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Prostate cancer (PCa) is the most frequent cancer in men aged 65 and over. PCa mainly metastasizes in the bone, forming osteosclerotic lesions, inducing pain, fractures, and nerve compression. Cancer cell-derived exosomes participate in the metastatic spread, ranging from oncogenic reprogramming to the formation of pre-metastatic niches. Moreover, exosomes were recently involved in the dialog between PCa cells and the bone metastasis microenvironment. Phospholipase D (PLD) isoforms PLD1/2 catalyze the hydrolysis of phosphatidylcholine to yield phosphatidic acid (PA), regulating tumor progression and metastasis. PLD is suspected to play a role in exosomes biogenesis. We aimed to determine whether PCa-derived exosomes, through PLD, interact with the bone microenvironment, especially osteoblasts, during the metastatic process. Here we demonstrate for the first time that PLD2 is present in exosomes of C4-2B and PC-3 cells. C4-2B-derived exosomes activate proliferation and differentiation of osteoblasts models, by stimulating ERK 1/2 phosphorylation, by increasing the tissue-nonspecific alkaline phosphatase activity and the expression of osteogenic differentiation markers. Contrariwise, when C4-2B exosomes are generated in the presence of halopemide, a PLD pan-inhibitor, they lose their ability to stimulate osteoblasts. Furthermore, the number of released exosomes diminishes significantly (-40%). When the PLD product PA is combined with halopemide, exosome secretion is fully restored. Taken together, our results indicate that PLD2 stimulates exosome secretion in PCa cell models as well as their ability to increase osteoblast activity. Thus, PLD2 could be considered as a potent player in the establishment of PCa bone metastasis acting through tumor cell derived-exosomes.

IF 4.208; International audience; Phthalic acid esters have been widely used to improve the plasticity of PVC medical devices. They carry a high exposure risk for both humans and the environment in clinical situations. Our study focuses on the cytotoxicity of alternative plasticizers. Postulated primary metabolites were synthesized, not being commercially available. Cytotoxicity assays were performed on L929 murine cells according to the ISO-EN 10993-5 standard design for the biocompatibility of medical devices. The tested concentrations of plasticizers (0.01, 0.05 and 0.1 mg/ml) covered the range likely to be found in biological fluids coming into direct contact with the medical devices. DEHP, DINP and DINCH were cytotoxic at the highest concentration (0.1 mg/ml) for 7 days of exposure. Their corresponding metabolites were found to be more cytotoxic, for the same concentration. By contrast, TOTM and its corresponding metabolite MOTM were not found to be cytotoxic. DEHA showed no cytotoxicity, but its corresponding monoester (MEHA) produced a cytotoxic effect at 0.05 mg/ml. In clinical situations, medical devices can release plasticizers, which can come into contact with patients. In vivo, the plasticizers are quickly transformed into primary metabolites. It is therefore important to measure the effects of both the plasticizers and their corresponding metabolites. Standard first-line cytotoxicity assays should be performed to ensure biocompatibility.

International audience

Standard histopathological examination is the gold standard for many disease diagnoses although the technique is limited with no full 3D volume analysis possible. Three dimensional X-ray Phase-Contrast Imaging(PCI) methods have been under constant and fast developments in the recent decades due to their superior performance for imaging low density objects and their ability to provide complementary information compared to attenuation based imaging. Despite the progresses, X-ray Phase Contrast Tomography still encounters remaining challenges to overcome on its way to become a routine non-invasive technique allowing the 3D assessment of tissue architecture in laboratory set-ups. Speckle Based Imaging (SBI) forms a new class of X-ray PCI techniques, sensitive to the first derivative of the phase. The set-up involved and the simplicity of implementation provide many advantages to SBI such as having no field of view and no resolution limitation in addition to have low requirements on the beam coherences. These advantages make SBI a good candidate for the transfer on conventional sources. In this work, we present preliminary results obtained on a conventional μCT and their comparison with data acquired at the European Synchrotron. We used a new phase retrieval algorithm based on optical energy conservation. We applied the method on both phantoms and biological samples in order to evaluate its quantitativeness for a transfer. A comparison to previously available speckle tracking algorithms is also performed. We demonstrate that the combination of the phase retrieval method with a standard μCT can achieve high resolution and high contrast within a few minutes, with a comparable image quality to the results obtained using synchrotron light.

