Cytotoxicity of photosensitizers camphorquinone and 9-fluorenone with visible light irradiation on a human submandibular-duct cell line in vitro

The cytotoxic effect of two types of photosensitizers (camphorquinone, CQ, a widely used aliphatic type and 9-fluorenone, 9F, an aromatic type) in the presence of 2-dimethylaminoethyl methacrylate (DM) as a reducing agent with exposure to visible light (350–550 nm) was examined in a human cell line. Cytotoxicity was evaluated in terms of the percentage of cell survival, and the production of reactive oxygen in living single cells was measured with an adherent cell analysis and sorting laser cytometer and a peroxide indicator. The amount of reactive oxygen generated in the cells irradiated in the 9F (1 mM–3 min) system was about 9-fold greater than under the same conditions in the CQ system. Similarly, the decrease in cell survival in the 9F system was about 10-fold greater than in the CQ. Both the production of reactive oxygen in the cells and the decrease in cell survival paralleled the concentration of photosensitizers and the irradiation time. Although the cell-damaging effects with the CQ system were mild, at a higher dose (10 mM) and longer irradiation time (24 min) it produced cell survival equal to that in the 9F (1 mM–3 min) system. These results suggest that in the case of irradiated photosensitizer systems, 9F was much more damaging to the cells than CQ, which damage probably occurred via free radicals involving reactive oxygen generation.