Designer surface proves deadly to bacteria

Using a novel approach to microbe killing, a team of researchers has made a new coating that could render countertops, computer keyboards, and even hospital sheets permanently antiseptic.

A chemically modified glass slide (left) kills bacteria that thrive on an ordinary glass slide (right). Joerg C. Tiller et al.

Unlike most antibacterial treatments, which lose microbe-repelling power as their active components leach out, the new surface coating has an enduring, built-in chemistry for killing bacteria on contact, says team member Kim Lewis, a microbiologist at Tufts University in Medford, Mass. The only care these surfaces require is an occasional wipe to remove dead bacteria, the researchers say.

Lewis and his colleagues altered the surface chemistry of glass slides by coating them with polymer molecules of a class known to destroy bacteria in water. The scientists found that the slides coated with long and rigid versions of the polymers killed between 94 and 100 percent of four types of bacteria sprayed onto them. They report their findings in the May 22 Proceedings of the National Academy of Sciences.

When one end of each bacteria-killing molecule binds to the glass, its other end can penetrate a bacterium’s cell membrane and kill the microbe, conjectures team member Alexander M. Klibanov, a chemist at the Massachusetts Institute of Technology. The most effective polymer is known as hexyl-PVP.

Bacteria are not likely to develop a resistance to this killing mechanism, as they do to other methods (see related story, this page), because no single gene could make the membrane invincible. Another benefit: The newly designed surface kills even hard-to-attack, airborne bacteria, such as those lofted during a sneeze or delivered by an air duct.

The surface modification is not limited to glass, adds Klibanov. Researchers could use the coating method to create permanent antiseptic coatings for door knobs, toys, and pay phones, for example, he says. Such a coating would be attractive to him personally, says Klibanov, speaking to Science News from a pay phone. “You don’t know who touched the phone before you did,” he notes.

The coating does not kill all the bacteria that land on it, comments Jonathan Dordick, a chemical engineer at Rensselaer Polytechnic Institute in Troy, N.Y. However, the figures cited by the researchers are “a pretty good start,” he says, and the new method is both simple and elegant. He adds, “I can’t think of any solution like this that’s been done for airborne microbes.”

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