Fig. 6.

An illustration of the effector mechanism in photodynamic therapy. 1) Activation of the photosensitizer by external light of a specific wavelength results in the singlet state, which is followed by the creation of reactive oxygen species (ROS), which is the main cause of the apoptosis of tumor cells. 2) Photodynamic therapy activates the immune system, releasing inflammatory mediators like IL-6, IL-1, and TNF-alpha, heat shock protein (HSP), and DAMPs (Damage Associated Molecular Patterns), which cause tumor cells to die