title: Toxicity of silver nanoparticles on the brain ofOreochromis niloticusandTilapia zillii.
abstract: BACKGROUND
  Silver nanoparticles (Ag-NPs) are widely used nowadays in a variety of commercial applications including medical, health care, textiles and household supplies.
  
  
  OBJECTIVE
  The current study was designed to determine the median lethal dose (LC50) of Ag-NPs onOreochromis niloticusandTilapia zillii.
  
  
  METHODS
  Acute and sub-acute toxicity study of the Ag-NPs on brain tissues was carried out using different concentrations of the NPs at 2 mg L and 4 mg L. These concentrations were dispersed in deionized water with the exception of the control groups in the experiments. Biochemical and molecular analysis were conducted on tissue homogenates in order to evaluate the potential effects of NPs on the antioxidant system.
  
  
  RESULTS
  The Ag-NP acute toxicity (96 h LC50) values of 19.5 ± 2 and 20 ± 2.4 mg/L were reported forO. niloticusandT. zilliirespectively. Fish exposed to 2 mg/L Ag-NPs did not show any significant change in the levels of reduced glutathione (GSH), total glutathione (tGSH) levels, superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) activity or genes expression and malondialdehyde (MDA) level. In contrary, a dose of 4 mg/L showed a significant reduction in the levels all the above-mentioned parameters except in MDA level where it was significantly induced.
  
  
  CONCLUSIONS
  Results indicate that exposure ofO. niloticusandT. zilliito Ag-NPs (4 mg/L) has deleterious effects on brain antioxidant system, whereas a dose of 2 mg/L has no effects.
authors.affiliation: Department of Biochemistry, Faculty of Veterinary Medicine, Zagazig University, Egypt; Department of Biological Sciences, Faculty of Science, University of Jeddah, Saudi Arabia.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Afifi
authors.affiliation: Department of Biological Sciences, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia.
authors.forename: Salina
authors.initials: S
authors.lastname: Saddick
authors.affiliation: Department of Biological Sciences, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia.
authors.forename: Osama A
authors.initials: OA
authors.lastname: Abu Zinada
keywords: Ag-NPs; Antioxidants; LC50; O. nilotica; T. zillii