Papers by Author: Kwan Han Yoon

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Authors: So Hee Yun, Ga Young Jun, Kwan Han Yoon, Yong Soon Park, Young Jin Kim, Inn Kyu Kang, Oh Hyeong Kwon
Abstract: Biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofibrous matrix containing gelatin was fabricated by electrospinning method. The average diameter of electrospun PHBV/Gelatin (1:1) nanofibers was 600 nm determined by FE-SEM. ATR-FTIR and ESCA measurements were used to confirm the presence of gelatin in PHBV/Gelatin nanofibers. Human fibroblasts' behavior on PHBV/Gelatin nanofibrous matrix has been investigated. Fibroblasts were well attached on the surface of control PHBV and PHBV/Gelatin nanofibers. Initial cell attachment on PHBV/Gelatin nanofibers was higher than that of control PHBV nanofibers. Gelatin has many RGD moiety that mediate cell attachment. From this reason, initial cell attachment increased on the surface of PHBV/Gelatin nanofibers. From the results, coelectrospinning of PHBV and gelatin is a promising method for tissue engineering scaffold.
Authors: Young Gwang Ko, Hyeon Ae Jeon, Kwan Han Yoon, Young Chul Kim, Chang Hyun Ahn, Young Jin Kim, Oh Hyeong Kwon
Abstract: PHBV ultrafine fibers were fabricated by electrospinning process. Electrospun PHBV fiber structures revealed randomly aligned fibers with average diameter of 400 nm. PIPAAm was grafted on the surface of PHBV nanofibrous mat by electron beam irradiation. PIPAAm-grafted PHBV mats were determined by ATR-FTIR and ESCA. Water contact angles were determined by a sessile drop method at 20 and 37. To examine the tissue compatibility, human fibroblasts were evenly seeded onto PIPAAm-grafted PHBV mat and cast film, ungrafted PHBV mat and film. Attached and spread fibroblasts on nanofibrous mat were proliferated more rapidly than that of flat film surface. Initial cell attachment on PIPAAm-grafted surfaces was higher than ungrafted surfaces. The surface property changed to hydrophilic by PIPAAm graft, which increased initial cell attachment. Detachment of single cells from PIPAAm-grafted PHBV matrixes was measured by low temperature treatment after incubation at 37. Cultured cells were rapidly detached from PIPAAm-grafted PHBV mat compared with film. With porous mats, the water molecules easily reach to grafted PIPAAm from underneath and peripheral to the attached cells, resulting in rapid hydration of grafted PIPAAm molecules and detachment of the cells.
Authors: Chang Hyun Ahn, Young Jin Kim, Inn Kyu Kang, Ga Young Jun, Young Gwang Ko, Kwan Han Yoon, Oh Hyeong Kwon
Abstract: In this study, we prepared polystyrene (PS) nanofibers as hepatocytes culture substrates by electrospinning method and subsequently coated with specific ligand (poly(N--vinylbenzyl-- β-D-galactopyranosyl-(14)-D-gluconamide)(PVLA) for hepatocytes attachment. Rat hepatocytes’ behavior on the PVLA-coated and non-coated PS nanofibrous matrices have been investigated. Electrospun PS fiber structures revealed randomly aligned fibers with average diameter of 500 nm. Fabricated PS nanofibers had no bonding points like cotton fibers. Analyses by ATR/FTIR and ESCA revealed that PVLA was successfully coated to the surfaces of PS nanofibers. More hepatocytes were attached on the surface of PS nanofibers coated with PVLA than that on noncoated PS nanofibers. PS nanofibrous matrix could incorporate many cells into the interior of the matrix probably due to the suitable pore size. Cell viabilities cultured on PVLA-coated PS nanofibrous mats were maintained for 2 weeks, while it was decreased rapidly on PVLA-coated PS dishes. High hepatic function especially albumin secretion was maintained for 2 weeks on nanofibrous mats but rapidly decreased on flat PS dishes. These results indicate that nanofibrous structure enabled spheroid-like culture results in providing cell-cell communication and subsequent long-term maintenance of specific cell function.
Authors: Young Gwang Ko, Kwan Han Yoon, Chung Park, Moon Hee Sung, Oh Kyoung Kwon, Chang Hyun Ahn, Young Jin Kim, Oh Hyeong Kwon
Abstract: Poly(γ-glutamic acid)(γ-PGA) based nanofiber sheets were prepared by using electrospinning technique to evaluate the ability of the prevention of postoperative tissue adhesion. The anti-adhesion membranes were prepared from poly(γ-glutamic acid) and PLGA with different compositions by electrospinning. Also nonsteroidal anti-inflammatory drug (ibuprofen) was incorporated during fabrication of nanofibers. Various electrospun nanofibers were characterized by the measurements of microstructure (surface morphology and fiber diameter by SEM), ATR-FTIR, water contact angle and in vivo animal study using Sprague Dawley rat model. The average diameter of nanofibers electrospun from trifluoroacetic acid (TFA) solution ranged from 300 nm to 900 nm, approximately. From in vivo animal study, it was observed that ibuprofen-incorporated γ- PGA nanofiber sheet was significantly effective in preventing tissue adhesion and inducing wound healing, probably due to the appropriate hydrophilicity of γ-PGA preventing shrinkage of the sheet and appropriate barrier property, while PLGA nanofibrous mat was dramatically contracted in in vivo due to its high hydrophobicity resulted in insufficient coverage of wound.
Authors: Young Gwang Ko, Kwan Han Yoon, Jin Ho Jang, Masayuki Yamato, Akihiko Kikuchi, Teruo Okano, Inn Kyu Kang, Oh Hyeong Kwon
Abstract: Rapid recovery of cell sheets is considered important to maintain the biological function and viability of recovered cell sheets. To accelerate required culture substrate hydrophilic/ hydrophobic structural changes in response to culture temperature alteration, poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(N-isopropylacrylamide) (PIPAAm) were grafted successively onto tissue culture polystyrene (TCPS) dishes by electron beam irradiation. Analysis by attenuated total reflection-Fourier transform infrared revealed that PHEMA and PIPAAm were successfully grafted to surfaces of TCPS dish. PIPAAm-PHEMA-grafted TCPS (PIPAAm-PHEMA-TCPS) dishes were compared with PIPAAm-grafted TCPS dishes for cell sheet detachment experiments. Approximately 75 min was required to completely detach cell sheets from PIPAAm-TCPS dish, compared to only 13 min to detach cell sheets from PIPAAm-PHEMA-TCPS dish, which is successively grafted with PHEMA and PIPAAm. PHEMA is a well-known as a high hygroscopic polymer. In the case of PIPAAm-PHEMA-TCPS dish, PHEMA layer acted as a water pool to accelerate the hydration of PIPAAm layer due to the effective and simultaneous water supply to PIPAAm layer, resulting in rapid hydration of grafted PIPAAm molecules and detachment of cell sheet compare to PIPAAm-TCPS dish without PHEMA layer.
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