Label-Free Detection of Zeptomol miRNA via Peptide Nucleic Acid Hybridization Using Novel Cyclic Voltammetry Method

PNA-Pdx: Versatile Peptide Nucleic Acid-Based Detection of Nucleic Acids and SNPs

Monitoring diseases caused by pathogens or by mutations in DNA sequences requires accurate, rapid, and sensitive tools to detect specific nucleic acid sequences. Here, we describe a new peptide nucleic acid (PNA)-based nucleic acid detection toolkit, termed PNA-powered diagnostics (PNA-Pdx). PNA-Pdx employs PNA probes that bind specifically to a target and are then detected in lateral flow assays. This can precisely detect a specific pathogen or genotype genomic sequence. PNA probes can also be designed to invade double-stranded DNAs (dsDNAs) to produce single-stranded DNAs for precise CRISPR-Cas12b-based detection of genomic SNPs without requiring the protospacer-adjacent motif (PAM), as Cas12b requires PAM sequences only for dsDNA targets. PNA-Pdx identified target nucleic acid sequences at concentrations as low as 2 copies/μL and precisely detected the SARS-CoV-2 genome in clinical samples in 40 min. Furthermore, the specific dsDNA invasion by the PNA coupled with CRISPR-Cas12b precisely detected genomic SNPs without PAM restriction. Overall, PNA-Pdx provides a novel toolkit for nucleic acid and SNP detection as well as highlights the benefits of engineering PNA probes for detecting nucleic acids.

An electrochemical biosensor based on ARGET ATRP with DSN-assisted target recycling for sensitive detection of tobacco mosaic virus RNA

Herein, an electrochemical biosensor for detecting tobacco mosaic virus (TMV) RNA is constructed by activator regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) combined with duplex-specific nuclease (DSN)-assisted target recycling. First, the captured DNA (cDNA) is self-assembled on the electrode surface and hybridizes with the TMV RNA (tRNA) to form cDNA/tRNA hybrids. And then the initiator of ARGET ATRP (α-bromoisobutyric acid, BMP) is attached to the cDNA via an amide bond and later triggers ARGET ATRP. Many electroactive monomers (ferrocenylmethyl methacrylate, FMMA) are polymerized and a remarkable electrical signal response of ferrocene (Fc) is obtained. However, with the present of DSN, DSN cleaves the cDNA/tRNA hybrid and releases tRNA to hybridize with another cDNA, thereby causing significant shortening of the length of the cDNA. The number of polymer chains on the electrode surface is drastically reduced, which is followed by a noticeable reduction in the signal of Fc. The method shows high sensitivity, superior selectivity, excellent stability and good reproducibility under optimal conditions with the limit of detection (LOD) of 2.9 fM. Furthermore, the biosensor showed satisfactory applicability in detecting tRNA in real samples, thereby demonstrating the potential of the method for practical TMV RNA detection.

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.