Polymer multilayer films obtained by electrochemically catalyzed click chemistry.

We report the covalent layer-by-layer construction of polyelectrolyte multilayer (PEM) films by using an efficient electrochemically triggered Sharpless click reaction. The click reaction is catalyzed by Cu(I) which is generated in situ from Cu(II) (originating from the dissolution of CuSO(4)) at the electrode constituting the substrate of the film. The film buildup can be controlled by the application of a mild potential inducing the reduction of Cu(II) to Cu(I) in the absence of any reducing agent or any ligand. The experiments were carried out in an electrochemical quartz crystal microbalance cell which allows both to apply a controlled potential on a gold electrode and to follow the mass deposited on the electrode through the quartz crystal microbalance. Poly(acrylic acid) (PAA) modified with either alkyne (PAA(Alk)) or azide (PAA(Az)) functions grafted onto the PAA backbone through ethylene glycol arms were used to build the PEM films. Construction takes place on gold electrodes whose potentials are more negative than a critical value, which lies between -70 and -150 mV vs Ag/AgCl (KCl sat.) reference electrode. The film thickness increment per bilayer appears independent of the applied voltage as long as it is more negative than the critical potential, but it depends upon Cu(II) and polyelectrolyte concentrations in solution and upon the reduction time of Cu(II) during each deposition step. An increase of any of these latter parameters leads to an increase of the mass deposited per layer. For given buildup conditions, the construction levels off after a given number of deposition steps which increases with the Cu(II) concentration and/or the Cu(II) reduction time. A model based on the diffusion of Cu(II) and Cu(I) ions through the film and the dynamics of the polyelectrolyte anchoring on the film, during the reduction period of Cu(II), is proposed to explain the major buildup features.journal articleresearch support, non-u.s. gov't2010 Feb 16importe

Eco-friendly processes for the synthesis of amorphous calcium carbonate nanoparticles in ethanol and their stabilisation in aqueous media

International audienceAmorphous calcium carbonate nanoparticles (ACC NPs) are promising multifunctional materials for healthcare applications. Due to their instability in aqueous media, pure ACC NPs for the biomedical field are increasingly synthesised in absolute ethanol, using the ammonia diffusion method (ADM). Although this method presents the advantage of providing stable ACC NPs without additives, it requires the use of pure ethanol as solvent. New insights into the formation mechanisms of ACC NPs in ethanol using gas diffusion are presented in this article. The optimisation of the process according to these findings can increase the mass concentration of ACC NPs by a factor of 3.5. As a result, the amount of ethanol required to produce a target mass of particles is significantly decreased, reducing the ecological impact of the process. The stabilisation of the resulting ACC NPs in aqueous media is achieved by a short-time process using phospholipids based on the ethanol injection method. By using the natural electrostatic affinity of negatively charged materials for the positive surface of ACC NPs in ethanol, we reduced the process time from 24 h to 2 minutes, compared with the closest state of the art, decreasing the operating time and corresponding energy consumption. The process does not require the use of synthetic PEGylated lipids for steric stabilisation. In addition, a natural egg-sourced phospholipid was identified as an efficient stabiliser for the first time. The upscaling of our process was successfully demonstrated using a 50 L reactor for bulk synthesis, as well as a continuous flow reactor for industrial continuous flow production

Design of a Liposomal Candidate Vaccine Against Pseudomonas aeruginosa and its Evaluation in Triggering Systemic and Lung Mucosal Immunity

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Positive effect of cold atmospheric nitrogen plasma on the behavior of mesenchymal stem cells cultured on a bone scaffold containing iron oxide-loaded silica nanoparticles catalyst

Low-temperature atmospheric pressure plasma was demonstrated to have an ability to generate different reactive oxygen and nitrogen species (RONS), showing wide biological actions. Within this study, mesoporous silica nanoparticles (NPs) and FexOy/NPs catalysts were produced and embedded in the polysaccharide matrix of chitosan/curdlan/hydroxyapatite biomaterial. Then, basic physicochemical and structural characterization of the NPs and biomaterials was performed. The primary aim of this work was to evaluate the impact of the combined action of cold nitrogen plasma and the materials produced on proliferation and osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells (ADSCs), which were seeded onto the bone scaffolds containing NPs or FexOy/NPs catalysts. Incorporation of catalysts into the structure of the biomaterial was expected to enhance the formation of plasma-induced RONS, thereby improving stem cell behavior. The results obtained clearly demonstrated that short-time (16s) exposure of ADSCs to nitrogen plasma accelerated proliferation of cells grown on the biomaterial containing FexOy/NPs catalysts and increased osteocalcin production by the cells cultured on the scaffold containing pure NPs. Plasma activation of FexOy/NPs-loaded biomaterial resulted in the formation of appropriate amounts of oxygen-based reactive species that had positive impact on stem cell proliferation and at the same time did not negatively affect their osteogenic differentiation. Therefore, plasma-activated FexOy/NPs-loaded biomaterial is characterized by improved biocompatibility and has great clinical potential to be used in regenerative medicine applications to improve bone healing process.Peer ReviewedPostprint (published version

