Decacationic [70]Fullerene Approach for Efficient Photokilling of Infectious Bacteria and Cancer Cells

Photodynamic inactivation of pathogenic bacteria and cancer cells by novel water-soluble decacationic fullerene monoadducts, C₆₀[>M(C₃N₆⁺C₃)₂] and C₇₀[>M(C₃N₆⁺C₃)₂], were investigated. In the presence of a high number of electron-donating iodide anions as parts of quaternary ammonium salts in the arm region, we found that C₇₀[>M(C₃N₆⁺C₃)₂] produced more highly reactive HO^• radical than C₆₀[>M(C₃N₆⁺C₃)₂], in addition to singlet oxygen (¹O₂). This finding offers an explanation of the preferential killing of Gram-positive and Gram-negative bacteria by C₆₀[>M(C₃N₆⁺C₃)₂] and C₇₀[>M(C3N₆⁺C₃)₂], respectively. The hypothesis is that ¹O₂ can diffuse more easily into porous cell walls of Gram-positive bacteria to reach sensitive sites, while the less permeable Gram-negative bacterial cell wall needs the more reactive HO^• to cause real damage.