by Pam Frost Gorder
Columbus OH (SPX)
December 18, 2005
Ohio State University researchers have invented a process for
uncoiling long strands of DNA and forming them into precise
Ultimately, these DNA strands could act
as wires in biologically based electronics and medical devices, said
L. James Lee, professor of chemical and biomolecular
engineering at Ohio State University.
In the early online edition of the Proceedings of the National
Academy of Sciences, Lee and postdoctoral researcher Jingjiao
Guan describe how they used a tiny rubber comb to pull DNA
strands from drops of water and stamp them onto glass chips.
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
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
"We think the 'thorns' may be used
as interconnects between nano-wires, or they could connect the
nano-wires 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 nano-particles for gene delivery.