Emerging engineered magnetic nanoparticulate probes for targeted MRI of atherosclerotic plaque macrophages

Inflammation is known to present at all stages of atherosclerotic lesion/plaque development, which often progresses silently for decades, before the occurrence of acute clinical events. Rupture of mature complex plaques with ongoing inflammation can lead to thrombosis, and many adverse acute clinical events such as stroke, myocardial infarction and/or sudden coronary death. Among new-generation noninvasive imaging modalities, molecular MRI with target-specific novel nanoparticulate contrast agents has shown great promise for the visualization of atherosclerosis at the molecular and cellular level in both animals and humans. Considering the key role macrophages play in atherosclerotic inflammation from lesion initiation to plaque rupture, this article reviews the recently engineered magnetic nanoparticulate probes targeting macrophages, their phagocytic activities, surface receptors and molecular products such as neutrophil gelatinase-associated lipocalin. The usefulness of some of these probes as multimodal and drug monitoring agents is also reviewed along with the challenges and future perspectives of the present developments for clinical benefit.