(735g) Constrained Growth of Magnetite Nanoparticles Via Artificial Biomineralization

Biomineralization is a process widely used in nature to direct the growth of inorganic structures such as bones, teeth, and shells, often leveraging the versatile nature of proteins to precisely direct the morphologies and crystal structures of these mineralized tissues. This work uses a biomimetic approach to replicate the formation of iron oxide nanoparticles by ferritin, an iron storage protein found in nearly all organisms, using a much simpler peptide system. Instead of a large and complex protein, we used a polyelectrolyte complex micelle, consisting of two oppositely charged polymer blocks that bind electrostatically to form a core, and a neutral hydrophilic block forming a corona; our micelle consists of PEG-b-polylysine and polyglutamic acid. When iron oxide synthesis is performed in the presence of these micelles, size-constrained Fe₃O₄ particles are produced and suspended in aqueous solution. Dynamic light scattering, electron microscopy, and small-angle x-ray scattering results confirm that the average particle diameter is below 100 nm and that the size distribution is monodisperse, which suggests that the oxide nanoparticles and peptides form a hybrid structure with the nanoparticle contained within the micelle. Furthermore, the particle morphology and stability in suspension can be tuned by adjusting parameters such as the concentration of reactants or type of polymers present (polyelectrolyte micelles or polyglutamic acid alone). Due to the magnetic properties of iron oxide, these particles could have diverse applications in memory storage devices, spintronics, and nanomedicine.