Abstract
Synchrotron radiation is a useful tool to elucidate initial processes leading to various radiobiological effects, since we can induce selectively X-ray photoabsorption at desired elements in cells by tuning X-ray energy to the absorption edges of the element. At inner shell ionized or excited atoms, Auger effects occur and several low energy electrons are emitted around the photo-absorbing atom, producing complex and severe damages around the site.(element selective irradiation) On the other hand, we recently developed an X-ray microbeam irradiation system with monochromatic X-rays. Energy of X-rays is restricted to 5.35 keV, since the beam is deflected right angle upward using diffraction of Si(311), in order to irradiate the samples through the bottom of the dish. (site selective irradiation).
In order to realize combined irradiation of site-selective and element- selective, we have constructed an energy-tunable X-ray microbeam irradiation system. As a dish to irradiate cells we decided to employ a commercially available one with bottom made of thin glass, which was developed for use with confocal laser microscopes. Cells attached on the bottom are kept humid by covering with a thin Kapton film after the medium is suctioned out just before irradiation. Physiological condition of cells after treated in sham irradiation process was found good enough to obtain reliable and reproducible results. Several studies have started and some preliminary results will soon be reported.
