A sensitive electrochemical method for DNA methyltransferase assay and inhibitor screening based on DNA methylation-sensitive cleavage

From bench to bedside: Biosensing strategies to evaluate endocrine disrupting compounds based on epigenetic events and their potential use in medicine

The relationship between endocrine system disorders and health risks due to chemical environmental compounds has become a growing concern in recent years. Involuntary exposure to endocrine disruptors (EDCs) is associated with the worldwide increase of diseases such as cancer, obesity, diabetes, and neurocortical disorders. EDCs are compounds that target the nuclear hormonereceptors (NHR) leading to epigenetic changes. Consequently, the use of biosensing strategies based on epigenetic events have a great potential to provide outstanding information about the exposition of EDCs and their evaluation in human health. This review addresses the novel trends in biosensing EDCs evaluation based on DNA methylation assays associated with different human diseases.

DNA methylation detection: recent developments in bisulfite free electrochemical and optical approaches

DNA methylation is one of the significant epigenetic modifications involved in mammalian development as well as in the initiation and progression of various diseases like cancer. Over the past few decades, an enormous amount of research has been carried out for the quantification of DNA methylation in the mammalian genome. Earlier, most of these methodologies used bisulfite treatment. However, the low conversion, false reading, longer assay time and complex chemical reaction are the common limitations of this method that hinder their application in routine clinical screening. Thus, as an alternative to bisulfite conversion-based DNA methylation detection, numerous bisulfite-free methods have been proposed. In this regard, electrochemical biosensors have gained much attention in recent years for being highly sensitive yet cost-effective, portable, and simple to operate. On the other hand, biosensors with optical readouts enable direct real time detection of biological molecules and are easily adaptable to multiplexing. Incorporation of electrochemical and optical readouts into bisulfite free DNA methylation analysis is paving the way for the translation of this important biomarker into standard patient care. In this review, we provide a critical overview of recent advances in the development of electrochemical and optical readout based bisulfite free DNA methylation assays.

Electrochemical biosensing strategies for DNA methylation analysis

DNA methylation is one of the key epigenetic modifications of DNA that results from the enzymatic addition of a methyl group at the fifth carbon of the cytosine base. It plays a crucial role in cellular development, genomic stability and gene expression. Aberrant DNA methylation is responsible for the pathogenesis of many diseases including cancers. Over the past several decades, many methodologies have been developed to detect DNA methylation. These methodologies range from classical molecular biology and optical approaches, such as bisulfite sequencing, microarrays, quantitative real-time PCR, colorimetry, Raman spectroscopy to the more recent electrochemical approaches. Among these, electrochemical approaches offer sensitive, simple, specific, rapid, and cost-effective analysis of DNA methylation. Additionally, electrochemical methods are highly amenable to miniaturization and possess the potential to be multiplexed. In recent years, several reviews have provided information on the detection strategies of DNA methylation. However, to date, there is no comprehensive evaluation of electrochemical DNA methylation detection strategies. Herein, we address the recent developments of electrochemical DNA methylation detection approaches. Furthermore, we highlight the major technical and biological challenges involved in these strategies and provide suggestions for the future direction of this important field.

A sandwich-hybridization assay for simultaneous determination of HIV and tuberculosis DNA targets based on signal amplification by quantum dots-PowerVision™ polymer coding nanotracers

A novel sandwich-hybridization assay for simultaneous electrochemical detection of multiple DNA targets related to human immune deficiency virus (HIV) and tuberculosis (TB) was developed based on the different quantum dots-PowerVision(TM) polymer nanotracers. The polymer nanotracers were respectively fabricated by immobilizing SH-labeled oligonucleotides (s-HIV or s-TB), which can partially hybrid with virus DNA (HIV or TB), on gold nanoparticles (Au NPs) and then modified with PowerVision(TM) (PV) polymer-encapsulated quantum dots (CdS or PbS) as signal tags. PV is a dendrimer enzyme linked polymer, which can immobilize abundant QDs to amplify the stripping voltammetry signals from the metal ions (Pb or Cd). The capture probes were prepared through the immobilization of SH-labeled oligonucleotides, which can complementary with HIV and TB DNA, on the magnetic Fe3O4@Au (GMPs) beads. After sandwich-hybridization, the polymer nanotracers together with HIV and TB DNA targets were simultaneously introduced onto the surface of GMPs. Then the two encoding metal ions (Cd(2+) and Pb(2+)) were used to differentiate two viruses DNA due to the different subsequent anodic stripping voltammetric peaks at -0.84 V (Cd) and -0.61 V (Pb). Because of the excellent signal amplification of the polymer nanotracers and the great specificity of DNA targets, this assay could detect targets DNA as low as 0.2 femtomolar and exhibited excellent selectivity with the dynamitic range from 0.5 fM to 500 pM. Those results demonstrated that this electrochemical coding assay has great potential in applications for screening more viruses DNA while changing the probes.