A Synthetic Fluorescent Mitochondria‐Targeted Sensor for Ratiometric Imaging of Calcium in Live Cells

Abstract

AbstractCa2+ handling by mitochondria is crucial for cell life and the direct measure of mitochondrial Ca2+ concentration in living cells is of pivotal interest. Genetically‐encoded indicators greatly facilitated this task, however they require demanding delivery procedures. On the other hand, existing mitochondria‐targeted synthetic Ca2+ indicators are plagued by several drawbacks, for example, non‐specific localization, leakage, toxicity. Here we report the synthesis and characterization of a new fluorescent Ca2+ sensor, named mt‐fura‐2, obtained by coupling two triphenylphosphonium cations to the molecular backbone of the ratiometric Ca2+ indicator fura‐2. Mt‐fura‐2 binds Ca2+ with a dissociation constant of ≈1.5 μm in vitro. When loaded in different cell types as acetoxymethyl ester, the probe shows proper mitochondrial localization and accurately measures matrix [Ca2+] variations, proving its superiority over available dyes. We describe the synthesis, characterization and application of mt‐fura‐2 to cell types where the delivery of genetically‐encoded indicators is troublesome.