Multifunctional nanoprobes for macrophage imaging.

Imaging and tracking macrophage behaviors in vivo are essential to reveal its biological function and fate in various diseases. Small molecular probes suffer from poor macrophage targeting and retention, rapid clearance, and deficient metabolizing stability. To overcome these limitations, a variety of functional nanoprobes have been developed for targeted imaging of macrophages in divergent diseases such as cancer, atherosclerosis and obesity. Generally, nanoprobes are functionalized with targeting peptides, ligands or antibodies to fulfill high macrophage affinity. In this review, the most recent advances of nanoprobes for imaging macrophages in vivo and ex vivo are systematically summarized. The challenges and perspectives of precisely imaging macrophages with improved signal-to-background ratios via nanoprobes are further discussed.