• Archives of Plastic Surgery
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• 제34권2호
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• pp.141-148
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• 2007

Purpose: The object of this study was to evaluate the development of continuous osteogenic differentiation and bone formation after the subcutaneous implantation of the tissue-engineered bone, in vitro. Methods: Human adipose-derived stem cells were obtained by proteolytic digestion of liposuction aspirates. Adipose-derived stem cells were seeded in PLGA scaffolds after being labeled with PKH26 and cultured in osteogenic differentiation media for 1 month. The PLGA scaffolds with osteogenic stimulated adipose-derived stem cells were implanted in subcutaneous layer of four nude mice. Osteogenesis was assessed by RT-PCR for mRNA of osteopontin and bone sialoprotein(BSP), and immunohistochemistry for osteocalcin, and von Kossa staining for calcification of extracellular matrix at 1 and 2 months. Results: Implanted PLGA scaffold with adipose-derived stem cells were well vascularized, and PLGA scaffolds degraded and were substituted by host tissues. The mRNA of osteopontin and BSP was detected by RT-PCR in both osteogenic stimulation group and also osteocalcin was detected by immunohistochemistry at osteogenic stimulation 1 and 2 months, but no calcified extracellular deposit in von Kossa stain was found in all groups. Conclusion: In vivo, it could also maintain the characteristics of osteogenic differentiation that adipose-derived stem cells within PLGA scaffold after stimulation of osteogenic differentiation in vitro, but there were not normal bone formation in subcutaneous area. Another important factor to consider is in vivo, heterologous environment would have negative effect on bone formation as.[p1]

• Macromolecular Research
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• 제14권5호
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• pp.510-516
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• 2006

Lactide was produced from oligomeric PLA by back-biting reaction of the OH end groups. For optimization of the reaction conditions, the effects of temperature, pressure, PLA molecular weight, and catalyst type on the lactide synthesis were examined. The fraction of D,L-lactide decreased with increasing temperature. Among the various Sn-based catalysts, the D,L-lactide fraction was maximized when SnO was used. A higher yield with lower racemization was observed at lower pressure. The conversion of PLA was maximized at an oligomeric PLA molecular weight of ca. 1380. The yield of lactide increased but the fraction of D,L-lactide decreased with increasing molecular weight. The highest conversion with the lowest racemization degree was obtained at a catalyst concentration of 0.1 wt%. The lactide was more sensitive to racemization because of the entropic effect.

• Journal of Pharmaceutical Investigation
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• 제40권4호
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• pp.245-250
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• 2010

Porous poly(lactic-co-glycolic acid) microspheres (PLGA MS) have been utilized as an inhalation delivery system and a matrix scaffold system for tissue engineering. Here, gelatin (type A) is introduced as an extractable pH-responsive porogen, which is capable of controlling the porosity and pore size of PLGA microspheres. Porous PLGA microspheres were prepared by a water-in-oil-in-water ($w_1/o/w_2$) double emulsification/solvent evaporation method. The surface morphology of these microspheres was examined by varying pH (2.0~11.0) of water phases, using scanning electron microscopy (SEM). Also, their porosity and pore size were monitored by altering acidification time (1~5 h) using a phosphoric acid solution. Results showed that the pore-forming capability of gelatin was optimized at pH 5.0, and that the surface pore-formation was not significantly observed at pHs of < 4.0 or > 8.0. This was attributable to the balance between gel-formation by electrostatic repulsion and dissolution of gelatin. The appropriate time-selection between PLGA hardening and gelatin-washing out was considered as a second significant factor to control the porosity. Delaying the acidification time to ~5 h after emulsification was clearly effective to make pores in the microspheres. This finding suggests that the porosity and pore size of porous microspheres using gelatin can be significantly controlled depending on water phase pH and gelatin-removal time. The results obtained in this study would provide valuable pharmaceutical information to prepare porous PLGA MS, which is required to control the porosity.

• 한국건설순환자원학회논문집
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• 제8권2호
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• pp.204-211
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• 2020

PLA(Poly-Lactic Acid)섬유는 친환경소재이며 자연분해가 되므로 건설재료에 사용할 경우 내부 공극연결구조를 가진 다공성 재료의 제조가 가능하다. 본 연구에서는 국내에서 생산된 PLA 섬유(직경 0.5mm, 1.0mm, 길이 10mm)를 대상으로 강알칼리와 고온에서의 용해실험을 수행하였으며, 이를 이용하여 FA기반 지오폴리머에 활용하였다. 고온양생과 강알칼리 용액을 통하여 강도는 확보하였으나, 완전한 PLA 섬유의 용해을 확보하지 못하였다. 기존의 연구인 0.003mm의 직경에서는 완전히 용해하였으나 0.5mm는 약 42.5%, 1.0mm는 약 33.3%의 용해율을 가지고 있는 것으로 평가되었다. 또한 섬유의 체적이 커짐에 따라 양생시 부유하는 섬유가 발생하여 작업성과 용해에 부정적인 영향을 나타내었다. PLA 특성은 생산하는 원재료와 생산조건에 따라 달라질 수 있으나, 다공성 건설 자재로서 사용하기 위해서는 0.1mm 내외의 PLA 섬유의 사용이 바람직하다고 판단된다.

