Folding of single-stranded circular DNA into rigid rectangular DNA accelerates its cellular uptake

Despite the importance of the interaction between DNA and cells for its biological activity, little is known about exactly how DNA interacts with cells. To elucidate the relationship between the structural properties of DNA and its cellular uptake, a single-stranded circular DNA of 1801 bases was designed and folded into a series of rectangular DNA (RecDNA) nanostructures with different rigidities using DNA origami technology. Interactions between these structures and cells were evaluated using mouse macrophage-like RAW264.7 cells. RecDNA with 50 staple DNAs, including four that were Alexa Fluor 488-labeled, was designed. RecDNA with fewer staples, down to four staples (all Alexa Fluor 488-labeled), was also prepared. Electrophoresis and atomic force microscopy showed that all DNA nanostructures were successfully obtained with a sufficiently high yield. Flow cytometry analysis showed that folding of the single-stranded circular DNA into RecDNA significantly increased its cellular uptake. In addition, there was a positive correlation between uptake and the number of staples. These results indicate that highly folded DNA nanostructures interact more efficiently with RAW264.7 cells than loosely folded structures do. Based on these results, it was concluded that the interaction of DNA with cells can be controlled by folding using DNA origami technology.