Polymer Glass Coating Creates Germ-Free Surfaces

Originally Published MDDI January 2002

R&D DIGEST

Polymer Glass Coating Creates Germ-Free Surfaces

Science has made numerous attempts to create surfaces with inherent bactericidal properties capable of rendering them germ free. Thus far, these attempts have been unsuccessful, but researchers at Northeastern University (Boston), working with colleagues at the Massachusetts Institute of Technology (Boston) and Tufts University (Medford, MA), believe they may have developed a method for creating permanently germ-free dry surfaces.

The researchers speculated that previous efforts to design dry bactericidal surfaces failed because the polymer chains that made up the material were not sufficiently long and flexible enough to penetrate bacterial cell walls. According to Kim Lewis, professor of biology at Northeastern University, their research has demonstrated that covalent attachment of N-alkylated poly(4-vinylpyridine) (PVP) to glass can make surfaces permanently lethal to several types of bacteria on contact.

The group found a narrow range of N-alkylated PVP compositions that enable the polymer to retain its bacteria-killing ability when coated on dry surfaces. Lewis and the other team members believe that these are the first engineered surfaces proven to kill airborne microbes in the absence of a liquid medium.

To overcome the limitations of previous compositions, which had polymer chains of insufficient length and flexibility, their polymer includes a long "linker" that enables the toxic N-alkylated pyridine groups to cross the bacterial envelope. According to the researchers, dry surface-bonded PVP with no N-alkyl chains or long N-alkyl chains, including 10 or more carbon units, is not bactericidal. However, three- to eight-unit PVP chains derive a sufficient positive charge from the cationic pyridine nitrogen to repel each other and stay flexible and sufficiently hydrophobic to penetrate bacterial cell walls.

The researchers indicate that surfaces fabricated in this way kill 94% to 99% of bacteria sprayed on them. Because the coating is chemically bonded to the surface, it will not be affected by being touched or washed.

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