Nanocrystalline apatites: From powders to biomaterials

Non-stoichiometric nanocrystalline apatite powders are used to elaborate highly-bioactive biomaterials. Their exceptional surface reactivity arises from a structured but rather unstable hydrated layer involving ions in nonapatitic chemical environments, like in bone mineral. The initial powder characteristics can be tailored through precipitation parameters (pH, temperature, maturation time in solution). The drying of nanocrystalline apatite suspensions at very low temperature (4 °C) leads to ceramic-like materials exhibiting average mechanical properties (compressive strength 54 MPa) and a high porosity which could be exploited to entrap active organic compounds (e.g. growth factors). The consolidation at 150–200 °C of nanocrystalline apatite powders has also been studied using uni-axial pressing and spark plasma sintering (SPS). The results indicate only a limited alteration of the initial nanocrystals, and the bioceramics obtained show mechanical properties close to those reached with sintered stoichiometric HA. The high ion mobility in the hydrated layer of the nanocrystals can lead to “crystal fusion” processes. This capability to favor crystal–crystal interactions at low temperature, while preserving the non-stoichiometry and nanometer dimensions of apatite crystals, opens interesting perspectives for the elaboration of new resorbable and highly-bioactive bioceramics

Photopolymérisation et modulation d'indice de réfraction en holographie

5 pagesNational audienceLes systèmes ici mis en œuvre en tant que support d'enregistrement holographique reposent sur la mise en commun des compétences, d'une part, du LPIM dans le domaine des photoamorceurs et des supports d'enregistrement holographique, et celles, d'autre part, du laboratoire Foton. Les systèmes photoamorceurs considérés sont composés de trois éléments : un colorant et deux co-amorceurs (un donneur d'électron et un accepteur d'électron). Le système SFH+-NPG-ClHABI est, après optimisation des formulations, celui qui conduit aux meilleures performances holographiques, tant du point de vue rendement final de diffraction que de la vitesse de formation du réseau, tout en se stabilisant rapidement à son maximum

Luminescent biomimetic citrate-coated europium-doped carbonated apatite nanoparticles for use in bioimaging: physico-chemistry and cytocompatibility

Nanomedicine covers the application of nanotechnologies in medicine. Of particular interest is the setup of highly-cytocompatible nanoparticles for use as drug carriers and/or for medical imaging. In this context, luminescent nanoparticles are appealing nanodevices with great potential for imaging of tumor or other targetable cells, and several strategies are under investigation. Biomimetic apatite nanoparticles represent candidates of choice in nanomedicine due to their high intrinsic biocompatibility and to the highly accommodative properties of the apatite structure, allowing many ionic substitutions. In this work, the preparation of biomimetic (bone-like) citrate-coated carbonated apatite nanoparticles doped with europium ions is explored using the citrate-based thermal decomplexing approach. The technique allows the preparation of the single apatitic phase with nanosized dimensions only at Eu3+ doping concentrations ≤0.01 M at some timepoints. The presence of the citrate coating on the particle surface (as found in bone nanoapatites) and Eu3+ substituting Ca2+ is beneficial for the preparation of stable suspensions at physiological pH, as witnessed by the ζ-potential versus pH characterizations. The sensitized luminescence features of the solid particles, as a function of the Eu3+ doping concentrations and the maturation times, have been thoroughly investigated, while those of particles in suspensions have been investigated at different pHs, ionic strengths and temperatures. Their cytocompatibility is illustrated in vitro on two selected cell types, the GTL-16 human carcinoma cells and the m17.ASC murine mesenchymal stem cells. This contribution shows the potentiality of the thermal decomplexing method for the setup of luminescent biomimetic apatite nanoprobes with controlled features for use in bioimaging

Pratiques d'écriture et de réécriture à l'université. (résumé de Thèse de doctorat)

Bosc Françoise. Pratiques d'écriture et de réécriture à l'université. (résumé de Thèse de doctorat). In: Langage et société, n°86, 1998. pp. 177-178

Pratiques d'écriture et de réécriture à l'université. (résumé de Thèse de doctorat)

Bosc Françoise. Pratiques d'écriture et de réécriture à l'université. (résumé de Thèse de doctorat). In: Langage et société, n°86, 1998. pp. 177-178

ÉTUDE DE DEUX TECHNIQUES DE DIAGNOSTIC DE GESTATION CHEZ LA TRUIE

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Comparison of some techniques of pregnancy diagnosis in the sow

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Use of prostaglandins at the time of parturition in the sow. Results in field conditions

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