Toronto Star

Scientists mastering the fine art of DNA origami

Technique for designing tiny, complex structures could be used to deliver drug therapies

- RACHEL FELTMAN THE WASHINGTON POST

Anew technique could make it easier to fold strands of DNA into itty-bitty nano-structures on command.

DNA origami, which sounds like the weirdest hobby ever, is actually a pretty important scientific technique: researcher­s want to be able to produce intricate structures on the nano-scale, so they can interact with human cells and the molecules that make them up. But it’s tough to make anything that small, let alone a highly specialize­d shape designed to, for example, bind to cancer cells and keep them from reproducin­g.

In a study published Wednesday in Nature, researcher­s present a new technique for building these complex structures on the smallest possible scale. One day, these minuscule, intricate objects could be used to deliver drug therapies, along with other applicatio­ns not even dreamed up yet.

And now, designing them is fast and easy, thanks to a centuries-old math problem.

To understand the problem tackled by Bjorn Hogberg of the Karolinska Institute, Sweden, and his colleagues, just look to the Seven Bridges of Konigsberg.

The problem goes like this: Konigsberg (now known as Kaliningra­d, Russia) had seven bridges throughout. Would it be possible, mathematic­ians wondered, to take a walk through the city in which each bridge was crossed once and only once?

“The problem we’re solving is very similar,” Hogberg told the Washington Post.

When scientists try to “3D print” a structure using strands of tiny DNA, they want to optimize the route that DNA takes in order to form the desired structure. Until now, most DNA-based structures have had to be solid and brick-like. But to harness the power of nano-scale objects, you want more dynamic shapes. To create them, you need the DNA to fold itself into a scaffold that maximizes strength and resilience without losing detail by doubling over itself too much.

“We wanted to put the DNA strand on every edge of the polygonal shape once — and if possible only once — and then bring it back to its starting point, since it’s a circular molecule,” Hogberg explained.

With his team’s new algorithm — developed with help from computer scientists at Aalto University in Finland — it’s as easy as rendering a complex shape using normal 3D printing software. The algorithm is able to optimize a DNA strand’s path to form that shape.

For the user, Hogberg said, it’s suddenly as simple to create 3D nanostruct­ures as it is to make large-scale ones. Until it comes time to print them out, anyway.

“The learning curve is really improved here. It’s really easy to design them now,” he said.

“But creating them hasn’t really changed. To actually get them printed out, you have to order the DNA and pipette it together, and that’s of course the barrier to entry for most people.”

So DIY bio-hackers will probably have to wait awhile before the team’s innovation lets them do complex DNA origami at home. For now, the group is publishing the code for the algorithm in the hopes of helping other labs produce these complex structures more quickly and efficientl­y.

 ?? ERIK BENSON AND BJORN HOGBERG ?? The shape of a rabbit is seamlessly converted into a folded DNA strand using a technique developed by Swedish researcher­s.
ERIK BENSON AND BJORN HOGBERG The shape of a rabbit is seamlessly converted into a folded DNA strand using a technique developed by Swedish researcher­s.

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