Long-circulating Er3+-doped Yb2O3 up-conversion nanoparticle as an in vivo X-Ray CT imaging contrast agent

Nanoparticulate imaging agents offer excellent diagnostic and therapeutic capabilities due to their intense and stable output, strong target binding via multiple ligands, as well as tunable biodistribution profiles. In the present work, we designed and synthesized PEGylated Yb2O3:Er nanoparticles with high Yb content in single particle (denoted as PEG-UCNPs) suitable for both X-ray CT imaging and up-conversion imaging. These PEG-UCNPs were facile to construct, possessed excellent stability against in vivo environment, and held long blood circulation time. Cell-cytotoxicity assay, hemolyticity, and post-injection histology analysis further demonstrated the excellent biocompatibility, indicating the feasibilities of PEG-UCNPs for in vivo applications. Compared with routinely used Iobitridol in clinic, well-prepared PEG-UCNPs provided much significantly enhanced contrast at a clinical 120 kVp voltage. By doping 5% Er3+ into the nanoparticles, PEG-UCNPs presented a long-term stable and nearly single-band red up-conversion emission upon continuous irradiation with an assistant of a 980 laser. In addition, pharmacokinetics, biodistribution, as well as clearance of nanoparticles were studied after intravenous injection in a mouse model, reflecting their overall safety. PEG-UCNPs composed of intrinsic up-conversion luminescence property, higher X-ray absorption over Iobitridol, as well as excellent biocompatibility represented a nanoplatform for biomedicine applications.