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Advances made by Old Dominion University engineers in biomedical applications for cold plasmas are described in the December 2007 issue of Physics Today, the journal of the American Institute of Physics.

Karl Schoenbach and Mounir Laroussi, two faculty members in the Department of Electrical and Computer Engineering, are quoted extensively in a feature article that summarizes potential uses of cold plasmas in procedures ranging from bacterial decontamination to cancer treatments. The article has a broad scope, also including developments from Stanford University and Eindhoven University of Technology in the Netherlands.

Research done at the Frank Reidy Research Center for Bioelectrics, which Schoenbach directs, and the Laser and Plasma Engineering Institute, which Laroussi directs, is the focus of the article.

"This is a great article summarizing the work being done, and it puts ODU at the
forefront of this field," said Schoenbach, who is Batten Endowed Chair in Bioelectrics and who founded the Reidy Center in 2003. "We are beginning to get the attention we need. The ball is rolling."

Schoenbach and Laroussi were identified by a national business magazine six years ago as leaders in cold plasma research and development. Plasmas are highly charged super gases that we see in nature as lightning and in industry as the electric arc of a welding device. More recently, engineers have developed cold plasmas that range in temperature in the atmosphere of Earth from about 200 degrees Fahrenheit to cool-to-the-touch.

Some cold plasmas that are too hot to touch can be use for sterilization. But even at cool temperatures, the plume emitted by the plasma pencil that Laroussi developed in 2005 can kill plaque-causing bacteria in the mouth without harming healthy tissue. Laroussi's plasma pencil has been the subject of numerous articles in scientific journals and general interest publications, including National Geographic, and was shown on televised documentaries.

Schoenbach is a pioneer in applications of ultra-fast pulsed, high-voltage electricity. At the Reidy Center, researchers have used this pulsed power to bring about remission of skin tumors in mice.

Pulsed power also can ignite a gas medium such as helium to create cold plasma. "The timed pulses keep the temperature down," Laroussi says in the article. Pulses excite the electrons of the helium atoms without stirring up the much heavier nuclei, and this moderates the temperature of the plasma.

Although cold plasmas may not kill bacteria with heat, they "inactivate bacteria through a combination of the plasmas' free radicals, charged particles and emitted UV radiation, all of which work together to disrupt the integrity of bacterial cell membranes," the article explains. The UV radiation, Laroussi is quoted as saying, "can damage the DNA strands (of cells), while charged particles can charge the cell wall and cause electrostatic disruption."

The article notes that the plume of Laroussi's plasma pencil appears to kill bacterial cells while sparing healthy mammalian cells, perhaps because the bacteria are simpler in structure and their DNA is not as well protected. "We think cold plasma will have an increasingly bigger role to play in healthcare and could revolutionize the way in which plasmas can be used in medicine," Laroussi states. For the First International Conference on Plasma Medicine, which took place in Corpus Christi in October, Laroussi was on the Scientific Organizing Committee. The conference brought together physicians and plasma physicists to discuss the promising role of cold plasma in the medicine.

Schoenbach says that more scientific investigation is needed. "We don't understand very much about the underlying mechanisms" of cold plasma biomedical applications, he told the Physics Today writer. "What is causing these effects, and how can we gain better control over the plasmas?"

This article was posted on: December 6, 2007

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