Irradiation of mammalian cultured cells with a collimated heavy-ion microbeam

Funayama, Tomoo; Wada, Seiichi; Kobayashi, Yasuhiko; Watanabe, Hiroshi*

As the first step for the analysis of the biological effect of heavy charged-particle radiation, we established a method for the irradiation of individual cells with a heavy ion microbeam apparatus at JAERI-Takasaki. CHO-K1 cells attached on the thin film of ion track detector, CR-39, were automatically detected under fluorescent microscope, and irradiated individually with Ar ion (11.5 MeV/u, LET=1260 keV/m) microbeam. Without killing the irradiated cells, trajectories of irradiated ions were visualized as etch-pits by treatment of CR-39 with alkaline-ethanol solution at 37C. The exact positions of ion hits were determined by overlaying images of both cells and etch-pits. The cells that were irradiated with argon ions showed a reduced growth in post-irradiate observations. Moreover, a single hit of an argon ion to the cell nucleus resulted in strong growth inhibition. These results tell us that our truthful irradiation method now enables us to start a precise study of the cellular response of high-LET radiation effects on cells.