Patients battling the blood cancer leukemia could one day receive a new
type of treatment that uses a plasma – a gas of electrically charged particles
– to kill cancer cells while keeping the healthy cells intact, according to new
research.
"We have a really amazing
device," says Mounir Laroussi, director of the laser and plasma
engineering institute at Old Dominion Univ., "We can generate a beam of plasma that is around room
temperature. It doesn't burn anything; it doesn't destroy or poke holes. You
can touch it with your hand."
After 10 minutes of treatment
with the cold-plasma blowtorch, over 90 percent of leukemia cells were
destroyed, according to the study published by Laroussi and research scientist
Nazir Barekzi in the Journal of
Physics D: Applied Physics.
Leukemia is the most common
childhood cancer and is responsible for almost one-third of all cancer-related
deaths in children, according to the Leukemia and Lymphoma Society. Currently,
leukemia survivors can lead healthy lives but long-term side-effects of the
treatments, including chemotherapy, radiation therapy and bone marrow
transplants, remain serious, says Laroussi.
Cold plasma, on the other hand,
is made from near room-temperature nontoxic gases and is not believed to have
negative long-term side effects.
Scientists create cold plasma by
sending super-speedy electrons through gasses like helium and air. These
electrons hit the atoms and molecules with so much energy that they pull off
the outermost electrons of the atoms and molecules in the gas, creating a soupy
mixture of free electrons and free ions.
The gas remains at around room
temperature, Laroussi explains, because the energy required to separate the
electrons from their atoms quickly dissipates, leaving the gas ions cool.
When leukemia cells were treated
with the cold-plasma plume, the scientists found something unexpected: the
cells did not die right away.
"Rather, right after the
experiment – in the zeroth hour – the cells are still okay. But after four to
eight hours, they start dying," says Laroussi.
Laroussi believes that the
delayed effect of the plasma treatment indicates that it triggers a biochemical
reaction that provokes the cancer cell to kill itself. He says that targeting
cancer cells to induce cell-death while leaving healthy cells unharmed is the
key to developing effective leukemia treatments with plasma.
Laroussi's view is shared by
Michael Keidar, associate professor of Mechanical and Aerospace Engineering at
George Washington Univ., who was not involved in the study but whose laboratory
also researches plasma for cancer therapy.
One of the molecules in cold
plasma is an especially reactive oxygen molecule made of three oxygen atoms,
known as ozone, rather than the two atoms of oxygen molecules in the
air. Scientists have known since the early twentieth century that ozone
acts as a disinfectant and recent research has demonstrated that ozone kills
bacterial infections, an important innovation in treating wounds and
drug-resistant bacterial infections.
Keidar's laboratory has
identified that this ozone is a key player in targeting cancer cells. The
molecule is a natural byproduct of a cell's metabolic cycle, Keidar says.
Cancer cells have higher metabolisms than healthy cells, which leads to
naturally elevated levels of ozone. Adding the right amount of extra ozone to
the cancer cells can push their already elevated levels over the threshold and
trigger cell-suicide, or apoptosis. Healthy cells, with their slower
metabolisms, have ozone levels beneath this threshold and remain unscathed.
In addition to further work in
leukemia treatment, Laroussi says that there are many future applications for
low-temperature plasma. Laroussi's laboratory has studied cold plasma
treatments for leukemia, bacterial infections, and even as a potential
treatment for the plaques that cause Parkinson's and Alzheimer's diseases.
As more is understood about how
the plasma initiates cell death, Keidar says that scientists might develop
different kinds of plasmas and adapt the way they deliver the plasma to the
tissue for each disease. His lab is currently developing new ways of tailoring
plasma doses for skin, lung and brain cancers.
"We are also looking into a
detection mechanism that can determine where the cancer is, treat it with cold
plasma, and then check if the treatment works. It’s very exciting," says
Keidar.
Inside Science News Service, Halleh Balch
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