ABSTRACT
Photodynamic therapy (PDT) relies on the generation of highly cytotoxic species upon illumination of a specic molecular agent known as a photosensitizer.1,2 In most cases, the photosensitizer itself does not react with biomolecules, but upon illumination reacts with molecular oxygen to generate actual toxic agents, namely, reactive oxygen species (ROS), which includes singlet oxygen 1O2, superoxide radical O2−•, hydroxyl radical HO•, and hydrogen peroxide H2O2.3 e high yield of production of these species upon illumination with light is the key prerequisite for the ecacy of PDT. Selection of the molecular platform with a set of optimized optical and photochemical properties is usually the rst step in the development of a useful photosensitizer. is step requires knowledge of both photochemical and chemical processes occurring when a photosensitizer interacts with oxygen, as well as properties of the photosensitizer, particularly in its excited state. is chapter provides a concise overview of key photochemical processes involved in the generation of ROS and a survey of photosensitizers commonly used in PDT, together with the discussion of their properties, relevant to ROS generation.
