纳米MgO对斜生栅藻的毒性效应及致毒机理  

Toxicities and mechanisms of MgO nanoparticles to Scenedesmus obliquus

作　　者：吴明珠[1] 何梅琳[1] 邹山梅[1] 邓祥元[1] 王长海[1] 

机构地区：[1]南京农业大学资源与环境科学学院,南京210095

出　　处：《环境化学》2015年第7期1259-1267,共9页Environmental Chemistry

基　　金：江苏省自然科学基金(BK20140713);中国博士后科学基金(2013M531370;2014T70532)资助

摘　　要：为探究纳米氧化镁(MgO)对微藻的毒性效应及致毒机制,以斜生栅藻(Scenedesmus obliquus)为实验材料,测定了纳米MgO对斜生栅藻细胞形态、生长、叶绿素含量及SOD和POD酶活性的影响.结果表明,低浓度的纳米MgO(>0.8 mg·L-1)即可对斜生栅藻的生长及叶绿素的合成有抑制作用,说明纳米MgO对斜生栅藻具有明显的毒性.100 mg·L-1纳米MgO处理时,完全抑制了栅藻的生长和叶绿素的合成,藻细胞在4 d内死亡.通过亚甲基蓝还原法测定培养体系中活性氧(ROS)含量发现,随着纳米MgO浓度的升高,ROS大量增加;且纳米MgO暴露条件下,POD酶活性相比于对照组显著增强,但不同浓度纳米MgO处理组之间POD酶活性无明显差异.纳米MgO处理96 h后,当其浓度高于0.8 mg·L-1时,SOD酶活性随浓度升高而降低,表明长时间暴露于纳米MgO后,SOD酶活性受高浓度纳米MgO抑制,而POD酶则作为主要的抗氧化酶清除产生的各种自由基.扫描电镜观察发现,纳米MgO(>20 mg·L-1)处理时,斜生栅藻细胞变形,甚至裂解.纳米MgO发生团聚,附着在栅藻细胞表面;团聚的纳米MgO对藻细胞鞭毛有缠绕作用,使细胞聚集成团,限制了藻细胞的游动,并导致细胞间相互遮弊,不利于藻细胞吸收光能.透射电镜观察发现,纳米MgO没有进入藻细胞内部.通过测定纳米MgO解离出的Mg2+的含量和对藻细胞部分生理生化指标的影响发现,其对藻细胞没有毒性效应.因此,纳米MgO对斜生栅藻的致毒机理可归纳为:通过释放大量ROS对藻细胞产生氧化胁迫抑制其生长;高浓度的纳米MgO引起藻细胞的接触性物理损伤,导致藻细胞质壁分离,裂解;同时纳米MgO团聚并覆盖在藻细胞表面,通过与藻细胞鞭毛的相互作用使细胞聚集成团,影响细胞的正常游动及其对光能、营养物质的吸收利用和气体的交换.To reveal the toxicities of MgO nanoparticles （nano-MgO） on microalgae and the toxic mechanism, the response of growth, chlorophyll concentration, superoxide dismutase （ SOD ） and peroxidase （POD） activities and its morphology of Scenedesmus obliquus exposed to different concentrations of nano-MgO were analyzed. The results showed that nano-MgO significantly inhibited the growth and the chlorophyll synthesis of S. obliquus, indicating that nano-MgO imposed a biological toxicity on S. obliquus. When treated with 100 mg·L^-1 nano-MgO, the growth and increment of chlorophyll of the algal culture was completely inhibited, and the culture died after 4 d of incubation. The content of reactive oxygen species （ROS） in the algal culture increased substantially with the concentration of nano-MgO. Enhancement of POD activity was observed in all treatments with different concentrations of nano-MgO, while nano-MgO （ 〉0.8 mg· L^-1 ） inhibited SOD activity. The POD acted as the main antioxidant enzymes to remove all kinds of free radicals. The scanning electron micrographs revealed that high concentration （ 〉 20 mg· L^-1 ） of nano-MgO resulted in cell deformation even split. Nano-MgO tended to aggregate and adhere to the surface of the algal cells. The aggregates of nano-MgO entrapped the flagella of S. obliquus, leading to the formation of a larger aggregates comprised of the algal cells and nanoparticles. As indicated by the transmission electron micrographs, no nano-MgO was observed inside the algae cells, which might be due to the blocking effect of algal cell wall. The concentration of Mg^2＋ dissociated from nano-MgO was positively correlated with the concentrations of nano-MgO. However, the free Mg〉 did not impose toxic effect on S. obliquus. Therefore, the toxic mechanism of nano-MgO could be mainly attributed to the oxidative stress induced by substantial ROS released by nano-MgO, which inhibited cell growth. The high concentrations of nano-MgO （ 〉 100 mg· L^-1 ） caused the cont

关 键 词：纳米MgO 斜生栅藻 毒性效应 致毒机理. 

分 类 号：X171.5[环境科学与工程—环境科学]