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

The molecular condom is a polymer – a molecule with a repeating, chain-like structure – made from three chemicals in these proportions:

* 80 parts of N-isopropylacrylamide. * 15 parts of butyl methacrylate, which is used in coatings, adhesives, solvents, resins, oil additives and to finish leather and paper. * Five parts acrylic acid, which is used in lubricant and spermicidal gels.

"The three together have the property of liquid at room temperature and vaginal pH, solid at body temperature and vaginal pH, and liquid at body temperature and semen pH," Kiser says.

Other researchers previously discovered this combination of chemicals forms a heat-sensitive gel, but Kiser and colleagues altered the polymer so it would change from liquid to gel and back at the desired temperature and pH. They also designed the gel so it would not dehydrate vaginal cells, which can trigger infections.

The researchers analyzed and optimized the gel’s ability to adhere to a surface similar to vaginal tissue without being diluted by other fluids, but to erode rapidly in the presence of seminal fluid. Kiser says first-generation microbicides use gels like those in spermicides and lubricants, and are not optimized to coat and be retained in the vagina.

A Burst of Anti-AIDS Medicine

Kiser, Gupta and colleagues demonstrated how the polymer could change from liquid to gel at body temperature, then return to liquid form when exposed to simulated seminal fluid – a sticky mixture of sugars and salt—and release large and small molecules used as stand-ins for real medicines in drug-delivery experiments.

In the experiments, when the hydrogel molecular condom was exposed to mock seminal fluid, it released 49 percent of the small-molecule drug within five minutes and 81 percent within an hour. It released 48 percent of the large molecule drug within 30 minutes and 66 percent in 90 minutes.

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