ISI Document Delivery No.: HR1SX Times Cited: 1 Cited Reference Count: 61 Moure, Anne Bacou, Elodie Bosch, Steffi Jegou, Dominique Salama, Apolline Riochet, David Gauthier, Olivier Blancho, Gilles Soulillou, Jean-Paul Poncelet, Denis Olmos, Eric Bach, Jean-Marie Mosser, Mathilde Bosch, Steffi/A-1557-2009 Bosch, Steffi/0000-0002-0995-2775; Moure, Anne/0000-0002-1891-3698 Agence Nationale de la Recherche (ECTIS IHU program, France) [ANR-10-IBHU-005]; Pays de la Loire Region (Xenothera program, Nantes, France) [2011-1296]; University of Nantes (Interdisciplinary program, Nantes, France) [2017-2203] Agence Nationale de la Recherche (ECTIS IHU program, France), Grant/Award Number: ANR-10-IBHU-005; Pays de la Loire Region (Xenothera program, Nantes, France), Grant/Award Number: 2011-1296; University of Nantes (Interdisciplinary program, Nantes, France), Grant/Award Number: 2017-2203 1 4 15 Wiley Hoboken 1097-0290; International audience; The bioartificial pancreas encapsulating pancreatic islets in immunoprotective hydrogel is a promising therapy for Type 1 diabetes. As pancreatic islets are highly metabolically active and exquisitely sensitive to hypoxia, maintaining O-2 supply after transplantation remains a major challenge. In this study, we address the O-2 limitation by combining silicone-encapsulated CaO2 (silicone-CaO2) to generate O-2 with an extracellular hemoglobin O-2-carrier coencapsulated with islets. We showed that the hemoglobin improved by 37% the O-2-diffusivity through an alginate hydrogel and displayed antioxidant properties neutralizing deleterious reactive O-2 species produced by silicone-CaO2. While the hemoglobin alone failed to maintain alginate macroencapsulated neonate pig islets under hypoxia, silicone-CaO2 alone or combined to the hemoglobin restored islet viability and insulin secretion and prevented proinflammatory metabolism (PTGS2 expression). Interestingly, the combination took the advantages of the two individual strategies, improved neonate pig islet viability and insulin secretion in normoxia, and VEGF secretion and PDK1 normalization in hypoxia. Moreover, we confirmed the specific benefits of the combination compared to silicone-CaO2 alone on murine pseudo-islet viability in normoxia and hypoxia. For the first time, our results show the interest of combining an O-2 provider with hemoglobin as an effective strategy to overcome O-2 limitations in tissue engineering.

International audience

Objectives Minimally invasive procedures are used for the surgical treatment of lung cancer. Two techniques are proposed: video-assisted thoracic surgery or robotic-assisted thoracic surgery. Our goal was to study the economic impact of our long-standing program for minimally invasive procedures for major lung resection. Methods We conducted a single-centre, 1-year prospective cost study. Patients who underwent lobectomy or segmentectomy were included. Patient characteristics and perioperative outcomes were collected. Medical supply expenses based on the microcosting method and capital depreciation were estimated. Total cost was evaluated using a national French database. Results One hundred twelve patients were included, 57 with and 55 without robotic assistance. More segmentectomies were performed with robotic assistance. The median length of stay was 5 days for robotic-assisted and 6 days for video-assisted procedures (P = 0.13). The duration of median chest drains (4 days, P = 0.36) and of operating room time (255 min, P = 0.55) was not significantly different between the groups. The overall conversion rate to thoracotomy was 9%, significantly higher in the video-assisted group than in the robotic group (16% vs 2%, P = 0.008). No difference was observed in postoperative complications. The cost of most robotic-assisted procedures ranged from €10 000 to €12 000 (median €10 972) and that of most video-assisted procedures ranged from €8 000 to €10 000 (median €9 637) (P = 0.007); median medical supply expenses were €3 236 and €2 818, respectively (P = 0.004). The overall mean cost of minimally invasive techniques (€11 759) was significantly lower than the mean French cost of lung resection surgical procedures (€13 424) (P = 0.001). Conclusions The cost at our centre of performing minimally invasive surgical procedures appeared lower than the cost nationwide. Robotic-assisted thoracic surgery demonstrated acceptable additional costs for a long-standing program.

