Engineered Iron-Oxide-Based Nanoparticles as Enhanced T1 Contrast Agents for Efficient Tumor Imaging

We report the design and synthesis of small-sized zwitterion-coated gadolinium-embedded iron oxide (Gd10) nanopartides, which exhibit a strong 71 contrast effect for tumor imaging through enhanced permeation and retention effect and the ability to clear out of the body in living subjects. The combination of spincanting effects and the collection of gadolinium species within small-sized Gd10 nanoparticles led to a significantly enhanced 71 contrast effect. For example, Gd10 nanoparticles with a diameter of similar to 4.8 nm exhibited a high r(1), relaxivity of 7.85 mM(-1) S-1 and a low r(2)/r(1) ratio of 5.24. After being coated with zwitterionic dopamine sulfonate molecules, the 4.8 nm Gd10 nanoparticles showed a steady hydrodynamic diameter (similar to 5.2 nm) in both PBS buffer and fetal bovine serum solution, indicating a low nonspecific protein absorption. This study provides a valuable strategy for the design of highly sensitive iron-oxide-based T-1 contrast agents with relatively long circulation half-lives (similar to 50 min), efficient tumor passive targeting (SKOV3, human ovarian cancer xenograft tumor as a model), and the possibility of rapid renal clearance after tumor imaging.