Photobleaching of Methylene Blue in Biological Tissue Model (Hydrolyzed Collagen) Using Red (635 nm) Radiation

Methylene blue (MB) is used for Photodynamic Therapy (PDT), with a protocol which is efficient, inexpensive, and safely, used for decades in clinical applications. The quantification of efficacy of a photosensitizer in aqueous solution is well known in literature. Photobleaching, a photoinduced degradation or modification of photosensitizer, can procedures significant lack of efficacy in PDT treatment since the generation of reactive oxygen species is directly associated with photons absorption of this photosensitizer. In this paper was studied the Photobleaching kinetics of methylene blue in presence of hydrolyzed collagen. In the investigated conditions, where the collagen matrix simulates the cytoskeleton net, it was demonstrated that the compartmentalization of MB can modulate its photobehavior, how bigger MB concentration in collagen medium, smaller Photobleaching rates. We associated this behavior to methylene blue concentration and by the environmental interaction.