DNA can do more than direct how bodies our made — it can also direct
the composition of many kinds of materials, according to a new study from the
U.S. Department of Energy’s
Argonne National Laboratory.
Argonne researcher Byeongdu Lee and his colleagues at Northwestern University
discovered that strands of DNA can act as a kind of nanoscopic "Velcro"
that binds different nanoparticles together. "It’s generally difficult
to precisely control the assembly of these types of nanostructures," Lee
said. "By using DNA, we’re borrowing nature’s power."
Argonne researcher Byeongdu Lee has determined that different shapes of gold nanoparticles, above and below, will self-assemble into different configurations when attached to single strands of DNA.
The "Velcro" effect of the DNA is caused by the molecule’s
"sticky ends," which are regions of unpaired nucleotides — the
building blocks of DNA — that are apt to bond chemically to their base-pair
partners, just like in our genes. When sufficiently similar regions contact
each other, chemical bonds form a rigid lattice. Scientists and engineers believe
these complex nanostructures have the potential to form the basis of new plastics,
electronics and fuels.
In 2008, Lee and his colleagues attached DNA to spherical nanoparticles made
of gold, hoping to control the way the particles arrange themselves into compact,
ordered crystals. This process is called nanoparticle "packing," and
Lee believed that by affixing DNA to the nanoparticles, he could control how
they packed together. "Materials that are packed differently — even
if they are made from the same substance — have been shown to exhibit
dramatically different physical and chemical properties," Lee said.
While the 2008 experiment showed that DNA appeared to control that instance
of nanosphere packing, it was not known whether the effect would occur with
different nanoparticle geometries. The more recent experiment looked at different
shapes of nanoparticles to determine whether their contours affected how they
packed.
According to Lee, the spherical nanoparticles in the earlier experiment tended
to arrange themselves into one of two separate types of cubic crystals: a face-centered
cube (a simple cube with nanospheres at each vertex and additional ones located
in the middle of each face) or a body-centered cube (a simple cube with an additional
nanosphere located in the middle of the cube itself). The type of lattice that
the nanoparticles formed was determined by how the "sticky ends" attached
to the nanoparticles paired together.
In the more recent experiment, the particles' shape did change the material's
final structure, but only insofar as it altered how the DNA "sticky ends"
attached to each other. In fact, the study showed that dodecahedral (12-sided)
nanoparticles arranged into a face-centered cubic configuration while octahedral
(8-sided) nanoparticles formed body-centered cubes — even when the nanoparticles
were attached to identical strands of DNA. "We may be able to make all
different types of nanoparticle packing structures, but the structure that will
result will always be the one that maximizes the amount of binding," he
said.
"The face-centered cubic structure is the most compact way for the nanoparticles
to arrange themselves, while the body-centered cubic is slightly less compact.
The DNA binding is really the true force controlling the construction of the
lattice," he added.
A paper based on the research, "DNA-nanoparticle superlattices formed
from anisotropic building blocks", appeared in the October 3 issue of Nature
Materials.