Optimization of light action spectra for porphyrins in vivo

Abstract

Light action spectra for main skin chromophores are simulated. Porphyrins are selected as target chromophores. They can produce singlet oxygen (SO) reactions under tissue irradiation, which acts as a natural photosensitizer. The SO is toxic for, e.g. cancer cells. This process is known to be widely used in photodynamic therapy (PDT). It is shown by way of examples that skin irradiation by red light, where the porphyrins have local maxima of light absorption, can improve the generation of SO as compared with the irradiation at a wavelength corresponding to the absolute maximum of light absorption. Taking etio- and rhodoporphyrin as target chromophores, we obtained that the said improvement of SO generation can be about 5 to 100 times at specific depths inside tissue and 10 to 20 times integrally for the whole dermis thickness. The presented results can provide new opportunities for the selection of the irradiation wavelengths under application of traditional PDT methods.