DNA Building Blocks

New pyramidal structures made out of DNA could be the basis of complex molecular devices.

For years, some researchers have suggested that DNA could be used to create complex self-assembling structures and even nanoscale machines. Indeed, simple shapes, such as cubes, and simple devices, such as tweezers, made of DNA have already been created. But skeptics have questioned whether DNA has the stability needed for more sophisticated devices.

Now researchers from The University of Oxford have developed rigid building blocks out of DNA that can be designed to self-assemble into more complex structures. These blocks, which are shaped like pyramids, have already demonstrated their usefulness by enabling the first measurements of the amount of force that DNA can support without buckling, according to the researchers.

Andrew Turberfield, professor of physics at Oxford, and a researcher involved in the work, says it is "one of the very few examples of the use of a DNA nanostructure to allow you to actually do something that you couldn't do before. It doesn't just look pretty, it's actually useful."

The new measurements show that DNA is "a relatively strong material," says Chris Dwyer, electrical and computer engineering professor at Duke University, who also works on DNA self-assembly. "This solidifies the argument that we'll be able to use DNA self-assembly for more complex structures."

DNA is an attractive material for self-assembled devices because its sequence of bases, which in the body serve as the genetic code, can be “programmed.” By tweaking this code, researchers are able to direct how strands will combine when added to a solution.

In the work at Oxford, four strands of DNA served as the basis for the pyramids. Each strand makes up one triangular face. The edges of these triangles have open puzzle-piece sequences that bind to another edge of a triangle. As these edges meet, the triangles fold into the shape of a pyramid. Simply by mixing the right numbers of different strands together, the researchers have built trillions of pyramids -- and in just seconds.

These simple structures may prove to be useful as containers, perhaps for drug delivery in the body. But they are also rigid structures that could be a starting point for many other, more complex structures. To get these building blocks to assemble into more complex structures, the Oxford researchers again turned to DNA. They incorporated loose strands into the structures with sequences designed to link to loose strands in neighboring pyramids.