Magnetic γ-Fe2O3/CeO2 nanoparticles were obtained by precipitation of Ce(NO3)3 with ammonia in the presence of γ-Fe2O3 seeds. The formation of CeO2 nanoparticles on the seeds was confirmed by transmission electron microscopy linked with selected area electron diffraction, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, and dynamic light scattering. The γ-Fe2O3/CeO2 particle surface was functionalized with PEG-neridronate to improve the colloidal stability in PBS and biocompatibility. Chemical and in vitro biological assays proved that the nanoparticles, due to the presence of cerium oxide, effectively scavenged radicals, thus decreasing oxidative stress in the model cell line. PEG functionalization of the nanoparticles diminished their in vitro aggregation and facilitated lysosomal cargo degradation in cancer cells during autophagy, which resulted in concentration-dependent cytotoxicity of the nanoparticles. Finally, the iron oxide core allowed easy magnetic separation of the particles from liquid media and may enable monitoring of nanoparticle biodistribution in organisms using magnetic resonance imaging.

Center for Advanced Preclinical Imaging 1st Faculty of Medicine Charles University Kateřinská 32 120 00 Prague 2 Czech Republic

Center of Interdisciplinary Biosciences Technology and Innovation Park Pavol Jozef Šafárik University in Košice Jesenná 5 041 01 Košice Slovak Republic

Department of Metals and Corrosion Engineering University of Chemistry and Technology Technická 5 Prague 6 166 28 Czech Republic

Institute of Macromolecular Chemistry Czech Academy of Sciences Heyrovského nám 2 162 06 Prague 6 Czech Republic

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High Resolution Powder Electron Diffraction in Scanning Electron Microscopy