College of Environmental Science and Engineering, Nankai University, Tianjin, 300350, China.
School of Environment, Beijing Normal University, Beijing, 100875, China.
Water Res. 2019 Oct 15;163:114867. doi: 10.1016/j.watres.2019.114867. Epub 2019 Jul 15.
The environmental transformation of nanoparticles results in significant changes in their structure, properties, and toxicity, which are imperative for assessing their environmental impact and health risks. Little is known about the toxicity alteration of fullerene nanoparticles (C) after water disinfection processes considering their potential application in antimicrobial control in water treatment ultimately ending in sewage treatment plants. We showed that C aggregates (nC) were converted to more oxidized forms via commonly used water disinfection processes (i.e., phototransformation and photochlorination treatment). The light-irradiated nanoparticles (UV_nC) exhibited mitigated cytotoxicity relative to nC, whereas photochlorinated nC (UV/Cl_nC) showed an exacerbated outcome. We revealed a distinct toxic mechanism occurring at the nano-bio interface, for which electrons were shuttled by C nanoparticles from membrane-bound NADPH oxidase to extracellular molecular oxygen, resulting in the production of various extracellular reactive oxygen species (ROS). UV/Cl_nC showed the highest electron-shuttling activity due to its high carbonyl content, and more than 2.4-fold higher level of extracellular hydroxyl radicals were detected relative to that in untreated cells. Although UV_nC possessed a somewhat higher carbonyl content than nC, it showed a weaker adhesion to the cell membrane, which compromised the electron-transfer process. The intrinsic ROS generation/quenching capabilities and oxidative potentials of the various nanoparticles were also systematically compared. Overall, this report highlights the importance of understanding environmental transformations in risk assessment and uncovers an overlooked mechanism through which nC/derivatives can modulate the electron transfer process at the nano-bio interface via acting as electron shuttles.
纳米颗粒的环境转化会导致其结构、性质和毒性发生显著变化，这对于评估其环境影响和健康风险至关重要。考虑到富勒烯纳米颗粒（C）在水处理中的抗菌控制方面的潜在应用，最终会进入污水处理厂，因此，在水消毒过程后，其毒性变化知之甚少。我们表明，通过常用的水消毒过程（即光转化和光氯化处理），C 聚集物（nC）被转化为更氧化的形式。与 nC 相比，受光照射的纳米颗粒（UV_nC）表现出减轻的细胞毒性，而光氯化的 nC（UV/Cl_nC）则表现出加剧的结果。我们揭示了在纳米 - 生物界面发生的一种独特的毒性机制，其中 C 纳米颗粒将电子从膜结合的 NADPH 氧化酶转移到细胞外的分子氧，导致各种细胞外活性氧（ROS）的产生。由于其高羰基含量，UV/Cl_nC 表现出最高的电子穿梭活性，并且相对于未处理的细胞，检测到的细胞外羟基自由基水平高出 2.4 倍以上。尽管 UV_nC 的羰基含量略高于 nC，但它与细胞膜的附着力较弱，从而损害了电子转移过程。还系统比较了各种纳米颗粒的固有 ROS 产生/猝灭能力和氧化电位。总体而言，本报告强调了在风险评估中理解环境转化的重要性，并揭示了一个被忽视的机制，即通过充当电子穿梭体，nC/衍生物可以调节纳米 - 生物界面的电子转移过程。
