Figure 3.

Mechanism of action of PDT. Reactive oxygen species produced by PDT after the interaction of light, photosensitizer, and oxygen mediate cellular damage by multiple mechanisms. The exact proportion of damage caused by each mechanism is dependent on the energy dose delivered (high doses causing more necrosis, lower doses cause apoptosis and ischemia, in addition to necrosis)⁵⁶ as well as the photosensitizer used (sensitizers accumulating in the mitochondria and lysosomes are more likely to initiate apoptosis, whereas those accumulating in the cell membranes cause more necrosis).³³