In this study, we propose a simple and effective strategy to prepare injectable macroporous calcium phosphate cements (CPCs) by syringe-foaming via hydrophilic viscous polymeric solution, such as using silanized-hydroxypropyl methylcellulose (Si-HPMC) as a foaming agent. The Si-HPMC foamed CPCs demonstrate excellent handling properties such as injectability and cohesion. After hardening the foamed CPCs possess hierarchical macropores and their mechanical properties (Young's modulus and compressive strength) are comparable to those of cancellous bone. Moreover, a preliminary in vivo study in the distal femoral sites of rabbits was conducted to evaluate the biofunctionality of this injectable macroporous CPC. The evidence of newly formed bone in the central zone of implantation site indicates the feasibility and effectiveness of this foaming strategy that will have to be optimized by further extensive animal experiments.A major challenge in the design of biomaterial-based injectable bone substitutes is the development of cohesive, macroporous and self-setting calcium phosphate cement (CPC) that enables rapid cell invasion with adequate initial mechanical properties without the use of complex processing and additives. Thus, we propose a simple and effective strategy to prepare injectable macroporous CPCs through syringe-foaming using a hydrophilic viscous polymeric solution (silanized-hydroxypropyl methylcellulose, Si-HPMC) as a foaming agent, that simultaneously meets all the aforementioned aims. Evidence from our in vivo studies shows the existence of newly formed bone within the implantation site, indicating the feasibility and effectiveness of this foaming strategy, which could be used in various CPC systems using other hydrophilic viscous polymeric solutions.

International audience; The aim of the present study was to assess the efficacy of a ready-to-use injectable bone substitute on the prevention of alveolar ridge resorption after tooth extraction. Maxillary and mandibular premolars were extracted from 3 Beagle dogs with preservation of alveolar bone. Thereafter, distal sockets were filled with an injectable bone substitute (IBS), obtained by combining a polymer solution and granules of a biphasic calcium phosphate (BCP) ceramic. As a control, the mesial sockets were left unfilled. After a 3 months healing period, specimens were removed and prepared for histomorphometric evaluation with image analysis. Histomorphometric study allowed to measure the mean and the maximal heights of alveolar crest modifications. Results always showed an alveolar bone resorption in unfilled sockets. Resorption in filled maxillary sites was significantly lower than in control sites. Interestingly, an alveolar ridge augmentation was measured in mandibular filled sockets including 30% of newly-formed bone. It was concluded that an injectable bone substitute composed of a polymeric carrier and calcium phosphate can significantly increase alveolar ridge preservation after tooth extraction.

The aim of the present work was to characterize the odontoblastic proliferation, differentiation, and matrix mineralization in culture of the recently established M2H4 rat cell line. Proliferation was assessed by cell counts, differentiation by RT-PCR analysis, and mineralization by alizarin red staining, atomic absorption spectrometry, and FTIR microspectroscopy. The results showed that M2H4 cell behavior closely mimics in vivo odontoblast differentiation, with, in particular, temporally regulated expression of DMP-1 and DSPP. Moreover, the mineral phase formed by M2H4 cells was similar to that in dentin from rat incisors. Finally, because in mice, transforming growth factor (TGF)-beta1 over-expression in vivo leads to an hypomineralization similar to that observed in dentinogenesis imperfecta type II, effects of TGF-beta1 on mineralization in M2H4 cell culture were studied. Treatment with TGF-beta1 dramatically reduced mineralization, whereas positive control treatment with bone morphogenetic protein-4 enhanced it, suggesting that M2H4 cell line is a promising tool to explore the mineralization mechanisms in physiopathologic conditions.

International audience; This study evaluated the in vivo behavior of an injectable calcium phosphate bone cement implanted in bone defects at the distal end of rabbit femora. After 3 weeks, samples were harvested and processed for undecalcified sectioning. Scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared microspectroscopy showed direct contact of bone and cement without soft tissue interposition, biocompatibility, and bioactivity with osteoconductive properties.

