Sophie Quillard

Rapid prototyped porous titanium coated with calcium phosphate as a scaffold for bone tissue engineering.

High strength porous scaffolds and mesenchymal stem cells are required for bone tissue engineering applications. Porous titanium scaffolds (TiS) with a regular array of interconnected pores of 1000 microm in diameter and a porosity of 50% were produced using a rapid prototyping technique. A calcium phosphate (CaP) coating was applied to these titanium (Ti) scaffolds with an electrodeposition method. Raman spectroscopy and energy dispersive X-ray analysis showed that the coating consisted of carbonated hydroxyapatite. Cross-sectioned observations by scanning electron microscopy indicated that the coating evenly covered the entire structure with a thickness of approximately 25 microm. The bonding strength of the coating to the substrate was evaluated to be around 25 MPa. Rat bone marrow cells (RBMC) were seeded and cultured on the Ti scaffolds with or without coating. The Alamar Blue assay provided a low initial cell attachment (40%) and cell numbers were similar on both the uncoated and coated Ti scaffolds after 3 days. The Ti scaffolds were subsequently implanted subcutaneously for 4 weeks in syngenic rats. Histology revealed the presence of a mineralized collagen tissue in contact with the implants, but no bone formation. This study demonstrated that porous Ti scaffolds with high strength and defined geometry may be evenly coated with CaP layers and cultured mesenchymal stem cells for bone tissue engineering.

Enhanced Expression of the Inorganic Phosphate Transporter Pit-1 Is Involved in BMP-2–Induced Matrix Mineralization in Osteoblast-Like Cells†

Pi handling by osteogenic cells is important for bone mineralization. The role of Pi transport in BMP‐2–induced matrix calcification was studied. BMP‐2 enhances Pit‐1 Pi transporters in osteogenic cells. Experimental analysis suggest that this response is required for bone matrix calcification.

Structural and spectroscopic characterization of a series of potassium- and/or sodium-substituted β-tricalcium phosphate

In this paper, we report X-ray diffraction investigations as well as Raman and solid-state (31)P and (23)Na magic angle spinning nuclear magnetic resonance (NMR) characterization of three series of calcium orthophosphates. The general formulae of the studied compounds are Ca(10.5-x/2)M(x)(PO(4))(7), where M=K or Na and x=0, 0.25, 0.50, 0.75, 1.0; and Ca(10)K(x)Na(1-x)(PO(4))(7), where x=0, 0.25, 0.5, 0.75, 1.0. These calcium orthophosphates are found to be isostructural with β-tricalcium phosphate (β-TCP, Ca(3)(PO(4))(2)) with the substitution of some calcium sites by potassium and/or sodium cations. The unit cell parameters vary continuously with the level of substitution, a characteristic of these solid solutions. The Raman spectra show the different vibrational bands of the phosphate groups PO(4), while the NMR chemical shifts are sensitive to the non-equivalent phosphorus and sodium ions present in these substituted samples. As both Raman and NMR spectroscopies are local probes, they offer tools to distinguish between these different phosphorus and phosphate groups, according to their structural site and local environment, especially the type of cation substituent. A convenient decomposition of the Raman and NMR spectra into Gaussian-Lorentzian components leads us to propose an assignment of the main observed bands of these substituted β-TCPs.

The in vivo degradation of a ruthenium labelled polysaccharide-based hydrogel for bone tissue engineering.

In this paper we report a new method that permitted for the first time to selectively track a polysaccharide-based hydrogel on bone tissue explants, several weeks after its implantation. The hydrogel, which was developed for bone healing and tissue engineering, was labelled with a ruthenium complex and implanted into rabbit bone defects in order to investigate its in vivo degradation. 1, 2, 3 and 8 weeks after surgery, the bone explants were analyzed by synchrotron X-ray microfluorescence, infrared mapping spectroscopy, scanning electron microscopy, and optical microscopy after histological coloration. The results showed that the labelled polysaccharide-based hydrogel was likely to undergo phagocytosis that seemed to occur from the edge to the center of the implantation site up to at least the 8th week.

