Detection Of Ochratoxin Research Articles

A Novel Four-Modal Nano-Sensor Based on Two-Dimensional Mxenes and Fully Connected Artificial Neural Networks for the Highly Sensitive and Rapid Detection of Ochratoxin A

Timely and accurate on-site detection of ochratoxin A (OTA) is extremely important for global public health. In this study, a fluorescence/colorimetric biosensor based on Ti3C2 nano-materials (Ti3C2-NMS) and a machine-learning (ML) based fluorescence/colorimetric intelligent learning system for detection of OTA concentration (COTA) were developed. The sensor was fabricated by functionalizing Ti3C2-NMS prepared by physical-exfoliation assisted metal-ion-induction using ssDNA. The Ti3C2-NMS exhibited good fluorescence quenching characteristics (FQC) and peroxidase-like activity (PLA). More surprisingly, the functionalization of Ti3C2-NMS by ssDNA further enhanced the FQC and PLA of the material, which could be used for dual-mode detection of OTA. When different COTA existed, ssDNA competitively bound to OTA, resulting in regular changes in fluorescence and colorimetric signals of the sensor, which realized the accurate and sensitive biosensing detection of OTA in two modalities. Based on a series of fluorescent/colorimetric RGB datasets collected by a self-developed application, a dual-channel ML model had been developed. This model can be integrated into mobile phones, clouds, and PCs to achieve intelligent sensing detection of OTA with the assistance of fully connected artificial neural networks. The method constructed had high specificity, low cost, and fast responsiveness, with a LOD as low as 1.58 pg mL-1, indicating excellent potential for application and promotion.

Smartphone-based dual-mode aptasensor with bifunctional metal-organic frameworks as signal probes for ochratoxin A detection

Ochratoxin A (OTA) poses significant risks to human health, being potentially nephrotoxic, carcinogenic, genotoxic, and immuno-toxic. In this work, we developed a dual-mode aptasensor for OTA analysis, integrating colorimetric, electrochemical, and smartphone-based detection. The bifunctional Fe-MIL-88 metal-organic framework, acting as both a nanozyme capable of catalyzing the 3,3′,5,5′-tetramethylbenzidine substrate and an electrochemical signal amplifier, enabled OTA quantification through current response or changes in color and absorbance intensity. Besides, the spatial confinement effect enhances the local concentration of Fe-MIL-88 signal probes through rolling circle amplification reaction, thereby contributing to a substantial enhancement in sensitivity. The proposed technique is simple, disposable, highly sensitive and selective, enabling OTA detection in the range of 1 fg/mL to 250 ng/mL, with a limit of detection of 0.22 fg/mL (3σ rule). Furthermore, we successfully detected OTA in corn, wheat, and red wine samples, with results good concordance with those obtained using commercial enzyme-linked immunoassay kits.

Presence of Ochratoxin A Residues in Blood Serum of Slaughtered Pigs in Greece.

This study aimed to assess the presence of ochratoxin A (OTA) residues in the blood serum of slaughtered pigs in Greece. Samples were obtained from 1695 healthy slaughtered pigs originating from 113 different farms located in 21 geographic regional units in 8 different geographic regions of Greece and were analyzed using an immunosorbent assay (ELISA) and high-performance liquid chromatography with fluorescence detector (HPLC-FD). OTA contamination assessment showed that 782 (46.1%) and 1233 (72.7%) samples were OTA-positive, with a concentration range of 0.20-5.38 μg/L and 0.15-5.96 µg/L according to ELISA and HPLC-FD analysis, respectively. Also, 88 (77.9%) and 108 (95.6%) of farms were found to be OTA-positive by ELISA and HPLC-FD analysis, respectively. The highest OTA serum positivity rate (>98%) and toxin level (5.96 µg/L) determined by HPLC-FD were observed in the Thessaly region, whereas a high prevalence of up to 100% (range 75-100%) was found on farms in the Crete Island region. The detection of OTA in the serum of slaughtered pigs in different regions in Greece poses a risk for animal and human health and highlights the need for constant OTA monitoring in the swine industry and pork meat production facilities.

