Papers by Keyword: Apatite

Abstract: Yttria-stabilized zirconia and alumina made significant contributions to the development of health care industry, specifically as orthopedic and dental materials. Both bioceramics are nearly inert ceramics, as they do not allow the interfacial bonding with tissue. Thus, it is necessary to provide bioactive surrounding as to elicit a specific biological response at the interface of material. This research reported the microstructure and bioactivity behavior of YSZ-Al₂O₃/10HAP with 30 wt. % and 60 wt. % of YSZ content. Powders were mixed before being compacted at 225MPa using uni-axial press machine. The composites were sintered at 1200 ̊C with heating rate of 10 ̊C/min. In-vitro bioactivity behavior of the composites were evaluated by immersing the composites into simulated body fluid. Results from x-ray diffraction pattern, confirmed the phase formation of apatite by the presence of Ca₂P₂O7, and CaO that might be useful on implant cell interaction in a body environment. The apatite formation was observed on the surfaces of the composites by SEM only after 9 days of immersion and subsequently apatite nucleation increased with prolonging immersion time. The dynamic changes in pH, between ion concentration in SBF and bioceramics surfaces correspondedwith an immersion time. Up to 30 days of immersion, the pH value of SBF stabilized approximately around pH 7.4-7.6, similar to the human blood plasma. Formation of apatite on composites surface of prepared YSZ-Al2O3/10HAP bioceramics may contribute to the improved biocompatibility and osteoconductivity.

Abstract: The low crystalline hydroxyl carbonate apatite forming capacity of a poly (70lactic-co-30glycolic acid)/15CaO-85SiO₂ composite, which had a dual pore structure, was newly examined in simulated body fluid. The bioactive 15CaO-85SiO₂ particles were synthesized by a sol-gel method using tetraethyl orthosilicate (TEOS) and calcium nitrate tetrahydrate under acidic condition followed by the heat treatment at 600°C for 3h. The poly (70lactic-co-30glycolic acid)/15CaO-85SiO₂ composite was then prepared by a solvent casting using dimethylformide as a solvent. The composite was loaded into a high pressure chamber and then carbon dioxide gas was introduced achieving a final pressure of 20 MPa. After 3 days, carbon dioxide gas was released quickly and resultantly the dual pore structure was obtained. The samples were observed by FE-SEM and its bioactivity was tested in simulated body fluid.

Abstract: Apatite containing-polymer beads have been prepared using two methods. The first series of scaffolds is obtained using an effortless procedure consisting in mixing the mineral phase in the polymer precursors, followed by crosslinking. The resulting materials contained agglomerates of inorganic particles. The second series of materials is generated through a more complex synthesis involving the alternate Ca²⁺/PO₄^3- soaking of the polymer beads. This leads to formation of nanometric apatite phase homogeneously distributed within and on the surface of the polymer substrates. The resulting materials have been characterized by infrared spectrometry, X-ray diffraction and scanning electron microscopy.

Abstract: Hydroxyapatite is a bioceramic material of great interest for use as bone substitute because of its similarity with the composition of biological apatite. Cationic and anionic substitutions in the apatite structure have been made in order to optimize the synthesis and accelerate the process of bone repair. In the present study, niobate apatite was synthesized by a patented aqueous precipitation method. The bioactivity of the samples was assessed by X-ray diffraction analyses (XRD), energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy with field emission gun (FEG-SEM; FEI Quanta FEG 250) in the samples before and after an incubation period in simulated body fluid. The results showed that after 3 days a bone-like apatite coating was formed onto the niobate apatite surface. A peculiar morphology comprised by nanosized wires was also observed on the niobate apatite surface.

Abstract: Based on the unique redox property of electrically conductive polymers, Ca²⁺ was incorporated into polypyrrole (PPy) film that previously doped with polyelectrolyte heparin. Then the apatite-forming ability of the Ca²⁺-doped PPy was examined by a biomimetic method using stimulated body fluid (SBF), which has ion concentration nearly equal to those of human blood plasma. It was found that the Ca²⁺-doped PPy successfully formed bonelike apatite deposition on its surface after soaking in SBF for only 3 days, whereas the similar apatite deposition was formed on Ca²⁺-free PPy after soaking in SBF for 7 days. These indicated that the entrapment of Ca²⁺ into PPy could accelerate the formation of apatite deposition and the Ca²⁺-doped PPy was possessed of enhanced bioactivity. It is expected that the Ca²⁺-doped PPy would be a useful bioactive coating material of metallic medical devices or tissue engineering scaffolds to promote the bone tissue regeneration.

