Papers by Keyword: CaO-SiO2

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Authors: Antonio J. Salinas, J.M. Merino, N. Hijón, A.I. Martín, Maria Vallet-Regí
Authors: Priya Saravanapavan, Larry L. Hench
Authors: S.B. Cho, E.M. An, Sujeong Lee, H.D. Jang, Ill Yong Kim, Chikara Ohtsuki, Y.J. Kim
Abstract: Osteoconductive bone-repairing materials with mechanical properties analogous to those of human bone can be prepared through the combination of an osteoconductive ceramic filler with an organic polymer. Osteoconduction is archived from apatite formation on substrates. Previously, we reported that novel osteoconductive spherical particles in a binary CaO-SiO2 system were produced through a sol-gel process as ceramic filler for the fabrication of composites. In this study, we fabricated the composites consisting of polyetheretherketone (PEEK) and 30CaO·70SiO2 (CS) spherical particles and evaluated the effects of heat treatment in the range of 320-360 °C on apatite formation of the composites in a simulated body fluid. The prepared composites of PEEK and CS particles form hydroxyapatite on their surfaces in the simulated body fluid. The induction periods of hydroxyapatite on the composites decreased with increasing the amount of CS particles and decreasing the temperature for heat treatment. The apatite formation was affected by exposure of ceramic filler on the polymer matrix.
Authors: Ill Yong Kim, Chikara Ohtsuki, Masanobu Kamitakahara, S.B. Cho
Abstract: CaO-SiO2 gels for bioactive organic-inorganic composites were prepared from tetraethoxysilane (TEOS) and calcium nitrate tetrahydrate (Ca(NO3)2⋅4H2O) by a sol-gel method with the addition of the various amount of polyethylene glycol (PEG). The effects of PEG on morphology and bioactivity of the gel were investigated. The samples with the starting compositions of Ca(NO3)2 : TEOS = 30 : 70 in molar ratiowere prepared with or without coexistence of PEG. All the examined gels were obtained as a crack-free bulk bodies after gelation and aging. FT-IR spectra of the prepared gels showed that the gels have similar contents of silanol groups regardless of the amount of PEG. SEM observation showed that the gel consists of aggregates of 2-3 μm spherical particles with a diameter of 2-3 μm when it was prepared with the addition of PEG at a molar ratio of PEG : TEOS = 0.002 : 1, while it consists of aggregates of spherical particles with a diameter of 50 nm at a molar ratio of PEG : TEOS = 0.004 or 0.007 : 1. The size of the CaO-SiO2 powder can be decreased with increasing the amount of the added PEG. All the samples, regardless of the amount of the added PEG, formed apatite on their surfaces in a simulated body fluid (SBF) within 1 d. These results suggest that bioactive fine spherical particles with various size can be obtained through sol-gel processing under co-existence of appropriate amounts of PEG.
Authors: Robert N. Mead, G. Mountjoy
Abstract: Enhanced bioactivity has been observed for amorphous CaO-SiO2 sol-gels with 30mol% CaO, and several structural techniques have recently been used to investigate the structural basis for this bioactivity. The current work presents the first detailed atomic model of (CaO)0.3(SiO2)0.7 solgel after heat treatment at 600°C, produced using molecular dynamics. The model contains 1056 atoms in cubic box with length 24.1Å, and specifically incorporates hydroxyl groups which are characteristic of the sol-gel. The model is in good agreement with experimental X-ray and neutron diffraction results. Inspection of the model shows a network of SiO4 tetrahedra with an average connectivity of approximately 3. Ca have coordination of NCaO=5.3, in agreement with experimental results. On average, each Ca is surrounded by 4 other Ca, and visual inspection shows several large clusters of Ca. These clusters should influence the dissolution of Ca, and hence the bioactivity of (CaO)0.3(SiO2)0.7 sol-gel.
Authors: S.B. Cho, G.J. Yoon, E.M. An, Y.J. Kim, T.N. Kim, H.D. Jang, Euisup S. Shin, Chikara Ohtsuki, Ill Yong Kim
Abstract: We reported the apatite-forming ability of CaO-SiO2 spherical particles obtained through a sol-gel processing. In this study, we synthesized the CaO-SiO2 containing silver (Ag) ions using silver standard solution to induce antibacterial property and evaluated the effects of Ag on their apatite forming ability in a simulated body fluid (SBF). The particles with 30CaO·70SiO2 starting composition in Ag standard solution with range 0 to 500 ppm Ag content were synthesized through the sol-gel processing. The prepared 30CaO·70SiO2 could be obtained as spherical particles with regardless of Ag contents. The prepared Ag-contained 30CaO·70SiO2 particles formed apatite on their surfaces after soaking in SBF regardless of Ag contents. Consequently, Ag-contained 30CaO·70SiO2 spherical particle could be obtained without decrease of its apatite forming ability.
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