| 1. |
- Crassous, Jerome, et al.
(författare)
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Giant hollow fiber formation through self-assembly of oppositely charged polyelectrolyte brushes and gold nanoparticles
- 2013
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 9:38, s. 9111-9118
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Tidskriftsartikel (refereegranskat)abstract
- We report on the use of binary mixtures of oppositely charged gold nanoparticles (AuNPs) and spherical polyelectrolyte brushes (SPBs), consisting of a polystyrene core onto which long polystyrene sulfonate chains are grafted, as a simple model system to investigate the influence of directional interactions on self-assembly. We demonstrate that the mixing ratio, i.e., the number of AuNPs per SPB, has a profound influence on self-assembly. In particular we report on the formation of giant hollow fibers, and present a thorough characterization of these nanostructures. We speculate that the adsorption of a few AuNPs on the SPBs appears to direct the tubular self-assembly, and discuss the analogy to the case of modified proteins such as tubulin under the action of nucleotides.
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| 2. |
- Crassous, Jerome, et al.
(författare)
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Preparation and characterization of ellipsoidal-shaped thermosensitive microgel colloids with tailored aspect ratios
- 2012
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 8:13, s. 3538-3548
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Tidskriftsartikel (refereegranskat)abstract
- Prolate model colloids with defined properties can be obtained by the stretching of spherical polymeric particles, which is well-known for polystyrene and poly(methyl methacrylate) latices. The present study aims to extend this approach to functional core-shell particles in order to achieve a new class of anisotropic colloidal materials where both the aspect ratio and the effective volume fraction can be controlled by temperature. We describe the synthesis and characterization of these functional anisotropic core-shell particles consisting of a polystyrene (PS) core onto which a crosslinked thermoresponsive microgel shell of poly(N-isopropylmethacrylamide) (PNIPMAm) was grafted. Embedded into a film of polyvinylalcohol (PVA), the spherical composite microgels are heated above the glass transition temperature (T-g) of the polystyrene core and then stretched with different deformations g. During the stretching, the particles adopt an elongated shape, that they retain after cooling to room temperature as confirmed by small-angle X-ray scattering performed on the films. Anisotropic composite microgels with aspect ratios ranging from 2.2 to 6.5 are recovered after dissolution of the PVA and purification, and are fully characterized by diverse methods such as transmission electron microscopy, confocal microscopy and light scattering. The temperature sensitivity of these anisotropic composite microgels is maintained as confirmed by dynamic light scattering and cryogenic electron microscopy performed below and above the volume phase transition of the shell.
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| 3. |
- Hallan, Supandeep Singh, et al.
(författare)
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Design and Characterization of Ethosomes for Transdermal Delivery of Caffeic Acid.
- 2020
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Ingår i: Pharmaceutics. - : MDPI. - 1999-4923. ; 12:8
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Tidskriftsartikel (refereegranskat)abstract
- in ethosome after six months, while in water, an almost complete degradation occurred within one month. The addition of poloxamer slightly modified vesicle structure and size, while it decreased the vesicle deformability. Caffeic acid diffusion coefficients from ethosome and ethosome gel were, respectively, 137- and 33-fold lower with respect to the aqueous solution. At last, the caffeic acid permeation and antioxidant power of ethosome were more intense with respect to the simple solution.
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| 4. |
- Hallan, Supandeep Singh, et al.
(författare)
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The Potential of Caffeic Acid Lipid Nanoparticulate Systems for Skin Application : In Vitro Assays to Assess Delivery and Antioxidant Effect
- 2021
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Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- The object of this study is a comparison between solid lipid nanoparticles and ethosomes for caffeic acid delivery through the skin. Caffeic acid is a potent antioxidant molecule whose cutaneous administration is hampered by its low solubility and scarce stability. In order to improve its therapeutic potential, caffeic acid has been encapsulated within solid lipid nanoparticles and ethosomes. The effect of lipid matrix has been evaluated on the morphology and size distribution of solid lipid nanoparticles and ethosomes loaded with caffeic acid. Particularly, morphology has been investigated by cryogenic transmission electron microscopy and small angle X-ray scattering, while mean diameters have been evaluated by photon correlation spectroscopy. The antioxidant power has been evaluated by the 2,2-diphenyl-1-picrylhydrazyl methodology. The influence of the type of nanoparticulate system on caffeic acid diffusion has been evaluated by Franz cells associated to the nylon membrane, while to evaluate caffeic acid permeation through the skin, an amperometric study has been conducted, which was based on a porcine skin-covered oxygen electrode. This apparatus allows measuring the O2 concentration changes in the membrane induced by polyphenols and H2O2 reaction in the skin. The antioxidative reactions in the skin induced by caffeic acid administered by solid lipid nanoparticles or ethosomes have been evaluated. Franz cell results indicated that caffeic acid diffusion from ethosomes was 18-fold slower with respect to solid lipid nanoparticles. The amperometric method evidenced the transdermal delivery effect of ethosome, indicating an intense antioxidant activity of caffeic acid and a very low response in the case of SLN. Finally, an irritation patch test conducted on 20 human volunteers demonstrated that both ethosomes and solid lipid nanoparticles can be safely applied on the skin.
