Infrared free-electron-laser ablation of cholesterol esters in an arteriosclerotic region

摘要

Successful removal of cholesterol ester which is specifically accumulated in the arteriosclerotic region on the arterial walls was achieved by the exposure of 5.75μm-infrared free-electron-lasers (FEL) which is absorbed by C=O stretching vibrations of ester. In this study, chemical bond-changes and decrease in amount of cholesteryl oleate in IRFEL photodynamic processes were examined by Fourier transform infrared microspectroscopy (FT-IR). We found that the exposure of 5.75μm-FELs induces not only dissociation of ester (RCOOR') bonds but also the oxidation process of the ester (RCOOR') bonds to aldehyde (RCHO), carboxylic acid (RCOOH), carboxylate (RCOO~-) or ketone (R_2C=O) bonds. Further, we exposed cholesteryl oleate to FELs having wavelength of 5.75μm, 9.40μm and 8.44μm. From changes in absorbance and thickness of the samples, we calculated quantum efficiency Φ for decrease of ester bonds and C-C chains for each wavelength-FEL exposure. Φ was obtained to be 2.1 * 10~(-4) for ester bond and 1.2 * 10~(-4) for C-C chain by 5.75μm-FELs, 0.9 * 10~(-4) and 2.0 * 10~(-4) by 9.40μm-FELs, and 1.2 * 10~(-4) and 1.0 * 10~(-4) by 8.44μm-FELs. Thus, we can conclude that removal of cholesteryl oleate by IR-FELs has the wavelength sensitivity coming from correspondence between the bonds which absorbs FEL photons and which aimed to remove.