Photochemical Properties and Structure–Activity Relationships of RuII Complexes with Pyridylbenzazole Ligands as Promising Anticancer Agents

• Published in: European journal of inorganic chemistry 2017-03, Vol.2017 (12), p.1687-1694
• Main Authors: Havrylyuk, Dmytro, Heidary, David K., Nease, Leona, Parkin, Sean, Glazer, Edith C.
• Format: Article
• Language: English
• Subjects: Anticancer properties; Cancer; Cytotoxicity; DNA damage; Inorganic chemistry; Ligands; Light; Light irradiation; Photochemistry; Photodynamic therapy; Radiation damage; Ruthenium; Ruthenium compounds; Synthesis; Toxicity
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201601450

Ruthenium complexes capable of light‐triggered cytotoxicity are appealing potential prodrugs for photodynamic therapy (PDT) and photoactivated chemotherapy (PACT). Two groups of (polypyridyl)RuII complexes with 2‐(2‐pyridyl)benzazole ligands were synthesized and investigated for their photochemical properties and anticancer activity to compare strained and unstrained systems that are likely to have different biological mechanisms of action. The structure–activity relationship was focused on the benzazole‐core bioisosterism and replacement of coligands in RuII complexes. Strained compounds rapidly ejected the 2‐(2‐pyridyl)benzazole ligand after light irradiation, and possessed strong toxicity in the HL‐60 cell line both under dark and light conditions. In contrast, unstrained RuII complexes were nontoxic in the absence of light, induced cytotoxicity at nanomolar concentrations after light irradiation, and were capable of light‐induced DNA damage. The 90–220‐fold difference in light and dark IC50 values provides a large potential therapeutic window to allow for selective targeting of cells by exposure to light. A structure–activity relationship study, focused on benzazole‐core bioisosterism in RuII complexes, revealed compounds with a potential for photodynamic therapy (PDT) and photoactivated chemotherapy (PACT).