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The aim of this study was analysis of DNA damage in the cell line of the human melanoma G361 after photodynamic therapy (PDT) by comet assay. Photodynamic therapy is based on cytotoxic action of sensitizers (10 µM ZnTPPS4 fixed into 1 mM cyclodextrin hpβCD) and light with a suitable wavelength. Single-cell gel electrophoresis (SCGE, comet assay) is a rapid and sensitive method for detecting DNA strand breaks at the level of single cells. Great amount of DNA damage was detected with the dose of irradiation of 0.1; 0.5 J and 2.5 J.cm-2. Only radiation dose of visible light in the presence of sensitizers can induce DNA breaks of tumour cells. Cells with DNA damage appear as fluorescent comets with tails of DNA fragmentation. In contrast, cells with undamage DNA appear as round spots, because their intact DNA does not migrate out of the cell.

The objective of our work was to describe the photophysical properties (absorption and fluorescence) of the sensitizers TPPS4, ZnTPPS4 a PdTPPS4 and above all the complexes of these sensitizers with cyclodextrin carriers HP-α-CD, HP-β-CD and HP-γ-CD (2–hydroxypropyl-α, β, γ-cyclodextrin) in a suitable environment for the cultivation of cancerous cell lines, and to determine the optimal radioactive conditions for maximizing photodynamic effects in cancerous cells.