Ionized Plasmas as Cheap Sterilizers for Developing World

This sounds really useful, particularly for drug resistant bacteria. [Link]

"We know plasmas will kill bacteria in water, but there are so many other possible applications, such as sterilizing medical instruments or enhancing wound healing," said chemical engineer David Graves, the Lam Research Distinguished Professor in Semiconductor Processing at UC Berkeley. "We could come up with a device to use in the home or in remote areas to replace bleach or surgical antibiotics."

Low-temperature plasmas as disinfectants are "an extraordinary innovation with tremendous potential to improve health treatments in developing and disaster-stricken regions," said Phillip Denny, chief administrative officer of UC Berkeley's Blum Center for Developing Economies, which helped fund Graves' research and has a mission of addressing the needs of the poor worldwide.

"One of the most difficult problems associated with medical facilities in low-resource countries is infection control," added Graves. "It is estimated that infections in these countries are a factor of three-to-five times more widespread than in the developed world."

Graves and his UC Berkeley colleagues published a paper in the November issue of the Journal of Physics D: Applied Physics, reporting that water treated with plasma killed essentially all the E. coli bacteria dumped in within a few hours of treatment and still killed 99.9 percent of bacteria added after it sat for seven days. Mutant strains of E. coli have caused outbreaks of intestinal upset and even death when they have contaminated meat, cheese and vegetables.

Based on other experiments, Graves and colleagues at the University of Maryland in College Park reported Oct. 31 at the annual meeting of the American Vacuum Society that plasma can also "kill" dangerous proteins and lipids -- including prions, the infectious agents that cause mad cow disease -- that standard sterilization processes leave behind.

In 2009, one of Graves' collaborators from the Max Planck Institute for Extraterrestrial Physics built a device capable of safely disinfecting human skin within seconds, killing even drug-resistant bacteria.

"The field of low-temperature plasmas is booming, and this is not just hype. It's real!" Graves said.

In the study published this month, Graves and his UC Berkeley colleagues showed that plasmas generated by brief sparks in air next to a container of water turned the water about as acidic as vinegar and created a cocktail of highly reactive, ionized molecules -- molecules that have lost one or more electrons and thus are eager to react with other molecules. They identified the reactive molecules as hydrogen peroxide and various nitrates and nitrites, all well-known antimicrobials. Nitrates and nitrites have been used for millennia to cure meat, for example.

Graves was puzzled to see, however, that the water was still antimicrobial a week later, even though the peroxide and nitrite concentrations had dropped to nil. This indicated that some other reactive chemical -- perhaps a nitrate -- remained in the water to kill microbes, he said.