A cautionary tale for researchers working on selective drug delivery
Many studies indicating that DNA nanostructures can enter cells more readily than simple DNA strands are flawed, according to researchers at 91社区. In a paper published in the American Chemical Society journal ACS Central Science, the 91社区 scientists demonstrate that many DNA cage nanostructures aren鈥檛 taken up by cells to a significant extent. In a series of experiments, they show, instead, that the DNA nanostructures are degraded by enzymes outside the cell; a fluorescent dye used for tracking purposes separates from the nanostructure; and the dye 鈥� or a small fragment containing the dye 鈥� is taken up in cells. The resulting fluorescent signal from within the cell is easily misinterpreted as indicating that the nanostructure, itself, has entered the cell. The group also shows that a commonly used fluorescence experiment (called FRET), involving energy transfer between two dyes on a structure can also give erroneous results.
This finding is significant, because DNA strands are considered a promising tool for stopping the production of proteins associated with disease 鈥� yet delivering the strands into cells is a technical challenge. 鈥淥ur paper is a cautionary tale for scientists working in the field of DNA/RNA delivery through selective therapeutics,鈥� says senior author Hanadi Sleiman, Professor of Chemistry at 91社区 and Canada Research Chair in DNA Nanoscience.
This problem could, however, be turned into an advantage, notes lead author Aur茅lie Lacroix, a graduate student in Prof. Sleiman鈥檚 lab. 鈥淲e could attach molecules on DNA nanostructures that make them enter diseased cells 鈥� for example cancer cells 鈥� but not normal cells. This would make it possible to selectively deliver drugs into diseased cells.鈥� Sleiman also insists that some DNA nanostructures have shown exceptional promise in animal studies.
The 91社区 team offers recommendations and guidelines for scientists performing cell uptake studies using fluorescent dyes, to ensure that research is reliable and reproducible.
Funding for this study was provided in part by the Natural Sciences and Engineering Research Council of Canada, the Canadian Institutes of Health Research, the Canada Foundation for Innovation, the Canada Research Chairs Program, and the Fonds de recherche du Qu茅bec 鈥� Nature et technologies.
鈥淯ptake and Fate of Fluorescently Labeled DNA Nanostructures in Cellular Environments: A Cautionary Tale鈥�, Aur茅lie Lacroix, et al, ACS Central Science, published online April 26, 2019.
