Health & Medicine / Pharmaceuticals

A prophylactic polymer is a gel at body temperature (above) but turns liquid on contact with sperm (below).

In ancient times, condoms were made from sheaths of linen, leather, or animal intestine. Time and technology led to more effective versions fashioned out of vulcanized rubber, polyurethane, and latex. Now biomedical engineers David Katz of Duke University and Patrick Kiser of the University of Utah may have hit on the next big thing in condomology: an HIV-preventing polymer that is sensitive to both heat and sperm.

Designed for women, their "smart molecular condom" is liquid at room temperature but solidifies into a gel that stays in place for up to 24 hours when warmed by the body. When the gel comes in contact with semen, the change in pH causes it to reliquefy and release an HIV-killing microbicide. Kiser and Katz are working on both a spermicide-laden version and one without so that women could still conceive while protecting themselves against sexually transmitted diseases. The polymer will be tested in animals later this year. If it can be produced cheaply enough, the condom could help eliminate the gender imbalance in HIV exposure and slash transmission rates in hard-hit areas like sub-Saharan Africa. "Depending on what study you read, the rate of transmission from male to female is 10 to 1,000 times higher than female to male," Kiser says. "Now, for a woman to protect herself requires condom negotiation—that's an issue here as well as in the developing world."

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