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Biphasic macroporous Hydroxyapatite/β-Tricalcium Phosphate (HA/β-TCP) scaffolds (BCPs) are widely used for bone repair. However, the high-temperature HA and β-TCP phases exhibit limited bioactivity (low solubility of HA, restricted surface area, low ion release). Strategies were developed to coat such BCPs with biomimetic apatite to enhance bioactivity. However, this can be associated with poor adhesion, and metastable solutions may prove difficult to handle at the industrial scale. Alternative strategies are thus desirable to generate a highly bioactive surface on commercial BCPs. In this work, we developed an innovative “coating from” approach for BCP surface remodeling via hydrothermal treatment under supercritical CO2, used as a reversible pH modifier and with industrial scalability. Based on a set of complementary tools including FEG-SEM, solid state NMR and ion exchange tests, we demonstrate the remodeling of macroporous BCP surface with the occurrence of dissolution–reprecipitation phenomena involving biomimetic CaP phases. The newly precipitated compounds are identified as bone-like nanocrystalline apatite and octacalcium phosphate (OCP), both known for their high bioactivity character, favoring bone healing. We also explored the effects of key process parameters, and showed the possibility to dope the remodeled BCPs with antibacterial Cu2+ ions to convey additional functionality to the scaffolds, which was confirmed by in vitro tests. This new process could enhance the bioactivity of commercial BCP scaffolds via a simple and biocompatible approach.

Biphasic macroporous Hydroxyapatite/β-Tricalcium Phosphate (HA/β-TCP) scaffolds (BCPs) are widely used for bone repair. However, the high-temperature HA and β-TCP phases exhibit limited bioactivity (low solubility of HA, restricted surface area, low ion release). Strategies were developed to coat such BCPs with biomimetic apatite to enhance bioactivity. However, this can be associated with poor adhesion, and metastable solutions may prove difficult to handle at the industrial scale. Alternative strategies are thus desirable to generate a highly bioactive surface on commercial BCPs. In this work, we developed an innovative “coating from” approach for BCP surface remodeling via hydrothermal treatment under supercritical CO2, used as a reversible pH modifier and with industrial scalability. Based on a set of complementary tools including FEG-SEM, solid state NMR and ion exchange tests, we demonstrate the remodeling of macroporous BCP surface with the occurrence of dissolution–reprecipitation phenomena involving biomimetic CaP phases. The newly precipitated compounds are identified as bone-like nanocrystalline apatite and octacalcium phosphate (OCP), both known for their high bioactivity character, favoring bone healing. We also explored the effects of key process parameters, and showed the possibility to dope the remodeled BCPs with antibacterial Cu2+ ions to convey additional functionality to the scaffolds, which was confirmed by in vitro tests. This new process could enhance the bioactivity of commercial BCP scaffolds via a simple and biocompatible approach.

Biphasic macroporous Hydroxyapatite/β-Tricalcium Phosphate (HA/β-TCP) scaffolds (BCPs) are widely used for bone repair. However, the high-temperature HA and β-TCP phases exhibit limited bioactivity (low solubility of HA, restricted surface area, low ion release). Strategies were developed to coat such BCPs with biomimetic apatite to enhance bioactivity. However, this can be associated with poor adhesion, and metastable solutions may prove difficult to handle at the industrial scale. Alternative strategies are thus desirable to generate a highly bioactive surface on commercial BCPs. In this work, we developed an innovative "coating from" approach for BCP surface remodeling via hydrothermal treatment under supercritical CO

Calcium carbonate (CaCO

International audience; While the formation of intracellular amorphous calcium carbonate (ACC) by living organisms is widespread, its detection in prokaryotes remains difficult owing to its susceptibility to transform or dissolve upon sample preparation. Because of these challenges, a large number of ACC-forming prokaryotes may have been undetected and their abundance in the natural environment is possibly underestimated. This study identifies diagnostic spectral markers of ACC-forming prokaryotes that facilitate their detection in the environment. Accordingly, ACC formed by cyanobacteria was characterized using Fourier transform infrared (FTIR) spectroscopy in near-IR, mid-IR, and far-IR spectral regions. Two characteristic FTIR vibrations of ACC, at ∼ 860 cm−1 and ∼ 306 cm−1, were identified as reliable spectral probes to rapidly detect prokaryotic ACC. Using these spectral probes, several Microcystis strains whose ACC-forming capability was unknown, were tested. Four out of eight Microcystis strains were identified as possessing ACC-forming capability and these findings were confirmed by scanning electron microscopy (SEM) observations. Overall, our findings provide a systematic characterization of prokaryotic ACC that facilitate rapid detection of ACC forming prokaryotes in the environment, a prerequisite to shed light on the role of ACC-forming prokaryotes in the geochemical cycle of Ca in the environment.

Simulated body fluids that mimic human blood plasma are widespread media for in-vitro studies in an extensive array of research fields, from biomineralization to surface and corrosion sciences. We show that these solutions undergo dynamic nanoscopic conformational rearrangements on the timescale of minutes to hours, even though they are commonly considered stable or metastable. In particular, we find and characterize nanoscale inhomogeneities made of calcium phosphate (CaP) aggregates that emerge from homogeneous SBF within a few hours and evolve into prenucleation species (PNS) that act as precursors in CaP crystallization processes. These ionic clusters consist of about 2 nm large spherical building units that can aggregate into supra-structures with sizes of over 200 nm. We show that the residence times of phosphate ions in the PNS depend critically on the total PNS surface. These findings are particularly relevant for understanding non-classical crystallization phenomena, in which PNS are assumed to act as building blocks for the final crystal structure.

