Photodynamic therapy (PDT) is a non-invasive therapeutic modality used in a
various number of diseases and cancer. It involves the systemic or topic
administration of a photosensitizer, followed by irradiation with light. The
activated photosensitizer converts oxygen to singlet oxygen and/or reactive oxygen
species (ROS) which lead to cell death and tissue necrosis. One aim of PDT
research is the discovery of new photosensitizers possessing minimal dark
cytotoxicity, high photodynamic properties, improved pharmacokinetics,
preferential retention in diseased instead of healthy tissues, chemical stability and a
good cellular uptake .We recently focused our efforts on pheophorbide a (Pba), a chlorophyll derivative.
Pba is characterized by a stronger absorption between 650-700 nm, in the tissuepenetrating
wavelength range. For in vivo applications the capacity of the
photosensitiser to reach in the diseased tissues becomes critical, in particular when
a large peritoneal area is interested as occurring in carcinomatosis and
sarcomatosis. To improve the pharmacokinetic and the activity of the photosensitizer we
conjugated Pba to polyethylene glycol (PEG). In vivo the pharmacokinetic analysis performed on living female C57/BL6 mice
bearing a subcutaneous melanoma mass, showed that injected mPEG-Pba
distributes all over the body, with an higher uptake in the tumor respect to free Pba.
Moreover, preliminary data suggest that PEG-Pba in mice bearing B78-H1
amelanotic melanoma reduces the tumor growth after light activation in
comparison with Pba.