Dual improved enzyme-linked immunosorbent assay based on multivalent bifunctional nanobody and polymerized horseradish peroxide for the ultrasensitive detection of Ochratoxin A in coffee samples

Enzyme-linked immunosorbent assay (ELISA) is favored for its high throughput, low cost, and simplicity, but the limited sensitivity of the traditional colorimetric ELISA restricts its wider application. Therefore, developing improvement strategies to enhance its sensitivity is a current research hotspot. In this work, we developed a multivalent bifunctional nanobody (Nb28-C4-SBP) by fusing a nanobody gene (Nb28) against ochratoxin A (OTA) with a self-assembling peptide (C4) and a streptavidin-conjugated peptide (SBP), which can introduce streptavidin-conjugated polymerized horseradish peroxidase (SA-PolyHRP) as a probe into the detection system. Subsequently, a dual improved ELISA (DI-ELISA) was developed using the higher affinity multivalent bifunctional nanobody (Nb28-C4-SBP) and the more enzyme-loaded probe (SA-PolyHRP) for the ultrasensitive detection of OTA in coffee samples. The DI-ELISA demonstrated a detection limit of 1 pg/mL, which was about 20-fold lower than that of the Nb28-C4-SBP and SA-HRP based ELISA and 266-fold lower than that of the Nb28-SBP and SA-PolyHRP based ELISA, respectively. In summary, we developed an ultrasensitive, rapid, and simple immunoassay for detecting OTA in coffee samples. Additionally, the proposed improvement strategy based on multivalent nanobody and polymerized horseradish peroxide is straightforward to operate and holds great potential for enhancing the sensitivity in various immunoassays.

Electrochemiluminescence immunoassay system based on PCN-224-Mn and gold-platinum bimetallic nanoflowers for sensitive detection of ochratoxin A

In this work, a novel Electrochemiluminescence Immunosensor was constructed using PCN-224-Mn and gold-platinum nanoflowers (AuPt NFs) for the ultrasensitive detection of ochratoxin A (OTA). PCN-224 modified with Mn (II) was synthesized as a probe material. The interaction efficiency of PCN-224 with S2O82− was also greatly improved. AuPt NFs were used as the substrate material for the electrodes. It has favorable biocompatibility, large specific surface area and can bind more antigen. Also greatly increased the electroactive surface area and conductivity of the electrode. OTA was detected using a competitive immunoassay strategy, in which OTA in the sample competes with the encapsulated antigen for a finite number of antibodies. ECLIA for the detection of OTA was designed to be highly sensitive, with a linear range from 0.0002 ng mL−1 to 1000 ng mL−1 and a LOD as low as 0.067 pg mL−1. In addition, it was evident from the electrochemical analyses that PCN-224-Mn had a stronger and more stable ECL signal compared to the plain PCN-224. The successful preparation of specific, sensitive and reproducible ECL immunosensors confirms the great promise for the detection of OTA or other small molecule mycotoxins.

SERS aptasensor for simultaneous detection of ochratoxin A and zearalenone utilizing a rigid enhanced substrate (ITO/AuNPs/GO) combined with Au@AgNPs

The contamination of mycotoxins poses a serious threat to global food security, hence the urgent need for simultaneous detection of multiple mycotoxins. Herein, two SERS nanoprobes were synthesized by embedded SERS tags (4-mercaptopyridine, 4MPy; 4-mercaptobenzonitrile, TBN) into the Au and Ag core–shell structure, and each was coupled with the aptamers specific to ochratoxin A (OTA) and zearalenone (ZEN). Meanwhile, a rigid enhanced substrate Indium tin oxide glass/AuNPs/Graphene oxide (ITO/AuNPs/GO) was combined with aptamer functionalized Au@AgNPs via π-π stacking interactions between the aptamer and GO to construct a surface-enhanced Raman spectroscopy (SERS) aptasensor, thereby inducing a SERS enhancement effect for the effective and swift simultaneous detection of both OTA and ZEN. The presence of OTA and ZEN caused signal probes dissociation, resulting in an inverse correlation between Raman signal intensity (1005 cm−1 and 2227 cm−1) and the concentrations of OTA and ZEN, respectively. The SERS aptasensor exhibited wide linear detection ranges of 0.001–20 ng/mL for OTA and 0.1–100 ng/mL for ZEN, with low detection limits (LOD) of 0.94 pg/mL for OTA and 59 pg/mL for ZEN. Furthermore, the developed SERS aptasensor demonstrated feasible applicability in the detection of OTA and ZEN in maize, showcasing its substantial potential for practical implementation.

