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 M 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.