Ochratoxin A In Samples Research Articles

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.

A CdSe@CdS quantum dots based electrochemiluminescence aptasensor for sensitive detection of ochratoxin A

In this work, a CdSe@CdS quantum dots (QDs) based label-free electrochemiluminescence (ECL) aptasensor was developed for the specific and sensitive detection of ochratoxin A (OTA). Chitosan (CHI) could immobilize abundant QDs on the surface of an Au electrode as the luminescent nanomaterials. Glutaraldehyde was used as the crosslinking agent for coupling a large number of OTA aptamers. Thanks to the excellent stability, good biocompatibility, and strong ECL intensity of CdSe@CdS QDs, as well as the quick reactions of the generated SO4•− in the electrolyte, strong ECL signals were measured. Because of the specific recognition of aptamer toward OTA, the reduced ECL signals caused by OTA in the samples were recorded for quantify the content of OTA. After optimizing a series of crucial conditions, the ECL aptasensor displayed superior sensitivity for OTA with a detection limit of 0.89 ng/mL and a wide linear concentration range of 1–100 ng/mL. The practicability and viability were verified through the rapid and facile analysis of OTA in real Lily and Rhubarb samples with recovery rates (n = 3) of 98.1–105.6% and 97.3–101.5%, respectively. The newly-developed QDs-based ECL aptasensor provided a new universal analytical tool for more mycotoxins in safety assessment of foods and feeds, environmental monitoring, and clinical diagnostics.

Engineering DNA G-quadruplex assembly for label-free detection of Ochratoxin A in colorimetric and fluorescent dual modes

Colorimetric and fluorescent methods for Ochratoxin A (OTA) detection are convenient and well received. However, the pigments and autofluorescence originated from food matrices often interfere with detection signals. We have developed a strategy with colorimetric and fluorescent dual modes to solve this challenge. In the colorimetric mode, OTA aptamer (AP9) was assembled into a DNA triple-helix switch with a specially designed signal-amplifying sequence. The OTA-induced G-quadruplex (G4) of AP9 would open the switch and release the signal-amplifying sequence for colorimetric signal amplification. The G4 structures of AP9 were further utilized to combine with the fluorogenic dye ThT for fluorescent mode. By skillfully engineering DNA G4 assembly for signal amplification, there was no need for any DNA amplification or nanomaterials labeling. Detections could be carried out in a wide temperature range (22–37 ℃) and finished rapidly (colorimetric mode, 60 min; fluorescent mode, 15 min). Broad linear ranges (colorimetric mode, 10–1.5 ×103 μg/kg; fluorescent mode, 0.05–1.0 ×103 μg/kg) were achieved. The limit of detection for colorimetric and fluorescent modes were 4 μg/kg and 0.01 μg/kg, respectively. The two modes have been successfully applied to detect OTA in samples with intrinsic pigments and autofluorescence, showing their applicability and reliability.

Effects of different drying treatments on fungal population and ochratoxin A occurrence in sultana type grapes

ABSTRACTThis study aimed to determine the changes in mould and ochratoxin A (OTA) occurrence in sultanas under three different conventional drying conditions. Five different vineyards were chosen, and the three different treatments were applied to these grapes while drying. At the end of the drying process, total mould and black aspergilli (BA) populations in the samples varied from 2.45 to 5.61 log colony-forming units (CFU) g–1 and from 0 to 4.92 log CFU g–1, respectively. Significant increases (p < 0.05) occurred in mould loads depending on the extending drying period. However, independent of vineyard location, all the samples treated with cold dipping solution showed the lowest fungal loads. These results indicate that dipping solution treatment was the most effective drying method to minimise fungal infection of grapes. The expected results could not be achieved by drying grapes artificially contaminated with ochratoxigenic Aspergillus carbonarius spores. Seventy-one of 96 isolates (73.95%) obtained during drying were Aspergillus spp., and the remaining (n = 25, 26.05%) belonged to other genera, such as Penicillium, Trichoderma and Cladosporium. Grape juice-based agar medium was used to determine the realistic OTA production capacities of the isolated mould strains. The highest OTA production capacities were 809.70 ± 9.19, 87.58 ± 16.89 and 45.44 ± 18.78 ng g–1 in 50% grape juice agar (GJ50), all five of which were from A. niger isolates. OTA was not present in any sample during the drying period; however, OTA was detected in two samples at 0.32 ± 0.15 and 0.52 ± 0.36 µg kg–1 after the end of the drying process. The limit of detection (LOD) and limit of quantitation (LOQ) of the method used for detecting OTA in samples were 0.1 and 0.3 µg kg–1, respectively.

Rapid Detection of Ochratoxin A in Malt by Cytometric Bead Array Based on Indirect Competition Principle

Abstract A cytometric bead array (CBA) method based on indirect competition principle was developed for the sensitive and rapid detection of ochratoxin A (OTA) in malt. The malt samples were extracted by 60% methanol/PBS and the extracts were diluted five times with 20% methanol/PBS. After centrifugation, the supernatant was collected to prepare sample solution for analysis. The fluorescence-encoded microsphere surface was labeled with bovine serum albumin OTA (BSA-OTA) to compete with OTA in samples for anti-OTA monoclonal antibody (mAb). Then, FITC-IgG was added to bind with the captured mAb on the microsphere. After centrifugation and washing, the mean fluorescence intensity from FITC on the surface of microsphere was detected by a BD FACSCalibur analyzer for accurately qualitative and quantitative analysis of OTA. The results showed that the half inhibitory concentration (IC 50 ) was 1.20 ng mL −1 with the correlation coefficient ( R 2 ) of 0.989, and the limit of detection (LOD) for OTA was 0.12 ng mL −1 . The average recovery rates in malt samples were 93.9%–97.4% with relative standard deviations (RSDs) less than 3.6% at three spiking levels. Sixteen malt samples were analyzed and OTA was found in two samples with the contents less than 3.83 μg kg −1 which was lower than the maximum permitted residue level (5 µg kg −1 ) proposed by the European Union. All the positive samples were confirmed by LC-MS/MS. In this study, the CBA technique based on indirect competition principle was developed for the first time for successful detection of OTA in malt samples. The method was easy, rapid, sensitive and reliable with high potential for the qualitative and quantitative of multiple mycotoxins in other complex matrices.

