Effect of Polyvinylpyrrolidone (PVP) functionalized gold nanoparticles on hen Egg-white lysozyme (HEWL) amyloids: An inhibition and disaggregation study

Abstract

Protein amyloids are characterized by aggregates that usually consist of fibres containing misfolded proteins having a β-sheet conformation. Such protein amyloids are associated with several degenerative diseases like Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS) and prion diseases. Studies on the effect of nanoparticles on protein amyloids have gained considerable research interest over the past two decades. The present study describes the effect of chemically synthesized Polyvinyl pyrrolidone (PVP) conjugated gold nanoparticles (PVP-AuNps) on Hen egg white lysozyme (HEWL) amyloids. Lysozyme amyloids occur in individuals suffering from a familial non-neuropathic systemic amyloidosis. Due to high level of similarity in the sequence and structure of human lysozyme and hen egg-white lysozyme (HEWL), studies have been conducted in HEWL. The synthesized nanoparticles have been characterized using various biophysical techniques like UV-Vis Spectroscopy, image analysis by TEM(Transmission Electron Microscopy), XRD(X-Ray Diffraction) analysis, particle size measurement by DLS(Dynamic Light Scattering), Zeta-Potential measurement and FTIR(Fourier-Transform IR Spectroscopy).An inhibition and disaggregation study was performed on nanoparticle incubated Hen egg white Lysozyme(HEWL) amyloids by performing various spectrofluorometric assays like Thioflavin-T and ANS binding assays. Also, the change in the secondary structures during amyloid formation was characterized using CD (Circular Dichroism Spectroscopy). Microscopic characterisation of the amyloids was done using fluorescence microscopy and Atomic Force Microscopy (AFM). A computational study was also done to predict whether PVP binds to the amyloidogenic regions of the protein. Finally it was found that PVP acts as an inhibitor of amyloids. However when conjugated to nanoparticle surface leads to complete inhibition of amyloid formation. PVP conjugated gold nanoparticles can therefore act as an effective therapeutic agent against the disease hereditary systemic amyloidosis. Also, further research can be carried out to find its effect on other protein misfolding disorders.