Superparamagnetic Iron Oxide Nanoparticles Stabilized with Multidentate Block Copolymers for Optimal Vascular Contrast in T1-Weighted Magnetic Resonance Imaging

Ultra-small superparamagnetic iron oxide nanoparticles (USPIOs) have been used as vascular contrast agents in magnetic resonance imaging (MRI), mainly for their capacity to generate negative contrast. To use USPIOs as positive contrast agents, it is necessary to achieve increased colloidal stability and signal-enhancement performance. Their molecular coatings must be carefully chosen so the vascular blood-pool contrast agents must lead to long blood turnover times. However, to avoid long-term toxicological effects, they must also be cleared rapidly through the urinary or the gastrointestinal pathways. In this context, highly stable USPIOs showing “positive” contrast in MRI and optimal clearance rates, call for the development of robust biocompatible molecular coatings. In the present study, USPIOs were stabilized with multidentate block copolymer (MDBC), using a one-pot polyol synthesis method in the presence of MDBC. Two types of MDBC having pendant COOH groups in the anchoring block were developed: a po...