Abstract
Hydroxyapatite (Ca10(PO4)6(OH)2) is widely used as bio-ceramic materials and as adsorbents for separation of bio-molecules. These materials have also been used as adsorbents for heavy metals, supports and as catalysts in oxidation and dehydrogenation reactions. The catalytic performance of these materials depend on the lattice substitution of Ca sites in Hydroxyapatite structure by varied cations as Na, Mg, Sr and Mn, which result in changes in various structural pro perties as crystallinity and morphology. Pure calcium hydroxyapatite (S1) and Cr loaded hydroxyl apatite (S2, S3, S4 and S5) of different chromium concentrations have been prepared by wet precipitated method. An in-vitro examination is essential to investigate the mechanism of the deficient HA and tissue interface reaction by preparing SBF (Simulated Body Fluid) through the elemental and chemical analysis of Ca, P and Cr. FTIR used to analyze the samples after incubation in SBF for 24 day. PH of the samples also was measured at the first period of immersion time. At high loading of chromium ions, the formation of carbonate apatite decrease. The concentrations of the chromium in the Cr_HA crystal during the soaking in SBF are very safe dose for human.
Highlights
Hydroxyapatite (HAp), chemical formula Ca5(PO4)3OH, is considered the structural template for the mineral phase of bone, dentin and enamel
Calcium phosphate bioceramic powder was prepared by an aqueous precipitation technique using 0.16 Mole of calcium nitrate titrahydrate [Ca(No3)2·4H2O] as a source of calcium which dissolving in one liter of de-ionized water and 0.096 Mole of di-ammonium hydrogen orthophosphate [(NH4)2HPO4] as a source of phosphorous which dissolving in one liter of de-ionized water
The elemental analysis of the phosphorus and calcium ions after immersion of the samples in simulated body fluid (SBF) for 24 day at temp. 37 ̊C, showed that, when the samples incubated in SBF, there were significant differences between the samples and the controls for chemical analysis
Summary
Hydroxyapatite (HAp), chemical formula Ca5(PO4)3OH, is considered the structural template for the mineral phase of bone, dentin and enamel. The close relationship between substitutions and bioactivity of synthetic substituted HAp has been demonstrated by in vitro and in vivo studies [1]. Chromium-loaded hydroxyapatite catalysts Cr(x)/CaHAp (0.1 _ x _ 3.7 wt.% Cr) was prepared by ion exchange and characterized by several techniques including FTIR, Raman, XPS, UV-vis-NIR spectroscopies. Several isolated chromium species were identified the surface Cr3+ ions in distorted octahedral symmetry, bulk octahedral Cr3+ ions, octahedral Cr5+ ions in low concentration and Cr6+ ions. The Cr6+ ions present as monochromates are predominant only at very low loadings (x _ 0.1 wt.%Cr) whereas, at higher Chromium amounts (up to 3.7 wt.% Cr), Cr3+ species are preponderant The majority of Cr3+ ions are located on the apatite surface; they do not form Cr2O3 crystallites but isolated Cr3+-O-Ca2+ or Cr3+-O-Cr3+ entities at the highest Cr amounts. Isolated Cr3+ species are believed to be responsible for the propylene formation (propylene yield around 7% at 550 8 ̊C)
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