Fluorescence Sensor for Hg^sup 2+^ and Fe^sup 3+^ ions using 3,3'–Dihydroxybenzidine:a–Cyclodextrin Supramolecular Complex: Characterization, in-silico and Cell Imaging Study

A sensitive and highly selective, fluorescent “turn–on” fluorescence sensor for Hg2+ and Fe3+ ions are reported by using an 3,3′–dihydroxybenzidine:α–cyclodextrin (DHB:α–CD) solid inclusion complex in an acetonitrile water system. Solid inclusion complex of DHB:α–CD was prepared by co-precipitation and kneading method and it was characterized by using FTIR, 1H NMR, XRD and SEM analysis. The investigation of fluorescence spectrum revealed that the host-guest system exhibited characteristic fluorescence behavior towards Hg2+ and Fe3+ ions in acetonitrile water system. With addition of Hg2+ and Fe3+, the host-guest system shows strong fluorescence enhancement, which resulted from the fluorophore of the coordination between DHB:α–CD and metal ions (Hg2+, Fe3+) with high binding constant (k = 3.1626 × 104 M−1, 1.8225 × 104 M−1). Moreover, high selectivity experiments revealed that the fluorescent sensor is specific to Hg2+ and Fe3+ ions even with interference from higher concentrations of other metal ions. Docked structure of DHB:α–CD (molecular docking studies) fully agree with experimental data. The molecular dynamic calculations show that there are structurally and energetically favourable association among the molecules, which are in good agreement with the experimental results. Further, bioimaging studies confirmed that the DHB:α–CD shows in vitro detection of Hg2+ and Fe3+ ions in HepG2 cells.