A new biomaterial is presented which consists of a cellulose derivative - silanised hydroxyethylcellulose (HEC-SIL) and biphasic calcium phosphate (BCP). Rheological properties of the polymer itself and its mixture with BCP are pH dependent. At pH = 10–12 HEC-SIL is liquid and undergoes quick gellation at pH < 9. Similarly the paste of HEC-SIL and BCP is fluid and injectable at higher pH and solidifies in biological solutions. The rate of this solidification can be easily controlled by the degree of substitution of hydroxyethylcellulose with silicoalkoxy groups.

We studied a new injectable biomaterial for bone and dental surgery consisting of a hydrophilic polymer as matrix and bioactive calcium phosphate (CaP) ceramics as fillers. This material is composed of complex fluids whose flow is determined by the laws of rheology. We investigated the macromolecular effects on this composite in a tube. The stability of the polymer and the mixture is essential to the production of a ready-to-use injectable biomaterial. These flow properties are necessary to obtain CaP bioactivity in a dental canal or bone defect during percutaneous surgery. Macromolecules provide spaces between CaP ceramic granules and facilitate the role of the biological agents of bone substitution.

The purpose of this study was to develop an injectable bone substitute (IBS) for percutaneous orthopedic surgery. The multiphasic material used was composed of a 2% aqueous solution of methylhydroxypropylcellulose (MHPC) and biphasic calcium phosphate (BCP, 60% hydroxyapatite and 40% beta-tricalcium phosphate) in which MHPC served as the carrier for 80-200 microm of BCP granules. The best BCP/polymer ratio was determined by the rheological properties and higher BCP content of the material. Steam sterilization was more effective than gamma irradiation in maintaining the stability of the mixture and conserving its physiochemical and mechanical properties. The in vitro biocompatibility of the composite was checked by direct-contact cytotoxicity and cell-proliferation assays. A preliminary in vivo test was performed in the rabbit using intraosseous implantations in the femoral epiphysis. Histological analysis was done after 1, 2, 4, and 10 weeks. Bone ingrowth into the IBS, in close association with BCP granules, was observed after 1 week and increased regularly from the surface inward at 2, 4, and 10 weeks. At the same time, smaller BCP granules (less than 80 microns in diameter) were degraded and resorbed. This injectable biomaterial proved suitable for cavity filling. The water solubility and viscosity of the polymer allow cells to recolonize, with in situ bonding of the mineral phase.

The aim of this work was to investigate in vitro the biological events leading to ectopic bone formation in contact with microporous biphasic calcium phosphate (BCP) ceramics. After implantation, microparticles may arise from their degradation and induce an inflammatory response involving macrophages. The secretion of pro-inflammatory cytokines may affect the differentiation of osteoblasts. Mouse macrophage-like (J774) and osteoblast-like (MC3T3-E1) cells were cultured in the presence of BCP microparticles of different sizes (

International audience; In this work, calcium-deficient apatites (CDA) were synthesized by ammonia hydrolysis reaction of dicalcium phosphate dihydrate (DCPD; CaHPO4 x 2 H2O) to obtain biphasic calcium phosphates (BCP) without any extraionic substitution. The influence of three parameters was studied: temperature of the reaction (70 and 100 degrees C), time of the reaction (4 and 18 h), and the pressure (open and closed system). Experiments were made according to a factorial design method (FDM) allowing optimization of the number of samples as well as statistical analysis of results. Moreover, the influence of temperature (until 200 degrees C) was investigated. The crystal size of CDA was determined according to the Scherrer's formula and from Rietveld refinements taking the CDA anisotropy into account. The last method seems to be a reliable method to determine crystallite sizes of CDA, since crystallite sizes of CDA along and directions were accessible. The results describe the hydroxyapatite % (HA%) in BCP by a first-order polynomial equation in the experimental area studied and the HA content was found to increase by raising time and temperature of the reaction. Moreover, the type of reaction system (open/closed vessel) appeared to have little influence on HA%.

