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Heated nanoshells kill cancer cells

30 Jun 2004

Tiny infrared-absorbing particles prove their worth by treating tumors in mice.

US researchers are hailing a non-invasive treatment which destroys tumors by heat a success after the first phase of animal testing. According to the team from Rice University and its licensee, Nanospectra Bioscience, the method has eradicated tumors in mice and does not affect healthy tissue. (Cancer Letters 209 171)

The technique relies on tiny gold-coated particles called nanoshells which, when injected into the bloodstream, selectively accumulate in tumors. By varying the size of the core and the thickness of the gold shell, the team tailors the nanoshell to convert near-infrared light into heat. The heating is said to be localized and does not affect healthy tissue close to the tumor.

"We are extremely encouraged by the results of these first animal tests," said Jennifer West from Rice's department of bioengineering. "These results confirm that nanoshells are effective agents for the photothermal treatment of in vivo tumors."

West's nanoshells comprise a 110 nm diameter silica core covered by a 8 to 10 nm thick gold shell. The nanoshells have a peak optical absorption between 805 to 810 nm. The treatment involves shining 808 nm light from a fiber-coupled 800 mW diode laser on the tumor for three minutes.

The trial involved 25 mice, some of which were injected with nanoshells. The researchers report that after 30 seconds of laser exposure, the temperature in the nanoshell-treated tumors had risen to around 50°C which was significantly higher than their nanoshell-free controls.

West and colleagues say that the tumors in the nanoshell-treated mice had disappeared ten days after treatment. Tumors in the animals that had not received a nanoshell injection continued to grow rapidly.

"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," said Naomi Halas of Rice's department of electrical and computer engineering. "We have licensed the technology to Nanospectra Biosciences which will obtain the necessary approvals and funding for human trials."

Jacqueline Hewett is technology editor on Optics.org and Opto & Laser Europe magazine.

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