title: Evaluation of the toxicity of ZnO nanoparticles to Chlorella vulgaris by use of the chiral perturbation approach.
abstract: The toxicity of ZnO nanoparticles (NPs) has been widely investigated because of their extensive use in consumer products. The mechanism of the toxicity of ZnO NPs to algae is unclear, however, and it is difficult to differentiate between particle-induced toxicity and the effect of dissolved Zn(2+). In the work discussed in this paper we investigated particle-induced toxicity and the effects of dissolved Zn(2+) by using the chiral perturbation approach with dichlorprop (DCPP) as chiral perturbation factor. The results indicated that intracellular zinc is important in the toxicity of ZnO NPs, and that ZnO NPs cause oxidative damage. According to dose-response curves for DCPP and the combination of ZnO NPs with (R)-DCPP or (S)-DCPP, the toxicity of DCPP was too low to perturb the toxicity of ZnO NPs, so DCPP was suitable for use as chiral perturbation factor. The different glutathione (GSH) content of algal cells exposed to (R)-DCPP or (S)-DCPP correlated well with different production of reactive oxygen species (ROS) after exposure to the two enantiomers. Treatment of algae with ZnO NPs and (R)-DCPP resulted in reduced levels of GSH and the glutathione/oxidized glutathione (GSH/GSSG) ratio in the cells compared with the control. Treatment of algae with ZnO NPs and (S)-DCPP, however, resulted in no significant changes in GSH and GSH/GSSG. Moreover, trends of variation of GSH and GSH/GSSG were different when algae were treated with ZnSO4·7H2O and the two enantiomers. Overall, the chiral perturbation approach revealed that NPs aggravated generation of ROS and that released Zn(2+) and NPs both contribute to the toxicity of ZnO NPs.
authors.affiliation: College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhou
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Wang
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhou
authors.forename: Hongzhou
authors.initials: H
authors.lastname: Yao
authors.forename: Farooq
authors.initials: F
authors.lastname: Ahmad
mesh_terms: D000975:Antioxidants / Q000737:chemistry; D001681:Biological Assay; D002473:Cell Wall / Q000187:drug effects; D002623:Chemistry Techniques, Analytical; D048408:Chlorella vulgaris / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000737:chemistry; D007477:Ions; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010100:Oxygen / Q000737:chemistry; D011392:Proline / Q000031:analogs & derivatives / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D017382:Reactive Oxygen Species; D015203:Reproducibility of Results; D013237:Stereoisomerism; D013997:Time Factors; D015032:Zinc / Q000032:analysis / Q000737:chemistry; D015034:Zinc Oxide / Q000032:analysis* / Q000737:chemistry
chemical_list: D000975:Antioxidants; D007477:Ions; D011725:Pyridines; D017382:Reactive Oxygen Species; C062806:4,4-dicarboxy-5-pyridoxylproline; D011392:Proline; D005978:Glutathione; D015032:Zinc; D010100:Oxygen; D015034:Zinc Oxide