• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.154-157
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• 2002

A cyto-indentation technique was used to obtain the biomechanical compressive compliance property of an chondrocyte cell attached to glass surface, which was tried to generate joint cartilage by tissue engineering. Piezo-transducer system and dual photo-diode system were used to conduct mechanical indentation through displacement-controlled testing and the measurement of corresponding cell reaction force. The Poisson's ratio of 0.37 was quoted from other report. The compressive compliance of chondrocyte, that was determined by elastic contact theory, was 1.38${\pm}$0.057 kPa. This value is 30% higher than that of MG63 osteoblast-like cell. The cyto-indentation technique employed in this study is so precise that it can quantify the biomechanical property of single cell.

• Journal of Chest Surgery
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• 제37권6호
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• pp.474-481
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• 2004

배경: 암이나 협착 등의 각종 기관질환으로 광범위한 기관절제가 필요한 경우에는 기관 이식이 필요하나, 다른 장기의 이식술과 비교하여 많은 어려움이 있다. 이에 본 연구에서는 이상적인 기관 대체물을 개발하기 위한 노력의 일환으로, 조직 공학적 기법을 통하여 기관 재건에 적용할 수 있는 소장-연골 복합 이식판의 개발이 가능한가를 알아보고자 하였다. 대상 및 방법: 생후 2주 된 토끼의 기관과 이개로부터 각각 연골세포를 채취하여 8주간 배양하였다. 배양된 초자 연골세포와 탄성 연골세포를 담체(PLGA)에 심거나 플루로닉 겔에 혼합한 후에, 4 종류의 혼합체를 토끼의 위장과 대장의 점막하 조직에 이식하고 10주 후에 연골 형성 여부를 평가하였다. 결과: 육안과 촉진으로 이식 부위를 판별할 수 있었으며, 현미경적 소견상 담체의 흡수와 연골의 형성을 확인할 수 있었다. 특히 초자 연골세포-담체 혼합체에서 연골의 형태를 잘 갖추고 있었다. 결론: 장-연골 복합 이식판 개발의 전망은 밝으며, 이상적인 기관 대체물로서 기관 재건에 기여할 가능성이 있다고 사료된다.

• 폴리머
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• 제37권2호
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• pp.141-147
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• 2013

Poly(lactide-co-glycolic acid)(PLGA)는 좋은 기계적 성질과 생분해성으로 약물전달시스템 또는 조직공학적으로 널리 이용되고 있으나 낮은 세포 부착률을 가지고 있어 피브린을 첨가하여 이를 보완하고자 하였다. 본 연구에서 사용된 지지체는 트롬빈과 피브리노겐, 그리고 세포을 혼합시킨 후 PLGA 지지체 위에 도포시켜 제조하였다. 세포의 부착 및 증식률을 측정하고자 PLGA/피브린 지지체에 늑연골 세포를 파종 후 1, 3일 및 7일 후 SEM과 MTT 분석을 통하여 측정하였으며, 세포외기질 형성에 미치는 피브린의 영향을 확인하고자 세포를 파종 후 누드마우스에 이식하여 GAG 및 콜라겐 합성의 효과를 확인하였다. 따라서 본 연구에서는 피브린이 혼합된 PLGA 지지체가 생체 내 외 환경에서 세포의 부착 및 증식에 미치는 영향을 확인하고자 연구를 진행하였다. 그 결과, PLGA/피브린 지지체가 기존의 PLGA 지지체와 비교하여 탁월한 세포 성장률을 나타내는 것으로 확인하였다.

