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

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

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

Release Kinetics of Dexamethasone Phosphate from Porous Chitosan: Comparison of Aerogels and Cryogels

Porous chitosan materials as potential wound dressings were prepared via dissolution of chitosan, nonsolvent-induced phase separation in NaOH-water, formation of a hydrogel, and either freeze-drying or supercritical CO2 drying, leading to “cryogels” and “aerogels”, respectively. The hydrophilic drug dexamethasone sodium phosphate was loaded by impregnation of chitosan hydrogel, and the release from cryogel or aerogel was monitored at two pH values relevant for wound healing. The goal was to compare the drug-loading efficiency and release behavior from aerogels and cryogels as a function of the drying method, the materials’ physicochemical properties (density, morphology), and the pH of the release medium. Cryogels exhibited a higher loading efficiency and a faster release in comparison with aerogels. A higher sample density and lower pH value of the release medium resulted in a more sustained release in the case of aerogels. In contrast, for cryogels, the density and pH of the release medium did not noticeably influence release kinetics. The Korsmeyer-Peppas model showed the best fit to describe the release from the porous chitosan materials into the different media

Roadmap on multifunctional materials for drug delivery

This Roadmap on drug delivery aims to cover some of the most recent advances in the field of materials for drug delivery systems (DDSs) and emphasizes the role that multifunctional materials play in advancing the performance of modern DDS s in the context of the most current challenges presented. The Roadmap is comprised of multiple sections, each of which introduces the status of the field, the current and future challenges faced, and a perspective of the required advances necessary for biomaterial science to tackle these challenges. It is our hope that this collective vision will contribute to the initiation of conversation and collaboration across all areas of multifunctional materials for DDSs. We stress that this article is not meant to be a fully comprehensive review but rather an up-to-date snapshot of different areas of research, with a minimal number of references that focus upon the very latest research developments

Covalent and/or dynamic networks for elastomeric self-healable degradable devices

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Development of a macromolecular platform to yield functional degradable networks with actuation, self-healing and/or bioadhesion properties

International audienc

Degradable star block copolymers as highly versatile architectures for biomedical Applications

International audienc

Insights into (multi)functional polyester biomaterials in biomedical applications : from drug delivery to medical devices

International audienc

SYNTHESE ET CARACTERISATION DE NOUVEAUX POLYESTERS BIODEGRADABLES ET HYDROSOLUBLES A FONCTIONS CATIONIQUES OU AMPHOTERES

A bibliographic review relating to grafted copolymers being both cationic, or amphoteric, and partially degradable allowed to highlight the lack of such compounds in the current literature. The aim of this thesis is to generate such compounds starting with poly((e-caprolactone) (PCL) as raw material and using an anionic modification method newly described for this polyester. Two main strategies based on a macropolycarbanionic PCL intermediate were followed. The first strategy uses the macropolycarbanion as a nucleophilic agent able to react with small electrophilic organic molecules. These substitution reactions allowed us to synthesise PCL based copolymers containing from 10 to 15% of functionalized units bearing cationic (ammonium, phosphonium), or hydrophilic groups (amine, carboxylic acid). These functionalized PCL can be further used within post-modification reactions. The second strategy uses the macropolycarbanion as a macroinitiator for anionic polymerization. Different families of monomers were tested, vinylic type (4-VP, N-VP), acrylic type (DMAEM, MAPEG), acrylamide type (DMA, DMAPMA) and cyclic ones (a-amino acids). Grafted water-soluble copolymers exhibiting a PCL main chain were thus obtained. These new compounds are potentially partially degradable and form spontaneously nanometric micelle-like objects in water. Finally, we describe the use of an iodo-PCL derivative as a macro transfer agent which is an innovative use of the iodine transfer polymerization technique leading to new grafted copolymers.Il n'existe à l'heure actuelle pratiquement pas de copolymères greffés à fonctions cationiques et/ou amphotères présentant une dégradabilité intrinsèque. L'objectif de cette thèse est de générer des composés répondant à ces critères à partir d'une méthode de modification chimique par voie anionique de poly(e-caprolactone) (PCL). A cette fin, deux stratégies principales ont été suivies à partir d'un même intermédiaire réactionnel, un macropolycarbanion dérivé de PCL. La première est fondée sur l'emploi du macropolycabanion en tant qu'agent nucléophile qui réagit avec de petites molécules organiques électrophiles. Ces réactions de substitution ont permis l'obtention de copolymères à base PCL possédant entre 10 et 15% de motifs substitués par des groupes cationiques (ammonium, phosphonium), ou hydrosolubilisants (amine, acide carboxylique). Ces squelettes PCL fonctionnalisés peuvent être utilisés pour effectuer des post-modifications (réactions de couplages, dérivation de fonctions). La seconde stratégie utilise le macropolycarbanion en tant que macroamorceur de polymérisation anionique. Ce type de réaction a été appliqué à des dérivés vinyliques (4-VP, N-VP), des dérivés acryliques (DMAEM, MAPEG), des dérivés acrylamides (DMA, DMAPMA) et des dérivés cycliques (NCA d'acides a-aminés) ce qui a permis d'obtenir des copolymères greffés hydrosolubles à chaîne principale PCL. Ces composés ont des structures partiellement dégradables et forment en solution aqueuse des objets de dimensions nanométriques. Enfin, l'utilisation d'un dérivé polyiodé de PCL en tant que macro-polyagent de transfert est abordée ce qui constitue une nouvelle méthode de polymérisation radicalaire contrôlée par transfert dégénératif d'iode permettant l'obtention de structures greffées