Water‐in‐Water Droplets Selectively Uptake Self‐Assembled DNA Nano/Microstructures: a Versatile Method for Purification in DNA Nanotechnology

DNA is an excellent material for constructing self‐assembled nano/microstructures. Owing to the widespread use of DNA as a building block in laboratories and industry, it is desirable to increase the efficiency of all steps involved in producing self‐assembled DNA structures. One of the bottlenecks is the purification required to separate the excess components from the target structures. This paper describes a purification method based on the fractionation by water‐in‐water (W/W) droplets composed of phase‐separated dextran‐rich droplets in a polyethylene glycol (PEG)‐rich continuous phase. The dextran‐rich droplets facilitate the selective uptake of self‐assembled DNA nano/microstructures and allow the separation of the target structure. This study investigates the ability to purify DNA origami, DNA hydrogels, and DNA microtubes. The W/W‐droplet fractionation allows the purification of structures of a broad size spectrum without changes to the protocol. By quantifying the activity of deoxyribozyme‐modified DNA origami after W/W‐droplet purification, this study demonstrates that this method sufficiently preserves the accessibility to the surface of a functional DNA nanostructure. It is considered that the W/W‐droplet fractionation could become one of the standard methods for the purification of self‐assembled DNA nano/microstructures for biomedical and nanotechnology applications owing to its low cost and simplicity.