Sonodynamic effects of protoporphyrin IX disodium salt on Ehrlich ascetic tumor cells

The cytotoxic effect of protoporphyrin IX disodium salt (PPIX) on isolated Ehrlich ascetic tumor (EAT) cells induced by ultrasound exposure was investigated. Tumor cells suspended in air-saturated phosphate buffer solution (PBS, pH 7.2) were exposed to ultrasound at 2.2 MHz for up to 60 s in the presence and absence of PPIX. The viability of cells was determined by a trypan blue exclusion test. The morphological changes of cells in SDT were observed by scanning electron microscope (SEM). And the sub-cellular localization of PPIX in EAT cells was detected by confocal laser scanning microscopy (CLSM). The ultrasonically-induced cell damage increased as PPIX concentration increased, while no cell damage was observed with PPIX alone. CLSM observation revealed that the fluorescence of PPIX and rhodamine 123 (mitochondrial probe) overlapped very well in the cytoplasm. The results indicate that PPIX could enhance the ultrasonically-induced cell damage and mitochondria may play an important role during sonodynamically induced cytotoxicity.