International audience; In vertebrates, the actin-binding proteins tropomyosins are encoded by four distinct genes that are expressed in a complex pattern during development and muscle differentiation. In this study, we have characterized the transcriptional machinery of the alpha-tropomyosin (alpha-Tm) gene in muscle cells. Promoter analysis revealed that a 284-bp proximal promoter region of the Xenopus laevis alpha-Tm gene is sufficient for maximal activity in the three muscle cell types. The transcriptional activity of this promoter in the three muscle cell types depends on both distinct and common cis-regulatory sequences. We have identified a 30-bp conserved sequence unique to all vertebrate alpha-Tm genes that contains an MCAT site that is critical for expression of the gene in all muscle cell types. This site can bind transcription enhancer factor-1 (TEF-1) present in muscle cells both in vitro and in vivo. In serum-deprived differentiated smooth muscle cells, TEF-1 was redistributed to the nucleus, and this correlated with increased activity of the alpha-Tm promoter. Overexpression of TEF-1 mRNA in Xenopus embryonic cells led to activation of both the endogenous alpha-Tm gene and the exogenous 284-bp promoter. Finally, we show that, in transgenic embryos and juveniles, an intact MCAT sequence is required for correct temporal and spatial expression of the 284-bp gene promoter. This study represents the first analysis of the transcriptional regulation of the alpha-Tm gene in vivo and highlights a common TEF-1-dependent regulatory mechanism necessary for expression of the gene in the three muscle lineages.

International audience; Bone tissue engineering consists of culturing osteoblastic cells onto synthetic three-dimensional (3D) porous scaffolds. The organization of bone cells into 3D scaffolds is crucial for ex vivo tissue formation. Diffusional rates of nutrients could be greatly improved by perfusing media through the 3D microporous scaffolds. However, bone cells cultured in vitro are responsive to a variety of different mechanical signals including fluid flow and shear stresses. In this work, we attempt to study osteoblastic cells behaviour cultured within microdevices allowing continuous and homogenous feeding of cells. We have fabricated polydimethylsiloxane PDMS microdevices with a 3D microstructured channel network. Mouse calvarial osteoblastic cells MC3T3-E1 were seeded at 2x10(6)cells/ml and cultured into the microdevices under flow rates of 0, 5, 35 microl/min. Cells attached and proliferated well in the designed microdevices. Cell viability was found around 85% up to 1 to 2 weeks for shear stress value under 5 mPa. The alkaline phosphatase (ALP) activity was enhanced 3- and 7.5-fold inside the microdevices under static and dynamic flow of 5 microl/min as compared to flat static cultures in PDMS coated Petri dishes. Therefore, osteoblastic cells could be successfully cultured inside the microdevices under dynamic conditions and their ALP activity was enhanced. These results are promising for bone cell growth and differentiation as well as future tissue regeneration using larger 3D microfluidic microdevices.

International audience; A new injectable and self-crosslinkable bone substitute (IBS2) was developed for filling bone defects. The IBS2 consisted of a chemically modified polymer solution mixed with biphasic calcium phosphate (BCP) ceramic particles. The polymer hydroxypropylmethyl cellulose was functionalized with silanol groups (Si-HPMC) and formed a viscous solution (3 wt %) in alkaline medium. With a decrease in pH, self-hardening occurred due to the formation of intermolecular -Si-O- bonds. During setting, BCP particles, 40 to 80 microm in diameter, were added to the polymer solution at a weight ratio of 50/50. The resulting injectable material was bilaterally implanted into critically sized bone defects at the distal femoral epiphyses of nine New Zealand White rabbits. The IBS2 filled the bone defects entirely and remained in place. After 8 weeks, bone had grown centripetally and progressed towards the center of the defects. Newly formed bone, ceramic, and nonmineralized tissue ratios were 24.6% +/- 5.6%, 21.6% +/- 5.8%, and 53.7% +/- 0.1%, respectively. Mineralized and mature bone was observed between and in contact with the BCP particles. The bone/ceramic apposition was 73.4% +/- 10.6%. The yield strength for the IBS2-filled defects was 16.4 +/- 7.2 MPa, significantly higher than for the host trabecular bone tissue (2.7 +/- 0.4 MPa). This study showed that BCP particles supported the bone healing process by osteoconduction while the Si-HPMC hydrogel created intergranular space for bone ingrowth. This new injectable and self-crosslinkable bone substitute could be used conveniently in orthopedic surgery for filling critical-size bone defects.

