†MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, P. R. China.
‡Department of Applied Chemistry, South China Agricultural University, Guangzhou 510642, P. R. China.
ACS Appl Mater Interfaces. 2015 Apr 22;7(15):8233-42. doi: 10.1021/acsami.5b01271. Epub 2015 Apr 9.
Polyvinylpyrrolidone-stabilized iridium nanoparticles (PVP-IrNPs), synthesized by the facile alcoholic reduction method using abundantly available PVP as protecting agents, were first reported as enzyme mimics showing intrinsic catalase- and peroxidase-like activities. The preparation procedure was much easier and more importantly, kinetic studies found that the catalytic activity of PVP-IrNPs was comparable to previously reported platinum nanoparticles. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) characterization indicated that PVP-IrNPs had the average size of approximately 1.5 nm and mainly consisted of Ir(0) chemical state. The mechanism of PVP-IrNPs' dual-enzyme activities was investigated using XPS, Electron spin resonance (ESR) and cytochrome C-based electron transfer methods. The catalase-like activity was related to the formation of oxidized species Ir(0)@IrO2 upon reaction with H2O2. The peroxidase-like activity originated from their ability acting as electron transfer mediators during the catalysis cycle, without the production of hydroxyl radicals. Interestingly, the protective effect of PVP-IrNPs against H2O2-induced cellular oxidative damage was investigated in an A549 lung cancer cell model and PVP-IrNPs displayed excellent biocompatibility and antioxidant activity. Upon pretreatment of cells with PVP-IrNPs, the intracellular reactive oxygen species (ROS) level in response to H2O2 was decreased and the cell viability increased. This work will facilitate studies on the mechanism and biomedical application of nanomaterials-based enzyme mimic.
聚乙烯吡咯烷酮稳定的铱纳米粒子（PVP-IrNPs），通过简单的醇还原法合成，以丰富的聚乙烯吡咯烷酮（PVP）作为保护剂，首次被报道为具有内在过氧化物酶和过氧化氢酶样活性的酶模拟物。该制备方法更加简单，更重要的是，动力学研究发现，PVP-IrNPs 的催化活性可与先前报道的铂纳米粒子相媲美。透射电子显微镜（TEM）和 X 射线光电子能谱（XPS）表征表明，PVP-IrNPs 的平均尺寸约为 1.5nm，主要由 Ir(0)化学状态组成。通过 XPS、电子顺磁共振（ESR）和基于细胞色素 C 的电子转移方法研究了 PVP-IrNPs 双酶活性的机制。过氧化氢酶样活性与 Ir(0)@IrO2 氧化物种的形成有关，这是与 H2O2 反应的结果。过氧化物酶样活性源于它们在催化循环中作为电子转移介质的能力，而不会产生羟基自由基。有趣的是，在 A549 肺癌细胞模型中研究了 PVP-IrNPs 对 H2O2 诱导的细胞氧化损伤的保护作用，结果表明 PVP-IrNPs 具有良好的生物相容性和抗氧化活性。在用 PVP-IrNPs 预处理细胞后，细胞内活性氧（ROS）水平对 H2O2 的响应降低，细胞活力增加。这项工作将有助于研究基于纳米材料的酶模拟物的机制和生物医学应用。