Zero-Background Dual-Mode Closed Bipolar Electrode Electrochemiluminescence Biosensor Based on ZnCoN-C Potential Regulation for Ultrasensitive Detection of Ochratoxin A.

In this work, the relationship between electrochemiluminescence (ECL) signal and driving voltage was first studied by self-made reduced and oxidized closed bipolar electrodes (CBPEs). It was found that when the driving voltage was large enough, the maximum ECL signals for the two kinds of CBPEs were the same but their required drive voltages were different. Zinc cobalt nitrogen doped carbon material (ZnCoN-C) had an outstanding electric double layer (EDL) property and conductivity. Therefore, it could significantly reduce the driving voltage of two kinds of CBPE systems, reaching the maximum ECL signal of Ru(bpy)32+. Interestingly, when the ZnCoN-C modified electrode reached the maximum ECL signal, the bare electrode signal was zero. As a proof-of-concept application, a zero-background dual-mode CBPE-ECL biosensor was constructed for the ultrasensitive detection of ochratoxin A (OTA) in beer. Considering that beer samples contained a large number of reducing substances, a reduced CBPE system was selected to build the biosensor. Furthermore, a convenient ECL imaging platform using a smartphone was built for the detection of OTA. This work used a unique EDL material ZnCoN-C to regulate the driving voltage of CBPE for the first time; thus, a novel zero-background ECL sensor was constructed. Further, this work provided a deeper understanding of the CBPE-ECL system and opened a new door for zero-background detection.

Enzyme- and label-free cascade isothermal amplification aptasensor for the ultrasensitive detection of ochratoxin A

BackgroundUltrasensitive detection is crucial for the early warning and intervention of risk factors, ultimately benefiting the environment and human health. Low levels of ochratoxin A (OTA) present a hidden yet significant threat, and rapid detection via high-performing biosensors is therefore essential. ResultsA cascade isothermal amplification aptasensor (CIA-aptasensor) was designed for OTA detection. On the surface of a magnetic bead probe, the OTA level was converted into positively correlated trigger cDNA through its competitive binding with OTA-Apt. The released trigger cDNA activated catalytic hairpin assembly followed by coupling with a hybridization chain reaction to achieve CIA. After adding graphene oxide and SYBR Green I, the background interference was eliminated to specifically obtain OTA-related fluorescence. The ultrasensitive limit of detection was 0.22 pg mL−1, an improvement of 1368-fold over conventional enzyme-linked aptamer sorbent assay by the same OTA-Apt, demonstrating satisfactory reliability and practicability. Thus, the CIA-aptasensor provides an enzyme- and label-free simplified homogeneous system with minimal background interference using isothermal conditions. SignificanceThis study provides a polymerase chain reaction–like approach for enhancing the sensitivity and performance of a biosensor, which could be extended for the application of CIA and label-free signaling strategy to other risk factors.

Ultrasensitive electrochemical sensing for simultaneous rapid detection of zearalenone and ochratoxin A in feedstuffs and foodstuffs

Mycotoxins are causing persistent worries regarding food safety worldwide due to their ability to elicit a wide range of harmful effects in both animals and humans. Approaches that can identify a single mycotoxin are not sufficient for addressing the needs of quality control of agricultural products since they are often co-contaminated by multiple mycotoxins. This paper presents the development of an electrochemical sensor that is free of biomolecules and is capable of simultaneously detecting zearalenone (ZEN) and ochratoxin A (OTA) through the incorporation of nickel oxide (NiO) with carboxylated carbon nanotubes (MWCNT(–COOH)).This is the first time that NiO–MWCNT(–COOH) based electrochemical sensor has achieved the simultaneous potential-resolved selective detection of ZEN and OTA. Under optimized conditions, good linear responses were observed in the range of 0.01–10.24 μg mL−1 for ZEN and 0.04–10.24 μg mL−1 for OTA with low detection limit of 6 and 15 ng mL−1, respectively. The proposed electrochemical sensor demonstrated good selectivity, reusability, reproducibility, and shelf-life for the sensitive detection of both mycotoxins. Moreover, the sensor was made utilizing screen-printing technology to demonstrate its potential for commercialization and practical application. Our biomolecule-free electrochemical sensor was successful in evaluating these mycotoxins in actual samples of corn flour and wheat flour, proving its promising application in monitoring ZEN and OTA co-contamination in agricultural products.

