Reaction-Based “Off–On” Fluorescent Probe Enabling Detection of Endogenous Labile Fe2+ and Imaging of Zn2+-induced Fe2+ Flux in Living Cells and Elevated Fe2+ in Ischemic Stroke

Fluorogenic sensors capable of spatiotemporally detecting Fe2+ in biological systems are highly valuable in the study of iron biology. Toward this end, a new “off–on” Fe2+-selective fluorescent probe has been developed by incorporating an Fe2+-induced N–O cleavage of acylated hydroxylamine moiety into the naphthalimide fluorophore. The probe displays facile response (within 15 min) and good selectivity toward Fe2+ with >27-fold enhancement of fluorescence intensity and high sensitivity of as low as 0.5 μM with a noticeable 3-fold fluorescence enhancement. These features of the probe have been transformed into in the convenient detection of endogenous, basal level of labile Fe2+ pools in living cells. Furthermore, we have demonstrated the capacity of the probe for the studies of important Fe2+ related biological functions. It can respond to the Zn2+-induced Fe2+ flux, an important event observed in stroke, and facilely detect the elevated level of Fe2+ in the brain tissue of a rat undergoing ischemic stroke at the ischemic site.