Metal-Organic-Frameworks as Contrast Agents in Magnetic Resonance Imaging

Metal-organic-frameworks (MOFs) are used either as drug carrying substrate for drug delivery or contrast agent for magnetic resonance imaging (MRI). MOFs are also playing a major role in harnessing dual or multiple modalities in therapeutic and diagnostic applications as a combined platform for both drug delivery and MRI contrast agents either as a T1- or T2- or combined T1- and T2-contrast agents for MRI image enhancement. This article presents an overview of the recent development of the modified and unmodified MOFs being used as MRI contrast agents and describes their biological evaluations, e.g., biocompatibility, bio-toxicity, in vitro and in vivo MRI cell imaging, and MRI image enhancement in animals. It illustrates vast diversities and complexities in developing these materials through complex designs and syntheses, types of MOFs being used, examinations of these MOFs-based materials for possible MRI contrast agents, types of MRI contrast agents, their functionalities and mechanism, in situ and in vivo MRI in cells and animals, and ranges of biological evaluations on the MOFs-based MRI contrast agents. Perspectives, insights, critical reflections, and future outlook are also presented.