Original Basic Activation for Enhancing Silica Particle Reactivity: Characterization by Liquid Phase Silanization and Silica-Rubber Nanocomposite Properties

Silica fillers are used in various nanocomposites in combination with silanes as a reinforcing filler. In tire technology, silica is generally functionalized before (pre-treated) or during mixing (in-situ silanization or post-treated). In both cases, a soft base catalyst (e.g., triethylamine or diphenyl guanidine, DPG) is typically used to accelerate and increase the yield of the silane/silica coupling reaction. In this study, we investigated how pre-treatments of silica particles with either strong amine or hydride bases impact the silanization of silica prior to or during SBR mixing for silica-rubber nanocomposite fabrication. Our findings are supported by molecular characterization (solid state 29Si NMR, 1H NMR and TGA), and scanning electron microscopy. In addition, the impact of these silica pre-treatments on a nanocomposite’s mechanical properties was evaluated using dynamic mechanical analysis (DMA)

Do the pristine physico-chemical properties of silver and gold nanoparticles influence uptake and molecular effects on Gammarus fossarum (Crustacea Amphipoda)?

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Photoinduced effects of m-tetrahydroxyphenylchlorin loaded lipid nanoemulsions on multicellular tumor spheroids

Background Photosensitizers are used in photodynamic therapy (PDT) to destruct tumor cells, however, their limited solubility and specificity hampers routine use, which may be overcome by encapsulation. Several promising novel nanoparticulate drug carriers including liposomes, polymeric nanoparticles, metallic nanoparticles and lipid nanocomposites have been developed. However, many of them contain components that would not meet safety standards of regulatory bodies and due to difficulties of the manufacturing processes, reproducibility and scale up procedures these drugs may eventually not reach the clinics. Recently, we have designed a novel lipid nanostructured carrier, namely Lipidots, consisting of nontoxic and FDA approved ingredients as promising vehicle for the approved photosensitizer m-tetrahydroxyphenylchlorin (mTHPC). Results In this study we tested Lipidots of two different sizes (50 and 120 nm) and assessed their photodynamic potential in 3-dimensional multicellular cancer spheroids. Microscopically, the intracellular accumulation kinetics of mTHPC were retarded after encapsulation. However, after activation mTHPC entrapped into 50 nm particles destroyed cancer spheroids as efficiently as the free drug. Cell death and gene expression studies provide evidence that encapsulation may lead to different cell killing modes in PDT. Conclusions Since ATP viability assays showed that the carriers were nontoxic and that encapsulation reduced dark toxicity of mTHPC we conclude that our 50 nm photosensitizer carriers may be beneficial for clinical PDT applications

The effect of low temperature atmospheric nitrogen plasma on MC3T3-E1 preosteoblast proliferation and differentiation in vitro

The aim of this work was to evaluate the impact of atmospheric pressure nitrogen plasma on viability, proliferation, and osteogenic differentiation of normal mouse calvarial preosteoblasts (MC3T3-E1 Subclone 4), which were maintained in Hanks’ balanced salt solution (HBSS)during plasma exposure. Obtained results clearly demonstrated that short-time (4, 8, and 16 s) nitrogen plasma treatment is non-toxic to the MC3T3-E1 cells, does not affect cell morphology, promotes reosteoblasts’ proliferation, enhances osteogenic differentiation by increasing bone alkaline phosphatase and osteocalcin concentration, but inhibits mineralization of extracellular matrix. The best results were achieved for 16 s exposure time and when the preosteoblasts were left in HBSS for 3 h after plasma treatment. Presented studies indicate great clinical potential of cold atmospheric nitrogen plasma for regenerative medicine applications to improve bone healing process