Anti-oxidation Mechanism And Bio-application Of Cerium Oxides Based Nanomaterials

Many diseases are closely related to reactive oxygen species produced by the aerobic metabolism. Therefore, the supplement of anti-oxidant which can scavenge excess oxygen species is necessary. Compared with small molecule anti-oxidant like vitamin E and vitamin C, redox-active nanomaterials are more favorable, by virtue of rich active sites and excellent stability. Among the redox-active nanomaterials, cerium oxides?CeO₂? nanomaterials have attracted great interest due to their outstanding redox properties.This dissertation is devoted to the study on synthesis, anti-oxidation mechanism, and modulation of anti-oxidation and bio-application of CeO₂ nanoparticles. CeO₂ acts as attractive catalyst due to the reversible conversion between Ce3+ and Ce4+. During the anti-oxidation process, the phase, surface state and local coordination environment of CeO₂ nanoparticles have been found out via various characterization methods, so as to obtain a systematical understanding of the anti-oxidation mechanism. On this basis, we proposed a general method to delicately engineer the anti-oxidation ability through modulating the defect state and reducibility of CeO₂ nanoparticles by Gd3+ doping. In addition, the anti-oxidation of CeO₂ nanoparticles has also been assessed in cell culture. Furthermore, multifunctional CeO₂-based nanomaterials have been studied so as to broaden the potential bio-application of CeO₂ nanomaterials. The contents of this dissertation are described as follows:?1? The understanding of anti-oxidation mechanism and modulation of anti-oxidation ability of CeO₂ nanoparticles.During the anti-oxidation process of CeO₂ nanoparticles reacting with H₂O₂, the value state and coordination environment of Ce have been measured by various characterization methods such as UV-Vis absorption spectroscopy, X-ray near edge absorption spectroscopy and Raman spectroscopy. The UV-Vis absorption of CeO₂ nanoparticles shifts to red after the addition of H₂O₂ and the shift extent increases with the concentration of H₂O₂. Meanwhile, the coordination number of Ce increases after the addition of H₂O₂, and recovers back to near the initial value as the reaction proceeds. In addition, adsorbed peroxides species are detected during the anti-oxidation process, which are responsible for the red-shifted absorption spectra of CeO₂ nanoparticles. On the basis of these results, the reactivity of coordination sites for peroxides species is considered to play as a key role in the anti-oxidation performance of CeO₂ nanoparticles. Additionally, the reduction of Ce4+ to Ce3+ is proposed to be a key step from the experiment on the effect of extra H+/OH- on the anti-oxidation performance of CeO₂ nanoparticles.Oxygen defects were tailored through doping Gd3+ in CeO₂ nanoparticles. In the probe reaction with H₂O₂, CeO₂:Gd nanoparticles showed better anti-oxidation performance than pure CeO₂ due to the enhanced coordination and reducibility after Gd3+ doping. Therefore, we show a robust method to delicately modulate the anti-oxidation of CeO₂ nanoparticles.?2? Multi-functionalization and bio-application of Ce O2-based nanomaterials.Multifunctional CeO₂-based nanoparticles were constructed by doping other rare earth metal ions. In this dissertation, the prepared CeO₂:Gd nanoparticles showed excellent anti-oxidation, magnetic resonance imaging and CT imaging. This multifunctional nanomaterial has potential application in the tracking in the clinical anti-oxidation treatment of CeO₂-based nanomaterials.We studied the application of CeO₂ nanoparticles in three oxidative damage models of INS-1 cells induced by H₂O₂, high glucose and STZ. CeO₂ nanoparticles can protect INS-1 cells from H₂O₂ induced damage. Moreover, CeO₂ nanoparticles have potential application in adjuvant therapy of leucocythemia.