Application of intercalating molecules in detection of methylated DNA in the presence of silver ions.

Silver ions can influence DNA structure. The extent of this structural perturbation is different in methylated and non-methylated DNA. Here, we explored the interaction of eight convenient DNA interacting molecules with methylated and non-methylated short GC rich oligonucleotides in the presence and absence of silver ions. Acridine orange, DAPI, Doxorubicin, Ethidium bromide, Hoechst 33342, Methylene blue, PicoGreen, and Propidium iodide are tested for their ability to distinguish methylated and non-methylated DNA. Among them, Ethidium bromide, Methylene blue, and PicoGreen were able to discriminate between methylated and non-methylated DNA, while DAPI and Hoechst 33342 were only able to discriminate with the aid of silver ions. A detection method is proposed using Ethidium bromide in which the silver-treated sample of DNA exposed different fluorescence intensity from the untreated one on the base of its methylation state. This phenomenon was sequence-dependent and could provide a sensing platform with a detection limit of about 40 nM.