The Molecular Condom - vaginal gel releases Anti-HIV drug when exposed to semen

"Up until now, most of the microbicide work has focused on the development of the active drug, not on the delivery of the drug," Kiser says. "This study and other work in my lab are directed at developing new technologies for vaginal delivery of antiviral agents, particularly a microbicide that can respond to triggers [body temperature and semen] that are present before, during and after intercourse. This is the first paper that begins to point in that direction."

Kiser says the dosage of anti-HIV drugs in first-generation microbicides lasts only a few hours, so "you have to use them an hour before sex, which is difficult. You only need one failure to get the disease. We're shooting for a microbicide delivery system that would be used once a day or once a month."

In the study, Kiser and colleagues outline how they designed a water-based gel or "hydrogel" sensitive to body temperature and pH (acidity or alkalinity) so that it could serve as a "smart semen-triggered vaginal microbiocidal vehicle."

The researchers have not yet tried incorporating an antiviral drug into the hydrogel, but showed that in laboratory conditions, the substance turns from a liquid to a gel at body temperature, then returns to liquid form and can release test compounds – stand-ins for antiAIDS drugs – when exposed to semen, which has a pH of 7.5, more alkaline than the acidic vaginal pH of 4 to 5.

Kiser conducted the research with University of Utah bioengineering graduate students Kavita Gupta and Meredith Roberts, and undergraduates Scott Barnes and Rachel Tangaro. The research is part of Gupta’s doctoral thesis, and she did much of the work. Other coauthors of the study were bioengineers David Katz and Derek Owen at Duke University in Durham, N.C. The National Institutes of Health funded the study. Designing a Microbicide to Empower Women

First-generation microbicides now being tested are expected to be available within four years and be 50 percent to 60 percent effective. That sounds low, but a British study found that even if a microbicide was only 50 percent effective against HIV and used by only 20 percent of the women in 73 developing nations, it would prevent 2.5 million infections during a three-year period. Kiser says he hopes the molecular condom ultimately will prove to be 90 percent effective.

Potential side effects of microbicides include itching, increased vaginal discharge and inflammation. But initial testing of the molecular condom – in which the hydrogel was tested on basic tissue cells known as mouse fibroblasts – "indicates these gels are likely to be well tolerated," Kiser says.

What about the comfort of a thin gel lining the vagina? "At the end of the day, women will use a material that protects them," he says. "But there is no reason to think these gels are uncomfortable."

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