Effect Of Co-exposure To Fe₃O₄ Nanoparticles And Cadmium Ion On The Development Of Zebrafish Embryos

Nanomaterials have been widely used in medical,enviroment protection and other field as their superior performance and unique properties;however,it is unsure whether they are safety or not.Fe₃O₄nanoparticles(NPs)as a kind of magnetic nanomaterials which possess superparamagnetism and adsorbability,have been used as an awesome adsorbent material for waste water treatment.Cadmiun is a kind of heavy metal with high lethal,carcinogenic and teratogenic characteristics.A great deal of cadmium-containing sewage have been poured into ecological environment and caused serious pollution due to lack understanding of its danger in the past.Fe₃O₄ NPs have showed great perfomance in cadmiun-contained sewage treatment while query of security still exist.Zebrafish(Danio rerio)as a model animal,which is sensitive,efficient and economical,often used in toxicology test for evaluating water qualilty.Based on these,we used zebrafish embryos to evaluate the safety of Fe₃O₄ NPs co-exposure with cadmium ion(Cd²⁺).We choose Fe₃O₄ NPs of 20 nm particle size as testing materials,exposure dose of Fe₃O₄ NPs is 20,40 and 80 mg/L,and exposure dose of Cd²⁺(dissolved from Cd Ac₂.2H₂O)is 0.25,0.5 and 1 mg/L.Development level index such as survival rate,hatch rate,abnormal rate,heart rate and body length of zebrafish embryos,and autonomous activity frequency were determined to estimate the toxicity of Fe₃O₄ NPs co-exposure with Cd²⁺,we also inquiry mechanism from the angel of oxidative stress by testing Reactive Oxygen Species(ROS),Malondialdehyde(MDA)and Total antioxidant capacity(T-AOC)level.Results of experiments shown that,high dose(80 mg/L)of Fe₃O₄ NPs had high toxicity and synergistic effect or cooperative effect with Cd²⁺,which caused more serious oxidative damage to zebrafish embryos,affected their development process and reduced their autonomous activity.However,Low dose(20mg/L)Fe₃O₄ NPs is less toxic,and the co-exposure with low dose Cd²⁺(0.25 mg/L)has antagonistic effect,compared with the single treatment group,low-dose co-exposure of the two groups could improve the survival rate and hatching rate of embryos.The oxidative damage to organism is an important mechanism of zebrafish embryo development toxicity caused by combined exposure of Fe₃O₄ NPs and Cd²⁺.Our experiment also demostrate Cd²⁺can reduce the intake of iron in zebrasifh tissue.We took numerous photographs of abnomal developed embryos or larval,classified abnormalities types and statistics incident rate of different abnormalities in different test group,and found rare abnormal types such as foreign body neoplasm in the co-exposure group.According to our experiment,we believe that the safe concentration of Fe₃O₄ NPs in water should be less than 40 mg/L.If Fe₃O₄ NPs is used to treat wastewater containing cadmium,excessive concentration of Fe₃O₄ NPs should be avoided directly discharged into the water environment,or used Fe₃O₄ NPs should be recovered in time before discharging.