| Posted: August 22, 2007 |
Metal nanoshells respond to near-infrared light for tumor imaging and therapy |
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(Nanowerk News) Using metal nanoshells designed to both absorb and scatter near-infrared light, a team of investigators at Rice University has shown that such nanoparticles can both image and treat tumors in animals. Their experiments revealed complete tumor destruction in more than 80 percent of animals treated with these nanoshells ("Near-infrared resonant nanoshells for combined optical imaging and photothermal cancer therapy").
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Jennifer West, Ph.D., and Rebekah Drezek, Ph.D., led the team of investigators that developed and tested these nanoshells, constructed with a 120-nanometer-diameter silica core, a 12-nanometer-thick gold shell, and a surface coating of poly(ethylene glycol). To image the nanoshells in animals, the investigators used optical coherence tomography (OCT), which measures light scattered by an imaging contrast agent, in this case the nanoshells. Compared with other commonly used OCT contrast agents, the nanoshells produced a markedly enhanced signal from tumors that was readily distinguished from normal tissue. The investigators were able to image malignancies without needing to anesthetize the tumor-bearing mice.
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Once the researchers had located tumors, they then irradiated the tumors in half the animals with a fiberoptic, near-infrared laser. They then monitored tumor size and animal survival for 7 weeks after a single treatment. By day 12, tumors on all but two of the treated animals had disappeared completely. Because so many of the treated animals survived for the entire 7-week experiment, the investigators were unable to calculate median survival time. In contrast, untreated animals showed a median survival of 10 days.
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