Abstract：
The mechanisms of toxicity of engineered nanomaterials (ENMs) to the early life stages of freshwater fish, and the relative hazard compared to dissolved metals, is only partially understood. In the present study, zebrafish (Danio rerio) embryos were exposed to lethal concentrations of silver nitrate (AgNO3) or silver (Ag) ENMs (primary size 42.5 ± 10.2 nm). The 96 h-LC50 for AgNO3 was 32.8 ± 0.72 μg Ag L-1 (mean ± 95% CI) compared to 6.5 ± 0.4 mg L-1 of the whole material for Ag ENMs; with the ENMs being orders of magnitude less toxic than the metal salt. The EC50 for hatching success was 30.5 ± 1.4 μg Ag L-1 and 6.04 ± 0.4 mg L-1 for AgNO3 and Ag ENMs, respectively. Further sub-lethal exposures were performed with the estimated LC10 concentrations for both AgNO3 or Ag ENMs over 96 h, where about 3.7% of the total Ag as AgNO3 was internalised, as measured by Ag accumulation in the dechorionated embryos. However, for the ENM exposures, nearly all (99.8%) of the total Ag was associated with chorion; indicating the chorion as an effective barrier to protect the embryo in the short term. Calcium (Ca2+) and sodium (Na+) depletion was induced in embryos by both forms of Ag, but hyponatremia was more pronounced in the nano form. Total glutathione (tGSH) levels declined in embryos exposed to both Ag forms, but a superior depletion occurred with the nano form. Nevertheless, oxidative stress was mild as superoxide dismutase (SOD) activity stayed uniform and the sodium pump (Na+/K+-ATPase) activity had no appreciable inhibition compared to the control. In conclusion, AgNO3 was more toxic to the early life stage zebrafish than the Ag ENMs, still differences were found in the exposure and toxic mechanisms of both Ag forms.
摘要：
工程纳米材料（ENM）对淡水鱼早期生命阶段的毒性机制，以及与溶解金属相比的相对危险，只是部分理解。在本研究中,斑马鱼（Daniorerio）胚胎暴露于致死浓度的硝酸银（AgNO3）或银（Ag）ENM（主要尺寸为42.5±10.2nm）。AgNO3的96h-LC50为32.8±0.72μgAgL-1（平均±95％CI），而AgENM的整个材料为6.5±0.4mgL-1；ENM的毒性比金属盐低几个数量级。AgNO3和AgENM孵化成功的EC50为30.5±1.4μgAgL-1和6.04±0.4mgL-1，分别。在96小时内，对AgNO3或AgENM的估计LC10浓度进行了进一步的亚致死暴露，其中AgNO3约占总Ag的3.7％。通过在脱细胞胚胎中的Ag积累来衡量。然而,对于ENM暴露，几乎所有（99.8％）的总银与绒毛膜有关；表明绒毛膜是在短期内保护胚胎的有效屏障。两种形式的Ag在胚胎中诱导钙（Ca2）和钠（Na）消耗，但纳米形式的低钠血症更为明显。暴露于两种Ag形式的胚胎中总谷胱甘肽（tGSH）水平下降，但是纳米形式发生了优越的消耗。然而，氧化应激是温和的，因为与对照组相比，超氧化物歧化酶（SOD）活性保持均匀，钠泵（Na/K-ATPase）活性没有明显的抑制作用。总之,AgNO3对生命早期斑马鱼的毒性比AgENM更大，两种Ag形式的暴露和毒性机制仍存在差异。
