PEG modified BaGdF₅:Yb/Er nanoprobes for multi-modal upconversion fluorescent, in vivo X-ray computed tomography and biomagnetic imaging.

Herein, a multi-functional nanoprobe of polyethylene glycol (PEG) modified BaGdF₅:Yb/Er upconversion nanoparticles (UCNPs) for tri-modal bioimaging of fluorescence, computed X-ray tomography (CT), and magnetic application is demonstrated for the first time. The PEG-modified BaGdF₅:Yb/Er UCNPs with optimal small size were synthesized by a facile one-pot hydrothermal method. The as-designed single-phase nanoprobe presents near-infrared to visible upconversion emissions in UC fluorescent bioimaging of HeLa cell. Importantly, we have demonstrated in vivo CT images with enhanced signals of spleen of a mouse for 2 h, indicating the UCNPs can be successfully used as CT contrast agent for improving the detection of splenic diseases. In addition, these UCNPs also exhibit excellent intrinsic paramagnetic property which can be also for magnetic imaging. Therefore, our results indicate that a tri-modal nanoprobe served as fluorescent/CT/magnetic bioimaging can be realized using the PEG-modified BaGdF₅:Yb/Er UCNPs with very low cytotoxicity and long circulation time, which would be very useful in a variety of biomedical application fields.