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Antioxidant Properties of Cerium Oxide Nanocrystals as a Function of Nanocrystal Diameter and Surface Coating
Link to Journal Abstract
This work examines the effect of nanocrystal diameter and surface coating on the reactivity of cerium oxide nanocrystals with H2O2 both in chemical solutions and in cells. Monodisperse nanocrystals were formed in organic solvents from the decomposition of cerium precursors, and subsequently phase transferred into water using amphiphiles as nanoparticle coatings. Quantitative analysis of the antioxidant capacity of CeO2-x using gas chromatography and a luminol test revealed that two moles of H2O2 reacted with every mole of cerium (III), suggesting that the reaction proceeds via a Fenton-type mechanism. Smaller diameter nanocrystals containing more cerium (III) were found to be more reactive towards H2O2. Additionally, the presence of a surface coating did not preclude the reaction between the nanocrystal surface cerium (III) and hydrogen peroxide. Taken together, the most reactive nanoparticles were the smallest (e.g. 3.8 nm diameter) with the thinnest surface coating (e.g. oleic acid). Moreover, a benchmark test of their antioxidant capacity revealed these materials were nine times more reactive than commercial antioxidants such as Trolox. A unique feature of these antioxidant nanocrystals is that they can be applied multiple times: over weeks, cerium (IV) rich particles slowly return to their starting cerium (III) content. In nearly all cases, the particles remain colloidally stable (e.g. non-aggregated) and could be applied multiple times as anti-oxidants. These chemical properties were also observed in cell culture, where the materials were able to reduce oxidative stress in human dermal fibroblasts exposed to H2O2 with efficiency comparable to their solution phase reactivity. These data suggest that organic coatings on cerium oxide nanocrystals do not limit the antioxidant behavior of the nanocrystals, and that their redox cycling behavior can be preserved even when stabilized.
This work examines the effect of nanocrystal diameter and surface coating on the reactivity of cerium oxide nanocrystals with H2O2 both in chemical solutions and in cells. The data suggest that organic coatings on cerium oxide nanocrystals do not limit the antioxidant behavior of the nanocrystals, and that their redox cycling behavior can be preserved even when stabilized.
Peer Reviewed Journal Article
Exposure Or Hazard Target
Method Of Study
Material Analysis and Applications
Risk Exposure Group
ACS Nano, 2013, Just Accepted, DOI:10.1021/nn4026806
Lee SS, Song W, Cho M, Puppala HL, Nguyen P, Zhu H, Segatori L, Colvin VL
Last updated on October 15, 2013
This work is supported in part by the Nanoscale Science and Engineering Initiative of the National Science Foundation
under NSF Award Number EEC-0118007.
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