"Turn-on" fluorescent probe detection of Ca 2+ ions and applications to bioimaging.

Ca2+ is intracellular divalent cation with the largest concentration variations and involved in many biological phenomena and often acted as a second messenger in signaling pathway. Therefore, the development of probes for specific Ca2+ detection is of great importance. Herein, a novel turn-on fluorescent probe for the detection of Ca2+ in MeCN-aqueous medium was designed and synthesized. The probe displayed responses to Ca2+ with a fluorescence enhancement at 525nm, accompanying with a distinct fluorescence change from nearly colorless to bright yellow-green. Besides, the probe exhibited a rapid signal response time (within 25s), a good linearity range and a lower detection limit (2.70×10-7 M). In addition, the ability of the probe to detect Ca2+ in living cells (HeLa cells) via an enhancement of the fluorescence has also been demonstrated.