Antibacterial and antibiofilm activity of ruthenium polypyridine complex against Staphylococcus strains

This study reports the synthesis of a new polypyridine ruthenium(II) complex, [Ru(anth)₃]²⁺, which generates singlet oxygen (Φ_Δ = 0.98) and binds DNA (K_b = 9.8 × 10⁴ M^-1), leading to bacterial damage. The compound exhibited minimum inhibitory concentrations (MICs) of 31.25 µg mL^-1 against S. aureus ATCC 700698 and S. epidermidis ATCC 35984, and 125 µg mL^-1 against S. aureus ATCC 25923 and S. epidermidis ATCC 12228. The compound showed synergistic effects with ampicillin and additive effects with tetracycline. The complex significantly reduced biofilm biomass, viable cell counts, and metabolic activity. Scanning electron and confocal laser microscopy confirmed surface disruption and reduced viability. Gel electrophoresis indicated light-induced DNA photocleavage. Cytotoxicity in L929 fibroblasts was observed only above 125 µg mL^-1. These findings suggest that [Ru(anth)₃]²⁺ is a promising antimicrobial agent with multi-target activity, supporting its potential for antimicrobial drug development.