Direct Photomodification of Polymer Surfaces: Unleashing the Potential of Aryl-Azide Copolymers

International audienceThe possibility to impart surface properties to any polymeric substrate using a fast, reproducible, and industrially friendly procedure, without the need for surface pretreatment, is highly sought after. This is in particular true in the frame of antibacterial surfaces to hinder the threat of biofilm formation. In this study, the potential of aryl‐azide polymers for photofunctionalization and the importance of the polymer structure for an efficient grafting are demonstrated. The strategy is illustrated with a UV‐reactive hydrophilic poly(2‐oxazoline) based copolymer, which can be photografted onto any polymer substrate that contains carbon–hydrogen bonds to introduce antifouling properties. Through detailed characterization it is demonstrated that the controlled spatial distribution of the UV‐reactive aryl‐azide moieties within the poly(2‐oxazline) structure, in the form of pseudogradient copolymers, ensures higher grafting efficacy than other copolymer structures including block copolymers. Furthermore, it is found that the photografting results in a covalently bound layer, which is thermally stable and causes a significant antiadherence effect and biofilm reduction against Escherichia coli and Staphylococcus epidermidis strains while remaining noncytotoxic against mouse fibroblasts

PLA scaffolds production from Thermally Induced Phase Separation: effect of process parameters and development of an environmentally improved route assisted by supercritical carbon dioxide

In this work, a relatively large scale of PLA scaffolds was produced using thermally induced phase separation (TIPS) combined with a supercritical carbon dioxide (SC-CO2) drying step as a green alternative. For the TIPS step, the phase separation of PLA and 1,4-dioxane solvent was controlled by adjusting the process conditions such as the polymer concentration and molecular weight, the 1,4-dioxane solvent power and the cooling conditions. The scaffolds morphology was analyzed by scanning electron microscopy. Their structural and mechanical properties were correlated together with the possibility to tune them by controlling the process conditions. An environmental analysis using the Life Cycle Assessment (LCA) methodology confirmed a reduction of at least 50% of the environmental impact of the whole process using the SC-CO2 drying compared to the traditional freeze-drying technology. This work is the first known attempt to conduct the LCA methodology on TIPS process for the PLA scaffolds production

Biomechanical behaviour of human bile duct wall and impact of cadaveric preservation processes.

International audienceBiliary diseases are the third most common cause of surgical digestive disease. There is a close relationship between the mechanical performance of the bile duct and its physiological function. Data of biomechanical properties of human main bile duct are scarce in literature. Furthermore, mechanical properties of soft tissues are affected by these preservation procedures. The aim of the present work was, on the one hand, to observe the microstructure of the human bile duct by means of histological analysis, on the other hand, to characterize the mechanical behavior and describe the impact of different preservation processes. A mechanical study in a controlled environment consisting of cyclic tests was made. The results of the mechanical tests are discussed and explained using the micro-structural observations. The results show an influence of the loading direction, which is representative of an anisotropic behavior. A strong hysteresis due to the viscoelastic properties of soft tissues was also observed. Embalming and freezing preservation methods had an impact on the biomechanical properties of human main bile duct, with fiber network deterioration. That may further provide a useful quantitative baseline for anatomical and surgical training using embalming and freezing

Interaction of gentamicin sulfate with alginate and consequences on the physico-chemical properties of alginate-containing biofilms

BACKGROUND: Alginate is one of the main extracellular polymeric substances (EPS) in biofilms of Cystic Fibrosis (CF) patients suffering from pulmonary infections. Gentamicin sulfate (GS) can strongly bind to alginate resulting in loss of pharmacological activity; however neither the mechanism nor its repercussion is fully understood. In this study, we investigated how GS modifies the alginate macromolecular network and its microenvironment. MATERIAL AND METHODS: Alginate gels of two different compositions (either enriched in guluronate units (G) or enriched in mannuronate units (M)) were crosslinked with Ca and exposed to GS at varying times and concentrations. The complexes formed were characterized via turbidimetry, mechanical tests, swelling assay, calorimetry techniques, nuclear magnetic resonance, Ca displacement, macromolecular probe diffusion and pH alteration. RESULTS: In presence of GS, the alginate network and its environment undergo a tremendous reorganization in terms of gel density, stiffness, diffusion property, presence and state of the water molecules. We noted that the intensity of those alterations is directly dependent on the polysaccharide motif composition (ratio M/G). CONCLUSION: Our results underline the importance of alginate as biofilm component, its pernicious role during antibiotherapy and could represent a potential macromolecular target to improve anti-infectious therapies

Functionalized PCL/HA nanocomposites as microporous membranes for bone regeneration

