Abstract
The increasing application of nanotechnology highlights the need to clarify and understand it. In this work, the subacute toxicity of Ag-NPs to the fresh water microalga Chlorella vulgaris and marine microalga Dunaliella tertiolecta were assessed. The effect of Ag-NPs was induced by exposing both algae to increasing concentrations of Ag-NPs (0, 10, 50, 100 and 200 mg/L). Cellular viability and reactive oxygen species (ROS) formation were determined to evaluate the toxic effect of Ag-NPs on algal growth. Superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities and lipid peroxidation (MDA) levels in the algal cells varied with the concentration of Ag-NPs suspensions and exposure times (up to 8 d). As a result, 100 and 200 mg/L Ag-NPs caused a statistically significant decrease in cell viability, as well as SOD, CAT and POD activities, and a significant increase in ROS formation and MDA levels in tissues (P<0.05), suggesting that the algal cells exposed to these two concentrations of Ag-NPs suffered from oxidative stress. The extent of depletion of antioxidant enzyme activities and the elevation of MDA in Dunaliella tertiolecta was the greatest, indicating that Dunaliella tertiolecta might be the most susceptible to Ag-NP exposure. These results indicated a potential risk from Ag-NPs released into the aqueous environment.