Photodynamic therapy (PDT) uses the action of visible, low energetic light on a photosensitizer to activate its cytotoxic potential in a target tissue. PDT is a selective treatment modality since the photosensitizer shows preferential accumulation in target (e.g., tumor) cells and the light application can be restricted to the treatment area. By light activation, the photosensitizer forms cytotoxic compounds, mainly reactive oxygen species (ROS), thus destroying the target. The emission of fluorescence light is employed in fluorescence diagnosis for tumor diagnosis and fluorescence-guided surgical resection. PDT is applied for malignant and several nonmalignant diseases.
In 1904, the term “photodynamic” was coined for light-induced cytotoxic action and fluorescence of a photosensitizer. Modern PDT started in the 1970s with the investigation and usage of hematoporphyrin...