHO regulations, when available, regarding mineral and microbiological parameters. In particular, microbiological assays using rapid and conventional methods, and trace mineral determination by inductively coupled plasma mass spectrometry (ICP-MS) were performed. Results show the safety of the tested spices, given that the microbiological parameters were within the legal microbiological criteria set by the European Commission Regulation (EC) No. 2073/2005 and its amendment Regulation (EC) No. 1441/2007. With reference to potentially toxic Cd, Pb, As, Hg, these were within the limits set by the European Commission Regulation (EC) No. 1881/2006 and its amendments, Regulation (EU) No. 1317/2021 and Regulation (EU) No. 1323/2021, and WHO. According to EU regulations, for Pb content, 2 samples out of 16 showed values different from the set limits.