| Analyzing
a blood sample for the presence of disease markers,
either in a doctor’s office or on the battlefield, could
soon become as quick and easy as scanning the bar-code
of a grocery item. Using nanotechnology, researchers
at Northwestern University have developed a way to label
tiny disease markers in blood with unique DNA tags,
which they call bio-bar-codes. The tags can then be
scanned by an instrument to identify diseases ranging
from cancer to Alzheimer’s, or identify exposure to
bioterror agents such as anthrax and smallpox, they
say.
Details
about the analytical test, which appears promising
in experimental studies, are scheduled to appear in
the May 19 print issue of the Journal of the American
Chemical Society, a peer-reviewed publication of the
American Chemical Society, the world’s largest scientific
society. The study was published online today (April
27) on the journal’s Web site.
“This
test has the potential to completely revolutionize
medical diagnostics,” says Chad A. Mirkin, Ph.D.,
head of the study and director of Northwestern’s Institute
for Nanotechnology, located in Evanston, Ill. He says
that the test will bring efficient, high-tech DNA
diagnostics to unprecedented settings, including the
battlefield and Third World villages, as well as hospitals
and the home.
The
test is easier, faster, more accurate and less expensive
than polymerase chain reaction (PCR), which is currently
used to detect and quantify DNA samples, he says.
The new test, called bio-bar-code amplification (BCA),
could be ready for marketing in as little as one year,
Mirkin says.
Unlike
conventional tests that require one or more vials
of blood, the new test allows a single drop of blood
to paint a patient’s comprehensive disease profile
in about the same amount of time it takes for a routine
doctor’s visit.
The
test is based on a set of chemical probes that are
used to tag disease markers. If one is trying to detect
exposure to anthrax, for instance, a set of probes
is prepared that represents a unique molecular tag
for anthrax-related DNA. One probe includes a magnetic
nanoparticle containing a single DNA strand that matches
the target (anthrax) DNA. The other probe consists
of a gold nanoparticle attached to a DNA strand that
also matches the target (anthrax) DNA. The gold nanoparticle
is also attached to hundreds of DNA bar-code sequences
that are unique identification tags for the anthrax
target DNA. If anthrax is present in the blood, its
DNA marker is then sandwiched between the two probes,
separated magnetically, scanned and identified.
So
far, the test has proven accurate in detecting anthrax
lethal factor — a marker for anthrax exposure. It
has also been used to detect prostate specific antigen
— a marker for prostate cancer — at low levels. One
could conceivably develop a bar-code for every disease-related
protein or DNA sequence, according to Mirkin.
Current
scanners that can read the bar-codes are bulky, stationary
instruments, but a handheld prototype is in development.
If all goes well in future studies, bar-code scanning
of blood could be developed for home use, allowing
consumers to make their own initial medical diagnoses
quickly and easily, says Mirkin.
Nanosphere,
a company that develops nanoparticle-based biodetection
technology for medical diagnostics, was started four
years ago by Mirkin.
Funding
for this research was provided by the Air force Office
of Scientific Research, the Defense Advanced Research
Projects Agency, the National Science Foundation and
the National Institutes of Health.
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