Institute Catala Of Nanotecnologia Icn

Barcelona, Spain

Institute Catala Of Nanotecnologia Icn

Barcelona, Spain

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Cafun J.-D.,European Synchrotron Radiation Facility | Kvashnina K.O.,European Synchrotron Radiation Facility | Casals E.,Institute Catala Of Nanotecnologia Icn | Casals E.,Autonomous University of Barcelona | And 3 more authors.
ACS Nano | Year: 2013

The catalytic performance of ceria nanoparticles is generally attributed to active sites on the particle surface. The creation of oxygen vacancies and thus nonstoichiometric CeO2-δ has been proposed to result in Ce3+ sites with unpaired f electrons which can be oxidized to spinless Ce4+ ions during catalytic reactions. We monitored the Ce electronic structure during the synthesis and catalase mimetic reaction of colloidal ceria nanoparticles under in situ conditions. By means of high-energy resolution hard X-ray spectroscopy, we directly probed the Ce 4f and 5d orbitals. We observe pronounced changes of the Ce 5d bands upon reduction of the particle size and during the catalytic reaction. The Ce 4f orbitals, however, remain unchanged, and we do not observe any significant number of spin-unpaired Ce3+ sites even for catalytically active small (3 nm) particles with large surface to bulk ratio. This confirms strong orbital mixing between Ce and O, and the Ce spin state is conserved during the reaction. The particles show an increase of the interatomic distances between Ce and O during the catalytic decomposition of hydrogen peroxide. The redox partner is therefore not a local Ce3+ site, but the electron density that is received and released during the catalytic reaction is delocalized over the atoms of the nanoparticle. This invokes the picture of an electron sponge. © 2013 American Chemical Society.

Schulz F.,University of Hamburg | Vossmeyer T.,University of Hamburg | Bastus N.G.,University of Hamburg | Bastus N.G.,Institute Catala Of Nanotecnologia Icn | Weller H.,University of Hamburg
Langmuir | Year: 2013

Poly(ethylene glycol)- (PEG-) based ligands are well-established for the stabilization of nanoparticles in aqueous solution and are especially interesting for applications in medicine and biotechnology because they are known to improve the pharmacokinetic properties of nanomaterials. In this study, we prepared gold nanoparticles (AuNPs) with ligand shells of different monodentate poly(ethylene glycol)-thiol (PEG-SH) ligands. These ligands differed only in the segment connecting the thiol group with the PEG moiety (M w ≈ 2000 g/mol) through an ester bond, the spacer. All ligands were synthesized by straightforward esterification. Specifically, we used PEG ligands with a long (C10, PEGMUA) or short (C2, PEGMPA) alkylene spacer or a phenylene (PEGMPAA) spacer. The influence of the spacer on the stability of gold nanoparticle-PEG conjugates (AuNP@PEG) was tested by cyanide etching experiments, electrolyte-induced aggregation, and competitive ligand displacement with dithiothreitol (DTT). In the presence of 100 mM cyanide, AuNPs stabilized with PEGMPA or PEGMPAA were completely dissolved by oxidative etching within a few minutes, whereas AuNPs stabilized with PEGMUA needed more than 20 h to be completely etched. By complementary experiments, we deduced a simplified description for the etching process that takes into account the role of excess ligand. In the presence of free ligand, significantly fewer AuNPs are etched, suggesting a competition of etching and ligand binding to AuNPs. We also compared the stabilizing effect of PEGMUA with that of a bidentate PEG-thiol ligand (PEGLIP) and found a reversed stability against cyanide etching and DTT displacement, in agreement with previously reported observations. Our results clearly demonstrate the strong impact of the spacer structure on conjugate stability and provide valuable information for the rational design of more complex AuNP@PEG conjugates, which are of much interest in the context of biotechnology and medical applications. © 2013 American Chemical Society.

Schmidtke C.,University of Hamburg | Poselt E.,University of Hamburg | Ostermann J.,University of Hamburg | Pietsch A.,University of Hamburg | And 8 more authors.
Nanoscale | Year: 2013

