• 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 Chest Surgery
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• 제41권2호
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• pp.160-169
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• 2008

배경: 혈관질환의 수술에 사용되는 인공 도관의 막힘과 문합부위의 좁아짐 등을 개선하기 위한 방법으로 조직공학적인 방법과 자가 세포를 이용한 인공혈관의 제작이 대안으로 대두되고 있다. 저자들은, 생흡수성이 있는 고분자 폴리머 지지체와 자가 골수세포를 이용한 인공혈관으로 생체실험을 시행하였다. 대상 및 방법: 생분해성 고분자 재료인 poly (lactide-co-${\varepsilon}$-caprolactone) (PLCL)과 poly(glycolic acid) (PGA) fiber로 혈관용 지지체를 제작한 후, 피실험 동물의 골수를 채취하여 혈관 내피 세포와 평활근 세포로 분열시켜 배양한 후 혈관 지지체위에 이식하였다. 만들어진 인공 혈관을 잡견의 복부대동맥에 이식한 후 3주 후에 혈관 조영술을 시행하고, 안락사 후에 혈관을 제거하여 조직학적 검사를 시행하였다. 결과: 6마리의 잡견 중 2마리에서 수술 후 10일에 혈관 지지체의 균열에 의한 대량 출혈로 사망하였다. 나머지 4마리의 잡견은 수술 후 3주까지 생존하였으며, 혈관 조영술상 혈관의 막힘이나 좁아짐은 발견되지 않았다. 인공 혈관의 내면은 작은 혈전들이 붙어 있었으며, 조직학 검사에서 정상 혈관과 유사한 3층의 구조를 나타내었다. 또한 면역화학 검사에서 혈관 내피세포와 혈관 평활근 세포가 재생된 것을 확인하였다. 결론: 고분자 폴리머와 자가 골수세포를 이용한 인공혈관은 생체 내에서 정상혈관과 유사한 모양으로 재생이 가능함을 보여주었다. 그러나, 동맥압력에 견디기 위해 혈관 지지체의 물성에 대한 개량과 충분한 양의 혈관 세포를 얻기 위한 연구가 더 필요할 것으로 생각된다.

• IMMUNE NETWORK
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• 제22권5호
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• pp.42.1-42.20
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• 2022

Vaccination with tumor peptide epitopes associated with MHC class I molecules is an attractive approach directed at inducing tumor-specific CTLs. However, challenges remain in improving the therapeutic efficacy of peptide epitope vaccines, including the low immunogenicity of peptide epitopes and insufficient stimulation of innate immune components in vivo. To overcome this, we aimed to develop and test an innovative strategy that elicits potent CTL responses against tumor epitopes. The essential feature of this strategy is vaccination using tumor epitope-loaded nanoparticles (NPs) in combination with polyinosinic-polycytidylic acid (poly-IC) and anti-PD1 mAb. Carboxylated NPs were prepared using poly(lactic-co-glycolic acid) and poly(ethylene/maleic anhydride), covalently conjugated with anti-H-2K^b mAbs, and then attached to H-2K^b molecules isolated from the tumor mass (H-2^b). Native peptides associated with the H-2K^b molecules of H-2K^b-attached NPs were exchanged with tumor peptide epitopes. Tumor peptide epitope-loaded NPs efficiently induced tumor-specific CTLs when used to immunize tumor-bearing mice as well as normal mice. This activity of the NPs significantly was increased when co-administered with poly-IC. Accordingly, the NPs exerted significant anti-tumor effects in mice implanted with EG7-OVA thymoma or B16-F10 melanoma, and the anti-tumor activity of the NPs was significantly increased when applied in combination with poly-IC. The most potent anti-tumor activity was observed when the NPs were co-administered with both poly-IC and anti-PD1 mAb. Immunization with tumor epitope-loaded NPs in combination with poly-IC and anti-PD1 mAb in tumor-bearing mice can be a powerful means to induce tumor-specific CTLs with therapeutic anti-tumor activity.