Abstract: Surface properties of a material play a significant role in manipulating biological response of living body to artificial materials. The aim of this work was put on bioactivity assessment of TiO₂ ceramic after thermal treatment and further surface activation with UV-light. The in vitro apatite-forming ability was examined by soaking the samples into the simulated body fluid for several days. The research shows that nanostructural surface and UV irradiation accelerates formation of apatite on TiO₂ pellets.

Abstract: The low crystalline hydroxyl carbonate apatite forming capacity of a poly (70lactic-co-30glycolic acid)/15CaO-85SiO₂ composite, which had a dual pore structure, was newly examined in simulated body fluid. The bioactive 15CaO-85SiO₂ particles were synthesized by a sol-gel method using tetraethyl orthosilicate (TEOS) and calcium nitrate tetrahydrate under acidic condition followed by the heat treatment at 600°C for 3h. The poly (70lactic-co-30glycolic acid)/15CaO-85SiO₂ composite was then prepared by a solvent casting using dimethylformide as a solvent. The composite was loaded into a high pressure chamber and then carbon dioxide gas was introduced achieving a final pressure of 20 MPa. After 3 days, carbon dioxide gas was released quickly and resultantly the dual pore structure was obtained. The samples were observed by FE-SEM and its bioactivity was tested in simulated body fluid.

Abstract: Single-phase Ba₅(PO₄)₃Cl:Ce³⁺,Tb³⁺ (BPCl:Ce³⁺,Tb³⁺) samples have been synthesized via solid-state reaction method. The phase structure and luminescence properties are characterized using powder X-ray diffraction (XRD), photoluminescence excitation and emission spectra. Effective energy transfer occurs from Ce³⁺ to Tb³⁺ due to the observed spectral overlap between the emission band of Ce³⁺ and the excitation band of Tb³⁺. Ce³⁺/Tb³⁺-codoped Ba₅(PO₄)₃Cl shows more intense yellowish-green light compared to that of Tb³⁺-doped sample under UV light excitation.

Abstract: This work consisted in the development and characterization of a bioactive coating on Ti6Al4V samples by flame spray projection. A synthetichidroxyapatite powder was used to form the coatings. Oxygen and acetylene gas were used as combustible, and the metallic substrate was Ti6Al4V with a roughness of 0.4 and 2.3 μm. The time process varied from 5 to 60 seconds. The projection distance was of 22 cm.The spray coatings were mechanical tested; in all cases, the results indicated that the coatings were well adhered to the metallic surfaces and the metallic subtracts did not present any degradation of the mechanical properties. In addition, the coatings were immersed in simulated body fluids for 21 days in physiological conditions to evaluate the bioactivity. The results demonstrated that the coatings are potentially bioactive through the formation of a dense and homogeneous apatite layer similar to the bone. Results of X-ray diffraction exhibited evidence of a hidroxyapatite layer and by energy dispersive spectroscopy, a Ca/P ratio of 1.57 was obtained. This is an indication of that the use of flame spray projection to coat Ti6Al4V substrates do not decompose the original hidroxyapatite powder. Compositional analysis of the remnant fluids, made by inductively coupled plasma spectrometry, showed that nonmetallic ions were present in the coatings.

Abstract: Flotation behavior of apatite was investigated by micro-flotation with five kinds of fatty acid as collectors; the mechanism was studied by thermodynamic calculation. In the thermodynamic discussion, the Gibbs energy (∆G) of reactions, which is between the collectors and Ca2+ ions dissolved by apatite in pulp, were computed with pH as a function. A comparison of the calculated results with the flotation behavior of apatite shows that the thermodynamic results agree well with the experimental data. This finding indicates an identical characteristic between the two reactions with a variation in pH, in which one is between the collectors and Ca2+ ions dissolved by apatite in the pulp, and the other is between collectors and Ca2+ ions on apatite. Therefore, from the thermodynamic results, the mechanism for the flotation behavior of apatite could be deduced. The decrease in recovery is due to the decrease in effective constituent of collector (A–) with the falling pH. Once the concentration of A– ions is lower than a certain value, the reactions of the collectors with mineral are terminated and thus result in the depression of apatite in an acidic environment.