Issue Date: May 25, 2009
DNA In Another Dimension
USING DNA as a basic chemical building block rather than a genetic molecule, scientists have devised a method for creating complex three-dimensional nanostructures with precisely controlled dimensions that range from 10 to 100 nm (Nature 2009, 459, 414). The strategy of self-assembly could provide a general route for manufacturing sophisticated devices with nanoscale features, the researchers say.
The technique, developed by William M. Shih of Boston's Dana-Farber Cancer Institute and colleagues, is an extension of DNA origami, in which hundreds of short oligonucleotides fasten to a long single strand of DNA in such a way that it folds into a predetermined shape (C&EN, March 20, 2006, page 10). Researchers have already used the technique to create 2-D snowflakes and smiley faces, as well as a 3-D DNA box (C&EN, May 11, page 30). Shih's strategy allows nanotechnologists to build a vast diversity of 3-D DNA structures, a capability his group demonstrated by constructing a tiny railed bridge, a genie bottle, and an icosahedron.
Shih's team designs the structures by computationally "carving" them out of a honeycomb lattice made of a DNA double helix. Using computer-aided design, they arrange a single strand of DNA so that it winds around that carved structure and then determine what short oligonucleotides are required to hold it in place.
"The challenge was actually getting it to work," Shih tells C&EN, because DNA is negatively charged, and repulsive forces tend to keep it from packing into the compact sculptures. "We didn't know what kind of tricks we would need to get it to fold correctly," he says. Ultimately, patience proved to be one of the tricks. Although most 2-D DNA origami structures fold within an hour, Shih's 3-D sculptures take about a week to fold.
"This successful move into three dimensions heralds a new era for the field of structural DNA technology," writes Duke University chemistry professor Thomas H. LaBean in a commentary that accompanies the paper. "Through the ages, some of the most iconic and lasting artifacts of human ingenuity have been sculptures and carvings, created from a wide variety of materials. But until now, a general purpose material from which nanometer-scale, three-dimensional shapes could be made has been lacking."
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