EFFICIENT PHOTODYNAMIC-ACTION OF VICTORIA BLUE BO AGAINST THE HUMAN LEUKEMIC-CELL LINES K-562 AND TF-1

Photodynamic induced cytotoxicity by Victoria blue BO (VB-BO), merocya nine 540 (MC540), Nile blue A (NB) and 4-tetrasulfonatophenyl-porphyri n (4-TSPP) has been studied on two human leukemic cell lines: K-562 an d TF-1. Cells were incubated with dyes and irradiated with different d oses of white light. Cell survival was assessed by propidium iodide (P I) staining using flow cytometry analysis. Concentrations of 5 x 10(-8 ) M VB-BO were found to kill 75% of cells, and a concentration of 1 X 10(-7) M induced more than 99% of cell killing. To obtain the same cyt otoxic level, the presence of 2.6 x 10(-5) M of MC540 during irradiati on was needed. Under the conditions used, NB was ineffective as a phot osensitizer, although uptake studies showed that this dye was taken by the cells in much greater amounts than any other studied dye. Cell cy cle distribution of TF-I cells, surviving MC540 or VB-BO photosensitiz ation has been studied by flow cytometry analysis after staining with Hoechst 33342 and PI. It was found that cells in G1 phase were slightl y more resistant toward MC540- and VB-BO-mediated photosensitization t han cells in other phases of the cell cycle.