Fluorescent Determination of Calcium Ion Using a Coumarinyl Pyrazoline Scaffold and Its Application in Living Cells

Calcium is an essential element for living systems and involved in numerous intracellular signaling cascades. In this work, a novel fluorescent probe based on a coumarin and pyrazoline scaffold was designed and synthesized for the detection of Ca2+ by a photoinduced electron transfer (PET) strategy. The probe showed good selectivity for Ca2+ compared to other substances in ethanol with a low detection limit (1.37 × 10−7 M). Meanwhile, following the addition of Ca2+ ions, the probe showed an obvious “turn on” with a rapid response of less than 5 s and 1:1 binding with an association constant of 7.97 × 103 M−1. Furthermore, the fluorescence imaging of the probe was also performed in the presence of Ca2+ in living A549 cells.