Effect of maghemite nanoparticles on insulin amyloid fibril formation: selective labeling, kinetics, and fibril removal by a magnetic field.

Maghemite (gamma-Fe(2)O(3)) magnetic nanoparticles of 15.0 +/- 2.1 nm were formed by nucleation followed by controlled growth of maghemite thin films on gelatin-iron oxide nuclei. Human insulin amyloid fibrils were formed by incubating the monomeric insulin dissolved in aqueous continuous phase at pH 1.6 and 65 degrees C. Magnetic human insulin amyloid fibrils/gamma-Fe(2)O(3) nanoparticle assemblies were prepared by interacting the gamma-Fe(2)O(3) nanoparticles with the insulin amyloid fibrils during or after their formation. The nanoparticles attached selectively to the insulin fibrils in both cases. The kinetics of the insulin fibrillation process in the absence and the presence of the gamma-Fe(2)O(3) nanoparticles was elucidated. The insulin amyloid fibrils/gamma-Fe(2)O(3) nanoparticle assemblies were easily extracted from the aqueous phase via a magnetic field. We hypothesize that this selective extraction approach may also be applicable for the removal of other amyloidogenic proteins that lead to neurodegenerative diseases (e.g., Alzheimer's, Parkinson's, Huntington's, mad cow, and prion diseases) from their continuous phase, e.g. milk, blood, neurological fluid, etc.