Papers by Author: Gil Son Khang

Abstract: Recently, nanomaterials have received considerable attention because of their potential applications in the biomedical field. In the present study, we investigated the effects of nano-sized calcium metaphosphate (CMP) particles (50 nm) compared with micro-sized CMP particles (200-500 nm and 10 μm) on the proliferation and osteoblastic differentiation of human bone marrow stem cells (BMSCs). BMSCs were challenged with CMP particles with different sizes for 3, 5, and 7 days. An analysis of the proliferation revealed that the nano-sized CMP particles (50 nm) stimulated the proliferation of BMSCs up to 27.79% compared to the untreated control. This stimulatory effect of the nano-sized CMP particle was dose-dependent. CMP particles appeared to adhere on the surface of BMSCs but this did not cause distinguishable morphological changes. Moreover, all CMP particles (50 nm to 10 μm) were capable of stimulating an osteoblastic differentiation of BMSCs as accessed by alkaline phosphatase (ALP) and von Kossa stainings. Further molecular analysis revealed that all the CMP particles induced an expression of osteoblast-related genes such as osteocalcin (OC) and collagen I (Col I). Taken together, our data demonstrate that nano-sized CMP particles have the potential to stimulate the proliferation and osteoblastic differentiation of BMSCs.

Abstract: We developed the successive roller type of microneedle system without pain to improve the permeation of drug through the skin barrier. The permeation rates of FITC-ovalbumin (OVA, MW: 45,000g/mole), FITC-insulin (MW: 5,733 g/mole) and FITC-bufexamac (MW: 227.37 g/mole) as model drugs were determined by modified Franz diffusion cells using the microneedle device with four times treatment. The average penetration fluxes of FITC- OVA, FITC-insulin and FITC-bufexamac were steeply increased from 13.4 to 83.3, 10.1 to 110.6 and 11.9 to 242.6 pmol/cm2 with treatment for 12 hrs, respectively. The lower the molecular weight of the drugs, the more the permeation flux investigated. In conclusion, we confirmed the possibility of the application for transdermal delivery of the larger molecular drugs as protein using the designed microneedle treatment device.

Abstract: The double-layered microspheres play an important role in controlling drug delivery for pharmaceutical application, because of the low initial burst compared with single-layered spheres and targetable delivery to specific organ. But it has drawback in loading drug and controlling size. In this study, we developed double-layered spheres using relatively simple oil-in-water (O/W) solvent evaporation method using bovine serum albumin (BSA) as water-soluble protein and poly(D,L-lactide-co-glycolide) (PLGA). BSA/PLGA double-layered microspheres were fabricated using O/W solvent evaporation method and investigated the specific character of double-layered microspheres according to the kind of surfactants. In SEM observation, double layered microsphere had spherical shape and smooth surface without pores. And the double layered microsphere using O/W solvent evaporation method was transparency because of slow evaporation of solvent. In fluorescent observation, we observed the fluorescent core in the double-walled spheres composed of FITC-BSA and PLGA using fluorescent observation. In the case of polyvinylalcohol as emulsifier, the yield was better than gelatin. As decreased concentration of PLGA, the size of double-layered microspheres deceased.

Abstract: To develop osmotic granule with semi-permeable membranes, we prepared the semipermeable membranes with different pore forming agent by using solvent casting method. The membrane was consisted of cellulose acetate, Eudragit® RS, hydroxypropylcellulose (HPC), and triethylcitrate (TEC) in the presence of PEG200, PEG1, 000, or dibutylsebacate(DBS) as a pore forming agent. The produced membranes were white and elastic and exhibited soft property on touch. The release amount of pore forming agent from membrane with different pore forming agent was measured in water dissolution media and the order was PEG200 > PEG1, 000 > DBS. The formation of pore in membrane was observed by morphological SEM image after dissolution. The pore formation and porosity of membrane depended on water solubility of pore forming agent. We confirmed that pores in porous semi-permeable membrane could be controlled by the pore forming agent.