• Journal of Microbiology and Biotechnology
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• 제15권3호
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• pp.510-518
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• 2005

In this study, we investigated whether PLGA microspheres in combination with hyaluronic acid (HA) gel have appropriate properties as a bulking agent for urologic injection therapies and whether the implantation of PLGA microspheres and HA gel induces angiogenesis in the newly formed tissues. In order to investigate whether this bulking agent is injectable, this material was injected through 24-gauge needles into the subcutaneous dorsum of the mouse. The bulking agent was easily injected without needle obstruction. Histological analyses of the hybrid tissues at 2 weeks showed that host cells at the surrounding tissues migrated into the spaces between the implanted PLGA microspheres and formed tissue-like structures. An inflammatory response to the implants was mild at 2 weeks and diminished at 8 weeks. Importantly, extensive ingrowth of blood vessels was observed in the hybrid tissues formed by the injection of PLGA microspheres and HA, whereas blood vessels rarely formed in the hybrid tissues formed by the injection of PLGA microspheres only. The implant volume was conserved for almost the entire implantation period. Histological analyses of the distant organs of the bulking agent-implanted animals, such as the lungs, liver, heart, brain, kidney, and spleen, showed no evidence of the injected microsphere migration. These results show that PLGA microspheres in combination with HA possess the appropriate characteristics for a bulking agent for urologic injection therapies and induce extensive blood vessel formation in the hybrid tissues.

• 폴리머
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• 제34권5호
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• pp.474-479
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• 2010

조직공학에 이용되는 고분자인 poly(lactic-co-glycolic acid)(PLGA)는 높은 생체적합성 및 생분해성의 장점을 지니지만, 생체활성물질의 결여와 소수성으로 인해 세포의 부착에 어려움을 가진다. 또한 PLGA의 가수분해 과정 중 생성되는 산 분해물이 조직주변의 pH를 감소시켜 염증을 유발하는 단점을 가지고 있다. 따라서 이러한 단점을 보완하기 위한 방법으로 천연고분자인 케라틴을 첨가한 PLGA필름을 제작하였으며 조직공학적 디스크재생에 응용하기 위하여 케라틴/PLGA 복합체필름의 원통형 지지체를 제작하였다. 이 원통형 지지체의 내부는 케라틴/PLGA 필름을 말아서 사용하였으며 외부는 PLGA 다공성 지지체 링을 제작하여 사용하였다. 본 연구에서는 이 지지체에 섬유륜세포를 파종하여 PLGA 필름과 케라틴/PLGA 필름을 이용한 원통형 지지체에서의 세포의 부착 및 생존율을 비교하고 케라틴을 첨가한 지지체의 우수성을 확인하였으며 강도의 우수성 또한 확인하였다. 이 결과는 디스크재생을 위한 지지체의 연구에 유용한 정보를 제공할 것이다.

• Journal of Periodontal and Implant Science
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• 제50권5호
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• pp.327-339
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• 2020

Purpose: The purpose of this study was to examine the local tissue reactions associated with 3 different poly(lactic-co-glycolic acid) (PLGA) prototype membranes and to compare them to the reactions associated with commercially available resorbable membranes in rats. Methods: Seven different membranes-3 synthetic PLGA prototypes (T1, T2, and T3) and 4 commercially available membranes (a PLGA membrane, a poly[lactic acid] membrane, a native collagen membrane, and a cross-linked collagen membrane)-were randomly inserted into 6 unconnected subcutaneous pouches in the backs of 42 rats. The animals were sacrificed at 4, 13, and 26 weeks. Descriptive histologic and histomorphometric assessments were performed to evaluate membrane degradation, visibility, tissue integration, tissue ingrowth, neovascularization, encapsulation, and inflammation. Means and standard deviations were calculated. Results: The histological analysis revealed complete integration and tissue ingrowth of PLGA prototype T1 at 26 weeks. In contrast, the T2 and T3 prototypes displayed slight to moderate integration and tissue ingrowth regardless of time point. The degradation patterns of the 3 synthetic prototypes were similar at 4 and 13 weeks, but differed at 26 weeks. T1 showed marked degradation at 26 weeks, whereas T2 and T3 displayed moderate degradation. Inflammatory cells were present in all 3 prototype membranes at all time points, and these membranes did not meaningfully differ from commercially available membranes with regard to the extent of inflammatory cell infiltration. Conclusions: The 3 PLGA prototypes, particularly T1, induced favorable tissue integration, exhibited a similar degradation rate to native collagen membranes, and elicited a similar inflammatory response to commercially available non-cross-linked resorbable membranes. The intensity of inflammation associated with degradable dental membranes appears to relate to their degradation kinetics, irrespective of their material composition.

