If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.



Driving A Spike Into Viruses

Polymers poke holes in lipid bilayers to kill viruses and pathogenic bacteria

by Celia Henry Arnaud
November 20, 2006 | A version of this story appeared in Volume 84, Issue 47

Credit: Courtesy of Alexander Klibanov
Klibanov (left) and Jayanta Haldar developed polymer paints that inactivate influenza virus.
Credit: Courtesy of Alexander Klibanov
Klibanov (left) and Jayanta Haldar developed polymer paints that inactivate influenza virus.

A charged polymeric coating that inactivates influenza virus and pathogenic bacteria might one day be used to kill infectious agents on surfaces such as door handles.

The idea comes from Alexander M. Klibanov and coworkers at MIT and their experience with glass slides coated with polyethylenimine polymers (Proc. Natl. Acad. Sci. USA 2006, 103, 17667). Within five minutes of putting influenza virus on the glass slide, all the virus is inactivated. The polymers stand up from the surface like spikes, which appear to poke holes in the virus's lipid envelope.

Earlier, the Klibanov group had shown that such coatings can kill bacteria. "We reasoned that a lipid envelope in viruses is not so different from a lipid membrane in bacteria," Klibanov says.

The hydrophobic nature of the polymers allows them to interact with viral or bacterial lipids, but the polymers must also be charged to work. Cationic polymers work better than anionic or zwitterionic polymers, which work much more slowly, and neutral polymers don't work at all. With no charge, the polymers interact with each other, forming a "spaghetti ball" structure that can't punch holes in the virus, Klibanov says. The charge makes these hydrophobic chains repel each other and stay erect in a spikelike configuration, he explains.

Lethal Weapons
Coatings made of cationic (right) or zwitterionic polyethylenimines eliminate influenza virus.
Coatings made of cationic (right) or zwitterionic polyethylenimines eliminate influenza virus.

In addition to helping the polymer stand upright, the charge allows the polymer to interact with the lipid envelope on the virus. "Clearly, there are areas of both positive and negative charge on the surface of the virus," Klibanov says. "Apparently, there are more areas of the negative charge, or at least those areas are more vulnerable."

The researchers mix the polymer with an organic solvent, which creates a "paint" that can be applied to any surface. The solvent evaporates, leaving the polymer adhered to the surface.

The Klibanov group has not completely elucidated the mechanism by which the polymers inactivate viruses, but they suspect that the polymers should work against any virus with a lipid coating. So far, Klibanov has shown effectiveness against two strains of influenza.

Killed viruses or bacteria can eventually block the surface, making it inactive, but wiping the surface with soapy water restores its activity, Klibanov says.

John Wood, an influenza expert at the National Institute for Biological Standards & Control in the U.K., cautions that the required five-minute contact time may limit the use of the polymer. "There would not be enough contact time to be useful in coating respiratory masks," he says. "However, in certain high-risk public areas such as clinic waiting rooms, there may be some benefit in coating door handles."

Jonathan Dordick, a chemical engineering professor at Rensselaer Polytechnic Institute, doesn't see the current contact time as a limitation. He suspects that the polymers can be optimized to work faster.

Dordick thinks it is unlikely that viruses or bacteria could evolve resistance to such coatings. "These materials are not likely to be degraded by any enzymatic method," he says. "I don't think that any of the major mechanisms that bacteria use to get out of trouble would be effective here."

Klibanov is collaborating with industry to address such issues as stability and resistance to cracking, both of which are required to make the polymer coating practical. He is currently working with Boeing, the airplane manufacturer.


This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.