Atherosclerosis is a chronic inflammatory disease characterized by the formation of atherosclerotic plaques, while macrophages as key players in plaque progression and destabilization are promising targets for atherosclerotic plaque imaging. Contrast-enhanced magnetic resonance imaging (CE-MRI) has emerged as a powerful noninvasive imaging technique for the evaluation of atherosclerotic plaques within arterial walls. However, the visualization of macrophages within atherosclerotic plaques presents considerable challenges due to the intricate pathophysiology of the disease and the dynamic behavior of these cells. Biocompatible ferrite nanoparticles with diverse surface ligands possess the potential to exhibit distinct relaxivity and cellular affinity, enabling improved imaging capabilities for macrophages in atherosclerosis. In this work, we report macrophage-affinity nanoparticles for magnetic resonance imaging (MRI) of atherosclerosis via tailoring nanoparticle surface coating. The ultrasmall zinc ferrite nanoparticles (Zn0.4Fe2.6O4) as T1 contrast agents were synthesized and modified with dopamine, 3,4-dihydroxyhydrocinnamic acid, and phosphorylated polyethylene glycol to adjust their surface charges to be positively, negatively, and neutrally charged, respectively. In vitro MRI evaluation shows that the T1 relaxivity for different surface charged Zn0.4Fe2.6O4 nanoparticles was three higher than that of the clinically used Gd-DTPA. Furthermore, in vivo atherosclerotic plaque MR imaging indicates that positively charged Zn0.4Fe2.6O4 showed superior MRI efficacy on carotid atherosclerosis than the other two, which is ascribed to high affinity to macrophages of positively charged nanoparticles. This work provides improved diagnostic capability and a better understanding of the molecular imaging of atherosclerosis.
Keywords: atherosclerosis; macrophages; magnetic resonance imaging; tailoring nanoparticle surface coating; ultrasmall zinc ferrite nanoparticles.