酶催化降解四溴双酚A反应引起的碳纳米管急性毒性变化

辣根过氧化物酶催化去除四溴双酚A的反应能够改变多壁碳纳米管(multiwall carbon nanotubes,MWCNTs)在水环境中的稳定性。为探究该反应对碳纳米管生态毒性效应的影响,选择大型蚤(Daphnia magna)和斜生栅藻(Scenedesmus obliquus)作为受试生物,分别考察了反应前后MWCNTs对大型蚤的急性毒性以及对斜生栅藻的生长抑制和藻细胞色素的影响。结果表明,在1~10 mg·L-1的暴露浓度下,与原始的MWCNTs相比,反应后的MWCNTs对大型蚤的急性毒性明显减弱。在10 mg·L-1的暴露剂量下,原始的MWCNTs造成大型蚤的死亡率高达65%,而反应后的MWCNTs引起大型蚤的死亡率仅为23%。此外,反应前后的MWCNTs对斜生栅藻的生长均有抑制作用。随着暴露浓度的增大,藻细胞密度、叶绿素a和b的含量逐渐降低。与原始MWCNTs相比,反应后的MWCNTs对斜生栅藻的毒性明显减弱。上述研究结果为评价MWCNTs的环境风险提供了基础数据。

The Toxic Effect of Multiwall Carbon Nanotubes Modified by the Peroxidase-Mediated Tetrabromobisphenol A Reaction on Daphnia magna and Scenedesmus obliquus

The physicochemical properties of multiwall carbon nanotubes (MWCNTs) were modified by the tetrabromobisphenol A (TBBPA) radicals resulting from the reaction mediated by horseradish peroxidase. The Daphnia magna and Scenedesmus obliquus were selected in this study as the testing organisms to reveal the toxic response of the MWCNTs and the modified MWCNTs resulted from the enzymatic reaction. Our experimental results indicated that the mortality of Daphnia magna caused by the modified MWCNTs was much lower than that of the pristine MWCNTs did. Both the cell density and the pigment (Chlorophyll a and b) content of Scenedesmus obliquus were decreased after the exposure of MWCNTs and modified MWCNTs. However, the above effects induced by the pristine MWCNTs were stronger than that the modified MWCNTs did. The above results suggest that the toxicity of MWCNTs was changed by the enzymatic reaction, providing a preliminary data for evaluating the risks of MWCNTs in the natural environment.