Mechanistic Insights of TiO 2 Nanoparticles with Different Surface Charges on Aβ 42 Peptide Early Aggregation: An In Vitro and In Silico Study.

Humans may intendedly or unintendedly be exposed to nanomaterials through food, water, and air. Upon exposure, nanomaterials can pierce the bloodstream and translocate to secondary organs, including the brain, which warrants increased concern for the potential health impacts of nanomaterials. Due to their large surface area and interaction energy, nanomaterials can adsorb surrounding proteins. The misfolding and self-aggregation of amyloid-β (Aβ) have been considered significant factors in the pathogenesis of Alzheimer's disease. We thus hypothesize that brain-targeted nanomaterials may modulate Aβ aggregation and cause related neurotoxicity. Here, we showed that TiO 2 nanoparticles (NPs) and their aminated analogue (TiO 2 -NH 2 NPs) adsorb the Aβ 42 peptide and accelerate its early oligomerization. Molecular dynamics simulation indicated that the adsorption onto TiO 2 NPs and TiO 2 -NH 2 NPs surfaces can stabilize the β-sheet-rich conformations formed by the Aβ 42 peptide. The binding sites between TiO 2 -NH 2 NPs and the Aβ 42 oligomer surface were mainly concentrated in the hydrophobic core region, and the β-sheet conformation spontaneously formed by Aβ 42 oligomers can be better stabilized through a hydrogen bond, electrostatic attraction, and hydrophobic interaction. This study will further help in the understanding of nanomaterial-related neurotoxicities and the regulation of their applications.