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

A novel amplification strategy based on target-induced multicomponent nuclease-mediated catalytic hairpin assembly for fluorescent DNA sensor

Ochratoxin A (OTA) is a highly hazardous mycotoxin widely found in food ingredients and processed products. In response to the demand for food safety, there is an urgent need to establish a highly sensitive, reliable, and cost-effective method for the detection of OTA. In this study, a simple, enzyme-free, sensitive cascade amplification fluorescent strategy was developed to detect OTA based on a magnetic separation system-assisted, multicomponent nuclease (MNAzyme) and its induced catalytic hairpin assembly (CHA). The formation of a stable active MNAzyme was induced by the presence of the target, and the MNAzyme specifically cleaved multiple hairpin H1 to produce sDNA fragments. The sDNA could initiate the mismatched CHA cycle, leading to the production of a large number of H2-H3 complexes, with carboxyfluorescein (FAM) moving away from the quench group (BHQ1), and the fluorescent signal being significantly amplified. The constructed fluorescent aptasensor has a good linear range (0.5-100 ng/mL) and detection limit (0.45 ng/mL). The developed sensor was successfully applied to detect OTA in corn flour and black tea samples.

Ratiometric fluorescent aptasensor based on DNA-gated Fe3O4@Uio-66-NH2 and Exo I-assisted signal amplification

BACKGROUND

Ochratoxin A (OTA) is toxic secondary metabolites produced by fungi and can pose a serious threat to food safety and human health. Due to the high stability and toxicity, OTA contamination in agricultural products is of great concern. Therefore, the development of a highly sensitive and reliable OTA detection method is crucial to ensure food safety. Although fluorescent sensors have been widely used for OTA detection, they still face challenges such as false positives and insufficient sensitivity, thus further improvement of the detection performance is necessary.

RESULTS

Herein, a ratiometric biosensor based on DNA-gated Fe₃O₄@Uio-66-NH₂ nanocomposites and Nucleic Acid Exonuclease I (Exo I)-assisted signal amplification was constructed for the sensitive detection of OTA. This functional nanocomposite combines magnetic, porous and fluorescent properties. Fe₃O₄ of the core enables efficient magnetic separation, while the porous structure of Uio-66-NH₂ encapsulates the fluorescent dye rhodamine 6G (Rho 6G). In addition, a label-free DNA gating strategy was introduced to control the release of Rho 6G. The sensor performs OTA detection by the fluorescence signal ratio of Fe3O4@Uio-66-NH2 and Rho 6G, which effectively avoids false positives of the sensor. Accelerated release of Rho 6G using Exo I greatly improves the sensitivity of the sensor. The sensor has a low LOD (0.308 ng mL-1) and the recoveries for OTA detection in real samples were 92.4%-116.0 %.

SIGNIFICANCE

The development of this ratiometric fluorescent aptasensor highlights its potential for highly sensitive OTA detection, offering significant advantages in selectivity and accuracy due to its unique DNA-gated mechanism and the dual fluorescence signal ratio strategy. Additionally, the use of Fe₃O₄@Uio-66-NH₂ enables effective magnetic separation, while the Exo I-assisted signal amplification enhances sensitivity, making this sensor a powerful tool for detecting OTA in complex sample matrices with high reliability.

A label-free electrochemical sensor based on π-structured bipedal DNA walker-triggered hybridization chain reaction and AuPt NPs/Zr-MOF for OTA detection

BACKGROUND

Ochratoxin A (OTA) is a serious food contaminant, not easily degradable, and capable of causing irreversible damage to the human body. Therefore, it is of great practical significance to establish a sensitive and efficient OTA detection method. The electrochemical aptasensor has a broad development prospect in OTA detection with its advantages of fast response speed and low cost.

RESULTS

Herein, a cascade signal amplification strategy based on AuPt NPs/Zr-MOF and π-structure bipedal DNA walker-triggered hybridization chain reaction (HCR) was designed for the detection of ochratoxin A (OTA). AuPt NPs/Zr-MOF was employed as the electrode modification material, providing a large number of active sites and high conductivity, achieving 1.47 times signal amplification. Interestingly, bipedal DNA walker binds to hairpin 1 (H1) to form the π-structure. Under the activation of Pb2+, one bipedal DNA walker can simultaneously bind and cleave two H1. It exhibits a wide walking range and high recognition efficiency. After H1 is cleaved, the trigger sequence was exposed to trigger HCR and a large amount of methylene blue was loaded on the electrode. Under the optimal conditions, the linear range of the determined OTA is 1 × 10-3-500 ng/mL, and the limit of detection is as low as 0.525 pg/mL.

SIGNIFICANCE

The experimental results demonstrate that the constructed electrochemical aptasensor is a sensitive and efficient platform for OTA monitoring. The applicability in food samples was also confirmed, and the strategy was efficiently selective and reproducible for different analytes. This provides ideas for subsequent food safety testing.