International audience; Bone collagenous extracellular matrix provides a confined environment into which apatite crystals form. This biomineralization process is related to a cascade of events partly controlled by noncollagenous proteins. Although overlooked in bone models, concentration and physical environment influence their activities. Here, we show that collagen suprafibrillar confinement in bone comprising intra- and interfibrillar spaces drives the activity of biomimetic acidic calcium-binding polymers on apatite mineralization. The difference in mineralization between an entrapping dentin matrix protein-1 (DMP1) recombinant peptide (rpDMP1) and the synthetic polyaspartate validates the specificity of the 57-KD fragment of DMP1 in the regulation of mineralization, but strikingly without phosphorylation. We show that all the identified functions of rpDMP1 are dedicated to preclude pathological mineralization. Interestingly, transient apatite phases are only found using a high nonphysiological concentration of additives. The possibility to combine biomimetic concentration of both collagen and additives ensures specific chemical interactions and offers perspectives for understanding the role of bone components in mineralization.

International audience; Bone models set for studying apatite mineralization tend to use excess of organic additives and a very low concentration of collagen in the light of those described in the biological tissue. However, the activity of soluble additives during mineral deposition is highly dependent on their concentration and confinement state, among others. Here, we investigate the role of concentration of organic additives described as key components in bone mineralization, i.e. the bioinspired synthetic polyaspartate mimicking non-collagenous protein (NCP), citrate and collagen, on apatite formation. The precipitation setup tends to mimic the acidic mineralization front in bone and was monitored by in situ Raman and ex situ solid-state nuclear magnetic resonance (ssNMR). This model helps to identify specific effects of organic additives on mineral formation. In particular, we show that the sequence of apatite precursors often described in vitro, i.e. amorphous calcium phosphate (ACP) and subsequent octacalciumphosphate (OCP) formation, is noticeably modified by varying the concentration of the additives. NCP and citrate are identified as either inhibitor or activator in the formation of calcium phosphate (CaP). Besides, collagen acts either as additives or as organic scaffold below and above the liquid-crystal threshold, respectively. This result highlights that confinement drives thermodynamically apatite formation by slowing down the kinetic formation of precursors, even at alkaline pH.

A novel bio-hybrid drug delivery system was obtained involving a Mg/Al-NO3 layered double hydroxide (LDH) intercalated either with ibuprofenate anions (IBU) or a phospholipid bilayer (BL) containing a neutral drug, i.e., 17&beta, estradiol, and then embedded in chitosan beads. The combination of these components in a hierarchical structure led to synergistic effects investigated through characterization of the intermediates and the final bio-composites by XRD, TG, SEM, and TEM. That allowed determining the presence and yield of IBU and of BL in the interlayer space of LDH, and of the encapsulated LDH in the beads, as well as the morphology of the latter. Peculiar attention has been paid to the intercalation process of the BL for which all available data substantiate the hypothesis of a first interaction at the defect of the LDH, as well as on the interaction mode of these components. 1H, 31P and 27Al MAS-NMR studies allowed establishing that the intercalated BL is not homogeneous and likely formed patches. Release kinetics were performed for sodium ibuprofenate as well as for the association of 17&beta, estradiol within the negatively charged BL, each encapsulated in the LDH/chitosan hybrid materials. Such new bio-hybrids offer an interesting outlook into the pharmaceutical domain with the ability to be used as sustained release systems for a wide variety of anionic and, importantly, neutral drugs.

International audience; Materials science has been informed by nonclassical pathways to crystallization, based on biological processes, about the fabrication of damage-tolerant composite materials. Various biomineralizing taxa, such as stony corals, deposit metastable, magnesium-rich, amorphous calcium carbonate nanoparticles that further assemble and transform into higher-order mineral structures. Here, we examine a similar process in abiogenic conditions using synthetic, amorphous calcium magnesium carbonate nanoparticles. Applying a combination of high-resolution imaging and in situ solid-state nuclear magnetic resonance spectroscopy, we reveal the underlying mechanism of the solid-state phase transformation of these amorphous nanoparticles into crystals under aqueous conditions. These amorphous nanoparticles are covered by a hydration shell of bound water molecules. Fast chemical exchanges occur: the hydrogens present within the nanoparticles exchange with the hydrogens from the surface-bound H2O molecules which, in turn, exchange with the hydrogens of the free H2O molecule of the surrounding aqueous medium. This cascade of chemical exchanges is associated with an enhanced mobility of the ions/molecules that compose the nanoparticles which, in turn, allow for their rearrangement into crystalline domains via solid-state transformation. Concurrently, the starting amorphous nanoparticles aggregate and form ordered mineral structures through crystal growth by particle attachment. Sphere-like aggregates and spindle-shaped structures were, respectively, formed from relatively high or low weights per volume of the same starting amorphous nanoparticles. These results offer promising prospects for exerting control over such a nonclassical pathway to crystallization to design mineral structures that could not be achieved through classical ion-by-ion growth.

