Toxicological Evaluation of a Methylene Blue-Based Photodynamic Water Disinfection Technique

摘要

The photosensitizer Methylene Blue (MB) is widely used in medicine as an antiseptic agent, an antidote in some poisonings, and a photosensitizer in photodynamic therapy. MB treatment of water exposed to light (photodynamic disinfection) is one of the proposed methods for water disinfection. The bactericidal effects of the photosensitizing dye are due to its affinity for bacterial cells. When excited by visible light, the dye molecules react with molecular oxygen and biomolecules, particularly with those of biomembranes, to form a number of short-living active radicals including active forms of oxygen. The radicals oxidize biomolecules, thus disrupting cell functioning and killing the organism. However, the dye itself can be transformed in the photochemical reaction. The degree of its photodestruction and the resulting products would determine the toxicity of a photosensitizer.