The use of microgel iron oxide nanoparticles in studies of magnetic resonance relaxation and endothelial progenitor cell labelling

In vivo tracking of stem cells after transplantation is crucial for understanding cell-fate and therapeutic efficacy. By labelling stem cells with magnetic particles, they can be tracked by Magnetic Resonance Imaging (MRI). We previously demonstrated that microgel iron oxide nanoparticle (MGIO) provide superior tracking sensitivity over commercially available particles. Here, we describe the synthesis of MGIO and report on their morphology, hydrodynamic diameters (87–766 nm), iron oxide weight content (up to 82%) and magnetization characteristics (Ms = 52.9 Am2/kg, MR = 0.061 Am2/kg and Hc = 0.672 A/m). Their MR relaxation characteristics are comparable to those of theoretical models and represent the first such correlation between model and real particles of varying diameters. A labelling study of primary endothelial progenitor cells also confirms that MGIO is an efficient label regardless of cell type. The facile synthesis of MGIO makes it a useful tool for the studying of relaxation induced by magnetic particles and cellular tracking by MRI.