DNA Density-dependent Uptake of DNA Origami-based Two-or Three-dimensional Nanostructures by Immune Cells

DNA nanostructures are potential candidates for targeted drug delivery to immune cells. Whether their structural properties are suitable for targeted delivery is, however, incompletely elucidated. Here, we focused on DNA density that may be important for the recognition and uptake of DNA nanostructures by immune cells. We designed DNA nanostructures with almost identical molecular weight and structural flexibility but different shape and density using DNA origami technology. We compared five types of DNA nanostructures all of which comprised 10 DNA helices with an identical circular, single-stranded scaffold and staples. Rec180 was a rectangular almost flat structure, while Rec90, Rec50, and Rec0 were forms of Rec180 bent at the center by 90°, 50°, and 0°, respectively. Rec50/50 had two bents of 50° each. The fluctuation or flexibility of these DNA nanostructures in solution was estimated using the CanDo software. The DNA density estimated from the average distance between any two of the 10 DNA helices in DNA nanostructures was different; Rec50, Rec0, and Rec50/50 had higher density than Rec180 and Rec90 did. Agarose gel electrophoresis and atomic force microscopy showed that all the nanostructures were produced at a high yield. Flow cytometry analysis revealed that the uptake of high-density DNA nanostructures by murine macrophage-like RAW264.7 cells was higher than that of low-density DNA. A positive correlation was observed between DNA density and cellular uptake. Thus, DNA nanostructures with high-density DNA are suitable delivery vehicles to immune cells.