Application of radical dendrimers as organic radical contrast agents for magnetic resonance imaging

To develop metal-free magnetic resonance imaging (MRI) contrast agents, organic radical based contrast agents have been proposed as a promising alternative to obtain less toxic and safer MRI contrast agents. However, the low relaxivity and rapid in vivo reduction have limited the application of organic radicals as MRI contrast agents. As a special class of polymer, dendrimers with three-dimensional molecular structure and multiple tunable functional groups on surface, enable the facile chemical modification with organic radicals. With dendrimer as scaffold, a considerable amount of effort has been made to develop completely organic contrast agents. Herein, this mini review reports the recent advances of contrast agents with dendrimers as scaffold functionalized with radicals on the surface.