title: Bioinspired design of a polymer gel sensor for the realization of extracellular Ca(2+) imaging.
abstract: Although the role of extracellular Ca(2+) draws increasing attention as a messenger in intercellular communications, there is currently no tool available for imaging Ca(2+) dynamics in extracellular regions. Here we report the first solid-state fluorescent Ca(2+) sensor that fulfills the essential requirements for realizing extracellular Ca(2+) imaging. Inspired by natural extracellular Ca(2+)-sensing receptors, we designed a particular type of chemically-crosslinked polyacrylic acid gel, which can undergo single-chain aggregation in the presence of Ca(2+). By attaching aggregation-induced emission luminogen to the polyacrylic acid as a pendant, the conformational state of the main chain at a given Ca(2+) concentration is successfully translated into fluorescence property. The Ca(2+) sensor has a millimolar-order apparent dissociation constant compatible with extracellular Ca(2+) concentrations, and exhibits sufficient dynamic range and excellent selectivity in the presence of physiological concentrations of biologically relevant ions, thus enabling monitoring of submillimolar fluctuations of Ca(2+) in flowing analytes containing millimolar Ca(2+) concentrations.
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Ishiwari
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Hanako
authors.initials: H
authors.lastname: Hasebe
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Satoko
authors.initials: S
authors.lastname: Matsumura
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Fatin
authors.initials: F
authors.lastname: Hajjaj
authors.affiliation: Department of Anatomy and Cell Biology, Faculty of Medicine, Nara Medical University, Kashihara, Nara 634-8521, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Horii-Hayashi
authors.affiliation: Department of Anatomy and Cell Biology, Faculty of Medicine, Nara Medical University, Kashihara, Nara 634-8521, Japan.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Nishi
authors.affiliation: Department of Electrical and Electronic Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Someya
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Fukushima
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D002118:Calcium / Q000032:analysis*; D005110:Extracellular Space / Q000737:chemistry*; D005453:Fluorescence; D061848:Optical Imaging / Q000379:methods*
chemical_list: D000180:Acrylic Resins; C016680:polyacrylamide gels; D002118:Calcium