Antimicrobial photodynamic therapy with decacationic monoadducts and bisadducts of [70]fullerene: In vitro and in vivo studies

Background: Antimicrobial photodynamic therapy uses photosensitizers designed to bind to microorganisms and generate reactive oxygen species when illuminated with visible light. Materials & methods: We synthesized a highly water-soluble [70]fullerene monoadduct, C₇₀[>M(C ₃N₆⁺C₃)₂]-(I ^-)₁₀ (LC17), and bisadduct, C₇₀[>M(C ₃N₆⁺C₃)₂][>M(C ₃N₆C₃)₂] (LC18), both with a well-defined decacationic quaternary ammonium iodide moiety with ten positive charges per C₇₀ to give water solubility and bacterial binding. We determined the antimicrobial effects against human pathogens, Gram-positive (Staphylococcus aureus) and Gram-negative species (Escherichia coli and Acinetobacter baumannii) when activated by UVA or white light. Results: White light was more effective with LC17, while UVA light was more effective with LC18. Both compounds were effective in a mouse model of Gram-negative third-degree burn infections determined by bioluminescence imaging. Discussion & conclusion: We propose that the attachment of an additional deca(tertiary-ethylenylamino)malonate arm to C₇₀ allowed the moiety to act as a potent electron donor and increased the generation yield of hydroxyl radicals under UVA illumination.