Department of Molecular Medicine, Human Physiology Unit, University of Pavia, 27100 Pavia, Italy.
Department of Chemistry, University of Pavia, 27100 Pavia, Italy.
Nanoscale. 2017 Jan 26;9(4):1527-1538. doi: 10.1039/c6nr07701c.
CeO nanoparticles (CNPs) have been investigated as promising antioxidant agents with significant activity in the therapy of diseases involving free radicals or oxidative stress. However, the exact mechanism responsible for CNP activity has not been completely elucidated. In particular, in situ evidence of modification of the oxidative state of CNPs in human cells and their evolution during cell internalization and subsequent intracellular distribution has never been presented. In this study we investigated modification of the Ce(iii)/Ce(iv) ratio following internalization in human cells by X-ray absorption near edge spectroscopy (XANES). From this analysis on cell pellets, we observed that CNPs incubated for 24 h showed a significant increase in Ce(iii). By coupling on individual cells synchrotron micro-X-ray fluorescence (μXRF) with micro-XANES (μXANES) we demonstrated that the Ce(iii)/Ce(iv) ratio is also dependent on CNP intracellular localization. The regions with the highest CNP concentrations, suggested to be endolysosomes by transmission electron microscopy, were characterized by Ce atoms in the Ce(iv) oxidation state, while a higher Ce(iii) content was observed in regions surrounding these areas. These observations suggest that the interaction of CNPs with cells involves a complex mechanism in which different cellular areas play different roles.
CeO 纳米颗粒（CNPs）已被研究为具有抗氧化活性的有前途的抗氧化剂，在涉及自由基或氧化应激的疾病治疗中具有显著的活性。然而，CNP 活性的确切机制尚未完全阐明。特别是，从未提出过在人细胞中 CNP 氧化态的原位修饰及其在细胞内化和随后的细胞内分布过程中的演变的证据。在这项研究中，我们通过 X 射线吸收近边缘光谱（XANES）研究了人细胞内内化后 Ce(iii)/Ce(iv) 比值的变化。通过对细胞沉淀物的分析，我们观察到孵育 24 小时的 CNPs 中 Ce(iii)明显增加。通过将同步加速器微 X 射线荧光（μXRF）与微 X 射线吸收近边缘结构（μXANES）相结合，我们证明 Ce(iii)/Ce(iv) 比值也取决于 CNP 的细胞内定位。具有最高 CNP 浓度的区域（通过透射电子显微镜提示为内溶酶体）的 Ce 原子呈 Ce(iv)氧化态，而在这些区域周围观察到更高的 Ce(iii)含量。这些观察结果表明，CNPs 与细胞的相互作用涉及一种复杂的机制，其中不同的细胞区域发挥不同的作用。
