Effect of TiO2 nanoparticles and multiwall carbon nanotubes on the freshwater diatom Nitzschia frustulum: evaluation of growth, cellular components and morphology

Great attention should be paid to the possible impacts of various nanoparticles on aquatic organism. Freshwater diatoms are essential components of phytoplankton and play a critical role in bioassessment of nanoparticle exposure in the environment. In this study, cell growth was inhibited by TiO2-NPs and MWCNTs, the 24 h EC50 values of TiO2-NPs and MWCNTs to Nitzschia frustulum were 20.75 and 24.64 mg L-1, respectively. Significant decreases of Chl a content after TiO2-NPs exposures were detected and the Chl a content of N. frustulum was obviously increased by MWCNTs treatment at lower concentration. The ROS was detected in N. frustulum after TiO2-NPs and MWCNTs exposures. The MDA content was significantly induced by TiO2-NPs at lower concentrations of 24 and 48 h exposure; meanwhile, it increased at all tested concentrations at 24 h MWCNTs exposure. The SOD enzyme was induced by 72 and 96 h TiO2-NPs exposure, and increased by MWCNTs treatment at 96 h in N. frustulum. Scanning electron microscopy results revealed that N. frustulum had obvious cell deformation after TiO2-NPs treatment. The result showed that the physiological and biochemical response mechanisms after NPs exposure of diatom were species-specific, and in relation to the exposure concentration and time.