Purification of DNA-origami nanostructures by rate-zonal centrifugation

Most previously reported methods for purifying DNA-origami nanostructures rely on agarose-gel electrophoresis (AGE) for separation. Although AGE is routinely used to yield 0.1-1 mu g purified DNA nanostructures, obtaining >100 mu g of purified DNA-origami structure through AGE is typically laborious because of the post-electrophoresis extraction, desalting and concentration steps. Here, we present a readily scalable purification approach utilizing rate-zonal centrifugation, which provides comparable separation resolution as AGE. The DNA nanostructures remain in aqueous solution throughout the purification process. Therefore, the desired products are easily recovered with consistently high yield (40-80%) and without contaminants such as residual agarose gel or DNA intercalating dyes. Seven distinct three-dimensional DNA-origami constructs were purified at the scale of 0.1-100 mu g (final yield) per centrifuge tube, showing the versatility of this method. Given the commercially available equipment for gradient mixing and fraction collection, this method should be amenable to automation and further scale up for preparation of larger amounts (e.g. milligram quantities) of DNA nanostructures.