Abstract
The rapid development of nanotechnology makes various kinds of nano-commodities have been packed in our life, but these nano-materials which may cause hazards to human and environment also lead much attention. In this study, the electrical low pressure impactor (ELPI) and Zetasizer were first used to discuss the different size distribution and agglomerate state of nano-ZnO in various sizes. Different sonication methods were compared for improving the dispersion of nanoparticles in water. Then, the agglomeration state of nanoparticles in various conditions water sysem such as pH value, ionic strength and existence of surfactant were discussed. Another study focused on the agglomeration and sedimentation of nanoparticles in a complicated DMEM cell culture medium. The results would be estimated suitable conditions for assessing the nano-ZnO cytotoxicity. In addition, self-prepared nano-ZnO which had different physicochemical properties (sizes, shapes and surface properties) were utilized to assess their correlation with toxicological responses. Finally, TiO2-coated ZnO was prepared to investigate the shell thickness effect and phase effect on the cytotoxicity. The results showed that when nano-ZnO transported from air to the water, the particles aggregated seriously. After comparing different sonication methods, the probe sonication got excellent dispersion result. The pH value, ionic strength and the surfactant existence of water contributed significant effect on the hydrodynamic size of nanoparticles, which was attributed to the variety of double electric layer on the particles surface. As particles dispersed to DMEM medium, the hydrodynamic size of particles increased to 900 nm even the suspension was sonicated. If serum was added into the medium, the suspension became stable. In MTT and IL-8 experiments, it could find that particles appeared more toxicity in serum-free medium. Nanorod and nanosphere ZnO were successfully produced by precipitation and solvothermal methods, the hydrophobic surface property of nano-ZnO was also prepared by adding oleic acid. Smaller particles had more toxicity than the large one could be found in either rod and sphere particles. Furthermore, under similar particle size the rod shapes ZnO were more toxic than sphere shapes. Hydrophobic ZnO particles in water system caused serious agglomeration and lower toxicity, while the more amount of potential IL-8 release than the non-modified nanoparticles. Interestingly, the particle surface area didn’t show significant relations on its toxicity. The ZnO-TiO2 core-shell structure was prepared and confirmed that increasing coating time increased shell thickness. The amorphous TiO2 shell was demonstrated by XRD, and this material exhibited more potential toxicity than other phases TiO2 nanoparticles (P25 and ST-21), which represented the phases of nanoparticles played more important role than their size effect. Though amorphous TiO2 still had toxicity, the thickness shell slightly decreased the toxicity of nano-ZnO. It might be attributed to the lower rate of releasing zinc ion or the partial uncovered ZnO. In this study, under the same mass concentration dosage, the effects of different physicochemical properties of nanoparticles inducing the toxicological responses are prioritized as follows: species > phase > shape > size > surface area.