Highly K⁺‐Selective Fluorescent Probes for Lifetime Sensing of K⁺ in Living Cells

Abstract

The new K -selective fluorescent probes 1 and 2 were obtained by Cu -catalyzed 1,3-dipolar azide alkyne cycloaddition (CuAAC) reactions of an alkyne-substituted [1,3]dioxolo[4,5-f][1,3]benzodioxole (DBD) ester fluorophore with azido-functionalized N-phenylaza-18-crown-6 ether and N-(o-isopropoxy) phenylaza-18-crown-6 ether, respectively. Probes 1 and 2 allow the detection of K in the presence of Na in water by fluorescence enhancement (2.2 for 1 at 2000 mm K and 2.5 for 2 at 160 mm K ). Fluorescence lifetime measurements in the absence and presence of K revealed bi-exponential decay kinetics with similar lifetimes, however with different proportions changing the averaged fluorescence decay times (τ ). For 1 a decrease of τ from 12.4 to 9.3 ns and for 2 an increase from 17.8 to 21.8 ns was observed. Variation of the substituent in ortho position of the aniline unit of the N-phenylaza-18-crown-6 host permits the modulation of the K value for a certain K concentration. For example, substitution of H in 1 by the isopropoxy group (2) decreased the K value from >300 mm to 10 mm. 2 was chosen for studying the efflux of K from human red blood cells (RBC). Upon addition of the Ca ionophor ionomycin to a RBC suspension in a buffer containing Ca , the fluorescence of 2 slightly rose within 10 min, however, after 120 min a significant increase was observed.

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

“…Recently, we synthesized by CuAAC reactions (CuAAC=CuI‐catalyzed 1,3‐dipolar azide alkyne cycloaddition reaction) highly K + selective fluorescent probes for the exclusive determination of K + by fluorescence enhancements,– fluorescence lifetime changes and by a ratiometric behavior at two emission wavelengths in water (cf. Scheme , see highly K + selective fluorescent probes K1 ‐ K4 ).…”

Extending the Class of [1,3]‐Dioxolo[4.5‐f]benzodioxole (DBD) Fluorescent Dyes

“…Following this principle, we also reported a DBD probe for the detection for carbohydrate lectin interactions . Very recently, we used DBD dyes in different FRET pairs, and developed a highly K + selective DBD probe …”

Detection of dsDNA with [1,3]Dioxolo[4,5‐f]benzodioxol (DBD) Dyes

“…Flash chromatography was carried out on silica gel 60 (40-63 mm). NMR spectra were recorded with aB ruker Avance 300 spectrometer.C hemical shifts are reported relative to the solvent signal Benzo [1,2-d:4,5-d']bis [1,3]dioxole-4-carbaldehyde (1):T his compound was prepared according to reference [9].…”

“…was prepared according to reference [27]. (3):C ompounds 1 (50 mg, 0.26 mmol, 1.0 equiv), 2 (108 mg, 0.38 mmol, 1.5 equiv) and pyridine (0.03 mL, 0.37 mmol, 1.0 equiv) were dissolved in anhydrous methanol (5 mL) and heated to reflux for 9h.T he precipitate product was fil- [1,3]dioxole (4):T his compound was prepared according to reference [9].…”

“…In 2011, our group introduced an ew class of fluorescent dyes based on [1,3]dioxolo [4,5-f]benzodioxole (DBD). [1] DBD dyes stand out because of their large Stokes shifts, large fluorescent lifetimes, and their sensitivity to the polarity of the environment, which blazed the trail to various applications of biological interestsuch as probing lipophilic environments, [2] the presence of K + ions [3] or carbohydrate-lectin interactions.…”