A Highly K+-Selective Phenylaza-[18]crown-6-Lariat-Ether-Based Fluoroionophore and Its Application in the Sensing of K+ Ions with an Optical Sensor Film and in Cells

• Published in: Chemistry : a European journal 2013-10, Vol.19 (44), p.14911-14917
• Main Authors: Ast, Sandra, Schwarze, Thomas, Müller, Holger, Sukhanov, Aleksey, Michaelis, Stefanie, Wegener, Joachim, Wolfbeis, Otto S., Körzdörfer, Thomas, Dürkop, Axel, Holdt, Hans-Jürgen
• Format: Article
• Language: English
• Subjects: Chemistry; crown compounds; Crown Ethers - chemistry; Fluorescence; gels; Gels - chemistry; Ionophores - chemistry; Ions - chemistry; Molecular Structure; potassium; Potassium - chemistry; Sensors; Spectrometry, Fluorescence
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201302350

Herein, we report the synthesis of two phenylaza‐[18]crown‐6 lariat ethers with a coumarin fluorophore (1 and 2) and we reveal that compound 1 is an excellent probe for K+ ions under simulated physiological conditions. The presence of a 2‐methoxyethoxy lariat group at the ortho position of the anilino moiety is crucial to the substantially increased stability of compounds 1 and 2 over their lariat‐free phenylaza‐[18]crown‐6 ether analogues. Probe 1 shows a high K+/Na+ selectivity and a 2.5‐fold fluorescence enhancement was observed in the presence of 100 mM K+ ions. A fluorescent membrane sensor, which was prepared by incorporating probe 1 into a hydrogel, showed a fully reversible response, a response time of 150 s, and a signal change of 7.8 % per 1 mM K+ within the range 1–10 mM K+. The membrane was easily fabricated (only a single sensing layer on a solid polyester support), yet no leaching was observed. Moreover, compound 1 rapidly permeated into cells, was cytocompatible, and was suitable for the fluorescent imaging of K+ ions on both the extracellular and intracellular levels. The crown jewels: A new phenylaza‐[18]crown‐6 lariat ether that contains a coumarin fluorophore (1) is an excellent fluorescent probe that shows high selectivity and sensitivity for K+ ions under simulated physiological conditions and in cells (see scheme). A fluorescent membrane sensor was prepared by incorporating probe 1 into a hydrogel, which showed a signal change of 7.8 % per 1 mM K+ within the range 1–10 mM K+.