STABILITY OF GOLD NANOPARTICLES AND THEIR INHIBITORY EFFECT ON AMYLOID-β1-42 PROTEIN AGGREGATION

Abstract

Aggregation of amyloid-β (Aβ) protein is known as the neurotoxicity involving in Alzheimer's disease (AD). Thus, prevention or reduction of Aβ aggregation would be a therapeutic strategy for AD. Gold nanoparticles (AuNPs) is considered to be a tool for AD treatment due to optical and biocompatible properties including ability to cross blood-brain barrier. In this study, citrate-stabilized AuNPs (AuCt) and polyethyleneimine-stabilized AuNPs (AuPEI) were synthesized and determined for their stability. Nanoparticle sizes of AuNPs were characterized by UV-vis spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS). The zeta potentials of AuNPs were determined by laser electrophoresis. The inhibitory effects of AuNPs on amyloid-β1-42 (Aβ1-42) aggregation and zinc-induced Aβ1-42 aggregation were examined using Thioflavin T fluorescence assay, and the appearance of aggregates were also observed under TEM. From the results, hydrodynamic diameters of AuCt and AuPEI obtained from DLS were 18.37 ± 0.34 nm and 18.59 ± 0.59 nm, respectively. The zeta potentials of AuCt and AuPEI were -35.37 ± 2.56 mV and 38.00 ± 1.68 mV, in orderly. Moreover, TEM analysis showed that AuPEI were smaller and less in size distribution than AuCt. After time storage, AuPEI were found to be more stable than AuCt. Both AuCt and AuPEI exhibited the inhibitory effect on Aβ1-42 aggregation and zinc-induced Aβ1-42 aggregation. However, AuCt had less inhibitory effect on the aggregation as compared to AuPEI. Increasing concentrations of AuCt and AuPEI AuNPS resulted in higher inhibitory effect on the aggregation. These results were in parallel with TEM images. Hence, the potential of AuNPs on inhibition of Aβ1-42 aggregation seemed to depend on the surface charges and concentrations of nanoparticles. The inhibitory mechanism of AuNPs on Aβ1-42 aggregates should be further clarified