In vivo imaging of Fe2+ using an easily obtained probe with a large Stokes shift and bright strong lipid droplet-targetable near-infrared fluorescence

Ferrous ions (Fe2+) play an irreplaceable role in living animals. However, the lack of effective Fe2+ probes has seriously hindered the further study of Fe2+ in vivo. An easily obtained reaction-based fluorescent probe DCI-Fe(II) for real-time detection and imaging of Fe2+ both in cells and in vivo was reported in this work. DCI-Fe(II) shows distinct changes in color and highly selective turn-on near-infrared (NIR) fluorescence (∼120-fold enhancement at 700 nm) for Fe2+ with a rapid response (5 min), high sensitivity (51 nM of detection limit), and a marked Stokes shift (195 nm). Moreover, DCI-Fe(II) proves to be readily applicable to visualize Fe2+ in lipid droplets of living cells. Further imaging of Fe2+ in vivo with DCI-Fe(II) was also successful, indicating that DCI-Fe(II) holds great potential to promote the research of Fe2+ in life systems.