Neurotoxicity of Silica Nanoparticles: Brain Localization and Dopaminergic Neurons Damage Pathways

Silica nanopartides (SiO2-NPs) are being used increasingly in diagnosis, imaging, and drug delivery for the central nervous system. However, to date, little is known concerning the potential adverse effects on the brain associated with exposure to SiO2-NPs. The present study was conducted to trace, locate, and quantify SiO2-NPs in the brain by a radiolabeling approach after intranasal instillation with SiO2-NPs. The oxidative stress, inflammatory response, and levels of neurochemicals in the brain were also analyzed. Furthermore, in vitro studies were carried out to elucidate the pathway and mechanism of in vivo damage with a co-incubation model of dopaminergic neuron PC12 and SiO2-NPs. The results Indicated that SiO2-NPs via intranasal instillation entered into the brain and especially deposited in the striatum. Exposure to SiO2-NPs also induced oxidative damage and an increased inflammatory response in the striatum. Meanwhile, results of in vitro studies demonstrated that exposure to SiO2-NPs decreased cell viability, increased levels of lactate dehydrogenase, triggered oxidative stress, disturbed cell cycle, induced apoptosis, and activated the p53-mediated signaling pathway. In addition, the In vivo injury of neurochemicals occurred as the SiO2-NPs appeared to induce depleted dopamine in the striatum, and the downregulation of tyrosine hydroxylase protein was the main contribution. These data demonstrate that SiO2-NPs possibly have a negative impact on the striatum and dopaminergic neurons as well as a potential risk for neurodegenerative diseases. There is potential concern with SiO2-NPs' neurotoxicity In biomedical applications and occupational exposure In large-scale production.