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Printer FriendlyReprinted with permission from Popular
Science, December 2000.
© Copyright, Times Mirror Magazines, Inc.
Gummy Drug Delivery
A NEW POLYMER material that gels in response to temperature may enable scientists to improve cancer treatments. Called a stimuli-sensitive polymer, it's a liquid at room temperature. But when exposed to temperatures above 90°F, the liquid becomes an opaque gel. By lacing a polymer solution with drugs or other substances, physicians could exploit this unique property to hold drugs in place while they are slowly released in the body.
"You can inject the polymer into the body, and the body will not dissolve it," explains senior research scientist Anna Gutowska, lead developer at the Department of Energy's Pacific Northwest National Laboratory in Richland, Washington.
The first application may be to improve upon an existing treatment, called brachytherapy, for early-stage prostate cancer, Gutowska says. In brachytherapy, surgeons implant radiation-emitting "seeds" that kill cancer cells ["New Weapons Against Prostate Cancer," August]. However, these seeds sometimes destroy healthy tissue, and they don't always irradiate the cancerous tissue uniformly.
Instead of implanting seeds individually, Gutowska's approach is to create "radiogels" containing tiny suspended particles of the radioactive isotope yttrium-90. Each particle emits radiation that travels only a short distance, so it is less likely to damage surrounding tissue. And since the particles are more closely spaced than the seeds, they are more likely to radiate uniformly.
Gutowska has already found that when radiogel is injected into mouse tumors, the particles do not migrate beyond the tumors. But she has yet to prove that the raidiogels can effectively irradiate cancerous tissue and that they are non-toxic. It will be at least two years before human testing begins.
Stimuli-sensitive polymers could also be used to reversibly sterilize people. And a biodegradable version could serve as a scaffold to hold cartilage cells in place to treat injured joints.—Dawn Stover
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