Embryotoxicity Of Typical Nanomaterials And Preliminary Study On Its Oxidative Stress Mechanism

Background: In recent years, as nanotechnology and materials science progressed by leaps and bounds, engineered nanomaterials have been mass-produced and widely applied. Simultaneously, people are increasingly exposed to various kinds of manufactured nanoparticles. Though the biological effects of some nanomaterials have been already assessed, information on embryotoxicity of various particle types are fairly sparse. Moreover, rare studies have compared the toxicological effects of different types of nanomaterials including carbonaceous, siliceous, and metal oxide nanoparticles. Therefore, the interrelationship between nanoparticles properties(e.g. size, shape, chemical composition) and their biological effects remains unclear.Objective: In this paper, we aimed to: 1) investigate the embryotoxicity of different types of nanomaterials; 2) identify the mechanism of oxidative stress through which nanoparticles induced embryotoxicity; 3) explore the interrelationship between particle size, shape, chemical composition and toxicological effects of four typical nanomaterials with comparable properties.Methods: We used a consistent set of in vivo and in vitro experimental protocols to study four different typical nanomaterials that are characterized in particle size, shape and chemical composition: (i)carbon black(Nano-CB), (ii)single wall carbon nanotubes(CNTs), (iii)silicon dioxide(Nano- SiO2) and (iv)zinc dioxide(Nano-ZnO). In animal study, pregnant-1day rats were exposed to nanomaterials by intratracheal instillation at a daily dose of 10 mg/kg bw for 7 days, the control group was instilled the same volume of new born calf serum which served as solvent for particle suspension. On the 20th day after mating, the rats were sacrificed and the examination on gestation, birth and fetus development were carried out. For in vitro study, cytotoxicity induced by nanoparticles was sufficiently measured by cellular morphology observation and three forms of viability assays: the MTT assay, the WST assay and lactate dehydrogenase (LDH) assay. The oxidative stress levels were determined respectively through reactive oxygen species (ROS), the intracellular levels of glutathione (GSH), superoxide dismutase (SOD) activity and malondialdehyde (MDA). The genotoxic effect was evaluated by DNA damage through comet assay.Results: (1)Compared to the control group, the pregnancy rates of rats exposed to nanomaterials were all significantly decreased; the fetus number and body weight, body lengh, tail length of the fetus in Nano-ZnO group were significantly less than the control group and other particle groups.(2)PMEF cells exposed for 24 hours retracted in different degrees, which resulted in increased cell spaces and sparse arrangement; the increased intracellular particles obviously reduced cellular transparency. The toxic effect comparisons amid four nanomaterials were significantly distinct at different concentrations: at lower dosage levels, the cytotoxicity of Nano-CB and CNTs was greater than Nano-ZnO and Nano-SiO2; as dosage level ascended, the toxic effect of Nano-ZnO was increased most significantly. (3)Nano-ZnO induced much greater cytotoxicity than other nanoparticles. This was significantly in accordance with intracellular oxidative stress levels measured by GSH depletion, MDA production, SOD inhibition as well as reactive oxygen species (ROS) generation. (4)Compared with Nano-ZnO nanoparticles, CNTs was moderately cytotoxic but induced more DNA damage determined by the comet assay. Nano- SiO2 seemed to be less effective.Conclusions: Our results indicated that nanomaterials could exert adverse effect on the gestation of the pregnant rats and the intrauterine development of the fetus. Oxidative stress may be the one of the main mechanisms underlying embryotoxicity and cytotoxicity. The comparative analysis demonstrated that particle composition probably played a primary role in the toxic effects of different nanoparticles. However, the potential genotoxicity might be mostly attributed to particle characters of shape or structure.