Figure 5From: Theoretical aspects and modelling of cellular decision making, cell killing and information-processing in photodynamic therapy of cancerSinglet Oxygen. Singlet Oxygen is the most important cytotoxic agent generated during PDT(it decays after photo irradiation time). Singlet oxygen is produced during PDT via a triplet-triplet annihilation reaction between ground state molecular oxygen (which is in a triplet state) and the excited triplet state of the photosensitizer.Back to article page