Nanoparticles (NPs) play an increasingly important role in biological labeling and imaging applications. However, preserving their useful properties in an aqueous biological environment remains challenging, even more as NPs therein have to be long-time stable, biocompatible and nontoxic. For in vivo applications, size control is crucial in order to route excretion pathways, e.g. renal clearance vs. hepato-biliary accumulation. Equally necessary, cellular and tissue specific targeting demands suitable linker chemistry for surface functionalization with affinity molecules, like peptides, proteins, carbohydrates and nucleotides. Herein, we report a three stage encapsulation process for NPs comprised of (1) a partial ligand exchange by a multidentate polyolefinic amine ligand, PI-N3, (2) micellar encapsulation with a precisely tuned amphiphilic diblock PI-b-PEG copolymer, in which the PI chains intercalate to the PI-N3 prepolymer and (3) radical cross-linking of the adjacent alkenyl bonds. As a result, water-soluble NPs were obtained, which virtually maintained their primal physical properties and were exceptionally stable in biological media. PEG-terminal functionalization of the diblock PI-b-PEG copolymer with numerous functional groups was mostly straightforward by chain termination of the living anionic polymerization (LAP) with the respective reagents. More complex affinity ligands, e.g. carbohydrates or biotin, were introduced in a two-step process, prior to micellar encapsulation. Advantageously, this pre-assembly approach opens up rapid access to precisely tuned multifunctional NPs, just by using mixtures of diverse functional PI-b-PEG polymers in a combinatorial manner. All constructs showed no toxicity from 0.001 to 1 μM (particle concentration) in standard WST and LDH assays on A549 cells, as well as only marginal unspecific cellular uptake, even in serum-free medium. © 2013 The Royal Society of Chemistry.

Schmidtke C.,University of Hamburg | Lange H.,TU Berlin | Lange H.,Columbia University | Tran H.,University of Hamburg | And 7 more authors.
Journal of Physical Chemistry C | Year: 2013

Cross-linking of biocompatible ligand shells significantly improves the stability of nanocrystals in the biological environment. We report a detailed spectroscopic study of radical initiated reactions on poly(isoprene)-b- poly(ethelene glycol) encapsulated CdSe/CdS/ZnS core-shell-shell quantum dots. It was found that the radicals not only initiate cross-linking of the polyisoprene moieties but also may anneal the nanocrystal surfaces and improve their crystallinity. © 2013 American Chemical Society.

Stoehr L.C.,University of Salzburg | Gonzalez E.,Institute Catala Of Nanotecnologia Icn | Stampfl A.,Helmholtz Center Munich | Casals E.,Institute Catala Of Nanotecnologia Icn | And 3 more authors.
Particle and Fibre Toxicology | Year: 2011

Background: In nanotoxicology, the exact role of particle shape, in relation to the composition, on the capacity to induce toxicity is largely unknown. We investigated the toxic and immunotoxic effects of silver wires (length: 1.5 - 25 μm; diameter 100 - 160 nm), spherical silver nanoparticles (30 nm) and silver microparticles (<45 μm) on alveolar epithelial cells (A549).Methods: Wires and nanoparticles were synthesized by wet-chemistry methods and extensively characterized. Cell viability and cytotoxicity were assessed and potential immunotoxic effects were investigated. To compare the effects on an activated and a resting immune system, cells were stimulated with rhTNF-α or left untreated. Changes in intracellular free calcium levels were determined using calcium imaging. Finally, ion release from the particles was assessed by ICP-MS and the effects of released ions on cell viability and cytotoxicity were tested.Results: No effects were observed for the spherical particles, whereas the silver wires significantly reduced cell viability and increased LDH release from A549 cells. Cytokine promoter induction and NF-κB activation decreased in a concentration dependent manner similar to the decrease seen in cell viability. In addition, a strong increase of intracellular calcium levels within minutes after addition of wires was observed. This toxicity was not due to free silver ions, since the samples with the highest ion release did not induce toxicity and ion release control experiments with cells treated with pre-incubated medium did not show any effects either.Conclusions: These data showed that silver wires strongly affect the alveolar epithelial cells, whereas spherical silver particles had no effect. This supports the hypothesis that shape is one of the important factors that determine particle toxicity. © 2011 Stoehr et al; licensee BioMed Central Ltd.

Ojea-Jimenez I.,Institute Catala Of Nanotecnologia Icn | Lopez X.,Institute Catala Of Nanotecnologia Icn | Lopez X.,National Autonomous University of Mexico | Arbiol J.,CSIC - Institute of Materials Science | And 3 more authors.
ACS Nano | Year: 2012

Colloidal gold nanoparticles (Au NPs) have been employed as single entities for rapid scanning and sequestration of Hg(II) from multicomponent aqueous solutions containing low pollutant concentrations. Under the studied conditions, sodium citrate has been identified as the reducing agent and Au NPs as the catalyst in the reduction of Hg(II), which is efficiently trapped in the presence of other cations such as Cu(II) and Fe(III). The effect of Hg(II) uptake implies amalgam formation, which leads to remarkable morphological transformations. The hydrophobicity of the resulting amalgam and consequent expulsion from water eases its recovery. The interaction between Au and Hg has been studied using UV-vis, ICP-MS, (S)TEM, SEM, EDX, and XRD. © 2012 American Chemical Society.

