Nonlinear photodynamic therapy using saturation of the photosensitizer triplet states

Abstract

Photosensitized oxidation of furfuryl alcohol under conditions simulating photodynamic therapy in vitro has been studied. The dependency of the photodynamic dose (PD) on the light dose in the medium that simulates tissue at continuous- and pulsed-mode irradiation was measured. In the first case, the relationship is linear and, in the second case, the PD exhibits a saturation level in the increasing energy density of the pulse. This saturation is due to the saturation of the triplet states of the photosensitizer. The possibility of calculating the change in the PD with the depth of the tissue under different photodynamic therapy conditions in vivo is shown on the basis of the data obtained. The results show a significant advantage of nonlinear photodynamic therapy over the traditional (linear) one due to the possibility to treat thicker tumors with less damage to the tissue surface.