Activités biologiques d'un peptide et mise au point d'un système de libération prolongée par microcapsulation en vue de la foctionnalisation de biomatériaux

La @première partie de ce travail a consisté en l'étude des effets d'un activateur du TGF-beta. Ce peptide KRFK, issu de la TSP-1, semble conserver ses propriétés activatrices du TGF-beta latent dans le système ostéoblastique.La deuxième partie de ce travail a concerné l'élaboration et la validation d'un système de libération prolongée, puis son association avec un revêtement prothétique. Ce système de libération est constitué de microcapsules. Leur caractérisation approfondie a permis de démontrer leur parfaite biocompatibilité, ainsi que leur capacité à libérer de façon prolongée le peptide. De plus, l'association de ces microcapsules à un revêtement de CaP a pu être réalisée par l'intermédiaire d'un film d'alginate de calcium. Ainsi, nous avons pu obtenir un biomatériau implantable en site osseux, et dont la capacité à libérer de façon prolongée un peptide actif sur les cellules osteoblastiques pourrait permettre d'accélérer la régénération tissulaire. Ces données peuvent donc inaugurer un nouveau type de biomatériau basé sur une approche liant l'ingénierie tissulaire et la pharmacotechnie.@The first part of this work was to study the effects of an activator of the TGF-beta. This peptide named KRFK, conserved its activator properties of the TGF-beta in the osteoblast.The second part of this work was to prepare and characterise a sustained release system, and then associate it to a prosthetic coating. This sustained release is called microcapsules. Their characterization allowed us to demonstrate their perfect biocompatibility and to obtain a sustained release of the peptide. Moreover, we created an alginate film in order to associate the release system to a CaP coating.Thus, we obtain a new biomaterial for bone implantation which is able to release an active peptide. This will lead to improve the bone regeneration.REIMS-BU Santé (514542104) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Coating alginate microspheres with a serum albumin-alginate membrane: application to the encapsulation of a peptide.

Calcium alginate gel microspheres coated with a human serum albumin (HSA)-alginate membrane were prepared adapting a transacylation method previously applied to large beads. The procedure involved emulsification of an aqueous solution of sodium alginate and propylene glycol alginate (PGA) in an oily phase, followed by addition of CaCl(2). The resulting gel microspheres were transferred in an aqueous solution of HSA. The addition of 0.5 M NaOH started the reaction between PGA and HSA, producing amide bonds and forming a membrane around the particles. An optimization study was conducted, notably exploring the addition of HSA to the internal phase. The microcapsules were studied with respect to morphology (optical and scanning electron microscopy) and size (laser granulometry), in comparison with uncoated gel microspheres. Biocompatibility was checked in osteoblast cultures. Lysine-arginine-phenylalanine-lysine (KRFK) was encapsulated and the release kinetics was studied in vitro. The method provided stable microspheres (size around 60 microm), with a membrane surviving a treatment with citrate and resisting lyophilization. The microcapsules were shown biocompatible. The release of KRFK was slower (release time>8 days) than that of uncoated microspheres. These microcapsules might be useful as peptide containers to be combined with prosthetic materials for improving osteointegration

Preparation and characterization of an electrodeposited calcium phosphate coating associated with a calcium alginate matrix.

A new way of optimizing osteoconduction of biomaterials is to bring to them biological properties. In this work, we associated a novel release system with an electrodeposited calcium phosphate (CaP) coated titanium alloy Ti6Al4V. The characterization of this material was performed by means of light microscopy, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and X-ray energy dispersive spectroscopy (EDXS). The electrodeposited CaP coating was a tricalcium phosphate, and the release system was composed of microcapsules entrapped in an alginate film. We observed that the alginate matrix had a close contact with the coating. An intermediate layer containing calcium and phosphorus appeared at the interface between the alginate matrix and the CaP coating. These results allowed us to conclude that the association of two techniques, i.e. electrodeposition followed by deposition of a calcium alginate matrix, led to the elaboration of a new biomaterial