Ojea-Jimenez I.,Institute Catala Of Nanotecnologia Icn | Bastus N.G.,Institute Catala Of Nanotecnologia Icn | Puntes V.,Institute Catala Of Nanotecnologia Icn | Puntes V.,Catalan Institution for Research and Advanced Studies
Journal of Physical Chemistry C | Year: 2011

The role of sodium citrate (SC) in the formation and growing mechanism of gold nanoparticles was systematically examined. Obtained results show that oxidation of SC can be induced either by the presence of HAuCl4 or by its thermal decomposition under air. By exchanging the order of reagent addition, it is possible to increase the oxidation rate of SC and hence control the size and morphology, thus allowing preparation of nanoparticles with a narrower size distribution than the standard Turkevich approach. © 2011 American Chemical Society.

Bastus N.G.,Institute Catala Of Nanotecnologia Icn | Comenge J.,Institute Catala Of Nanotecnologia Icn | Comenge J.,International Iberian Nanotechnology Laboratory | Comenge J.,Autonomous University of Barcelona | And 3 more authors.
Langmuir | Year: 2011

Monodisperse citrate-stabilized gold nanoparticles with a uniform quasi-spherical shape of up to ∼200 nm and a narrow size distribution were synthesized following a kinetically controlled seeded growth strategy via the reduction of HAuCl4 by sodium citrate. The inhibition of any secondary nucleation during homogeneous growth was controlled by adjusting the reaction conditions: temperature, gold precursor to seed particle concentration, and pH. This method presents improved results regarding the traditional Frens method in several aspects: (i) it produces particles of higher monodispersity; (ii) it allows better control of the gold nanoparticle size and size distribution; and (iii) it leads to higher concentrations. Gold nanoparticles synthesized following this method can be further functionalized with a wide variety of molecules, hence this method appears to be a promising candidate for application in the fields of biomedicine, photonics, and electronics, among others. © 2011 American Chemical Society.

Ojea-Jimenez I.,Institute Catala Of Nanotecnologia Icn | Comenge J.,Institute Catala Of Nanotecnologia Icn | Comenge J.,International Iberian Nanotechnology Laboratory | Garcia-Fernandez L.,Institute Catala Of Nanotecnologia Icn | And 4 more authors.
Current Drug Metabolism | Year: 2013

Inorganic nanoparticles (NPs) currently have immense potential as drug delivery vectors due to their unique physicochemical properties such as high surface area per unit volume, their optical and magnetic uniqueness and the ability to be functionalized with a large number of ligands to enhance their affinity towards target molecules. These features, together with the therapeutic activity of some drugs, render the combination of these two entities (NP-drug) as an attractive alternative in the area of drug delivery. One of the major advantages of these conjugates is the possibility to have a local delivery of the drug, thus reducing systemic side effects and enabling a higher efficiency of the therapeutic molecule. This review highlights the direct implications of nanoscale particles in the development of drug delivery systems. In more detail, it is also remarked the extensive use of inorganic NPs for targeted cancer therapies. As the range of nanoparticles and their applications continues to increase, human safety concerns are gaining importance, which makes it necessary to better understand the potential toxicity hazards of these materials. © 2013 Bentham Science Publishers.

Ojea-Jimenez I.,Institute Catala Of Nanotecnologia Icn | Garcia-Fernandez L.,Institute Catala Of Nanotecnologia Icn | Garcia-Fernandez L.,Autonomous University of Barcelona | Lorenzo J.,Autonomous University of Barcelona | And 3 more authors.
ACS Nano | Year: 2012

The present work faces the rising demand of cationic particles of different sizes for biological applications, especially in gene therapies and nanotoxicology studies. A simple phase-transfer methodology has been developed for the functionalization of gold nanoparticles (Au NPs) with a variety of ligands, both cationic and anionic in aqueous solution, employing different nanocrystal sizes with narrow size distributions. Successful functionalization has been demonstrated by UV-vis spectroscopy, DLS, χ-potential, and FTIR spectroscopy characterization of the particles before and after the phase transfer. The intracellular uptake of the differently charged Au NPs functionalized with peptidic biomolecules was investigated with human fibroblasts (1BR3G) by ICP-MS analysis of the digested cells and confocal fluorescence microscopy, which showed increased internalization of the cationic bioconjugates. Nuclear targeting could be observed by TEM, suggesting that the cationic peptidic biomolecule is acting as a nuclear localization signal. © 2012 American Chemical Society.

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