Ligand-free synthesis of gold nanoparticles included within cylindrical blocl copolymer films

International audienceWe report a method to include non-functionalized gold nanoparticles (AuNPs) in oriented cylindrical phases of poly(styrene)-b-poly(vinylpyridine) (PS-b-PVP) block copolymers, perpendicular or parallel to a substrate. The combination of AFM, TEM, GISAXS and spectroscopy allows a complete characterization of the nanocomposite. AuNPs are produced by the ultra-sound reduction of a gold salt in the copolymer solution, prior to the deposition of the film by spin-coating. The AuNPs are found to be located within the PVP cylinders exclusively. Sizes from 2 to 4 nm are tuned as a function of the initial gold salt concentration. A seeded-growth of these pre-formed AuNPs was also achieved by a further ultra-sound treatment to produce larger AuNPs (up to d=10 nm) with plasmon resonance properties. For parallel cylinders, the presence of AuNPs in the PVP domains disturbs the organization, while, for perpendicular cylinders, the PVP domains are swollen without any change in their orientation. The synthesis of AuNPs inside the copolymer was also performed by radiolysis, through the irradiation of the copolymer solution or the copolymer film, both containing the gold salt. In these cases, the presence of plasmonic AuNPs was also evidenced. Offering a control of the AuNPs size (< 2 nm to 10 nm) and location, the presented method is a unique way of inserting plasmonic AuNPs into oriented cylinders for reaching anisotropic geometries of valuable interest for optic

Ligand-free synthesis of gold nanoparticles incorporated within oriented cylindrical block copolymer films

Mixing gold nanoparticles with nanostructured block copolymer films is a self-assembled way of building potential optical metamaterials. We report here the inclusion of gold nanoparticles (AuNPs) without pre-functionalization step in oriented films of block copolymer poly(styrene)-b-poly(vinylpyridine) (PS-b-PVP) on a substrate. After deposition with an appropriate solvent, PS-b-P4VP and PS-b-P2VP are cast as films presenting either perpendicular and parallel cylinders. By including gold salt in these solutions and operating subsequent sonication, AuNPs (with a diameter of 2 nm) are synthetized and found located inside the cylinders of PVP (Fig.1) after deposition of the film by spin-coating. 1 Increasing the initial amount of gold precursors allows the formation of bigger AuPs (d=4 nm). The seeded-growth of the pre-formed AuNPs was also achieved in order to get bigger AuNPs (d=8 nm) with plasmon resonance properties. This method was found more efficient in order to get bigger nanoparticles with a low quantity of gold precursor. The presence of AuNPs in the PVP domains disturbs the organization of the parallel cylinders, while it swells the PVP domains in the case of the perpendicular cylinders without changing their orientation. The formation of AuNPs inside a copolymer was also performed by radiolysis, through the irradiation of the copolymer solution and the copolymer film, both containing the gold salt, and led to similar results. The presence of plasmonic AuNPs of small diameter ($\sim$3-4 nm) was evidenced in both cases. GISAXS measurements are presented to characterize and compare the films order before and after gold inclusion, and help proving that cylinder are perpendicular to the substrate through the entire thickness. If time allows, first optical characterizations of the polymer-gold films will be presented

Ligand-free synthesis of gold nanoparticles incorporated within oriented cylindrical block copolymer films : towards optical metamaterials

We report a method to incorporate non-functionalized gold nanoparticles (AuNPs) in oriented cylindrical phases of poly(styrene)-b-poly(vinylpyridine) (PS-b-PVP) block copolymers, perpendicular to a substrate. The combination of AFM, TEM, GISAXS and spectroscopy allows complete characterization of the nanocomposites. AuNPs are produced by the ultra-sound reduction of a gold salt in the copolymer solution, prior to the deposition of the films by spin-coating. The AuNPs are found to be located within the PVP cylinders exclusively. The seeded-growth of these pre-formed AuNPs by a further ultra-sound treatment produced plasmonic AuNPs (up to d =10 nm). For perpendicular cylinders, the PVP domains are swollen without any change in their orientation. Ellipsometric optical properties of these plasmonic AuNPs embeded into oriented cylinders show a definite extinction in reflectivity at a precise energy and incidence angle

Fresh and in vitro osteodifferentiated human amniotic membrane, alone or associated with an additional scaffold, does not induce ectopic bone formation in Balb/c mice.

IF 1.331International audienceThe human amniotic membrane (hAM) has been successfully used as a natural carrier containing amniotic mesenchymal stromal cells, epithelial cells and growth factors. It has a little or no immunogenicity, and possesses useful anti-microbial, anti-inflammatory, anti-fibrotic and analgesic properties. It has been used for many years in several indications for soft tissue repair. We previously reported that hAM represents a natural and preformed sheet containing highly potent stem cells, and could thus be used for bone repair. Indeed, native hAM possesses pre-osteoblastic potential that can easily be stimulated, even as far as mineralization, by means of in vitro osteogenic culture. However, cell culture induces damage to the tissue, as well as to cell phenotype and function. The aim of this study was to evaluate new bone formation by fresh and in vitro osteodifferentiated hAM, alone or associated with an additional scaffold presenting osteoinductive properties. Moreover, we also aimed to determine the effect of in vitro hAM pre-osteodifferentiation on its in vivo biocompatibility/tissue degradation. Results showed that neither fresh nor osteodifferentiated hAM induced ectopic bone formation, whether or not it was associated with the osteoinductive scaffold. Secondly, fresh and osteodifferentiated hAM presented similar in vivo tissue degradation, suggesting that in vitro hAM pre-osteodifferentiation did not influence its in vivo biocompatibility

In vitro osteodifferentiation of intact human amniotic membrane is not beneficial in the context of bone repair

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