Papers by Author: Jeong Koo Kim

Abstract: Tissue-engineering must be either manufactured aseptically or sterilized after processing. To extend protection of medical devices against microbial contamination, various sterilization methods have been suggested. Hydrogen peroxide gas plasma sterilization has been applied in hospitals worldwide for almost a decade. In this study, we investigated the sterilization efficacy of hydrogen peroxide gas plasma sterilizer with porous polyurethane sample. The result is suggested that hydrogen peroxide gas plasma can be applicable to the sterilization of polymer scaffold for tissue engineering materials.

Abstract: Polyurethane foam was fabricated by ‘two-component method’ for changing cell structures. Compression force applied immediately to the polyurethane foam just after complete foam formation at the top of the mold for generation cell structure of negative Poisson effect. That is what we called pressure-controlled method. The polyurethane foam, produced by pressurecontrol method (CT), has significant higher resilience (52.3%) and similar level of shock absorption (47.5%) compared with control polyurethane foam (resilience is 21.5%, shock absorption is 54%). The PU foam with negative Poisson’s ratio showed excellent resilience with shock absorbance. The pressure-control method divided into two parts (CT0, CT1). The CT1 method is to apply compression force to the foam with time-delayed after foam formation. The PU foam produced by CT1 showed lower stress relaxation time, stress relaxation ratio, and maximum stress than CT0. Hence, CT1 foam is superior to other polyurethane foam as shock absorbing materials, such as shoes for diabetic patients.

Abstract: The effect of β-glucan-reinforced PLGA scaffold on cell proliferation was investigated. The PLGA scaffolds were prepared by salt-leaching method. The prepared scaffolds were grafted with (1→3) (1→6)-β-glucan in various ratios after plasma treatment on the surface. The surface of the scaffold was characterized by scanning electron microscope (SEM). The HDFs (Human dermal fibroblasts, 1
105 cells/scaffold) were used to evaluate the cell proliferation on PLGA scaffold before and after plasma/β-glucan treatment. In results, in the β-glucan treated scaffolds, the pores seemed to become narrower and even looked like closed form. The result of cell proliferation showed that the plasma/β-glucan treated scaffolds had narrower pores because the β-glucan was attached in the pores that would not be allowed the cells to penetrate into the inner areas. Consequently, cell proliferation was not effective in the plasma/β-glucan treated scaffolds in this study.

Abstract: PLGA (75:25)/hydroxyapatite (HA) composite films were fabricated by solvent-casting method to investigate the effect of various hydroxyapatite content ratio to the PLGA film for cellular attachment and proliferation. Mechanical property of the composite film was characterized by tensile test. The ultimate tensile strength of 10% HA content film was two folds higher than control group. The surface of the film was characterized by contact angle measurement. The PLGA/HA composite film was more hydrophilic than control film. In vitro chondrocyte responses to the composite films were measured by cellular attachment and proliferation test. The attached and proliferated cells were significantly higher on PLGA/HA (10%) composite film than control group (1.44 times higher in attachment test and 1.31 times higher for 6th-day at culture in proliferation assaying, p<0.05). Base on these finding, the PLGA/HA (10%) composite was effective for the cell attachment for the initial stage of cultivation and cell proliferation.

Abstract: Poly (D,L-latic-co-glycolic acid) (PLGA) has been used as the artificial scaffold for blood vessel formation. In order to hinder smooth muscle cell (SMC) angiogenesis, new scaffold design method of loading Epigallocatechin 3-O-gallate (EGCG) on PLGA film was introduced. PLGA and EGCG were dissolved in acetone and film-shape scaffold was manufactured. Antiangiogenetic effect of EGCG released on scaffold was analyzed for SMC and human umbilical vein endothelial cell (HUVEC) and method for selective inhibition from the difference of growth of SMC and HUVEC was suggested.

Abstract: This study fabricated polyurethane foam after transforming the cell structure from a convex polyhedral shape to a concave shape. Polyurethane was synthesized and fabricated after changing the cellular structure of the foam using two methods. Scanning electron microscopy showed that the cellular structure was a more concave structure than in control foam. The Poisson’s ratio of the experimental foam was negative. The average range of the Poisson’s ratio was –3.4~0, versus 0.3~1.3 for the control foam.

Abstract: In this study, human dermal fibroblast behaviors onto non-porous PLGA (75:25) films immobilized with 1, 10 and 100 µg/ml collagen (CN) or fibronectin (FN) were investigated according to different cell-seeding densities (1,000, 10,000 and 100,000 cells/ml). Cell attachment and proliferation were assessed using water soluble tetrazolium salt. The results indicated that 1 µg/ml of FN-immobilized PLGA film demonstrated significantly (p < 0.05) superior cellular attachment to the intact PLGA film after 4 hr of incubation. Moreover, the number of attached cells was shown to be directly proportional to that of initially seeded cells. After 48 hr, the cells showed significantly (p < 0.05) higher proliferation onto 1 or 10 µg/ml of FN-immobilized PLGA films than onto other PLGA films, regardless of the initial cell-seeding density. In terms of CN-immobilization, cell proliferation was appreciably increased but it was relatively lower than FN-immobilization. These results suggested that ECM-immobilization can enhance the cell affinity of hydrophobic scaffolds and be used to potential applications for tissue engineering by supporting cell growth.

Abstract: The surface properties of scaffolds are important since cell affinity is the most crucial factor to be concerned when the biodegradable polymeric material is utilized as a scaffold in tissue engineering. The surface of biodegradable non-porous poly (lactic-co-glycolic acid) (PLGA) scaffolds were treated by atmospheric pressure dielectric barrier discharge (APDBD). The wetting angle of APDBD treated PLGA were decreased from the untreated PLGA of 73° to 42°. FTIR-ATR analyses showed hydroxyl groups were not detected regardless of treated condition, but the intensities of both ether groups and carbonyl groups were increased with treatment time and oxygen flow rate. Treatment time and oxygen flux are equally effective to make the PLGA surface more hydrophilic.

Abstract: A culture system that is capable of providing even and uniform distribution and deposition of cells and extracellular matrix (ECM) is desired to enhance biological functions of the tissue-engineered artificial dermis (TEADs). For this purpose, we have developed a perfusion culture system that offers uniform exchange of nutrients and gases along the scaffold. Viability and effectiveness of the system were investigated by comparing biological and mechanical properties of TEADs. Results showed that the TEADs constructed by the perfusion culture system revealed significantly increased cell growth, ECM synthesis, and elastic modulus compared to those by the conventional static culture system. In addition, histological findings indicated that cells were more evenly distributed and ECM deposition increased in TEADs with the perfusion culture system. Therefore, it can be suggested that the perfusion culture system can constitute a more promising approach for constructing the TEADs.