Water-soluble inclusion complex of fullerene with γ-cyclodextrin polymer for photodynamic therapy

A stable aqueous inclusion complex of fullerene (C60) with macromolecules (C60 concentration as high as 3 × 10^-4 mol L^-1) was achieved by a one-step strategy using γ-cyclodextrin polymer (γ-CDP). The inclusion complex of C60 with γ-CDP (C60-γ-CDP) was characterized by ultraviolet-visible, Raman and ¹H-NMR spectroscopies, powder X-ray diffraction analysis, and thermogravimetric analysis. The supramolecular interactions and the equilibrium constant for a 1 : 2 (C60 : CD unit in γ-CDP) complex of C60 with γ-CDP were studied. Under ultraviolet A (UVA) irradiation C60-γ-CDP in water could generate singlet oxygen, which was detected by electron paramagnetic resonance spectroscopy. We also evaluated the cytotoxicities of C60-γ-CDP, and investigated the phototoxicity of C60-γ-CDP and pristine C60 toward B16-F10 melanoma cells. The cell viability test showed that C60-γ-CDP had a significantly higher photodynamic ability than that of the pristine C60 under UVA irradiation. This work demonstrated both a CDP-functionalized strategy for enhancing the water-solubility and phototoxicity of fullerenes for applications in cancer photodynamic therapy, as well as remediating the negative biological effects of pristine fullerenes.