Surface coating kills germs on contact
07/01/2001
Mark A. DeSorbo
Will the life sciences and food processors welcome the added line of defense the coating offers?
MEDFORD, MA—Scientists at Tufts University and the Massachusetts Institute of Technology (MIT) believe they have developed an airborne bacteria-killing coating that can be applied to everything from cleanroom materials, like polyvinyl chloride and polyethylene, to plastics, metals, ceramics and fabric.
It took just eight attempts before Kim Lewis, associate professor of biotechnology at Tufts, and chemistry professors Jeorg C. Tiller, Chun-Jen Liao and Alexander Klibanov of MIT (Cambridge, MA) successfully attached a polymer, polyvinyl-pyrrolidone (PVP), to benzalkonium, a powerful antiseptic, which made the surfaces of glass slides toxic to potentially deadly bacteria like E. coli and staphylococcus.
The coating, Lewis maintains, can even be applied to everyday items like counter tops, doorknobs, telephones and toys. According to their research, scientist estimated that 94 to 99 percent of the bacterium sprayed onto treated and dried surfaces was killed. In addition, the coating is physically bonded to surfaces, so it does not wash off, outgas or particulate.
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Scientists at Tufts University (Medford, MA) and the Massachusetts Institute of Technology (Cambridge) have developed a surface coating that zaps airborn microorganisms on contact. Numerous colonies of bacteria were grown on the glass slide to lef, while the slide on the right was treated with the coating, dried and then exposed with the same bacteria.
"Bacteria is everywhere, and multi-drug resistant strains and diseases are a clear and present danger," he says, adding that Dupont, Dow Chemicals and Boeing have expressed interest in the discovery. "If people washed their hands more often, you wouldn't need this type of surface."
Eyeing the commercial market
It is anticipated, Lewis says, that life sciences employing contamination control against microorganisms, namely the pharmaceutical, biotechnology and food processing, will welcome the added line of defense the coating offers.
Thomas Gilmore, technical director of the International Association of Food Industries Suppliers (IAFIS; McLean, VA), says that industries who implement contamination control measures in the United States, like the dairy industry, will not likely embrace this technology in lieu of regular sanitation.
"Antibacterial agents in plastics have been available in Europe for quite some time and seem to have acceptance over there, at least in consumer goods," he says, adding that field experience and federal approval is needed before such coatings can be introduced and used.
Hank Rahe, a member of the CleanRooms Editorial Advisory Board and director of technology at Contain-Tech (Indianapolis), says a germ-killing surface coating is a fantastic concept, especially since it aims at killing nosocomial or hospital-borne diseases, but it has a long way to go.
"The durability would have to be proven, and if they're going to claim it's clean, they're going to have to prove it with data," he adds.
Lewis, the project's microbiologist, says he and his fellow scientists decided to design a sterile surface by using the antiseptic, benzalkonium, which attacks a microorganism's cell membrane and kills it.
Prior research, he says, indicated that polymers chemically bonded to an antiseptic kills bacterium by disrupting cell membranes, but immobilization often rendered them inactive.
The coating needed longer hydrophobic, or water repelling, side chains, which would cause the agents to resist the other. That's where the PVP, or what Lewis calls the linker, came in.
"We had to tinker with it a little bit," he says. "There were eight variations on the general design of the linker and the toxic chemical compound. It now allows the antiseptic to dangle on the end of a linker, reach inside the thick bacteria cell envelope and kill it."