A quinoline-based chromogenic and ratiometric fluorescent probe for selective detection of Mg2+ ion: Design, synthesis and its application in salt lake brines and bioimaging

A fluorescent probe was rational designed and prepared to distinguish Mg2+ ion from Ca2+ ion, in which 8-hydroxyquinoline acted as not only a fluorophore but also a recognition group. Notably, this probe QB (8-hydroxyquinoline-5-benzothiazole) shows two fluorescence response modes for highly selective detection of Mg2+ ion, namely fluorescence ratiometric mode and turn-on mode, which can be realized by controlling the excitation wavelength at 356 nm or 425 nm. After the addition of Mg2+ ion, the color of the QB solution changed from colorless to yellow, which can be easily found by naked eye. All experimental results suggested that probe QB has a high selectivity toward Mg2+ ion in the presence of other cations. Its detection limit for Mg2+ ion was estimated as low as 0.142 mu M, and this value was far lower than the intracellular concentration (0.5-1.2 mM). The detection mechanism was proposed further by the experiment of H-1 NMR titration and theoretical calculation. More significantly, this probe was successfully used to detect Mg2+ ion in brine samples as a quantitative method, and was also applied to detecting and imaging Mg2+ ion in living cells, indicating its great application value in practical use for the detection of Mg2+ ion.

Automated summary

A newly designed fluorescent probe QB shows high selectivity for Mg2+ ion detection with two fluorescence response modes, ratiometric and turn-on modes. It has been successfully applied in brine samples and living cells, indicating its great application potential in practical use for Mg2+ ion detection.