Photodynamic Cancer Therapy: The Underlying Laser Characteristics

Abstract

A photosensitizer (PS) is a substance composed of molecules that can occupy a higher level of excitation pursuant to a photon capture. Photofrin is the readily available and selected PS throughout this work despite its few inherent drawbacks namely, a fairly long in situ reminiscent time of up to three weeks following the injection and a low selectivity for tumor cells. Blue light can detect cancer whereas red light can treat the same. The latter unique attribute, chiefly due to the absorption spectral profile in the first NIR optical window, means that red light – around 700 nm – can penetrate deep enough into the tissue while suffering negligible attenuation. The red light promotes the PS from its ground state to a higher state of excitation (singlets and triplets). The molecules in the triplet state return to the ground state via phosphorescence, a long radiative relaxation mechanism allowing to produce singlet oxygen. Finally, the reaction of the biomolecules and singlet oxygen is conducive to the destruction of the tumor cells [1].