Enhanced electrochemiluminescence of RuSi nanoparticles for ultrasensitive detection of ochratoxin A by energy transfer with CdTe quantum dots

This paper develops a new approach to enhance the electrochemiluminescence (ECL) emission of the Ru(bpy)32+-tripropyl amine (TPrA) system for ultrasensitive determination of ochratoxin A (OTA). Ru(bpy)32+-doped silica nanoparticles (RuSi NPs) act as ECL materials, which are immobilized on the surface of electrode by chitosan to fabricate a solid-state ECL sensor. CdTe quantum dots (QDs) can enhance the ECL emission of the Ru(bpy)32+-TPrA ECL system by energy transfer. This strategy can improve the sensitivity of the sensor. In this assay, we combine the ECL with molecular imprinting technique to improve the selectivity of this sensor. The template molecule could be eluted from the molecularly imprinted polymer (MIP), and the formed cavities could then selectively recognize the target. The cavities could also work as the tunnel for the transfer of coreactant TPrA to produce responsive signal. With the increase of the concentration of OTA in samples, more cavities were filled because of the rebinding of OTA to the MIP surface, resulting in a gradual decrease in ECL intensity. The results showed that the ECL decrease value depended linearly on the logarithm of the OTA concentration in the range from 1.00×10−5 to 11.13ngmL−1 with lower detection limit of 3.0fgmL−1 (S/N=3). This ECL sensor has also been applied to detect OTA concentration in the real samples with satisfied results, and the recoveries range from 85.1% to 107.9%.

Effects of different temperatures and durations of heating on the reduction of Ochratoxin A in bread samples

Ochratoxin A (OTA) is a mycotoxin produced in corn, rice, and flour. It is a major concern for animal and human health. The purpose of this study was the evaluation of OTA contamination in bread samples gathered from bakeries, in different temperatures and durations of heating. In this study, 32 samples (4 samples of flour and 28 samples of bread) were randomly collected from different bakeries in Babol city, Mazandaran province, Iran, in fall 2013. The OTA content of the samples was measured in different temperatures and durations of heating using competitive direct enzyme-linked immunosorbent assay (CD-ELISA) method. Nonparametric Kruskal-Wallis was applied for data analysis. Results proved that reduction in the amount of OTA in samples during the heating process was significant and longer duration of heating was more effective, than raising the temperature, on OTA reduction. The highest percentage of OTA reduction occurred in constant temperature and when 2 minutes were added to the original time of heating. The lowest reduction rate of this toxin was observed in constant temperature and when 4 minutes was deducted from the original time in each bakery. Our study showed that bread and flour samples do in fact contain OTA, but this toxin is being reduced through heating. Since bread is the most consumed food in the world and also Iran, determination, management, and reduction of OTA in bread should be considered seriously.

Ultrasonic extraction with ultra-performance liquid chromatography/tandem mass spectrometry for the determination of ochratoxin A in processed cereal products.

A rapid, simple, and reliable method using ultra-performance LC/MS/MS (UPLC/MS/MS) was developed for determination of ochratoxin A (OTA) in processed cereal products. OTA was ultrasonically extracted from the sample with acetonitrile-water (80 + 20, v/v), and the extract was then injected into the UPLC/MS/MS system after filtration. The calibration curves had good linearity with coefficients of determination greater than 0.999. Recoveries of OTA were in the range of 90-104%. LOD and LOQ of OTA in samples were 0.6 and 2.0 ng/g, respectively, and no significant matrix effect was found. This method was applied to determine OTA in 25 oat-based cereal samples. OTA was detected in five samples (20%) in the range of 2.4 to 7.3 ng/g.

Determination of seasonal variations in serum ochratoxin A levels in healthy population living in some regions of Turkey by enzyme-linked immunosorbent assay

This study has been undertaken to investigate the regional and seasonal variability in ochratoxin A (OTA) exposure of healthy population living in Black Sea and Mediterranean regions of Turkey by measuring serum OTA concentrations. The mean serum concentrations of OTA were determined to be 0.137 ng/mL (0.0306-0.887 ng/mL) and 0.312 ng/mL (0.028-1.496 ng/mL) in all samples for winter and summer, respectively by enzyme-linked immunosorbent assay (ELISA). The differences between mean values of OTA in all serum samples collected in summer and winter were statistically significant. The highest OTA concentration was determined in the children living in Black Sea Region in summer. The mean daily intake levels of OTA in all samples were estimated as 0.182 ng/kg b.w./day and 0.408 ng/kg b.w./day in winter and summer, respectively. The results showed that the mean serum concentrations of OTA in healthy population in both regions were found not to be exceeded 1 ng/mL in agreement with the distribution reported in most European countries and that the daily intake levels of OTA were calculated below the tolerable daily intake levels given by regulatory authorities. However, overall results suggest that Turkish population living in these regions is continuously exposed to OTA and that the exposure levels are also elevated in summer period compared to winter.