Adsorption and separation of amyloid beta aggregates using ferromagnetic nanoparticles coated with charged polymer brushes.

Amyloid beta (Aβ) protein aggregates, which include fibrils and oligomers, are neurotoxic and are considered to cause Alzheimer's disease. Thus, separation of these Aβ aggregates from biological samples is important. Herein, we report the use of strongly ferromagnetic few-layer graphene-coated magnetic nanoparticles (C/Co), which were functionalized with a cationic polymer, poly[3-(methacryloyl amino)propyl]trimethylammonium chloride (polyMAPTAC), C/Co@polyMAPTAC, for the adsorption and magnetic separation of Aβ aggregates. Fast adsorption (∼1 min) of Aβ fibrils and oligomers onto the particles was observed. Interestingly, the Aβ monomer was not captured by the particles, suggesting that binding to Aβ molecules is toxic species-selective. Selective adsorption was also observed in the presence of serum albumin protein. We also showed that C/Co@polyMAPTAC could reduce the cytotoxicity of the Aβ aggregate solutions. This study should be useful for further elucidation of the application of nanoparticle adsorption in mediating Aβ toxicity.