We report a simple electrochemical method referred to as "eMethylsorb" for the detection of DNA methylation. The method relies on the base dependent affinity interaction of DNA with gold. The methylation status of DNA is quantified by monitoring the electrochemical current as a function of the relative adsorption level of bisulphite treated DNA samples onto a bare gold electrode. This method can successfully distinguish methylated and unmethylated epigenotypes at single CpG resolution.
A new strategy to produce stable barcodes using biological self‐assembly of streptavidin‐ and biotin‐functionalized quantum dots is reported. Such systems are of potential use in multiplexed immunoassay and nucleic acid hybridization assays.
BACKGROUND: DNA methylation is a potential source of disease biomarkers. Typically, methylation levels are measured at individual cytosine/guanine (CpG) sites or over a short region of interest. However, regions of interest often show heterogeneous methylation comprising multiple patterns of methylation (epialleles) on individual DNA strands. Heterogeneous methylation is largely ignored because digital methods are required to deconvolute these usually complex patterns of epialleles. Currently, only singlemolecule approaches, such as next generation sequencing (NGS), can provide detailed epiallele information. Because NGS is not yet feasible for routine practice, we developed a single-molecule-like approach, named for epiallele quantification (EpiQ).
DNA methylation has the potential to be a clinically important biomarker in cancer. This communication reports a real-time and label-free biosensing strategy for DNA methylation detection in cancer cell line. This has been achieved by using surface plasmon resonance biosensing combined with the highly specific molecular inversion probe based amplification method, which requires only 50 ng of bisufite treated genomic DNA.DNA methylation is the process in which a methyl group is added to the carbon-5 position of cytosine in a CpG dinucleotide 1 . Differences in DNA methylation levels between normal and cancer cells have been proposed as biomarkers to retrieve clinically relevant information regarding the stage of disease or cancer subtype, which in turn might help to underpin prognosis and appropriate mode of treatment.2 Much attention has been focused on the detection of DNA methylation using different sensors schemes, 3-9 however the most widely used techniques for DNA methylation are bisulfite sequencing 10 and affinityenrichement. 5 Bisulfite-sequencing is a very sensitive technique capable of retrieving single cytosine methylation information, but the methodology itself is complex and prone to DNA amplification errors. Detecting a series of several CpG sites in a region (e.g., the promoter region) has the potential to extract the desired methylation information without requiring single CpG site resolution. In this context, affinity based methods using methyl binding domain proteins that specifically recognize methylated-CpG rich regions offer a better alternative. While all these methods have excellent analytical performances in detecting regional DNA methylation, they are poorly suited for routine diagnostics due to the high running cost, long assay time, complicated chemistries and detection procedures. Surface Plasmon resonance (SPR) is one of the most powerful alternative analytical methods for circumventing these type of problems, while providing label-free, real-time, reproducible and sensitive biomolecular detection.11 In SPR biosensing, the binding of the target analyte to its surface-bound receptor counterpart produces a local change in refractive index over time at the sensing surface, which is quantitative with the relative mass increase associated with target capture, thus enabling the real-time and label-free readout of these targets
12. This method has previously been used to detect regional DNA methylation using proteins with affinity to CpG rich regions. 6,9 However, the reproducibility of affinity based methods depends on antibody specificity and CG-density. 13 Herein, we report a novel strategy which synergistically couples the label-free, real-time nature of the SPR biosensor with the sensitive, specific and multiplexing capability of the molecular inversion probes (MIPs) for accurate detection of regional DNA methylation. The principle involves utilizing a MIP, which is a single stranded oligonucleotide (ss-oligo) capable of hybridizing to a genomic DNA target by two inverted recognition e...
We show that well-defined three-dimensional nanostructures of functional enzymes can be controllably fabricated by layer-by-layer assembly of avidin and biotinylated horseradish peroxidase on micro-contact printing patterned surface templates.
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