DNA-Based Nanobiosensors as an Emerging Platform for Detection of Disease

A comprehensive review on nano-molybdenum disulfide/DNA interfaces as emerging biosensing platforms

The development of nucleic acid-based portable platforms for the real-time analysis of diseases has attracted considerable scientific and commercial interest. Recently, 2D layered molybdenum sulfide (2D MoS₂ from here on) nanosheets have shown great potential for the development of next-generation platforms for efficient signal transduction. Through combination with DNA as a biorecognition medium, MoS₂ nanostructures have opened new opportunities to design and construct highly sensitive, specific, and commercially viable sensing devices. The use of specific short ssDNA sequences like aptamers has been proven to bind well with the unique transduction properties of 2D MoS₂ nanosheets to realize aptasensing devices. Such sensors can be operated on the principles of fluorescence, electro-cheumuluminescence, and electrochemistry with many advantageous features (e.g., robust biointerfacing through various conjugation chemistries, facile sensor assembly, high stability with regard to temperature/pH, and high affinity to target). This review encompasses the state of the art information on various design tactics and working principles of MoS₂/DNA sensor technology which is emerging as one of the most sought-after and valuable fields with the advent of nucleic acid inspired devices. To help achieve a new milestone in biosensing applications, great potential of this emerging technique is described further with regard to sensitivity, specificity, operational convenience, and versatility.

Tandem blocking of PCR extension to form a single-stranded overhang for facile, visual, and ultrasensitive gene detection

In order to detect a predetermined gene in a field test, a facile, visual, and ultrasensitive approach without the need of special and expensive machines is required. In this study, a gene in the Ebola virus was targeted as an example for diagnosis. The key strategy is to incorporate molecular blockers (azobenzene-bearing moieties or thymine dimers) in tandem in one of the PCR primers and stop the polymerase extension there to form a single-stranded overhang. The PCR product was added to the dispersion of gold nanoparticles which were labelled with a probe oligonucleotide. When the Ebola virus-specific gene existed in the specimen, the oligonucleotide on the gold particles formed a double-helix with the single-stranded overhang, and thus the dispersion remained red in color. In the absence of the gene, however, the dispersion rapidly turned to blue because of nanoparticle aggregation. The difference was explicit even when the initial specimen involved only 1 copy of the gene. Accordingly, “whether the patient is infected by the virus or not” can be easily and visually judged by the naked eye.

Here we present a simple but practically useful assay for gene detection. This strategy employs the advantages of both PCR and Au colloidal science, and thus satisfactorily fulfills the factors required for Point-of-Care detection.

Synthesis and Characterization of Polyaniline/Graphene Composite Nanofiber and Its Application as an Electrochemical DNA Biosensor for the Detection of Mycobacterium tuberculosis

This article describes chemically modified polyaniline and graphene (PANI/GP) composite nanofibers prepared by self-assembly process using oxidative polymerization of aniline monomer and graphene in the presence of a solution containing poly(methyl vinyl ether-alt-maleic acid) (PMVEA). Characterization of the composite nanofibers was carried out by Fourier transform infrared (FTIR) and Raman spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). SEM images revealed the size of the PANI nanofibers ranged from 90 to 360 nm in diameter and was greatly influenced by the proportion of PMVEA and graphene. The composite nanofibers with an immobilized DNA probe were used for the detection of Mycobacterium tuberculosis by using an electrochemical technique. A photochemical indicator, methylene blue (MB) was used to monitor the hybridization of target DNA by using differential pulse voltammetry (DPV) method. The detection range of DNA biosensor was obtained from of 10⁻⁶–10⁻⁹ M with the detection limit of 7.853 × 10⁻⁷ M under optimum conditions. The results show that the composite nanofibers have a great potential in a range of applications for DNA sensors.

Blocking probe as a potential tool for detection of single nucleotide DNA mutations: design and performance

Developing strategies to detect single nucleotide DNA mutations associated with treatment decisions in cancer patients from liquid biopsies is a rapidly emerging area of personalized medicine that requires high specificity. Here we report how to design an easy enzyme-free approach that could create a platform for detection of L858R mutation of EGFR that is a predictive biomarker of tyrosine kinase treatment in many cancers. This approach includes the addition of blocking probes with the antisense ssDNA at different blocking positions and different concentrations such as to avoid re-annealing with the respective sense ssDNA. The successful blocking strategy was corroborated by fluorescence spectroscopy in solution using two distinct FRET pairs and quartz crystal microbalance with dissipation (QCM-D) measurements under comparable experimental conditions, as the hybridization rate-limiting step in both methods is the nucleation process. The efficiency of hybridization of each blocking probe was strongly dependent on its position particularly when the analyte possesses a secondary hairpin-structure. We tested the performance of blocking probes in combination with gold nanoparticles; the obtained results were in agreement with those of QCM-D. These findings could facilitate the development of better biosensors, especially those using probes containing secondary structure.

Prevention of Child Sexual Abuse by Targeting Pre-Offenders Before First Offense

The population of potential child abuse offenders has largely been unstudied. In the current study, we examine whether a six-component model used for primary diabetes prevention could be adapted to child sexual abuse pre-offenders, whereby individuals who are prone to sexual abuse but have not yet committed an offense can be prevented from committing a first offense. The six components include: define and track the magnitude of the problem, delineate a well-established risk factor profile so that at-risk persons can be identified, define valid screening tests to correctly rule in those with the disease and rule out those without disease, test effectiveness of interventions-the Dunkelfeld Project is an example, produce and disseminate reliable outcome data so that widespread application can be justified, and establish a system for continuous improvement. By using the diabetes primary prevention model as a model, the number of victims of child sexual abuse might be diminished.

Biomedical Applications of DNA-Conjugated Gold Nanoparticles

Gold nanoparticles (AuNPs) are useful for diagnostic and biomedical applications, mainly because of their ease in preparation and conjugation, biocompatibility, and size-dependent optical properties. However, bare AuNPs do not possess specificity for targets. AuNPs conjugated with DNA aptamers offer specificity for various analytes, such as proteins and small molecules/ions. Although DNA aptamers themselves have therapeutic and target-recognizing properties, they are susceptible to degradation in vivo. When DNA aptamers are conjugated to AuNPs, their stability and cell uptake efficiency both increase, making aptamer-AuNPs suitable for biomedical applications. Additionally, drugs can be efficiently conjugated with DNA aptamer-AuNPs to further enhance their therapeutic efficiency. This review focuses on the applications of DNA aptamer-based AuNPs in several biomedical areas, including anticoagulation, anticancer, antibacterial, and antiviral applications.

A QCM-based ‘on–off’ mechanistic study of gas adsorption by plasmid DNA and DNA–[Bmim][PF6] construct

The study of the adsorption behavior of disease markers such as ammonia (NH₃) and acetaldehyde (CH₃CHO) with biomaterials has been presented to enable the development of self-diagnosis technologies, among others.