Zr- and Hf-based nanoscale metal-organic frameworks as contrast agents for computed tomography.

Nanoscale metal-organic frameworks (NMOFs) of the UiO-66 structure containing high Zr (37 wt%) and Hf (57 wt%) content were synthesized and characterized, and their potential as contrast agents for X-ray computed tomography (CT) imaging was evaluated. Hf-NMOFs of different sizes were coated with silica and poly(ethylene glycol) (PEG) to enhance biocompatibility, and were used for in vivo CT imaging of mice, showing increased attenuation in the liver and spleen.