Effects of low level light therapy and NO on light irradiation efficacy of ruthenium-phthalocyanine complexes as a function of radical species formation. (Conference Presentation)

Different kinds of light irradiation has been used for several decades in clinical therapy. Among them low level light therapy (LLLT) is found to modulate signaling pathways, via production of ROS, ATP, Ca+2 and NO, which could be an important tool in a combination with other kind of therapy1. We have found some benefits of the combined LLLT and photodynamic therapy (PDT) using a metal-based compound, as an alternative treatment that combines photosensitizer, reactive oxygen and nitrogen species (RONS) and light irradiation against cancer2. Two types of ruthenium compounds were used in those studies ([Ru(Pc)], Pc = phthalocyanine) (I) and [RuNO(Pc)NO2] (II). Herein, we present the synthesis, characterization and photobiological properties of both ruthenium complexes. Both complexes present UV-Vis spectral peaks in 650 nm region. Light irradiation on the Q-band using (II) 0,5 µM provokes a decrease in the percentage of viable cells in human melanoma (A431) around 40 % in comparison to (I). We have hypothesized that those results are coming from the synergistic effect between singlet oxygen and nitric oxide. Similar experiment performed with the combination of PDT (660 nm) +LLLT (850 nm) induced more active photocytotoxicity of (I) and (II), which were interpreted as a function of the increase of cell metabolism and consequently increase of the uptake of the ruthenium-phthalocyanine compounds. The use of metal-based photosensitizers and combination of light therapy described in this work maybe constitutes in an advance in the field of clinical work related to photodynamic therapy.