Towards the Development of Antioxidant Cerium Oxide Nanoparticles for Biomedical Applications: Controlling the Properties by Tuning Synthesis Conditions.

Noemi Gallucci,Irene Russo Krauss,Daria Maria Monti,Luigi Paduano,Giuseppe Vitiello,Alessandro Vergara,Rocco Di Girolamo,Oreste Tarallo,Paola Imbimbo

doi:10.3390/nano11020542

Abstract

In this work CeO2 nanoparticles (CeO2-NPs) were synthesized through the thermal decomposition of Ce(NO3)3·6H2O, using as capping agents either octylamine or oleylamine, to evaluate the effect of alkyl chain length, an issue at 150 °C, in the case of octylamine and at 150 and 250 °C, in the case of oleylamine, to evaluate the effect of the temperature on NPs properties. All the nanoparticles were extensively characterized by a multidisciplinary approach, such as wide-angle X-ray diffraction, transmission electron microscopy, dynamic light scattering, UV-Vis, fluorescence, Raman and FTIR spectroscopies. The analysis of the experimental data shows that the capping agent nature and the synthesis temperature affect nanoparticle properties including size, morphology, aggregation and Ce3+/Ce4+ ratio. Such issues have not been discussed yet, at the best of our knowledge, in the literature. Notably, CeO2-NPs synthesized in the presence of oleylamine at 250 °C showed no tendency to aggregation and we made them water-soluble through a further coating with sodium oleate. The obtained nanoparticles show a less tendency to clustering forming stable aggregates (ranging between 14 and 22 nm) of few NPs. These were tested for biocompatibility and ROS inhibiting activity, demonstrating a remarkable antioxidant activity, against oxidative stress.

Highlights

Among the rare-earth metals, cerium is the most abundant one and can exist both in the +3 and +4 oxidation states
The synthesis carried out at 250 ◦ C and in the presence of oleylamine produces regular NPs of about 5 nm of radius characterized by a low clustering tendency, with a well-defined peak in the UV region, due to a major amount of Ce4+
With respect to Ce3+, differently from what observed for CeO2 -NPs synthesized at 150 ◦ C

Summary

Introduction

66 ppm in the Earth crust) and can exist both in the +3 and +4 oxidation states. Cerium oxide exists as both CeO2 and Ce2 O3 in the bulk state [1,2,3,4]. CeO2 , at room temperature and pressure, crystallizes in the fluorite crystal structure, with space group Fm3m. Cerium cations are arranged in a face-centered cubic structure and the O2− anions are positioned in the octahedral interstices. In this structure, each cerium cation is coordinated with eight oxygen anions, while each oxygen anion is coordinated with four cerium cations [4,5]

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Discussion

Conclusion