Search

International audience; The integration of nanoparticles (NPs) into photonic devices and plasmonic sensors requires selective patterning of these NPs with fine control of their size, shape, and spatial positioning. In this article, we report on a general strategy to pattern different types of NPs. This strategy involves the functionalization of photopolymers before their patterning by two-photon laser writing to fabricate micro- and nanostructures that selectively attract colloidal NPs with suitable ligands, allowing their precise immobilization and organization even within complex 3D structures. Monolayers of NPs without aggregations are obtained and the surface density of NPs on the polymer surface can be controlled by changing either the time of immersion in the colloidal solution or the type of amine molecule chemically grafted on the polymer surface. Different types of NPs (gold, silver, polystyrene, iron oxide, colloidal quantum dots, and nanodiamonds) of different sizes are introduced showing a potential toward nanophotonic applications. To validate the great potential of our method, we successfully demonstrate the integration of quantum dots within a gold nanocube with high spatial resolution and nanometer precision. The promise of this hybrid nanosource of light (plasmonic/polymer/QDs) as optical nanoswitch is illustrated through photoluminescence measurements under polarized exciting light.

Background: Clinical management of ischemic events and prevention of vascular disease is based on antiplatelet drugs. Given the relevance of phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) as a candidate target in thrombosis, the main goal of the present study was to identify novel antiplatelet agents within the existing inhibitors blocking PI3K isoforms. Methods: We performed a biological evaluation of the pharmacological activity of PI3K inhibitors in platelets. The effect of the inhibitors was evaluated in intracellular calcium release and platelet functional assays, the latter including aggregation, adhesion, and viability assays. The in vivo drug antithrombotic potential was assessed in mice undergoing chemically induced arterial occlusion, and the associated hemorrhagic risk evaluated by measuring the tail bleeding time. Results: We show that PI3K Class IA inhibitors potently block calcium mobilization in human platelets. The PI3K p110δ inhibitor Idelalisib inhibits platelet aggregation mediated by ITAM receptors GPVI and CLEC-2, preferentially by the former. Moreover, Idelalisib also inhibits platelet adhesion and aggregation under shear and adhesion to collagen. Interestingly, an antithrombotic effect was observed in mice treated with Idelalisib, with mild bleeding effects at high doses of the drug. Conclusion: Idelalisib may have antiplatelet effects with minor bleeding effects, which provides a rationale to evaluate its antithrombotic efficacy in humans.

International audience; A new methodology is developed to determine the shape distribution of gold nanoparticles (NPs) from optical spectroscopic measurements. Indeed, the morphology of Au colloids is deduced by fitting their absorption spectra with an effective medium theory which takes into account the nanoparticle shape distribution. The same procedure is applied to ellipsometric measurements recorded on photoresist films which contain Au NPs. Three spaces (L2, r2, P2) are introduced to interpret the NPs shape distribution. In the P2 space, the sphericity, the prolacity and the oblacity estimators are proposed to quantify the shape of NPs. The r2 space enables the determination of the NP aspect ratio distribution. The distributions determined from optical spectroscopy were found to be in very good agreement with the shape distributions obtained by transmission electron microscopy. We found that fitting absorption or ellipsometric spectra with an adequate effective medium theory, provides a robust tool for measuring the shape and concentration of metallic NPs.

International audience; This paper reports the complete ellipsometric characterization of gold nanoparticles (NPs) embedded in a photoresist films. The effective dielectric function of nanocomposite films as well as the shape distribution and the volume fraction of NPs are extracted from ellipsometric measurements by introducing an effective medium theory which takes into account the NP shape distribution and the intrinsic confinement effect. This theory remains valid as long as the nanoparticle interaction is negligible. We show that the magnitude of the confinement depends on the nanoparticle shape and the environment through chemical damping. This suggests that the NP shape distribution can be directly estimated by ellipsometry, while the determination of absolute radius distribution requires transmission electron microscopy measurements. The imaginary part of the effective dielectric function exhibits a strong asymmetric surface plasmon band, while a large variation of the real part occurs close to the resonance. The redshift and the broadening of the plasmon band as the gold volume fraction increases are correlated to the evolution of NP shape distribution. This evolution is attributed to a competition between the nucleation and the coalescence of NPs. This unambiguously demonstrates that ellipsometry combined with a shape-distributed effective medium theory is a powerful alternative tool to transmission electron microscopy for the NP shape analysis.

