Tetracycline-Loaded Biomimetic Apatite: An Adsorption Study

Biomimetic apatites are appealing compounds for the elaboration of bioactive bone-repair scaffolds due to their intrinsic similarity to bone mineral. Bone surgeries are however often heavy procedures, and the infiltration of pathogens may not be totally avoided. To prevent their development, systemic antibiotic prophylaxis is widespread but does not specifically target surgical sites and involves doses not always optimized. A relevant alternative is a preliminary functionalization by an infection-fighting agent. In this work, we investigated from a physicochemical viewpoint the association of a wide-spectrum antibiotic, tetracycline (TC), and a biomimetic nanocrystalline apatite previously characterized. TC adsorption kinetics and isotherm were thoroughly explored. Kinetic data were fitted to various models(pseudo-first-order, pseudo-second-order, general kinetic model of order n, Elovich, double-exponential, and purely diffusive models). The best fit was found for a doubleexponential kinetic model or with a decimal reaction order of 1.4, highlighting a complex process with such TC molecules which do not expose high-affinity end groups for the surface of apatite. The adsorption isotherm was perfectly fitted to the Sips (Langmuir−Freundlich) model, while other models failed to describe it, and the Sips exponent greater than unity (1.08) suggested a joint impact of surface heterogeneity and positive cooperativity between adsorbed molecules. Finally, preliminary insights on TC release from pelletized nanocrystalline apatite, in aqueous medium and neutral pH, were obtained using a recirculation cell, indicating a release profile mainly following a Higuchi-like diffusion-limited rate. This work is intended to shed more light on the interaction between polar molecules not exhibiting high-affinity end groups and biomimetic apatites and is a starting point in view of the elaboration of biomimetic apatite-based bone scaffolds functionalized with polar organic drugs for a local delivery

Revêtements d'hydroxyapatite réalisés par projection plasma : vers de nouvelles fonctionnalités

Dans les stratégies de remplacement/reconstruction des os et des articulations, il est souvent fait appel à des matériaux revêtus. Le matériau de structure permet d'assurer une bonne tenue mécanique et le revêtement doit faciliter et pérenniser l'ancrage dans le site osseux. Dans ce contexte, la technique de projection plasma est largement utilisée pour réaliser industriellement des revêtements d'hydroxyapatite. Nous proposons ici de faire une revue sur les avancées en termes de procédé (projection plasma dc ou rf, de suspensions/solutions, basse énergie, …) couplé à des compositions d'hydroxyapatite modifiées

Synthesis and characterization of La2NiO4+δ coatings deposited by reactive magnetron sputtering using plasma emission monitoring

This work focuses on the structural and electrical characterization of La–Ni–O coatings deposited by reactive magnetron sputtering using Plasma Emission Monitoring (PEM) which allows high deposition rate. The optimal regulation setpoint for lanthanumdeposition is determined and then the current dissipated on the nickel target is adjusted to obtain the convenient La/Ni ratio to achieve the K2NiF4 structure. After an appropriate annealing treatment, all coatings exhibit crystalline structures that depend on the La/Ni ratio. Some cracks appear on samples deposited on alumina substrates depending to the argon flow rate and influence their electrical behavior

Optimizing Compliance and Thermal Conductivity of Plasma Sprayed Thermal Barrier Coatings via Controlled Powders and Processing Strategies

The properties and performance of plasma-sprayed thermal barrier coatings (TBCs) are strongly dependent on the microstructural defects, which are affected by starting powder morphology and processing conditions. Of particular interest is the use of hollow powders which not only allow for efficient melting of zirconia ceramics but also produce lower conductivity and more compliant coatings. Typical industrial hollow spray powders have an assortment of densities resulting in masking potential advantages of the hollow morphology. In this study, we have conducted process mapping strategies using a novel uniform shell thickness hollow powder to control the defect microstructure and properties. Correlations among coating properties, microstructure, and processing reveal feasibility to produce highly compliant and low conductivity TBC through a combination of optimized feedstock and processing conditions. The results are presented through the framework of process maps establishing correlations among process, microstructure, and properties and providing opportunities for optimization of TBCs

Synthesis of Half Fuel Cell Ni-YSZ / YSZ on Porous Metallic Support by Dry Surface Deposition Processes