International audience

International audience; BACKGROUND: The aim of the present study was to assess the efficacy of a ready-to-use injectable bone substitute for bone regeneration around dental implants placed into fresh extraction sockets. METHODS: Third and fourth mandibular premolars were extracted from three beagle dogs and the interradicular septa were surgically reduced to induce a mesial bone defect. Thereafter, titanium implants were immediately placed. On the left side of the jaw, mesial bone defects were filled with an injectable bone substitute (IBS), obtained by combining a polymer and biphasic calcium phosphate ceramic granules. The right defects were left unfilled as controls. After 3 months of healing, specimens were prepared for histological and histomorphometric evaluations. RESULTS: No post-surgical complications were observed during the healing period. In all experimental conditions, histological observations revealed a lamellar bone formation in contact with the implant. Histomorphometric analysis showed that IBS triggers a significant (P

International audience; Involvement of Pi and Ca in chondrocyte maturation was studied because their levels increase in cartilage growth plate. In vitro results showed that Pi increases type X collagen expression, and together with Ca, induces apoptosis-associated mineralization, which is similar to that analyzed in vivo, thus suggesting a role for both ions and apoptosis during endochondral ossification. INTRODUCTION: During endochondral ossification, regulation of chondrocyte maturation governs the growth of the cartilage plate. The role of inorganic phosphate (Pi), whose levels strongly increase in the hypertrophic zone of the growth plate both in intra- and extracellular compartments, on chondrocyte maturation and mineralization of the extracellular matrix has not yet been deciphered. MATERIALS AND METHODS: The murine chondrogenic cell line ATDC5 was used. Various Pi and calcium concentrations were obtained by adding NaH2PO4/Na2HPO4 and CaCl2, respectively. Mineralization was investigated by measuring calcium content in cell layer by atomic absorption spectroscopy and by analyzing crystals with transmission electron microscopy and Fourier transform infrared microspectroscopy. Cell differentiation was investigated at the mRNA level (reverse transcriptase-polymerase chain reaction [RT-PCR] analysis). Cell viability was assessed by methyl tetrazolium salt (MTS) assay and staining with cell tracker green (CTG) and ethidium homodimer-(EthD-1). Apoptosis was evidenced by DNA fragmentation and caspase activation observed in confocal microscopy, as well as Bcl-2/Bax mRNA ratio (RT-PCR analysis). RESULTS: We showed that Pi increases expression of the hypertrophic marker, type X collagen. When calcium concentration is slightly increased (like in cartilage growth plate), Pi also induces matrix mineralization that seems identical to that observed in murine growth plate cartilage and stimulates apoptosis of differentiated ATDC5 cells, with a decrease in Bcl-2/Bax mRNA ratio, DNA fragmentation, characteristic morphological features, and caspase-3 activation. In addition, the use of a competitive inhibitor of phosphate transport showed that these effects are likely dependent on Pi entry into cells through phosphate transporters. Finally, inhibition of apoptosis with ZVAD-fmk reduces pi-induced mineralization. CONCLUSIONS: These findings suggest that Pi regulates chondrocyte maturation and apoptosis-associated mineralization, highlighting a possible role for Pi in the control of skeletal development.

Interleukin-1 receptor antagonist (IL-1Ra) is a natural IL-1 inhibitor possessing anti-inflammatory properties. IL-1Ra is produced as different isoforms, one secreted (sIL-1Ra) and three intracellular (icIL-1Ra1, icIL-1Ra2 and icIL-1Ra3), derived from the same gene. We examined the production of IL-1Ra species by cultured human articular chondrocytes in response to various cytokines. The levels of IL-1Ra were undetectable in culture supernatants of untreated cells, but were significantly increased by IL-1β. Cell lysates contained very low levels of IL-1Ra, even in response to IL-1β, suggesting that chondrocytes produce predominantly sIL-1Ra. IL-6, which had no effect on its own, enhanced the effect of IL-1β, while dexamethasone prevented the response. We observed by RT-PCR that IL-1β and IL-6 induced primarily the production ofsIL-1RamRNA. Furthermore, IL-1β alone or combined with IL-6 increased the levels of nascent unsplicedsIL-1RamRNA, suggesting that sIL-1Ra expression is regulated at the transcriptional level. Reporter gene assays in immortalized chondrocytes, C-20/A4, consistently showed increasedsIL-1Rapromoter activity in response to IL-1β and IL-6. In conclusion, human articular chondrocytes produce sIL-1Ra in response to IL-1β and IL-6. The production of sIL-1Ra by chondrocytes may have a protective effect against articular inflammatory and catabolic responses.

