Recent progress in rational design of fluorescent probes for Fe2+ and bioapplication

Iron is the most abundant transition metal ion in the human body. It has unique redox activity and plays an important role in maintaining the normal function of cells. However, excessive iron produces highly reactive oxygen, which is harmful to organisms and can even cause cell damage or ferroptosis. The intracellular iron ion, especially Fe2+ which is not bound or weakly bound to the protein, has greater influence on the cellular function, and its metabolic abnormality is implicated in occurrence of a series of critical diseases. Detection the Fe2+ is of great demand for the investigation of aberrant iron related diseases. To this end, researchers have designed various fluorescent probes that can monitor Fe2+ in vitro and in vivo which substantially the accelerates the investigation and understanding of Fe2+ related diseases. In this review we summarize and classify Fe2+ fluorescent probes based on their different interaction mechanism with Fe2+, and introduce their applications in bioimaging, so as to provide clues for developing more reliable and applicable Fe2+ probes.