Papers by Author: Jong Chul Park

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: Glucans have been reported to stimulate immunity and to promote wound healing. Adult human dermal fibroblast (aHDF) cultured in serum free (serum-starvation). Proliferation of aHDF was measured at various concentrations of β-glucan by MTT assay, and migration was observed for 36h on microscope. The result of fibroblast bioassay, β-glucan had positive influence. In this study, the direct effects of β-glucan on proliferation and migration of human dermal fibroblasts were examined in vitro. That means β-D-glucan has the effect to enhance proliferation and aHDF migration speed, and has the potential as a wound healing agent.

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: In this study, such behaviors of vascular smooth muscle cells (VSMCs), as proliferation and migration, with serum stimulation were investigated onto (−)-epigallocatechin-3-O-gallate (EGCG)-blended poly(L-lactide-co-ε-caprolactone, PLCL) copolymers (EGCG-b PLCL). VSMCs were primarily cultured from rat aorta, and EGCG-b PLCL films were fabricated by mixing PLCL with EGCG. The proliferation of VSMCs cultured onto EGCG-b PLCL film was significantly suppressed in spite of serum induction. Moreover, recovery of denuded area by VSMCs receiving conditioned media obtained from EGCG-b films was completely inhibited, whereas VSMCs onto intact films migrated into denuded area in response to serum showing essentially complete recovery. These results suggest that inhibition in the behaviors of serum-stimulated VSMCs may be mediated through the anti-proliferative effects of EGCG released from polymer films, and EGCG-b polymers can be applied for fabricating an EGCG-eluting vascular stent.

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: Attachment and viability of different cell types(fibrioblast, chondrocyte and osteoblast ) was observed on two forms of silk (mat & Three-dimensional scaffolds). The osteoblasts behaviors cultured on silk mat were significantly higher than that found on 3-D silk fibroin scaffold (3-D SF scaffold). In the MTT assay, the cell viability of fibroblasts, chondrocyte and osteoblasts seeded on 2-D nanofiber mat was (2-D mat) significantly higher than that found on 3-D SF scaffold. Similar result could be seen from SEM observation and cell attachment study. However, alkaline phosphatase activity was significantly increased on 3-D SF scaffold than on2-D nanofiber

Abstract: Adhesions are abnormal attachments between tissues, caused by an inflammatory stimulus or trauma. It was generally used physical barriers and various agents to prevent from adhesions formation. In this study, we made an experiment on animals with wound covering material of substance to prevent tissue adhesion. It was performed in sub-acute toxicity, and tested local effects after implantation.

Abstract: Implantable neural prostheses form hybrid interfaces with biological constructs, and the application of electrical fields can restore functions of patients with neurological damages. The various stoichiometric compositions of iridium oxide were synthesized using reactive magnetron sputtering. The charge injection behavior of iridium oxide deposited with an O2/Ar ratio of 0.5 was similar to pure Ir. The charge density of iridium oxide increased with increasing O2/Ar ratio, and increasing thickness of iridium oxide.

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.