Gold Nanoparticles as a Probe for Amyloid-β Oligomer and Amyloid Formation.

The process of amyloid-β (Aβ) amyloid formation is pathologically linked to Alzheimer's disease (AD). The identification of Aβ amyloids and intermediates that are crucial players in the pathology of AD is critical for exploring the underlying mechanism of Aβ aggregation and the diagnosis of the disease. Herein, we performed a gold nanoparticle (AuNP)-based study to detect the formation of Aβ amyloid fibrils and oligomers. Our results demonstrate that the intensity of the surface plasmon resonance (SPR) absorption band of the AuNPs is sensitive to the quantity of Aβ40 amyloids. This allows the SPR assay to be used for detection and semi-quantification of Aβ40 amyloids, and characterization of the kinetics of Aβ amyloid formation. Furthermore, our study demonstrates that the SPR band intensity of the AuNPs is sensitive to the presence of oligomers of both Aβ40 and an Aβ40 mutant, which forms more stable oligomers. The kinetics of the stable oligomer formation of the Aβ40 mutant can also be monitored following the SPR band intensity change of AuNPs. Our results indicate that this nanoparticle based method can be used for mechanistic studies of early protein self-assembly and fibrillogenesis.