A new strategy based on duplex-specific nuclease and DNA aptamer with modified hairpin structure for various analytes detection

A dual-cycle DNA walker sensor for sensitive clinical detection of microRNAs

BACKGROUND

MicroRNAs (miRNAs) play crucial roles in both physiological and pathological processes, and are increasingly recognized as important biomarkers for cancers and other diseases. However, current detection methods for miRNA face challenges, including inadequate sensitivity and the need for temperature-controlled instruments, which hinder their clinical application. It is a pressing need for new strategies suitable for clinical miRNA detection.

RESULTS

We designed a dual-cycle DNA walker sensor (DDWS) by coupling duplex-specific nucleases enzyme-assisted signal amplification (DSNSA) with a DNA walker sensor. In the DSNSA process, the DSN enzyme specifically hydrolyzes DNA in DNA/target miRNA hybrid duplexes to facilitate the target cycling. The DNA walker sensor is activated by the trigger released from the DSNSA process, enabling a DNA walker cycle via the CHA reaction on magnetic microparticles (MMPs). The DDWS exhibited a strong linear relationship over a range of 600 fM to 600 nM and demonstrated excellent specificity for target miRNA. Furthermore, the DDWS was successfully applied to miRNA detection in real samples, including total RNAs extracted in cell samples and clinical papillary thyroid carcinoma (PTC) tissue samples.

SIGNIFICANCE

This DDWS assay holds great potential for evaluating miRNA expression levels across various biological matrices, contributing to the clinical diagnosis and prognosis of cancers.

Detection of zearalenone by electrochemical aptasensor based on enzyme-assisted target recycling and DNAzyme release strategy

Zearalenone has a high level of detection and exceedance in cereals and by-products. Herein, an electrochemical aptasensor for ZEN detection was proposed. The selected aptamer, which has a high affinity for ZEN, serves as a molecular recognition element and effectively avoids interference from other toxins. Meanwhile, the strategy of exonuclease III-assisted target recycling and DNAzyme-catalysed substrate cleavage was combined. Aptamers and RNA-cleaving DNAzymes, two types of functional nucleic acids, have demonstrated considerable potential as key components of biosensors for the detection of biological targets. Enzyme-assisted signal amplification technology also helps to detect trace levels of ZEN. Under optimal conditions, the proposed aptasensor exhibited remarkable repeatability (RSD: 2.73 %) and superior detection performance over a wide concentration range (100 fg/mL-50 ng/mL), with a detection limit of 89 fg/mL. In actual analysis of cereal samples, the results are comparable to those of liquid chromatography, greatly extending the selectivity of ZEN detection.

Recent Advances in Biological Applications of Aptamer-Based Fluorescent Biosensors

Aptamers have been spotlighted as promising bio-recognition elements because they can be tailored to specific target molecules, bind to targets with a high affinity and specificity, and are easy to chemically synthesize and introduce functional groups to. In particular, fluorescent aptasensors are widely used in biological applications to diagnose diseases as well as prevent diseases by detecting cancer cells, viruses, and various biomarkers including nucleic acids and proteins as well as biotoxins and bacteria from food because they have the advantages of a high sensitivity, selectivity, rapidity, a simple detection process, and a low price. We introduce screening methods for isolating aptamers with q high specificity and summarize the sequences and affinities of the aptamers in a table. This review focuses on aptamer-based fluorescence detection sensors for biological applications, from fluorescent probes to mechanisms of action and signal amplification strategies.

State-of-the-Art Fluorescent Probes: Duplex-Specific Nuclease-Based Strategies for Early Disease Diagnostics

Precision healthcare aims to improve patient health by integrating prevention measures with early disease detection for prompt treatments. For the delivery of preventive healthcare, cutting-edge diagnostics that enable early disease detection must be clinically adopted. Duplex-specific nuclease (DSN) is a useful tool for bioanalysis since it can precisely digest DNA contained in duplexes. DSN is commonly used in biomedical and life science applications, including the construction of cDNA libraries, detection of microRNA, and single-nucleotide polymorphism (SNP) recognition. Herein, following the comprehensive introduction to the field, we highlight the clinical applicability, multi-analyte miRNA, and SNP clinical assays for disease diagnosis through large-cohort studies using DSN-based fluorescent methods. In fluorescent platforms, the signal is produced based on the probe (dyes, TaqMan, or molecular beacon) properties in proportion to the target concentration. We outline the reported fluorescent biosensors for SNP detection in the next section. This review aims to capture current knowledge of the overlapping miRNAs and SNPs' detection that have been widely associated with the pathophysiology of cancer, cardiovascular, neural, and viral diseases. We further highlight the proficiency of DSN-based approaches in complex biological matrices or those constructed on novel nano-architectures. The outlooks on the progress in this field are discussed.

A reagentless electrochemical immunosensor for sensitive detection of carcinoembryonic antigen based on the interface with redox probe-modified electron transfer wires and effectively immobilized antibody

Convenient and sensitive detection of tumors marked in serum samples is of great significance for the early diagnosis of cancers. Facile fabrication of reagentless electrochemical immunosensor with efficient sensing interface and high sensitivity is still a challenge. Herein, an electrochemical immunosensor was easily fabricated based on the easy fabrication of immunoassay interface with electron transfer wires, confined redox probes, and conveniently immobilized antibodies, which can achieve sensitive and reagentless determination of the tumor marker, carcinoembryonic antigen (CEA). Carboxyl multi-walled carbon nanotubes (MWCNTs) were firstly modified with an electrochemical redox probe, methylene blue (MB), which has redox potentials distinguished from those of redox molecules commonly existing in biological samples (for example, ascorbic acid and uric acid). After the as-prepared MB-modified MWCNT (MWCNT-MB) was coated on the supporting glassy carbon electrode (GCE), the MWCNT-MB/GCE exhibited improved active area and electron transfer property. Polydopamine (PDA) was then in situ synthesized through simple self-polymerization of dopamine, which acts as the bio-linker to covalently immobilize the anti-CEA antibody (Ab). The developed immunosensor could be applied for electrochemical detection of CEA based on the decrease in the redox signal of MB after specific binding of CEA and immobilized Ab. The fabricated immunosensor can achieve sensitive determination of CEA ranging from 10 pg/ml to 100 ng/ml with a limit of detection (LOD) of 0.6 pg/ml. Determination of CEA in human serum samples was also realized with high accuracy.