Ruthenium and iridium complexes bearing porphyrin moieties: PDT efficacy against resistant melanoma cells

Porphyrin derivatives present an excellent ability to act as photosensitizers (PS) in photodynamic therapy (PDT). Ruthenium and iridium complexes, mainly containing pyridine ligands, also have been highlighted as potential PS for PDT, due to their photochemical and photophysical properties. The combination of porphyrin derivatives with iridium or ruthenium ions may create singular features and, consequently, improve the PDT effect. In this paper, we report the synthesis, characterization and efficacy of porphyrin derivatives bearing attached ruthenium or iridium terpyridine units to act as PS against resistant melanoma cells (B16F10 cell model). The choice of the porphyrin derivatives to carry out this study was related with their efficacy to generate reactive oxygen species (ROS), the presence of anchoring groups to enable the coordination with ruthenium and iridium metal ions and on the studies of subcellular localization. In the PDT studies, a cell viability decrease was observed in the presence of compounds 4a (ruthenium derivative) and 3b (iridium derivative) at lower concentrations due to the high values of singlet oxygen quantum yield and cellular uptake found. The fluorescence of derivative 3b was observed uniformly dispersed by the cells.