Iridium(III) complexes as therapeutic and bioimaging reagents for cellular applications

There is an emerging interest in applying inorganic and organometallic transition metal complexes to biomolecular and cellular studies. The cytotoxic effects of these complexes on various cancer and normal cells have been examined. Many of these complexes display intense, long-lived, and environment-sensitive emission, rendering them useful live-cell imaging reagents. Of particular interest are iridium(III) complexes, which possess a diversity of molecular structures with intriguing biological activity and photophysical properties. In this review article, we summarize recent work using iridium(III) complexes as anticancer drugs and cellular imaging reagents. We focus on the cytotoxic activity, cellular uptake efficiency and mechanisms, and intracellular distribution properties of these complexes. Additionally, we describe the applications of luminescent iridium(III) complexes in intracellular sensing for ions and small molecules, gene-delivery, and cancer cell detection. © 2012 The Royal Society of Chemistry.