Original Article
Photoinduced electron-transfer mechanisms for radical-enhanced photodynamic therapy mediated by water-soluble decacationic C70 and C84O2 Fullerene Derivatives

https://doi.org/10.1016/j.nano.2012.09.005Get rights and content

Abstract

Fullerenes are promising candidates for photodynamic therapy (PDT). Thus, C70 and novel C84O2 fullerenes were functionalized with and without an additional deca-tertiary ethyleneamino-chain as an electron source, giving rise to two distinct pairs of photosensitizers, the monoadducts LC-17, LC-19 and the bisadducts LC18 and LC-20 to perform PDT in HeLa cells with UVA, blue, green, white and red light. Shorter wavelengths gave more phototoxicity with LC-20 while LC-19 was better at longer wavelengths; the ratio between killing obtained with LC-19 and LC-20 showed an almost perfect linear correlation (R = 0.975) with wavelength. The incorporation of a deca-tertiary amine chain in the C84O2 fullerene gave more PDT killing when excited with shorter wavelengths or in the presence of low ascorbate concentration through higher generation of hydroxyl radicals. Photoactivated C84O2 fullerenes induced apoptosis of HeLa cancer cells, together with mitochondrial and lysosomal damage demonstrated by acridine orange and rhodamine 123 fluorescent probes.

From the Clinical Editor

Photoactivated C70 and C84O2 fullerenes were demonstrated to induce apoptosis of HeLa cancer cells, together with mitochondrial and lysosomal damage, as a function of wavelength. The study is paving the way to future clinical uses of these agents in photodynamic therapy.

Graphical Abstract

Decationically-armed C70 or C84(O2) fullerenes can be excited by UVA, blue, green, white or red light to produce varying amounts of hydroxyl radicals (electron transfer) or singlet oxygen (energy transfer) that can kill cancer cells. Ascorbic acid can potentiate electron transfer but quench singlet oxygen.

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Section snippets

Materials

Reagents consisting of γ-butyrolactone, BF3·Et2O, triethylamine, pyridine, iodomethane, 1,8-diazabicyclo[5,4,0]-undec-7-ene (DBU), tetrabromomethane (CBr4), iodine, trifluoroacetic acid, and L-ascorbate were purchased from Aldrich Chemicals and used without further purification. Malonyl chloride was purchased from TCI America. A C70 sample with a purity of 98.0% was purchased from Term USA, Inc. and a C84O2 sample was provided by Nano-C, Inc. Sodium sulfate was employed as a drying agent.

Synthesis of C70- and C84O2-malonate quaternary ammonium iodide salts

The unmodified fullerenes are not soluble in polar solvents, which demands their chemical modification so they can become suited for biological purposes,24 such as PDT. Accordingly, functional moieties of C70 and C84O2 fullerenes were designed to increase both the water-solubility and provide surface binding interactions with –D-Ala-D-Ala residues of the bacteria cell wall by incorporating multiple H-bondings and positive quaternary ammonium charges. We first synthesized a malonate precursor

Discussion

The phenomenon of wavelength-dependent alteration of PDT mechanisms has not been much reported (if at all). When PDT is performed with LC-20 and shorter wavelengths, higher cell killing is achieved, but LC-19-I3 gives higher killing when used along with longer wavelengths, such as red light. The presence of tertiary amine electron donors predisposes towards better killing after short wavelength excitation. Knowing that high amounts of hydroxyl radical induce the apoptosis of cells31 and that

References (51)

  • P. Agostinis et al.

    Photodynamic therapy of cancer: an update

    CA Cancer J Clin

    (2011)
  • P. Mroz et al.

    Photodynamic therapy with fullerenes

    Photochem Photobiol Sci

    (2007)
  • D.E. Dolmans et al.

    Photodynamic therapy for cancer

    Nat Rev Cancer

    (2003)
  • S.K. Sharma et al.

    Photodynamic therapy with fullerenes in vivo: reality or a dream?

    Nanomedicine

    (2011)
  • J.W. Arbogast et al.

    Photophysical properties of sixty atom carbon molecule (C60)

    J Phys Chem

    (1991)
  • M. Neumaier et al.

    Electron transfer collisions between isolated fullerene dianions and SF6

    J Chem Phys

    (2005)
  • L. Culotta et al.

    Buckyballs: wide open playing field for chemists

    Science

    (1991)
  • Y. Tabata et al.

    Photodynamic effect of polyethylene glycol-modified fullerene on tumor

    Jpn J Cancer Res

    (1997)
  • H. Kawauchi et al.

    Photoinduced charge-separation and charge-recombination processes of fullerene[60] dyads covalently connected with phenothiazine and its trimer

    J Phys Chem A

    (2008)
  • M. Maggini et al.

    Organic, physical and materials photochemistry

  • Y. Araki et al.

    Photoinduced electron transfer between electron donors and fullerenes as unique electron acceptors

  • Y. Doi et al.

    Intracellular uptake and photodynamic activity of water-soluble [60]- and [70]fullerenes incorporated in liposomes

    Chemistry

    (2008)
  • A. Ikeda et al.

    Direct and short-time uptake of [70]fullerene into the cell membrane using an exchange reaction from a [70]fullerene-gamma-cyclodextrin complex and the resulting photodynamic activity

    Chem Commun (Camb)

    (2009)
  • M. Wang et al.

    Synthesis and photodynamic effect of new highly photostable decacationically armed [60]- and [70]fullerene decaiodide monoadducts to target pathogenic bacteria and cancer cells

    J Med Chem

    (2012)
  • R. Koeppe et al.

    Photoinduced charge and energy transfer involving fullerene derivatives

    Photochem Photobiol Sci

    (2006)
  • Cited by (0)

    Funding. This work was supported by NIH grant R01CA137108 to LYC. FFS was supported by CAPES Foundation, Ministry of Education of Brazil, grant number 0310-11-5. TD was supported by an Airlift Research Foundation Extremity Trauma Research Grant (grant 109421) and a Basic Research Grant from the Orthopaedic Trauma Association (grant 2012-16). MRH was supported by NIH grant RO1AI050875.

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