The Effect of Aqueous Solution of Silver Nanoparticles on Rat Behavior

Abstract: Silver nanoparticles (AgNP) are known to penetrate the brain and cause pathological changes in central nervous system (CNS) functions. Still, it remains unclear whether AgNP solutions as antimicrobial agents are safe for humans. The attempt was undertaken to assess the risk of commercial silver nanoparticles for CNS, using a rat as a model and creating conditions as close as possible to human intake of aqueous AgNP solutions. The silver nanoparticle solutions prepared with natural stabilizer were used, a low dosage (51 μg/kg), intake with drinking water, and long-time exposure. We determined the effect of the AgNP solution on some indices of animal behavior—motor activity, anxiety, and short-term habituation (non-associative learning)—1 and 2 months after the start of the consumption and three months after the AgNP withdrawal. After the 2-month course, rats showed (1) an increase in motor activity and a decrease in anxiety-phobic levels under a stressful environment of a classic open field test, (2) a lack of short-term habituation in the acoustic startle, and (3) presence of the nanoparticles in the hippocampus, frontal cortex, and striatum as detected by transmission electron microscopy. These signs disappeared three months after the AgNP withdrawal. The results suggest that under experimental conditions close to actual human consumption, silver nanoparticles do not have a long-term adverse effect on the CNS functions.