A reversible, benzothiazole-based “Turn-on” fluorescence sensor for selective detection of Zn2+ ions in vitro


Temperature-driven, highly sensitive and selective “TURN-ON” fluorometric detection of Zn2+ by benzothiazole-based probes (L1 and L2) was reported in physiological pH in the present work. Iron(II) acted as the reversible switch or trigger for the reversible detection of Zn2+ ions by the probes resulting in “TURN-OFF” fluorescence at room temperature. However, selective detection of Zn2+ in the presence of Fe2+ was irreversible at 0–5 °C. Such temperature dependence on reversible fluorometric detection of Zn2+ in the presence of Fe2+ was explained from the thermodynamic perspective as well as DFT calculations in which the absolute enthalpy (H) and Gibbs free energy (G) of the resultant complexes and the fluorophores (L1 and L2) at different temperatures were determined. Enhanced fluorescence of the Zn2+ bound probes was due to the inhibition of excited-state intramolecular proton transfer (ESIPT). Effect of solvents, pH, and temperature on the fluorometric detection of Zn2+ was also probed in the present work. The results were translated into the visual detection of Zn2+ on paper-based fluorescence probe and later we demonstrated the sensing of mobile Zn2+ ions by the probes in living HeLa cells as the proof of concept of our present investigations.

Graphic Abstract

A benzothiazole-based, “TURN-ON” fluorescent sensor was developed for selective and reversible detection of Zn2+in vitro, in which Fe2+ acted as the reversible switch.

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We thank the Science and Engineering Research Board, Government of India, New Delhi for financial support [ECR-2016-000839/CS] and Board of Research in Nuclear Science (BRNS), Mumbai (37(2)/14/18/2017-BRNS) for financial support. We thank NIT Manipur for providing infrastructure. We sincerely thank Prof. Akhil R. Chakravarty, IISc Bangalore for providing the facility of cellular studies. We thank Prof. Mohammad Qureshi, Central Instruments Facility (CIF), IIT Guwahati for measuring luminescent decay for the ligands and in presence of metals. We also thank Advanced Material Research Center, IIT Mandi for recording the 1H and 13C NMR, ESI mass spectra of the probes and the complexes.

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Correspondence to Mithun Roy.

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Musib, D., Raza, M.K., Devi, S.S. et al. A reversible, benzothiazole-based “Turn-on” fluorescence sensor for selective detection of Zn2+ ions in vitro. J Chem Sci 132, 43 (2020). https://doi.org/10.1007/s12039-020-1745-z

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  • Reversible and selective detection of Zn2+
  • Fe2+ as the reversible switch
  • pH and temperature dependence
  • DFT and TD-DFT
  • On-site screening analysis
  • Cellular imaging