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

Abstract

Successful removal of cholesterol ester which is specifically accumulated in the arteriosclerotic region on the arterial walls was achieved by the exposure of5.75tm-infraredfree-electron-1asers (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). Wefound that the exposure of 5.75tm-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 (R2C=O) bonds. Further, we exposed cholesteryl oleate to FELs having wavelength of5.75tm, 9.4ORm and8.44tm. From changes in absorbance andthickness of the samples, we calculated quantum efficiency 1 for decrease of ester bonds and C-C chains for each wavelength-EEL exposure. 1 was obtained to be 2.1x104 forester bondand 1.2x1Ofor C-Cchainby 5.75.tm-FELs,O.9x1O and2.0x104 by 9.4Otm-FELs, and 1.2x104 and 1 .0x104 by 8.44m-FELs. Thus, we canconcludethat removal ofcholesteryl oleate by IR-FELs has the wavelength sensitivity coming from correspondence between the bonds which absorbs FEL photons and which aimed to remove.