Elaboration de nouvelles compositions de bioverres destinés à la chirurgie réparatrice

Les bioverres sont des matériaux utilisés comme comblement osseux ayant la particularité de former une liaison intime avec le milieu hôte grâce au développement d une couche d hydroxyapatite carbonatée cristallisée (HAC) à leur surface. La bioactivité d un verre est définie par le temps de formation de cette couche dans le milieu physiologique. Le but de la thèse est de déterminer des formules mathématiques permettant de relier différentes propriétés essentielles de bioverres à leur composition. Celles-ci, appelées réponses, sont étudiées par plans de mélanges. Elles sont au nombre de sept : la température de fusion des mélanges de poudre, les températures de transition vitreuse et de cristallisation, la plage de travail des verres, la densité, la bioactivité et enfin l épaisseur de la couche d hydroxyapatite carbonatée. Ces caractéristiques jouent toutes un rôle important quant au choix d un bioverre pour une utilisation donnée. Par exemple, la température de fusion des mélanges renseigne sur sa facilité de synthèse, les températures caractéristiques indiquent les possibilités de mise en forme (verres massifs, poreux, granules ). L étude de la bioactivité et de l épaisseur de la couche d HAC permet de connaître la composition des verres les plus performants pour l utilisation en chirurgie réparatrice. Les plans de mélanges ont permis d étudier de manière systématique le système simple SiO2-CaO-Na2O, puis dopé par P2O5 et enfin par du fluor. Les formules obtenues mettent en évidence des lignes d isoréponses pour toutes les propriétés recherchées, ce qui renseigne sur l existence ou non d un verre de propriétés définies et dans le cas échéant indique sa ou ses compositionsBioglasses are materials used as bone filling and able to form a bond with the host environment by developing a hydroxyapatite layer (HCA) at their surface. The glass bioactivity is defined by its layer formation time in the body fluid. The aim of this work is to link some bioglass essential properties with their compositions by the mean of mathematical formulas. These properties are called responses, and are studied by mixtures designs. There are seven of them: powder mixtures melting temperature, glass transition and crystallization temperatures, the working range, the density, the bioactivity and the thickness of the hydroxyapatite layer. These whole characteristics have an important role for the choice of a bioglass. For example, melting temperature informs on the synthesis ease, characteristic temperatures indicate the preparation possibilities (glass bulk, porous, granules ). Bioactivity and HCA thickness study permits to point out the most efficient glasses for repairing surgery utilization. Mixtures designs have been applied on SiO2-CaO-Na2O system, P2O5 and CaF2-doped. Obtained formulas point out different response areas for all properties, which inform on the existence of a bioglass with defined properties and indicate its or their compositionsVALENCIENNES-BU Sciences Lettres (596062101) / SudocMAUBEUGE-BU (593922101) / SudocSudocFranceF

Etude de bioverres à base de SiO2, CaO, Na2O non dopés et dopés par le phosphore

The aim is to determine the most bioactive glasses of SiO2-CaO-Na2O ternary, and of this system doped with phosphorus.Soaking glasses in the simulated body fluid allowed to study the formation of crystalline hydroxycarbonate apatite (HCA). This layer allows a chemical anchoring implant-natural bone.The most bioactive glasses are Na2O-rich and SiO2-poor glasses. They forms an HCA layer within 12 hours. For this same glasses doped with phosphorus, adding phosphorus don't improve bioactivity. For less Na2O-rich invert glasses with phosphorus, corresponding to the less bioactive glasses of the ternary, the higher rate of P the faster HCA forms (6 hours with 6 mol % of P2O5). In conventional glasses, bioactivity stays middle (2-3 days).Some studies of cytotoxicity and cytocompatibility on the most Na-rich glass without and with phosphorus showed that these glasses form rapidly the HCA but make the environment too aggressive for the cells.MAUBEUGE-BU (593922101) / SudocVALENCIENNES-BU Sciences Lettres (596062101) / SudocSudocFranceF

