A high affinity to skeleton rare earth doped nanoparticles for near-infrared II imaging

As a newly non-invasive emerging modality, NIR-II fluorescence imaging (1000-1700 nm) has many advantages over conventional visible and NIR-I imaging (700-900 nm). Unfortunately, few NIR-II fluorophores are suitable for bone imaging. Here, we report an NIR-II fluorophore based on DSPE-mPEG encapsulated rare earth doped nanoparticles (RENPs@DSPE-mPEG), which shows inherent affinity to bone without linking any targeting ligands, and thus it provides an alternative non-invasive and non-radiation strategy for skeletal system mapping and bone diseases diagnosis. Interestingly, within NIR-II window, imaging at longer wavelength (1345 nm) provides higher resolution and signal-to-noise ratio than that imaging at 1064 nm, even though quantum yield at 1064 nm is 2-fold higher than that at 1345 nm. Besides bone imaging, RENPs@DSPE-mPEG show imaging application in blood vessel and lymph node. Importantly, RENPs@DSPE-mPEG can be internalized by circulating white blood cells. This finding may open a window to increase ...