Lewis, former associate professor at Tufts' Biotechnology Center, along with MIT's Joerg C. Tiller, Chun-Jen (Jason) Liao, and Alexander M. Klibanov, have found a fairly narrow range of N-alkylated PVP compositions that allow the polymers to retain their bacteria-killing ability when coated on dry surfaces. These are the first engineered surfaces that have been shown to kill airborne microbes in the absence of any liquid medium.
Previous efforts to design dry bactericidal surfaces were continuously unsuccessful, the researchers hypothesized, because the polymer chains weren't sufficiently long and flexible enough to penetrate bacterial cell walls. Their polymer includes a long "linker" that enables the toxic N-alkylated pyridine groups to cross the bacterial envelope. The researchers found that dry surface-bonded PVP with either no N-alkyl chains or long N-alkyl chains (10 or more carbon units) is not bactericidal. But three- to eight-unit PVP chains, however, have sufficient positive charge (from the cationic pyridine nitrogen) to repel each other and stay flexible and sufficiently hydrophobic to penetrate bacterial cell walls.
Such surfaces kill 94% to more than 99% of bacteria sprayed on them, and because the coating is chemically bonded to the surface, it doesn't come off when touched or washed. The surface treatment is potentially long-lasting and capable of being scaled up to commercial production at moderate cost, being applied as a paint or coating. The goal is to make any common surface capable of killing airborne bacteria.