Issue 23, 2014

eMethylsorb: rapid quantification of DNA methylation in cancer cells on screen-printed gold electrodes

Abstract

Simple, sensitive and inexpensive regional DNA methylation detection methodologies are imperative for routine patient diagnostics. Herein, we describe eMethylsorb, an electrochemical assay for quantitative detection of regional DNA methylation on a single-use and cost-effective screen-printed gold electrode (SPE-Au) platform. The eMethylsorb approach is based on the inherent differential adsorption affinity of DNA bases to gold (i.e. adenine > cytosine ≥ guanine > thymine). Through bisulfite modification and asymmetric PCR of DNA, methylated and unmethylated DNA in the sample becomes guanine-enriched and adenine-enriched respectively. Under optimized conditions, adenine-enriched unmethylated DNA (higher affinity to gold) adsorbs more onto the SPE-Au surface than methylated DNA. Higher DNA adsorption causes stronger coulombic repulsion and hinders reduction of ferricyanide [Fe(CN)6]3−ions on the SPE-Au surface to give a lower electrochemical response. Hence, the response level is directly proportional to the methylation level in the sample. The applicability of this methodology was tested by detecting the regional methylation status in a cluster of eight CpG sites within the engrailed (EN1) gene promoter of the MCF7 breast cancer cell line. A 10% methylation level sensitivity with good reproducibility (RSD = 5.8%, n = 3) was achieved rapidly in 10 min. Furthermore, eMethylsorb also has advantages over current methylation assays such as being inexpensive, rapid and does not require any electrode surface modification. We thus believe that the eMethylsorb assay could potentially be a rapid and accurate diagnostic assay for point-of-care DNA methylation analysis.

Graphical abstract: eMethylsorb: rapid quantification of DNA methylation in cancer cells on screen-printed gold electrodes

Article information

Article type
Paper
Submitted
05 Sep 2014
Accepted
09 Oct 2014
First published
09 Oct 2014

Analyst, 2014,139, 6178-6184

Author version available

eMethylsorb: rapid quantification of DNA methylation in cancer cells on screen-printed gold electrodes

K. M. Koo, A. A. Ibn Sina, L. G. Carrascosa, M. J. A. Shiddiky and M. Trau, Analyst, 2014, 139, 6178 DOI: 10.1039/C4AN01641F

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