Toxic and Phototoxic Effects of Tetraphenylporphinesulphonate and Haematoporphyrin Derivative in Vitro

Summary

The toxic and phototoxic effects of tetraphenylporphinesulphonate (TPPS₄) and haematoporphyrin derivative (HpD) have been examined in vitro. TPPS₄ was found to have less dark toxicity to the cells than HpD as measured by inhibition of cell multiplication and colony formation at comparable extracellular concentrations. TPPS₄ was also less effective than was HpD in photoinactivating NHIK 3025 cells by more than a factor 2 which should be expected on the basis of cellular uptake. Spectrofluorometric data suggest that HpD in cells interacts more with lipids than TPPS₄. This might explain the large photosensitizing effect of HpD compared to TPPS₄ since the lifetime of singlet oxygen is about a factor of 10 longer in a lipid environment than in an aqueous environment.

The uptake of TPPS₄ and HpD by cancer cells in vitro does not correlate with previous in vivo data, indicating retention of TPPS₄ in the tumour stroma. This makes in vitro/in vivo extrapolation difficult with regard to the use of TPPS₄ as an agent for photodynamic therapy.

• tetraphenylporphinesulphonate
• haematoporphyrin derivative
• cellular uptake of photosensitizers
• cellular photoinactivation
• photodynamic sensitizers