Mechanisms in photodynamic therapy photosensitizers and cellular localization on K562 cells

This paper proposes to explore the pattern of lymphoblastic cell line K562 cells death, the effects on their cell cycle induced by 5,10,15,20-tetra-p-sulphonato-phenyl-porphyrin-based photodynamic therapy (TS4PP-PDT). Flow cytometry combined with Annexin V-FITC/PI labeling was used to detect the pattern of K562 cells' death induced by TS4PP-PDT. These effects frequently lead to induction of apoptosis by the mitochondrial pathway involving caspases. The transmission electron microscope (TEM) and confocal laser scanning microscopy (CLSM) were used to detect the localization and time-biodistribution of sensitizers in the cells. After 1h of TS4PP administration, the sensitizer shows a non-uniform distribution, following that after 4h of administration, the sensitizer to be localized in some cellular targets and an increased fluorescence intensity is being detected. After 8 h and 24 h post-administration, the sensitizer is released from the cells and the light-irradiation (He-Ne laser, lambda=632.8 nm) could start. Immediately after irradiation, many typical apoptotic bodies were seen in the cells treated. Most of the cells treated were necrotic at 24 hours following irradiation.