Effect of nanoparticles on the aggregation and amyloid formation of amyloid-beta peptide.

Abstract

Nanoparticles are becoming more and more important in medicine and biotechnology. Moreover, due to environmental pollution, the human body is exposed to nanoparticles in the everyday life. Nanomaterials can also affect the aggregation processes of proteins. The Aβ peptides are known for forming amyloid aggregates in the brain in Alzheimer's disease. We used in-house expressed recombinant Aβ(1-42) to study the structure, aggregation kinetics and cytotoxicity of the peptide. We characterized nanoparticles of different materials and studied their effects on the structure and aggregation of Aβ. We followed amyloid formation by monitoring Thioflavin T fluorescence in the presence of nanoparticles. We observed that nanoparticles typically reduce the lag time of aggregation. We found that polystyrene particles bind monomers to a certain saturation point and allow only excess monomers to form fibrils. Calcium fluoride (CaF2) nanoparticles do not bind monomers in a similar fashion, but do influence the secondary structure composition of the resulting amyloid fibrils. We used CD spectroscopy and the BeStSel method to determine the secondary structure composition of the different forms of Aβ. While the main characteristics of Aβ fibrils formed alone is parallel β-sheet, in the presence of CaF2, Aβ forms significant amount of antiparallel β-structure as well. We also conducted cytotoxicity experiments to investigate if nanoparticles alter the toxic effect of Aβ on mouse hippocampal cells. Our preliminary findings suggest that studied particles might reduce cytotoxicity of Aβ if applied in very low concentrations.