Multifunctional Metal Complexes for Cancer Theranostics

Metal complexes can express multifunctionality via cooperativity between the metal center and a ligand, resulting in diagnostic functions, such as luminescent probes, contrast for magnetic resonance imaging (MRI), and photoacoustic (PA) imaging, and therapeutic functions, such as neutron capture therapy (NCT) and photothermal therapy (PTT). In some cases, both therapeutic and diagnostic functions can be attained by one metal complex species, leading to theranostic reagents. In view of the application of multifunctionality in cancer theranostics, selective delivery to tumors is indispensable. Here, we describe our strategy to develop multifunctional complexes coupled with nanotechnology to deliver complexes via enhanced permeability and retention effects. Examples include (1) lanthanide(III)-thiacalixarene complexes for luminescence, MRI, and Gd-NCT; (2) platinum(II)-diradical complexes for PA imaging and PTT; and (3) Mn(II)-metal organic framework (MOF)-74 as an MRI contrast agent, showing almost unlimited possibilities in nanomedicine strategies for cancer.