• 한국정밀공학회지
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• 제26권7호
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• pp.38-43
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• 2009

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1265-1270
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• 2007

Conventional methods for fabricating three-dimensional (3-D) scaffolds have substantial limitations. In this paper, we present 3-D scaffolds that can be made repeatedly with the same dimensions using a microstereolithography system. This system allows the fabrication of a pre-designed internal structure, such as pore size and porosity, by stacking photopolymerized materials. The scaffolds must be manufactured in a material that is biocompatible and biodegradable. In this regard, we synthesized liquid photocurable biodegradable TMC/TMP, followed by acrylation at terminal ends. And also, solidification properties of TMC/TMP polymer are to be obtained through experiments. Cell adhesion to scaffolds significantly affects tissue regeneration. As a typical example, we seeded chondrocytes on two types of 3-D scaffold and compared the adhesion results. Based on these results, the scaffold geometry is one of the most important factors in chondrocyte adhesion. These 3-D scaffolds could be key factors for studying cell behavior in complex environments and eventually lead to the optimum design of scaffolds for the regeneration of various tissues, such as cartilage and bone.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.155.1-155.1
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• 2005

• Macromolecular Research
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• 제16권6호
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• pp.517-523
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• 2008

A RGD (Arg-Gly-Asp) conjugated chitosan hydrogel was used as a cell-supporting scaffold for articular cartilage regeneration. Thermosensitive chitosan-Pluronic (CP) has potential biomedical applications on account of its biocompatibility and injectability. A RGD-conjugated CP (RGD-CP) copolymer was prepared by coupling the carboxyl group in the peptide with the residual amine group in the CP copolymer. The chemical structure of RGD-CP was characterized by $^1H$ NMR and FT IR. The concentration of conjugated RGD was quantified by amino acid analysis (AAA) and rheology of the RGD-CP hydrogel was investigated. The amount of bound RGD was $0.135{\mu}g$ per 1 mg of CP copolymer. The viscoelastic parameters of RGD-CP hydrogel showed thermo-sensitivity and suitable mechanical strength at body temperature for cell scaffolds (a> 100 kPa storage modulus). The viability of the bovine chondrocyte and the amount of synthesized glycosaminoglycans (GAGs) on the RGD-CP hydrogels were evaluated together with the alginate hydrogels as a control over a 14 day period. Both results showed that the RGD-CP hydrogel was superior to the alginate hydrogel. These results show that conjugating RGD to CP hydro gels improves cell viability and proliferation, including extra cellular matrix (ECM) expression. Therefore, RGD conjugated CP hydrogels are quite suitable for a chondrocyte culture and have potential applications to the tissue engineering of articular cartilage tissue.

• 대한의용생체공학회:의공학회지
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• 제23권2호
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• pp.147-153
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• 2002

본 연구에서는 관상의 Poly(lactic-co-glycolic acid) (PLGA) 담체에 대한 인간의 초자연골과 탄성연골의 형성정도를 살펴보았다. 담체는 PLGA의 분자량에 따라서는 110,000 g/mol과 220,000 g/mol을 비교하였고 내경 유지를 위하여 내경측에는 220,000 g/mol, 외경측에는 110,000 g/mol 의 복합체를 만들거나, 비분해성 고분자 폴리에틸렌 튜브와 110,000 g/mol PLGA의 담체와의 결합도 시도하였다. PLGA 담체들은 주사전자현미경으로 단면 구조를 관찰하였다. 각각의 담체에 20세 미만의 환자들의 비중격에서 채취된 초자연골과 귀에서 채취된 탄성연골에서 분리한 연골세포를 심었다. 분리된 연골세포는 두 번의 계대배양을 거쳐 각각의 PLGA 담체에 심었고 일주일동안 생체 외 환경에서 배양하였다. 각각의 세포와 담체의 복합체를 nude mouse의 배부 좌, 우로 피하조직에 이식하고 8주 뒤 H&E 염색으로 조직 검사를 시행하였다. 110,000 g/mol의 PLGA담체의 연골조직은 잘 형성되어 있었지만 그 내경은 유지되지 못하였다. 반면 220,000 g/mol의 PLGA담체의 연골조직은 내경은 유지하였으나 연골조직이 부분적으로 형성되어 있고 성숙한 연골조직의 양이 많지 않았다. 초자연골 세포에 비교하여 탄성연골 세포가 같은 조건하에서 연골조직을 더 많이 형성한 것으로 나타났다. 관상의 유지를 위하여 220,000 9/mol PLGA 담체를 내경측에 110,000 g/mol PLGA 담체를 외경측으로 한 담체에서는 연골조직 형성이 잘 되지 않았으나 내경측에 폴리에틸렌 튜브를 끼운 110,000 g/mol PLGA 담체에서는 조직 형성과 내경유지가 잘 되었고 원래의 담체와 거의 유사한 형태로 유지되었다. 분화된 연골세포도 조직 소견으로 확인할 수 있었다. 이 1mm 내경의 관상 연골조직은 인공 기관지나 식도 등을 위한 동물 실험과 인공 합성 튜브의 대체 등 앞으로 많은 응용분야가 기대된다.

