Hong-Chae Park

In vivo evaluation of porous hydroxyapatite/chitosan-alginate composite scaffolds for bone tissue engineering

Porous hydroxyapatite (HAp)/chitosan-alginate composite scaffolds were prepared through in situ co-precipitation and freeze-drying for bone tissue engineering. The composite scaffolds were highly porous and interconnected with a pore size of around 50-220 μm at low concentrations of HAp. As the HAp content increased, the porosity of the scaffolds decreased from 84.98 to 74.54%. An MTT assay indicates that the obtained scaffolds have no cytotoxic effects on MG-63 cells, and that they have good biocompatibility. An implantation experiment in mouse skulls revealed that the composite scaffold provides a strong positive effect on bone formation in vivo in mice. Furthermore, that HAp/chitosan-alginate composite scaffold has been shown to be more effective for new bone generation than chitosan-alginate scaffold.

Synthesis and application of terpolymer bearing cyclic carbonate and cinnamoyl groups

Abstract We propose the syntheses of photopolymer with pendant cinnamic ester and cyclic carbonate groups by the addition reaction of poly(glycidyl methacrylate-co-styrene) with CO2 and then with cinnamoyl chloride. Quaternary ammonium salts showed good catalytic activity for this synthesis. Photochemical reaction experiments revealed that terpolymer having cinnamate and cyclic carbonate groups has good photosensitivity, even in the absence of sensitizer. In order to expand the application of the obtained terpolymer, polymer blends with poly(methyl methacrylate) were prepared. Differential scanning calorimetry and optical clarity tests showed that the blends were miscible over the whole composition ranges.

Long and short range order structural analysis of In-situ formed biphasic calcium phosphates

BackgroundBiphasic calcium phosphates (BCP) have attracted considerable attention as a bone graft substitute. In this study, BCP were prepared by aqueous co-precipitation and calcination method. The crystal phases of in-situ formed BCP consisting of hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) were controlled by the degree of calcium deficiency of precursors. The long and short range order structures of biphasic mixtures was investigated using Rietveld refinement technique and high resolution Raman spectroscopy. The refined structural parameters of in-situ formed BCP confirmed that all the investigated structures have crystallized in the corresponding hexagonal (space group P63/m) and rhombohedral (space group R3c) structures.ResultsThe crystal phases, Ca/P molar ratio, and lattice parameters of in-situ formed BCP consisting of HAp and β-TCP were controlled by the degree of calcium deficiency of calcium phosphate precursors. The significant short range order structural change of BCP was determined by Raman analysis.ConclusionsThe long and short range order structural changes of in-situ formed BCP might be due to the coexistence of β-TCP and HAp crystal phases.

Preparation and characterization of La 0.8 Sr 0.2 Ga 0.8 Mg 0.1 Co 0.1 O 3- δ electrolyte using glycine-nitrate process

Conductivity of LSGMC materials were affected by secondary phase segregation, composition and synthetic route. (LSGMC) powders were prepared using the glycine nitrate process to produce high surface area and compositionally homogeneous powders. The powders were synthesized with different 0.5, 1, 1.5, 2, 2.5 of glycine/cation molar ratios. A single perovskite phase from the synthesized powders was characterized with X-ray diffraction patterns. The obtained sintered pellets showed the dense grain microstructure. In case of 1.5 molar ratio, its density was higher than the others. The electrical conductivity measured at was observed to be 0.131 . In addition, the linear thermal expansion behavior was indicated between and .

Degradation Behavior of Hydroxyapatite with Different Crystallinity in Simulated Body Fluid Solution

Hydroxyapatite (HAp) powders with different crystallinities were synthesized at various calcination temperatures through the co-precipitation of and . The degradation behavior of these HAp powders with different crystallinities was assessed in a simulated body fluid solution (SBF) for 8 weeks. Below , the powders were nonstochiometric HAp, and the single HAp phase was successfully synthesized at . The degree of crystallinity of the HAp powders increased with an increasing calcination temperature and varied in a range from 39.6% to 92.5%. In the low crystallinity HAp powders, the Ca and P ion concentrations of the SBF solution increased with an increasing soaking time, which indicated that the low crystallinity HAp degraded in the SBF solution. The mass of the HAp powders linearly decreased with respect to the soaking time, and the mass loss was higher at lower crystallinities. The mass loss ranged from 0.8% to 13.2% after 8 weeks. The crystallinity of the HAp powders increased with an increasing soaking time up to 4 weeks and then decreased because of HAp degradation. The pH of the SBF solution did not change much throughout the course of these experiments. These results suggested that the crystallinity of HAp can be used to control the degradation.

Synthesis and characterization of silicon ion substituted biphasic calcium phosphate

Si-substituted biphasic calcium phosphates (Si-BCP) were prepared by co-precipitation method. X-ray diffraction and fourier transform infrared spectroscopy were used to characterize the structure of Si-BCP powders. The Si-BCP powders with various Ca/(P+Si) molar ratio were carried out on structural change of hydroxyapatite (HAp) and -tricalcium phosphate (-TCP). The in-vitro bioactivity of the Si-BCP powders was determined by immersing the powders in SBF solution, after that observing the chemical composition and morphology change by X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy.

Suitability evaluation of magnesium substituted biphasic calcium phosphates prepared by coprecipitation method

Magnesium-substituted BCP (biphasic calcium phosphate) powders were prepared by incorporating small amounts of magnesium into the structure of different hydroxyapatite (HAp)/-tricalcium phosphate (-TCP) ratios through coprecipitation method. A series of magnesium substitutions ranging from 0, 0.5, and 1.0 wt%, which are comparable to the measured magnesium contents, were performed. The obtained powders were characterized by the following analytical techniques: X-ray diffraction analysis (XRD), Thermo Gravimetric Analyzer (TGA) and Fourier transform infrared spectroscopy (FT-IR). The results have shown that substitution of magnesium in the calcium-deficient apatites resulted in the formation of biphasic mixtures of different HAP/-TCP ratios after heating above . The 1.0 wt% magnesiumsubstituted-BCP were soaked in Hank`s solutions after 2 weeks to observe the morphology of the biocement, especially needle-like hydroxyapatite crystals and to estimate the length and diameter of nanoneedle crystals.

마이크로파에 의해 합성된 β-TCP/PLGA 복합체의 의사체액에서의 분해 거동

【The biodegradable

Characterization of the biodegradable behavior for biphasic calcium phosphates using X-ray diffraction and lattice parameter

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Determination of stoichiometric Ca/P ratio in biphasic calcium phosphates using X-ray diffraction analysis

-tricalcium phosphate (