Graphene Oxide Quantum Dot Alters Amyloidogenicity of Hen Egg White Lysozyme via Modulation of Protein Surface Character.

A series of neurodegenerative disorders are caused by intracellular or extracellular amyloid deposition, including Alzheimer's disease, Parkinson's disease, Prion disease, and so on. To prevent the progress of such amyloid-mediated disorders, various agents have been tested including nanoparticles. Among different nanomaterials, graphene oxide shows unique electrochemical properties, which have potential applications in various biomedical fields. In our present investigation, we explored the effect of graphene oxide quantum dots (GOQDs) in amyloid β-fibrillation of hen egg white lysozyme (HEWL) under various conditions. Electron microscopy imaging showed that administration of GOQD inhibited HEWL amyloid β-fibrillation via producing thin and small fragments of fibrils. ζ-Potential measurement and 8-anilino-1-naphthalenesulfonic fluorescence study of lysozyme amyloid demonstrated a significant drop in surface hydrophobicity and an increase of surface charge of protein molecules. The reduced hydrophobic interaction and enhanced surface charge inhibit the hydrophobic assembly and colloidal stability of the protein. Circular dichroism and thioflavin-T fluorescence demonstrated that GOQD also interfered at the secondary structure level and prevented amyloid β-sheet formation and assembly of a protein by reducing the amount of amyloid β-sheet formation. Further, cellular toxicity analysis with HaCaT and 3T3 cells showed reduced toxicity of amyloid samples prepared with GOQD. Therefore, GOQD might be used to be a potential amyloid-preventive agent in various neurodegenerative diseases.