• 한국미생물·생명공학회지
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• 제9권3호
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• pp.159-164
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• 1981

부분적 항상성변이주인 Bacillus megaterium (KFCC 10029)가 생산하는 페니실린 아미다제를 예로하여 강화된 $Ca^{++}$-alginate gel에 의한 포괄방법을 이용하는 효소 고정화 방법을 제시하였다. 발효액으로 부터 celite 흡착법에 의해 효소를 분리한 후 alginate의 gellatin용액에 혼합하고 $Ca^{++}$ 용액에서 응고시키고 glutaraldehyde로 처리하여 성형하였다. 이렇게 하여 얻은 고정화효소의 최적 pH 및 온도는 각각 8.0과 6$0^{\circ}C$였다. Km value 와 6-APA 및 페닐초산에 의한 저해 상수는 각각 2.6mM, 7.4mM, 21.2mM이었다. Gel의 증가된 물리적 강도 때문에 반응조 조작중 흡착효소의 유실을 성공적으로 없앨수 있었다. 관형식 반응조에서의 고정화 효소의 반감기는 4$0^{\circ}C$와 3$0^{\circ}C$에서 각각 6일 및 30일이었으며, 이것은 흡착효소와 비교해 볼 때 6-8배의 증가치이다. 결론적으로 alginate gel 포괄방법에 의한 효소고정화 방법에 있어, 본 연구에서 개발된 개량된 방법을 사용함으로써 고정화효소의 물리적 강도 및 안정도를 크게 증가시킬 수 있었다.

• Fisheries and Aquatic Sciences
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• 제17권2호
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• pp.203-207
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• 2014

The present study was conducted to elucidate effects of heat, salt and hydrocolloid treatments on flying fish Cypselurus agoo roe analogs prepared using calcium alginate gel. The changes in size, sphericity and rupture strength of the analogs as affected by treatments of heat, sodium chloride and hydrocolloids were investigated. The size (mm), sphericity (%), and rupture strength (kPa) of the analogs were $2.2{\pm}0.1$, $98.2{\pm}0.2$, and $74.7{\pm}1.7$, respectively. When the analogs were heated at $95^{\circ}C$ in water, the size was slightly decreased. The rupture strength by curing with 2% sodium chloride was slightly increased. Sphericity didn't show significant differences by sodium chloride and heat treatment. The rupture strength of the analogs was slightly decreased by heat treatment, whereas remarkably decreased by curing with sodium chloride. In order to prevent a remarkable decrease in rupture strength of the analogs by curing with sodium chloride, the analogs were treated with hydrocolloids such as xanthan gum, gum guar, glucomannan, pectin and gelatin. The hydrocolloids treated analogs showed an increment in size and no significant changes in sphericity. On the other hand, the rupture strength of the hydrocolloids treated analogs exhibited remarkable increase than that of untreated ones.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2017년도 춘계공동학술대회
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• pp.107-107
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• 2017

3D bioprinting is a technology to produce complex tissue constructs through printing living cells with hydrogel in a layer-by-layer process. To produce more stable 3D cell-laden structures, various materials have been developed such as alginate, fibrin and gelatin. However, most of these hydrogels are chemically bound using crosslinkers which can cause some problems in cytotoxicity and cell viability. On the other hand, thermosensitive hydrogels are physically cross-linked by non-covalent interaction without crosslinker, facilitating stable cytotoxicity and cell viability. The examples of currently reported thermosensitive hydrogels are poly(ethylene glycol)/poly(propylene glycol)/poly(ethylene glycol) (PEG-PPG-PEG) and poly(ethylene glycol)/poly(lactic acid-co-glycolic acid) (PEG/PLGA). Chitosan, which have been widely used in tissue engineering due to its biocompatibility and osteoconductivity, can be used as thermosensitive hydrogels. However, despite the many advantages, chitosan hydrogel has not yet been used as a bioink. The purpose of this study was to develop a bioink by chitosan hydrogel for 3D bioprinting and to evaluate the suitability and potential ability of the developed chitosan hydrogel as a bioink. To prepare the chitosan hydrogel solution, ${\beta}-glycerolphosphate$ solution was added to the chitosan solution at the final pH ranged from 6.9 to 7.1. Gelation time decreased exponentially with increasing temperature. Scanning electron microscopy (SEM) image showed that chitosan hydrogel had irregular porous structure. From the water soluble tetrazolium salt (WST) and live and dead assay data, it was proven that there was no significant cytotoxicity and that cells were well dispersed. The chitosan hydrogel was well printed under temperature-controlled condition, and cells were well laden inside gel. The cytotoxicity of laden cells was evaluated by live and dead assay. In conclusion, chitosan bioink can be a candidate for 3D bioprinting.

