Effect of bleaching of porphyrin sensitizers during photodynamic therapy.
Cells of the line NHIK 3025 were incubated with the tumor-localizing porphyrin preparation DHE (Photofrin II). Exposure of light within the porphyrin absorption spectrum resulted in a change of the fluorescence spectra indicative of a movement of porphyrins from binding sites on proteins to more lipid environments, a degradation of the porphyrins in the cells without any significant formation of new porphyrin species. The photodegradation of the porphyrins resulted in a reduced yield of inactivation of cells per incident photon. Several independent estimations indicate that bleaching may play a role in clinical situations.
D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D017324:Hematoporphyrin Derivative; D006415:Hematoporphyrins / Q000378:metabolism / Q000528:radiation effects*; D006801:Humans; D066298:In Vitro Techniques; D050356:Lipid Metabolism; D010777:Photochemistry; D011506:Proteins / Q000378:metabolism; D013050:Spectrometry, Fluorescence
D006415:Hematoporphyrins; D011506:Proteins; D017324:Hematoporphyrin Derivative