Influence of Au nanoparticles on the aggregation of amyloid-β-(25-35) peptides

The influence of Au nanoparticles (Au NPs) on the aggregation of amyloid-β-(25-35) peptides (Aβ25-35) is investigated by atomic force microscopy and Thioflavin T fluorescence measurements. It is found that, without Au NPs, the Aβ25-35 peptides aggregate gradually from monomers and oligomers to long fibrils with the incubation time. In contrast, short protofibrils are formed quickly after Au NPs are added to the Aβ25-35 solution, which can be further aggregated to form short fibril bundles or even bundle conjunctions. To reveal the origin of Au NPs on the aggregation of Aβ25-35, electrostatic force microscopy and scanning Kelvin microscopy are employed to investigate the electrical properties of the Aβ25-35 fibrils with and without Au NPs. Due to the significant difference of the electrical properties between the Aβ25-35 fibrils and Au NPs, the locations of Au NPs inside the Aβ25-35 fibril bundles can be revealed and hence a possible influence mechanism of Au NPs on the aggregation of Aβ25-35 is suggested.