Proline functionalized gold nanoparticles modulates lysozyme fibrillation.

Amyloid fibrils are the hallmarks of neurodegenerative diseases like Alzheimer's, Parkinson's and other proteopathies. Inhibition of fibrillation is a potential strategy to check the progress of amyloid associated diseases and further allied deterioration. In this study, we have synthesized proline functionalized gold nanoparticles (Pro-AuNPs) and scrutinized its antifibrillation property towards Hen Egg White Lysozyme (HEWL) aggregation. Pro-AuNPs were characterized using various biophysical methods like ultraviolet-visible spectroscopy, fourier transform infra-red spectroscopy, zeta potential measurement, dynamic light scattering and transmission electron microscopy. The effect of Pro-AuNPs on HEWL fibrillation was analyzed employing thioflavin T (ThT) and 8-Anilino-1-naphthalenesulfonic acid (ANS) assays. The kinetics of HEWL exhibited a typical sigmoidal nature of protein aggregation and was fitted to Boltzmann model. HEWL in the presence of bare gold nanoparticles (bAuNPs) exhibited similar aggregation kinetics as HEWL alone. However, HEWL fibrillation substantially reduced upon co-incubation with proline and Pro-AuNPs, and two slightly different intermediate species were formed with these two systems as predicted by CD spectroscopy. TEM images also supported the above observation displaying different morphological states of HEWL aggregates in the presence of proline and Pro-AuNPs. Using computational methods, the nature of interaction of HEWL and proline was found to be hydrogen bonding and hydrophobic interaction in multiple amyloidogenic regions. These interactions inhibited the formation of prefibrils (β-sheet rich intermediates) and also found to disintegrate fibrils. Furthermore, HEWL-Pro-AuNPs system resulted HEWL adsorption through hydrophobic patches, which blocked the intermolecular β-sheet formation. The present study successfully established Pro-AuNPs as a potential inhibitor of HEWL aggregation.