An anthracene–quinoline based dual-mode fluorometric–colorimetric sensor for the detection of Fe3+ and its application in live cell imaging

Abstract

An anthracene–quinoline based dual-mode chemosensor, anthracene-9-carboxylic acid quinoline-8-ylamide (HAQ), has been synthesized and fully characterized using elemental analysis, different spectroscopic methods, and single crystal X-ray diffraction analysis. HAQ acts as an “On–Off” fluorescent sensor toward Fe³⁺ ions in DMSO solution with high selectivity and sensitivity over all other competitive metal ions. The limit of detection (LOD) for Fe³⁺ and the binding constant (K_a) for the resulting complex are 1.3 × 10⁻⁶ M and 3.7 × 10⁸ M⁻¹, respectively. Furthermore, HAQ displays a strong color change from colorless to bright yellow when exposed to Fe³⁺, which can be easily observed by the naked eye. The sensing mechanism and 1 : 1 binding stoichiometry of AQ⁻ and Fe³⁺ are confirmed using Job's plot, ESI-MS data, and computational studies. The in vitro cytotoxicity of the probe has been tested against the human breast cancer cell line MCF-7 using the MTT assay, showing a cell viability of more than 95% in the concentration range of 1.25–100 μM. The fluorescence imaging study revealed the good cell permeability of HAQ and its efficient cell staining ability; thus, the probe could be used to detect the accumulation of Fe³⁺ in living cells.