A naked-eye visible and turn-on fluorescence probe for Fe3+ and its bioimaging application in living cells

A novel turn-on fluorescence probe based on rhodamine B for Fe3+ has been synthesized and characterized by various analytical techniques. Compared with other commonly coexisting metal ions, the probe showed 100-fold fluorescence enhancement for detecting Fe3+ with a 1:1 stoichiometry in MeOH/H2O (1:1, v/v) solution. After adding Fe3+, the rapid enhancement of fluorescence intensity provided a rapid method for detection of Fe3+. The color change was visible, so it could be used for naked-eye detection. The association constant between the probe and Fe3+ was detected to be 0.67 × 104 M−1 and the corresponding detection limit were calculated to be 5.7 × 10−8 M according to fluorescence titration analysis. The reversible binding of probe L to Fe3+ was confirmed by reacting with Na4P2O7, which captured the Fe3+ from the L-Fe3+complex and turned off the L-Fe3+complex. Fluorescence imaging experiments demonstrated that this probe was cell permeable and suitable for monitoring intracellular Fe3+ in living cells by confocal microscopy. What’s more, MTT assay indicated that this probe had no significant cytotoxicity to living cells.

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