Going for the gold Researchers have created a dnA spider that can do a simple task—
pick up and carry a gold nanoparticle. To do this, the spider’s arm binds to a dnA “leash” on a
nanoparticle, detaches it from the station and ferries the cargo away (top). Atomic force micro
scopy (bottom) shows three separate nanoparticles (purple) as they are collected by the spider.
arms binds to this DNA leash, grabbing
the nanoparticle and plucking it off the
origami. As the spider moves away from
that station, it carries the new cargo
along to the next stop, where it will pick
up another nanoparticle.
Seeman compares the spider to a car
chassis moving along an assembly line.
Components are added to the spider
“like you would add a door, a steering
wheel or an engine to a chassis,” says
Seeman, whose spider work also appears
in the May 13 issue of Nature.
After two more stops, the spider might
have up to three particles in its arms.
But there may also be just one or two.
That’s because the stations can be programmed to either give up or keep their
cargo. Using the same track, the spider
may pick up different combinations of
In the future, Seeman says, a single
assembly line may be able to work with
many more than three building blocks.
Such longer assembly lines could build
more complex objects. He also plans
to make these spiders autonomous so
they can do the work without the scientists having to add new DNA strands for
Finally, he wants to try to assemble
molecules that will bind together into
complexes, rather than make things that
ultimately have to be held together by
the DNA. He thinks spiders could pick
up individual molecules at each station
that would bind to each other. By bringing together molecules one at a time,
spiders could fit together molecular
puzzle pieces that don’t react well
together in nature. This could be a help
to chemists, he says.
“What we do right now in virtually all
chemistry is throw in a bunch of things
in the pot, and swirl them around so
they collide with one another,” Seeman
says. “In principle we could do reactions
Crawling into the future
Researchers concede that DNA spiders
can’t do anything useful yet, and most
scientists are reluctant to project too
far into the future about what these
nanorobots could eventually do.
“It’s very appealing to be able to picture
something that’s a billion times smaller
than a human that can move,” says
Caltech biological engineer Niles Pierce,
who has done work on DNA walkers. “But
to take that locomotion and put it to pro-
ductive use for fabrication of nanoscale
components, that’s still a futuristic goal.”
Yet engineers should continue to
experiment with these nanomachines
to pave the way for novel discoveries
in nanorobotics, Pierce says. “The stuff
you would learn along the way pays
dividends in other areas.”
And the hope remains that decades
down the road, swarms of DNA spiders
might be deployed in people’s bodies
searching for telltale signs of cancer or
disease. Those spiders would signal to
each other where to find the troubled
tissue and work together to dive-bomb
their targets with sacs of medicine. Such
targeted antidisease missiles could avoid
the side effects that occur when drugs
pervade the body and affect other tissues.
s Lloyd Smith. “Molecular robots on
the move.” Nature. May 13, 2010.
s For more information, visit the Centre
for dnA nanotechnology website at
September 11, 2010 | science news | 21