UI
Researchers Turn DNA into Lead Detector
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Too much lead in the body can
lead to brain damage potentially severe enough to cause mental retardation
in children, whose neurological systems are developing and hence more vulnerable.
The health risk has made detecting lead in our environment a national
concern.
And University of Illinois researchers have developed what could
prove to be a simple, fast, inexpensive method of on-site lead detection,
using a DNA-based sensor designed to glow like a microscopic lightning
bug in the presence of even tiny amounts of the metal.
The process also could be modified to sense other toxic
metals, such as mercury. That metal became a particular concern in Illinois
this year when Nicor Inc. began investigating mercury contamination in
dozens of homes in the Chicago area, caused by the company's old gas regulators.
In their lab work, published in the Oct. 25 issue of the
Journal of the American Chemical Society, UI chemistry Professor Yi Lu
and graduate student Jing Li were able to detect lead at levels about 50
times below the amount considered dangerous.
"This DNA is very selective for lead," Lu said.
"The process of finding it (evidence of lead) costs a
lot less, the time and the effort," he added.
Eventually, Lu hopes to see portable lead detection devices
employed using the process, which is being patented. He's already working
with researchers in the UI College of Engineering on hardware designs.
Lu said such a device could be feasible in as little as
five to 10 years.
Others, such as Anthony Czarnik, a bio-sensing specialist
and editor of the Journal of Combinatorial Chemistry, also see the research
leading to a marketable device.
"I think this work could serve as the basis for real-world
(lead) sensors," Czarnik said in the most recent issue of Chemical &
Engineering News.
The basic problem with overexposure to lead is the neurological
damage it causes, especially in young children. Even when it's not severe
enough to lead to retardation, it can contribute to hyperactivity, learning
disabilities and hearing problems, said Ron Brown, acting chief of the
state Health Department's Division of Health Assessment Screening.
People who are "lead compromised" also may suffer headaches,
bone pain and organ damage, said Garry Bird of the Champaign-Urbana Public
Health District, who has two decades of lead investigation experience.
Bird and Brown said the most common source of lead exposure
remains lead-based paint in older buildings.
Soil and water contaminated around heavily trafficked
areas by past burning of lead-containing gasoline in automobiles also can
be a problem.
"When it burned off as an emission, it fell to the ground,"
Brown said. "It doesn't break down."
Some manufacturing processes, batteries and munitions
are other common sources of lead contamination.
The standard method of detecting lead now is sampling,
say, paint or soil at a site and testing the samples in a lab with mass
spectrometry, essentially burning them to measure the tell-tale signs of
burning lead. That's both expensive and time consuming.
Bird said there are some existing on-site testing methods,
but they either don't provide an accurate reading of the lead level or
cost too much, particularly for local health departments.
Lu's method uses DNA, the genetic material that carries
the codes, or sequences, that make us blue-eyed, red-haired, lanky and
the like.
In this case, the DNA was manufactured rather than naturally
occurring, and culled by Lu and Li from a huge pool of different DNA types
for its reactivity to lead.
Basically, tiny lead particles, called ions, strike and
cleave a strand of the DNA when the metal is present.
In its normal state, the DNA is fluorescent, Lu said.
The method he and Li developed attaches the DNA strand to a "quencher"
that prevents the glowing.
When the lead ions cleave the reactive DNA, it separates
from the quencher and lights up, which gives off a signal. The more lead
present, the greater the signal's strength.
Lu is now searching for types of DNA that react similarly
to other metals, such as mercury.
In the future, he envisions a chip with several different
types of DNA attached that can detect different kinds of metals. The idea
isn't unheard of, Lu said. The nose works largely on the same principles
in detecting a variety of smells.
"We have to come up with all the DNAs," he said. "I think
it has a lot of promise."