Target-swiped DNA lock for electrochemical sensing of miRNAs based on DNAzyme-assisted primer-generation amplification

Detection of fucosylated extracellular vesicles miR-4732-5p related to diagnosis of early lung adenocarcinoma by the electrochemical biosensor

Our preliminary investigation has identified the potential of serum fucosylated extracellular vesicles (EVs) miR-4732-5p in the early diagnosis of lung adenocarcinoma (LUAD) by a fucose-captured strategy utilizing lentil lectin (LCA)-magnetic beads and subsequent screening of high throughput sequencing and validation of real-time quantitative polymerase chain reaction (RT-qPCR). Considering the relatively complicated procedure, expensive equipment, and stringent laboratory condition, we have constructed an electrochemical biosensor assay for the detection of miR-4732-5p. miR-4732-5p is extremely low in serum, down to the fM level, so it needs to be detected by highly sensitive electrochemical methods based on the Mg2+-dependent DNAzyme splitting nucleic acid lock (NAL) cycle and hybridization chain reaction (HCR) signal amplification. In this study, signal amplification is achieved through the dual amplification reactions using NAL cycle in combination with HCR. In addition, hybridized DNA strands bind to a large number of methylene blue (MB) molecules to enhance signaling. Based on the above strategy, we further enhance our signal amplification strategies to improve detection sensitivity and accuracy. The implementation of this assay proceeded as follows: initially, miR-4732-5p was combined with NAL, and then Mg2+-dependent DNAzyme splitted NAL to release auxiliary DNA (S1) strands, which were subsequently captured by the immobilized capture probe DNA (C1) strands on the electrode surface. Following this, abundant quantities of DNA1 (H1) and DNA2 (H2) tandems were generated by HCR, and S1 strands then hybridized with the H1 and H2 tandems through base complementary pairing. Finally, MB was bonded to the H1 and H2 tandems through π-π stacking interaction, leading to the generation of a signal current upon the detection of a potential capable of inducing a redox change of MB by the electrode. Furthermore, we evaluated the performance of our developed electrochemical biosensor assay. The results demonstrated that our assay is a reliable approach, characterized by its high sensitivity (with a detection limit of 2.6 × 10-17 M), excellent specificity, good accuracy, reproducibility, and stability. Additionally, it is cost-effective, requires simple operation, and is portable, making it suitable for the detection of serum fucosylated extracellular vesicles miR-4732-5p. Ultimately, this development has the potential to enhance the diagnostic efficiency for patients with early-stage LUAD.

Signal Amplification-Based Biosensors and Application in RNA Tumor Markers

Tumor markers are important substances for assessing cancer development. In recent years, RNA tumor markers have attracted significant attention, and studies have shown that their abnormal expression of post-transcriptional regulatory genes is associated with tumor progression. Therefore, RNA tumor markers are considered as potential targets in clinical diagnosis and prognosis. Many studies show that biosensors have good application prospects in the field of medical diagnosis. The application of biosensors in RNA tumor markers is developing rapidly. These sensors have the advantages of high sensitivity, excellent selectivity, and convenience. However, the detection abundance of RNA tumor markers is low. In order to improve the detection sensitivity, researchers have developed a variety of signal amplification strategies to enhance the detection signal. In this review, after a brief introduction of the sensing principles and designs of different biosensing platforms, we will summarize the latest research progress of electrochemical, photoelectrochemical, and fluorescent biosensors based on signal amplification strategies for detecting RNA tumor markers. This review provides a high sensitivity and good selectivity sensing platform for early-stage cancer research. It provides a new idea for the development of accurate, sensitive, and convenient biological analysis in the future, which can be used for the early diagnosis and monitoring of cancer and contribute to the reduction in the mortality rate.

Enzyme-Free Autocatalysis-Driven Feedback DNA Circuits for Amplified Aptasensing of Living Cells

Aptasensors with high specificity have emerged as powerful tools for understanding various biological processes, thus providing tremendous opportunities for clinical diagnosis and prognosis. However, their applications in intracellular molecular imaging are largely impeded due to the low anti-interference capacity in biological environments and the moderate sensitivity to targets. Herein, a robust enzyme-free autocatalysis-driven feedback DNA circuit is devised for amplified aptasensing, for example, adenosine triphosphate (ATP) and thrombin, with a significantly improved sensitivity in living cells. This initiator-replicated hybridization chain reaction (ID-HCR) circuit was acquired by integrating the HCR circuit with the DNAzyme biocatalysis. Also, the autocatalysis-driven aptasensor consists of a recognition element and an amplification element. The recognition unit can specifically identify ATP or thrombin via a versatile conformational transformation, resulting in the exposure of the initiator to the autocatalysis-driven circuit. The ID-HCR element integrates the charming self-assembly characteristics of the HCR and the remarkable catalytic cleavage capacity of DNAzyme for realizing the continuously self-sustained regeneration or replication of trigger strands and for achieving an exponential signal gain. The autocatalysis-driven aptasensor has been validated for quantitative analysis of ATP and thrombin in vitro and for monitoring the corresponding aptamer substrates with various expressions in live cells. More importantly, the autocatalysis-driven aptasensor, as a versatile amplification strategy, holds enormous potential for analysis of other less abundant biomarkers by changing only the recognition element of the system.