Papers by Author: Chang Hyun Ahn

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Authors: Jin Suk Bae, Ga Young Jun, Akihiko Kikuchi, Teruo Okano, Chang Hyun Ahn, Young Jin Kim, Inn Kyu Kang, Oh Hyeong Kwon
Abstract: In this work, we developed a novel patterned co-culture method with thermo-responsive poly(N-isopropylacrylamide) (PIPAAm) and poly(N-ρ-vinylbenzyl-Ο-β-D-galactopyranosyl-(1→ 4)-D-gluconamide) (PVLA) inducing active hepatocyte attachment. Patterned graft of PIPAAm onto PS dishes was carried out by electron beam irradiation using cover-glass as a photomask. PVLA was only coated onto PIPAAm-ungrafted domain because of hydrated hydrophilic property of PIPAAm at below the LCST. Analysis by attenuated total reflection-Fourier transform infrared and electron spectroscopy for chemical analysis revealed that PIPAAm and PVLA were successfully grafted and coated on surfaces of PS dishes. PIPAAm-grafted surface exhibited decreasing contact angle by changing temperature from 37 to 20°C, while PVLA-coated PS and non-treated PS had negligible contact angle changes with temperature alternation. Atomic force microscopy (AFM) results showed that PIPAAm-grafted and PVLA-coated PS had smoother surfaces than that of ungrafted PS dishes. After culture for 12 hours, hepatocytes were well attached on PVLA-coated domain. Hepatocytes adherent on PIPAAm-grafted domain were detached by decreasing temperature. And then, fibroblasts were seeded onto PIPAAm pattern-grafted domain. Fibroblasts were only attached and spread onto PIPAAm-grafted domain. Co-cultured hepatocytes showed better differentiated function of albumin expression compared to homotypic hepatocyte culture
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.
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