Abstract: In order to application for the tissue engineered intervertebral disc (IVD), we designed the synthetic/natural hybrid scaffolds with poly(lactide-co-glycolide) (PLGA) and small intestine submucosa (SIS). SIS has been widely used as a biomaterial because SIS consists of various collagens and cytokines. SIS, however, possesses disadvantages such as their weak mechanical properties and uncontrolled degradation. Novel composite scaffolds of PLGA/SIS were manufactured by simple immersion method of PLGA scaffolds in SIS solution under vacuum. Then SIS was crosslinked. Also, PLGA scaffolds and SIS sponges were manufactured by solvent casting/salt leaching and freeze-dried methods, respectively. We evaluated pore structure, porosity, water absorption ability and cell viability of three types of scaffolds for the application of IVD.

Abstract: In this study, we developed an injectable carrier for demineralized bone matrix (DBM) which consists of chitosan and glycerol phosphate (GP). The phase transition behaviors of chitosan and GP solution characterized as a function of temperature. The chitosan and GP solutions were shown to form a sol at room temperature, and the chitosan solution with 10-20 wt% concentrations were found to undergo sol-to-gel phase transitions as the temperature was increased. In situ gel forming implant in vivo was successfully fabricated by simple subcutaneous injection of chitosan and GP solutions with demineralized bone matrix (DBM). von Kossa images of the gel implant formed from solution with DBM revealed the presence of mineral deposits.

Abstract: Recently, it has been studied tissue engineered technique as novel approaches for treatment of the degenerative intervertebral disc (IVD). We designed the hybrid type of IVD mimicked scaffolds with poly(lactide-co-glycolide) (PLGA) and methoxypoly(ethyleneglycol)- poly(
-caprolactone) (MPEG-PCL) diblock copolymers in order to application for the tissue engineered IVD. The MPEG-PCL solutions formed a gel-to-sol phase transitions as the temperature was increasesd. MPEG-PCL diblock copolymers were prepared by ring opening polymerization, and then nucleus pulposus (NP) cell was impregnated. Also, in order to restore annulus fibrosus (AF), we fabricated PLGA scaffold by solvent casting/salt leaching method. We confirmed disc cell function in manufactured scaffold through MTT assay in vitro and gross morphology and special staining in vivo for the possibility of the application of tissue engineering techniques.

Abstract: This study was designed to investigate the influence of demineralized bone particles (DBP)/PLGA hybrid scaffold on angiogenesis and osteogenesis in a calvarial defect model. DBP/PLGA scaffolds were manufactured by solvent casting/salt leaching method, and each scaffold contained 0, 10, 20, 40, and 80 wt% DBP of PLGA, respectively. A total of 34 rats were operated and bicortical holes were placed on their calvaria. The defects were filled with different ratio DBP/PLGA scaffolds. After 3, 7, 14, and 28 days, specimens were taken and, histologic, immunohistologic and RT-PCR analyses were carried out concerning number of vessels and density of regenerated bone, and angiogenic activation. On days 7, in all experimental groups, bone formation occurred in a direction from defected margin of calvarium to center of implanted scaffold and new vessel formation took place in front of the osteogenic regeneration front. We found that the 20 and 40 wt% DBP/PLGA scaffold was superior in its ability to regenerate new bone, induced more intensive formation of microvasculature and expressed in a higher level of osteocalcin mRNA than other groups.

Abstract: To develop a wound dressing that can be removed from the injured skin without the damage and supporting rapid healing, we made hybrid dressing of small intestinal submucosa (SIS) and hydrogels. Alginate and gelatin used as a dressing material in hydrogels were selected to coat SIS sheets. Characteristics and tendency of wound healing of prepared sheets were investigated. Water uptake ability was greater when the sheets were coated with gelatin than alginate although both showed higher water absorption than the native SIS sheets, but the degradation rate of alginate/gelatin coated SIS was slower than that of native SIS because both polymers may delay contact time of enzyme to the SIS surface in solution. It was observed that less of fibroblasts attached to the natural polymer coated SIS sheets. This property will make easy for the detachment of the sheet from the defected tissue. Wound closure examination showed that prepared sheets enhanced wound healing. It was concluded that prepared alginate/gelatin coated SIS sheets are positively regarded as an appropriate biodegradable wound dressing that is reducing patient’s pain during change of the dressing.