For years, researchers have been working on microbicides (intravaginal gels, rings, and films) that can prevent the transmission of viruses such as the human immunodeficiency virus (HIV). Only a handful ever made it to human clinical trial, and ran into issues such as women not using them, or the antiviral drugs in the microbicides not lasting long enough. Some microbicides even seemed to increase the risk of transmission.
Now, researchers at the University of Utah seem to have greatly improved on a microbicide they first wrote about in 2006, according to a study published this week in the journal Advanced Functional Materials.
Their original molecular condom was applied as a liquid, which then turned into a gel coating at body temperate, and then turned liquid again in the presence of semen (which alters pH balance to be less acidic), thereby triggering the release of an anti-HIV drug. Problem was, few antiviral drugs bind and attach to HIV in semen, and high temperatures tended to prevent the gel from turning to liquid to activate the drug at all.
Their new condom works in the opposite way, starting as a gel but becoming semi-solid in response to pH changes caused by the introduction of semen, thereby forming a nanoscopic mesh of crosslinked molecules so tightly woven that they form a serious barrier to the virus:
The new gel is applied as a gel, and then becomes more solid and impenetrable as changes in pH alter the strength of the bond between the gel's two key components, both of which are polymers, or long, chain-like molecules made of many smaller, repeating units: PBA, or phenylboronic acid, and SHA, or salicylhydroxamic acid.
According to the University of Utah press release, the mesh of molecules--at 30 to 50 nanometers wide--should be able to block any HIV particle, which is two to three times thicker (roughly 100 nanometers wide). This should also block sperm, which measure 5,000 to 10,000 nanometers (5 to 10 microns). One way to think about this nano scale is that a strand of human hair is generally about 100,000 nanometers wide (100 microns), making it 10 to 20 times thicker than sperm and 2,000 to 3,333 times thicker than an HIV particle.
What if the virus were to get past the double barrier of this nanoscopic mesh and the accompanying antiviral drug? The study's senior author, Patrick Kiser, an associate professor of bioengineering at the University of Utah's College of Engineering, says that after sex the vagina gradually becomes more acidic again, and any residual HIV particles would be inactivated by not only this acidity, but also the antiviral drug (such as tenofovir) within the remaining gel.
The team's research, which is funded by the National Institutes of Health and the Bill and Melinda Gates Foundation, could be truly groundbreaking for women the world over. Still, one of the problems researchers ran into during the 2006 study--that some women failed to use the gel--won't necessarily be solved by a better gel.
It remains unclear whether failure to use the gel was because sex was forced and women didn't have time to apply it, or they just didn't believe it would work, or they were ridiculed, or felt ashamed, etc. What is clear is that hurdles remain when it comes to condoms, even if the chemistry is good.