Photosensitizing properties of palladium-tetraphenylporphycene on culturedtumour cells

In this study we describe photokilling properties and effects on the mitoti c index (MI) of cultured HeLa cells induced by palladium(II)-tetraphenylpor phycene (PdTPPo). The drug was synthesized by refluxing tetraphenylporphyce ne (TPPo) and PdCl2 in dimethylformamide, followed by evaporation and purif ication by chromatography. Cells were treated with different concentrations of PdTPPo incorporated into dipalmitoylphosphatidylcholine liposomes, and red light irradiation (lambda > 600 nm) was performed at 21 mW/cm(2). No da rk toxicity was found when the drug was applied under our experimental cond itions. Using lethal (LD100) treatments, cells showed the immediate occurre nce of bubbles on the plasma membrane, whereas homogeneous nuclear condensa tion and loss of cytoplasm appeared 3-24 h later. An increased MI was found 6-8 h after sublethal LD25 and LD40 treatments as well as a high proportio n of abnormal metaphases with altered spindle microtubules. Chromatin conde nsation and fragmentation were observed 8 h after LD75 treatments. These re sults show that in comparison with TPPo, the new sensitizer PdTPPo has more efficient photokilling properties which could be very valuable for the pho todynamic therapy of cancer.