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内容記述 |
We investigated DNA damage formation induced by a focused near-infrared (NIR) femtosecond (fs) laser. Recently, an NIR-fs laser, e.g., Ti:Sapphire laser (~800 nm, ~10^9 W/cm^2), has been employed to investigate excited state dynamics in DNA, exploiting its ultrashort pulse duration and high peak power. A focused beam (~10^11 W/cm^2) has been used for single-cell radiation biology as a microbeam source, and for nanosurgery of cells and tissues. Moreover, intense NIR-fs laser filamentation was applied to cancer therapy. When such an intense laser pulse is focused into a medium, a laser filament is formed by nonlinear effects of focusing and defocusing. The common events occurring in the media interacting with the intense NIR-fs laser pulses are ionization of water, plasma formation, and subsequent radical chain reactions. Although the fs laser holds significant promise for application in discovering hidden biological functions and for the innovative development of medical applications, the information on underlying physicochemical mechanisms and details of chemical reactions are limited. In our study, we observed that the DNA damage per laser shot decreased as the laser repetition rate increased, and that extraordinarily short DNA fragments were produced even at low dose (Akamatsu, K., et al., J. Photochem. Photobiol. B 258, 112994 (2024)). These findings suggest that an intense laser pulse induces a specific DNA damage profile that is not induced by a sparsely ionizing radiation such as X-rays. |
