On-off-on relay fluorescence recognition of ferric and fluoride ions based on indicator displacement in living cells

• Published in: Analytica chimica acta 2019-08, Vol.1066, p.112-120
• Main Authors: Selvaraj, Muthusamy, Rajalakshmi, Kanagaraj, Nam, Yun-Sik, Lee, Yeonhee, Song, Jong-Won, Lee, Ho-Jin, Lee, Kang-Bong
• Format: Article
• Language: English
• Subjects: Acids; Anions; Boronic acid derivative; Cations; Conformation; Cytotoxicity; Ferric ions; Fluorescence; Fluorescence imaging; Fluorescent indicators; Fluorides; Imidazole; Ions; Iron; Living HeLa cells; Medical imaging; Probe for Fe3+ ions and F; Reagents; Selectivity; Stoichiometry; Toxicity; Water analysis; Water sampling; “On-off-on” sensor
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2019.03.040

A new boronic acid derivative functionalized with a 4-(3-(4-(4,5-diphenyl-1H-imidazole-2-yl)phenyl)-1,2,4-oxadiazol-5-yl)phenyl (IOP) moiety was synthesized for use as a sequential “on-off-on”-type relay fluorescence probe for Fe3+ ions and F− ions with high selectivity and sensitivity under physiological conditions. The introduction of Fe3+ to IOP boronic acid (IOPBA) formed an Fe3+IOPBA complex, which led to quenching of the blue fluorescence intensity at 458 nm. The lowest-energy conformation of IOPBA was theoretically predicted to adopt an extended structure, and the Fe3+ ion in the Fe3+IOPBA complex was coordinated to two phenyl groups to form a π-complex. Upon addition of F− to the Fe3+IOPBA complex, the original fluorescence was recovered due to formation of [FeF6]3‒, resulting in “on-off-on”-type sensor behavior. IOPBA showed high selectivity towards Fe3+ among other cations. Moreover, the Fe3+IOPBA complex showed specific selectivity towards F−, with other cations and anions not interfering with detection. Both sensing processes showed 1:1 stoichiometry with binding constants of 6.87 × 106 and 4.49 × 106 mol−1 L for Fe3+ with IOPBA and F− with Fe3+IOPBA, respectively. The limits of detection for Fe3+ and F− were 10 and 1 nM, respectively. The proposed method was successfully applied in real water samples. Furthermore, the probe had low cytotoxicity and was successfully used as a bioimaging reagent to detect intracellular Fe3+ and F− in living HeLa cells. [Display omitted] •Imidazole oxadiazole boronic acid derivative (IOPBA) was designed and synthesized.•IOPBA showed highly sensitive and selective response for Fe3+ and F−.•On-off-on type relay response was achieved at Fe3+IOPBA with F−.•The probe expressed LODs of 10 and 1 nM for Fe3+ and F−, respectively.•IOPBA can be utilized as bioimaging reagent for Fe3+ and F− in living HeLa cells.