Department of Ecology and Coastal Management, Institute of Marine Sciences of Andalusia (CSIC), Campus Río S. Pedro, 11510 Puerto Real, Cádiz, Spain.
Department of Material Science, Metallurgical Engineering and Inorganic Chemistry, Faculty of Sciences, University of Cadiz, E-11510 Puerto Real, Cádiz, Spain.
Sci Total Environ. 2017 Jul 15;590-591:304-315. doi: 10.1016/j.scitotenv.2017.03.007. Epub 2017 Mar 7.
CeO nanoparticles (CeO NPs) are well-known for their catalytic properties and antioxidant potential. Recent uses in therapy are based on the Ce ions released by CeO NPs. Reactions involving redox cycles between Ce and Ce oxidation stage seem to promote scavenging of reactive oxygen species (ROS), thus protecting cells from oxygen damage. However, the internalization of CeO NPs and release of Ce could be responsible for a toxic effect on cells. The literature reports controversial results on the toxicity of CeO NPs to phytoplankton. Therefore, we have tested the potential toxic effect of two CeO NPs (with positive and negative zeta potential) and bulk CeO (at 0.1, 1, 10, 100 and 200mg·L) on three species of microalgae from different environments: marine diatom (Phaeodactylum tricornutum), marine chlorophyte (Nannochloris atomus) and freshwater chlorophyte (Chlamydomonas reinhardtii) over 72h in batch cultures. Responses measured in the microalgae population are: growth, chlorophyll a, cell size, cell complexity, percentage of ROS, and percentage of cell membrane damage. Positive zeta potential CeO NPs provoked greater cell complexity (up to 78, 172 and 23 times more cell complexity than in controls found for C. reinhardtii, P. tricornutum and N. atomus respectively) than negative zeta potential CeO NPs. The SSC signal detected by flow cytometry measured increases of particles entering cells, and this is related to cell viability and levels of intracellular ROS (correlation between SSC and percentage of ROS of 0.72 and 0.97 found for C. reinhardtii and P. tricornutum). When increased cellular complexity over controls is between 2 and 6 times greater, CeO (in bulk or nanoparticulate form) seems to protect against ROS. When increased cellular complexity is from 7 to 23 times greater, CeO does not provoke toxic responses; however, when increased cellular complexity over controls is very high, from 61 to 172 times, increased ROS production and toxic responses are found. Results show that two factors, the charge of CeO NPs and cell wall structure, constitute the primary barrier to the possible accumulation of CeO NPs within phytoplankton cytosol.
CeO 纳米粒子（CeO NPs）以其催化性能和抗氧化潜力而闻名。最近在治疗中的应用基于 CeO NPs 释放的 Ce 离子。Ce 和 Ce 氧化态之间的氧化还原循环反应似乎促进了活性氧物种（ROS）的清除，从而保护细胞免受氧损伤。然而，CeO NPs 的内化和 Ce 的释放可能对细胞产生毒性作用。文献报道了 CeO NPs 对浮游植物的毒性存在争议的结果。因此，我们测试了两种 CeO NPs（带正电和负电）和块状 CeO（浓度分别为 0.1、1、10、100 和 200mg·L）对来自不同环境的三种微藻（海洋硅藻（Phaeodactylum tricornutum）、海洋绿藻（Nannochloris atomus）和淡水绿藻（Chlamydomonas reinhardtii））的潜在毒性作用，在批式培养中培养 72 小时。在微藻种群中测量的反应是：生长、叶绿素 a、细胞大小、细胞复杂性、ROS 百分比和细胞膜损伤百分比。带正电的 CeO NPs 比带负电的 CeO NPs 引起更大的细胞复杂性（与对照相比，C. reinhardtii、P. tricornutum 和 N. atomus 的细胞复杂性分别增加了 78、172 和 23 倍）。流式细胞术检测到的 SSC 信号表明进入细胞的颗粒增加，这与细胞活力和细胞内 ROS 水平相关（C. reinhardtii 和 P. tricornutum 的 SSC 与 ROS 百分比之间的相关性分别为 0.72 和 0.97）。当细胞复杂性比对照增加 2 到 6 倍时，CeO（以块状或纳米颗粒形式）似乎可以防止 ROS。当细胞复杂性比对照增加 7 到 23 倍时，CeO 不会引起毒性反应；然而，当细胞复杂性比对照增加非常高，从 61 到 172 倍时，会发现 ROS 产生增加和毒性反应。结果表明，CeO NPs 的电荷和细胞壁结构这两个因素构成了 CeO NPs 在浮游植物细胞质中可能积累的主要障碍。
