A rhodamine-6G-based "turn-on" fluorescent probe for selective detection of Fe³⁺ in living cells

A new fluorescent probe R6GES based on rhodamine 6G was designed and synthesized for the detection of Fe³⁺. The Fe³⁺ irreversibly binds to the R6GES and induces the ring opening and hydrolyzing of the spirolactam in the rhodamine unit. In the case of other biologically relevant metal ions, including Al³⁺, Na⁺, K⁺, Li⁺, Ag⁺, Cu²⁺, Mg²⁺, Zn²⁺, Co²⁺, Fe²⁺, Cd²⁺, Ni²⁺, Mn²⁺, Ba²⁺, Ca²⁺ and Hg²⁺, a negligible change was observed under similar conditions. These results indicate that probe R6GES can be used for the detection of Fe³⁺ without interference from other competitive metal ions. The tested concentration range and the limit of detection (LOD) of the probe were 0-30.00 μmol L^-1 and 0.030 μmol L^-1, respectively. The present probe was applied to the determination of Fe³⁺ in drinking water samples. The average recoveries ranged from 102.40% to 104.55% at a spiked concentration level of 20.00 μmol L^-1, and the obtained results were consistent with those obtained using atomic absorption spectrometry (AAS). Furthermore, the fluorescent probe can also be applied as a bioimaging reagent for Fe³⁺ detection in BEL-7402 cells.