Monodisperse transfer of superparamagnetic nanoparticles from non-polar solvent to aqueous phase

The use of superparamagnetic nanocrystals (MNPs) for biomedical applications generally requires a synthetic route in which the resultant MNPs are water soluble and biocompatible with good morphology and size distribution control, as well as optimized hydrodynamic size. To achieve this, hydrophobic MNPs are typically synthesized through the thermolysis process and thereafter water solubilized by using amphiphilic brush co-polymers. In this paper, two types of MNPs were synthesized, i.e. magnetite and manganese ferrite nanocrystals. We presented the optimization process of a water solubilization route by employing poly(isobutylene-alt-maleic anhydride) grafted with dodecylamine (PIMA-g-C12) as the coating. Several parameters that would lead to monodisperse phase transfer of the superparamagnetic nanocrystals (i.e. minimization of the overall MNPs hydrodynamic size) were investigated. These included the PIMA-g-C12/MNPs ratio, the amount of hydrolyzing agent and the initial MNPs concentration in non-polar organic solvent. Such PIMA-g-C12 coated MNPs were found to exhibit good colloidal stability (pH, temperature and kinetic stability). Lastly, PIMA-g-C12 coated MNPs also exhibited excellent in vitro biocompatibility when incubated with NIH/3T3 fibroblast and MCF-7 breast cancer cells.