Photodynamic therapy with a new photosensitizing agent

Objective: The aim of this study was to investigate the cytotoxicity of octal-bromide zinc phthalocyanine (ZnPcBr8) before and after irradiation with a low-power laser (AsGaAl) and analyze the effects of photodynamic therapy (PDT) on the nucleus of L929 cells. Background Data: One of the most recent and promising applications of phthalocyanine in medicine is in the detection and cure of tumors. We studied the ZnPcBr8 in agreement with the development of new photosensitizing agents for curing tumors. Methods: L929 cells were cultivated at standard conditions, incubated with ZnPcBr8 for 1 h at different concentrations, irradiated with a semiconductor laser, and incubated in MEM medium for 1, 12, or 24 h. Cells were analyzed using the 3( 4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) technique and fluorescence microscopy. Results: The results demonstrated that ZnPcBr8 at 1 mu M was the most effective concentration for PDT, with a decrease of 63% after 1 h, 99% after 12 h, and 100% after 24 h in relation to the control group. The fluorescence microscopy results showed that ZnPcBr8 was localized in the perinuclear region when analyzed 1 h after incubation. Nucleus staining with DAPI made it possible to observe that nuclear fragmentation occurred 24 h after PDT, cytoplasm retraction at 1, 12, and 24 h after PDT, and vacuoles along the cytoplasm at 12 and 24 h after PDT. Conclusion: According to the results obtained in this study, L929 cell death caused by PDT with ZnPcBr8 possesses characteristics of apoptosis mediated by the mitochondria, due to the decrease in cells viability, the subcellular localization, and the photodamage found.