NEWS: Targeting tumors using tiny gold particles
http://web.mit.edu/newsoffice/2009/print/gold-cancer-0504-print.html
MIT news
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Gold nanorods could detect, treat cancer
It has long been known that heat is an effective weapon against tumor
cells. However, it's difficult to heat patients' tumors without damaging
nearby tissues. Now, MIT researchers have developed tiny gold particles that can home in
on tumors, and then, by absorbing energy from near-infrared light and
emitting it as heat, destroy tumors with minimal side effects. Such particles, known as gold nanorods, could diagnose as well as treat
tumors, says MIT graduate student Geoffrey von Maltzahn, who developed the
tumor-homing particles with Sangeeta Bhatia, professor in the Harvard-MIT
Division of Health Sciences and Technology (HST) and in the Department of
Electrical Engineering and Computer Science, a member of the David H. Koch
Institute for Integrative Cancer Research at MIT and a Howard Hughes Medical
Institute Investigator. Von Maltzahn and Bhatia describe their gold nanorods in two papers
recently published in Cancer Research and Advanced Materials. In March, von
Maltzahn won the Lemelson-MIT Student Prize, in part for his work with the
nanorods. Cancer affects about seven million people worldwide, and that number is
projected to grow to 15 million by 2020. Most of those patients are treated
with chemotherapy and/or radiation, which are often effective but can have
debilitating side effects because it's difficult to target tumor tissue. With chemotherapy treatment, 99 percent of drugs administered typically
don't reach the tumor, said von Maltzahn. In contrast, the gold nanorods can
specifically focus heat on tumors. "This class of particles provides the most efficient method of
specifically depositing energy in tumors," he said. Wiping out tumors
Gold nanoparticles can absorb different frequencies of light, depending on
their shape. Rod-shaped particles, such as those used by von Maltzahn and
Bhatia, absorb light at near-infrared frequency; this light heats the rods
but passes harmlessly through human tissue. In a study reported in the team's Cancer Research paper, tumors in mice
that received an intravenous injection of nanorods plus near-infrared laser
treatment disappeared within 15 days. Those mice survived for three months
with no evidence of reoccurrence, until the end of the study, while mice that
received no treatment or only the nanorods or laser, did not. Once the nanorods are injected, they disperse uniformly throughout the
bloodstream. Bhatia's team developed a polymer coating for the particles that
allows them to survive in the bloodstream longer than any other gold
nanoparticles (the half-life is greater than 17 hours). In designing the particles, the researchers took advantage of the fact
that blood vessels located near tumors have tiny pores just large enough for
the nanorods to enter. Nanorods accumulate in the tumors, and within three
days, the liver and spleen clear any that don't reach the tumor. During a single exposure to a near-infrared laser, the nanorods heat up to
70 degree Celsius, hot enough to kill tumor cells. Additionally, heating them
to a lower temperature weakens tumor cells enough to enhance the
effectiveness of existing chemotherapy treatments, raising the possibility of
using the nanorods as a supplement to those treatments. The nanorods could also be used to kill tumor cells left behind after
surgery. The nanorods can be more than 1,000 times more precise than a
surgeon's scalpel, says von Maltzahn, so they could potentially remove
residual cells the surgeon can't get. Finding tumors
The nanorods' homing abilities also make them a promising tool for
diagnosing tumors. After the particles are injected, they can be imaged using
a technique known as Raman scattering. Any tissue that lights up, other than
the liver or spleen, could harbor an invasive tumor. In the Advanced Materials paper, the researchers showed they could enhance
the nanorods' imaging abilities by adding molecules that absorb near-infrared
light to their surface. Because of this surface-enhanced Raman scattering,
very low concentrations of nanorods - to only a few parts per trillion in
water [gf1]- can be detected. Another advantage of the nanorods is that by coating them with different
types of light-scattering molecules, they can be designed to simultaneously
gather multiple types of information - not only whether there is a tumor, but
whether it is at risk of invading other tissues, whether it's a primary or
secondary tumor, or where it originated. Bhatia and von Maltzahn are looking into commercializing the technology.
Before the gold nanorods can be used in humans, they must undergo clinical
trials and be approved by the FDA, which von Maltzahn says will be a
multi-year process. Other authors of the Advanced Materials paper are Andrea Centrone,
postdoctoral associate in chemical engineering; Renuka Ramanathan,
undergraduate in biological engineering; Alan Hatton, the Ralph Landau
Professor of Chemical Engineering; and Michael Sailor and Ji-Ho Park of the
University of California at San Diego. Park and Sailor are also authors of the Cancer Research paper, along with
Amit Agrawal, former postdoctoral associate in HST; and Nanda Kishor Bandaru
and Sarit Das of the Indian Institute of Technology Madras. The research was funded by the National Institutes of Health, the Whitaker
Foundation and the National Science Foundation. Nanopartz Inc. supplied gold
nanoparticles, gold nanowires and the precursor gold nanorods used in this work. URL: http://web.mit.edu/newsoffice/2009/gold-cancer-0504.html
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