Nanoshell Treatment Eradicates Tumors

A revolutionary new form of cancer therapy in development at Rice has proven effective at eradicating tumors in laboratory animals during the first phase of animal testing.ce.

The noninvasive cancer treatment uses a combination of harmless, near-infrared light and benign, gold nanoshells to destroy tumors with heat. The treatment does not affect healthy tissue.

“We are extremely encouraged by the results of these first animal tests,” says Jennifer West, the Isabel C. Cameron Professor of Bioengineering and professor in chemical engineering. “These results confirm that nanoshells are effective agents for the photothermal treatment of in vivo tumors.” Results of the study were published in the June 25 issue of the journal Cancer Letters.

Invented at Rice in the 1990s by Naomi Halas, gold nanoshells are 1/20th the size of red blood cells. They consist of a silica core covered by a thin layer of gold. The size, shape, and composition of the nanoshells give them unique optical properties. By varying the size of the core and the thickness of the gold, researchers can tailor a nanoshell to respond to specific wavelengths of light.

The photothermal cancer treatment uses nanoshells that are tuned to respond to near-infrared light, which passes harmlessly through soft tissue. The nanoshells convert this light into heat that destroys nearby tumor cells. The heating is very localized and does not affect healthy tissue adjacent to the tumor.

The animal trial involved 25 mice with tumors ranging in size from 3 to 5.5 millimeters. The mice were divided into three groups. The first group was given no treatment. The second received saline injections, followed by three minutes of exposure to near-infrared laser light. The final group received nanoshell injections and laser treatments.

Because the blood vessels inside tumors develop poorly, small particles such as nanoshells can leak out and accumulate inside tumors. In the test, researchers injected nanoshells intravenously into the mice, waited six hours to give the nanoshells time to accumulate in the tumors, then applied a 5-millimeter-wide laser beam on the skin above each tumor.

Surface temperature measurements taken on the skin above the tumors during the laser treatments showed a marked increase that averaged about 46 degrees Fahrenheit for the nanoshell group. There was no measurable temperature increase at the site of laser treatments in the saline group. Likewise, sections of laser-treated skin located apart from the tumor sites in the nanoshell group also showed no increase in temperature, indicating that the nanoshells had accumulated as expected within the tumors.

All signs of tumors disappeared in the nanoshell group within 10 days. These mice remained cancer-free after treatment.

Tumors in the other two test groups continued to grow rapidly. All mice in these groups were euthanized when the tumors reached 10 millimeters in size. The mean survival time of the mice receiving no treatment was 10.1 days; the mean survival time for the group receiving saline injections and laser treatments was 12.5 days.

“The results of these first animal studies are very promising, and while we don’t yet have a target date for our first human trial, our entire team is working hard to make this treatment available to cancer patients as soon as possible,” says Halas, the Stanley C. Moore Professor in Electrical and Computer Engineering and professor of chemistry. “We have licensed the technology to the Houston-based firm Nanospectra Biosciences Inc., which will obtain the necessary approvals and funding for human trials.”

This research was funded by the National Science Foundation under both a Small Business Technology Transfer grant to Nanospectra Biosciences and a National Nanotechnology Initiative grant to Rice’s Center for Biological and Environmental Nanotechnology.

——Jade Boyd