• 한국임상수의학회지
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• 제24권2호
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• pp.182-191
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• 2007

Bioabsorbable devices have been utilized and experimented in many aspects of orthopaedic surgery. Depending upon their constituent polymers, these materials can be tailored to provide sufficient rigidity to allow bone healing, retain mechanical strength for certain period of time, and then eventually begin to undergo degradation. The objective of this study was to estimate extent in which Poly-L-latic acid (PLLA) implants had bioabsorbability and biocompatibility with bone and soft tissue in dogs and also to develop bioabsorbable, biocompatible materials with the appropriate strength and degradation characteristics to allow for regular clinical use for treating orthopedic problems in humans as well as animals. Eighteen dogs were used as experimental animals and were inserted two types of PLLA implants. PLLA rods were inserted into subcutaneous tissue of back or the abdomen wall. And the rods were tested for material properties including viscosity, molecular weight, melting point, melting temperature, crystallinity, flexural strength, and flexural modulus over time. PLLA screws were inserted through cortical bone into bone marrow in the femur of the dogs and stainless steel screw was inserted in the same femur. Radiographs were taken after surgery to observe locations of screw. Histological variations including cortical bone response, muscular response, bone marrow response were analyzed over the time for 62weeks. The physical properties of PLLA rods had delicate balances between mechanical, thermal and viscoelastic factors. PLLA screws did not induce any harmful effects and clinical complications on bone and soft tissue for degradation period. These results suggest that PLLA implants could be suitable for clinical use.

• Bulletin of the Korean Chemical Society
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• 제33권5호
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• pp.1638-1642
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• 2012

A series of poly (lactic acid) (PLA) and poly (ethylene glycol) (PEG) tri and multiblock copolymers with relatively high molecular weights were synthesized through the coupling reaction between the bis(acyl chloride) of carboxylated PLA and mono or dihydroxy PEG. The coupling reaction and the copolymer structures were monitored by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The melting temperature (Tm) of PEG blocks decreased with the presence of PLA sequences attaching to PEG blocks. The CMC values were determined to be 10-145 mg/L depending on the length of PLA and PEG blocks and the structure of the block copolymers.

• Journal of Microbiology and Biotechnology
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• 제22권1호
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• pp.92-99
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• 2012

The optimal physical factors affecting enzyme production in an airlift fermenter have not been studied so far. Therefore, the physical parameters such as aeration rate, pH, and temperature affecting PLA-degrading enzyme production by Actinomadura keratinilytica strain T16-1 in a 3 l airlift fermenter were investigated. The response surface methodology (RSM) was used to optimize PLA-degrading enzyme production by implementing the central composite design. The optimal conditions for higher production of PLA-degrading enzyme were aeration rate of 0.43 vvm, pH of 6.85, and temperature at $46^{\circ}C$. Under these conditions, the model predicted a PLA-degrading activity of 254 U/ml. Verification of the optimization showed that PLA-degrading enzyme production of 257 U/ml was observed after 3 days cultivation under the optimal conditions in a 3 l airlift fermenter. The production under the optimized condition in the airlift fermenter was higher than un-optimized condition by 1.7 folds and 12 folds with un-optimized medium or condition in shake flasks. This is the first report on the optimization of environmental conditions for improvement of PLA-degrading enzyme production in a 3 l airlift fermenter by using a statistical analysis method. Moreover, the crude PLA-degrading enzyme could be adsorbed to the substrate and degraded PLA powder to produce lactic acid as degradation products. Therefore, this incident indicates that PLA-degrading enzyme produced by Actinomadura keratinilytica NBRC 104111 strain T16-1 has a potential to degrade PLA to lactic acid as a monomer and can be used for the recycle of PLA polymer.

