The biodistribution of nanoparticles becomes a critical concern for further clinical translation. Recent studies have demonstrated that, in addition to the liver and spleen, bone also plays a crucial role in nanoparticle distribution following systemic administration. However, the factors influencing the accumulation of nanoparticles in skeletal tissues remain unclear. We conducted an investigation into the distribution and retention of rare-earth nanocrystals with varying sizes and surface modifications using in vivo near-infrared IIb imaging. The findings revealed that within a few minutes after intravenous injection, the rare earth nanocrystals were swiftly concentrated in the bone marrow through the vascular system. Furthermore, there was a more pronounced accumulation observed for nanocrystals possessing carboxyl groups and smaller dimensions. Notably, the PEG-modified nanocrystals exhibit enhanced stability and biocompatibility, rendering them an ideal candidate for bone marrow imaging. This study lays a foundation for the development of nanoagents targeting bone-related diseases and elucidates some of the mechanisms underlying nanoparticles retention in the bone marrow.
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