Biodegradable and Renal-Clearable Hollow Porous Iron Oxide Nanoboxes for in Vivo Imaging

For in vivo imaging, it is important that imaging agents could be harmlessly eliminated from the body after performing their functions. Gadolinium-based magnetic resonance contrast agents have been suffering from low relaxivity, a potential risk of gadolinium deposition. The biocompatibility and biodegradability of γ-Fe2O3 nanoparticles render them promising as a potential candidate contrast agent for MRI applications. Herein, we develop a facile synthesis of biodegradable hollow porous iron oxide nanoboxes (HPIOs) with high r1 values and low r2/r1 ratios, allowing for superior contrast-enhanced T1 imaging. The zwitterionic dopamine sulfonate (ZDS) functionalized HPIOs (HPIOs@ZDS) could effectively avoid nonspecific protein adsorption and achieve controllable biodistribution. Furthermore, HPIOs@ZDS could be degraded into 4–5 nm fragments in the body and subsequently cleared by kidneys rapidly after magnetic resonance imaging, which significantly reduces potential long-term toxicity. These desirable features make HPIOs@ZDS a prominent T1 contrast agent for magnetic resonance angiography in vivo. These biodegradable and biocompatible HPIOs@ZDS holds great promise for highly sensitive and accurate detection of heart and vascular diseases in molecular imaging.