Women someday could protect themselves against sexually transmitted infections by using a gel that uses nanoparticles to deliver drugs to the vaginal walls, a new study in mice suggests.

Researchers used the gel to deliver an anti-herpes drug to the mice and found that the technology tripled the level of protection that the drug normally provides against a herpes infection.

It's possible the gel's protection could be made to be long-lasting, so it could be applied hours before sexual intercourse, according to the study, which appears today (June 13) in the journal Science Translational Medicine.

If the gel is found fit for human use, the composition of the gel makes it likely that a woman could use it discreetly, without her partner noticing it, the researchers added.

To see just how much the nanoparticle delivery system improved a drug's effectiveness, the researchers purposefully chose an anti-herpes medication that was not particularly effective, and a strain of herpes virus that was remarkably infectious.

“We could protect animals fairly well, with a wimpy drug, against a strong herpes infection,” said study researcher Justin Hanes, director of the Center for Nanomedicine at the John Hopkins School of Medicine.

The research has yet to be tried in people, and rodent studies often don't hold up in humans. Under ideal circumstances, clinical trials of the gel could be possible within a year or two, Hanes said.

The trick to developing the gel was making the particles small enough and slick enough to get through the mucus that coats the inside of the vagina. Hanes likened the problem to a bug trying to fly through a spider web.

“There could be a bug that's small enough to fit through a spider web, but that doesn't mean it will get through without getting stuck,” he said. But with small, “non-sticky” nanoparticles, the drug was evenly applied across nearly 100 percent of the vaginal surface — a feat given the vagina's complex, folding walls, Hanes said.

When they applied the anti-herpes drug to mice, the researchers found that the drug's effectiveness in preventing herpes increased from 16 percent without the nanoparticles, to 53 percent with the nanoparticles.

Those results are quite promising, said Chi Lee, a professor at the University of Missouri's Kansas City School of Pharmacy, who was not involved with the research.

The new technology could be used to administer a “microbicide agent against any type of sexually transmitted disease, including AIDS or HPV cancer,” Lee said. The research could make a great impact on clinical practice, he added.

Hanes said this type of drug application could be particularly important for women because it could give them more control over their sexual health.

While condoms are certainly very effective at preventing sexually transmitted infections, some people don't like to use them, and in some cases, women are unable to get their partners to wear them.

“Women in developing countries need a discreet method of protection,” Hanes said.

Lee noted that modeling the human sexual experience with mice is difficult, so differences between mice and people, in terms of the gel's effectiveness, are likely to be seen when they research the possibility of human use.

The researchers said they believe the gel's mechanism will work the same way in humans.

The gel could have applications other than preventing sexually transmitted infections, the researchers said. The technology could be applied to penetrating mucus at other sites, such as the eyes, ears, nose, mouth or rectum, and could treat diseases, such as inflammatory bowel disease or lung cancer, that develop in mucus-covered body surfaces.

Pass it on: Women may soon be able to protect themselves from STDs with a new gel that uses nanoparticles.

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