Influence of the separation procedure on the properties of magnetic nanoparticles: Gaining in vitro stability and T1-T2 magnetic resonance imaging performance.

Ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) coated with polyacrylic acid (PAA) were synthesized by a hydrothermal method in gram-scale quantity and extensively characterized. Only the nanoparticles subjected to an additional centrifugation step showed narrow size distribution, high polymeric coverage, and ideal superparamagnetism. In addition to improved physico-chemical properties, these nanoparticles feature high stability in vitro as well as dual T1-T2 performance as contrast agents (CAs) for magnetic resonance imaging (MRI), highlighting the importance of the additional separation step in obtaining material with the desired properties.