International audience; Since the observation in 2005 of a disordered mineral layer at the surface of aragonite platelets in abalone Haliotis laevigata nacre, the model of the organo–mineral interface in such biomineralized tissue has been challenged. As a direct interaction between the aragonite crystalline core and the organic matrix is no longer appropriate to describe such interface, a structural description of the disordered mineral domains at the atomic level is a key for a comprehensive view of nacre ultrastructure. Here, we use European abalone Haliotis tuberculata as a model to investigate aragonite nacre through high-resolution transmission electron microscopy (HR-TEM) and multinuclear solid state nuclear magnetic resonance (ssNMR). The presence of a disordered domain around aragonite crystals is shown through HR-TEM observations similarly to H. laevigata. The structure and the ionic composition of the disordered mineral environments of H. tuberculata nacre are investigated through 1H, 13C, 43Ca, and 23Na ssNMR. Interestingly, we demonstrate that the disordered mineral domains in nacre seem to be heterogeneous in terms of structure and chemical composition and do not match with amorphous calcium carbonate stricto sensu. At least three different carbonates species are evidenced, including CO32– and HCO3– present in the same mineral domain and closely associated with rigid H2O molecules. The local disorder around these ions is found to be inhomogeneous as some CO32– possess an aragonitic environment and are rather ordered (according to the position and line width of their 13C resonance) whereas, in opposition, the chemical environment around HCO3– is highly distributed. The analysis of potential cations as counterions revealed the presence of disordered Ca2+ and the presence of Na+ closely associated with HCO3–. On the basis of these structural data, we propose an atomic-level model for the disordered domains in abalone (H.tuberculata) nacre where the protonation level of carbonate ions, the proportion of sodium ions and the local disorder are increasing from the inner to the outer part of disordered domains. These results give an unprecedented structural view at the atomic scale of such disordered mineral domains in nacre aragonite tablets.

International audience; We report an experimental approach for highresolution real-time monitoring of transiently formed species occurring during the onset of precipitation of ionic solids from solution. This is made possible by real-time nuclear magnetic resonance (NMR) monitoring using dissolution dynamic nuclear polarization (D-DNP) to amplify signals of functional intermediates and is supported by turbidimetry, cryo-electron microscopy and solid-state NMR measurements. D-DNP can provide drastic signal improvements in NMR signal amplitudes, permitting dramatic reductions in acquisition times and thereby enabling to probe fast interaction kinetics such as those underlying the formation of pre-nucleation species (PNS) that precede solid-liquid phase separation. This experimental strategy allows, at unprecedented detail, for investigation of the formation of calcium phosphate (CaP)-based minerals by 31 P NMR-a process of substantial industrial, geological, and biological interest. So far, many aspects of the mechanisms of CaP nucleation remain unclear due to the absence of experimental methods capable of accessing such processes on sufficiently short time scales. The approach reported here aims to address this by an improved characterization of the initial steps of CaP precipitation, permitting the detection of PNS by NMR and determination of their formation rates, exchange dynamics and sizes. Using D-DNP monitoring, we find that under our conditions i) in the first 2 seconds after preparation of oversaturated calcium phosphate solutions, PNS with a hydrodynamic radius of Rh ≈ 1 nm are formed; and ii) following this rapid initial formation, the entire crystallization processes proceed on considerably longer timescales, requiring > 20 s to form the final crystal phase.

International audience; Calcium phosphates (CaPs) are one of the major mineral families of wide interest in biomineralization and biomaterial development. The identification and quantification of the different CaP phases (crystalline and amorphous) remains a major challenge in both in vitro and in vivo systems. This work aims to provide critical analysis of the different analytical techniques, Raman spectroscopy, solid-state NMR spectroscopy (ssNMR) and X-ray diffraction (XRD), which are used for the discrimination of octacalcium phosphate (OCP) from hydroxyapatite (HAp). Low amounts of OCP (∼10 wt%) can be detected by Raman spectroscopy in the presence of biomimetic carbonated apatite (cHAp), provided that the ν(HPO4) contribution with weak intensity from OCP at 1008 cm−1 is observable or that the spectral decomposition of the overlapped ν1(PO4) bands from OCP and cHAp is performed. However, Raman is not suitable for quantification purposes. In contrast, the quantification of OCP in proportions down to 10 wt% is easily performed with 31P solid state NMR. Opposite to solid state NMR, Raman can be implemented under in situ conditions to monitor the time dependence of the biomineralization process without any sampling perturbation. An approach combining the advantages of in situ micro-Raman spectroscopy and the sensitivity of ex situ solid state NMR was used to monitor the formation of biomimetic carbonated apatite from an acidic aqueous solution of phosphate, carbonate and calcium ions. In relation with the progressive increase of pH, we identify the transient phases, the precursors of cHAp: it is shown that an amorphous calcium phosphate phase (ACP) is first formed and subsequently transforms into OCP that then progressively turns into cHAp. Finally, powder X-ray diffraction coupled to Rietveld refinement was found to be very powerful in quantifying very small amounts of residual OCP in cHAp (down to 2 wt%). Upon the OCP transformation into cHAp, the decrease of the relative intensity of the (100) diffraction peak of the transient OCP phase was ascribed to an alteration of its hydrated layers, related to incorporation of water molecules and/or carbonate anions with reaction time. Such carbonate uptake in the course of transformation of OCP into cHAp could explain the origin of carbonate substitutions in the final biomimetic carbonated apatite.

