title: Smart near-infrared fluorescence probes with donor-acceptor structure for in vivo detection of β-amyloid deposits.
abstract: The deposition of β-amyloid (Aβ) plaques in the parenchymal and cortical brain is accepted as the main pathological hallmark of Alzheimer's disease (AD); however, early detection of AD still presents a challenge. With the assistance of molecular imaging techniques, imaging agents specifically targeting Aβ plaques in the brain may lead to the early diagnosis of AD. Herein, we report the design, synthesis, and evaluation of a series of smart near-infrared fluorescence (NIRF) imaging probes with donor-acceptor architecture bridged by a conjugated π-electron chain for Aβ plaques. The chemical structure of these NIRF probes is completely different from Congo Red and Thioflavin-T. Probes with a longer conjugated π system (carbon-carbon double bond) displayed maximum emission in PBS (>650 nm), which falls in the best range for NIRF probes. These probes were proved to have affinity to Aβ plaques in fluorescent staining of brain sections from an AD patient and double transgenic mice, as well as in an in vitro binding assay using Aβ(1-42) aggregates. One probe with high affinity (K(i) = 37 nM, K(d) = 27 nM) was selected for in vivo imaging. It can penetrate the blood-brain barrier of nude mice efficiently and is quickly washed out of the normal brain. Moreover, after intravenous injection of this probe, 22-month-old APPswe/PSEN1 mice exhibited a higher relative signal than control mice over the same period of time, and ex vivo fluorescent observations confirmed the existence of Aβ plaques. In summary, this probe meets most of the requirements for a NIRF contrast agent for the detection of Aβ plaques both in vitro and in vivo.
authors.affiliation: Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University , 46-29 Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Mengchao
authors.initials: M
authors.lastname: Cui
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ono
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Watanabe
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kimura
authors.forename: Boli
authors.initials: B
authors.lastname: Liu
authors.forename: Hideo
authors.initials: H
authors.lastname: Saji
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry*; D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D015195:Drug Design; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry* / Q000633:toxicity; D006801:Humans; D007259:Infrared Rays; D051379:Mice; D061848:Optical Imaging / Q000379:methods*; D010446:Peptide Fragments / Q000737:chemistry*; D055503:Protein Multimerization; D017433:Protein Structure, Secondary
chemical_list: D016229:Amyloid beta-Peptides; D005456:Fluorescent Dyes; D010446:Peptide Fragments; C075222:amyloid beta-protein (1-42)