Novel electrochemical biosensor based on Exo III-assisted digestion of dsDNA polymer from hybridization chain reaction in homogeneous solution for CYFRA 21-1 DNA assay

S9.6 Antibody-Mediated Bivalent Capture Biosensor Using Vacuum-Assembled HCR Amplifier for One-Pot, Record-Fast and Ultrasensitive Detection of Nucleic Acid

Electrochemical biosensors utilizing hybridization chain reaction (E-HCR) have witnessed substantial advancement over the past two decades, yet achieving simultaneous rapid and ultrasensitive detection remains a challenge with current strategies. Herein, we report a portable, wireless E-HCR biosensor that leverages S9.6 antibody-mediated bivalent capture for ultrasensitive nucleic acid detection, achieving a record-fast assay completion time. The detection mechanism involves target nucleic acid-triggered opening of a hairpin probe, followed by hybridization with a preassembled HCR/HRP amplifier. The resulting target/hairpin/HCR/HRP complex contains two segments of DNA/RNA heteroduplex, enabling efficient capture by an S9.6 antibody-modified screen-printed carbon electrode (SPCE) through bivalent S9.6 antibody-heteroduplex interactions. The bivalent capture strategy demonstrates a 1.6-fold enhancement over single-site S9.6 antibody-heteroduplex binding and a 3.1-fold improvement in capture efficiency compared to monovalent hybridization. This one-pot strategy offers three unique advantages. First, the integration of bivalent capture, homogeneous hybridization, and preformed HCR/HRP amplifiers enables the heterogeneous E-HCR assay to be completed within 34 min, significantly faster than conventional methods. Second, optimization of HCR amplifier and background signal suppression achieves a high signal-to-noise ratio, facilitating ultrasensitive nucleic acid detection. Third, the biosensor features wireless signal output and utilizes low-cost SPCE, making it suitable for point-of-care applications. Collectively, these unique merits enable the bivalent capture biosensor to achieve portable, one-pot, rapid, and ultrasensitive nucleic acid detection, addressing limitations in current E-HCR biosensing platforms.

Dual Mode Analysis of Methicillin-Resistant Staphylococcus aureus by the CRISPR/Cas12a-Assisted Exonuclease-Mediated Signal Cycle

Methicillin-resistant Staphylococcus aureus (MRSA) is the main Gram-positive bacteria isolated from patients with ocular infections and remians a huge threat to public health. Therefore, sensitive and dual-mode analysis of MRSA is of great significance for evaluating MRSA infection. We depicted a clustered regularly interspaced short palindromic repeats (CRISPR)/Cas12a-based biosensor by integrating the exonuclease III (Exo III)-enhanced fluorescence and colorimetric signals for sensitive and dual-mode analysis of methicillin resistance in MRSA without needing nucleic acid amplification. In this method, Exo III-assisted signal recycling is triggered only when the target mecA gene activates the CRISPR/Cas12a complex, and the HP probes on the surface of magnetic nanoparticles are cleaved by the trans-cleavage activity of Cas12a. Taking the merits of the trans-cleavage activity of the CRISPR/Cas12a system and the Exo III-assisted signal recycling, this approach exhibits an exceptionally elevated detection threshold for the mecA gene. Besides MRSA detection, this accurate and sensitive sensor can be employed to assess additional biomarkers in disease diagnosis by simply changing the crRNA.

Cascade signal amplification strategy for the electrochemical aptasensing of nucleic acid: Combination of dual-output toehold-mediated DNA strand displacement, DNA walker and Exo III

BACKGROUND

Sensitive and selective analysis of low content nucleic acid sequences plays an important role in pathogen analysis, disease diagnosis and biomedicine. The electrochemical biosensor based on toehold-mediated strand displacement reaction (TMSD) is highly attractive in nucleic acid detection due to their improved sensitivity and rapid response. But the traditional TMSD carried out on the electrode always with low displacement efficiency and complicated electrode operation, resulting in compromised sensing performance. There is a great need to construct a novel TMSD based electrochemical detection strategy to overcome such challenges in nucleic acid detecting.

RESULT

Herein, a triple signal amplification electrochemical aptasensor was developed for ultrasensitive detection of CYFRA21-1 DNA. The dual-output toehold mediated strand displacement reaction (dTMSD) can convert one input to two strands output within one strand displacement cycle. So that it possesses a higher efficiency for improving the sensitivity in comparison with the single-output TMSD. And the fuel strand was configured with a tail to realize successive DNA circuits through self-propelling as a DNA walker. All the above processes were carried out on magnetic beads, which is conducive to achieving effective sample purification and minimizing the background signals. Besides, Exonuclease III was further amplified signal. As a result, through the cascade use of above three technologies, the proposed biosensing strategy realized sensitive detection of target DNA with a low detection limit of 0.35 fM (S/N = 3) and wide linear range (0.5 fM-500 pM).

SIGNIFICANCE

The proposed novel dTMSD combining multiple signal amplification strategies for electrochemical detection of CYFRA21-1 DNA with easy operation not only possesses excellent sensitivity and selectivity, but also has potential application value for monitoring DNA in serum. Meanwhile, the development of highly sensitive and specific CYFRA21-1 DNA detection methods is very important for the prevention and treatment of lung cancer.

Substrate-Free Untagged Detection of miR393a Using an Ultrasensitive Electrochemical Biosensor

Rapid and sensitive detection of numerous regulatory pathways in growth and development processes and defensive responses in plant-pathogen interactions caused by miRNA has been the current interest of agricultural scientists. Herein, an uncomplicated ultrasensitive electrochemical biosensor was fabricated to detect miR393a, as its detection is of vital importance for plant diseases. A streptavidin-coated screen-printed carbon electrode (SPCE) was fabricated and characterized by scanning electrochemical microscopy, scanning electron microscopy, surface plasmon resonance, and cyclic voltammetry. The two-dimensional (2D) structure and chemical functionality of the streptavidin-coated SPCE render it a superior platform for loading a modified probe via a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide-N-hydroxysuccinimide linker. This biorecognition platform is capable of efficiently using its excellent conductivity, greater surface area, and effective electrochemical execution due to its synergistic effect between streptavidin and carbon electrodes. The biosensor showed a good linear response (R ² = 0.96) to miR393a concentrations ranging from 100 nM to 100 fM. This streptavidin-based biosensor is highly sensitive to the minimum concentration of miR393a, lowest detection limit, and ultrasensitivity under optimized conditions, i.e., 100 fM, 0.33 fM, and 33.72 μA fM^-1 cm^-2, respectively. In addition, remarkable recoveries could be obtained to confirm the feasibility of this assay in plant disease samples. The fabricated technology could offer a selective, adaptable, and farmer-friendly strategy for the timely detection of miRNA of plant samples.

High-Sensitivity Fluorescence Detection for lung cancer CYFRA21-1 DNA based on Accumulative Hybridization of Quantum Dots

Sensitive detection of circulating tumor DNA (ctDNA) in vitro has attracted growing attention owing to its potential application in diagnostics of cancer. In this study, we synthesized hydrophilic AgInS2@ZnS core-shell...