Methionine-derived Schiff base as selective fluorescent “turn-on” chemosensor for Zn2+ in aqueous medium and its application in living cells imaging

• Quantitative synthesis of methionine-derived Schiff base (SMSB) used as Zn2+ fluorescent detector.
• Fluorescent “turn-on” selective Zn2+ chemosensor is reported.
• The binding phenomenon of Zn2+ with SMSB was investigated by 1H NMR and HR-ESI-MS showing 1:1 binding ratio.
• A complete UV–vis and fluorescent study of SMSB/Zn2+ binding.
• Application of SMSB in living cells imaging.

We describe the quantitative synthesis of a Schiff base derived from methionine and salicylaldehyde (SMSB) which displayed turn-on selective fluorescent chemo-sensing properties for Zn2+ in buffered CH3CN/H2O (1:1) solution. In physiological pH (7.2 buffered) SMSB exhibited high selectivity and sensitivity toward Zn2+ over the other selected metal ions. Upon the addition of Zn2+ 33 folds of emission enhancement was observed in SMSB and limit of detection (CL) for Zn2+ was found to be 5.0 × 10−7 M. This binding phenomenon was studied by 1H NMR and HR-MS analysis. Mass spectrometry analysis revealed that SMSB interacts with Zn2+ and form a 1:1 complex, also confirmed by Job's plot. This probe was completely retrieved by adding EDTANa2 solution, exhibited a fluorescent quenching effect by removing Zn2+ from the sensor. SMSB was observed to have a good tolerance for fluorescence detection of Zn2+ in pH range 6–10. Furthermore it is successfully investigated for living cells imaging using MCF-7 cells. Combine experimental results indicated SMSB to be a useful and powerful chemosensing probe for Zn2+ in water as well as in living cells.

SMSB showed selective “turn-on” fluorescence to Zn2+ in the presence of other common metal ions and it is also applied successfully in living cells imaging.Figure optionsDownload as PowerPoint slide