The scientific basis of PDT

Harry Moseley

doi:10.1117/12.544869

12 December 2003 The scientific basis of PDT

Harry Moseley

Proceedings Volume 5287, Laser Florence 2002: A Window on the Laser Medicine World; (2003) https://doi.org/10.1117/12.544869
Event: Laser Florence 2002: A Window on the Laser Medicine World, 2002, Florence, Italy

Abstract

Photodynamic therapy (PDT) involves the use of a photoactive drug (photosensitizer) and light. Upon absorption of light, the photosensitizer initiates oxygen-mediated chemical reactions that lead to the direct or indirect production of species such as singlet oxygen that cause cell death. The reaction of the cytotoxic species with subcellular organelles and molecules such as proteins and DNA lead to apoptosis or necrosis of the cells hosting the photosensitizer. Preferential accumulation of photosensitizer in cancer cells means that, as an anti-cancer treatment, this has the potential to kill selectively the tumor cells while leaving healthy cells undamaged. Photodynamic mechanisms proceed from the first excited singlet state (S1) via either Type I or Type II mechanism. A Type I reaction involves the photosensitizer losing an electron to form a radical cation, typically reacting with oxygen to form superoxide and hydroxyl radicals. In a Type II reaction, the sensitizer relaxes into the first excited triplet state (T1) which interacts with oxygen to form singlet oxygen. The species produced are very reactive and can cause cell death by either apoptosis or necrosis. Cells membranes are a primary site of action. Functional impairment of mitochondria is also observed.

Citation Download Citation

Harry Moseley "The scientific basis of PDT", Proc. SPIE 5287, Laser Florence 2002: A Window on the Laser Medicine World, (12 December 2003); https://doi.org/10.1117/12.544869

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