In the present work, microporous membranes based on poly(ε-caprolactone) (PCL) and PCL functionalized with amine (PCL-DMAEA) or anhydride groups (PCL-MAGMA) were realized by solvent-non solvent phase inversion and proposed for use in Guided Tissue Regeneration (GTR). Nanowhiskers of hydroxyapatite (HA) were also incorporated in the polymer matrix to realize nanocomposite membranes. Scanning Electron Microscopy (SEM) showed improved interfacial adhesion with HA for functionalized polymers, and highlighted substantial differences in the porosity. A relationship between the developed porous structure of the membrane and the chemical nature of grafted groups was proposed. Compared to virgin PCL, hydrophilicity increases for functionalized PCL, while the addition of HA influences significantly the hydrophilic characteristics only in the case of virgin polymer. A significant increase of in vitro degradation rate was found for PCL-MAGMA based membranes, and at lower extent of PCL-DMAEA membranes. The novel materials were investigated regarding their potential as support for cell growth in bone repair using multipotent mesenchymal stromal cells (MSC) as a model. MSC plated onto the various membranes were analyzed in terms of adhesion, proliferation and osteogenic capacity that resulted to be related to chemical as well as porous structure. In particular, PCL-DMAEA and the relative nanocomposite membranes are the most promising in terms of cell-biomaterial interactions

Copolymère hydrophobe visible en IRM

The invention relates to a hydrophobic thermoplastic copolymer which is in particular of use for manufacturing and/or coating medical devices, in particular implantable medical devices, characterized in that it is obtained by copolymerization, and in that it comprises at least one first monomer unit and at least one second monomer unit onto which is grafted a paramagnetic-ion-chelating ligand which can complex with such a paramagnetic ion or a paramagnetic-ion-chelating ligand which is complexed with such a paramagnetic ion, wherein the second monomer unit is grafted in sufficient amount for the copolymer to be visible in magnetic resonance imaging when it is complexed with said paramagnetic ion. The invention also relates to a method for obtaining said hydrophobic thermoplastic copolymer

Development of an eco-friendly Thermal Induced Phase Separation (TIPS) process assisted by supercritical CO2 for the production of PLA scaffolds with tunable structural and mechanical properties

Many routes are nowadays utilized for the production of PLA scaffolds. In this study, a relative large scale of scaffolds was produced combining thermal induced phase separation and supercritical CO2 as a green alternative drying. The phase separation between polylactic acid and 1,4-dioxane was monitored by adjusting the process parameters such as the polymer concentration, the molecular weight, the solvent power and the cooling conditions. The morphologic changes occurring during the phase separation were analyzed by scanning electron microscopy. Structural and mechanical properties of scaffolds were correlated and it was possible to tune them depending on the process parameters. Moreover, an environmental analysis of the thermal induced phase separation (TIPS) process and the comparison between supercritical CO2 and the traditional freeze drying technologies were investigated. This work is the first known attempt to conduct the life cycle assessment (LCA) methodology on TIPS process and the polylactic acid scaffolds production. The results of the LCA have demonstrated that using supercritical-CO2 drying technology allows to reduce by at least 50 % the environmental impact of the whole process and to drastically diminish the production time

MRI-visible polymer based on poly(methyl methacrylate) for imaging applications

Macromolecular contrast agents are very attractive to afford efficient magnetic resonance imaging (MRI) visualization of implantable medical devices. In this work, we report on the grafting of a Gd-based DTPA contrast agent onto a poly(methyl methacrylate) derivative backbone by combining free radical polymerization and copper-catalyzed azide-alkyne cycloaddition (CuAAC). Using free radical polymerization, poly(methyl methacrylate-co-propargyl methacrylate) copolymers were prepared with a control of the ratio in propargyl methacrylate monomer units. The synthesis of a new azido monofunctionalized DTPA ligand was also reported and characterized by 1H NMR and mass spectroscopy. After complexation with gadolinium, this ligand has been grafted on the polymer backbone by click chemistry reaction. The obtained macromolecular contrast agent was then coated on a polypropylene mesh using the airbrushing technique and the mesh was assessed for MRI visualization at 7 teslas. The polymeric contrast agent was also tested for cytocompatibility and stability to assess its suitability for biomedical applications

Controlled Anchoring of Iron-Oxide Nanoparticles on Polymeric Nanofibers: Easy Access to Core@Shell Organic-Inorganic Nanocomposites for Magneto-Scaffolds

Composites combining superparamagnetic iron oxide nanoparticles (SPIONs) and polymers are largely present in modern (bio)materials. However, while SPIONs embedded in polymer matrices are classically reported, the mechanical and degradation properties of the polymer scaffold are impacted by the SPIONs. Therefore, the controlled anchoring of SPIONs onto polymer surfaces is still a major challenge. Herein, we propose an efficient strategy for the direct and uniform anchoring of SPIONs on the surface of functionalized-polylactide (PLA) nanofibers via a simple free ligand exchange procedure to design PLA@SPIONs core@shell nanocomposites. The resulting PLA@SPIONs hybrid biomaterials are characterized by electron microscopy (SEM and TEM) and EDXS analysis, to probe the morphology and detect elements present at the organic/inorganic interface, respectively. A monolayer of SPIONs with a complete and homogeneous coverage is observed on the surface of PLA nanofibers. Magnetization experiments show that magnetic properties of the nanoparticles are well-preserved after their grafting on the PLA fibers and that the size of the nanoparticles does not change. The absence of cytotoxicity, combined with a high sensitivity of detection in MRI both in vitro and in vivo make these hybrid nanocomposites attractive for the development of magnetic biomaterials for biomedical applications