Researchers at the Georgia Institute of Technology have discovered an new process for assembling DNA nanostructures in a water-free solvent, which may allow for fabricating more complex nanoscale structures — especially, nanoelectronic chips based on DNA.

Scientists have been using DNA to construct sophisticated new structures from nanoparticles (such as a recent development at Brookhaven National Labs reported by KurzweilAI May 26), but the use of DNA has required a water-based environment. That’s because DNA naturally functions inside the watery environment of living cells. However, the use of water limited the types of structures that are possible.

In addition, the Georgia Tech researchers discovered that, paradoxically, adding a small amount of water to their water-free solvent during the assembly process (and removing it later) increases the assembly rate. It could also allow for even more complex structures, by reducing the problem of DNA becoming trapped in unintended structures by aggregation (clumping).

The new solvent they used is known as glycholine, a mixture of glycerol (used for sweetening and preserving food) and choline chloride, but the researchers are exploring other materials.

The solvent system could improve the combined use of metallic nanoparticles and DNA based materials at room temperature. The solvent’s low volatility could also allow for storage of assembled DNA structures without the concern that a water-based medium would dry out.

The research on water-free solvents grew out of Georgia Tech researchers’ studies in the origins of life. They wondered if the molecules necessary for life, such as the ancestor of DNA, could have developed in a water-free solution. In some cases, they found, the chemistry necessary to make the molecules of life would be much easier without water being present.

Sponsored by the National Science Foundation and NASA, the research will be published as the cover story in Volume 54, Issue 23 of the journal Angewandte Chemie International Edition.

* The assembly rate of DNA nanostructures can be very slow, and depends strongly on temperature. Raising the temperature increases this rate, but temperatures that are too high can cause the DNA structures to fall apart. The solvent system developed at Georgia Tech adds a new level of control over DNA assembly. DNA structures assemble at lower temperatures in this solvent, and adding water can adjust the solvent’s viscosity (resistance to flow), which allows for faster assembly compared to the water-free version of the solvent.

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Abstract of Folding and Imaging of DNA Nanostructures in Anhydrous and Hydrated Deep-Eutectic Solvents

There is great interest in DNA nanotechnology, but its use has been limited to aqueous or substantially hydrated media. The first assembly of a DNA nanostructure in a water-free solvent, namely a low-volatility biocompatible deep-eutectic solvent composed of a 4:1 mixture of glycerol and choline chloride (glycholine), is now described. Glycholine allows for the folding of a two-dimensional DNA origami at 20 °C in six days, whereas in hydrated glycholine, folding is accelerated (≤3 h). Moreover, a three-dimensional DNA origami and a DNA tail system can be folded in hydrated glycholine under isothermal conditions. Glycholine apparently reduces the kinetic traps encountered during folding in aqueous solvent. Furthermore, folded structures can be transferred between aqueous solvent and glycholine. It is anticipated that glycholine and similar solvents will allow for the creation of functional DNA structures of greater complexity by providing a milieu with tunable properties that can be optimized for a range of applications and nanostructures.