Photodynamic activities of silicon phthalocyanines against achromic M6 melanoma cells and healthy human melanocytes and keratinocytes

Dichlorosilicon phthalocyanine (Cl2SiPc) and bis(tri-n-hexylsiloxy)silicon phthalocyanine (HexSiPc) have been evaluated in vitro as potential, photose nsitizers for photodynamic therapy (PDT) against the human amelanotic melan oma cell line M6. Each photosensitizer is dissolved in a solvent-PBS mixtur e, or entrapped in egg-yolk lecithin Liposomes or in Cremophor EL micelles. The cells are incubated for 1 h with the sensitizer and then irradiated fo r 20 min, 1 h or 2 h (lambda > 480 nm, 10 mW cm(-2)). The photocytotoxic ef fect is dependent on the photosensitizer concentration and the light dose. Higher phototoxicity is observed after an irradiation of 2 h: treatment wit h a solution of photosensitizer (2 x 10(-9) M) leads to 10% (HexSiPc in egg -yolk lecithin liposomes) or 20% (Cl2SiPc in DMF-PBS solution) cell viabili ty. After 1 h incubation and 20 min of light exposure, the photodynamic eff ect is connected with the type of delivery system used. For HexSiPc, lower cell viability is found when this photosensitizer is entrapped in egg-yolk lecithin instead of solvent-PBS or for Cremophor EL micelles with Cl2SiPc. Liposome-delivered HexSiPc leads to lipid damage in M6 cells, illustrated b y an increase of thiobarbituric acid-reacting substances (TBARs), but the c hange is not significant with Cremophor EL. The same is observed for the an tioxidative defences after photodynamic stress. The cells irradiated with H exSiPc entrapped in liposomes display an increase of superoxide dismutase ( SOD) activity and a decrease of glutathione (GSH) level, glutathione peroxi dase (GSHPx) and catalase (Cat) activities. (C) 1999 Elsevier Science S.A. All rights reserved.