Strength and failure of fibrin fiber branch points

Blood clots form rapidly in the event of vascular injury, to prevent blood loss. They may also form in undesired places, causing heart attacks, strokes, and other diseases. Blood clots can rupture, and fragments of the clotmay lodge in distal blood vessels, causing, for example, ischemic strokes or embolisms. Thus, there has been great interest in understanding the mechanical behavior and failure mechanisms of blood clots and their constituents. To develop a mechanically realistic model of a blood clot, knowledge of the mechanical properties of its constituents is required. The major structural component providing mechanical strength to the clot is a mesh of fibrin fibers. Principally, three pieces of information are needed to develop realistic (fibrin fiber) network models: (i) the architecture of the network; (ii) the properties of the single fibers; and (iii) the properties of the fiber branchpoints

Fabrication of doped b-tricalcium phosphate bioceramics by robocasting for bone repair applications

International audienceb-tricalcium phosphate (b-TCP, b-Ca 3 (PO 4 ) 2 ) is one of the most attractive biomaterials for bone repair since it shows anexcellent biological compatibility, osteoconductivity, and resorbability. It is already commercialized under granules orpreforms for bone filling but there are still some issues for b-TCP porous scaffolds fabrication. Indeed, b-TCP cannotbe used as scaffolds in large bone defects or in load-bearing areas due to its weak mechanical properties related toinsufficient densification level. Indeed, the sintering temperature is limited because of the occurrence of a phasetransition b to a-TCP at 1150°C with a large lattice expansion causing microcracks and reducing shrinkage duringsintering. The thermal stability can be increased by the incorporation of dopants inside the b-TCP lattice. Indeed, suchdopants like cations can replace the calcium inside the structure and stabilize the b phase reaching higher densities.Moreover, dopants can also improve biological properties of b-TCP as bone implant like the osteoconductivity or theantibacterial behaviour.In this work, doped b-TCP powders are synthetized by coprecipitation of Ca(NO 3 ) 2 and (NH 4 ) 2 HPO 4 solutions in presenceof magnesium, strontium, silver and copper cations in order to prevent the phase transformation, increase the sinteringtemperature as well as the mechanical properties and bring an antibacterial behaviour. Rapid microwave sintering canthen be successfully applied with a limited grain growth and compared with conventional sintering. Cytotoxicity andantibacterial evaluation are conducted to assess the potential of the doped b-TCP.Finally, 3D-printable suspensions are prepared from optimized doped powder to manufacture porous scaffolds byrobocasting using water-based inks

Tribocorrosion of Polyethylene/Cobalt Contact Combined with Real-Time Fluorescence Assays on Living Macrophages: Development of A Multidisciplinary Biotribocorrosion Device

International audiencehe test conditions currently used in biotribocorrosion devices often differ greatly from the physiological conditions of joint replacements, contributing to discrepancies between the simulated and actual life span of joint replacements. In this study, a multidisciplinary biotribocorrosion device was developed based on the limitations of existing tribocorrosimeters. The set-up enables corrosion measurements to be simultaneously performed with real-time visualization of living cells using fluorescence microscopy under dynamic loads and movements. The device was configured to simulate the joint contact of ankle prostheses, and the wear of ultra-high-molecular-weight polyethylene/cobalt alloy (CoCrMo) implants surrounded by murine macrophages was tested. Various characterization techniques (non-contact optical profilometry, scanning and fluorescence electron microscopy and quantitative analyses of metal ions and pro-inflammatory cytokines) were combined in-depth multidisciplinary study. Two experimental conditions were used to promote the production of either polyethylene wear particles or metal ions. The first results indicated two distinct tribocorrosion mechanisms: 1) adhesive wear coupled with slow ionic depassivation of the cobalt alloy. The main degradation products were micrometric spherical polyethylene particles that seem to have little impact effect on the metabolic activity of the macrophages. 2) Ionic wear with the production of small, fibrillar polyethylene particles was observed. The production of metal ions, mainly chromium, was the predominant degradation process. The cytotoxicity of the chromium ions was evaluated based on the secretion of pro-inflammatory cytokines (prostaglandin E2). Our findings indicate that simulated conditions that result in low mechanical wear but high ions release appear to be more harmful to cells

Fabrication of Doped ß-tricalcium Phosphate Bioceramics by Robocasting for Bone Repair Applications

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Metallic glasses for biological applications and opportunities opened by laser surface texturing: A review

International audienc

Multiscale characterization of the wettability of thin film metallic glasses surfaces: Effect of a fs-laser treatment

