ARLINGTON, Va., May 18, 2005 -- Biomedical engineers have used nanotechnology
to find human melanoma tumors in mice while the growths are still invisible
to conventional magnetic resonance imaging (MRI).
Earlier detection can potentially increase the effectiveness
of treatment. This is especially true with melanoma,
which begins as a highly curable disorder, then progresses
into an aggressive and deadly disease.
A second benefit of the approach is that the same
nanoparticles used to find the tumors could potentially
deliver stronger doses of anti-cancer drugs directly
to the tumor site with fewer side effects.
Samuel Wickline, M.D., professor of medicine, physics,
biomedical engineering and cellular physiology at
Washington University in St. Louis, and his colleague,
Gregory Lanza, M.D., Ph.D., associate professor of
medicine, have detected tumors as small as a couple
of millimeters in diameter.
"This technique may be employed to noninvasively
detect very small regions of angiogenesis associated
with nascent melanoma tumors," the researchers reported
in a recent issue of the journal Magnetic Resonance
in Medicine .
To zero in on the small tumors, the researchers
developed nanoparticles, thousands of which could
fit in the period at the end of this sentence. Each
particle was filled with thousands of molecules of
the metal that is used to enhance contrast in conventional
MRI scans. The surface of each particle was decorated
with a substance that attaches to newly forming blood
vessels, which are present at tumor sites. The goal
is to create a high density of the glowing particles
at the site of tumor growth so they are easily visible.
One group of mice bearing human melanoma tumors
was injected with the nanoparticles and two other
groups of animals were injected with other, more
conventional contrast enhancers. The animals underwent
MRI scans. Those injected with the nanoparticles
glowed brightly at the tumor sites. The control groups
showed no discernable glow.
Lanza said the nanoparticles can be made to work
in other types of medical imaging, such as nuclear
imaging, computed tomography (CT), and ultrasound.
It may also be possible to load the nanoparticles
with drugs to kill the tumors.
"When drug-bearing nanoparticles also contain an
imaging agent, you can get a visible signal that
allows you to measure how much medication got to
the tumor," said Lanza, who treats cancer patients
at Barnes Jewish Hospital. "You would know the same
day you treated the patient if the drug was at a
Targeting the drugs to the tumor site in this way
would also allow stronger doses than would be possible
if the drug were injected or delivered in some other
The researchers believe that nanoparticles might
also allow doctors to more readily assess the effectiveness
of the treatment by comparing before and after pictures.
Other cancer types might be accessible to this approach
as well, because all tumors recruit new blood vessels
as they grow.
studies , Wickline and Lanza demonstrated the
use of a similar nanotechnology for detecting sites
where blood-vessel plaques are just beginning to
form, well before they pose a risk of heart attack
Clinical applications of these lines of research
are being explored under a $7.3 million grant from
the National Heart, Lung, and Blood Institute of
the National Institutes of Health. In 1995, Wickline
received a Whitaker Foundation Special Opportunity
Award for cardiovascular bioengineering.
Samuel Wickline ,
Frank Blanchard ,
The Whitaker Foundation
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