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DNA strands fluoresce in these microscope images
from Ohio State University . Researchers here have invented a
process for uncoiling DNA strands and forming them into precise
patterns – a prelude to biologically based electronics and medical
devices. The squares in the lower right image measure
approximately 10 micrometers (millionths of a meter) across.
Image courtesy of Ohio State University.
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Other labs have formed very simple structures
with DNA, and those are now used in devices for gene testing and
medical diagnostics. But Lee and Guan are the first to coax strands of
DNA into structures that are at once so orderly and so complex that
they resemble stitches on a quilt.
"These are very narrow, very long wires that can be
designed into patterns for molecular electronics or biosensors," Lee
said. "And in our case, we want to try to build tools for gene
delivery, DNA recombination, and maybe even gene repair, down the road."
The longest strands are one millimeter (thousandths
of a meter) long, and only one nanometer (billionths of a meter) thick.
On a larger scale, positioning such a long, skinny tendril of DNA is
like wielding a human hair that is ten meters (30 feet) long. Yet Lee
and Guan are able to arrange their DNA strands with nanometer
precision, using relatively simple equipment.
In this patent-pending technology, the researchers
press the comb into a drop of water containing coils of DNA molecules.
Some of the DNA strands fall between the comb's teeth, so that the
strands uncoil and stretch out along the surface of the comb as it is
pulled from the water.
They then place the comb on a glass chip surface.
Depending on how they place the comb, they leave behind strands of
different lengths and shapes.
"Basically, we're doing nanotechnology using only a
piece of rubber and a tiny droplet of DNA solution," Guan said.
Computer chips that bridge the gap between the
electronic and the biological could make detection of certain
chemicals easier, and speed disease diagnosis. But first, researchers
must develop technologies to mass produce DNA circuits as they produce
chip circuits today.
The technique that Lee and Guan used is similar to
a relatively inexpensive chip-making technology called soft
lithography, where rubber molds press materials into shape.
In this study, they arranged the DNA into rows of "stitches,"
pinstripes and criss-cross shapes.
The pinstripes presented the researchers with a
mystery: for some reason, thorn-like structures emerged along the
strands at regular intervals.
"We think the 'thorns' may be used as interconnects
between nanowires, or they could connect the nanowires with other
electronic components," Guan said. "We are not trying to eliminate
them, because we do not think they are defects. We also believe their
formation is controllable, because they are almost completely absent
in some experiments but abundant in others. Although we currently do
not know exactly how the thorns form, maybe new and useful
nanostructures may be created if we can better understand and control
this process."
The university will license the technology for
further development. Lee and Guan are working on their first
application – building the wires into sensors for detecting disease
biomarkers. In the meantime, they are collaborating with researchers
in the Department of Electrical and Computer Engineering at Ohio State
to measure the electrical properties of the DNA wires. They are also
using this technique to produce DNA-based nanoparticles for gene
delivery. |
