Skip to Content

Molecular Condom Blocks HIV

A novel gel that filters out HIV could protect women from infection.
August 12, 2009

A polymer gel that blocks viral particles could one day provide a way for women to protect themselves against HIV infection. The gel reacts with semen to form a tight mesh that blocks the movement of virus particles. The material, which is still in early development, could eventually be combined with antiviral gels currently in clinical trials to provide a dual defense against HIV.

Viral blockade: A gel, shown here stained blue, forms tendril structures at pH 7.4. The red dots are 100 nanometer particles, about the same size as HIV, which are trapped in these structures.

Scientists have been working on microbicide gels for HIV for more than a decade. This type of prophylactic, which women could use without relying on their partners, is of particular interest in areas such as Sub-Saharan Africa, where HIV-infection rates are high and use of condoms is relatively low. But development has been slow–a number of products have failed clinical trials.

Most of the topical microbicides being tested for HIV prevention contain antiviral drugs designed to block replication of the virus once it infects a cell. The new gel, which is being developed by Patrick Kiser and colleagues at the University of Utah, in Salt Lake City, acts at the first stage of infection–when the virus moves from semen to the surface of vaginal tissue.

“This research stresses improvement not in the drugs but in the vehicle used to deliver the drugs,” says Ian McGowan, a physician and scientist at the University of Pittsburgh Medical Center who was not involved in the research. “That’s a relatively neglected area, and the technology is quite exciting.”

Kiser and colleagues developed a gel from two polymers–PBA (phenylboronic acid) and SHA (salicylhydroxamic acid)–that can be spread around the vagina prior to intercourse. With the introduction of semen, the vagina reaches a higher pH level, causing molecules in the gel to bind together, creating a finer mesh that prevents HIV particles from passing through. “The idea is to use the trigger of semen to activate the gel and create a more effective barrier,” says Kiser.

In research published this week in the journal of Advanced Functional Materials, researchers showed in lab tests that the gel can block the movement of HIV particles, and that it appears safe when tested in human vaginal cells. The next step is to test the gel on human tissue collected from women who have had hysterectomies to show that it can prevent infection.

“It’s a very interesting approach to take advantage of normal vaginal physiology and alter it to inhibit HIV transmission,” says Craig Hoesley, an infectious-disease specialist at the University of Alabama, in Birmingham. But this might also prove troublesome. McGowan points out that the change in pH after intercouse can be variable, so researchers need to show that the gel can react under different chemical conditions.

Kiser and his team ultimately want to combine this type of gel with an antiviral drug in order to block both the movement of HIV and its replication. But extensive testing, including safety testing, remains to be done. For example, for use in Sub-Saharan Africa, the gel must be stable at different temperatures. “We will also need to see if it is compatible with antiviral drugs,” says McGowan.

Keep Reading

Most Popular

DeepMind’s cofounder: Generative AI is just a phase. What’s next is interactive AI.

“This is a profound moment in the history of technology,” says Mustafa Suleyman.

What to know about this autumn’s covid vaccines

New variants will pose a challenge, but early signs suggest the shots will still boost antibody responses.

Human-plus-AI solutions mitigate security threats

With the right human oversight, emerging technologies like artificial intelligence can help keep business and customer data secure

Next slide, please: A brief history of the corporate presentation

From million-dollar slide shows to Steve Jobs’s introduction of the iPhone, a bit of show business never hurt plain old business.

Stay connected

Illustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at with a list of newsletters you’d like to receive.