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
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.
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.
Phone : (514) 343-6671
: Natural Sciences and Research Council of Canada (NSERC),
Société Air Liquide (France).
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.
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."
Phone : (514) 343-6204