Evaluation of diethyl-3-3'-(9,10-anthracenediyl)bis acrylate as a probe for singlet oxygen formation during photodynamic therapy.

The cell-permeable anthracene analog diethyl-3-3'-(9,10-anthracenediyl)bis acrylate (DADB) was recently identified as a highly selective probe for singlet oxygen ((1)O(2)). Now, we show that DADB can be used to monitor (1)O(2) formation in cell culture during photodynamic therapy. An atypical property of DADB is that fluorescence emission is decreased upon oxidation. Using photosensitizers that target specific organelles, we determined that DADB could detect (1)O(2) whether formed in ER, mitochondria or lysosomes. DADB fluorescence was not, however, significantly altered when the photosensitizing agent was the palladium bacteriopheophorbide termed WST11, an agent reported to produce mainly oxygen radicals upon irradiation in an aqueous environment, whereas singlet oxygen was formed in organic solvents.