The Developmental Toxicity Study Of Nano-ZnO On Zebrafish Embryos

With the rapid development of nanotechnology, nanomaterials are widely usedin industrial production and daily life, inevitablely entering environment, which areharmful to human health and ecological environment. Based on the toxicity ofnanomaterials, we selected zebrafish embryos as biological subjects and the typicalnanostructured ZnO nanomaterials as object and assessed on the acute toxicity,oxidative stress and apoptosis of nano-ZnO comprehensively for the first time. Theperfect toxicology data of nano-ZnO provided scientific evidence for environmentalrisk assessment.Characterization results showed that nano-ZnO was well dispersed in theaqueous solution, and presented plate shape crystal. The graind iameter of nano-ZnOin1、20、50、100mg/L distribution was below100nm, which was suitable for thefollow experiment. The results of acute toxicity experiment showed that96h LC50of nano-ZnO was60mg/L. Zebrafish embryos survival rate, heart rate, hatching ratewere reduced as nano-ZnO exposure concentration increased. Although the bodyweight and body length were reduced, there was no significant difference comparedwith control. At the same time, nano-ZnO induced embryonic malformation, andmainly showed as pericardial edema, yolk sac edema and tail malformation. Inaddition, the Zn2+released from distribution (the soluble Zn2+) caused less toxiceffects in zebrafsh embryos and larvae.Antioxidant enzymes changed in concentration-effect and time-effect mannerafter nano-ZnO treated3-15days. MDA content was induced. The activities of SOD、CAT、GPX were first increased and then decreased with extension of exposure time,but nano-ZnO of30mg/L treatment group, SOD and CAT activities was sustainedinduced. Activities of antioxidant enzymes reached maximum respectively afternano-ZnO treated7and11days, showing that exposure to different concentrations,and antioxidant enzymes work time were different. Furthermore, the activities ofCAT and SOD changed in certain synchronic ity in7-15days. These results showedthat nano-ZnO caused oxidative stress effect on zebrafish embryos. Antioxidativestress gene results showed that Cu/Zn-Sod and Mn-Sod mRNA levels was notsignificant up-regulation. The mRNA levels of Cat and Gpx were significantlyup-regulated, especially for nano-ZnO of30mg/L exposure group, and mRNAexpression was increased8.1fold and15.8fold respectively.Staining with AO indicated that the nano-ZnO induced embryos apoptotic cellsand increased dose dependently, and considerable numbers of apoptotic cellsappeared around the heart. Nano-ZnO could induce ROS level rising. Flow cytometric analys is of apoptotic cells showed an apoptotic rate increased dosedependently, indicating that nano-ZnO could promote apoptosis. The genes of p53,Bax, caspase-3and caspase-9related to cell apoptosis were up-regulated afternano-ZnO treated. The enzyme activity of Caspase-3and Caspase-9were increased.After30mg/L nano-ZnOexposure, apoptosis enzyme activity increased by52.2%and40.4%in contrast with control group.