International audience; Bone, tooth enamel, and dentin accumulate Sr 2+ , a natural trace element in the human body. Sr 2+ comes from dietary and environmental sources and is thought to play a key role in osteoporosis treatments. However, the underlying impacts of Sr 2+ on bone mineralization remain unclear and the use of synthetic apatites (which are structurally different from bone mineral) and non-physiological conditions have led to contradictory results. Here, we report on the formation of a new Sr 2+-rich and stable amorphous calcium phosphate phase, Sr(ACP). Relying on a bioinspired pathway, a series of Sr 2+ substituted hydroxya-patite (HA) that combines the major bone mineral features is depicted as model to investigate how this phase forms and Sr 2+ affects bone. In addition, by means of a comprehensive investigation the biominer-alization pathway of Sr 2+ bearing HA is described showing that not more than 10 at% of Sr 2+ , i.e. a physiological limit incorporated in bone, can be incorporated into HA without phase segregation. A combination of 31 P and 1 H solid state NMR, energy electron loss spectromicroscopy, transmission electron microscopy, electron diffraction, and Raman spectroscopy shows that Sr 2+ introduces disorder in the HA culminating with the unexpected Sr(ACP), which co-exists with the HA under physiological conditions. These results suggest that heterogeneous Sr 2+ distribution in bone is associated with regions of low structural organization. Going further, such observations give clues from the physicochemical standpoint to understand the defects in bone formation induced by high Sr 2+ doses. Statement of Significance Understanding the role played by Sr 2+ has a relevant impact in physiological biomineralization and provides insights for its use as osteoporosis treatments. Previous studies inspired by the bone remodelling pathway led to the formation of biomimetic HA in terms of composition, structures and properties in water. Herein, by investigating different atomic percentage of Sr 2+ related to Ca 2+ in the synthesis, we demonstrate that 10% of Sr 2+ is the critical loads into the biomimetic HA phase; similarly to bone. Unexpectedly, using higher amount leads to the formation of a stable Sr 2+-rich amorphous calcium phosphate phase that may high-dose related pathologies. Our results provide further understanding of the different ways Sr 2+ impacts bone.

Some compositional and structural features of mature bone mineral particles remain unclear. They have been described as calcium-deficient and hydroxyl-deficient carbonated hydroxyapatite particles in which a fraction of the PO43− lattice sites are occupied by HPO42− ions. The time has come to revise this description since it has now been proven that the surface of mature bone mineral particles is not in the form of hydroxyapatite but rather in the form of hydrated amorphous calcium phosphate. Using a combination of dedicated solid-state nuclear magnetic resonance techniques, the hydrogen-bearing species present in bone mineral and especially the HPO42− ions were closely scrutinized. We show that these HPO42− ions are concentrated at the surface of bone mineral particles in the so-called amorphous surface layer whose thickness was estimated here to be about 0.8 nm for a 4-nm thick particle. We also show that their molar proportion is much higher than previously estimated since they stand for about half of the overall amount of inorganic phosphate ions that compose bone mineral. As such, the mineral-mineral and mineral-biomolecule interfaces in bone tissue must be driven by metastable hydrated amorphous environments rich in HPO42− ions rather than by stable crystalline environments of hydroxyapatite structure.

In order to improve our knowledge on the vertebral development, structure and mineralization in Acipenseriformes, we undertook a study in a growth series of reared Siberian sturgeons (Acipenser baerii) using in toto clear and stain specimens, histological and ultrastructural observations, X-ray micro-tomography, and solid state NMR analyses. Scutes were also studied to compare the tissue structure and mineralization of endoskeletal and dermal skeletal elements. This study completes and clarifies previous investigations on vertebral development and architecture in sturgeons, and brings original data on the structure of (i) the perichondral bone that is progressively deposited around the vertebral elements during ontogeny, (ii) the typical cartilage composing these elements, and (iii) the scutes. In addition we provide data on the mineralization process, on the nature of the bone mineral phase, and on the growth dynamics of the vertebral elements.

The mechanism (s) that drive the organization of bone mineral throughout the bone extracellular matrix remain unclear. The long-standing theory implicates the organic matrix, namely specific non-collagenous proteins and/or collagen fibrils, while a recent theory proposes a self-assembly mechanism. Applying a combination of spectroscopic and microscopic techniques in wet and dry conditions to bone-like hydroxyapatite nanoparticles that were used as a proxy for bone mineral, we confirm that mature bone mineral particles have the capacity to self-assemble into organized structures. A large quantity of water is present at the surface of bone mineral due to the presence of a hydrophilic, amorphous surface layer that coats bone mineral nanoparticles. These water molecules must not only be strongly bound to the surface of bone mineral in the form of a rigid hydration shell, but they must also be trapped within the amorphous surface layer. Cohesive forces between these water molecules present at the mineral&ndash, mineral interface not only hold the mature bone mineral particles together, but also promote their oriented stacking. This intrinsic ability of mature bone mineral particles to organize themselves without recourse to the organic matrix forms the foundation for the development of the next generation of orthopedic biomaterials.

