Caltech scientists use DNA tiles to play tic-tac-toe at the nanoscale

Courtesy Qian Lab/Caltech.

Scientists at Caltech have created the world's smallest game board for playing tic-tac-toe out of DNA strands. What's more, it's possible to swap hundreds of DNA strands in and out at once to reconfigure the nanostructure at will, making it possible in principle to build complicated nanomachines in different custom patterns. The scientists described their work in a December paper in Nature Communications.
Back in 2006, Caltech bioengineer Paul Rothemund figured out how to fold a long strand of DNA into simple shapes, demonstrating this 'DNA origami' technique by producing a smiley face. All you need is a long strand of DNA, plus several shorter strands ('staples'). Combine them in a test tube, and the shorter strands pull various parts of the long strand together so that it folds over into any number of simple shapes. DNA origami was a huge advance for nanotechnology, but to really achieve its full potential, scientists needed to be able to create larger and more complex structures.
Last year, Rothemund's Caltech colleague Lulu Qian introduced a cheap means of getting DNA origami to assemble itself into large arrays. The best part: you could create custom patterns. The array was a bit like a blank canvas, and Qian demonstrated the power of her technique (dubbed 'fractal assembly') by creating the world's smallest version of Leonardo da Vinci's 'Mona Lisa,' visible only with atomic force microscopy.
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