Department of Environment and Health, Tianjin Institute of Environmental and Operational Medicine, Tianjin 300050, China.
State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
Molecules. 2018 Mar 8;23(3):606. doi: 10.3390/molecules23030606.
While nanoparticles exert bactericidal effects through the generation of reactive oxygen species (ROS), the processes of the internalization of and the direct physical damage caused by iron oxide nanoparticles are not completely clear. We hypothesize that direct physical or mechanical damage of the cell membrane and cytoplasmic integrity by nanoparticles is another major cause of bacterial death besides ROS. The aim of this study is to investigate the process of the internalization of iron oxide nanoparticles, and to evaluate the effect of direct physical or mechanical damage on bacterial cell growth and death. The results demonstrate that iron oxide nanoparticles not only inhibited cell growth, but also caused bacterial cell death. Iron oxide nanoparticles produced significantly elevated ROS levels in bacteria. Transmission electronic microscopy demonstrated that iron oxide nanoparticles were internalized into and condensed the cytoplasm. Strikingly, we observed that the internalized nanoparticles caused intracellular vacuole formation, instead of simply adsorbing thereon; and formed clusters on the bacterial surface and tore up the outer cell membrane to release cytoplasm. This is the first time that the exact process of the internalization of iron oxide nanoparticles has been observed. We speculate that the intracellular vacuole formation and direct physical or mechanical damage caused by the iron oxide nanoparticles caused the bactericidal effect, along with the effects of ROS.
虽然纳米颗粒通过产生活性氧物质（ROS）发挥杀菌作用，但氧化铁纳米颗粒的内化过程和直接物理损伤的过程尚不完全清楚。我们假设，纳米颗粒对细胞膜和细胞质完整性的直接物理或机械损伤是除 ROS 之外导致细菌死亡的另一个主要原因。本研究旨在探讨氧化铁纳米颗粒的内化过程，并评估直接物理或机械损伤对细菌细胞生长和死亡的影响。结果表明，氧化铁纳米颗粒不仅抑制了细胞生长，还导致了细菌细胞死亡。氧化铁纳米颗粒在细菌中产生了显著升高的 ROS 水平。透射电子显微镜显示，氧化铁纳米颗粒被内化并浓缩细胞质。引人注目的是，我们观察到内化的纳米颗粒在细胞内形成空泡，而不是简单地吸附在其上；并且在细菌表面形成聚集体并撕裂外细胞膜以释放细胞质。这是首次观察到氧化铁纳米颗粒内化的确切过程。我们推测，氧化铁纳米颗粒引起的细胞内空泡形成和直接物理或机械损伤，以及 ROS 的作用，导致了杀菌作用。
