Peptide-Ruthenium Conjugate as an Efficient Photosensitizer for the Inactivation of Multidrug-Resistant Bacteria.

Antimicrobial photodynamic therapy (APDT) has gained increased attention because of its broad spectrum activity and lower likelihood to elicit bacterial resistance. Although many photosensitizers excel at eradicating Gram-positive bacterial infections, they are generally less potent when utilized against Gram-negative bacteria. We hypothesized that conjugating the DNA-targeting, antimicrobial peptide buforin II to a metal-based photosensitizer would result in a potent APDT agent. Herein, we present the synthesis and characterization of a buforin II-[Ru(bpy)3]2+ bioconjugate (1). The submicromolar activity of 1 against the multidrug-resistant strains Escherichia coli AR 0114 and Acinetobacter baumannii Naval-17 indicates strong synergy between the ruthenium complex and buforin II. Our mechanistic studies point to an increased rate of DNA damage by 1 compared to [Ru(bpy)3]2+. These results suggest that conjugating metal complexes to antimicrobial peptides can lead to potent antimicrobial agents.