Toxic Effects Of Liposome-encapsulated Silver (AgNPs、Ag~+) On Daphnia Magna

Silver is a widely used metal material that will inevitably leak into the environment during production,use and disposal,affecting the safety of the ecological environment.Although the literature has reported the toxicity of silver（nanosilver,silver ion）to Daphnia magna,most studies use direct water exposure,in which silver（nanosilver,silver ions）can affect Daphnia magna by affecting ionic components in algae（Daphnia magna food）and water environments.In this study,the following main results were obtained by comparing the acute and chronic toxic effects of silver（nanosilver,silver ion）on Daphnia magna before and after encapsulation by liposomes:（1）The citric acid-coated nanosilver（AgNPs）were prepared by the reduction method.The particles were round and dispersed relatively uniformly,and the particle size was50.0±0.4 nm.Nanosilver liposomes（lipid-AgNPs）and silver ion liposomes（lipid-Ag⁺）satisfying the Daphnia magna feeding range（0.6⁴0mm）were prepared by film dispersion method,and their particle sizes were 616.7±10.1 nm and 1852.8±42.4 nm,respectively.（2）There is a dose-effect relationship between AgNPs and lipid-AgNPs on the inhibition rate of Daphnia magna.The inhibition rate of Daphnia magna increased with increasing concentration,and the toxicity of AgNPs was higher than that of lipid-AgNPs.The 24-hour half-inhibitory concentration(24h-EC₅₀)of Daphnia magna was 0.084 mg/L and 0.174 mg/L,respectively,and the 48-hour half-death concentration(48h-LC₅₀)of Daphnia magna was 0.078 mg/L and 0.169 mg/L,respectively.AgNPs and lipid-AgNPs affected the reproduction of Daphnia magna,mainly delaying the first breeding time of Daphnia magna,and the high concentration group（0.019 mg/L and 0.029 mg/L）of AgNPs significantly prolonged the first brooding time of Daphnia magna（P<0.05）.Both AgNPs and lipid-AgNPs inhibit the superoxide dismutase（SOD）,glutathione peroxidase（GSH-Px）and lactate dehydrogenase（LDH）of Daphnia magna,affecting the energy supply of the body and antioxidant defense system.（3）There is a dose-effect relationship between Ag⁺and lipid-Ag⁺on the inhibition rate of Daphnia magna.The inhibition rate of Daphnia magna increased with increasing concentration,and the toxicity of Ag⁺was higher than that of lipid-Ag⁺.The 24h-EC₅₀ of Daphnia magna was 0.622 mg/L and 2.205 mg/L,respectively,and the 48h-LC₅₀ of Daphnia magna was 0.512 mg/L and 2.230 mg/L,respectively.Ag⁺and lipid-Ag⁺affected the growth and reproduction of Daphnia magna,which was reflected in reducing the number of peeling,delaying the time of the first breeding,reducing the number of first birth and inhibition the innate rate of increase.In the intermediate concentration group（0.0130⁰.050 mg/L）,the time of the first breeding of the Daphnia magna in the lipid-Ag⁺group was significantly earlier than that of Ag⁺（P<0.05）,and the innate rate of increase of the Daphnia magna in the lipid-Ag⁺group was significantly higher than that of Ag⁺（P<0.05）.Ag⁺and lipid-Ag⁺significantly inhibited SOD,GSH-Px and LDH in Daphnia magna（P<0.05）,affecting the body’s energy supply and antioxidant defense system,and the GSH-Px activity in Ag⁺group was significantly lower than that in lipid-Ag⁺（P<0.05）.