Tuesday, January 02, 2007

Remotely Activated Nanoparticles Destroy Cancer

Targeted nanotech-based treatments will enter clinical trials in 2007.

By Kevin Bullis

Microscopic gold particles and nanoshells (shown here in solution) can be tuned to absorb different wavelengths of light--a feature that is proving useful for cancer treatment. Credit: Corey Radloff and the Halas Group, Rice University

The first in a new generation of nanotechnology-based cancer treatments will likely begin clinical trials in 2007, and if the promise of animal trials carries through to human trials, these treatments will transform cancer therapy. By replacing surgery and conventional chemotherapy with noninvasive treatments targeted at cancerous tumors, this nanotech approach could reduce or eliminate side effects by avoiding damage to healthy tissue. It could also make it possible to destroy tumors that are inoperable or won't respond to current treatment.

One of these new approaches places gold-coated nanoparticles, called nanoshells, inside tumors and then heats them with infrared light until the cancer cells die. Because the nanoparticles also scatter light, they could be used to image tumors as well. Mauro Ferrari, a leader in the field of nanomedicine and professor of bioengineering at the University of Texas Health Science Center, says this is "very exciting" technology.

"With chemotherapy," Ferrari says, "we carpet bomb the patient, hoping to hit the lesions, the little foci of disease. To be able to shine the light only where you want this thing to heat up is a great advantage."

Although several groups are now working on similar localized treatments, Naomi Halas and Jennifer West have led the way in this area, and their work is the farthest along. (See "Nano Weapons Join the Fight Against Cancer.") Nearly ten years ago, Halas, professor of chemistry and electrical and computer engineering at Rice University, developed a precise and reliable method for making nanoshells, which can be hollow spheres of gold or, in the case of the cancer treatment, gold-coated glass spheres. These spheres are small enough (about 100 nanometers in diameter) to slip through gaps in blood vessels that feed tumors. So as they circulate in the bloodstream, they gradually accumulate at tumor sites.

Halas tuned the nanoparticles to absorb specific wavelengths of light by changing the thickness of the glass and gold. For the cancer treatment, she selected infrared wavelengths that pass easily through biological tissues without causing damage. To destroy a nanoshell-infiltrated tumor, the tumor is illuminated with a laser, either through the skin or via an optical fiber for areas such as the lungs.

"We shine light through the skin, and in just a few minutes, the tumor is heated up," Halas says. "In the studies that were initially reported--and this has been repeated now more than 20 times in at least three different animal models--we have seen essentially 100 percent tumor remission." The tests also suggest the nanoshells are nontoxic. Halas says they are eliminated from the body through the liver over several weeks. The technology was developed at Rice in collaboration with Jennifer West, a professor of bioengineering. It has been licensed by Nanospectra Biosciences, a startup based in Houston, TX, that is beginning the process of getting FDA approval for clinical trials for treating head and neck cancer. In the future, the technology could be used for a wide variety of cancers.