Nature 465, 202–205 (2010)

Nature 465, 206–210 (2010)

DNA is a natural polymer that is frequently employed as a synthetic nanoscale construction element. The molecule has been used to build intricate structures and primitive machines. In particular, bipedal DNA walkers have been created that can walk along one-dimensional tracks. Now, two independent teams of researchers have extended the capabilities of these nanomachines, allowing them to go on autonomous journeys guided only by their surroundings and to pick up cargoes as they move along nanoscale assembly lines.

Milan Stojanovic and colleagues at Columbia University, Arizona State University, the University of Michigan and the California Institute of Technology developed spider-shaped walkers that can travel across a surface. The spiders are composed of an inert protein 'body' and DNA enzyme 'legs' that can cleave a DNA strand from the surface. The surface itself is made from DNA origami — a technique in which a long single strand of DNA is folded into a predetermined shape — and has a track of cleavable DNA strands with base sequences complementary to those of the spider's legs laid out on top of it. The spider seeks out these strands and can thus move along a path programmed into the origami surface.

Nadrian Seeman and colleagues at New York University and Nanjing University have also developed a DNA walker that operates on an origami track. Their walker, however, has single-stranded DNA 'feet' that move along the origami surface with the help of externally supplied strands. Moreover, the walker has 'arms' that can pick up different types of gold nanoparticles from programmable DNA machines positioned along the track.