Long-circulating Gd2O3:Yb3+, Er3+ up-conversion nanoprobes as high-performance contrast agents for multi-modality imaging

Due to their unique electric, magnetic, and optical properties, engineered nanostructures have been applied to provide diagnostic, therapeutic, as well as prognostic information about the status of disease. In this study, we report a multifunctional nanoprobe based on PEGylated Gd2O3:Yb3+, Er3+ nanorods (denoted as PEG-UCNPs) for in vivo up-conversion luminescence (UCL), T1-enhanced magnetic resonance (MR), and X-ray computed tomography (CT) multi-modality imaging. A facile and large-scale hydrothermal system combining the merits of an in situ thermal decomposition method and a surface-modified approach is introduced to construct high-quality PEG-UCNPs. By grafting PEG molecules on the surface of PEG-UCNPs, the nanostructures possess excellent stability against in vivo environment and hold long blood circulation time. Cell-cytotoxicity assay, hemolyticity, as well as post-injection histology, hematology, and inflammation analysis further demonstrate their non-cytotoxic character and indicate further in vivo application. In detail, the capability of PEG-UCNPs as high-performance contrast agents for UCL/MR/CT imaging is evaluated successfully through small-animal experiments. Additionally, pharmacokinetics, biodistribution, and clearance route are studied after intravenous injection in a mouse model, reflecting their overall safety.