Ceria nanoparticles (CNPs) have recently been shown to protect cells and animals from radiation induced damage. However, most of the CNPs used in previous studies were either naked or weakly protected by surfactants, which inevitably encounter many obstacles in biological applications. Here, alendronate was used as an ideal anchor to graft polyethylene glycol (PEG) onto CNPs, leading to enhanced stability, reduced cytotoxicity, and improved biological properties. Further investigation assessed the protective ability of the nanoparticles against radiation induced effects for human normal liver cells (L-02), indicating that the PEGylatecl CNPs (CNPs-AL-PEG) were more efficient than naked CNPs. We determined that enhanced Ce3+/Ce4+ ratios improved intracellular dispersion and that the ameliorated intracellular distribution of CNPs-AL-PEG contributes to the elevated expression of SOD2, which leads to increased protection of normal cells against ROS and reduces the oxidatively generated DNA damage. These studies hold tremendous promise for raclioprotection and biological applications. (C) 2015 Elsevier Inc. All rights rcserved