International audience; Biomineralization processes in living organisms result in the formation of skeletal elements with complex ultrastructures. Although the formation pathways in sea urchin larvae are known, the interrelation between calcite, amorphous calcium carbonate (ACC), and intra-crystalline organics in adult sea urchin biominerals is less clear. Here, we study this interplay in the spines and test 2 plates of the Paracentrotus lividus sea urchins whose skeletal elements have optimized function-properties relationships. Thermogravimetric analysis coupled with differential scanning calorimetry or mass spectrometry measurements, nuclear magnetic resonance technique and high-resolution powder X-ray diffraction show that pristine spines and test plates are composed of Mg-rich calcite and comprise about 10 wt. % of anhydrous ACC, 1.2 to 1.6 wt. % of organics, and less than 0.2 wt. % of water. Anhydrous ACC originates from incomplete crystallization of a precursor ACC phase during biomineralization and is associated with intra-crystalline organics at the molecular level. Molecular interactions at organic/inorganic interfaces cause significant calcite lattice distortions of the tensile type. The latter are amplified during ACC crystallization and finally disappear after heat-assisted destruction of organic molecules. Converting the measured lattice distortions (strains) into internal stress components, we follow stress evolution upon annealing and find that complete crystallization of ACC leads to the isotropy of residual stresses in all investigated skeletal parts. These results allow us to speculate that organic macromolecules are preferentially attached to different crystallographic planes in the pristine test and spine samples.

[EN] Boron chemistry has raised much interest because, despite the difference between necessities and toxicity being very narrow, it is still widely used in industrial processes. In a previous work we reported an adsorbent for boron extraction from water by the functionalisation of a UVM-7 mesoporous silica matrix with gluconamide moieties. The ability of this material to adsorb boron is based on its well-known affinity for coordinating the cis-diols present in attached saccharide. Although much research on the formation of boron esters with sugars and sugar derivatives in solution has been done, very few reports have dealt with the adsorption mechanism of boron onto functionalised materials in the solid state. Hence an in-depth study of the adsorption process was conducted in this paper. For this purpose, several solids with increasing boron contents were prepared from the gluconamide-functionalised UVM-7 material and an isothermal boron adsorption curve was obtained. The B-11 and C-13 MAS NMR techniques were used to characterise the obtained solids, and the simulation of the boron NMR and isothermal adsorption combined data was accomplished to enlighten the boron adsorption process. A model with three different coordination environments, two possible adsorption sites and the presence of oligomeric boron species allowed us to reproduce not only the isothermal boron adsorption curve, but also the evolution of the integrated areas for the signals in the B-11 MAS NMR spectra obtained for the different boron-containing gluconamide-functionalised UVM-7 materials., Financial support from the Spanish Government (Project MAT2009-14564-C04-01 and MAT2012-38429-C04-01) and the Generalitat Valenciana (Project PROMETEO/2009/016) is gratefully acknowledged. C.S. thanks the MICINN for a predoctoral fellowship.

International audience; The dynamical behavior of ibuprofen or benzoic acid (model molecule of ibuprofen) encapsulated in mesoporous silica is very specific as a very high mobility is evidenced at ambient temperature due to the existence of confinement effect. In this contribution, we demonstrate through variable temperature 1H MAS NMR experiments that this specific dynamical behavior is also related to a fast chemical exchange that takes place between protons of the COOH group of the organic molecule and protons from water molecules at the surface of the silica for materials obtained through incipient wetness impregnation. This phenomenon implies a weak interaction between the guest molecule and the silica surface that is related to the fast release profile of encapsulated ibuprofen observed in vitro.

International audience; In a study aiming to improve knowledge on the mineralization of the axial skeleton in reared Siberian sturgeon (Acipenser baerii Brandt, 1869), we discovered a new mineralized tissue within the notochord. To our knowledge, such a structure has never been reported in any vertebrate species with the exception of the pathological mineralization of the notochord remains in degenerative intervertebral disks of mammals. Here, we describe this enigmatic tissue using X-ray microtomography, histological analyses and solid state NMR-spectroscopy. We also performed a 1-year monitoring of the mineral content (MC) of the notochord in relation with seasonal variations of temperature. In all specimens studied from 2-year-old juveniles onwards, this mineralized structure was found within a particular region of the notochord called funiculus. This feature first appears in the abdominal region then extends posteriorly with ageing, while the notochord MC also increases. The mineral phase is mainly composed of amorphous calcium phosphate, a small amount of which changes into hydroxyapatite with ageing. The putative role of this structure is discussed as either a store of minerals available for the phosphocalcic metabolism, or a mechanical support in a species with a poorly mineralized axial skeleton. A pathological feature putatively related to rearing conditions is also discussed.

International audience; The presented research work is devoted to the investigation of the adsorption properties of biologically active molecules in mesoporous silicas. In particular, the interaction of ibuprofen with unique hydrated and functionalized silica carriers is unraveled by means of DFT-D calculations and experimental NMR experiments. The effects of temperature, degree of hydration, and adsorption site have been analyzed in detail to provide a molecular scale description of the adsorption and vectorization of a well-known drug, ibuprofen, on functionalized silicas. We conclude that the hydrated state, by the presence of a monolayer of water surface molecules on silica, plays the starring role.

