Photosensitizing properties of palladium-tetraphenylporphycene on cultured tumour cells

In this study we describe photokilling properties and effects on the mitotic index (MI) of cultured HeLa cells induced by palladium(II)-tetraphenylporphycene (PdTPPo). The drug was synthesized by refluxing tetraphenylporphycene (TPPo) and PdCl₂ in dimethylformamide, followed by evaporation and purification by chromatography. Cells were treated with different concentrations of PdTPPo incorporated into dipalmitoylphosphatidylcholine liposomes, and red light irradiation (λ > 600 nm) was performed at 21 mW/cm². No dark toxicity was found when the drug was applied under our experimental conditions. Using lethal (LD₁₀₀) treatments, cells showed the immediate occurrence of bubbles on the plasma membrane, whereas homogeneous nuclear condensation 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 proportion of abnormal metaphases with altered spindle microtubules. Chromatin condensation and fragmentation were observed 8 h after LD₇₅ treatments. These results show that in comparison with TPPo, the new sensitizer PdTPPo has more efficient photokilling properties which could be very valuable for the photodynamic therapy of cancer.