• Journal of Microbiology and Biotechnology
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• 제32권2호
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• pp.238-247
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• 2022

Since the skin covers most surfaces of the body, it is susceptible to damage, which can be fatal depending on the degree of injury to the skin because it defends against external attack and protects internal structures. Various types of artificial skin are being studied for transplantation to repair damaged skin, and recently, the production of replaceable skin using three-dimensional (3D) bioprinting technology has also been investigated. In this study, skin tissue was produced using a 3D bioprinter with human skin cell lines and cells extracted from mouse skin, and the printing conditions were optimized. Gelatin was used as a bioink, and fibrinogen and alginate were used for tissue hardening after printing. Printed skin tissue maintained a survival rate of 90% or more when cultured for 14 days. Culture conditions were established using 8 mM calcium chloride treatment and the skin tissue was exposed to air to optimize epidermal cell differentiation. The skin tissue was cultured for 14 days after differentiation induction by this optimized culture method, and immunofluorescent staining was performed using epidermal cell differentiation markers to investigate whether the epidermal cells had differentiated. After differentiation, loricrin, which is normally found in terminally differentiated epidermal cells, was observed in the cells at the tip of the epidermal layer, and cytokeratin 14 was expressed in the lower cells of the epidermis layer. Collectively, this study may provide optimized conditions for bioprinting and keratinization for three-dimensional skin production.

• 청정기술
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• 제29권1호
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• pp.10-21
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• 2023

천연 고분자 이중 네트워크를 기반으로 하는 하이드로젤은 뛰어난 생체 적합성, 낮은 세포 독성, 높은 함수율을 가져 다양한 의학 분야 재료로서 우수한 성능을 가지며 생체 조직 내 표적 약물 전달 시스템에의 응용에도 많은 주목을 받고 있지만 상대적으로 약한 기계적 물성에 의한 한계를 가진다. 본 연구에서는 천연 고분자 산화 알지네이트(alginate di-aldehyde, ADA)와 젤라틴(gelatin)이 형성하는 이중 네트워크 기반의 하이드로젤을 합성하였으며 하이드로젤 내부의 기능기와 수소 결합을 할 수 있는 다량의 수산기(-OH) 기능기를 가지는 과분지 고분자(hyperbranched polyglycerol, HPG)를 0~25%의 범위로 조절하여 첨가하여 최종적으로 기계적 물성이 향상된 천연 고분자 기반 하이드로젤을 합성하였다. 또한, 자철석 나노 입자(Fe₃O₄ nanoparticles (NPs))를 하이드로젤 내부에 in-situ 방법으로 합성하여 자성이 부여된 천연고분자 하이드로젤의 제조 및 특성 분석을 진행하였다. 결과적으로 Fe₃O₄ NPs를 도입한 15% HPG 함량의 하이드로젤은 3.8 emu g^-1의 포화자화 값을 가지는 초상자성을 보였고, 변형률 67.4%에서 최대 압축 강도 1.1 MPa으로 높은 기계적 물성을 가졌다. 향상된 기계적 물성을 가지는 천연 고분자 기반의 초상자성 하이드로젤은 약물 전달 시스템 및 생체 재료에 매우 중요한 잠재적 용도가 있을 것으로 사료된다.

• Journal of Microbiology and Biotechnology
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• 제16권9호
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• pp.1347-1354
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• 2006

The aims of this study were to establish a simple and effective method for isolating male germline stem cells (GSCs), and to test the possibility of using these cells as a new approach for male infertility treatment. Testes obtained from neonatal and adult mice were manually decapsulated. GSCs were collected from seminiferous tubules by a two-step enzyme digestion method and plated on gelatin-coated dishes. Over 5-7 days of culture, GSCs obtained from neonates and adults gave rise to large multicellular colonies that were subsequently grown for 10 passages. During in vitro proliferation, oct-4 and two immunological markers (Integrin ${\beta}1,\;{\alpha}6$) for GSCs were highly expressed in the cell colonies. During another culture period of 6 weeks to differentiate to later stage germ cells, the expression of oct-4 mRNA decreased in GSCs and Sertoli cells encapsulated with calcium alginate, but the expression of c-kit and testis-specific histone protein 2B(TH2B) mRNA as well as the localization of c-kit protein was increased. Expression of transition protein (TP-l) and localization of peanut agglutinin were not seen until 3 weeks after culturing, and appeared by 6 weeks of culture. The putative spermatids derived from GSCs supported embryonic development up to the blastocyst stage with normal chromosomal ploidy after chemical activation. Thus, GSCs isolated from neonatal and adult mouse testes were able to be maintained and proliferated in our simple culture conditions. These GSCs have the potential to differentiate into haploid germ cells during another long-term culture.