Development of ruthenium(II) complexes as topical antibiotics against methicillin resistant Staphylococcus aureus

A series of ruthenium(II) bis(2,2'-bipyridyl) complexes containing N-phenyl-substituted diazafluorenes (Ru-C1, Ru-C6, Ru-C7 and Ru-F) was synthesized and their potential antibacterial activity against methicillin resistant Staphylococcus aureus (MRSA) was investigated. The Ru-C7 complex showed significant improvement in both minimum inhibitory concentration (MIC, 6.25 mu g mL(-1)) and minimum bactericidal concentration (MBC, 25 mu g mL(-1)) towards MRSA when compared with those of methicillin (positive control) (MIC = 25 mu g mL(-1) and MBC = 100 mu g mL(-1)). The Ru-C7 complex possessed much stronger antibacterial effects than the Ru-C6 complex (MIC, 25 mu g mL(-1), MBC, > 100 mu g mL(-1)). Both Ru-C6 and Ru-C7 complexes were also demonstrated to be biologically safe when tested on normal human skin keratinocytes.