Optical properties of model cholangiocarcinoma tissues in the spectral range of 350-2250 nm in laser photothermolysis treatment

Abstract

The paper presents the investigation of change of optical properties of the rat transplanted cholangiocarcinoma doped with gold nanorods after laser-induced plasmon-resonant photothermal treatment (PPT). 72, 48 and 24 hours before the experiment the animals were injected with the suspension of gold nanorods intravenously. For irradiation a diode laser with wavelength 808 nm was used. After the irradiation the tumors and surrounding tissues were removed and sliced. The samples studied were: skin, subcutaneous connective tissue, tumor capsule, top, center, and bottom part of tumor. Spectra of total transmittance and diffuse reflectance of the samples were measured in the wavelength range 350-2250 nm. Absorption and reduced scattering coefficients of the tumor tissues were calculated with inverse adding-doubling method. The results of the experiment were compared with result of investigation of the control tissues without gold nanorods injection and PPT. A decrease in the absorption coefficient of tumor layers in the water absorption bands was obtained, which indicated tissue dehydration during PPT. A decrease in the reduced scattering coefficient of tumor layers indicated an increase in the size of scatterers and an increase in their ordering. Changes in the optical parameters of the skin and subcutaneous layer were insignificant, which indicated a weak thermal damage.