Photodynamic therapy kills cells which have taken up sensitizing molecules that produce reactive oxygen species when they absorb light.  We have tested the toxicity of a series of porphyrin derivatives in the light and in the dark.  Each was tested on a normal fibroblast line, which was most sensitive, and 3 tumor-derived lines, which required higher doses for photoxicity.  The porphyrins were modified with side chains that affect their hydrophobicity and solubility in water.  Distribution coefficients (logD) between octanol and buffer were determined for each derivative.  In general, increasing logD (hydrophobicity) correlated with greater photoxicity at lower doses.  However, dark toxicity also increased with logD.  Several of the derivatives show promise for in vivo testing- they are highly phototoxic on tumor-derived cells at low concentration (<10 micromolar) while showing low dark toxicity at these concentrations.  This data will be used to design derivatives with improved properties for photodynamic therapy.

Phototoxicity of modified porphyrins for photodynamic therapy

243rd National Meeting (2012)

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