Metal based complexes have been used lately as anti-cancer agents due to their ability to bind DNA and thereby affecting gene expression. Of these metal complexes, ruthenium based drugs have recently gained interest as potential antitumor and antimetastatic agents. Photodynamic therapy is a valuable technique aimed at alleviating drug resistance and side effects associated with conventional chemotherapy. The present study aims at studying the biological activity of a series of photoactivatable ruthenium(II) polyimine complexes. Three sterically strained ruthenium complexes were synthesized and fully characterized: ruthenium(bipyridine)2(2,9-dimethylphenanthroline)Cl2 (complex 1); ruthenium(bipyridine)2(bathocuproine)Cl2 (complex 2); ruthenium(bipyridine)2 (2,9-diphenylphenanthroline)Cl2 (complex 3); along with a control ruthenium(bipyridine)2(1,10-phenanthroline)Cl2 (complex 4). The photochemical ligand ejection from theses complexes was evaluated using NMR studies. Cell viability assay (WST-1) was performed on triple-negative breast cancer cell line (MDA) and murine melanoma cell line (B16) to determine the cytotoxic effect of the complexes with and without light activation. While complex 4 was biologically inert, treatment with complex 1 showed a phototoxicity index (PI; IC50 dark/IC50 light) of about 3 on MDA cells. No significant effect on B16 cells was observed. For complex 2, PI was found to be around 10 on MDA and about 4000 on B16 cells. Notably, complex 2 exhibited an IC50 of 12 nM on MDA cells upon light activation, which is several order of magnitude lower than cisplatin. Complex 3 showed a PI of about 150 on MDA and 100 on B16 cells. Our results suggest that both complex 2 and complex 3 are promising photodynamic agents for cancer therapy.

Photodynamic therapy of cancer using sterically strained ruthenium complexes

253rd National Meeting (2017)

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