• Advances in biomechanics and applications
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• 제1권3호
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• pp.169-185
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• 2014

Computational multibody models of the elbow can provide a versatile tool to study joint mechanics, cartilage loading, ligament function and the effects of joint trauma and orthopaedic repair. An efficiently developed computational model can assist surgeons and other investigators in the design and evaluation of treatments for elbow injuries, and contribute to improvements in patient care. The purpose of this study was to develop an anatomically correct elbow joint model and validate the model against experimental data. The elbow model was constrained by multiple bundles of non-linear ligaments, three-dimensional deformable contacts between articulating geometries, and applied external loads. The developed anatomical computational models of the joint can then be incorporated into neuro-musculoskeletal models within a multibody framework. In the approach presented here, volume images of two cadaver elbows were generated by computed tomography (CT) and one elbow by magnetic resonance imaging (MRI) to construct the three-dimensional bone geometries for the model. The ligaments and triceps tendon were represented with non-linear spring-damper elements as a function of stiffness, ligament length and ligament zero-load length. Articular cartilage was represented as uniform thickness solids that allowed prediction of compliant contact forces. As a final step, the subject specific model was validated by comparing predicted kinematics and triceps tendon forces to experimentally obtained data of the identically loaded cadaver elbow. The maximum root mean square (RMS) error between the predicted and measured kinematics during the complete testing cycle was 4.9 mm medial-lateral translational of the radius relative to the humerus (for Specimen 2 in this study) and 5.30 internal-external rotation of the radius relative to the humerus (for Specimen 3 in this study). The maximum RMS error for triceps tendon force was 7.6 N (for Specimen 3).

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 춘계학술대회
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• pp.27-33
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• 1995

A time-dependent large deformation fracture theory is developed for application to soft biological tissues. The theory uses the quasilinear viscoelastic theory of Fung, and particularizes it to constitutive assumptions on polyvinyl-chloride (PVC) (Part I) and cartilage (Part II). This constitutive theory is used in a general viscoelastic theory by Christensen and Naghdi and an energy balance to develop an expression for the fracture toughness of the materials. Experimental methods are developed for measuring the required constitutive parameters and fracture data for the materials. Elastic stress and reduced relaxation functions were determined using tensile and shear tests at high loading rates with rise times of 25-30 msec, and test times of 150 sec. The developed method was validated, using an engineering material, PVC to separate the error in the testing method from the inherent variation of the biological tissues. It was found that the the proposed constitutive modeling can predict the nonlinear stress-strain and the time-dependent behavior of the material. As an approximation method, a pseudo-elastic theory using the J-integral concept, assuming that the material is a time-independent large deformation elastic material, was also developed and compared with the time-dependent fracture theory. For PVC. the predicted fracture toughness is $1.2{\pm}0.41$ and $1.5{\pm}0.23\;kN/m$ for the time-dependent theory and the pseudo-elastic theory, respectively. The methods should be of value in quantifying fracture properties of soft biological tissues. In Part II, an application of the developed method to a biological soft tissue was made by using bovine humeral articular cartilage.