Potenziale ossidativo delle nanoparticelle di ossidi metallici :uno studio basato su EPR/ spin trapping

In the past years metal oxide nanoparticles (NPs) have gained a considerable interest for several applications. The oxides of transition metal such as CuO are widely used as semiconductors, in magnetic storage media, solar energy transformation, electronics and catalysis. Iron oxides, FeO and F3O4, are currently employed in several biomedical applications; Cr2O3 in green pigment preparation, heterogeneous catalysis, and coating for thermal protection and wear resistance. Exposure to metal oxide NPs may thus occur in the general population or in an occupational context. The micrometric form of some of these oxides does not pose concern regarding human health, however when reduced to nanometric-size their surface reactivity, hence possible toxicity, could increase. To address this issues, a set of industrially relevant oxides of transition metal ions NPs, including CuO, Cr2O3, Fe2O3 and F3O4, has been thoroughly physico-chemically characterized. The potential of these NPs to generate radical species (hydroxyl, and carboxyl radical) and singlet oxygen in aqueous suspension at physiological pH has been investigated in cell-free tests using the spin trapping technique coupled with electron paramagnetic resonance (EPR) spectroscopy. All metal oxides examined are able to generate hydroxyl and carboxyl radical. However Cr2O3 and CuO show an higher reactivity than the iron oxides and are the only able to generate singlet oxygen. The composition of the surrounding environment dramatically affects the free radical release. Carboxyl radical generation was observed only in the presence of ascorbic acid, while 1O2 require the presence of H2O2. Finally, an important finding is that ions leached from the nanoparticles surface play an important role in the generation of free radical species.