Lasers in Medical Science

, Volume 24, Issue 2, pp 259–268 | Cite as

Photophysics and photochemistry of photodynamic therapy: fundamental aspects

  • K. Plaetzer
  • B. Krammer
  • J. Berlanda
  • F. Berr
  • T. Kiesslich
Review Article


Photodynamic therapy (PDT) is a treatment modality for cancer and various other diseases. The clinical protocol covers the illumination of target cells (or tissue), which have been loaded with a photoactive drug (photosensitizer). In this review we describe the photophysical and primary photochemical processes that occur during PDT. Interaction of light with tissue results in attenuation of the incident light energy due to reflectance, absorption, scattering, and refraction. Refraction and reflection are reduced by perpendicular light application, whereas absorption can be minimized by the choice of a photosensitizer that absorbs in the far red region of the electromagnetic spectrum. Interaction of light and the photosensitizer can result in degradation, modification or relocalization of the drug, which differently affect the effectiveness of PDT. Photodynamic therapy itself, however, employs the light-induced chemical reactions of the activated photosensitizer (triplet state), resulting in the production of various reactive oxygen species, amongst them singlet oxygen as the primary photochemical product. Based on these considerations, the properties of an ideal photosensitizer for PDT are discussed. According to the clinical experience with PDT, it is proposed that the innovative concept of PDT is most successfully implemented into the mainstream of anticancer therapies by following an application-, i.e. tumor-centered approach with a focus on the actual clinical requirements of the respective tumor type.


Photodynamic therapy Photophysics Photochemistry Photosensitizer Singlet oxygen 


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Copyright information

© Springer-Verlag London Limited 2008

Authors and Affiliations

  • K. Plaetzer
    • 1
  • B. Krammer
    • 1
  • J. Berlanda
    • 1
  • F. Berr
    • 2
  • T. Kiesslich
    • 2
  1. 1.Department of Molecular BiologyUniversity of SalzburgSalzburgAustria
  2. 2.University Hospital of Internal Medicine IParacelsus Medical University and SALKSalzburgAustria

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