Phototoxicity Of Rhodamine Dyes

Rhodamine-123 (R123) and tetrabromo-R123 (TBR) have been evaluated in vitro as potential photosensitizers. R123 localizes selectively in mitochondria of MGH-V1 bladder carcinoma cells exposed to 10 pM R123 for 30 min, and under these conditions R123 is a weak photosensitizes. Incubation with R123 for longer times enhances its phototoxicity, and is associated with a modification of its intracellular localization. TBR is approximately 100 times more phototoxic than R123, as assessed either by 3H-thymidine uptake or vital staining. Actively proliferating cells are more sensitive to either R123 or TBR phototoxicity than are plateau-phase, confluent cultures.