A sensitive new nanotechnology assay might represent a “quantum leap” in DNA methylation detection. The technique, which was developed by Vasudev Bailey and co-workers at The Johns Hopkins University School of Medicine, uses quantum dots-fluorescent nanocrystals of a semiconductor material-to selectivel detect and quantify minute amounts of methylated DNA. As in methylation-specific PCR (MSP), sample DNA was treated with sodium bisulfite to convert unmethylated cytosines to uracils while leaving the methylated cytosines unchanged. However, in the new technique bisulfite-treated DNA was amplified by PCR with specific biotin-labeled primers. Next, the researchers added streptavidin-coated quantum dots to the amplified DNA samples. The interaction of biotin-labeled DNA segments with streptavidin-coated quantum dots caused a change in the fluorescence emitted by the nanocrystals, which could be quantified to determine the percentage of methylation of a given DNA sequence.
Because of the high performance of quantum dot fluorophores, the new method is more sensitive and efficient than MSP. As few as eight PCR cycles are required to detect methylated DNA, which reduces the PCR bias that can be observed for MSP. In addition, the “lab-on-a-chip” method minimizes handling and allows simultaneous processing and analysis of multiple samples. The research is being presented at the American Association for Cancer Research’s International Conference on Molecular Diagnostics in Cancer Therapeutic Development, which is being held September 22−25, 2008, in Philadelphia…Check out the details