Common Pool Chemical Could Be Key to Building Triple-Helix DNA Nanomaterials

A chemical that protects swimming pool chlorine from sunlight could help create nanomaterials built from DNA. Buda Mendes/Getty Images

Cyanuric acid is one of those many chemicals that you've like never heard of but that do humdrum but useful tasks to make our modern lifestyle possible. In the case of this chemical — also called CYA — its day job is preventing germ-killing chlorine in swimming pools from being destroyed by the sun's ultraviolent rays. All you need to keep your backyard pool safe and healthy is a very small concentration of CYA, no more than 60 to 80 parts per million. You probably don't even realize that you're putting it in the water, since many powdered, tablet and stick chlorine treatments include CYA in the mix.

But now, researchers at Canada's McGill University may have found an exotic, cutting-edge use for CYA, one that suddenly could make it a much more important chemical. In a recent article in the journal Nature Chemistry, the scientists detail how CYA can be used to coax deoxyribonucleic acid, or DNA — the massive molecule that stores genetic information in our cells — into forming a triple helix, a structure that's dramatically different from DNA's usual double helix.

This development could be huge, in an incredibly tiny way. It could enable researchers to create new sorts of DNA assemblies, including ones that incorporate new letters in the genetic alphabet, and create ones with new properties. These DNA nanomaterials could be used to build all sorts of things, from synthetic human tissue to tiny devices for delivering medications inside the body.

Stringing together short DNA strands using the small molecule cyanuric acid (CYA) leads to the formation of a unique rosette motif and a triple helix structure.
Nicole Avakyan

Hanadi Sleiman, a DNA nanoscientist at McGill and senior author of the study, says that the new process could be used with other chemicals that are similar in molecular size to CYA.

"This is the first time that a small molecule has been shown to induce the assembly of DNA strands into a new material by hydrogen-bonding," she says via email. "Using the principle that we introduced in this paper, we can use many other small molecules to induce DNA to form a variety of novel biomaterials."

Steven Maguire, a researcher in Queens University's SNO+ research program who was not involved in the study, explains, "By building custom sections of DNA, researchers can program them to build very small structures, similar to the way DNA is used to build proteins in living cells."

According to Maguire, the process developed by Sleiman's team provides a solution to one of the major problems in the nascent field. "The limitations of current DNA nonomaterials are that they don't branch — it's like trying to build something with Tinkertoys, but only having 180-degree connectors," he says. "Using this new 'star' method lets you build in different directions rather than just in straight lines, and allows researchers to build more and varied structures. This sounds like a pretty major breakthrough in the field."

The new process was eight years in the making. It all started when Sleiman mentioned to other scientists in her lab that CYA might be a good chemical to experiment with, because the molecule has three faces with the same binding features as thymine, the T in the DNA alphabet that also includes adenine, guanine and cytosine (A, G and C, respectively).

"My student Faisal Aldaye tried it at the time, and came back telling me that he had observed very long and abundant fibers by atomic force microscopy," says Sleiman. "However, it took us eight years and the involvement of three PhD students, a post-doc and a collaborator at Queen's University to finally figure out the internal structure of these fibers. It turns out that the fibers are made of triple helices of polyadenines, and each level inside the helix is a hexametric, flower-like rosette of adenine and cyanuric acid units. This is the longest time that it has taken us to publish a paper from the initial discovery."

Another reason CYA is promising for building DNA nanostructures because it is both inexpensive and has low toxicity. Rigoberto Advincula, a professor in the department of macromolecular science and engineering at Case Western Reserve University, also hailed the new process as "a major advancement." He says via email that among other things, the nanofiber structures created by the process can be used to engineer tissue that's more biocompatible with the person who'd receive it in a transplant. 

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