Fig. 2

Viability of SK-ChA-1 cells after ZnPC-ITL-PDT. SK-ChA-1 cells were incubated with 500 μM ZnPC-ITLs (final lipid concentration) and kept in the dark (ITL) or were irradiated with 50-mW (ITL 50) or 500-mW (ITL 500) laser light at a cumulative radiant exposure of 15 J/cm². Metabolic activity and the extent of cell death were assessed after 24 hours with a WST-1 assay (a) and SRB assay (b), respectively. Data were normalized to control cells that were set at 100 %. Alternatively, the mode of cell death was assessed 90 minutes (c) or 24 hours (d) post-PDT by flow cytometry. For this purpose, cells were stained with Alexa Fluor 488-conjugated annexin V and propidium iodide (PI). Necrotic cells are represented in red (PI-positive), apoptotic cells are shown in green (PI-negative, annexin V-positive), and healthy cells are represented in white (PI-negative, annexin V-negative). Values are presented as mean + SD for n = 6 per group. Readers are referred to section Statistical analysis for the significance of the statistical symbols