International audienceWith the absence of crystalline defects and their amorphous structure, metallic glasses (MGs) exhibit very interesting mechanical and chemical properties. They have been studied since the 60s in their bulk state (BMGs), but are size limited and complex to synthesize due to their high needed number of elements. More recently, it was proved that PVD processes exhibit high cooling rate of the deposited atoms to allow the formation of metastable amorphous metallic phases [1]. Thus, metallic glasses are easier to obtain by PVD in thin film form than bulk ones. In addition, the thin film approach allows a great freedom in the films’ chemistry.From pure metallic targets, the magnetron sputtering process has already shown its ability to synthesize binary Zr-Cu thin film metallic glasses (TFMGs) over a wide range of chemical compositions (from 13 to 85 at.% of Cu [2]). These films exhibited a very low surface roughness together with the absence of grain boundaries, making them suitable for a femtosecond laser treatment [3], in order to still improve their properties. The laser irradiation process allows a one-step modification with a great repeatability, and gives rise to localized topographic and chemical modifications at the surface of the thin film.The work proposed here considers the formation of laser induced periodic surface structures (LIPSS) at the surface of two ternary magnetron sputtered TFMGs (ZrCuAg and ZrTiAg, with interesting biological properties [4-5]) using infrared ultrashort laser treatment. Several surface texturations are created by controlling the parameters of the laser (fluence, recovering of the pulses, etc…). These surfaces are first studied in terms of topographic (through scanning electron microscopy and atomic force microscopy) and chemical modifications, then a focus on the wettability modification of the textured surfaces (hydro-phily/phoby) is proposed. Wettability is studied first at the macroscale from the conventional measurement of the water contact angle of small water droplets. On the other hand, the condensation process of water onto the surface is also measured at the microscale by in situ measurements conducted in an environmental scanning electron microscope. Such a complementary small-scale method gives key information on the interaction of very small water droplets with the textured surface. Wetting behaviour is then discussed in light of the surface chemical nature and texture.[1] C.-Y. Chuand, et al., Surface and Coatings Technology, 215, 2013[2] M. Apreutesei, et al., Journal of Alloys and Compounds, 619, 2015[3] M. Prudent, et al., Nanomaterials, 11(5), 2021[4] A. Etiemble, et al., Journal of Alloys and Compounds, 707, 2019[5] A. Jabed, et al., Surface and Coatings Technology, 372, 201

Metallic glasses for biological applications and opportunities opened by laser surface texturing: A review

International audienc

Multiscale characterization of the wettability of fs-laser textured thin film metallic glasses surfaces

International audienceWith the absence of crystalline defects and their amorphous structure, metallic glasses (MGs) exhibit very interesting mechanical and chemical properties. They have been studied since the 60s in their bulk state (BMGs), but are size limited and complex to synthesize due to their high needed number of elements. More recently, PVD processes enabling high cooling rate of the deposited atoms have demonstrated the easier formation of metastable amorphous metallic phases, together with great freedom in the films’ chemistry.From pure metallic targets, the magnetron sputtering process has already shown its ability to synthesize binary Zr-Cu thin film metallic glasses (TFMGs) over a wide range of chemical compositions (from 13 to 85 at.% of Cu [1]), with low surface roughness together with the absence of grain boundaries, making them suitable for a femtosecond laser treatment [2], to further improve their properties.The work proposed here considers the formation of laser induced periodic surface structures (LIPSS) at the surface of two ternary magnetron sputtered TFMGs (ZrCuAg and ZrTiAg, with interesting biological properties [3]) using infrared ultrashort laser treatment. These textured surfaces are first studied in terms of topographic and chemical modifications, then a focus on the wettability modifications (hydro-phily/phoby) is proposed. Wettability is studied first at the macroscale from the conventional measurement of the water contact angle. On the other hand, the condensation process of water onto the surface is also measured at the microscale by in situ measurements conducted in an environmental scanning electron microscope (ESEM). Such a complementary small-scale method gives key information on the interaction of very small water droplets with the textured surface, opening the way to biological behavior of such surfaces.[1] M. Apreutesei, et al., “Zr-Cu thin film metallic glasses: An assessment of the thermal stability and phases transformation mechanisms”, Journal of Alloys and Compounds, 2015[2] M. Prudent, et al., “Initial morphology and feedback effects on laser-induced periodic nano-structuring of thin-film metallic glasses”, Nanomaterials, 2021[3] A. Etiemble, et al., “Innovative Zr-Cu-Ag thin film metallic glass deposited by magnetron PVD sputtering for antibacterial applications”, Journal of Alloys and Compounds, 201