Papers by Author: Bum Soon Lim

Abstract: Poly(lactic-co-glycolic)acid and silica gel fibers mixed non-woven fabric was made by electro-spinning method for the potential application as a bone grafting material. The silica gel, the source material for electro-spinning, was prepared by the hydrolysis of tetraethyl orthosilicate in the presence of calcium salt, water, hydrochloric acid and ethanol. Poly(lactic-co-glycolic)acid solution was prepared by dissolving it in the hexafluoroisopropanol. Then, they were transferred to two separate syringes which were connected to the high voltage supply generating a high electric field between the spinneret and the ground collecting drum. The silica gel containing calcium and poly(lactic-co-glycolic)acid solution were spun together under the electric field of 2 ㎸/㎝. The FE-SEM observations showed that the silica gel and poly(lactic-co-glycolic)acid fibers were mixed together completely and its handling property was much improved compared to that of the non-woven silica gel fabric. After soaking in the SBF for 1 week, low crystalline apatite crystals were also observed to occur on the silica fiber surfaces first and then they were also observed to occur on the poly(lactic-co-glycolic)acid fiber surfaces. From the results, it can be concluded that the poly(lactic-co-glycolic)acid and silica gel fibers mixed non-woven fabric made by electro-spinning method has a bioactivity. It means it has a potential to be used as a bone grafting material because of its apatite-forming ability, high surface area to volume ratio and high porosity.

Abstract: The poly(methyl methacrylate)/silica nano-composite made from trimethoxysilyl functionalized poly(methyl methacrylate) and dimethyl diethoxysilane was newly prepared and its apatite-forming ability and mechanical properties were evaluated comparing to poly(methyl methacrylate)/silica nano-composite made from trimethoxysilyl functionalized poly(methyl methacrylate) and tetraethyl orthosilicate. Its apatite-forming ability was similar to that of poly(methyl methacrylate)/silica nano-composite using tetraethyl orthosilicate but its fracture toughness was much improved. Its high fracture toughness might come from the less quantity of siloxane linkages in its structure because dimethyl diethoxysilane had only two ethoxysilane groups while tetraethyl orthosilicate had four ethoxysilane groups. From the results, it can be concluded that it has a possibility to be used as bioactive bone cement.

Abstract: Non-woven silica fabric was made by electro-spinning method for the potential application as a bone grafting material. The silica gel, the source material for electro-spinning, was prepared by the hydrolysis of tetraethyl orthosilicate in the presence of calcium salt, water, hydrochloric acid and ethanol. It was transferred to a syringe, which was connected to the high voltage supply generating a high electric field between the spinneret and the ground collecting drum. The silica fibers containing calcium were spun under the electric field of 2 KV/cm. Their diameters were in the range from about 0.3 μm to 8 μm. It was heat-treated at 300 oC for 3 hours. After soaking in the SBF for 1 week, low crystalline apatite crystals were observed to occur on their surfaces. From the results, it can be concluded that the non-woven silica fabric containing calcium made by electro-spinning method and then heat-treated has a bioactivity. It means it has a potential to be used as a bone grafting material because of its apatite-forming ability, high surface area to volume ratio and high porosity.

Abstract: Novel poly(ε-caprolactone)-organosiloxane hybrid containing amine group was synthesized through sol-gel method. Triethoxysilane end-capped poly(ε-caprolactone) was prepared by reaction with α,ω-hydroxyl poly(ε-caprolactone) and 3-isocyanatopropyl triethoxysilane. It was then hydrolyzed and co-condensed with aminopropyl triethoxysilane through sol-gel method. The success of hybridization was evaluated by FT-IR by new formation of siloxane group. Osteoblast-like cell responses were assessed on this new hybrid material for the potential application as a bone tissue engineering scaffold. The cell responses were compatible with those on pure poly(ε-caprolactone) used as a control.

Abstract: The method which gives a low crystalline hydroxyl carbonated apatite forming ability to originally non-bioactive high crystalline hydroxyapatite surface was newly developed. The granules of trabecular bovine bone, which had a size range from 212 to 1000 μm, were defatted, deproteinized, and then heat-treated at 1000 oC for 3 hours to remove organics completely. They were treated with the mixed solution of calcium chloride and calcium hydroxide in Soxhlet’s apparatus at 100 oC for 3 days and then dried completely. Low crystalline hydroxyl carbonated apatite was observed to occur on the surface of high crystalline hydroxyapatite granules after soaking them into the simulated body fluid (SBF) for 1 week. This method is likely to have a potential to be used as a new process to give a bioactivity to originally non-bioactive materials.

