A Rhodamine Appended Iron-Recognizing Probe for On-Demand Theranostics in Anemic Drosophila

The development of functional organic molecules for advanced biological and environmental applications is of growing interest, particularly for metal ion sensing and therapeutic delivery. Rhodamine-based fluorescent compounds have been widely studied due to their well-defined absorption and emission properties. In this study, a rhodamine-appended fluorescent probe (RhB-A) was designed and synthesized, exhibiting strong fluorescence upon excitation at 400 nm. The probe demonstrates exceptional selectivity for Fe³⁺ ions, with significant fluorescence quenching even in the presence of 16 competing metal ions, with a LOD of 0.285 ppm in a semiaqueous medium, below the WHO guideline for iron in drinking water. Further, the Fe³⁺-coordinated complex was isolated as single crystals, confirming a 1:2 metal-to-ligand binding ratio. UV-Vis absorption studies further verified a reversible binding mechanism, supporting the probe's potential as a reusable sensor. Computational studies supported the ligand's reactivity and bioactivity, consistent with its experimental selectivity as a sensor. Importantly, the Fe³⁺ complex effectively treated lead-induced anemia in Drosophila melanogaster, delivering iron to deficient cells in a controlled and targeted manner. Thus, the designed fluorescent probe and its Fe³⁺ complex exhibited dual potential as a selective Fe³⁺ sensor and an anemia treatment agent.