ZNA probe immobilized single-use electrodes for impedimetric detection of nucleic acid hybridization related to single nucleotide mutation

A bulged-type enzyme-free recognition strategy designed for single nucleotide polymorphisms integrating with label-free electrochemical biosensor

Compared to conventional nucleic acid detection methods, label-free single nucleotide polymorphism (SNP) detection presents challenging due to the necessity of discerning single base mismatches, especially in the field of enzyme-free detection. In this study, we introduce a novel bulged-type DNA duplex probe designed to significantly amplify single-base differences. This probe is integrated with programmable DNA-based nanostructures to develop a sensitive, label-free biosensor for nonenzymatic SNP detection. The duplex probe with one bulge could selectively identify wild-typed DNA (WT) and mutant-type DNA (MT) based on a competitive strand displacement reaction mechanism. The hyperbranched HCR (HHCR) by incorporating of hairpin DNA into the DNA tetrahedron and surface-tethering on the portable screen printing electrode (SPCE) significantly favor the formation of negatively charged DNA nanostructure. We harnessed strong repulsion of DNA nanostructure towards the electroactive [Fe(CN)₆]³⁻/⁴⁻ in combination with electrochemical technique to create a label-free biosensor. This simple, enzyme-free and label-free biosensor could detect MT with a detection limit of 56 aM, even in multiple sequence backgrounds. The study served as the proof-of-concept for the integration of enzyme-free competitive mechanism and label-free strategy, which can be extended as a powerful tool to various fields.

Recent Progress on Optical Biosensors Developed for Nucleic Acid Detection Related to Infectious Viral Diseases

Optical biosensors have many advantages over traditional analytical methods. They enable the identification of several biological and chemical compounds directly, instantly, and without the need of labels. Their benefits include excellent specificity, sensitivity, compact size, and low cost. In this review, the main focus is placed on the nucleic acid-based optical biosensor technologies, including colorimetric, fluorescence, surface plasmon resonance (SPR), Evanescent-Wave Optical, Fiber optic and bioluminescent optical fibre. The fundamentals of each type of biosensor are briefly explained, and particular emphasis has been placed on the achievements which have been gained in the last decade on the field of diagnosis of infectious viral diseases. Concluding remarks concerning the perspectives of further developments are discussed.

Zip Nucleic Acid-Based Genomagnetic Assay for Electrochemical Detection of microRNA-34a

Zip nucleic acid (ZNA)-based genomagnetic assay was developed herein for the electrochemical detection of microRNA-34a (miR-34a), which is related to neurological disorders and cancer. The hybridization between the ZNA probe and miR-34a target was performed in the solution phase; then, the resultant hybrids were immobilized onto the surface of magnetic beads (MBs). After magnetic separation, the hybrids were separated from the surface of MBs and then immobilized on the surface of pencil graphite electrodes (PGEs). In the case of a full-match hybridization, the guanine oxidation signal was measured via the differential pulse voltammetry (DPV) technique. All the experimental parameters that influenced the hybridization efficiency (i.e., hybridization strategy, probe concentration, hybridization temperature, etc.) were optimized. The cross-selectivity of the genomagnetic assay was tested against two different miRNAs, miR-155 and miR-181b, individually as well as in mixture samples. To show the applicability of the ZNA-based genomagnetic assay for miR-34a detection in real samples, a batch of experiments was carried out in this study by using the total RNA samples isolated from the human hepatocellular carcinoma cell line (HUH-7).

Printed Electrochemical Biosensors: Opportunities and Metrological Challenges

Printed electrochemical biosensors have recently gained increasing relevance in fields ranging from basic research to home-based point-of-care. Thus, they represent a unique opportunity to enable low-cost, fast, non-invasive and/or continuous monitoring of cells and biomolecules, exploiting their electrical properties. Printing technologies represent powerful tools to combine simpler and more customizable fabrication of biosensors with high resolution, miniaturization and integration with more complex microfluidic and electronics systems. The metrological aspects of those biosensors, such as sensitivity, repeatability and stability, represent very challenging aspects that are required for the assessment of the sensor itself. This review provides an overview of the opportunities of printed electrochemical biosensors in terms of transducing principles, metrological characteristics and the enlargement of the application field. A critical discussion on metrological challenges is then provided, deepening our understanding of the most promising trends in order to overcome them: printed nanostructures to improve the limit of detection, sensitivity and repeatability; printing strategies to improve organic biosensor integration in biological environments; emerging printing methods for non-conventional substrates; microfluidic dispensing to improve repeatability. Finally, an up-to-date analysis of the most recent examples of printed electrochemical biosensors for the main classes of target analytes (live cells, nucleic acids, proteins, metabolites and electrolytes) is reported.

Impedimetric Sensing of Factor V Leiden Mutation by Zip Nucleic Acid Probe and Electrochemical Array

A carbon nanofiber enriched 8-channel screen-printed electrochemical array was used for the impedimetric detection of SNP related to Factor V Leiden (FV Leiden) mutation, which is the most common inherited form of thrombophilia. FV Leiden mutation sensing was carried out in three steps: solution-phase nucleic acid hybridization between zip nucleic acid probe (Z-probe) and mutant type DNA target, followed by the immobilization of the hybrid on the working electrode area of array, and measurement by electrochemical impedance spectroscopy (EIS). The selectivity of the assay was tested against mutation-free DNA sequences and synthetic polymerase chain reaction (PCR) samples. The developed biosensor was a trustful assay for FV Leiden mutation diagnosis, which can effectively discriminate wild type and mutant type even in PCR samples.

Electrochemical Detection of Solution Phase Hybridization Related to Single Nucleotide Mutation by Carbon Nanofibers Enriched Electrodes

In the present study, a sensitive and selective impedimetric detection of solution-phase nucleic acid hybridization related to Factor V Leiden (FV Leiden) mutation was performed by carbon nanofibers (CNF) modified screen printed electrodes (SPE). The microscopic and electrochemical characterization of CNF-SPEs was explored in comparison to the unmodified electrodes. Since the FV Leiden mutation is a widespread inherited risk factor predisposing to venous thromboembolism, this study herein aimed to perform the impedimetric detection of FV Leiden mutation by a zip nucleic acid (ZNA) probe-based assay in combination with CNF-SPEs. The selectivity of the assay was then examined against the mutation-free DNA sequences as well as the synthetic PCR samples.