Biochemical and Histopathological Alterations Induced by Sublethal Concentrations of Silver Nanoparticles and Silver Nitrate in the Nile tilapia (Oreochromis niloticus)

This study aimed to characterize the biochemical and histopathological alterations induced by sublethal concentrations of silver nanoparticles (AgNPs) and silver nitrate (AgNO₃) by determining their toxic effects on the Nile tilapia (Oreochromis niloticus). The investigation of growth performance revealed a decline in all measured parameters with increasing concentrations of AgNPs. Fish were exposed to non-lethal concentrations of AgNPs (10, 20, 50, and 100μg/ L) and to 100μg/ L of AgNO₃ for durations of 2, 4, and 6 weeks. Exposure to these sublethal concentrations resulted in a significant elevation (P< 0.05) in serum glucose, cholesterol, ALT, AST, uric acid, and urea levels compared to the control group. Conversely, total protein levels were significantly decreased (P< 0.05) in treated groups. The biochemical changes were more pronounced in fish exposed to AgNPs than in those exposed to silver nitrate, particularly at higher concentrations (50 and 100μg/ L) of AgNPs compared to the lowest concentration (10μg/ L). Histopathological examination revealed degeneration, necrosis, and hemosiderin accumulation in the epidermis, dermis, and muscle layers. Additional findings in the muscle layer included ballooning necrosis, covering cells, vascular infiltration, and edema. These pathological changes intensified with increasing concentrations and longer exposure durations.