International audience; The presence of an amorphous surface layer that coats a crystalline core has been evidenced for many biominerals, including bone mineral. In parallel, transient amorphous precursor phases have been proposed in various biomineralization processes, including bone biomineralization. Here we propose a methodology to investigate the origin of these amorphous environments taking the bone tissue as a key example. This study relies on the investigation of a bone tissue sample and its comparison with synthetic calcium phosphate samples, including a stoichiometric apatite, an amorphous calcium phosphate sample, and two different biomimetic apatites.To reveal if the amorphous environments in bone originate from an amorphous surface layer or a transient amorphous precursor phase, a combined solid-state nuclear magnetic resonance (NMR) experiment has been used. The latter consists of a double cross polarization 1H→31P→1H pulse sequence followed by a 1H magnetization exchange pulse sequence. The presence of an amorphous surface layer has been investigated through the study of the biomimetic apatites; while the presence of a transient amorphous precursor phase in the form of amorphous calcium phosphate particles has been mimicked with the help of a physical mixture of stoichiometric apatite and amorphous calcium phosphate. The NMR results show that the amorphous and the crystalline environments detected in our bone tissue sample belong to the same particle. The presence of an amorphous surface layer that coats the apatitic core of bone apatite particles has been unambiguously confirmed, and it is certain that this amorphous surface layer has strong implication on bone tissue biogenesis and regeneration.

In order to improve our knowledge on the vertebral development, structure and mineralization in Acipenseriformes, we undertook a study in a growth series of reared Siberian sturgeons (Acipenser baerii) using in toto clear and stain specimens, histological and ultrastructural observations, X-ray micro-tomography, and solid state NMR analyses. Scutes were also studied to compare the tissue structure and mineralization of endoskeletal and dermal skeletal elements. This study completes and clarifies previous investigations on vertebral development and architecture in sturgeons, and brings original data on the structure of (i) the perichondral bone that is progressively deposited around the vertebral elements during ontogeny, (ii) the typical cartilage composing these elements, and (iii) the scutes. In addition we provide data on the mineralization process, on the nature of the bone mineral phase, and on the growth dynamics of the vertebral elements. Anat Rec, 300:437-449, 2017. © 2016 Wiley Periodicals, Inc.

International audience; The transition from osteoblast to osteocyte is described to occur through passive entrapment mechanism (self-buried, or embedded by neighboring cells). Here, we provide evidence of a new pathway where osteoblasts are “more” active than generally assumed. We demonstrate that osteoblasts possess the ability to migrate and differentiate into early osteocytes inside dense collagen matrices. This step involves MMP-13 simultaneously with IBSP and DMP1 expression. We also show that osteoblast migration is enhanced by the presence of apatite bone mineral. To reach this conclusion, we used an in vitro hybrid model based on both the structural characteristics of the osteoid tissue (including its density, texture and three-dimensional order), and the use of bone-like apatite. This finding highlights the mutual dynamic influence of osteoblast cell and bone extra cellular matrix. Such interactivity extends the role of physicochemical effects in bone morphogenesis complementing the widely studied molecular signals. This result represents a conceptual advancement in the fundamental understanding of bone formation.

International audience; Phosphatidylcholine isotropic mesophases are easily formed by membrane fusion in hydroalcoholic solution in the presence of condensating silica. The transformation of lamellar bilayers into a sponge phase proceeds with the increase of the concentration of ethanol until a monodispersed mesoporous silica with surface area 800 m2 g-1 can be formed by calcination. Natural impurities of lecithin favour the formation of the sponge phase.

International audience; The involvement of collagen in bone biomineralization is commonly admitted, yet its role remains unclear. Here we show that type I collagen in vitro can initiate and orientate the growth of carbonated apatite mineral in the absence of any other vertebrate extracellular matrix molecules of calcifying tissues. We also show that the collagen matrix influences the structural characteristics on the atomic scale, and controls the size and the three-dimensional distribution of apatite at larger length scales. These results call into question recent consensus in the literature on the need for Ca-rich non-collagenous proteins for collagen mineralization to occur in vivo. Our model is based on a collagen/apatite self-assembly process that combines the ability to mimic the in vivo extracellular fluid with three major features inherent to living bone tissue, that is, high fibrillar density, monodispersed fibrils and long-range hierarchical organization.

Si/C/CMC composite for electrodes (Na-Carboxy-Methyl-Cellulose) appear today as the most promising strategy in view of substituting carbonaceous materials for silicon as negative active material in Li-ion batteries, hence the need to understand their reaction mechanism. By means of solid state Nuclear Magnetic Resonance spectroscopy, we confirmed that CMC chains can bind to Si via covalent or hydrogen bonding depending upon the pH of the mother suspension. Through coupled in situ Scanning Electron Microscopy and Electrochemical Impedance Spectroscopy observations of such electrodes reacting with Li, we demonstrated the ability of their porosity to buffer the Si swelling up to 1.7–2 Li/Si, further lithiation resulting in internal reorganization with either a definitive break of the covalent CMC-Si bond, or preservation of both the texture and electric wiring in the case of weaker Si-CMC hydrogen bonding thanks to a self-healing process. A relationship between the nature of the Si-CMC bonding and the electrode performance was found with a very positive impact of hydrogen interaction as 100 cycles could be achieved with preservation of the initial texture and excellent retention (3000 mAh/g Si after 100 cycles). Besides, we demonstrated that an alteration in the electrode texture/porosity, by a freeze-drying process, also impacts the electrode reversibility.

