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Image of cancer cell
illuminated by gold nanorods bound to anti-EFGR(Image courtesy
of Georgia Institute of Technology) |
Researchers at the Georgia Institute of
Technology and the University of
California, San Francisco, have found an
even more effective and safer way to
detect and kill cancer cells. By
changing the shapes of gold nanospheres
into cylindrical gold nanorods, they can
detect malignant tumors hidden deeper
under the skin, like breast cancer, and
selectively destroy them with lasers
only half as powerful as before –
without harming the healthy cells. The
method, which allows for a safer, deeper
penetrating noninvasive cancer
treatment, has just appeared in the
Journal of the American Chemical
Society, volume 128.
Last year, the father and son research
team of Mostafa El-Sayed and Ivan El-Sayed,
showed that gold nanoparticles coated
with a cancer antibody were very
effective at binding to tumor cells.
When bound to the gold, the cancer cells
scattered light, making it very easy to
identify the noncancerous cells from the
malignant ones. The nanoparticles also
absorbed the laser light more easily, so
that the coated malignant cells only
required half the laser energy to be
killed compared to the benign cells.
This makes it relatively easy to ensure
that only the malignant cells are being
destroyed.
Now, they've discovered that by changing
the spheres into rods, they can lower
the frequency to which the nanoparticles
respond from the visible light spectrum
used by the nanospheres to the
near-infrared spectrum. Since these
lasers can penetrate deeper under the
skin than lasers in the visible
spectrum, they can reach tumors that are
inaccessible to visible lasers.
"With the nanospheres we’re using
visible lasers, but most of the solid
cancer is under the tissues and visible
light doesn’t go but a few millimeters
deep. But by using the nanorods we can
tune them to react to the infrared
lasers, which can penetrate the tumor
without being absorbed by the tissues,”
said Mostafa El-Sayed, director of the
Laser Dyanamics Laboratory and Regents’
professor of chemistry at Georgia Tech.
Many cancer cells
have a protein, known as Epidermal
Growth Factor Receptor (EFGR), all over
their surface, while healthy cells
typically do not express the protein as
strongly. By conjugating, or binding,
the gold nanorods to an antibody for
EFGR, suitably named anti-EFGR,
researchers were able to get the
nanoparticles to attach themselves to
the cancer cells.
In this latest study, researchers
incubated two malignant oral epithelial
cell lines and one benign epithelial
cell lines with nanorods conjugated to
anti-EFGR. Not only were the malignant
lines clearly identifiable as such under
a simple optical microscope, but after
being exposed to a continuous sapphire
laser in the near infrared spectrum, the
malignant lines only required half the
laser energy to kill them as the healthy
cells.
"This makes it more practical than the
sphere in terms of treating cancer,”
said Mostafa El-Sayed. “For laser
phototherapy treatment of skin cancer
or, for diagnostic biopsies, the spheres
are fine, but for phototherapy of cancer
deep under the skin, like breast cancer,
then one really needs to use the
nanorods treatment.”
Source:
Georgia Institute of Technology
Published on 18th
MARCH 2006
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