A new carboxamide probe as On-Off fluorescent and colorimetric sensor for Fe3+ and application in detecting intracellular Fe3+ ion in living cells

A novel quinoline-functionalized carboxamide derivative, 1H-indole-2-carboxylic acid quinoline-8-ylamide (H2IQ), has been designed and synthesized via a benign method for detection of Fe3+. The On-Off H2IQ chemosensor is highly selective and sensitive toward Fe3+ in the presence of other competing cations. This sensor displays rapid Fe3+ mediated decrease of florescence intensity at 445 nm, and also intense color change from colorless to bright yellow in DMSO-acetonitrile (1:9 v/v) solution. The 1:1 binding mode of the H2IQ with Fe3+ is confirmed by means of Job's plot and ESI-MS. The association constant (Ka) and limit of detection (LOD) for the resulting Fe3+ complex is 3.7 × 105 M-1 and 4.3 × 10-7 M respectively. Other interfering ions such as Na+, K+, Ca2+, Mg2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Mn2+, Cr3+ and Al3+, show either no or slight change in the fluorescence intensity of H2IQ in the presence of Fe3+. The cytotoxicity of H2IQ was examined using the MTT assay. H2IQ is cell penetrant and does not overtly affect cell viability in various human cell lines. Importantly, using Opera PhenixTM HCS live cell imaging system, we have shown that H2IQ can be used to detect the intracellular presence of Fe3+ ions in live cells.

• View at Publisher
• View at Scopus