RuSiNPs@N,S-GQDs as self-enhanced anodic electrochemiluminescent immunobeacons for the highly sensitive quantitation of okadaic acid in shellfish

A competitive electrochemiluminescence (ECL) immunosensor is proposed to accurately and rapidly assess okadaic acid (OA) levels in shellfish using a novel self-reinforced solid-state ECL marker, which is essential for ensuring seafood safety. Graphene quantum dots doped with nitrogen and sulfur (N,S-GQDs) were synthesized, for the first time, through the electrolysis of graphite in 3-(N-morpholine) propane sulfonic acid solution. Intriguingly, these N,S-GQDs exhibited exceptional co-reactant properties, significantly enhancing the anodic ECL performance of Ru(bpy)32+ in a phosphate-buffered saline solution. Following the functionalization of Ru(bpy)32+-doped silica nanoparticles (RuSiNPs) with poly(diallyldimethylammonium) chloride, we achieved a well-dispersed assembly of N,S-GQDs on the exterior of the RuSiNPs through electrostatic interactions. Importantly, the core-shell structure of RuSiNPs@N,S-GQDs efficiently encapsulated both the luminophore and co-reactant, thus improving the transfer rates of electrons, shorting interaction distances, and reducing energy loss during light emission. Leveraging this "bright" ECL beacon, the ECL immunosensor demonstrated remarkable analytical performance, yielding a low half maximal inhibitory concentration (IC50) of 0.14 ng mL-1, an extensive linear range spanning 0.003-40 ng mL-1, and impressively low limit of detection of 0.001 ng mL-1 for OA determination.

Simultaneous detection of multiple mycotoxins in agricultural products: Recent advances in optical and electrochemical sensing methods

Mycotoxin contamination poses serious threats to human and animal health. Food and environmental systems are often simultaneously contaminated with multiple mycotoxins, a problem that is further exacerbated by the synergistic toxicological effects of these co-occurring mycotoxins. Consequently, the development of rapid detection methods capable of simultaneously identifying multiple mycotoxins in agricultural products is essential to prevent their entry into the food chain. Compared to standard detection methods, optical and electrochemical (EC) sensing methods have distinct advantages for the rapid detection of mycotoxins. This review comprehensively summarizes the latest advancements in the field of simultaneous detection of multiple mycotoxins using optical and EC sensing methods over the last 6 years (2018-2024). First, the review introduces the classification and relevant principles of optical and EC sensing methods. Thereafter, it emphasizes innovative simultaneous detection strategies within these approaches. Finally, it discusses current challenges and offers a reference for further research. Currently, the main challenge lies in the mutual interference among targets, making the development of an interference-free detection platform essential. Furthermore, the ongoing development of integrated technology is expected to aid regulatory authorities in improving the quality of agricultural products for field applications.

Colorimetric aptasensor utilizing MOF-235 with exceptional peroxidase-like activity for the detection of oxytetracycline residues in raw milk

In this work, a simple, convenient and cost-effective colorimetric aptasensor was successfully constructed for the detection of antibiotic residues in raw milk based on the property that aptamer (Apt) synergistically enhances the catalase-like activity of MOF-235. Under optimised conditions, the proposed colorimetric aptasensor exhibited a wide detection range (15-1500 nM) with a low detection limit (6.92 nM). Furthermore, the proposed aptasensor demonstrated high selectivity, good resistance to interference and storage stability. The proposed aptasensor was validated by spiking recovery in camel milk, cow milk and goat milk with satisfactory recoveries, which demonstrated the great potential of the aptasensor for further application in real food samples, and also suggested that MOF-235 can be used as a potential universal platform to build a sensitive detection platform for other targets.

Integrated Photoelectrochemical-SERS Platform Based on Plasmonic Metal-Semiconductor Heterostructures for Multidimensional Charge Transfer Analysis and Enhanced Patulin Detection

Comprehending the charge transfer mechanism at the semiconductor interfaces is crucial for enhancing the electronic and optical performance of sensing devices. Yet, relying solely on single signal acquisition methods at the interface hinders a comprehensive understanding of the charge transfer under optical excitation. Herein, we present an integrated photoelectrochemical surface-enhanced Raman spectroscopy (PEC-SERS) platform based on quantum dots/metal-organic framework (CdTe/Yb-TCPP) nanocomposites for investigating the charge transfer mechanism under photoexcitation in multiple dimensions. This integrated platform allows simultaneous PEC and SERS measurements with a 532 nm laser. The obtained photocurrent and Raman spectra of the CdTe/Yb-TCPP nanocomposites are simultaneously influenced by variable bias voltages, and the correlation between them enables us to predict the charge transfer pathway. Moreover, we integrate gold nanorods (Au NRs) into the PEC-SERS system by using magnetic separation and DNA biometrics to construct a biosensor for patulin detection. This biosensor demonstrates the voltage-driven ON/OFF switching of PEC and SERS signals, a phenomenon attributed to the plasmon resonance effect of Au NRs at different voltages, thereby influencing charge transfer. The detection of patulin in apples verified the applicability of the biosensor. The study offers an efficient approach to understanding semiconductor-metal interfaces and presents a new avenue for designing high-performance biosensors.

