Bi-layered silane-TiO2/collagen coating to control biodegradation and biointegration of Mg alloys

International audienceMagnesium alloys have shown high potential as biodegradable implants for bone repair applications. However, their fast degradation in physiological media demands tuning their corrosion rate to accompany the natural tissue healing processes. Here, a new bi-layered silane-TiO2/collagen coating efficient in stabilizing and biofunctionalizing the surface of AZ31 and ZE41 Mg alloys is presented. Corrosion tests performed in cell culture medium over 7 weeks showed that the bi-layered coating promotes the formation of a stable layer of Mg(OH)2/MgCO3/CaCO3 that provides effective protection to the alloys at advanced immersion stages. The intrinsic reactivity of each alloy plus formation of transitory calcium phosphate phases, resulted in distinct corrosion behavior in the short term. Cell experiments showed that the bi-layered coating improved osteoblasts and fibroblasts proliferation compared to bare and silane-TiO2-coated alloys. Different responses in terms of cell adhesion could be related to the intrinsic corrosion rate of each alloy and some toxicity from the alloying elements. The results evidenced the complex interplay between alloy nature, coating-alloy combination and cell type. The silane-TiO2/collagen coating showed to be a promising strategy to improve cell response and viability and to control degradation rate of Mg alloys in the long term

In situ three-dimensional monitoring of collagen fibrillogenesis using SHG microscopy.

International audienceWe implemented in situ time-lapse Second Harmonic Generation (SHG) microscopy to monitor the three-dimensional (3D) self-assembly of collagen in solution. As a proof of concept, we tuned the kinetics of fibril formation by varying the pH and measured the subsequent exponential increase of fibril volume density in SHG images. We obtained significantly different time constants at pH = 6.5 ± 0.3 and at pH = 7.5 ± 0.3. Moreover, we showed that we could focus on the growth of a single isolated collagen fibril because SHG microscopy is sensitive to well-organized fibrils with diameter below the optical resolution. This work illustrates the potential of SHG microscopy for the rational design and characterization of collagen-based biomaterials

Recent progress in the synthesis of imogolite and imogolite-like clay minerals. A focus on the sphree-tube transition

International audienceImogolite has been discovered more than 50 years ago in the weathering produc of volcanic soils in Japan. It has been quickly realjzed that imogoli lets a ubiquitous clay mineral which can be readly synthesized in the laborarory using ralber simple co-precipitation receipt

Organo-apatites for lead removal from aqueous solutions: A comparison between carboxylic acid and aminophosphonate surface modification

International audienceOrgano-apatites were prepared by in situ incorporation of adipic acid, citric acid and nitrilotris(methylene)triphosphonic acid. The resulting powders consist of poorly-crystalline nanosized apatites with organic content in the 2-8 wt% range. All materials exhibit faster sorption rate and higher sorption capacity for Pb2+ in acidic solutions compared to the pure apatite. This is especially true for carboxylate-modified powders that exhibit the highest-to-date maximum lead sorption capacity (approximate to gg(-1)). These properties can be correlated with the ability of introduced organic moieties to modify the acido-basic properties of the material surface and to form stable complexes with Pb2+

Fibrillogenesis from nanosurfaces: multiphoton imaging and stereological analysis of collagen 3D self-assembly dynamics

International audienceThe assembly of proteins into fibrillar structures is an important process that concerns different biological contexts, including molecular medicine and functional biomaterials. Engineering of hybrid biomaterials can advantageously provide synergetic interactions of the biopolymers with an inorganic component to ensure specific supramolecular organization and dynamics. To this aim, we designed hybrid systems associating collagen and surface-functionalized silica particles and we built a new strategy to investigate fibrillogenesis processes in such multicomponents systems, working at the crossroads of chemistry, physics and mathematics. The self-assembly process was investigated by bimodal multiphoton imaging coupling second harmonic generation (SHG) and 2 photon excited fluorescence (2PEF). The in-depth spatial characterization of the system was further achieved using the three-dimensional analysis of the SHG/2PEF data via mathematical morphology processing. Quantitation of collagen distribution around particles offers strong evidence that the chemically induced confinement of the protein on the silica nanosurfaces has a key influence on the spatial extension of fibrillogenesis. This new approach is unique in the information it can provide on 3D dynamic hybrid systems and may be extended to other associations of fibrillar molecules with optically responsive nano-objects