Photodynamic therapy (PDT) is an alternative method of tumour treatment. It is based on a photochemical reaction of a photosensitizer, irradiation, and O(2) which converts to cytotoxic (1)O(2) and other forms of reactive oxygen species (ROS). The comet assay (also called single-cell gel electrophoresis, SCGE) is a sensitive, simple and quantitative technique for detection of DNA damage. In our study we investigated the phototoxicity of the two porphyrin photosensitizers, TPPS4 and MgTPPS4, on HeLa cells. Three different radiation doses and six different concentrations of the photosensitizers were used. Our results show that the DNA of the cells treated with the TPPS(4) and MgTPPS(4) at the concentrations higher than 5 μM was highly fragmented indicating a strong phototoxic effect resulting in a cell apoptosis. On the base of our results we can hypothesize that even the irradiation dose of 1 J cm(-2) is sufficient enough to provoke the DNA fragmentation.

Department of Medical Biophysics Faculty of Medicine and Dentistry Institute of Molecular and Translation Medicine Palacky University Hnevotinska 3 77515 Olomouc Czech Republic

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