Na+ Selective Fluorescent Tools Based on Fluorescence Intensity Enhancements, Lifetime Changes, and on a Ratiometric Response

• Published in: Chemistry : a European journal 2019-09, Vol.25 (53), p.12412-12422
• Main Authors: Schwarze, Thomas, Riemer, Janine, Müller, Holger, John, Leonard, Holdt, Hans‐Jürgen, Wessig, Pablo
• Format: Article
• Language: English
• Subjects: Chemistry; crown compounds; Emission; Fluorescence; fluorescence lifetime; Fluorescent indicators; fluorescent probes; Potassium; Probes; ratiometric; sodium; Wavelengths
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201902536

Over the years, we developed highly selective fluorescent probes for K+ in water, which show K+‐induced fluorescence intensity enhancements, lifetime changes, or a ratiometric behavior at two emission wavelengths (cf. Scheme 1, K1–K4). In this paper, we introduce selective fluorescent probes for Na+ in water, which also show Na+ induced signal changes, which are analyzed by diverse fluorescence techniques. Initially, we synthesized the fluorescent probes 2, 4, 5, 6 and 10 for a fluorescence analysis by intensity enhancements at one wavelength by varying the Na+ responsive ionophore unit and the fluorophore moiety to adjust different Kd values for an intra‐ or extracellular Na+ analysis. Thus, we found that 2, 4 and 5 are Na+ selective fluorescent tools, which are able to measure physiologically important Na+ levels at wavelengths higher than 500 nm. Secondly, we developed the fluorescent probes 7 and 8 to analyze precise Na+ levels by fluorescence lifetime changes. Herein, only 8 (Kd=106 mm) is a capable fluorescent tool to measure Na+ levels in blood samples by lifetime changes. Finally, the fluorescent probe 9 was designed to show a Na+ induced ratiometric fluorescence behavior at two emission wavelengths. As desired, 9 (Kd=78 mm) showed a ratiometric fluorescence response towards Na+ ions and is a suitable tool to measure physiologically relevant Na+ levels by the intensity change of two emission wavelengths at 404 nm and 492 nm. Click! Click! A set of highly Na+ selective fluorescent probes was synthesized using click chemistry. These probes show Na+ induced fluorescence intensity or lifetime changes or a ratiometric behavior at two emission wavelengths.