engleski

Oxidative stress response of Daphnia magna exposed to silver nanoparticles

Introduction Silver nanoparticles (AgNPs) are one of the most widely used engineered metal-based nanoparticles due to their catalytic, antimicrobial, and plasmonic properties. They can be found in many products, such as antimicrobial dressings and coatings of catheters, and odour free fabrics used in clothing. As a consequence of their widespread use, there is a great chance for environmental exposure to AgNPs leading to possible toxic effect on living organisms. Because of that, there is a need for environmentally relevant toxicity testing using the appropriate test species. Materials & Methods Daphnia magna, a standardized aquatic test organism in toxicology was used for determining oxidative stress biomarkers induced by exposure to various concentrations of AgNPs and Ag+. After 48 h of the exposure, the surviving neonates were used for measuring the activities of antioxidant enzymes catalase, superoxide dismutase, and the levels of reduced glutathione (GSH). Also, the production of reactive oxidative species (ROS) was determined using DCFH-DA and DHE staining. Conducting at least three repetitions, the data were reported as averages ± SD. Results The activity of catalase and the level of GSH were increased with increasing AgNP concentrations, indicating that AgNP induced ROS production in D. magna. The significant increase in GSH level was observed already at the 0.5 mg/L AgNP, while further increase followed a dose-response gradient, steeper than in the case of catalase activity. Significant increase in GSH level and catalase activity was measured up to the 0.1 and 0.01 mg/L Ag+ doses, respectively. There is a significant decrease in ROS levels after treatment with Ag+, while decrease in DCF fluorescence intensity was observed up to 5 mg/L AgNP. The same decrease was observed for DHE intensity. Superoxide dismutase activities in AgNP-exposed daphnids did not change comparing to controls, whereas these activities were insignificantly induced in the Ag+ treated groups. Conclusion The present biochemical results revealed decreased ROS level, increased GSH level and catalase activity, but not of SOD, after exposure of D. magna to AgNPs. Obtained data showed significantly different toxicity of nano and ionic form of Ag in the aquatic system, with Ag+ being more toxic to D. magna. This study provided strong evidence of the antioxidation mechanism and suggested that introduced nanomaterials can significantly affect the toxicity of nanoparticles on aquatic organisms.

Nanosilver; toxicity; Daphnia magna; oxidative stress

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