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.
Highlights
Nanotechnology manipulates matter at a nanoscale properties have been exploited by certain groups (1-100 nm), producing nanoproducts and nanoma- commercializing colloidal silver suspensions as terials (NMs) that can have novel and size-related ‘health supplements’
It was reported that SiO2 and TiO2 exposure to dissolved silver ions and silver salts in NPs were able to interact directly with the algal cell fresh- and seawater organisms provides a baseline surface through adsorption to the cell walls (Van for assessment and a reason for concern; from this Hoecke et al, 2008; Sadiq et al, 2011)
The frozen cells were rinsed in 9-fold chilled 100 was grown in sterile BG-11 liquid medium and the mmol/L, pH 7.8 sodium phosphate buffer solution stock culture was aerated with bubbling air (Rippka and homogenized by a hand-driven glass homogeet al., 1979); Dunaliella tertiolecta was cultivated in nizer
Summary
(Kachynski et al, 2008). Silver is considered relatively harmless to humans. The environmental impacts of Ag-NPs are as Chlamydomonas reinhardtii formed large aggregates yet unknown. Oxidative stress is an important factor in nanoparticle-induced toxicity Antioxidant enzyme activities such as SOD, CAT and POD, are very sensitive to the stress of pollutants and can be used as an oxidativestress signal for an early warning of environmental pollution (Nel et al, 2006). We aimed to assess the effects of exposure of freshwater microalgae Chlorella vulgaris and marine microalgae Dunaliella tertiolecta to Ag-NPs. The subacute toxicity effects on the algae freshwater that will impact on the behavior of na- were examined, including physiological responses, noparticles and thereby the habitats or organisms by documenting the induction of ROS formation being exposed. As nanoparticles have a large surface area-tovolume ratio, it is thought that Ag-NPs react strong-
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