Tiny Gold-Coated Beads Kill Cancer Cells
The nanoshells leave healthy, neighboring cells alone, a new study says.
By Steven Reinberg,
TUESDAY, Nov. 4 (HealthDayNews) -- New experiments in the science of the
super-small suggest that nanoshells coated with gold and placed into
cancerous tumors will kill only malignant cells when external
near-infrared light is applied.
The nanoshells used in these experiments are microscopic silica beads,
according to the report in this week's issue of the Proceedings of the
National Academy of Sciences.
A gold coating is used because it absorbs energy turning it into heat, and
can also carry biological markers that direct the nanoshells to their
Nanotechnology is the study of finding practical uses of minuscule items,
and in medicine it is how to insert those items in a body in a way to
heal. Researchers study at the level of a nanometer, which is so small it
would take 80,000 of them to equal the diameter of a human hair.
The research team speculated that when near-infrared light -- a type of
low-energy radiation that does not affect living cells -- was applied to
the nanoshells, they would become hot enough to kill the tumor cells, but
the tissue outside the tumor would be unaffected.
"We can use nanoshells as a localized heat source in tissues to heat the
cells to 55 degrees Celsius [131 degrees Fahrenheit] to induce cell
death," says co-researcher Naomi Halas, a professor of electrical and
computer engineering and a professor of chemistry at Rice University.
The researchers tested their technique on human breast cancer cells and on
cancerous tumors grown on mice. In each case, the combination of
nanoshells and near-infrared light caused irreversible heat damage to
tumor cells while leaving surrounding tissue unharmed.
These nanoparticles can be used to induce cell death in specific areas,
while leaving the surrounding tissue unharmed and at normal temperatures,
Halas suspects that this nanoshell technology can be used to replace or
supplement chemotherapy and surgery.
"The nice thing about nanoshells is that you can attach antibodies or
proteins to their surfaces to target specific tissue types or specific
cells the way chemotherapy does. But the advantage is that unlike
chemotherapy, nanoshells are benign, so there would be very few side
effects," she says.
In ongoing studies, the researchers are finding that after serving their
purpose, nanoshells are eliminated from the body.
Halas' team is also looking at several mechanisms that can be used to mark
the nanoshells so they reach their intended tissue targets when injected
into the body.
"This is a very interesting piece of work on the use of
near-infrared-absorbing nanoshells for photothermal treatment of cancer, "
says Shuming Nie, director of cancer nanotechnology and an associate
professor of biomedical engineering and chemistry at Emory University.
Nie notes the key finding in the paper is that when heat is applied, the
temperature increases enough to induce cell death.
However, "it is unclear whether these large nanoshell particles. . . could
be selectively delivered to small metastasized tumors upon systemic
injection, a very different process from direct tumoral injection," Nie
To learn more about cancer and nanotechnology, visit the National Cancer
Institute, while the Institute of Nanotechnology in Britain explains
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Last Updated: November 04, 2003