title: Near-infrared fluorescence probes for enzymes based on binding affinity modulation of squarylium dye scaffold.
abstract: We present a novel design strategy for near-infrared (NIR) fluorescence probes utilizing dye-protein interaction as a trigger for fluorescence enhancement. The design principle involves modification of a polymethine dye with cleavable functional groups that reduce the dye's protein-binding affinity. When these functional groups are removed by specific interaction with the target enzymes, the dye's protein affinity is restored, protein binding occurs, and the dye's fluorescence is strongly enhanced. To validate this strategy, we first designed and synthesized an alkaline phosphatase (ALP) sensor by introducing phosphate into the squarylium dye scaffold; this sensor was able to detect ALP-labeled secondary antibodies in Western blotting analysis. Second, we synthesized a probe for β-galactosidase (widely used as a reporter of gene expression) by means of β-galactosyl substitution of the squarylium scaffold; this sensor was able to visualize β-galactosidase activity both in vitro and in vivo. Our strategy should be applicable to obtain NIR fluorescence probes for a wide range of target enzymes.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Daihi
authors.initials: D
authors.lastname: Oushiki
authors.forename: Hirotatsu
authors.initials: H
authors.lastname: Kojima
authors.forename: Yuki
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Toru
authors.initials: T
authors.lastname: Komatsu
authors.forename: Takuya
authors.initials: T
authors.lastname: Terai
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Hanaoka
authors.forename: Makiya
authors.initials: M
authors.lastname: Nishikawa
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Takakura
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Nagano
mesh_terms: D000469:Alkaline Phosphatase / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D005456:Fluorescent Dyes / Q000737:chemistry*; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D011485:Protein Binding; D011789:Quantum Theory; D019265:Spectroscopy, Near-Infrared; D001616:beta-Galactosidase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D005456:Fluorescent Dyes; D000469:Alkaline Phosphatase; D001616:beta-Galactosidase