Synthesis and Photodynamic
Effect of New Highly Photostable Decacationically Armed [60]- and
[70]Fullerene Decaiodide Monoadducts To Target Pathogenic Bacteria
and Cancer Cells
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Abstract
Novel water-soluble decacationically armed C<sub>60</sub> and C<sub>70</sub> decaiodide monoadducts, C<sub>60</sub>- and C<sub>70</sub>[>M(C<sub>3</sub>N<sub>6</sub><sup>+</sup>C<sub>3</sub>)<sub>2</sub>], were synthesized, characterized, and applied as photosensitizers
and potential nano-PDT agents against pathogenic bacteria and cancer
cells. A high number of cationic charges per fullerene cage and H-bonding
moieties were designed for rapid binding to the anionic residues displayed
on the outer parts of bacterial cell walls. 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 C<sub>70</sub>[>M(C<sub>3</sub>N<sub>6</sub><sup>+</sup>C<sub>3</sub>)<sub>2</sub>] produced
more HO<sup>•</sup> than C<sub>60</sub>[>M(C<sub>3</sub>N<sub>6</sub><sup>+</sup>C<sub>3</sub>)<sub>2</sub>], in addition
to <sup>1</sup>O<sub>2</sub>. This finding offers an explanation of
the preferential killing of Gram-positive and Gram-negative bacteria
by C<sub>60</sub>[>M(C<sub>3</sub>N<sub>6</sub><sup>+</sup>C<sub>3</sub>)<sub>2</sub>] and C<sub>70</sub>[>M(C<sub>3</sub>N<sub>6</sub><sup>+</sup>C<sub>3</sub>)<sub>2</sub>], respectively. The
hypothesis is that <sup>1</sup>O<sub>2</sub> 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<sup>•</sup> to cause real damage
