A highly selective fluorescent probe for the intracellular measurement of magnesium ion.

Magnesium ion (Mg+2) plays an important role in various biological processes. All the commercial indicators available share a common drawback, i.e., they have a higher affinity towards calcium ions (Ca+2) than Mg+2. In this study, we reported a new robust green fluorescent indicator, Mag-520, for detection of Mg+2 in live cells. Our results showed that Mag-520 has 10 fold higher affinity towards Mg+2 than Ca+2, while mag-fluo-4 has less than 0.5 fold affinity to Mg+2 than Ca+2 under the same conditions using flow cytometry and fluorescence microscopy. The results demonstrated that Mag-520 provides a better tool to measure Mg+2 with less interference from Ca+2.