Fotogeração de espécies reativas de oxigênio induzida por fulerenos e derivados: um estudo por ressonância paramagnética eletrônica e captura de spins

Abstract

The physical and chemical properties of fullerenes have attracted considerable interest since C60 became available in macroscopic quantities some decades ago. Fullerene derivatives have been applied in several areas, from the construction of photovoltaic cells to biomedicine. The functionalization of fullerenes modifies their characteristics, leading to molecules with novel and often more interesting properties. The photophysical properties of new fullerene derivatives were studied by electron paramagnetic resonance (EPR) using the spin trapping technique, which allows the indirect measurement of free radical generation. It was shown that highly cytotoxic reactive oxygen species (ROS) are efficiently produced by these compounds through photosensitization. Using a calibration curve with stable radicals, it was possible to quantify the generation of ROS for each derivative and compare them with pure C60. Moreover, a kinetic model was proposed toexplain the time evolution of radical production and confirms that the radical produced preferably by fullerenes is singlet oxygen. The results suggest that fullerenes and their derivatives are potential candidates for the role of photosensitizers in photodynamic therapy (PDT).