45 research outputs found
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