• Journal of Microbiology and Biotechnology
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• 제19권11호
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• pp.1490-1495
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• 2009

The development of nanotechnology has penetrated the fields of biology and medicine, resulting in remarkable applications for tissue regeneration. In order to apply this technology to tissue engineering, we have developed nano-scaled 3D scaffolds consisting of growth factor-loaded heparin/poly(l-lysine) nanoparticles (NPs) attached to the surface of polymeric micro spheres via polyionic complex methods. Growth factor-loaded NPs were simply produced as polyelectrolyte complexes with diameters of 100-200 nm. They were then coated onto positively charged poly(lactic-co-glycolic acid) (PLGA) pretreated with polyethyleneimine to enable cell adhesion, proliferation, and stimulation of neurite outgrowth. Propidium iodide staining and $\beta$-tubulin analysis revealed that neuronal PC12 cells proliferated extensively, expressed significant amounts of b-tubulin, and showed well-structured neurite outgrowth on polymeric microspheres by stimulation with growth factors. These results suggest that cellular adhesion and biological functionality on prepared PLGA microspheres enabled terminal differentiation of neuronal cells.

• Bulletin of the Korean Chemical Society
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• 제30권9호
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• pp.1985-1988
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• 2009

Poly (lactic-co-glycolic acid) (PLGA) nanoparticles loading paclitaxel have been deposited on coronary stents by self-assembling properties of colloidal particles. The layers of the nanoparticles were enhanced to a sufficient mechanical strength by a thermal process under the proper temperature and humidity conditions. In vitro release studies proved the controlled paclitaxel release of the nanoparticle layers. This technique gives rise to a new range of applications for nanoparticles and drug-eluting stents.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 춘계학술발표대회
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• pp.541-545
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• 2000

For the sustained release formulation of recombinant human growth hormone (rhGH), dissociable rhGH aggregates were microencapsulated within poly(D,L-lactic-co-glycolic acid) [PLGA] microparticles. rhGH aggregates with 2 - 3 m Particle diameter were first produced by adding a small volume of aqueous rhGH solution into a partially water miscible organic solvent phase(ethyl acetate) containing PLGA. These rhGH aggregates were then microencapsulated within PLGA polymer phase by extracting ethyl acetate into an aqueous phase pre-saturated with ethyl acetate. The resultant microparticles were 2 - 3 m in diameter similar to the size of rhGH aggregates, suggesting that PLGA polymer was coated around the protein aggregates. Release profiles of rhGH from these microparticles were greatly affected by changing the volume of the incubation medium. The release rhGH species consisted of mostly monomeric form with having a correct conformation. This study reveals that sustained rhGH release could be achieved by microencapsulating reversibly dissociable protein aggregates within biodegradable polymers.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.591-594
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• 2003

기존 재료들의 단점인 재료의 전이성, 염증 유발, 효과의 단기 지속 등의 문제를 해결하기 위하여 PLGA 미립구를 주 재료로 하는 주사 충전재를 개발하였다. 생쥐 실험 결과 염증 반응이 적고 장기 이동성이 없으며 부피 유지 효과가 우수하다는 결론을 내렸으며 추가적으로 장기 추가 보완 실험을 실시하여 비뇨기과, 성형외과적 주사용 충전재로써의 적합성을 조사하겠다.