title: Facile preparation of water-soluble fluorescent gold nanoclusters for cellular imaging applications.
abstract: We report a facile strategy to synthesize water-soluble, fluorescent gold nanoclusters (AuNCs) in one step by using a mild reductant, tetrakis(hydroxymethyl)phosphonium chloride (THPC). A zwitterionic functional ligand, D-penicillamine (DPA), as a capping agent endowed the AuNCs with excellent stability in aqueous solvent over the physiologically relevant pH range. The DPA-capped AuNCs displayed excitation and emission bands at 400 and 610 nm, respectively; the fluorescence quantum yield was 1.3%. The effect of borohydride reduction on the optical spectra and X-ray photoelectron spectroscopy (XPS) results indicated that the AuNC luminescence is closely related to the presence of Au(I) on their surfaces. In a first optical imaging application, we studied internalization of the AuNCs by live HeLa cells using confocal microscopy with two-photon excitation. A cell viability assay revealed good biocompatibility of these AuNCs. Our studies demonstrate a great potential of DPA-stabilized AuNCs as fluorescent nanoprobes in bioimaging and related applications.
authors.affiliation: Institute of Applied Physics and Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Strasse 1, 76131 Karlsruhe, Germany.
authors.forename: Li
authors.initials: L
authors.lastname: Shang
authors.forename: René M
authors.initials: RM
authors.lastname: Dörlich
authors.forename: Stefan
authors.initials: S
authors.lastname: Brandholt
authors.forename: Reinhard
authors.initials: R
authors.lastname: Schneider
authors.forename: Vanessa
authors.initials: V
authors.lastname: Trouillet
authors.forename: Michael
authors.initials: M
authors.lastname: Bruns
authors.forename: Dagmar
authors.initials: D
authors.lastname: Gerthsen
authors.forename: G Ulrich
authors.initials: GU
authors.lastname: Nienhaus
mesh_terms: D006046:Gold; D006367:HeLa Cells; D006801:Humans; D008422:Materials Testing; D008856:Microscopy, Fluorescence / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D012995:Solubility; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D006046:Gold