The Role of Free Radicals in the Photodynamic Treatment of Fibrotic Skin Diseases

The first derivatives of gelatin and type I collagen fluorescence spectra were characterized in order to describe the effect of free radicals on pyridinoline (PYD) cross-links. The different gas saturation conditions were used to investigate the effect of different free radicals. An analysis of first derivative fluorescence spectra suggests that PYD cross-link fluorescence emission is composed of three peaks in gelatin, but only two in type I collagen. The PYD cross-link was photo-degraded more than other gases in the presence of O 2 . This suggests that the singlet oxygen ( 1 O 2 ) plays a key role when using photodynamic therapy to treat skin fibrosis disease with Hypocrellin B (HB).