International audience; The preparation method of nanoporous poly(methyl methacrylate)( PMMA) containing silver nanoparticles self-organized in rings is highly adaptable, yielding a variety of materials of controllable pore size (ranging from 200 nm to over 5 mu m), nanoparticle size (20 to 200 nm), surface coverage and silver precursor concentration. In this article, it is optimized aiming at a best performance as enhancers for Surface Enhanced Raman Spectroscopy. The versatility of these sensors is shown by multi-wavelength excitation experiment at 457, 488, 514 and 633 nm. Finally, the efficiency of 2,2'-bipyridine, 4,4'-bipyridine and trans-bis-(4,4'-bipyridyl) ethylene as SERS probe molecules is compared using PMMA/Ag-rings. Ag+ ions are shown to play an important role in the adsorption of the target molecules on these surfaces leading to a SERS enhancement factor of 3.783 108 at 488 nm for trans-bis-(4,4'-bipyridyl) ethylene.

International audience

Upon stimulation, platelets release a high number of proteins (the releasate). There are clear indications that these proteins are involved in the pathogenesis of several diseases, such as atherosclerosis. In the present study we compared the platelet releasate following platelet activation with two major endogenous agonists: thrombin and collagen. Proteome analysis was based on 2D-DIGE and LC-MS/MS. Firstly, we showed the primary role of thrombin and collagen receptors in platelet secretion by these agonists; moreover, we demonstrated that GPVI is the primary responsible for collagen-induced platelet activation/aggregation. Proteomic analysis allowed the detection of 122 protein spots differentially regulated between both conditions. After excluding fibrinogen spots, down-regulated in the releasate of thrombin-activated platelets, 84 differences remained. From those, we successfully identified 42, corresponding to 37 open-reading frames. Many of the differences identified correspond to post-translational modifications, primarily, proteolysis induced by thrombin. Among others, we show vitamin K-dependent protein S, an anticoagulant plasma protein, is up-regulated in thrombin samples. Our results could have pathological implications given that platelets might be playing a differential role in various diseases and biological processes through the secretion of different subsets of granule proteins and microvesicles following a predominant activation of certain receptors.

International audience; Fabrication of freestanding, three-dimensional microstructures having gold nanoparticles as building blockshas been achieved using two-photon lithography. The reported constructions hold structural coherencewithout the need of a polymeric network to embed the nanoparticles. The Au nanoparticles areproduced by radical-mediated photoreduction and immediately self-arrange in micrometre-sizedcylinders, which are used as the building units of the 3D structure writing. The manufactured structurespresent plasmonic activity, as well as excellent properties as substrates for Surface-Enhanced RamanSpectroscopy, in key issues such as reproducibility in intensity or enhancement factor. Such is calculatedto be above 8 106 for the non-resonant probe molecule trans-1,2-bis-4-pyridylethylene. The optionof repeated use of the substrates is confirmed, and they are successfully applied for detection of thefungicide thiabendazole.

In this work we have investigated the detection of aminoglutethimide (AGI) drug based on its adsorption on gold nanoparticles employing Surface-Enhanced Raman Spectroscopy (SERS) and plasmon resonance. The adsorption of AGI on Au was studied at different experimental conditions, such as the excitation wavelength, the pH and the concentration, aimed to optimize the trace detection of this drug with possible application in the anti-doping analysis or in bioanalysis. © 2011 The Royal Society of Chemistry., This work has been supported by the Spanish Ministerio de Ciencia e Innovacion (grants FIS2007-63065 and FIS2010-15405) and Comunidad de Madrid through the MICROSERES II network (grant S2009/TIC-1476).

The controlled tuning of interparticle distance at the nanoscale level is a major challenge for nanofabrication of surface-enhanced Raman scattering (SERS) active clusters and their application to molecular sensing. In fact, the geometrical properties of the narrow gaps between nanoparticles play a key role in determining the local field enhancement (and therefore, the SERS enhancement factor) and the spatial enhancement distribution in the gap region. Besides, very short interparticle distances may block the access of the analyte to the hot zone. In this paper, we report the synthesis of silver colloid NP clusters with interparticle distances fine tuned in the ≤2 nm range, by exploiting the chemical properties of linear α,ω-aliphatic diamines as molecular linkers with varying chain length. The bifunctional diamines also form intermolecular cavities within their self-assembled monolayers, suitable to host molecular analytes for nanosensing applications, as evidenced by SERS detection of organochlorine insecticides at the trace level. In this regard, the extension of the aliphatic chain played a crucial role in determining the SAM conformation and thus the final sensitivity of the functionalized SERS substrate. © 2010 Springer Science+Business Media, LLC., Supported by the Spanish Ministerio de Ciencia e Innovación (grant no. FIS2007-63065, FIS2009-11264, and Consolider-Ingenio project EMET CSD2008-00066, Comunidad de Madrid through the MICROSERES network (grant S-0505/TIC-0191), and CSIC