title: Rational design of fluorescent bioimaging probes by controlling the aggregation behavior of squaraines: a special effect of ionic liquid pendants.
abstract: We herein present an effective strategy to create water-soluble fluorescent bioimaging dyes by introducing the imidazolium-based ionic liquid (IL) pendants into a fluorescent skeleton. A new type of water-soluble imidazolium-anchored squaraine dye was synthesized accordingly. The relationship between the aggregate of squaraines and their fluorescent cell imaging application was elucidated in detail. Firstly, the aggregation behavior of squaraines in water solutions could be suppressed by varying the alkyl chain attached to the imidazolium unit. Secondly, the capability of cellular uptake and staining of dyes was also dramatically enhanced upon increasing the length of the paraffinic chain. These squaraine dyes displayed an excellent photostability that could permit real-time fluorescence bioimaging experiments to be monitored over a long time period with constant sample irradiation. Additionally, we designed for the first time an Fe(II)-ion probe on the basis of an attack of the hydroxyl radical to the four-membered ring of squaraine. The results demonstrated that the imidazolium-anchored squaraines could perform "naked-eye" detection of the Fe(2+) ion over a wide range of other interfering metals in aqueous media. More surprisingly, this process showed a fluorescence "turn-off" and "-on" response through the regeneration of squaraines in cells.
authors.affiliation: Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry and State Key Laboratory of Biotherapy, West China Medical School, Sichuan University, 29 Wangjiang Road, Chengdu 610064, PR China.
authors.forename: Wenhai
authors.initials: W
authors.lastname: Wang
authors.forename: Afu
authors.initials: A
authors.lastname: Fu
authors.forename: Jingbo
authors.initials: J
authors.lastname: Lan
authors.forename: Ge
authors.initials: G
authors.lastname: Gao
authors.forename: Jingsong
authors.initials: J
authors.lastname: You
authors.forename: Lijuan
authors.initials: L
authors.lastname: Chen
mesh_terms: D003503:Cyclobutanes / Q000737:chemistry*; D005296:Ferrous Compounds / Q000032:analysis / Q000737:chemistry; D005456:Fluorescent Dyes / Q000138:chemical synthesis* / Q000737:chemistry; D006367:HeLa Cells; D056945:Hep G2 Cells; D006801:Humans; D006842:Hydrocarbons, Brominated / Q000138:chemical synthesis* / Q000737:chemistry; D007093:Imidazoles / Q000138:chemical synthesis* / Q000737:chemistry; D052578:Ionic Liquids; D015394:Molecular Structure; D010636:Phenols / Q000737:chemistry*; D012995:Solubility; D013050:Spectrometry, Fluorescence / Q000379:methods; D014407:Tumor Cells, Cultured; D014470:Umbilical Cord / Q000166:cytology; D014867:Water
chemical_list: D003503:Cyclobutanes; D005296:Ferrous Compounds; D005456:Fluorescent Dyes; D006842:Hydrocarbons, Brominated; D007093:Imidazoles; D052578:Ionic Liquids; D010636:Phenols; C480596:squaraine; D014867:Water