An old dream comes true: A direct and environmentally benign synthetic strategy was developed for the aerosol-based mass production of large-pore mesostructured aluminosilicate powders (see TEM image). Although amorphous, some powders exhibit higher activity towards m-xylene isomerization and lower coke formation than a Y-zeolite based industrial reference catalyst.

International audience; One- and two-dimensional refocused MAS-J-INEPT NMR experiments in the solid state (through-bond polarization transfer) involving the highly abundant 31P spin and the rare 29Si spin are described for the crystalline silicophosphate phase Si5O(PO4)6 and complex mixtures of SiP2O7 polymorphs. The evaluation of the 2JP-O-Si coupling constants for all 29Si sites is obtained by the careful analysis of the INEPT build-up curves under fast MAS. The results are in agreement with the crystallographic data, taking into account the various J coupling paths. The efficiency of the experiment is demonstrated by its application to more complex systems such as silicophosphate amorphous gels (obtained by the sol−gel process).

In two recent papers (J. Andersson, S. Areva, B. Spliethoff and M. Linden, Biomaterials, 2005, 26, 6827–6835 and J. Andersson, E. Johannessen, S. Areva, M. Jarn and M. Linden, J. Nanosci. Nanotechnol., 2006, 6, 2438–2444) we have presented new means of synthesizing silica–calcium phosphate (hydroxyapatite or tricalcium phosphate) composite materials, where the calcium phosphate is covered by a mesoporous layer of silica. These materials are bifunctional biomaterials, as they can be used both as drug carrier matrices and osteoconductive materials. Some of these materials, especially if synthesized according to a one-pot method, exhibit a very high in vitro bioactivity, and nucleate and grow calcium phosphate on their surfaces in less than 24 h if exposed to a simulated body fluid. In the present study, we have carried out a thorough characterization of the one-pot sol–gel derived composite materials by the means of solid state 29Si magic angle spinning (MAS) NMR, 31P MAS NMR, 23Na MAS NMR, and transfer of population in double resonance (TRAPDOR) NMR spectroscopy, scanning electron microscopy, and transmission electron microscopy. The aim of the study is to relate the material properties to the in vitro bioactivity. The reason for high bioactivity of the composites cannot be ascribed to the silica content, but primarily to the presence of a highly soluble second calcium phosphate phase, NaCaPO4, co-existing with the hydroxyapatite in the hybrid material. Furthermore, the hydroxyapatite becomes increasingly calcium deficient with increasing silica content, which adds to increase the bioactivity. Also the overall crystallinity of the apatitic calcium phosphate phase could contribute to the bioactivity of the composites in vitro.

Solid-state 29 Si, 31 P MAS and CP MAS NMR and X-ray powder diffraction have been used to study phosphosilicate gels of molar composition (TEOS/H 3 PO 4 = 1) treated under various temperature conditions. It was found that the gel treated at 100 °C for 30 h had a structure consisting of a silica matrix including isolated molecules of phosphorous acid. In contrast, cross condensation (leading to the formation of Si–O–P bonds) was observed when the gel was treated at 136 °C for 6 days. Evidence for the formation of Si–O–P bonds was provided first by XRD, which showed the formation of the crystalline phosphosilicate phases Si 5 O(PO 4 ) 6 and Si(HPO 4 ) 2 ·H 2 O, and then by the use of two-dimensional (2D) NMR techniques: 31 P– 29 Si heteronuclear correlation (HETCOR) experiments, based on cross polarization transfer. Very few data concerning this type of experiments are available in the literature: therefore, CP dynamics was carefully studied under MAS. To cite this article: C. Coelho et al., C. R. Chimie 9 (2006) .

The results of two techniques of dipolar recoupling, REDOR and CPMAS, are compared in the case of a coupled multiple-spin system. A fundamentally different behavior is observed for these two techniques. In REDOR, the terms associated with each interaction S – I k commute with each other and no truncation takes place so that each addition of spin I k causes a splitting with its dipolar frequency. In CPMAS, the flip-flop terms of the dipolar Hamiltonian do not commute with the dominant term from the strongly coupled spin pair so that the weak coupling terms from the neighboring spin I k are effectively truncated by the dominant pair interaction. Spin dynamics calculations are in agreement with the experimental data in a cubane shaped cluster.

A geometrical approach of the quadrupolar interaction is presented. First- and second-order effects on all transitions are represented by quadrics and quartics. This approach allows a simple and exhaustive description of the Solomon multiple echoes: the location of the echoes in the time domain, as well as their nature , is determined without calculation. Experimental evidence of multiple echoes in the case of a 27 Al–O–P cluster is presented. The selection of 2Q coherences by appropriate phase cycling is presented as well. DAS and MQ MAS experiments are also described in this particular frame. To cite this article: C. Bonhomme et al., C. R. Chimie 7 (2004).

