Mechanical behaviour׳s evolution of a PLA-b-PEG-b-PLA triblock copolymer during hydrolytic degradation.

PLA-b-PEG-b-PLA is a biodegradable triblock copolymer that presents both the mechanical properties of PLA and the hydrophilicity of PEG. In this paper, physical and mechanical properties of PLA-b-PEG-b-PLA are studied during in vitro degradation. The degradation process leads to a mass loss, a decrease of number average molecular weight and an increase of dispersity index. Mechanical experiments are made in a specific experimental set-up designed to create an environment close to in vivo conditions. The viscoelastic behaviour of the material is studied during the degradation. Finally, the mechanical behaviour is modelled with a linear viscoelastic model. A degradation variable is defined and included in the model to describe the hydrolytic degradation. This variable is linked to physical parameters of the macromolecular polymer network. The model allows us to describe weak deformations but become less accurate for larger deformations. The abilities and limits of the model are discussed.

[Prevention and treatment of intra-uterine synechiae: Review of the literature]. / Prévention et traitement des synéchies endo-utérines : revue de la littérature.

Intra-uterine adhesions are a major cause of secondary infertility. The prevalence of adhesions is probably underestimated due to the heterogeneity of the symptoms. An exhaustive literature search using search engines MEDLINE, Pubmed, Cochrane library and Web of Science was performed to make a focus on the origins, consequences and methods of prevention of intra-uterine adhesions. Intra-uterine adhesions are likely to occur after any endo-uterine surgery via dysregulated activation of coagulation chain linked to the inflammatory process. Early and late obstetric complications are also recognized as caused by adhesions. The diagnosis is currently performed by hysteroscopy but it remains an invasive procedure even if it can be done with an ambulatory management. Several research approaches inspired by intra-abdominal surgery for the prevention of pelvic adhesions have been developed. However, no current method of prevention has proven its effectiveness in terms of improving spontaneous fertility. The improvement in surgical practices, the design of new intra-uterine medical devices and new research especially in the field of endometrial stem cells can maybe reduce the rate of adhesions end their complications after intra-uterine surgery.

Effect of various additives and polymers on lysozyme release from PLGA microspheres prepared by an s/o/w emulsion technique.

Incomplete protein release from PLGA-based microspheres due to protein interactions with the polymer is one of the main issues in the development of PLGA protein-loaded microspheres. In this study, a two-dimensional adsorption model was designed to rapidly assess the anti-adsorption effect of formulation components (additives, additives blended with the polymer or modified polymers). Lysozyme was chosen as a model protein because of its strong, non-specific adsorption on the PLGA surface. This study showed that PEGs, poloxamer 188 and BSA totally inhibited protein adsorption onto the PLGA37.5/25 layer. Similarly, it was emphasised that more hydrophilic polymers were less prone to protein adsorption. The correlation between this model and the in vitro release profile was made by microencapsulating lysozyme with a low loading in the presence of these excipients by a non-denaturing s/o/w encapsulation technique. The precipitation of lysozyme with the amphiphilic poloxamer 188 prior to encapsulation exhibited continuous release of active lysozyme over 3 weeks without any burst effect. To promote lysozyme release in the latter stage of release, a PLGA-PEG-PLGA tribloc copolymer was used; lysozyme was continuously released over 45 days in a biologically active form.

[Development of new skin substitutes based on bioresorbable polymer for treatment of severe skin defects]. / Développement de nouveaux substituts cutanés à base de polymères biorésorbables pour la prise en charge des affections cutanées sévères.

Over the last years, increasing attention has been paid to skin engineering due to its predominant function in body integrity. Thus, many laboratories are attempting to develop a dermal-epidermal complex. The aim of this study was to evaluate the potential of poly(alpha-hydroxyacid)s in the development of biocompatible and bioresorbable dermal scaffold combining human fibroblasts and keratinocytes, in order to obviate the drawbacks of using natural polymers such as collagen, hyaluronic acid and fibrin. We first confirmed the interest of poly(d,l-lactic acid) (PLA(50)) during the reconstitution of epidermis and next, we investigated the potential of poly(d,l-lactic acid)-poly(ethylene glycol)-poly(d,l-lactic acid) (PLA(50)-PEG-PLA(50)) for either skin cytocompatibility or scaffold processing. Data showed that PLA(50)-PEG-PLA(50) is compatible with the culture of human skin cells (fibroblasts and keratinocytes) and the development of a porous scaffold; two requirements compulsory for being considered as an adequate skin substitute. In fine, this material could represent the first generation of new skin dressings, i.e. a new concept taking advantage of both implantable devices and current dressings.