The Invisible Enemy: Nanoparticle Exposure and Neurodegenerative Decline

Atmospheric air pollution, specifically the ultra-fine fraction of particulate matter (PM2.5) known as nanoparticles (NPs), poses serious global health threats with critical neurological implications. This review summarizes evidence indicating that inhaled nanoparticles, particularly metallic nanoparticles (MNPs), can penetrate respiratory defense mechanisms and the blood-brain barrier (BBB). This enables direct translocation into the central nervous system (CNS). Once they enter the brain, these nanoparticles act as structural scaffolds, thereby accelerating the misfolding and aggregation of amyloid-beta (Aβ) peptides. This phenomenon has been identified as a pathological hallmark of Alzheimer's disease (AD). The underlying mechanisms involve chronic neuroinflammation and excessive reactive oxygen species (ROS) generation, leading to neuronal degeneration and cognitive decline. Significantly, the physicochemical properties that make nanoparticles potentially hazardous also present therapeutic possibilities. A notable example is the use of gold nanoparticles (AuNPs) to inhibit amyloid beta aggregation, which highlights the potential of nanomedicine for targeted neuroprotection.