レーザアブレーションが引き起こす生体系組織コラーゲン膜の光-熱変換機

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In order to gain obvious insight into the role of water in the mechanism of the excimer laser ablation of the cornea, we have macroscopically investigated the ablation behavior of collagen gel in swelled states by direct photoetching using an ArF excimer laser with time-resolved photography, and furthermore the thermal effects on the microscopic structures of collagen -olecules by FTIR-ATR spectroscopy. As for the dried collagen film (DF), a well-defined periodic structure ascribed to a Fresnel diffraction of the laser beam at the edge of the aperture was observed in the irradiated region by AFM, whereas for the hydrated collagen film (HF), the irregularity of the surface structure for HF was created by the heat through photo-thermal conversion and/or boiling of water in the gel matrix. FTIR-ATR spectroscopic results revealed that the existence of the water suppressed the denaturation of collagen to gelatin on the surface in the irradiated region. After all, it was inferred that during the ablation process for HF,the laser energy would be consumed as the latent heat of evaporation of water, accompanied by the suppression of the increment in the surface temperature in the irradiated region and further for the denaturation of the collagen.