Elaboration et analyses structurales de verres bioactifs macroporeux

Le travail porte sur l étude de verres bioactifs à base de SiO2, CaO, Na2O et P2O5 et se décompose en trois parties. Afin de relier la structure et la bioactivité, une étude structurale de ces verres a été réalisée par RMN du 29Si et du 31P. Cette étude a permis de montrer que l ajout progressif de phosphore engendre une polymérisation progressive du réseau silicate et modifie légèrement la nature chimique des entités phosphates. La deuxième partie concerne l élaboration d un verre bioactif macroporeux à porosité contrôlée en transposant le Procédé d élaboration de substituts osseux synthétiques d architecture poreuse parfaitement maîtrisée au verre 43,65SiO2-22,795CaO-30,555Na2O 3P2O5. Cependant, la densification par traitement thermique engendre la cristallisation partielle du verre. La RMN du 23Na a permis de confirmer la formation d une vitrocéramique. La troisième partie concerne l évaluation de la bioactivité in vitro ainsi que des essais préliminaires de cytocompatibilité du verre initial et de la vitrocéramique correspondante. Les analyses Infra Rouge réalisées sur les surfaces des échantillons plongés dans du fluide physiologique simulé (SBF) ont montré que la vitrocéramique est plus bioactive que le verre : l apatite s est formée après 5h15 d immersion pour la vitrocéramique contre 10h15 pour le verre. Les tests de cytocompatibilité ont mis en évidence une non cytotoxicité du verre et de la vitrocéramique. Cette étude a ainsi permis de corréler la structure des verres à leur bioactivité. À partir d un verre très bioactif, il a également été possible d élaborer une vitrocéramique macroporeuse à porosité contrôlée, avec de meilleurs résultats de bioactivité in vitro. Elaboration and Structural Analysis of macroporous bioactive glassesThe work concerns the study of bioactive SiO2, CaO, Na2O and P2O5 glasses and presents three parts. In order to connect the structure and the bioactivity, a structural study of these glasses was carried out by 29Si and 31P NMR. The study allowed to show that the progressive phosphorus addition generates an increasingly important polymerization of the silicate network and modifies slightly the phosphate entities chemical nature. The second part relates the macroporous bioactive glass elaboration with controlled porosity by transposing the Procédé d élaboration de substituts osseux synthétiques d architecture poreuse parfaitement maîtrisée to 43.65SiO2-22.795CaO-30.555Na2O-3P2O5 glass. However, the densification by heat treatment generates a partial crystallization of the glass. The 23Na NMR confirms the glass-ceramic formation. The third part relates to the in vitro bioactivity evaluation as well as preliminary cytocompatibility tests of for the initial glass and the corresponding glass-ceramic. The Infra Red analysis, made on the samples plunged in simulated body fluid (SBF), showed that the glass-ceramic is more bioactive than the glass: apatite was formed after 5h15 immersion for glass-ceramic against 10h15 for glass. The cytocompatibility tests put in evidence no cytotoxicity of the glass-ceramic. This study thus allowed to correlate the glasses structure to their bioactivity. From a very bioactive glass, it was also possible to elaborate a macroporous vitreous ceramic with controlled porosity and with better in vitro bioactivity resultsVALENCIENNES-BU Sciences Lettres (596062101) / SudocMAUBEUGE-BU (593922101) / SudocSudocFranceF

Bismuth lead oxyfluroride ionic glass conductors

PosterMany works were published on anion conductors by ions O2 -, with good conductivities at 500-600°C. Oxyfluorides, conductors by ions F-, have the same level of performances around 300°C. For example, the oxyfluoride system containing bismuth and lead led to a crystallized phase having a conductivity of 1 Sm-1 at 300°C. Doping by silica makes it possible to stabilize a vitreous domain and extends the range of the conducting phases. The presented study relates to the stability of the vitreous phase and the variation of conductivity as well according to the temperature as versus the composition. Thermal analyses by DTA evidenced, after the temperature of vitreous transition, the recrystallization of material in one or more stages. The phases crystallized were identified by high temperature X-rays diffraction. The best conductivity, about 0,3 Sm-1 at 227°C, is obtained for the fluorine richest material

Study of novel oxyfluoronitride bioglasses

International audienceBioglasses are used as bone substitutes and prosthetic coatings. Following implantation, they are predisposed to generate a series of physicochemical reactions at the glass-bone interface. Bioglasses with molar composition: 55SiO2–8.5CaO–31.5Na2O–5CaF2 have been synthesized and characterized. However, because of their poor strength, doping with nitrogen was performed on these glasses to increase their mechanical properties. The Young's elastic moduli, Vicker's microhardnesses, and the fracture toughnesses were measured and observed to increase linearly with nitrogen content in each of these systems. These results are consistent with the incorporation of nitrogen into the glass structure in three-fold coordination with silicon. Fluorine addition significantly decreases the thermal property values but the mechanical properties of these glasses remain unchanged with fluorine. The characterization of these N and F substituted bioglasses using 29Si MAS NMR have shown that the increase in rigidity of the glass network can be explained by the formation of SiO3N, SiO2N2 tetrahedra and Q4 units with extra bridging anions at the expense of Q3 units. The bioactivity of the glasses has been evaluated by soaking them in simulated body fluid (SBF) and showed that all oxyfluonitrides glasses are bioactives. Cytotoxicity tests based on different concentrations of bioglass powders in a cell growth environment have been also showed that they are not cytotoxi

Two novel phosphates Na2Mg2Fe(PO4)3 and Ag2Mg2Fe(PO4)3 with alluaudite structure: Synthesis, crystal structure and electrical properties

International audienc

Synthesis, crystal structure and magnetic behavior of a new calcium magnesium and iron orthophosphate Ca2MgFe2(PO4)4

International audienceThe structure of the new calcium magnesium iron orthophosphate, Ca2MgFe2(PO4)4 was determined from single crystal X-ray diffraction data. It crystallizes in the orthorhombic system, space group Pbca, with all atoms in general positions among which two sites are disordered. The crystal structure of this phosphate is build up from PO4 tetrahedra linked to FeO6 octahedra and to (Fe/Mg)O5 polyhedra via common vertices. In fact, each of the two mixed sites (Fe/Mg) is surrounded by five oxygen atoms which form either a pyramid with a square base or a bi-pyramid with a triangular base. The interconnection of these polyhedra leads to a three-dimensional structure delimiting cavities where Ca2+ cations are localized. The powder of this compound was successfully obtained by solid state reaction and its X-ray diffraction diagram was refined by pattern matching method. The magnetic measurements show multiple transition assigned to frustrated triangles locally present in AFM (antiferromagnetic) magnetic layered units