EFFECT OF PHOTOSENSITIZER DELIVERY SYSTEM AND IRRADIATION PARAMETERS ON THE EFFICIENCY OF PHOTODYNAMIC THERAPY OF B16 PIGMENTED MELANOMA INMICE

Previous studies (Biolo et al., Photochem. Photobiol. 59, 362-365, 199 4) showed that liposome-delivered Si(IV)-naphthalocyanine (SiNc) photo sensitizes B16 pigmented melanoma subcutaneously transplanted in C57 m ice to the action of 776 nm light. However, the efficacy of the photot reatment was limited by a lack of selectivity of tumor targeting by Si Nc as well as by incomplete necrosis of the neoplastic mass. The prese nt investigations show that the use of a different delivery system (Cr emophor emulsion vs liposomes of dipalmitoylphosphatidylcholine) cause s no significant increase in the selectivity of tumor targeting for th ree injected doses of SiNc (0.5, 1, 2 mg/kg). However, upon 776 mm lig ht irradiation (300 mW/cm(2); 520 J/cm(2)), the delay in the rate of t umor growth was maximal (7-8 days) for the highest naphthalocyanine do se. On the other hand, a remarkable improvement in the tumor response was obtained by inducing an intratumoral temperature increase to 44 de grees C immediately after PDT. The thermal effect appeared to be due t o photoexcitation of melanin by 776 nn light (550 mW/cm(2); 520 J/cm(2 )) and subsequent partial conversion of absorbed energy into heat.