Spectroscopic and Photophysical Properties of a Highly Derivatized C60 Fullerol

Authors

  • B. Vileno,

    1. Institute of Physics of Complex Matter, Ecole Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
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  • P. R. Marcoux,

    1. Institute of Physics of Complex Matter, Ecole Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
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  • M. Lekka,

    1. Institute of Physics of Complex Matter, Ecole Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
    2. The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, PL-31–342 Kraków, Poland
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  • A. Sienkiewicz,

    1. Institute of Physics of Complex Matter, Ecole Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
    2. Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, PL-02-668 Warsaw, Poland
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  • T. Fehér,

    1. Institute of Physics of Complex Matter, Ecole Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
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  • L. Forró

    1. Institute of Physics of Complex Matter, Ecole Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
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  • The authors are very thankful to Nicolas Xanthopoulos (Institut des Matériaux, Ecole Polytechnique Fédérale de Lausanne) for performing XPS measurements. Dr. Marc Adrian is also acknowledged for performing cryoelectron microscopy. Joao Bruno Livramento (Laboratoire de Chimie Inorganique et Bioinorganique, Ecole Polytechnique Fédérale de Lausanne) is gratefully acknowledged for helpful discussion and Karl–Fischer analysis. B.V. thanks Claudia Clopath and Sylvain Lecoultre (both from Ecole Polytechnique Fédérale de Lausanne) for their assistance with the ESR experiments. This work was also partly supported by grant No. G1MA_CI_2002_4017 (CEPHEUS) of the European Commission (A.S.) and by the NANOTEMP European Research Network. We also thank Dr. Alessia Pica from the Service de Radio-Oncologie, Centre Hospitalier Universitaire de Lausanne, for providing the glioblastoma cells for this study.

Abstract

Hydroxylated C60 molecules, also called fullerols, are a class of water-soluble fullerenes. Here we report the synthesis in acidic conditions of a highly derivatized fullerol (up to 36 carbons per C60 are oxidized). Spectroscopic investigations (X-ray photoelectron spectroscopy and infrared absorption) highlight the coexistence of both acidic and basic forms for the hydroxyl addends of derivatized C60. pH titrimetry reveals that, at millimolar concentrations, only ten protons per fullerol molecule are labile. Such a low value, as compared to 36 hydroxyl groups, is explained by the formation of clusters. A UV-vis absorption study performed over a large range of concentrations also points to the aggregation phenomenon. Moreover, this study shows that the clusters of fullerols appear at relatively low (micromolar) concentrations. An electron spin resonance (ESR) study, based on the attack of singlet oxygen (1Δg) on 2,2,6,6-tetramethyl-4-piperidinol (TMP-OH), has proved the potential of hydroxylated C60 for performing efficient generation of singlet oxygen in aqueous solution. ESR measurements, which allow detection and quantification of 1Δg, have also revealed the generation of reactive oxygen species (ROS). The yield of generation of 1Δg and ROS is strongly correlated to the concentration of fullerol, thus also pointing to the aggregation of fullerol molecules. Exposing glioblastoma cells to oxidative stress in the presence of hydroxylated C60 and visible light has also been performed. Atomic force microscopy is used to monitor the relevant diminishment of the Young's modulus values for cells exposed to the oxidative stress. These results point to a possible application field of fullerols for performing bio-oxidations.

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