• 폴리머
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• 제30권2호
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• pp.168-174
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• 2006

기존의 고분자 지지체의 소수성 및 세포친화성을 향상시켜 조직공학용 고기능성 지지체로 사용하기 위해서 여러 가지 플라스마 처리와 카복실기를 함유한 아크릴산(AA)을 직접 chamber내에서 in situ 그래프트 결합을 행하여 최적의 친수성을 갖는 생분해성 poly(L-lactic acid) (PLLA) 필름 및 이중기공 지지체를 제조하였다. 표면분석 결과, 표면개질된 비다공성 PLLA 필름 및 이중기공 지지체 표면은 미처리 PLLA control에 비해서 접촉각의 감소와 카복실기 함량의 증가로 친수성이 크게 증가하였다. 특히 여러 가지 표면개질 방법 중 Ar(아르곤)/AA 시료나 Ar+TP(열중합) 시료보다는 Ar 플라스마와 AA를 차례로 처리한 Ar+AA+AA 시료가 다른 시료들보다 접촉각이 낮고 카복실기가 많아서 최적의 표면 친수화 처리조건임을 알 수 있었으며, 표면개질된 PLLA 필름 및 이중기공 지지체의 경우 친수성이 증가함에 따라서 연골세포의 점착과 증식도 크게 향상되었다.

• 한국발생생물학회지:발생과생식
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• 제15권2호
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• pp.87-98
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• 2011

본 실험은 bioceramic을 첨가하여 만든 다공성 poly D,L-lactic-co-glycolic acid(PLGA)-scaffold가 인간 지방조직에서 유래된 중간엽 줄기세포(human adipose tissue derived mesenchymal stem cells, ATMSCs)의 골 형성과정에 효과적인지를 알아보고자 수행하였다. ATMSCs를 well plate에 접종하여 골형성 유도(osteogenic induction, OI) 배양액으로 28일 동안 배양하였다. OI배양액군의 증식률은 세포접종 후 14일까지는 세포증식이 활발하게 진행됐지만, 21일 이후 세포의증식이 둔화되는 양상을 보였다. 반면, 기본배양액군은 꾸준한 세포 증식을 보이며 21일 이후에는 OI배양액군보다 더 높은 증식을 나타냈다. OI배양액군의 alkaline phosphatase(ALP) 활성은 세포배양 21일까지는 증가했지만, 28일에는 감소한 반면에 기본배양액군은 계속 감소하는 양상을 띠었다. OI배양액군의 세포는 배양 21일에는 뚜렷한nodule의 형성을 관찰할 수 있었고, nodule에 칼슘의 축적이 일어남을 확인하였다. ATMSCs를 scaffold에 접종하여 OI배양액으로 배양하였다. Scaffold 내 골아세포 분화에 따른 ALP 활성은 PLGA scaffold와 Bioceramic-PLGA scaffold 모두에서 세포 배양 21일에 급격히 증가하였고, Bioceramic-PLGA scaffold의 ALP 활성이 PLGA scaffold보다 크게 증가하였다. 칼슘과 인의 함량 역시 Bioceramic-PLGA scaffold에서 높게 나타났으며, Bioceramic-PLGA scaffold의 Ca/P ratio가 PLGA scaffold보다 높게 나타났다. 생체내에 이식된 scaffold의 생분해성과 광물화는 bioceramic-PLGA scaffold에서 더욱 뚜렷하게 관찰되었다. 본 실험의 결과들을 종합해 볼 때 ATMSCs의 골형성능은 well plate보다 scaffold가 더 효과적이며, bioceramic이 scaffold의 세포 부착률과 ALP 활성을 증가시켜 골형성능에 효과적으로 작용하는 것으로 생각된다. 또한 bioceramic이 ATMSCs의 골형성 분화에 따른 광물화단계의 scaffold 내 칼슘과 인의 함량을 증가시키는 것으로 사료된다.생체 내 scaffold의 생분해성은 PLGA scaffold보다 Bioceramic-PLGA scaffold가 빠른 분해를 나타내며, 광물화에 따른 칼슘 침착이 더 활발한 것은 scaffold에 포함된 bioceramic이 생체 내 세포의 부착, 증식, 분화를 증가시켜 골형성을 촉진시키는 물질로 작용한 것으로 사료된다.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.181-181
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• 2006

We developed a novel method to fabricate a nerve guide conduit (NGC) with the porosity of submicron pore sizes (to prevent fibrous tissue infiltration) and hydrophilicity (for effective oxygen and nutrient permeation) using poly(lactic-co-glycolic acid) (PLGA) and Pluronic F127 by a modified immersion precipitation method designed by our laboratory. It was recognized that the hydrophilized PLGA/F127 (3 wt%) tube can be a good candidate as a NGC from the analyses of its morphology, mechanical strength, hydrophilicity, model nutrient permeability and in vivo nerve regeneration behavior using a rat model.