Research On Biotoxicity And Toxic Mechanism Of NiO Nanoparticles On Chlorella Vulgaris

Along with the rapid development of nanotechnology, all sorts of nanomaterials are widely applied to every aspect of life. Because of nanomaterial has many different properties comparing with their bulk counterparts, the negative effects to human health and the living environment produced by them has raised widly public concern, which became an urgent problem of science.In order to evaluate the potential impact to marine ecosystem after nano- materials leaked to water, we discussed the aquatic biological effects and toxicity mechanism of NiO nanoparticles, using Chlorella vulgaris. Main research results show as follows:1) According to OECD 201 algae growth inhibition method, we investigated the influence of two sizes NiO nanoparticles (nano and microns) on the growth of Chlorella vulgaris. It was implied that the nano-NiO particles showed more toxicity than micro-NiO, and their inhibition effect obviously depends on the doses.2) According to the standard of toxicity assessment of OECD and EU, the toxicity of NiO nanoparticles were defined as acute 2, toxic to Chlorella vulgaris; NiO microns particles were low-toxic and defined as chronic 3, harmful to Chlorella vulgaris.3) By optical microscope and transmission electron microscope (TEM) analysis, we found that different dispersed environment could influence the aggregation of NiO nanoparticles, the deposition of nanoparticles in seawater is more obviously than that in ultra-pure water. Otherwise algae could interact with nanoparticles, form micro interface, accelerated the aggregation and deposition of NiO.4) NiO nanoparticles exposure produced oxidative damage to Chlorella vulgaris at 72h. Performance for lipid peroxidation level remarkable increased, and the activity of antioxidant enzymes SOD and CAT increased significantly in cells.5) Chlorophyll content in cells declined after NiO nanoparticles treatment, transcriptions of psaB coding the reaction center protein of PS I decreased; but expression level of dark reaction gene rbcL increased signifacantly. It was suggested that NiO nanoparticles exposure has effect on algae photosynthesis system.Our results suggested that NiO nanoparticles showed toxicity to marine microalgae. Its toxigenicity mechanism on Chlorella vulgaris can be classified into the following:i, size effect of NiO nanoparticles;ii, NPs produce of free radicals cause oxidative damage to cells; iii, NPs inhibited algae photosynthesis system through gene expression and chlorophyll synthetic; iv, the shading effect caused by NPs attached on algae.