Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts, USA.
Environ Toxicol Chem. 2011 Apr;30(4):861-9. doi: 10.1002/etc.445. Epub 2011 Feb 21.
The present study investigated the impact of nano titanium dioxide (nTiO(2) ) exposure on the cellular structures of the nitrogen-fixing cyanobacteria Anabaena variabilis. Results of the present study showed that nTiO(2) exposure led to observable alteration in various intracellular structures and induced a series of recognized stress responses, including production of reactive oxygen species (ROS), appearance and increase in the abundance of membrane crystalline inclusions, membrane mucilage layer formation, opening of intrathylakoidal spaces, and internal plasma membrane disruption. The production of total ROS in A. variabilis cells increased with increasing nTiO(2) doses and exposure time, and the intracellular ROS contributed to only a small fraction (<10%) of the total ROS measured. The percentage of cells with loss of thylakoids and growth of membrane crystalline inclusions increased as the nTiO(2) dose and exposure time increased compared with controls, suggesting their possible roles in stress response to nTiO(2) , as previously shown for metals. Algal cell surface morphology and mechanical properties were modified by nTiO(2) exposure, as indicated by the increase in cell surface roughness and shifts in cell spring constant determined by atomic force microscopy analysis. The change in cell surface structure and increase in the cellular turgor pressure likely resulted from the structural membrane damage mediated by the ROS production. Transmission electron microscopy (TEM) analysis of nTiO(2) aggregates size distribution seems to suggest possible disaggregation of nTiO(2) aggregates when in close contact with microbial cells, potentially as a result of biomolecules such as DNA excreted by organisms that may serve as a biodispersant. The present study also showed, for the first time, with both TEM and Raman imaging that internalization of nTiO(2) particles through multilayered membranes in algal cells is possible. Environ. Toxicol. Chem. 2011; 30:861-869. © 2010 SETAC.
本研究考察了纳米二氧化钛（nTiO(2)）暴露对固氮蓝藻鱼腥藻细胞结构的影响。研究结果表明，nTiO(2)暴露导致各种细胞内结构发生明显改变，并诱导一系列公认的应激反应，包括活性氧（ROS）的产生、膜结晶内含物的出现和增加、膜粘液层的形成、类囊体空间的开放以及内部质膜的破坏。鱼腥藻细胞内总 ROS 的产生随 nTiO(2)剂量和暴露时间的增加而增加，而细胞内 ROS 仅占测量的总 ROS 的一小部分（<10%）。与对照组相比，随着 nTiO(2)剂量和暴露时间的增加，出现类囊体丧失和膜结晶内含物生长的细胞比例增加，表明它们在应对 nTiO(2)的应激反应中可能发挥作用，如先前对金属的研究所示。细胞表面形态和机械性能因 nTiO(2)暴露而发生变化，这表现为原子力显微镜分析中细胞表面粗糙度的增加和细胞弹性常数的变化。细胞表面结构的变化和细胞膨压的增加可能是由 ROS 产生介导的结构膜损伤引起的。透射电子显微镜（TEM）分析 nTiO(2)聚集体的大小分布似乎表明，当与微生物细胞密切接触时，nTiO(2)聚集体可能发生解聚，这可能是由于生物体分泌的 DNA 等生物分子作为生物分散剂发挥作用的结果。本研究还首次通过 TEM 和拉曼成像表明，nTiO(2)颗粒通过藻类细胞的多层膜内化是可能的。《环境毒理学化学》2011 年；30:861-869。 © 2010 SETAC。