The first Al−O−P analogue of the so-called 4=1 Secondary Building Unit (SBU) of zeolites is presented and characterized by single-crystal X ray diffraction (compound 1). The 4=1 building unit structure is very rarely encountered in zeolites and microporous materials. Compound 1 was carefully studied by 31P and 27Al solid-state MAS NMR, resulting in the precise spectroscopic description of the phosphorus and aluminium sites. Unusual 27Al quadrupolar parameters were measured. Moreover, we also present a high-resolution solid-state 1H NMR study of 1 at 600 MHz and 33 kHz MAS; a remarkable improvement in resolution is observed, allowing definite assignments. The new opportunities offered by very high speed 1H NMR at high field were further demonstrated with the study of a cubane-shaped Al−O−P cluster (compound 2) and of phenylphosphonic acid. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

A detailed solid state NMR study of molecular aluminophosphates is presented. The crystallographic structures of [Al4(HPO4)4(C2H5OH)12]Cl4·4C2H5OH (compound 1) and [Al4(HPO4)4(C2H5OH)12]Br4·4C2H5OH (compound 2) were obtained at low temperature. 13C CP MAS NMR dynamics were carefully studied: non-exponential growth of magnetisation was observed for 13C CP even for moderately coupled 13CH3 groups. This approach was extended for the first time to 31P CP MAS NMR. Variable contact time as well as inversion recovery cross polarisation (IRCP) experiments showed unambiguously that the 1H → 31P magnetisation transfer was also not exponential. The 31P IRCP MAS experiment proved to be a powerful tool for the study of complex amorphous materials, allowing editing of the spectra. Variable contact time experiments under fast MAS led to the observation of strong dipolar oscillations. The subsequent analysis of the CP data in the frequency domain led to the direct accurate determination of 31P–1H distances. This approach can be used as an alternative method for the measurement of distances in solid state NMR. 27Al NMR quadrupolar parameters for 1 and 2 were derived by using several static and MAS techniques, in both time and frequency domains. The time domain response to a two-pulse sequence led to the very unusual observation of multiple quadrupolar Solomon echoes. The spectroscopic data related to 1 and 2 are a good starting point and pertinent tools for the study of more complex derivatives.

We present a new Al-O-P cyclic aluminophosphinate characterized by single X-ray diffraction (XRD) and multinuclear solid state NMR.

First principles calculations of 31P NMR parameters allow full characterization of biocompatible Ca(PO3)2 phases. A “bridge” is established between NMR experimental data and calcium phosphate structures through the FPC-NMR approach (first principles calculations-NMR). We believe that this approach can be extended to a large panel of structures in the frame of biocompatible materials.

International audience; It is well known that organic molecules from the vertebrate extracellular matrix of calcifying tissues are essential in structuring the apatite mineral. Here, we show that water also plays a structuring role. By using solid-state nuclear magnetic resonance, wide-angle X-ray scattering and cryogenic transmission electron microscopy to characterize the structure and organization of crystalline and biomimetic apatite nanoparticles as well as intact bone samples, we demonstrate that water orients apatite crystals through an amorphous calcium phosphate-like layer that coats the crystalline core of bone apatite. This disordered layer is reminiscent of those found around the crystalline core of calcified biominerals in various natural composite materials in vivo. This work provides an extended local model of bone biomineralization.

International audience; Clay materials have been an ever-present accoutrement of modern civilization; improvements to process these materials have quickened their utilization for use in complex multiaxial load-bearing structures. Specifically, with better methods to organize the constituent metal oxide components in clay, the distribution of characteristic nematic and smectic phases can be controlled. In this work, we utilize the interactions of an amorphous calcium carbonate phase with kaolinite to form a complex composite that can be organized into distinct hierarchical structures. We demonstrate that these ACC–kaolinite composites can maintain characteristic long-range-ordered layer-by-layer structures across many length scales, from nano- to millimeter, through convenient and economical processing at room temperature.

International audience; A facile method for preparing highly conductive hybrid organic-inorganic membranes is reported. These membranes are synthesized using an electrospinning process with a sol-gel-based solution containing PVDF-HFP (polyvinylidenefluoride-hexafluoropropylene), functionalized or not functionalized silicon alkoxides, and additives. Proton conduction measurements highlight that these hybrid membranes exhibit conductivity value of 101 mS/cm at 120 degrees C under 80% RH (relative humidity), comparable to the best Nafion measured under the same conditions. These membranes have a proton conductivity-humidity variation close to Nafion and a modulus value higher than that for Nafion above 80 degrees C. Their proton conductivity value is about 15 mS/cm under 50% RH, and it constitutes one of the highest values reported. These interesting properties are related to the microstructure of the electrospun membranes that have been characterized using field emission scanning electron microscopy (FE-SEM) and small angle neutron scattering (SANS). The electrospun membranes are made composed of a bundle of fibers surrounded by a functionalized silica network. The bundle of fibers corresponds to the assembly of small polymer fibers surrounded by small anisotropic functionalized silica domains. Coupling the reactive chemistry of the sol-gel-based process with electrospinning allows the design of hybrid membranes with fractal hydrophobic/hydrophilic interfaces exhibiting different length scales.