| GOLD DUST & DNA
By Sean Henahan, Access Excellence
Evanston, Ill. (22 August 1997) A new probe combining nanoparticles
of gold and DNA oligonucleotides could provide a new generation of tests
for genetic and pathogenic diseases.
The researchers create two batches of DNA strands as probes, with each
probe sequence complementary to half of the sequence of a third or target
strand. The key
step involves attaching gold-binding thiol groups to the two sets of
DNA probes. When mixed with gold nanoparticles, gold particles coated with
dozens of DNA strands result. Combined the two sets of DNA-coated particles
with the target DNA results in the the first probe linking to half of the
target DNA strand, and the second probe to the other half, causing the
target strand to bridge the two probes.With amplification, the process
produces a three-dimensional web, producing a color change from red to
blue when the target DNA is present.
Preliminary tests indicate that the new diagnostic modality provides
a high level of sensitivity and specificity, according to co-inventor Chad
A. Mirkin, professor of chemistry at Northwestern University: "This process
is likely to be faster, cheaper and more selective than existing diagnostic
tools."
This represents an important safety innovation, since current DNA hybridization
assays often require the use of radioactive phosphorus or sulfur tracers
in the probes. This creates a need for specially trained personnel, creates
disposal problems and uses material with short shelf lives.
"The method should be particularly useful in assays where expense and
simplicity in instrumentation and operation are important," says Mirkin.
Using the new gold-DNA probes eliminates those problems, because no
radioactive materials are used, and the solution is stabilized to give
it the longer shelf life needed for a useful diagnostic tool, Mirkin notes.
The new findings follow earlier research which led to the development
of the process for tailoring the optical, electrical, mechanical
and structural properties of the gold-DNA combination material. Nanoparticles
have a diameter one-billionth of a meter, so small they can't be seen with
conventional microscopes.
The new material could also prove useful in forensics, mass screenings
for pathogens in clinical or laboratory settings and detection of biological
weapons, Mirkin said.
The research results appear in the August 22, 1997 issue of Science
magazine.
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