Superparamagnetic Nanoparticles Coated with Various Electric Charges and Structural Changes in α-Synuclein and β-Amyloid Proteins

Abstract

Alzheimer s and Parkinson s are the most common amyloid diseases in the world that can affect more than 30 million people worldwide. The main cause of this disease is the production of amyloid fibrils, which play an important role in the development of neurological diseases. In fact, the formation of these compounds initiates the fibrillation process in the brain. The two peptides derived from fibrils are β-amyloid and α- synuclein, which form plaques in the brain. Studies have shown that magnetic iron oxide superconducting nanoparticles (SPIONs) that contain iron oxide nuclei affect protein fibrillation. Therefore, in this study, we tested commercial SPION nanoparticles with different electric charges including positive (NH2) negative (COOH) and neutral (Plain) at different concentrations of 50, 25 and 100 g/ml of nanoparticles on fibril kinetics of proteins. We examined this by modifying the fluorescence emission of thioflavin T. The results showed that while lower concentrations of SPION (25 g/ml) caused immediate inhibition of fibrillation, higher concentrations (100 g/ml) increased the rate of fibrillation process. Considering the nanoparticle charge, it was observed that neutral-charged SPIONs and the highest concentration (100 g/ml) were able to speed up the fibrillation process significantly compared to negative or positive SPIONs. The amount of concentration is same. The difference between the fluorescence emission from the β-amyloid fibrillation process and the α-nucleoside-induced fibrillation with different applied loads and concentrations were statistically significant at p<0.05, which indicates that in addition to the presence of nanoparticles, The electrical charge that affects the monomeric proteins in the environment (in the nucleation phase) also affects the concentration of the nanoparticles on the protein compounds. Differences in fluorescence emission were also examined in each of the two types of proteins studied.