X-ray microanalysis in STEM of short-term physico-chemical reactions at bioactive glass particles / biological fluids interface. Determination of O/Si atomic ratios

Short-term physico-chemical reactions at the interface between bioactive glass particles and biological fluids are studied and we focus our attention on the measurements of O/Si atomic ratio. The studied bioactive glass is in the SiO2-Na2O-CaO-P2O5-K2O-Al2O3-MgO system. The elemental analysis is performed at the submicrometer scale by STEM associated with EDXS and EELS. We previously developed an EDXS quantification method based on the ratio method and taking into account local absorption corrections. In this way, we use EELS data to determine, by an iterative process, the local mass thickness which is an essential parameter to correct absorption in EDXS spectra. After different delays of immersion of bioactive glass particles in a simulated biological solution, results show the formation of different surface layers at the bioactive glass periphery. Before one day of immersion, we observe the presence of an already shown (Si,O,Al) rich layer at the periphery. In this paper, we demonstrate that a thin electron dense (Si,O) layer is formed on top of the (Si,O,Al) layer. In this (Si,O) layer, depleted in aluminium, we point out an increase of oxygen weight concentration which can be interpreted by the presence of Si(OH)4 groups, that permit the formation of a (Ca,P) layer. Aluminium plays a role in the glass solubility and may inhibit apatite nucleation. After the beginning of the (Ca,P) layer formation, the size of the electron dense (Si,O) layer decreases and tends to disappear. After two days of immersion, the (Ca,P) layer grows in thickness and leads to apatite precipitatio

Atomic transfers between implanted bioceramics and tissues in orthopaedics surgery

We study transfers of ions and debris from bioceramics implanted in bone sites. A contamination of surrounding tissues may play a major role in aseptic loosening of the implant. For these reasons, bioceramics require studies of biocompatibility and biofunctionality . So, in addition to in vitro studies of bioceramics, it is essential to implant them in vivo to know body reactions. We measured the concentration of mineral elements at different time intervals after implantation over a whole cross-section. We found a discontinuity of the mineral elements (Ca, P, Sr, Zn, Fe) at the interface between the implant and the receiver. The osseous attack is not global but, on the contrary, centripetal. Moreover, the fit of the concentration time course indicates that the kinetics of ossification is different for each atomic element and characterizes a distinct biological phenomeno

Properties of two biological glasses used as metallic prosthesis coatings and after an implantation in body

présentation faite par Y. Barbottea

Biological activity of a SiO2-CaO-P2O5 sol-gel glass highlighted by PIXE-RBS methods

It is proposed in this study to observe the influence of P2O5 on the formation of the apatite-like layer in a bioactive glass via a complete PIXE characterization. A glass in the SiO2-CaO-P2O5 ternary system was elaborated by sol-gel processing. Glass samples were soaked in biological fluids for periods up to 10 days. The surface changes were characterized using Particle Induced X-ray Emission (PIXE) associated to Rutherford Backscattering Spectroscopy (RBS), which are efficient methods for multielemental analysis. Elemental maps of major and trace elements were obtained at a micrometer scale and revealed the bone bonding ability of the material. The formation of a calcium phosphate-rich layer containing magnesium occurs after a few days of interaction. We demonstrate that the presence of phosphorus in the material has an impact on the development and the formation rate of the bone-like apatite layer. Indeed, the Ca/P atomic ratio at the glass/biological fluids interface is closer to the nominal value of pure apatite compared to P2O5 free glasses. It would permit, in vivo, an improved chemical bond between the biomaterials and bone.Comment: presented at CAARI 2006:19th International Conference on the Application of Accelerators in Research and Industry, Forth Worth, Etats Unis, 20-25 Aug 2006, 11 pp, 4 figures, submitted to NIM

Influence Du Dopage En Zinc Et En Manganese Sur La Cinetique De Resorption D'un Implant D'hydroxyapatite Et Etude Des Effets De Matrice Dans La Methode Nucleaire P.i.x.e. Utilisee

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Controlled Bioactivity in Zn-doped sol-gel derived SiO2-CaO bioactive glasses

Sol-gel derived glasses based on SiO2-CaO were studied with and without Zn as doping element. Investigations of their in vitro bioactivity were performed by soaking the glass powders in biological fluids for time periods up to 4 days. The surface reactions were characterized at the micrometer scale and with a high level of efficiency for both major and trace elements by using Particle Induced X-ray Emission (PIXE) associated to Rutherford Backscattering Spectroscopy (RBS). The evolution of the biological medium composition was followed by ICP-AES analyses. If the bioactivity of binary SiO2-CaO glasses is already known, this study shows the improvement of the early step of the bioactive process by using zinc as a doping element. Indeed, zinc improves the specific surface area and then the number of sites for the nucleation of calcium phosphate precipitates. In addition, Zn-doping slows the 1 Corresponding author