Naked-eye fluorescent sensor for Cu(II) based on indole conjugate BODIPY dye

A novel on/off fluorescent indole/BODIPY-based Cu2+ chemosensor (3) was synthesized by Knoevenagel condensation of BODIPY derivative 1 with 2-methyl-indole-3-carbaldehyde 2. The identity of compound 3 was confirmed by 1H NMR, 13C NMR, FT-IR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and single crystal X-ray diffraction techniques. Fluorescent chemosensor (3) is found to be highly selective and sensitive for detection of Cu2+ with a color change from purple to yellow. The optical sensor features for the Cu2+ complex of 3 were investigated by UV–Vis and fluorescence spectroscopy. The addition of Cu2+ caused quenching of fluorescence intensity and the detection limit was calculated to be 0.124 μM. Also, the stoichiometry ratio of 3+Cu2+ was obtained 2:1 by Job’s plot. Live cell image, flow cytometry and cytotoxic properties of compound 3 were examined.

A novel indole mono-styryl BODIPY was synthesised and characterized for the colorimetric recognition of Cu2+. It was also revealed from this study 3 can passively diffuse through cell membrane and stain both bacterial and mammalian cells even in very low concentrations. BODIPY-indole 3 retains inside the cells in cytometry and can be further modified for other applications.Figure optionsDownload as PowerPoint slide