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| 5. |
- Kellermeier, Matthias, et al.
(författare)
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Additive-induced morphological tuning of self-assembled silica-barium carbonate crystal aggregates
- 2009
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 311:8, s. 2530-2541
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Tidskriftsartikel (refereegranskat)abstract
- Crystallisation of barium carbonate from alkaline silica solutions results in the formation of extraordinary micron-scale architectures exhibiting non-crystallographic curved shapes, such as helical filaments and worm-like braids. These so-called "silica biomorphs" consist of a textured assembly of uniform elongated witherite nanocrystallites, which is occasionally sheathed by a skin of amorphous silica. Although great efforts have been devoted to clarifying the physical origin of these fascinating materials, to date little is known about the processes underlying the observed self-organisation. Herein, we describe the effect of two selected additives, a cationic surfactant and a cationic polymer, on the morphology of the forming crystal aggregates, and relate changes to experiments conducted in the absence of additives. Minor amounts of both substances are shown to exert a significant influence on the growth process, leading to the formation of predominantly flower-like spherulitic aggregates. The observed effects are discussed in terms of feasible morphogenesis pathways. Based on the assumption of a template membrane steering biomorph formation, it is proposed that the two additives are capable of performing specific bridging functions promoting the aggregation of colloidal silica which constitutes the membrane. Morphological changes are tentatively ascribed to varying colloid coordination effecting distinct membrane curvatures. (C) 2009 Elsevier B.V. All rights reserved.
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| 6. |
- Rochette, Christophe N., et al.
(författare)
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Shell Structure of Natural Rubber Particles: Evidence of Chemical Stratification by Electrokinetics and Cryo-TEM
- 2013
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 29:47, s. 14655-14665
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Tidskriftsartikel (refereegranskat)abstract
- The interfacial structure of natural rubber (NR) colloids is investigated by means of cryogenic transmission electron microscopy (cryo-TEM) and electrokinetics over a broad range of KNO3 electrolyte concentrations (4-300 mM) and pH values (1-8). The asymptotic plateau value reached by NR electrophoretic mobility (mu) in the thin double layer limit supports the presence of a soft (ion- and water-permeable) polyelectrolytic type of layer located at the periphery of the NR particles. This property is confirmed by the analysis of the electron density profile obtained from cryo-TEM that evidences a similar to 2-4 nm thick corona surrounding the NR polyisoprene core. The dependence of mu on pH and salt concentration is further marked by a dramatic decrease of the point of zero electrophoretic mobility (PZM) from 3.6 to 0.8 with increasing electrolyte concentration in the range 4-300 mM. Using a recent theory for electrohydrodynamics of soft multilayered particles, this "anomalous" dependence of the PZM on electrolyte concentration is shown to be consistent with a radial organization of anionic and cationic groups across the peripheral NR structure. The NR electrokinetic response in the pH range 1-8 is indeed found to be equivalent to that of particles surrounded by a positively charged similar to 3.5 nm thick layer (mean dissociation pK similar to 4.2) supporting a thin and negatively charged outermost layer (0.6 nm in thickness, pK similar to 0.7). Altogether, the strong dependence of the PZM on electrolyte concentration suggests that the electrostatic properties of the outer peripheral region of the NR shell are mediated by lipidic residues protruding from a shell containing a significant amount of protein-like charges. This proposed NR shell interfacial structure questions previously reported NR representations according to which the shell consists of either a fully mixed lipid protein layer, or a layer of phospholipids residing exclusively beneath an outer proteic film.
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