Rhodamine probes for Fe3+: theoretical calculation for specific recognition and instant fluorescent bioimaging

Aim: To overcome the existing difficulty in distinguishing Fe(III) from Fe(II), rhodamine-containing Fe3+ probes, giving off different fluorescence responses to ferric and ferrous ions, were synthesized. Materials & methods: Color change in Fe3+ recognition, accompanying spirolactam opening-closing, could be used for 'naked-eye' detection. Theoretical calculations revealed the possible Fe3+-probe combination mechanism. Results: Apart from the probes' specific response toward Fe3+, the Fe3+-probe demonstrated highly quantitative relationships in fluorescence titration, instant labeling and dynamic tracking of intracellular Fe3+ in bioimaging. Conclusion: Cytotoxity and bioimaging in living L929 suggested the probes' future applications as real-time detection methods for Fe3+ in clinical diagnosis. Instant and time-lapse imagings, based on fluorescence-time stability of Fe3+-probe, enables the dynamic labeling and tracking of Fe3+ in living systems.