Ultrasensitive strategy for OTA analysis by both recognition-activated multiple isothermal cyclic strand displacement amplification and DNAzyme-mediated cyclic signal reporting mechanism

We propose a recognition-driven ultrasensitive fluorescence sensing strategy for accurate analysis of ochratoxin A (OTA) by taking Mg2+-dependent DNAzyme based catalysis as the final signal output module. Recognition of target OTA destroys the simple double-strand recognition structure and contributes to the liberation of primer probe, which can trigger and activate the primer-mediated multiple isothermal cyclic strand displacement amplification (M-CSDA) process. The designed dual templates (T-P, T-A) can contribute to the generation of enormous nicked products (DNAzyme and primer), which will take effect in the triggering of M-CSDA. Meanwhile, one of the nicked products (DNAzyme) will also take part in the cyclically cleavage of designed hairpin probes (HP) with the presence of the cofactor Mg2+, inducing the recovery of fluorescent signal of quenched hairpin probes. Only the trace amount of target OTA could generate drastic fluorescent signal and ultrasensitive detection of OTA could be well achieved. Under optimized conditions, the detection limit of this method for OTA is 0.59 fg/mL. The characteristics of this method including the simplicity in dual signal amplification design, isothermal operation process and easy fluorescence measurement model exhibit the superior sensitivity and specificity for OTA detection. And this strategy can be further expanded for the design of ultrasensitive aptamer-sensing methods for series analytes.

Mycotoxins in vegetating corn plants from experimental mono-sowing

The aim of present study was to reveal the mycotoxin contamination of vegetative maize (Zea mays L.) plants during the periods of leaf formation and panicle emergence. Early maturing hybrids of the varieties Krasnodarsky 194 MV, Ladozhsky 175 MV and Competence®, resistant to fungal diseases, were grown in the spring-summer period of 2023 on the experimental field of the Russian State Agrarian University – Moscow Agricultural Academy (Moscow) with sod-podzolic soil and the application of NPK fertilizers 16:16:16. For mycotoxicological analysis, aerial parts of plants were collected weekly from the phase of formation of the 3rd leaf (18 days after sowing. Samples of seedlings, leaves and stems (total number – 172), after drying, were ground in a laboratory mill and extracted with a mixture of acetonitrile and water in a volumetric ratio of 84:16 with a consumption of 10 ml per 1 g of sample. Mycotoxin content was determined in extracts after 10-fold dilution with phosphate-salt buffer solution pH 7.5 by indirect competitive enzyme immunoassay. T-2 toxin, deoxynivalenol, diacetoxiscirpenol, roridin A, sterigmatocystin and PR toxin were absent in the samples. Corn seedlings and leaves contained cyclopiazonic acid (CPA), emodin (EMO), mycophenolic acid (MPA), alternariol (AOL), ergot alkaloids (EA), aflatoxin B1 (AB1) and single samples – zearalenone (ZEN), ochratoxin A (OA) and citrinin (CIT) in concentrations from 16 up to 35 μg/kg. Fumonisins of group B are found only in early seedlings. The permanent contaminant of the stems was MPA, whereas EA and CIT were absent. In the seedlings and leaves of all hybrids, the detection of AOL and EA remained stable during the change of development phases, as did the average concentrations of CPA (about 100 μg/kg), AOL (from 17 to 27 μg/kg), EMO (35–58 μg/kg), MPA (28–41 μg/kg), EA (6–18 μg/kg) and AB1 (2 μg/kg). In the stems of plants in phases 7–9 of leaf and sweeping, variation in cases of detection of CPA, EMO, AOL, AB1 and OA was noted by varieties.

A Piezoelectric Nanogenerator-Driven Dual-Mode Platform for Visualization and Impedance Sensing.