Abstract: Effect of poly(ε-caprolactone) structure on the mechanical properties and apatite-forming ability of poly(ε-caprolactone)/silica composite was investigated. Star-shaped poly(ε-caprolactone) was used in the experiment and it was end-capped with 3-isocyanopropyl triethoxysilane following the reaction with tetraethyl orthosilicate by sol-gel method. It was heat-treated at 150 oC for 24 hours and then tensile mechanical and dynamic viscoelastic testings were conducted, respectively. Its bioactivity was evaluated by the apatite forming ability in simulated body fluid at 36.5 oC. Its tensile strength was about 22 MPa while elastic modulus was about 2.6 GPa when the content of poly(ε-caprolactone) was 60 wt.%. The formation of apatite crystals on its surface was confirmed after 1 week of soaking in the SBF. The high elastic modulus of this composite was explained in terms of its 3-dimensional network structure.

Abstract: The biological activity of osteoblast-like MC3T3-E1 cells on the newly developed non-woven silica fabric was investigated. The attachment, proliferation, and differentiation of osteoblast-like MC3T3-E1 cells were evaluated by MTS and alkaline phosphatase activity assays, respectively. The non-woven silica fabric showed higher biological activities than those of tissue culture plates with regard to attachment and proliferation while there was no significant difference with respect to differentiation. These results suggest that the non-woven silica fabric has a potential application as a bone grafting materia

Abstract: Non-woven silica fabric was made by electro-spinning method for the application as a bone grafting material. The silica gel, the source material for electro-spinning, was prepared by the hydrolysis of tetraethyl orthosilicate in the presence of water, hydrochloric acid and ethanol. It was transferred to a syringe (spinneret), which was connected to the high voltage supply generating a high electric field between the spinneret and the ground collecting drum. The silica fibers were spun under the electric field of 2 KV/cm. Their diameters were in the range from about 100 nm to 5 µm. After soaking in the SBF for 4 week, low crystalline apatite crystals were observed to occur partly on their surfaces. From the results, it can be concluded that the non-woven silica fabric made by electro-spinning method has the apatite forming ability in the SBF and it means it has a potential to be used as a bone grafting material because of its apatite-forming ability, high surface area to volume ratio and high porosity.

Abstract: A bioactive chitosan-siloxane nano-hybrid material was newly developed and evaluated for the potential application as a bone graft material. The chitosan which can be dissolved in organic solvent was synthesized by the reaction with phtalic anhydride (Ph-Chitosan) and it was then reacted with 3-isocyanatopropyl triethoxysilane (Si-Chitosan) in dimethylformamide. Following this, the Si-Chitosan was hydrolyzed and condensed to yield a hybrid sol-gel material (Si-O-Chitosan). The gelation was carried out for 1 week at ambient condition in a covered Teflon mold with a few pinholes and then dried under vacuum at room temperature for 48 h. The bioactivity of the chitosan nano-hybrid material was evaluated by examining the apatite forming ability in the simulated body fluid (SBF). The surface microstructure and functional groups of the specimen was analyzed by field emission scanning electron microscopy and Fourier transformed infrared spectroscopy, respectively. The crystal phases of the specimen before and after the bioactivity testing were analyzed by thin film X-ray diffractometry. Newly developed chitosan nano-hybrid material showed apatite-forming ability in the SBF within 1 week soaking and this ability was believed to come from the silanol group formed on the surface of Si-O-Chitosan and calcium salt which increased the ionic activity product of apatite in the SBF.

Abstract: Bioactive poly(e-caprolactone)-siloxane hybrid material was newly developed and its in vitro and in vivo evaluations were made for the potential application as a bone substitute. The polymer precursor, triethoxysilane end capped poly(e-caprolactone) was prepared by the reaction with a,w-hydroxyl poly(e-caprolactone) and 3-isocyanatopropyl triethoxysilane with 1,4-diazabicyclo [2,2,2] octane as a catalyst and toluene as a solvent. The triethoxysilane end capped poly(e-caprolactone) was hydrolyzed and condensed to yield a hybrid sol-gel material. The gelation was carried out for 1 week at ambient condition in a covered Teflon mold with a few pinholes and then dried under vacuum at room temperature for 48 h. Its bioactivity was evaluated by examining the apatite formation on its surface in the SBF and its osteoconductivity was assessed in the tibia of white rabbit. The hybrid material showed apatite-forming ability in the SBF within 1 week soaking. Besides, new bone was formed on the surface of a cylindrical shaped specimen with no histologically demonstrable intervening non-osseous tissue after 6 weeks implantation. There was no evidence of inflammation or foreign body reaction. From the results, it can be concluded that this newly developed hybrid material has osteoconductivity and is likely to be used for the application as a bone graft substitute.