Effect of PEGylated superparamagnetic iron oxide nanoparticles (SPIONs) under magnetic field on amyloid beta fibrillation process.

Superparamagnetic iron oxide nanoparticles (SPIONs) with specific surface coatings have been shown appropriate potential in the diagnosis and treatment of various brain diseases such as Alzheimer's. Comprehensive understanding of SPIONs interactions with amyloid beta (Aβ) and other amyloidogenic proteins is essential for their clinical application. SPIONs could be delivered to the target tissue under the magnetic field, while they might be influenced by the applied field. In this work, we exhibit the effect of different SPIONs (magnetized or non-magnetized with different surface charges) on the kinetics of Aβ fibrillation in aqueous solution by the aid of ThT assay. The results showed that applying of magnetic field to the SPIONs influences on the Aβ fibrillation because of its effect on the size due to surface charge. It was found that under magnetic field and high concentrations of nanoparticles (SPIONs-PEG-NH2), the Aβ fibrillation process accelerates, while at lower concentrations the fibrillation is inhibited. Furthermore, the coating charge has a considerable role in fibrillation process and the positively charged SPIONs/magnetized, at lower particle concentrations, accelerate the fibrillation compared with the negatively charged or uncharged SPIONs. This hints that SPIONs with a positive charge have dual effects on the Aβ fibrillation process. They influence on the concentration of monomeric protein in solution and thereby the nucleation time. Also, SPIONs have an effect on binding during the protein conformation.