Neurotoxicity of nanoparticles entering the brain via sensory nerve-to-brain pathways: injuries and mechanisms

Nanoparticles induce neurotoxicity following inhalation, oral administration, intravenous administration, or injection. Different pathways have various corresponding characteristics. Among them, the sensory nerve-to-brain pathways, which are direct neural pathways, bypass barriers such as the blood–brain barrier, which prevents the entry of the majority of nanoparticles into the brain. Subsequently, nanoparticles exert effects on sensory neuroreceptors and sensory nerves, causing central neurotoxicity. However, no studies have summarized sensory nerve-to-brain pathways for transporting nanoparticles. Here, we review recent findings on the potential sensory nerve pathways that promote nanoparticle entry into the brain, the effects of NPs on sensory receptors and sensory nerves, the central neurotoxicity induced by nanoparticles via sensory nerve pathways, and the possible mechanisms underlying these effects. In addition, the limitations of current research and possible trends for future research are also discussed. In summary, we hope that this review will serve as a reference, inspire ideas for further research into the neurotoxicity of nanoparticles, and facilitate the development of protective measures and treatment schemes for nanoparticle-induced neurotoxicity.