Fluorescent Sensor Based on Magnetic Separation and Strand Displacement Amplification for the Sensitive Detection of Ochratoxin A

Multi-DNAzymes cascade reaction mediated aptasensors for OTA detection based on the integration of autocatalytic Mg2+-dependent DNAzyme cleavage and entropy-driven circuit

Ochratoxin A (OTA) is a compound of concern due to its potential health effects on humans. Detecting OTA in food is crucial for safeguarding public health. In this study, we fabricated a multi-DNAzyme cascade reaction-mediated colorimetric aptasensors for OTA detection, integrating autocatalytic Mg2+-dependent DNAzyme cleavage (MNAzyme) and an entropy-driven circuit. In brief, the recognition between the aptamer and target OTA led to the release of DNA1. Subsequently, DNA1 hybridized with DNA2, generating an upstream MNAzyme that facilitated the production of a downstream MNAzyme. These MNAzymes possess similar substrate binding arms, enabling them to catalyze the same substrate. The catalytic efficiency of MNAzymes towards the substrates was enhanced due to the increasing concentration of MNAzymes. The cleavage products then triggered an entropy-driven cycle to generate a signal. Under optimal conditions, the sensing system exhibited low detection limits of 48.97 fM for OTA. Additionally, the proposed aptasensor was successfully applied to quantitatively analyze OTA in food samples. Thus, the multi-DNAzyme cascade reaction-mediated colorimetric aptasensors offer an adaptable platform for detecting traces of OTA contaminant in food.

Machine learning driven metal oxide-based portable sensor array for on-site detection and discrimination of mycotoxins in corn sample

Cereals, grains, and feedstuffs are prone to contamination by fungi during various stages from growth to storage. These fungi may produce harmful mycotoxins impacting food quality and safety. Thus, the development of quick and reliable methods for on-site application is crucial for ensuring food safety and quality monitoring. Herein, we have developed an efficient sensor array based on hierarchically modified metal oxides with azodye-based metal complexes for on-site detection and segregation of harmful mycotoxins present in corn samples. The functionalized material has been fully characterized utilizing various sophisticated techniques. The sensor array successfully detected and differentiated five different mycotoxins with 100 % efficiency, validated by linear discriminant analysis (LDA) score plots. The limit of detection, as determined from calibration curves, ranges from 0.02 to 0.09 ppm for the respective mycotoxins. Additionally, the sensor array has also demonstrated 100 % accuracy in discriminating binary and ternary ratios of mycotoxins in real sample analyses.

Establishment of a Dual-Signal Enhanced Fluorescent Aptasensor for Highly Sensitive Detection of Ochratoxin A

A robust and versatile dual-signal enhanced fluorescent aptasensor was developed for ochratoxin A (OTA) detection based on fluorescence resonance energy transfer between 5-carboxyfluorescein (FAM) and Super Green I (SG) fluorophores as the donor and graphene oxide (GO) nanosheet as the acceptor. Abundant SG probes were adsorbed into the FAM-complementary DNA (cDNA)-aptamer double-stranded structure to achieve remarkably enhanced fluorescence responses. Without OTA, the FAM-cDNA-SG conjugates coexisted with GO nanosheets, exhibiting strong fluorescence signals. In the presence of OTA, it was captured by the aptamers to release cDNA-FAM and SG probes, which were adsorbed by GO, leading to OTA-dependent fluorescence quenching. The changed fluorescence intensity was measured for accurate quantitation of OTA. Under optimum conditions, the dual-signal enhanced fluorescent aptasensor realized fascinating sensitivity with a limit of detection of 0.005 ng/mL and a wide concentration range of 0.02-20 ng/mL, as well as high selectivity for OTA over other interfering substances, excellent accuracy with average recoveries of 91.37-116.83% in the fortified malt matrices, and superior reliability and practicability in actual samples. This FAM-cDNA-aptamer-SG/GO nanosheet-based aptasensing platform could be extended to monitor other contaminants or trace molecules in food, environmental, and diagnostic fields by altering the corresponding aptamers.

Magnetic nanoparticle-based immunosensors and aptasensors for mycotoxin detection in foodstuffs: An update

Mycotoxin contamination of food crops is a global challenge due to their unpredictable occurrence and severe adverse health effects on humans. Therefore, it is of great importance to develop effective tools to prevent the accumulation of mycotoxins through the food chain. The use of magnetic nanoparticle (MNP)-assisted biosensors for detecting mycotoxin in complex foodstuffs has garnered great interest due to the significantly enhanced sensitivity and accuracy. Within such a context, this review includes the fundamentals and recent advances (2020-2023) in the area of mycotoxin monitoring in food matrices using MNP-based aptasensors and immunosensors. In this review, we start by providing a comprehensive introduction to the design of immunosensors (natural antibody or nanobody, random or site-oriented immobilization) and aptasensors (techniques for aptamer selection, characterization, and truncation). Meanwhile, special attention is paid to the multifunctionalities of MNPs (recoverable adsorbent, versatile carrier, and signal indicator) in preparing mycotoxin-specific biosensors. Further, the contribution of MNPs to the multiplexing determination of various mycotoxins is summarized. Finally, challenges and future perspectives for the practical applications of MNP-assisted biosensors are also discussed. The progress and updates of MNP-based biosensors shown in this review are expected to offer readers valuable insights about the design of MNP-based tools for the effective detection of mycotoxins in practical applications.

A novel ternary Y-DNA walker amplification strategy designed fluorescence aptasensor based on Au@SiO2@Fe3O4 nanomaterials for ochratoxin A detection

A novel ternary Y-DNA walker amplification strategy designed fluorescence aptasensor based on Au@SiO2@Fe3O4 nanomaterials for ultrasensitive and specific ochratoxin A detection in food samples is presented. Au@SiO2@Fe3O4 nanomaterials provide the loading platform as well as separation and recovery properties for the ternary Y-DNA walker. The ternary Y-DNA walker is designed to be driven by Nb.BbvCI cleaving a large number of FAM probes to achieve signal amplification. Since Ochratoxin A (OTA) can bind to the constituent aptamer in the ternary Y-DNA walker, adding OTA will destroy the structure of the ternary Y-DNA walker, thereby inhibiting the driving process of the walker. After optimization of various parameters, a standard curve was obtained from 100 to 0.05 ng·mL-1 of OTA with the limit of determination of 0.027 ng·mL-1. The spiked recovery of peanut samples by this method was 82.00-93.30%, and the aptasensor showed excellent specificity and long-term stability. This simple, robust, and scalable oligonucleotide chain-based ternary Y-DNA walker can provide a general signal amplification strategy for trace analysis.