Key Engineering Materials Vols. 330-332

Abstract: The purpose of this study was to compare the bone regenerative effect of calcium phosphate glass according to the particle size in vivo. We prepared two different sizes, that is 400 μm and 40 μm, of calcium phosphate glass powder using the system CaO-CaF2-P2O5-MgO-ZnO. Critical-sized calvarial defects were created in 60 male Sprague-Dawley rats. The animals were divided into 3 groups of 20 animals each. Each defect was filled with a constant weight of 0.5 g calcium phosphate glass powder mixed with saline. As controls, the defect was left empty. The rats were sacrificed 2 or 8 weeks after postsurgery, and the results were evaluated using histological as well as histomorphometrical studies. The particle size of the calcium phosphate was crucial; 400 μm particles promoted new bone formation, while 40 μm particles inhibited it because of severe inflammation.

Abstract: The porous apatite-wollastonite bioactive glass-ceramic (AW-GG) was made from nano-precursor powders derived from sol-gel process, and shaped by dipping method with polymer foam. The physical-chemical properties, bioactivity and biocompatibility of the materials were studied by means of TG, XRD, SEM, TEM and so on. The bioactivity was investigated in simulated body fluid (SBF) and the biocompatibility was evaluated by co-culturing with marrow stromal cells (MSCs). The result shows that: the particle size of the AW precursor powders is 40~100nm; porous AW GC has three-dimensional pored structure with 300~500um macropores and 2~5um micropores; the materials possess high bioactivity and biocompatibility. Porous AW GC may therefore have great potential application as bone tissue engineering scaffold.

Abstract: Factors controlling the antibacterial ability of three bioactive glasses were studied by comparing the changes in the SBF during immersion of the glasses with their response to four microorganisms. After immersion of 100 mg/ml fine powder (<45μm) of the glasses in the SBF for 1, 2, 4, 8, 16, 27 and 48 hours, the immersion solutions were filtered and the pH in the bulk solution was measured. Ionic concentrations of Na, K, Ca, Mg, P and Si ions in the immersion solutions were determined by ICP-OES. The antibacterial activity of the glasses showed good correlation with the changes of the pH values in the SBF solutions. No correlation was found between the ionic concentration and the antibacterial ability of the three glasses against the four tested microorganisms. The results suggest that, the antimicrobial effect of the glass powder against the microorganisms tested is mostly dependent on the increase of the pH in the solution to values detrimental for the bacteria growth.

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.

Abstract: fabricated by pressureless sintering process. The effect of BG on the sintering ability and mechanical strength of the ceramics, and the adhesion and proliferation of osteoblasts were investigated. The results showed that the optimum amount of BG was 20wt.% and the samples sintered at 1100oC for 5h revealed a bending strength of 172 MPa, which was approximately 2-times higher than that of the pure CaSiO3 ceramics. The cell experiments showed that BG reinforced CaSiO3 ceramics supported osteoblast adhesion and possessed higher proliferation than that of the pure CaSiO3 ceramics, which indicated excellent biocompatibility. Our results suggested that BG reinforced CaSiO3 ceramics could be potential candidates as bioactive bone implant materials.

Abstract: The aim of this study is to find out the crystallization behaviour and in-vitro bioactivity character of machinable glass ceramics having different ratios of Na/K mica and apatite phases, to ascertain the best machinable composition. In order to investigate the bioactivity behavior of the samples the simulated body fluid (SBF) was prepared. Samples were removed from the solution after 1 hour, 1 day, 1, 2, 3 and 4 weeks. FEG-SEM was used to characterize the morphology of precipitation HCA layer on the surface depending on time. Molecular bonding characterization of HCA layers were carried out by using Fourier Transform Infrared Spectroscopy (FTIR) technique. The thin film X-ray diffraction (TF-XRD) analysis was used to characterize the variation of chemical composition on precipitated layer by time. Optimum results were obtained by the composition, containing 70wt% Na/K mica and 30wt% fluorapatite which had an average mica size of 3-4 microns.

Abstract: Composite biomaterials of calcinated bovine bone derived hydroxyapatite (HA) doped with 5 and 10 wt% commercial inert glass (CIG) were prepared by sintering. The production of HA from natural sources satisfies economic and time-saving aims, while the use of CIGs is directed by economic and ecological aspects. The produced composites were subjected to scanning electron microscopy (SEM) and X-ray diffraction analysis. Measurements of compression strength, microhardness, and density were also carried out. The experimental results and their discussion showed that the type and the composition of incorporated glass are of crucial importance. Consequently, provided that an optimum amount of glass is incorporated, the resultant materials can exhibit good values of compression strength and microhardness and hence they can be suggested for potential use in load-bearing biomedical applications.

Abstract: We observed the cytotoxicity of human bone marrow stromal cells(hBMSCs) by microparticles of bioactive glass with four particle groups(same chemical composition-45S5 but produced by two different manufacturer and two different size groups). In vivo test using rat calvaria were also carried out. The apoptosis rates of all small particle groups(10-20 ㎛) were increased than large(500-700 ㎛ or 200-900 ㎛) particle groups in any culture time and any amount of particles with statistical significance. In vivo study we observed pathologic signs such as macrophages and foreign-body giant cells in rat calvaria by micro-particles of bioglass. Small(10- 20 ㎛) sized particles induced foreign body reaction and bone resorption. There was proliferation of macrophages and cells in large number. But in large particle groups, only fibroblasts were surrounding the particles. The micro-particles of bioglass induced apoptosis of hBMSC and foreign body reaction in calvaria of rat, therefore micro-particles of bioglass may cause osteolysis if used in replacement arthroplasty.

Abstract: Nano-sized β-tricalcium phosphate (nano-sized β-TCP) was synthesized by dialysis process using Ca(NO3)2·4H2O and (NH4)2HPO4 as starting materials. The time needed for the whole process is much shorter than other reported methods. In this new synthesis, dialysis was used to remove the unwanted ions, and the removal efficiency of impurity ion was evaluated by comparing the representative ion NH4 + between the original slurries and deionized water outside of the dialysis tube. The resulting powders were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), and chemical analysis. Results showed the final products are pure β-TCP. The pictures of high resolution-transmission electron microscope (HR-TEM) further indicated that β-TCP crystals are around 100nm in diameter.

Abstract: The gelation process is of importance for the structure and texture of the silica particle and further functionalization in the area of biomedical application. In a base-catalysis process the sodium phosphate or plus calcium nitrate salts could be added to induce the gelling velocity and particle size distribution. Multivalent anions (phosphate ions) or dication (calcium ions) induce the microscopic phase separation and accelerate gelation of silica sol. Furthermore, the composite silica nanospheres show excellent monodispersibility as well as pH-stability in the simulated body fluids or Tris-HCl buffer solution, which will help to surface modification and functionalization in the biomolecule-existing environments.