Traditional visual biosensing platforms rely on color to display detection results, which can be influenced by individual visual abilities, equipment, parameters, and lighting conditions during photo capture. This limitation significantly impedes the advancement of next-generation portable electrochemical biosensors. Therefore, we propose a visual biosensing device that utilizes distance as an indicator, enabling the facile determination of the length of discoloration, which is inversely proportional to the concentration of the target analyte. The separation of the Signal Generation (SG) and Signal Output (SO) regions effectively mitigates potential interference from the sample color. Additionally, the SG region can be disassembled to facilitate electrochemical impedance spectroscopy (EIS) detection in laboratory settings, enabling dual-mode detection. Meanwhile, the utilization of piezoelectric nanogenerators (PENG) empowers the entire point-of-care testing (POCT) sensing device, effectively addressing the issue of a limited battery life. The biosensing device exhibited a satisfactory linear range (EIS mode, 5 pg/L to 5 mg/L; visual mode, 0.5 ng/L to 5 mg/L) and a low limit of detection (EIS mode, 2.3 pg/L; visual mode, 0.14 ng/L) with S/N = 3 for ochratoxin A (OTA) under optimized conditions. The self-powered and cost-effective dual-mode biosensing platform developed for OTA detection offers clear and easily interpretable results, demonstrating a high accuracy in laboratory settings.

Assembly of stabilized dendritic magnetic ferric-silver nanocomposite with gold nanoparticles for sensitive detection of ochratoxin A using SERS aptasensor

Ochratoxin A (OTA) contamination poses a significant global threat to food security, necessitating the development of rapid and effective detection methods. A dendritic magnetic silver nanocomposite (Fe3O4@SiO2@Ag) tagged with aptamers acted as surface-enhanced Raman scattering (SERS) substrates and capture probes. Further, gold nanoparticles (AuNPs) were functionalized with cDNA and utilized as Raman-enhanced probes (cDNA-AuNPs). The SERS aptasensor which was constructed by the assembly of Apt-Fe3O4@SiO2@Ag and cDNA-AuNPs attained the accuracy quantitative and extremely sensitive detection of OTA. An inverse relationship between the concentration of OTA standard solution and Raman intensity of the characteristic peak at 1080 cm−1 was established in the range of 0.01–5 ng/mL, with an LOD of 0.0074 ng/mL. Furthermore, for positive corn samples, the coincidence rate between the established SERS aptamer sensor and HPLC was in the range of 92.67–121.10%, demonstrating tremendous promise for future practical application through other crops.

A highly efficient homogeneous electrochemiluminescence aptasensor for amplified analysis of Ochratoxin A

Ochratoxin A (OTA) is a toxic thermostable subordinate metabolite produced by Aspergillus and Penicillium species. OTA contamination occurs in a wide range of foods and poses a threat to human health. Therefore, it is crucial to construct a sensitive and reliable method for analyzing OTA to ensure food safety. Herein, a simple yet sensitive ECL aptasensor has been constructed for OTA detection through the synergistic amplification between catalytic DNA assembly (CDA) and exonuclease III (Exo III)-initiated recycling reaction. The anti-OTA aptamer-encoded sensing unit specifically recognizes target OTA and leads to the release of the trigger sequence for stimulating the CDA circuit, yielding numerous dsDNA hybrids that carry the re-assembled S strand. Each of the as-assembled S sequence could hybridize with the Ru(bpy)32+-labeled substrate (S*-Ru) to produce a T-shape structure with a blunt 3′ terminus, which can be hydrolyzed and digested by Exo III, leading to the liberation of mononucleotide functionalized with Ru(bpy)32+ (Ru). Simultaneously, the S sequence was released and hybridized with another S*-Ru sequence for initiating the subsequent cycle of Exo III-stimulated digestion process until all the S*-Ru strands are digested, thus resulting in the generation of numerous Ru and remarkably amplified ECL signals for high-performance detection of OTA. With reliable analyte recognition and high signal gain, the ECL system enabled the high-performance and accurate determination of OTA in buffer, wheat, and wine samples, thus showing considerable potential applications for highly efficient determination of contaminants of low concentration in foodstuff.

