Physics
Plasma sterilization could kill prions

After HIV and antibiotic resistant bacteria, hospital environments have to deal with another contamination problem: prions. These are extremely pathogenic protein particles that are responsible, among other things, for spongiform encephalophies such as Mad Cow disease and Creutzfeldt-Jakob disease.

There is practically no low-cost method for sterilizing medical instruments that effectively eliminates prions, so that the general procedure is to destroy instruments when they have been used in surgery on a patient suspected of being infected by prions. Some of the instruments are worth as much as $100,000! Others are made of plastics and cannot stand up to autoclave sterilization, where temperatures are very high.

But work done by a multi-disciplinary team under the direction of Michel Moisan, Professor in the Department of Physics and head of the Plasma Physics Group at Université de Montréal, has just opened up a promising new alternative. An experiment conducted on spores of a non-pathogenic bacterium (Baccillus subtilis) demonstrated that plasmas break down the spores atom by atom, and that this process could also be effective on prions.

In physics, the term "plasma" refers to a gas of ions and electrons. For their experiment, Michel Moisan's group used a mixture of nitrogen and molecular oxygen which, once ionized by an intense electric field, liberates free radicals (in this case, oxygen atoms) and photons in the ultraviolet range. The spores are actually bacteria in a dormant state that protect themselves from a hostile environment by sheathing themselves in a very resistant membrane. They were cultivated by Jean Barbeau in the microbiology and immunology laboratory of the Faculty of Dentistry. After 40 minutes' exposure to the gas from the plasma source, the several million spores in the test were destroyed. "We believe that the sterilization effect is due to the combined action of ultraviolet photons and free oxygen atoms," noted Michel Moisan. The UV photons alone may be sufficient to kill the spores by destroying their genetic material, but only if the spores are in a single layer. Because the penetrating action of the photons is limited to one micron, they cannot reach spores below the first layer if these are in layers.

Researcher : Michel Moisan
Phone : (514) 343-6671
Funding : Natural Sciences and Research Council of Canada (NSERC),
Société Air Liquide (France).

A million dollars from NASA to detect gamma rays

For the past six years, physicist Louis-André Hamel has been working to develop a gamma ray detector that could one day be sent into space. At any event, the prototype developed in the René J.A. Lévesque Laboratory, which measures just 1 cm2, seemed sufficiently promising to NASA that the American space agency has set aside a budget of $1 million for the work of this professor in the Department of Physics at Université de Montréal, in conjunction with researchers at the Space Science Center at University of New Hampshire.

Several dozen teams around the world are working to develop the ideal detector," explains the researcher. "But our prototype has passed efficiency and resolution tests with a margin of error of less than 1 mm."

In the visible and invisible spectra, gamma rays hold a special place. Regarded as the most energetic electromagnetic rays, they are just like visible light except that they have a higher energy and frequency (more than 1019 Hertz). They are also being studied more and more by physicists.
Known since 1969, the phenomenon of gamma ray bursts intrigues researchers in particular. Approximately once a day, a heavy influx of gamma rays is captured at different places on Earth. At the beginning, the higher flux was attributed to clandestine nuclear tests, until researchers showed that they originated outside the Earth. "These gamma rays bursts are produced at several billion light years distance and are the most spectacular events in the Universe," the physicist explains. "In a few seconds, a single one emits more energy than our sun is capable of producing during its entire existence."

Researcher : Louis-André Hamel
Phone : (514) 343-6204
Funding:NASA