Dual-Color Imaging of Magnesium/Calcium Ion Activities with Two-Photon Fluorescent Probes

We report two-photon probes (FMg1 and FMg2) that can selectively detect intracellular free Mg2+ ([Mg2+]i) in live cells and tissues by two-photon microscopy. Combined with BCaM, a two-photon probe for near-membrane Ca2+ ([Ca2+]m), FMg2 allows dual-color imaging of Mg2+/Ca2+ activities in live cells and [Mg2+]i /[Ca2+]m distributions in live tissues at a depth of 100–200 μm.