title: Sequential and parallel dual labeling of nanoparticles using click chemistry.
abstract: Bioorthogonal 'click' reactions have recently emerged as promising tools for chemistry and biological applications. By using a combination of two different 'click' reactions, 'double-click' strategies have been developed to attach multiple labels onto biomacromolecules. These strategies require multi-step modifications of the biomacromolecules that can lead to heterogeneity in the final conjugates. Herein, we report the synthesis and characterization of a set of three trifunctional linkers. The linkers having alkyne and cyclooctyne moieties that are capable of participating in sequential copper(I)-catalyzed and copper-free cycloaddition reactions with azides. We have also prepared a linker comprised of an alkyne and a 1,2,4,5-terazine moiety that allows for simultaneous cycloaddition reactions with azides and trans-cyclooctenes, respectively. These linkers can be attached to synthetic or biological macromolecules to create a platform capable of sequential or parallel 'double-click' labeling in biological systems. We show this potential using a generation 5 (G5) polyamidoamine (PAMAM) dendrimer in combination with the clickable linkers. The dendrimers were successfully modified with these linkers and we demonstrate both sequential and parallel 'double-click' labeling with fluorescent reporters. We anticipate that these linkers will have a variety of application including molecular imaging and monitoring of macromolecule interactions in biological systems.
authors.affiliation: Michigan Nanotechnology Institute for Medicine and Biological Sciences, United States. Electronic address: hzong@med.umich.edu.
authors.forename: Hong
authors.initials: H
authors.lastname: Zong
authors.affiliation: Michigan Nanotechnology Institute for Medicine and Biological Sciences, United States; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Michigan, United States.
authors.forename: Sascha N
authors.initials: SN
authors.lastname: Goonewardena
authors.affiliation: Michigan Nanotechnology Institute for Medicine and Biological Sciences, United States.
authors.forename: Huai-Ning
authors.initials: HN
authors.lastname: Chang
authors.affiliation: Michigan Nanotechnology Institute for Medicine and Biological Sciences, United States.
authors.forename: James B
authors.initials: JB
authors.lastname: Otis
authors.affiliation: Michigan Nanotechnology Institute for Medicine and Biological Sciences, United States. Electronic address: jbakerjr@med.umich.edu.
authors.forename: James R
authors.initials: JR
authors.lastname: Baker
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D001386:Azides / Q000737:chemistry*; D057930:Click Chemistry; D061565:Cycloaddition Reaction; D034242:Cyclooctanes / Q000737:chemistry; D050091:Dendrimers / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D011073:Polyamines / Q000737:chemistry
chemical_list: D000480:Alkynes; D001386:Azides; D034242:Cyclooctanes; D050091:Dendrimers; D005456:Fluorescent Dyes; C531249:Poly(amidoamine); D011073:Polyamines
keywords: Click chemistry; FRET; Fluorescent labeling; PAMAM dendrimer