3D DNAzyme walker based electrochemical biosensor for attomolar level microRNA-155 detection

Spatiotemporal control of DNAzyme activity for fluorescent imaging of telomerase RNA in living cells

BACKGROUND

Human telomerase is a ribonucleoprotein complex that includes proteins and human telomerase RNA (hTR). Emerging evidence suggested that the expression level of hTR was high related with the development of tumor, so it is important to accurately detect the content of hTR. Optical control of DNAzyme activity shows a promising strategy for precise biosensing, biomedical imaging and modulation of biological processes. Although DNAzyme-based sensors can be controlled spatiotemporally by light, its application in the detection of hTR in living cells is still rare. Therefore, designing DNAzyme activity spatiotemporal controllable sensors for hTR detection is highly needed.

RESULTS

We developed a UV light-activated DNAzyme-based nanoprobe for spatially accurate imaging of intracellular hTR. The proposed nanoprobe was named MDPH, which composed of an 8-17 DNAzyme (D) inactivated by a protector strand (P), a substrate strand (H), and MnO2 nanosheets. The MnO2 nanosheets can enhance the cellular uptake of DNA strands, so that MDPH probe can enter cells autonomously through endocytosis. Under the high concentration of GSH in cancer cells, MnO2 nanosheets can self-generate cofactors to maintain the catalytic activity of DNAzyme. When exposing UV light and in presence of target hTR, DNAzyme could cleave substrate H, resulting in the recovery of fluorescence of the system. The cells imaging results show that MDPH probe could be spatiotemporally controlled to image endogenous hTR in cancer cells.

SIGNIFICANCE

With this design, telomerase RNA-specific fluorescent imaging was achieved by MDPH probe in both cancer and normal cells. Our probe made a promising new platform for spatiotemporal controllable intracellular hTR monitoring. This current method can be applied to monitor a variety of other biomarkers in living cells and perform medical diagnosis, so it may has broad applications in the field of medicine.

Dual-Signal Imaging Mode Based on Fluorescence and Electrochemiluminescence for Ultrasensitive Visualization of SARS-CoV-2 Spike Protein

Accurate and reliable detection of SARS-CoV-2 is critical for the effective prevention and rapid containment of COVID-19. Current approaches suffer from complex procedures or a single signal readout, resulting in an increased risk of false negatives and low sensitivity. Here, we developed a fluorescence (FL) and electrochemiluminescence (ECL) dual-mode imaging platform based on a self-powered DNAzyme walker to achieve accurate surveillance of SARS-CoV-2 spike protein at the single-molecule level. The specific activation of the DNAzyme walker by the target protein provides the power for the system's continuous running, enabling the simultaneous recording of the reduction in fluorescence spots and the appearance of ECL spots generated by the Ru-doped metal-organic framework (MOF) emitter. Therefore, the constructed imaging platform can achieve dual-mode detection of spike protein via reverse dual-signal feedback, which could effectively eliminate false-positive or false-negative signals and improve the detection accuracy and sensitivity with a low detection limit. In particular, the dual-mode accuracy of spike protein diagnosis in samples has been significantly improved compared to single-signal output means. In addition, this dual-mode imaging platform may become a prospective diagnostic device for other infectious viruses.

Inverting the DNA tetrahedron: A novel strategy for sensitive and stable detection of aging-related enzyme MMP2

In the current study, a novel electrochemiluminescence biosensor based on the entropy-driven DNA tetrahedron for the detection of matrix metalloproteinase 2 (MMP2), an enzyme that regulates extracellular matrix remodeling and affects aging was reported. The biosensor utilizes an inverted DNA tetrahedron structure, which exposes three vertices to the solution, as molecular recognition units for capturing specific biomolecules. The biosensor also employs a ratiometric method and an entropy-driven reaction, which enhance the response rate and sensitivity of the detection. The biosensor can detect MMP2 with a detection limit of 55.2 fM, which is lower than that of conventional sensors. The biosensor also exhibits excellent stability and reproducibility, and can accurately measure MMP2 levels in complex samples, such as human serum. The paper demonstrates the feasibility and effectiveness of using the "inverted" DNA tetrahedron structure and the entropy-driven process to construct interfacial biosensors. The paper also discusses the potential applications of the biosensor in clinical diagnosis and anti-aging research, where MMP2 plays a crucial role in tissue damage and repair. The paper provides a valuable contribution to the field of biosensor development, and opens up new possibilities for using DNA nanotechnology for sensitive and reliable detection of various biomolecules.

Unraveling the Possibilities: Recent Progress in DNA Biosensing

Due to the advantages of its numerous modification sites, predictable structure, high thermal stability, and excellent biocompatibility, DNA is the ideal choice as a key component of biosensors. DNA biosensors offer significant advantages over existing bioanalytical techniques, addressing limitations in sensitivity, selectivity, and limit of detection. Consequently, they have attracted significant attention from researchers worldwide. Here, we exemplify four foundational categories of functional nucleic acids: aptamers, DNAzymes, i-motifs, and G-quadruplexes, from the perspective of the structure-driven functionality in constructing DNA biosensors. Furthermore, we provide a concise overview of the design and detection mechanisms employed in these DNA biosensors. Noteworthy advantages of DNA as a sensor component, including its programmable structure, reaction predictility, exceptional specificity, excellent sensitivity, and thermal stability, are highlighted. These characteristics contribute to the efficacy and reliability of DNA biosensors. Despite their great potential, challenges remain for the successful application of DNA biosensors, spanning storage and detection conditions, as well as associated costs. To overcome these limitations, we propose potential strategies that can be implemented to solve these issues. By offering these insights, we aim to inspire subsequent researchers in related fields.