活性氧
过氧化氢酶
超氧化物歧化酶
激进的
氧化铈
铈
抗氧化剂
密度泛函理论
氧气
羟基自由基
过氧化氢
吸附
材料科学
化学
氧化物
化学工程
无机化学
有机化学
计算化学
生物化学
工程类
作者
Hongyang Ma,Zhao Liu,Pramod Koshy,Charles C. Sorrell,Judy N. Hart
标识
DOI:10.1021/acsami.1c24686
摘要
There is considerable interest in the pH-dependent, switchable, biocatalytic properties of cerium oxide (CeO2) nanoparticles in biomedicine, where these materials exhibit beneficial antioxidant activity against reactive oxygen species (ROS) at a basic physiological pH but cytotoxic prooxidant activity in an acidic cancer cell pH microenvironment. While the general characteristics of the role of oxygen vacancies are known, the mechanism of their action at the atomic scale under different pH conditions has yet to be elucidated. The present work applies density functional theory (DFT) calculations to interpret, at the atomic scale, the pH-induced behavior of the stable {111} surface of CeO2 containing oxygen vacancies. Analysis of the surface-adsorbed media species reveals the critical role of pH on the interaction between ROS (•O2- and H2O2) and the defective CeO2 {111} surface. Under basic conditions, the superoxide dismutase (SOD) and catalase (CAT) biomimetic reactions can be performed cyclically, scavenging and decomposing ROS to harmless products, making CeO2 an excellent antioxidant. However, under acidic conditions, the CAT biomimetic reaction is hindered owing to the limited reversibility of Ce3+ ↔ Ce4+ and formation ↔ annihilation of oxygen vacancies. A Fenton biomimetic reaction (H2O2 + Ce3+ → Ce4+ + OH- + •OH) is predicted to occur simultaneously with the SOD and CAT biomimetic reactions, resulting in the formation of hydroxyl radicals, making CeO2 a cytotoxic prooxidant.
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