Strands of DNA have been used to fasten - and then separate - nanoparticles in experiments that could lead to the development of fundamentally "self-constructing" materials.
Christof Niemeyer and colleagues at the University of Dortmund, Germany, used sections of artificially synthesised DNA to attach gold nanoparticles together before separating them again.
DNA consists of two complementary strands that bind together depending on the chemical "bases" on either strand. Attaching nanoparticles by appending them to complementary strands of DNA is a tried and tested technique, already used in some protein sensing systems. But, until now, no one has shown that it is possible to separate the strands again afterwards.
Selectively binding nanoparticles could provide a way to construct complex nanostructures piece by piece, using different DNA strands to add different nanoparticles. These materials could have novel electrical and optical properties that cannot currently be obtained using conventional chemistry.
Being able to separate these materials again would offer even greater flexibility. Niemeyer says it could conceivably be used to modify nanostructures after construction. "It could be used to build [self-constructing] materials," he told New Scientist. "Although that is very far off at the moment."
The team uses artificial DNA, fabricated to have particular bases. Each gold particle - measuring around 15 nanometres (15 billionths of a metre) across - is attached using sulphur to the centre of a DNA strand. The strand extends out on either side.
Two gold particles are then joined together by adding a third strand of DNA that complements half of each gold-bound DNA strand and attaches to both, forming a bridge. This just left the problem of how to separate the gold particles once the bridge was firmly in place.
So Niemeyer's team developed the bridging strand of DNA to have one end longer than the other with the tip of the long end refusing to attach to the gold-bound strands, leaving it loose.
The trick, finally, was to use an additional fourth piece of DNA to bind to this loose end of the bridging strand before "peeling" it away completely - like pulling off a piece of Velcro - leaving the gold particles separated once again.
Chad Mirkin, who pioneered the use of DNA as a nanoscale construction material says the approach is interesting, although the potential applications remain unclear.
"It's a step towards creating a structure where you could have triggerable changes," says Mirkin, now based at Northwestern University in Chicago, US. "But it's not yet clear where these would be useful."
Journal reference: Angewandte Chemie (vol 43, p 6469)
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