Progress on Electrochemical Biomimetic Nanosensors for the Detection and Monitoring of Mycotoxins and Pesticides

Monitoring agricultural toxins such as mycotoxins is crucial for a healthy society. High concentrations of these toxins lead to the cause of several chronic diseases; therefore, developing analytical systems for detecting/monitoring agricultural toxins is essential. These toxins are found in crops such as vegetables, fruits, food, and beverage products. Currently, screening of these toxins is mostly performed with sophisticated instrumentation such as chromatography and spectroscopy techniques. However, these techniques are very expensive and require extensive maintenance, and their availability is limited to metro cities only. Alternatively, electrochemical biomimetic sensing methodologies have progressed hugely during the last decade due to their unique advantages like point-of-care sensing, miniaturized instrumentations, and mobile/personalized monitoring systems. Specifically, affinity-based sensing strategies including immunosensors, aptasensors, and molecular imprinted polymers offer tremendous sensitivity, selectivity, and stability to the sensing system. The current review discusses the principal mechanisms and the recent developments in affinity-based sensing methodologies for the detection and continuous monitoring of mycotoxins and pesticides. The core discussion has mainly focused on the fabrication protocols, advantages, and disadvantages of affinity-based sensing systems and different exploited electrochemical transduction techniques.

Research progress on the detection of foodborne pathogens based on aptamer recognition

Foodborne diseases caused by bacterial contamination are a serious threat to food safety and human health. The classical plate culture method has the problems of long detection cycle, low sensitivity and specificity, and complicated operation, which cannot meet the growing demand for rapid quantitative detection of pathogenic bacteria. The frequent outbreak of foodborne diseases has put forward higher requirements for rapid and simple detection technology of foodborne pathogens. Aptamer is a kind of oligonucleotide fragment that can recognize targets with the advantages of high affinity and good specificity. The target can be range from proteins, small molecules, cells bacteria, and even viruses. Herein, the latest advances in sensitive and rapid detection of foodborne pathogens based on aptamer recognition was reviewed. Special attention has been paid to the obtained sequences of aptamers to various foodborne pathogens, the optimization of sequences, and the mechanism of aptamer recognition. Then, the research progress of biosensors for the detection of pathogenic bacteria based on aptamer recognition were summarized. Some challenges and prospects for the detection of foodborne pathogens based on aptamer recognition were prospected. In summary, with the further deepening of aptamer research and improvement of detection technology, aptamer-based recognition can meet the needs of rapid, sensitive, and accurate detection in practical applications.

Portable self-powered electrochemical aptasensing platform for ratiometric detection of mycotoxins based on multichannel photofuel cell

Self-powered electrochemical sensors based on photofuel cells have attracted considerable research interest because their unique advantage of not requiring an external electric source, but their application in portable and multiplexed targets assay is limited by the inherent mechanism. In this work, a portable self-powered sensor constructed with multichannel photofuel cells was developed for the ratiometric detection of mycotoxins, namely ochratoxin A (OTA) and patulin (PAT). The spatially resolved CdS/Bi2S3-modified photoanodes and a shared Prussian Blue cathode were integrated on an etched indium-tin oxide slide to fabricate the multichannel photofuel cell. The aptamers of OTA and PAT were covalently bonded to individual photoanode regions to build sensitive interfaces, and the specific recognition of analytes impaired the output performance of constructed PFC. Accordingly, ratiometric sensing of OTA and PAT was achieved by utilizing the output performance of a control PFC as a reference signal. This approach effectively eliminates the impact of light intensity on the accuracy of the detection. Under the optimal conditions, the proposed sensing chip exhibited linear ranges of 2.0-1000 nM and 5.0-500 nM for OTA and PAT, respectively. The detection limits (3 S/N) were determined to be 0.25 nM for OTA and 0.27 nM for PAT. The developed ratiometric sensing method demonstrated good selectivity and stability in the simultaneous detection of OTA and PAT. It was successfully utilized for the analysis of OTA and PAT real samples. This work provides a new perspective for construction of portable and ratiometric self-powered sensing platform.

Fast, portable, selective, and ratiometric determination of ochratoxin A (OTA) by a fluorescent supramolecular sensor

Ochratoxin A (OTA), a mycotoxin found in various food items, possesses significant health risks due to its carcinogenic and toxic properties. Thus, detecting OTA is crucial to ensure food safety. Among the reported analytical methods, there has yet to be one that achieves fast, selective, and portable detection of OTA. In this study, we explore a novel supramolecular sensor, DOCE@ALB, utilizing human serum albumin as the host and a flavonoid fluorescent indicator as the guest. On the basis of indicator displacement assay, this sensor boasts an ultra-fast response time of just 5 s, high sensitivity with a limit of detection at 0.39 ppb, exceptional selectivity, and a noticeable ratiometric fluorescence response to OTA. This discernible color change and portability of the sensor make it suitable for on-site OTA detection in real food samples, including flour, beer, and wine, simply using a smartphone. In comparison to previously reported methods, our approach has showcased notable advantages in both response time and portability, addressing a critical need for food safety and regulatory compliance.