A novel approach for the detection of DNA using immobilized peptide nucleic acid (PNA) probes and signal enhancement by real-time immuno-polymerase chain reaction (RT-iPCR)

A double methylene blue labeled single-stranded DNA and hairpin DNA coupling biosensor for the detection of Fusarium oxysporum f. sp. cubense race 4

The DCL gene in Fusarium oxysporum f. sp. cubense Race 4 (Foc4) is a pivotal pathogenic factor causing banana fusarium wilt. Precise DCL detection is crucial for Foc4 containment. Here, we present a novel ssDNA-hDNA coupling electrochemical biosensor for highly specific DCL detection. The sensing interface was formed via electrodeposition of a composite containing reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) onto a carbon screen-printed electrode (SPE), followed by thiol-modified ssDNA functionalization. Additionally, the incorporation of hDNA, with methylene blue (MB) at both ends, binds to ssDNA through base complementarity, forming an ssDNA-hDNA coupling probe with bismethylene blue. This sensing strategy relies on DCL recognition by the hDNA probe, leading to DNA hairpin unfolding and detachment of hDNA bearing two MBs from ssDNA, generating a robust "on-off" signal. Empirical results demonstrate the sensor's amplified electrical signals, reduced background currents, and an extended detection range (6.02 × 106-3.01 × 1010 copies/μL) with a limit of detection (3.01 × 106 copies/μL) for DCL identification. We applied this sensor to analyze soil, banana leaves, and fruit samples, confirming its high specificity and stability. Moreover, post-sample detection, the sensor exhibits reusability, offering a cost-effective and rapid approach for banana wilt detection.

Application strategies of peptide nucleic acids toward electrochemical nucleic acid sensors

Peptide nucleic acids (PNAs) have attracted tremendous interest in the fabrication of highly sensitive electrochemical nucleic acid biosensors due to their higher stability and increased sensitivity than common DNA probes. The neutral pseudopeptide backbone of PNAs not only makes the PNA/DNA duplexes more stable but also provides many opportunities to construct ultrasensitive nucleic acid sensors. This review presents the details of various protocols for the construction of PNA-based electrochemical nucleic acid sensors. The crucial factors, origin, and development of PNA, immobilization methods of PNA probes and signal generation mechanisms, are discussed. This review aims to provide a reference for ultrasensitive PNA electrochemical biosensor preparation.

A highly sensitive detection for foot-and-mouth disease virus by gold nanopariticle improved immuno-PCR

BACKGROUND

Foot-and-mouth disease (FMD) is one of the most contagious of all artiodactyl animal diseases, and its infection has an obvious ability to spread over long distances and to contribute to epidemics in FMD-free areas. A highly sensitive and specific method is required to detect FMDV. In this study, we evaluated the usefulness of a bio-barcode assay (BCA) technique for detecting clinical samples of FMDV.

METHODS

Highly sensitive gold nanopariticle (GNP) improved immuno -PCR (GNP-IPCR) which derived from the bio-barcode assay (BCA) was designed for the detection of FMDV. The target viral particles were captured by a polyclonal antibody coated on ELISA microplate, followed by adding GNP which was dually modified with oligonucleotides and a FMDV specific monoclonal antibody (MAb) 1D11 to form a sandwiched immune complex. After the formation of immuno-complex, the signal DNA was released by heating, and consequently characterized by PCR and real time PCR.

RESULTS

The detection limit of GNP-PCR could reach to 10 fg/ml purified FMDV particles, and the assay can detect clinical samples of FMDV with highly sensitivity, while detect limit of conventional ELISA is 100 ng/ml in this study.

CONCLUSION

GNP-IPCR may provide a highly sensitive method for the detection of FMDV.

Food analysis and food authentication by peptide nucleic acid (PNA)-based technologies

This tutorial review will address the issue of DNA determination in food by using Peptide Nucleic Acid (PNA) probes with different technological platforms, with a particular emphasis on the applications devoted to food authentication. After an introduction aimed at describing PNAs structure, binding properties and their use as genetic probes, the review will then focus specifically on the use of PNAs in the field of food analysis. In particular, the following issues will be considered: detection of genetically modified organisms (GMOs), of hidden allergens, of microbial pathogens and determination of ingredient authenticity. Finally, the future perspectives for the use of PNAs in food analysis will be briefly discussed according to the most recent developments.

Polycation/DNA complexes coated with oligonucleotides for gene delivery

Ternary nanoparticles with negatively charged surface were prepared by coating single-stranded oligonucleotides (5'-C(10)A(20)-3') on histidine-conjugated polyallylamine (PAA-HIS)/DNA complexes for gene delivery. Characterization of PAA-HIS/DNA/oligonucleotide complexes demonstrated that nanoparticles possessed the negative surface charge -27 mV and size of around 100 nm when the molar ratio of oligonucleotide/PAA-HIS exceeded 1.5. The negatively charged oligonucleotide-coated PAA-HIS/DNA complexes could be entirely internalized by the living HeLa cells to exhibit high gene expression with low cytotoxicity and the resistance against erythrocyte agglutination and serum inhibition. Since the gene expression of PAA-HIS/DNA complexes was significantly inhibited by coating other polyanions and oligonucleotides, the ternary PAA-HIS/DNA/deoxyadenosine-rich oligonucleotide complexes were uptaken by specific receptor-mediated process. Additionally, the deposition of a layer of oligonucleotides onto the binary PAA-HIS/DNA complexes could effectively transfect various types of cells including HEK-293, HepG2 and Hs68 cells, indicating the technology of coating specific oligonucleotides on PAA-HIS/DNA complexes or other cationic binary DNA complexes might facilitate the use of nanoparticles for safe and efficient gene delivery and eventual therapy.

Nanomaterial-assisted signal enhancement of hybridization for DNA biosensors: a review

Detection of DNA sequences has received broad attention due to its potential applications in a variety of fields. As sensitivity of DNA biosensors is determined by signal variation of hybridization events, the signal enhancement is of great significance for improving the sensitivity in DNA detection, which still remains a great challenge. Nanomaterials, which possess some unique chemical and physical properties caused by nanoscale effects, provide a new opportunity for developing novel nanomaterial-based signal-enhancers for DNA biosensors. In this review, recent progress concerning this field, including some newly-developed signal enhancement approaches using quantum-dots, carbon nanotubes and their composites reported by our group and other researchers are comprehensively summarized. Reports on signal enhancement of DNA biosensors by non-nanomaterials, such as enzymes and polymer reagents, are also reviewed for comparison. Furthermore, the prospects for developing DNA biosensors using nanomaterials as signal-enhancers in future are also indicated.