Detection of Ochratoxin A and Human Exposure Risk Assessment in Rasa roxburghii by SPE-UHPLC-MS/MS

Detection of Ochratoxin A and Human Exposure Risk Assessment in <em>Rasa roxburghii</em> by SPE-UHPLC-MS/MS

Exonuclease III assisted electrochemical aptasensor simultaneous detection of aflatoxin B1 and ochratoxin a in grains

The synergistic effect of multiple mycotoxins in cereals increases their toxicity. Therefore, the simultaneous detection of multiple mycotoxins in cereals is of great importance. Exonuclease III (Exo III) assisted electrochemical aptasensor has been used for mycotoxin detection, but simultaneous detection of two mycotoxins has not been previously reported. By utilizing Exo III assisted strand displacement, this study developed an electrochemical aptasensor strategy for the simultaneous detection of aflatoxin B1 (AFB1) and ochratoxin A (OTA). This method demonstrates excellent detection of AFB1 and OTA within the range of 0.001–500 ng mL−1, with detection limits as low as 0.229 pg mL−1 for AFB1 and 0.564 pg mL−1 for OTA. The electrochemical aptasensor was successfully applied to analyze grain samples, and the sensor has good specificity, stability and repeatability. The adapter provides simultaneous detection of AFB1 and OTA in food in a fast, simple and highly sensitive platform.

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.

Plasmonic enzyme immunoassay via nanobody-driven controllable aggregation of gold nanoparticles for detection of ochratoxin A in pepper

Ochratoxin A (OTA) in food poses a serious challenge to public health. Herein, using the nanobody-driven controllable aggregation of gold nanoparticles (AuNPs) in a glucose oxidase-tyramine-horseradish peroxidase (GOx-TYR-HRP) system, we propose a direct competitive plasmonic enzyme immunoassay (dc-PEIA) for OTA detection. The OTA-GOx conjugate catalyzes glucose to produce hydrogen peroxide (H2O2), and then HRP catalyzes H2O2 to generate hydroxyl radical which induces the crosslink of TYR. Crosslinked TYR leads to aggregation of AuNPs through strong electrostatic interactions, which is tunable based on the competition of OTA-GOx and free OTA for binding the immobilized nanobody. The optimized dc-PEIA achieves an instrumental limit of detection (LOD) of 0.275 ng/mL and a visual LOD of 1.56 ng/mL. It exhibits good selectivity for OTA and accuracy in the analysis of pepper samples, with the confirmation of high-performance liquid chromatography. Overall, the dc-PEIA is demonstrated as a useful tool for detecting OTA in food.

A G-quadruplex dual-signal strategy for on-site detection of OTA in moldy foods

Ochratoxin A (OTA) is a mycotoxin that is prevalent in contaminated foods and poses a substantial risk. Currently, OTA detection methods rely primarily on single-signal output, rendering them vulnerable to interference. Dual-signal methods can effectively circumvent the aforementioned issues, but the diversity of output signals is limited and needs to be expanded immediately, and there is an extreme lack of on-site detection methods for OTA in crops. In this study, G-quadruplex (G4)-hemin was introduced into a temperature panel to construct a G4 dual-signal (colorimetric and temperature) sensing system, which enables a highly sensitive, on-site, rapid detection of OTA with detection limits of 9.7 nM for colorimetric and 15.7 nM for temperature, respectively. More importantly, this system successfully achieved on-site detection of OTA in moldy corn and wheat. The constructed·G4·dual-signal sensing system own the advantages of simplicity, accuracy, and high sensitivity, demonstrating the great promise in home testing.

A photothermal aptasensor based on rolling circle amplification-enriched DNAzyme for portable detection of ochratoxin A in grape juice

Aptasensors for detection of ochratoxin A (OTA) have been extensively studied, but the majority of them require costly and large-scale equipment as signal readers. Herein, a photothermal aptasensor capable of portable detection of OTA through a thermometer was developed on basis of aptamer structural switching and rolling circle amplification (RCA)-enriched DNAzyme. Oligonucleotides and alkaline phosphatase (ALP) modified magnetic beads were prepared. The binding of aptamers to OTA led to the release of ALP labeled complementary DNA. After magnetic separation, ALP catalyzed the padlock dephosphorylation, inhibiting the subsequent RCA reaction. This process converted the OTA concentration into the amount of the photothermal reagent oxTMB produced from the catalytic reaction induced by RCA-enriched DNAzyme. Under the optimal conditions, the detection limit (LOD) of this aptasensor was 2.28 nM in a clean buffer, while the LOD reached 2.43 nM in 2 % grape juice. The good performance of the photothermal aptasensor makes it possible to measure OTA pollution in low resource environments.