In a new study reported in the journal Advanced Functional Materials, University of Utah scientists developed a gel-type of “molecular condom” to protect women from AIDS.

Women apply the gel prior to sexual intercourse. The gel turns semisolid in the presence of semen and is able to trap AIDS virus particles before they infect vaginal cells.

This new technology was designed particularly for women living in impoverished areas such as sub-Saharan Africa and South Asia, who will now be able to protect themselves from HIV without needing the approval of their partner.

The issue of developing effective microbicides, compounds or substances whose purpose is to reduce infectivity of viruses and bacteria, has been plaguing scientists for years.

In 2006, the same team of University of Utah scientists had developed a different “molecular condom” that was applied vaginally as a liquid, turned into a gel coating at body temperature, and then, in the presence of semen, turned into a liquid and released an anti-HIV drug. However, very few antiviral drugs bind to and attack HIV in semen. Additionally, high temperatures became an issue in Africa because they prevented the gel from turning into a liquid.

The main difference between the new and old “molecular condom” is that the new one becomes semisolid and forms a linkage of molecules, in response to a change in the vaginal pH (acidity or alkalinity) from the introduction of semen to the vagina.

The change in pH modifies the strength of the bond between the two main components of the gel, phenylboronic acid (PBA) and salicylhydroxamic acid (SHA). PBA and SHA are polymers, or large molecules, consisting of repeating structural units that are joined by chemical bonds.

During normal acidic vaginal conditions (pH 4.8), the chemical bonds between PBA and SHA repeatedly join together and separate, which allows the gel to flow smoothly. However, when semen enters the vagina, conditions become alkaline (pH 7.6), a condition in which PBA and SHA link together tightly, which slows down the flow of the gel dramatically.

The polymers form an extremely small mesh from the cross linkages, approximately 30 to 50 nanometers in size. An HIV particle is about 100 nanometers wide.  Due to its smaller size, the mesh is able to block out HIV particles.

Researchers used a specialized microscope, marking HIV particles with a fluorescent dye to track how fast they moved when they were caught in the gel and how the speed varied as a result of pH changes. They found that the movement of HIV particles in acidic conditions was much slower in the presence of the gel’s microscopic mesh.  Additionally, HIV particles reacted with the polymers, further slowing down their movement.

After sexual intercourse, the vaginal acidity returns and would inactivate any residual HIV particles. The gel may also prevent AIDS by blocking the movement of immune system cells that are vulnerable to infection by the AIDS virus.

Additionally, the researchers believe that adding an antiretroviral drug, such as Viread (tenofovir), may improve the effectiveness of the “molecular condom” because HIV would have to get past both the polymer barrier and the drug barrier.

Furthermore, the gel may serve as a contraceptive because of its ability to block sperm, and it may also block other viruses, such as herpes and human papillomavirus.

For more information, please see the study in Advanced Functional Materials (abstract) or the related article in Science Daily.