Comparison of sensitizers by detecting reactive oxygen species after photodynamic reaction in vitro

The production of reactive oxygen species (ROS) has a crucial effect on the result of photodynamic therapy (PDT). Because of this fact, we examined the ROS formation by means of three porphyrin sensitizers (TPPS4, ZnTPPS4 and PdTPPS4) and compared their effectivity for induction of cell death in the G361 (human melanoma) cell line. The porphyrins used are very efficient water-soluble aromatic dyes with a potential application in photomedicine and have a high tendency to accumulate in the membranes of intracellular organelles such as lysosomes and mitochondria. Interaction between the triplet excited state of the sensitizer and molecular oxygen leads to the production singlet oxygen and other reactive oxygen species to induce cell death. Production of ROS was investigated by molecular probe CM-H2DCFDA. Our results demonstrated that ZnTPPS4 induces the highest ROS production in the cell line compared to TPPS4 and PdTPPS4 at concentrations of 1, 10, and 100 μM and light dose of 1 J cm−2. We also observed a consequence between ROS production and cell survival. In conclusion, these results demonstrate that photodynamic effect depends on sensitizer type, its concentration and light dose.