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Plume from Plasma Pencil Shown to Kill Leukemia Cells

The plasma pencil, a miniature light saber that Old Dominion University's Mounir Laroussi created more than five years ago, has been shown in recent tests to kill leukemia cells, according to a paper published in the Journal of Physics D: Applied Physics by Laroussi's research team.

A broad array of popular media, including National Geographic, as well as professional publications have noted the germ-killing applications, and the ease of use, of Laroussi's plasma pencil. In the past few years, the ODU electrical engineer has collaborated with life scientists at the university to study the way the so-called "cold" plasma that shoots from his hand-held pencil can kill diseased cells and bacteria.

Now, Laroussi and Nazir Barekzi, a research scientist with ODU's Laser and Plasma Engineering Institute, which Laroussi directs, have published "Dose-dependent Killing of Leukemia Cells by Low-temperature Plasma." The article was given special treatment as a "fast track communication" when it was released online earlier this month by the Applied Physics journal.

The researchers found that the morphology and viability of human T-cell leukemia cells were affected in a dose-dependent manner after treatment with low-temperature atmospheric pressure plasma pulses fired from the plasma pencil. The leukemia cells were treated in vitro in a tissue culture plate.

"The outcome of this study revealed that the effect of plasma exposure was not immediate, but had a delayed effect, and increasing the time of plasma exposure resulted in increased leukemia cell death," they wrote in the article.

Laroussi cautioned that the investigations are preliminary, but he said he believes the results hold promise as a component of a leukemia treatment.

"First, let me say that we are not at the stage where we can apply our plasma as a therapy for leukemia, or any other cancer," he said. "At the present time we are doing fundamental scientific studies to evaluate the effects of low-temperature plasma on cancer cells. So far we have killed with some degree of success metastatic prostate cancer from a site in the brain, and leukemia cells."

What sort of treatment application might he envision from results showing that leukemia cells can be killed outside of the body by the low-temperature plasma?

"I was asked the same question by a reporter from MedicalPhysicsWeb," Laroussi said. "Here is my answer: 'Leukemia results from an overabundance of white blood cells. Controlling the number of white cells by killing them would restore the balance in the blood and could be a partial solution to a cure. This could be conceived in a similar way to a dialysis machine where blood could be subjected to plasma outside of the body. Killing cancerous white blood cells, however, may not be enough, as it does not deal with the root of the problem. Plasma could be conceived as part of a larger solution that involves treatment of bone marrow, for example.'"

Laroussi's specialty is the plasma that can be created in regular atmospheric conditions and can be used - in dental or wound-healing treatments, for example - without burning normal human tissue. Conventional plasma, like that present in lightning and in television sets, is created in the absence of atmospheric pressure and is radically hot.

Both plasmas have been shown to kill germs, but the low-temperature version has gotten more attention for biomedical applications because it is safer and easier to use.

The plasma pencil, which is about the size of an electric toothbrush, used helium gas as a medium for the plasma created in the leukemia cell studies. Results indicate that high doses of low-temperature plasma prevent leukemia cell proliferation and are able to induce cell death. In addition, the results indicate that low doses of this plasma have a delayed, but statistically significant, killing effect on leukemia cells.

Barekzi and Laroussi are currently planning tests of the efficacy of low-temperature plasma directed against different types of cancerous cell lines, as well as additional research to try to nail down the underlying mechanisms that allow low-temperature plasma treatments to bring about the death of cancer and bacteria cells.

In the past, Laroussi has collaborated with bacteriologist Wayne Hynes, chair of ODU's Department of Biological Sciences, to conduct tests to see if cold plasma could kill E. coli bacteria on green beans without affecting the look or taste of the beans. Laroussi called the results "encouraging."

Laroussi, together with Michele Darby and Gayle McCombs of ODU's School of Dental Hygiene have used the plasma pencil to kill oral-borne bacteria that cause periodontal diseases. Darby is an Eminent Scholar, University Professor and the dental hygiene chair. McCombs is a University Professor and director of ODU's Dental Hygiene Research Center.

Plasmas are a super-excited "soup" that have been called the fourth state of matter - quite different from solids, liquids and gases. Cold plasmas are cool to the touch because only the very lightweight electrons in them are energized, and not the heavier nuclei. But for reasons not yet fully understood, these non-thermal plasmas can kill or inactivate bacteria and cancer cells while at the same time enhancing the proliferation of healthy cells. Experiments have shown them to be useful for sterilization, treatment of disease and wound healing.

In July 2012 Laroussi was the recipient of the IEEE-NPSS Merit Award for his pioneering work on the biomedical applications of plasma. The Merit Award is the highest technical award given by IEEE at the society level.

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