纳米氧化锌对羊角月牙藻毒性效应及其在藻细胞内外的分布

为研究纳米氧化锌(ZnO NP)的毒性效应及其在细胞内外分布,以羊角月牙藻(Selenastrum capricornutum)为模型藻类,研究了不同浓度ZnO NP对羊角月牙藻生长、叶绿素含量、可溶性蛋白含量、超氧化物岐化酶(SOD)及过氧化物酶(POD)活性、丙二醛(MDA)含量及细胞内外ZnO NP含量变化。结果表明,ZnO NP对羊角月牙藻的生长抑制与处理浓度呈现正相关。在45 mg·L~(-1)ZnO NP暴露24 h后,其生长抑制率已达到95%。当ZnO NP处理藻细胞72 h后,羊角月牙藻细胞的叶绿素含量与处理浓度之间存在剂量-效应关系。低浓度(0.5 mg·L~(-1))ZnO NP处理后藻细胞可溶性蛋白质含量、SOD和POD活性明显下降,MDA含量升高,其产生的毒性效应高于高浓度组(5 mg·L~(-1)、45 mg·L~(-1))。细胞培养液溶出Zn2+量及藻细胞外吸附的ZnO NP量与ZnO NP处理浓度成正比,但是藻细胞内ZnO NP量与ZnO NP浓度没有相关性,胞内积累量基本维持不变。研究表明,各浓度组对藻细胞毒性的差异,不仅与细胞内Zn2+量有关,还与细胞外粘附的ZnO NP有关。

Toxicities of ZnO Nanoparticles on Selenastrum capricornutum and Its Distributions in Intra- and Extra-Cells

To study the toxic effects and cellular distributions of ZnO nanoparticles (ZnO NP) in microalgae, we investigated the growth, chlorophyll contents and protein contents, the activities of superoxide dismutase (SOD) and peroxidase (POD), the contents of malonydialdehyde (MDA) and intra- and extra-cellular ZnO NP concentrations in S.capricornutum after ZnO NP exposure.The results indicated that the growth of S.capricornutum was significantly inhibited by ZnO NP, and a positive correlation was found between ZnO NP levels and the biomass concentration of S.capricornutum in medium.The growth inhibition rate was over 95% after 45 mg·L-1 ZnO NP treatment for 24 h.The chlorophyll contents was decreased with increasing ZnO NP concentrations in a dose-dependent manner.After 0.5 mg·L-1 ZnO NP exposure for 72 h, both of the protein contents and the activities of POD and SOD of S.capricornutum decreased significantly, while MDA contents in algae cells increased dramatically, compared to the control.The toxic effects induced by low concentrations of ZnO NP (0.5 mg·L-1) were more significant than those of higher concentrations of ZnO NP treatments (5 mg·L-1, 45 mg·L-1) in terms of protein contents, MDA contents, POD and SOD activities.Both Zn2+ contents dissolved from ZnO NP to culture medium and contents of ZnO NP adsorbed on algae surface increased with the increase of the concentrations of ZnO NP.No significant correlation was observed between ZnO NP contents inside algal cells and the treatment concentrations of ZnO NP, and the intracellular accumulation of Zn almost remained constant.The results showed that the cytotoxicity of ZnO NPs to algal cells was not only related to the contents of intracellular Zn2+ but also to the extracellular adhesion of ZnO NP.