Vibrational analysis of the reduced form of polyaniline: the leucoemeraldine base

Abstract Extensive studies have been carried out on the different forms of polyaniline. In this paper, we present a study of the vibrational properties of the leucoemeraldine base, the reduced form of polyaniline. Infrared absorption and resonant Raman scattering (RRS) spectra are presented for the polymer, together with those obtained in model compounds such as diphenylamine and N , N ′-diphenyl-1,4-phenylenediamine. The Raman spectrum of the leucoemeraldine base exhibits mainly bands at 1181, 1219, 1597 and 1618 cm −1 . By the use of a valence-force-field model, we have assigned these vibrational modes, including those of the model compounds. Calculations are in rather good agreement with previous assignments and the main force constants, which are determined from the fit of the experimental IR and Raman bands, are physically reasonable compared to what is found in other polymers.

Electronic and vibrational changes induced by different acidic vapors in polyaniline

Abstract We present a comparative study of conductive salt of polyaniline, i. e., polyemeraldine doped with HCl vapor or with HCSA upon m-cresol vapor. Raman scattering, UV-Vis-nir absorption and conductivity measurements vs acid vapor time exposure have been made. In fact, interesting and similar results have been observed by UV-Vis-nir on thin film of polyemeraldine base doped with HCl vapor [1] and on PANI-HCSA thin films deposited from chloroform and exposed to m-cresol vapor [2]. Raman spectra were recorded with the excitation lines from the blue range ( λ exc = 457.9 nm) to the red region ( λ exc = 676.4 nm). As expected, results are clearly affected during both processes. These modifications can be interpreted in terms of electronic and conformational changes of the chains, consistent with an increase of the conjugation length and of the delocalization of polarons.

Oligoanilines : from crystals to FET

Recently, FET technique led to doped materials without structural defects. Wishing applying this to oligoanilines (dimer and tetramer) we determined the crystal structures and we investigated the polarizability tensors via polarized Raman scattering. Xray diffraction and polarized ir revealed that evaporated thin films are layered textured, in relation to crystalline parameters. Thin film processing combined to physical properties of these oligomers is then an convenient way to realize electronic devices, such as OFET and sensors systems.

Effects of citrate and NaCl on size, morphology, crystallinity and microstructure of calcium phosphates obtained from aqueous solutions at acidic or near-neutral pH.

Precipitation of calcium phosphates occurs in dairy products and depending on pH and ionic environment, several salts with different crystallinity can form. The present study aimed to investigate the effects of NaCl and citrate on the characteristics of precipitates obtained from model solutions of calcium phosphate at pH 6·70 maintained constant or left to drift. The ion speciation calculations showed that all the starting solutions were supersaturated with respect to dicalcium phosphate dihydrate (DCPD), octacalcium phosphate (OCP) and hydroxyapatite (HAP) in the order HAP>OCP>DCPD. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses of the precipitates showed that DCPD was formed at drifting pH (acidic final pH) whereas poor crystallised calcium deficient apatite was mainly formed at constant pH (6·70). Laser light scattering measurements and electron microscopy observations showed that citrate had a pronounced inhibitory effect on the crystallisation of calcium phosphates both at drifting and constant pH. This resulted in the decrease of the particle sizes and the modification of the morphology and the microstructure of the precipitates. The inhibitory effect of citrate mainly acted by the adsorption of the citrate molecules onto the surfaces of newly formed nuclei of calcium phosphate, thereby changing the morphology of the growing particles. These findings are relevant for the understanding of calcium phosphate precipitation from dairy byproducts that contain large amounts of NaCl and citrate.

Polarized infrared reflectance spectra of brushite (CaHPO4·2H2O) crystal investigation of the phosphate stretching modes.

Polarized infrared (IR) reflectance measurements at near-normal incidence were recorded from the ac-plane of a monoclinic brushite (CaHPO4·2H2O) crystal in the 800-1200 cm(-1) spectral range (P-O stretching modes). The adjustment of these data, on the basis of a dispersion analysis (DA) model for monoclinic case, allowed the determination of oscillators parameters for the four P-O stretching observed modes of the phosphate group.

Raman and Infrared Studies of Substituted β-TCP

Several substituted â-tricalcium phosphates have been prepared with different cations (monovalent, divalent and trivalent) and at various levels of substitution. Structural investigations have proved that fewer than ~10% wt substitution, the substituted compounds are isostructural to â- TCP, leading to solid solutions. These samples have been characterized by infrared and Raman spectroscopies. The vibrational spectra show mainly the bands related to the vibrations of PO43- tetrahedrons present in the structure. As Raman scattering and infrared absorption are local probes, the bands are sensitive to the local environment of the distinct tetrahedrons, related to the site of substitution and to the nature of the cations.