International audience; Hydroxypropylmethylcellulose (HPMC) is used as a ligand for a bioactive calcium phosphate ceramic (the filler) in a ready-to-use injectable sterilized biomaterial for bone and dental surgery. Light scattering experiments were usually used to study high water-soluble polymers and to determine the basic macromolecular parameters. In order to gain a deeper understanding of polymer/mineral interactions in this type of material, we have investigated the effect of divalent and trivalent ions (Ca(2+), PO(4)(3-)) and steam sterilization on dilute solutions of HPMC and hydroxyethylcellulose (HEC). The sterilization process may cause some degradation of HEC taking into account its high molecular weight and some rigidity of the polymer chain. Moreover, in the case of HPMC, the changes in the conformations rather than degradation process are supposed. These effects of degradation and flocculation are strengthened in alkaline medium. Experimental data suggested the formation of chelate complexes between Ca(2+) and HPMC which improve its affinity to the mineral blend and consolidate the injectable biomaterial even in the case of its hydration by biological fluid.

International audience; The purpose of this study was to check the chemical stability of an injectable bone substitute (IBS) composed of a 50/50 w/w mixture of 2.92% hydroxypropyl methylcellulose (HPMC) solution in deionized water containing biphasic calcium phosphate (BCP) granules (60% hydroxyapatite/40% beta-tricalcium phosphate w/w). After separation of the organic and mineral phases, capillary gas chromatography (GC) was used to study the possible modification of HPMC due to the contact with BCP granules following steam sterilisation and 32 days storage at room temperature. HPMC was extracted from IBS in aqueous medium, and a dialytic method was then used to extract calcium phosphate salts from the HPMC. The percentage of HPMC extracted from BCP was 98.5%+/-0.5%, as measured by UV. GC showed no chemical modifications after steam sterilisation and storage.

International audience; Fourier transform infrared microspectroscopy (FTIRM) was used to investigate the organic and mineral phases of a calcified tissue (dentin) as a function of its location from predentin toward enamel, Thin dentin slices (decalcified or not) were fixed in formaldehyde and embedded in glycolmethylmethacrylate (GMA), Fixation did not denature collagen, and GMA did not interact with organic or mineral constituents of dentin, The nu (x)nu (3) PO4 domain was studied in particular in order to estimate mineral maturity and amide I, II, A, and B to obtain data on protein conformation. The results showed that dentin apatite became increasingly mature (stoichiometric) from the mineralization front toward the enamel, especially through loss of HPO42- groups and vacancies. Moreover, collagen fibrils became less and less hydrated, suggesting that intrafibrillar mineralization partially dehydrated the collagen. Combined study of the organic and mineral fractions of calcified tissues may help clarify their relationships in physiological and pathological tissues.

Hydroxypropylmethylcellulose (HPMC) of high-viscosity grade is used as a ligand for a bioactive calcium phosphate ceramic (the filler) in a ready-to-use injectable sterilized biomaterial for bone and dental surgery. Application of physico-chemical methods such as XPS, NMR, or Raman spectroscopy encounters difficulties when used to study such a multiphased material. This paper reports on the application of FT-IR microspectroscopy (FT-IRM) for the investigation of inorganic and organic phases of the rough composite and separated phases obtained by mechanical or chemical extraction methods. A comparison of FT-IRM with the conventional KBr pellet method was made and indicates that the macro and micro FT-IR methods are complementary: the former revealed new chemical groups not visualized with the KBr method whereas the latter detected the major compound of the blend. FT-IR microspectroscopy was revealed to be a powerful method of analysis that is complementary to other existing spectroscopic methods. Moreover, it is expected to be a useful tool in the study of biomaterials in biological samples.