Suchergebnisse

The irradiation of gold nanorod colloids with a femtosecond laser can be tuned to induce controlled nanorod reshaping, yielding colloids with exceptionally narrow localized surface plasmon resonance bands. The process relies on a regime characterized by a gentle multishot reduction of the aspect ratio, whereas the rod shape and volume are barely affected. Successful reshaping can only occur within a narrow window of the heat dissipation rate: Low cooling rates lead to drastic morphological changes, and fast cooling has nearly no effect. Hence, a delicate balance must be achieved between irradiation fluence and surface density of the surfactant on the nanorods. This perfection process is appealing because it provides a simple, fast, reproducible, and scalable route toward gold nanorods with an optical response of exceptional quality, near the theoretical limit. ; This work was funded by the Spanish MINECO (Ministry of Economy and Competitiveness; grants CTQ2012-37404-C02-01, MAT2013-46101-R, MAT2014-59678-R, ENE2015-70300-C3-3-R, and CTQ2015-65033-P), the EUROfusion Consortium (AWP15-ENR-01/CEA-02), the Madrid Regional Government (S2013/MIT-2775 and S2013/MIT-2807), and the European Research Council (ERC Advanced Grant 267867, Plasmaquo). A.G.-M. and G.G.-R. respectively acknowledge receipt of Ramón y Cajal and FPI (Formación de Personal Investigador) fellowships from the Spanish MINECO. P.D.-N. acknowledges receipt of a fellowship from the Madrid Regional Government. The authors acknowledge the computer resources and technical assistance provided by CESVIMA (Centro de Supercomputación y Visualización de Madrid, Universidad Politécnica de Madrid) and the facilities provided by the Center for Ultrafast Lasers and the National Center of Microscopy (Universidad Complutense de Madrid). All results are reported in the main paper and supplementary materials.

21 p.-3 fig.-1 tab.-9 fig. supl. ; Understanding protein amyloidogenesis is an important topic in protein science, fueled by the role of amyloid aggregates, especially oligomers, in the etiology of a number of devastating human degenerative diseases. However, the mechanisms that determine the formation of amyloid oligomers remain elusive due to the high complexity of the amyloidogenesis process. For instance, gold nanoparticles promote or inhibit amyloid fibrillation. We have functionalized gold nanorods with a metal-chelating group to selectively immobilize soluble RepA-WH1, a model synthetic bacterial prionoid, using a hexa-histidine tag (H6). H6-RepA-WH1 undergoes stable amyloid oligomerization in the presence of catalytic concentrations of anisotropic nanoparticles. Then, in a physically separated event, such oligomers promote the growth of amyloid fibers of untagged RepA-WH1. SERS spectral changes of H6-RepA-WH1 on spherical citrate-AuNP substrates provide evidence for structural modifications in the protein, which are compatible with a gradual increase in β-sheet structure, as expected in amyloid oligomerization. ; Research at the R.G.laboratory was supported by MINECO grants CSD2009-00088, BIO2012-30852 and BIO2015-68730-R. Research at the A.G-M. and L.M.L-M. laboratories was supported by MINECO (MAT2014-59678-R and MAT2013-46101-R), Madrid Regional Government (S2013/MIT-2807) and the "I Convocatoria de Ayudas Fundación BBVA a Investigadores,Innovadores y Creadores Culturales"(14_CBB_147) grants.A.G-M. and G.G-R. acknowledge,respectively,receipt of Ramón y Cajal and FPI Fellowships from the Spanish MINECO. ; Peer reviewed

The search for efficient plasmonic photothermal therapies using nonharmful pulse laser irradiation at the near-infrared (NIR) is fundamental for biomedical cancer research. Therefore, the development of novel assembled plasmonic gold nanostructures with the aim of reducing the applied laser power density to a minimum through hot-spot-mediated cell photothermolysis is an ongoing challenge. We demonstrate that gold nanorods (Au NRs) functionalized at their tips with a pH-sensitive ligand assemble into oligomers within cell lysosomes through hydrogen-bonding attractive interactions. The unique intracellular features of the plasmonic oligomers allow us to significantly reduce the femtosecond laser power density and Au NR dose while still achieving excellent cell killing rates. The formation of gold tip-to-tip oligomers with longitudinal localized surface plasmon resonance bands at the NIR, obtained from low-aspect-ratio Au NRs close in resonance with 800 nm Ti:sapphire 90 fs laser pulses, was found to be the key parameter for realizing the enhanced plasmonic photothermal therapy. ; This work has been funded by the Spanish MINECO (MAT2014-59678-R and CTQ2012-37404-C02-01) and the Madrid Regional Government (S2013/MIT-2807). A.C.-M. and M.C. and I.L.-M. acknowledge the financial support of the ERC Starting Grants "NANOFORCELLS" (ERC-StG-2011-278860) and "MITOCHON" (ERC-StG-2013-338133). A.G.-M. and I.L.-M. acknowledge receipt of Ramón y Cajal Fellowships from the Spanish MINECO. G.G.-R. acknowledges receipt of the FPI Fellowship from the Spanish MINECO. ; Peer reviewed

Amphiphilic nonionic ligands, synthesized with a fixed hydrophobic moiety formed by a thiolated alkyl chain and an aromatic ring, and with a hydrophilic tail composed of a variable number of oxyethylene units, were used to functionalize spherical gold nanoparticles (AuNPs) in water. Steady-state and time-resolved fluorescence measurements of the AuNPs in the presence of α-cyclodextrin (α-CD) revealed the formation of supramolecular complexes between the ligand and macrocycle at the surface of the nanocrystals. The addition of α-CD induced the formation of inclusion complexes with a high apparent binding constant that decreased with the increasing oxyethylene chain length. The formation of polyrotaxanes at the surface of AuNPs, in which many α-CDs are trapped as hosts on the long and linear ligands, was demonstrated by the formation of large and homogeneous arrays of self-assembled AuNPs with hexagonal close packing, where the interparticle distance increased with the length of the oxyethylene chain. The estimated number of α-CDs per polyrotaxane suggests a high rigidization of the ligand upon complexation, allowing for nearly perfect control of the interparticle distance in the arrays. This degree of supramolecular control was extended to arrays formed by AuNPs stabilized with polyethylene glycol and even to binary arrays. Electromagnetic simulations showed that the enhancement and distribution of the electric field can be finely controlled in these plasmonic arrays. ; : This work was funded by the Spanish MINECO (MAT2014-59678-R and CTQ2015-65972-R), and the Madrid Regional Government (S2013/MIT-2807). A.G.-M. and S.G.-G. acknowledge receipt of a "Ramón y Cajal" and "Juan de la Cierva" fellowships, respectively, from the Spanish MINECO. P.D.N. acknowledges DIMMAT project funded by the Madrid Regional Government (S2013/MIT-2775). The authors acknowledge the facilities provided by the Nuclear Magnetic Resonance Center and the National Center of Microscopy (Universidad Complutense de Madrid).