A new cell design with metallic porous support was selected in order to face with the reduction of IT-SOFC's operation temperature. Nevertheless, the excessive roughness of the porous metallic interconnect induce additional problems when a thin electrolyte layer is required. In this work, an anode material (NiO-TSZ) by Atmospheric Plasma Spraying was deposited on metallic supports (ITM) produced by PLANSEE able to cover the roughness of the support. Then, a second thin and dense electrolyte layer (YSZ) by reactive magnetron sputtering was produced on the anode material. In this study, for both processing routes, the optimal process parameters regarding the structural, morphological and electrical characterizations were investigated

Dense yttria-stabilized zirconia obtained by direct selective laser sintering

This work demonstrated the possibility to manufacture dense yttria-stabilized zirconia (YSZ) parts by direct laser beam sintering using a commercial 3D SYSTEMS machine. To achieve this, several requirements of the process itself had to be met. First, an efficient laser-matter interaction had to be achieved. Indeed, a major issue to overcome was the intrinsic nonabsorbance property of the YSZ powder at the Nd:YAG laser wavelength. This issue was solved by adding a small amount of graphite to the YSZ powder that resulted in a simple mechanical blending of the two compounds. The graphite adjunction allowed an increase in the absorbance value from 2% to approximately 60%. The chemical composition of the powder blend and the density and the particle size distribution of the starting material used in this work enabled adequate heat transfers due to the appropriate thermophysical properties. Finally, a set of machine parameters that allows to manufacture parts with a high relative density, good geometrical accuracy, and mechanical strength was experimentally determined. Ultimately, it was found that the direct SLS allows the reproducible manufacture of simple YSZ parts with a relative density of 96.5

Compte rendu de l’atelier doctoral « L’Italie “à parts égales” : écrire l’histoire de l’Italie avant la conquête romaine » (Naples, Centre Jean Bérard, 1er‑5 juillet 2013)

Du 1er au 5 juillet 2013 s’est tenu à Naples, dans les locaux du centre Jean Bérard, l’atelier doctoral « L’Italie “à parts égales” : écrire l’histoire de l’Italie avant la conquête romaine ». Cet atelier, fruit d’une coopération entre l’École française de Rome et le centre Jean Bérard de Naples, s’inscrit dans le programme de recherche de l’École française de Rome, intitulé « Italia picta : territoires italiens et pratiques romaines (ve‑iiie siècles avant J.‑C.) ». Au sein de ce programme, r..

Ln 2 NiO 4+δ (Ln = La, Pr, Nd) coatings deposited by reactive magnetron sputtering as cathode material for intermediate temperature solid oxide fuel cell

This work focuses on the comparison of Ln-Ni-O coatings (Ln = La, Nd, Pr) deposited by reactive magnetron sputtering using Plasma Emission Monitoring (PEM) which allows high deposition rate. Each layer is deposited by different steps. The optimal regulation setpoint for oxide rare-earth deposition is determined and then the current dissipated on the nickel target is adjusted to obtain the convenient Ln/Ni ratio and to achieve the K2NiF4 structure. After an appropriate annealing treatment, all coatings exhibit crystalline structures, which depend on the Ln/Ni ratio. Due to the instability of Pr2NiO4 structure at intermediate temperatures, the crystallization step of praseodymium nickelate is performed at higher temperature than the other materials. This further thermal treatment implies a more porous structure. Each coating exhibits interesting properties. Electrical and electrochemical characterizations performed on these deposits prove better properties of the praseodymium nickelate coating

Effect of the deposition route on the microstructure of plasma-sprayed hydroxyapatite coatings

Plasma-spray (PS) is the most common technique used to cover orthopaedic titanium-based implant surfaces with hydroxyapatite (HA - Ca10(PO4)6OH2). The objective of the current work was to explore the influence of the precursor nature and characteristics (mainly powder size, Ca/P ratio, and density) on the morphology and the microstructure of HA coatings, deposited either by conventional atmospheric plasma spray (APS) or by rf-suspension plasma spray (rf-SPS). Two powders with different size distribution, density and shape were sprayed with same operating APS conditions. In parallel two water-based suspensions with distinct particle size and chemistry (Ca/P ratio) were implemented in rf-SPS. The morphology of both APS and rf-SPS coatings observed by SEM exhibits micro and sub-micro sized structures respectively, with similar porosity and thickness. The difference in precursor particle size does not affect the coating structure in rf-SPS, unlike in APS conditions. Superimposition of topography and phases maps performed from profilometry and Raman cartographies showed no direct correlation between the surface profile and composition. But such analysis highlighted the heterogeneity of the phases composing the coating surface, opening the possibility of a better understanding of biological behaviour