ABSTRACT
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.
Subject(s)
Nanostructures , Water , DNA/chemistry , Dextrans , Nanostructures/chemistry , Nanotechnology/methods , Water/chemistryABSTRACT
We report a photolithographic method for the shape control of DNA hydrogels based on photo-activated self-assembly of Y-shaped DNA nanostructures (Y-motifs). To date, various methods to control the shape of DNA hydrogels have been developed to enhance the functions of the DNA hydrogel system. However, photolithographic production of shape-controlled DNA hydrogels formed through the self-assembly of DNA nanostructures without the use of radical polymerizations has never been demonstrated, although such a method is expected to be applied for the shape-control of DNA hydrogels encapsulating sensitive biomolecules, such as proteins. In this study, we used a photo-activated linker to initiate the self-assembly of Y-motifs, where the cross-linker DNA was at first inactive but was activated after UV light irradiation, resulting in the formation of shape-controlled DNA hydrogels only at the UV-exposed area produced by photomasks. We believe that this method will be applied for the construction of biohybrid machines, such as molecular robots and artificial cells that contain intelligent biomolecular devices, such as molecular sensors and computers.
ABSTRACT
This study examined the effects of surfactants on the motion and positioning of microparticles in an inhomogeneous electric field. The microparticles were suspended in oil with a surfactant and the electric field was generated using sawtooth-patterned electrodes. The microparticles were trapped, oscillating, or attached to the electrodes. The proportion of microparticles in each state was defined by the concentration of surfactant and the voltage applied to the electrodes. Based on the trajectory of the microparticles in the electric field, we developed a new physical model in which the surfactant adsorbed on the microparticles allowed the microparticles to be charged by contact with the electrodes, with either positive or negative charges, while the non-adsorbed surfactant micellizing in the oil contributed to charge relaxation. A simulation based on this model showed that the charging and charge relaxation, as modulated by the surfactant concentration, can explain the trajectories and proportion of the trapped, oscillating, and attached microparticles. These results will be useful for the development of novel self-assembly and transport technologies and colloids sensitive to electricity.
