Phenazine‐Based Fluorescence “Turn‐Off” Sensor for Fluoride: Application on Real Samples and to Cell and Zebrafish Imaging

Abstract

AbstractIn the present work, we report the design of a novel chemosensor 2‐(1H‐indole‐3‐yl)‐1H‐imidazo[4,5‐b]phenazine, (R) for fluoride ion detection via a naked eye observable colour change from light yellow to brown along with 10 fold ratiometric fluorescence quenching from green to no fluorescence in a matrix containing a large number of similar toxic anions in aqueous dimethylsulfoxide (30% H2O + DMSO) solution. The sensing mechanism was ascertained to be the fluoride triggered deprotonation of imidazole as well as indole moiety of R which is supported by 1:2 saturation level equivalence of R‐F‐. R was fully characterized through FT‐IR, 1H, 13C NMR and HRMS. R is an effective receptor for F‐ within a wide range of pH that indicates its bio‐compatibility. LoD and Ka for F‐ were found to be 1.8×10‐6 M (below 0.34 mg/Liter) and 2.7 × 104 M‐1 respectively. The experimental observations were supported by the theoretical calculations using density functional theory. R also showed its potential practical applicability for fluoride detection in toothpaste solution. Furthermore, to prove its nontoxicity, probe R also applied to a cytotoxicity assay of HeLa cells followed by confocal fluorescence cells imaging and Zebrafish imaging experiments.