Silver nanoparticles (AgNPs) find application in the manufacturing of industrial, household and diagnostic products, besides its extensive antimicrobial use. While the economic benefits of manufacturing such materials are highly promising, their adverse environmental and health effects are yet to be fully realized. The unique physico-chemical properties of AgNP influence its ability to aerosolize, and thus occupational or environmental exposure is of major concern. To determine if AgNPs pose a neurological risk, we evaluated its effects in a rodent model. Well characterized AgNP (primary particle size = 20-50 nm) suspensions were prepared in dispersion medium (DM; mean particle aggregate size in DM = 180 nm). Adult male Sprague-Dawley rats were intra-tracheally instilled with a single dose of either DM, 37.5, 112.5 or 450 ug AgNP. At 1, 7, 28, or 84d post-exposure, various indices of neural dysfunction we examined in discrete brain areas. By 7d post-exposure, AgNPs caused a partial loss (35-40%) of striatal synaptosomal-associated protein 25 (Snap 25) and syntaxin binding protein 1 (Stxbp 1), critical molecular regulators of synaptic neurotransmission. Levels of Snap 25 decreased further (-85%) by 84d post-exposure. AgNP also decreased (-25%) serotonin content by 28d post-exposure. However, AgNP did not alter striatal dopamine content, although it reduced striatal Th. Reactive astrogliosis, as evidenced by the striatum, 7d following exposure. The persistent reduction of synaptic proteins 84d following cessation of exposure suggests that AgNPs can potentially be neurotoxic. Whether such abnormalities can culminate in neurodegeneration remains to be investigated. Our findings call for extensive safety evaluation to better understand the risks associated with AgNPs and avert any adverse neurological health effects.
Nanotechnology; Microbiology; Microchemistry; Environmental-exposure; Exposure-levels; Physiological-function; Physiological-effects; Physiology; Chemical-properties; Aerosols; Risk-factors; Laboratory-animals; Animals; Neurological-system; Neurological-reactions; Molecular-biology; Molecular-structure; Metal-compounds; Metallic-compounds; Workers; Neurotoxicity; Neurotoxic-effects; Neurological-system; Neurological-reactions; Toxicology
The Toxicologist. Society of Toxicology 52nd Annual Meeting and ToxExpo, March 10-14, 2013, San Antonio, Texas