B. Wei et al. / Wyss Institute, Harvard

This atomic-force microscopy shows 100 shapes, each created from tiles of DNA strands. Each shape takes up a space measuring 150 by 150 nanometers, or roughly one-thousandth the width of a human hair.

By Alan Boyle

The DNA molecule serves as the code of life, but it also serves as handy building material for nanoscale structures and newly published research shows how patterns as complex as letters, numbers and smiley faces can be created far more cheaply and quickly than previously thought.

Harvard researchers demonstrate the latest twists in this week's issue of the journal Nature. The process involves laying out short segmentsof DNA in a tile-shaped pattern determined by custom-designed chemical bonds. Those single-stranded tiles, in turn, can assemble themselves into larger shapes like Lego blocks, depending on how the bonds attach to one another. Different recipes for mixing the tiles together will produce different shapes.

The researchers Bryan Wei, Mingjie Dai and Peng Yinestimate that the process yielded the desired structure 12 to 17 percent of the time. That yield is far from perfect, but it could be perfectly acceptable for a process involving thousands upon thousands of self-assembling molecules.

The technique updates a construction strategy that was first pioneered in the 1980s. Back then, it took two years to create a 7-nanometer-wide cube from 10 strands of DNA, Caltech's Paul Rothemund and Aarhus University's Ebbe Sloth Andersen observed in a Nature commentary on the research. In contrast, the newly reported results suggest that far more complex shapes, measuring more than 100 nanometers across, could be churned out at an average rate of one per hour. (A human hair is roughly 100,000 nanometers wide.)

Another attractive factor has to do with the cost: An alternate method for creating nanoscale shapes, known as DNA origami, twists one long molecular strand into a desired shape rather than using lots of smaller tiles. But for each different shape, a new set of molecular "staples" has to be synthesized at a cost of roughly $1,000, according to the Nature commentary. The Harvard researchers' method involves creating a $7,000 set of tiles that could theoretically produce 2 X 10^93 shapes. That's a 2 followed by 93 zeros.

In their Nature paper, Wei and his colleagues showed off 100 shapes including the Roman alphabet, numerical digits, punctuation marks, the peace sign, Chinese characters and 10 kinds of emoticons. They made use of a custom-designed computer program to aid in the design of the shapes and control the liquid-handling robot that mixed the DNA ingredients.

"This advance truly brings DNA nanotechnology into the rapid-prototyping age, and enables DNA shapes to be tailored for every experiment," Rothemund and Andersen wrote in their commentary.

Link:
DNA designs done faster, cheaper