Iron oxide-coated metal magnetic nanoparticles: improved magnetic properties and surface functionalization for biomedical applications

In recent years, the magnetic nanoparticles uses in many biomedical and biotechnological areas have received great attention due to their applications possibilities such as: tissue repair, diagnostics, magnetic resonance imaging, cancer treatment, cell separation, and controlled drug delivery, among others. Today, the magnetic nanoparticles applications are mainly based on magnetic iron oxides, which exhibit superparamagnetic behavior at room temperature and low saturation magnetization around 60 emu g-1. Magnetic oxide uses was based in two main reasons: easily and versatility of surface changes and functionalization due to hydroxyl groups present on the oxide nanoparticles surface, and low toxicity compared with the magnetic metallic nanoparticles. Biocompatibility and targetable functionalizations are generally obtained by paramagnetic and/or diamagnetic materials incorporations onto the nanoparticle surface contributing to decreases the already low oxide saturation magnetization. In this context, the development of new magnetic nuclei with high magnetizations values closed to the metallic iron values (~200 emu g-1) is required. However, this value is only generally observed in highly toxic metallic nanoparticles. Therefore, in this study, bimetallic magnetic nanoparticles of FePt, CoPt and NiPt coated with iron oxide and Ni- or Co-ferrites in a core-shell structure are synthesized by using the modified polyol process combined with the seed-mediated growth method. Obtained nanoparticles presented size and size distribution compatible for biomedical applications and the saturation magnetization of the different synthesized systems were enhanced compared with the pure magnetic oxide nanoparticles. Oleic acid and oleylamine present on the as-synthesized magnetic nanoparticles surface were properly changed by (3-aminopropyl)trimethoxysilane (APTMS) molecules leading to water-dispersible magnetic nanoparticles system. In addition, carboxymethyl-dextran molecules were conjugated with the APTMS molecules changing the nanoparticles surfaces and resulting in biocompatible water-soluble magnetic nanoparticles systems with improved magnetic response. These synthesized biocompatible magnetic systems present a great potential for many biomedical applications. (AU)