Synthesis, properties, and endothelial progenitor cells labeling stability of dextranes as polymeric magnetic resonance imaging contrast agents.

Magnetic resonance imaging is one of the most important fields for cellular imaging due to its non-invasive capacity, spatial resolution, and sensibility to visualized transplanted cells. An enhanced magnetic resonance image can be achieved by using contrast agents containing paramagnetic gadolinium chelates, which have the widest clinical use. To obtain a better contrast-enhancement and reduce the concentration of Gd for payload, one strategy is to conjugate the gadolinium(III) chelate to polymeric materials that will lead into an increase in the rotational correlation time and therefore improve the relaxivity. Four series of dextran gadolinium chelates were synthesized which are of interest as potential MRI contrast agents to track bone marrow-derived endothelial progenitor cells in vivo. The dextranes with molecular weights were characterized, introduced into the endothelial progenitor cells by electroporation, and injected in aqueous solution into rats to acquire the MR images. We have shown that by selecting polymers of the appropriate molecular weight, stability into the cell after labeling, relaxivity, and retention into the body can be accomplished.