• Proceedings of the KOSOMBE Conference
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• v.1991 no.11
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• pp.101-102
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• 1991

• Proceedings of the KOSOMBE Conference
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• v.1993 no.05
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• pp.139-140
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• 1993

• Journal of Biomedical Engineering Research
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• v.20 no.6
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• pp.547-553
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• 1999

생체재료로 사용되는 polyurethane(PU) 표면에 항혈전성 lumbrokinase(LK)를 고정함으로써 생체적합성을 향상시키고자하였다. 먼저 LK를 PU 표면에 고정하기 위한 가교제로서 4-azidoaniline hydrochloride와 poly(acrylic acid)를 이용하여 4-azidophenyl 작용기가 amido 결합으로 치환된 수용성, 광반응성 poly(acrylic acid)(PPa-II)를 합성하였다. H-nuclear magnetic reasonance spectrum(500MHz H-NMR)의 6-7 peak와 infrared spectrum (FT-IR) 의 2125.48 cm peak으로부터 PPA-II의 합성을 지원하였다. EH한 4-azidophenyl 작용기가 poly(acrylid acid) 잔기에 치환된 정도는 UV/VIS adpectrophotometric spectrum을 확인한 결과 11~14%임을 알 수있었다. 0.5 1및 5% PPA-II를 각각 광반응하여 얻은 PU는 39.5, 161.8 및 181.5 nmole/$\textrm{cm}^2$의 농도로 표면에 carvoxyl 작용기가 유도되었음을 알 수있었다. 0.05M KH2PO4 (pH 4.5) 용액에서 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide(EDC)를 촉매로 사용하여 LK를 PU표면에 amido 공유결합으로 고정하였으며, 이것은 지속적인 fibrinolytic 활성도를 보였다. PPA-II를 이용한 표면 개질 방법은 수용성 반응조건에서 이루어진다는 점과 광반응을 이용함으로써 특정부위에서의 표면개질이 가능하다는 점에서 그 응용가치가 크며 아울러 PU의 생체적합성을 향상시킬 수 있는 방법으로서 판단된다.

• Proceedings of the KOSOMBE Conference
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• v.1994 no.05
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• pp.136-138
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• 1994

• Journal of Biomedical Engineering Research
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• v.8 no.2
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• pp.161-170
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• 1987

A new type of motor-driven total artificial heart system with a rolloing-cylinder mechanism has been developed. The prototype system consists of a brushless DC motor inside of a rolling-cylinder, two arc shaped pusher-plate s, and two ventricles of smooth, seamless polyurethane sacs. The motor-driven pump has the advantages of being portable and quiet compared to the present air-driven pump. It can also be controlled more accurately. This rolling-cylinder type electromechanical pump has several structural advantages including small size and weight, as compared to other research groups' motor-driven pumps. The results of mock circulation tests confirm sufficient pump output capacity(cardiac output . 9 L/min, at aortic pressure'120mmHg, with heart rate . 120 BPM) for animal implantation of our prototype system.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.335-336
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• 1996

Flexible, self-expanding metallic stent were developed using igzag wire bend and segmented polyurethane. Mechanical properties of these stents were tested using INSTRON. These stents were used for palliative treatment of mallignant esophagogastric strictures(3 case) and bawl preparation of collorectal obstruction(10 case). All stents were inserted with fluoroscopic guidance without techinal failures. According to the results, these stents are easy to insert, safe, and very effective for dilation of strictures in curved GI tract.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.227-228
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• 1998

Lumbrokinase, potent fibrinolytic enzyme purified from earthworm, was immobilized onto polyurethane valves using photoreaction, photoreactive polyallyl-amino as a photoreactive linker. For evaluation of blood compatibility, lumbrokinase immobilized polymer valves were assembled into the total artificial heart (TAH). This TAH was implanted to 60kg healthy lamb for 1-3 days with the cardiac output 5 L/min. In the control lamb, the valves were untreated, in ore other, only valves on the right were treated, and in the remaining animal, only those on the left. To facilitate the thrombus formation, low doses of heparin were administered. For evaluation of the immobilized lumbrokinase, thrombus formation, proteolytic and fibrinolytic activity was measured. This data shows that lumbrokinase-treated polyurethane valves lead to decreased thrombus formation in vivo, and that their biocompatibility is therefore higher than that of untreated valves.

• Advances in nano research
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• v.10 no.1
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• pp.59-69
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• 2021

Electrospinning is a cost-effective and versatile method for producing submicron fibers. Although this method is relatively simple, at the theoretical level the interactions between process parameters and their influence on the fiber morphology are not yet fully understood. In this paper, the aim was finding optimal electrospinning parameters in order to obtain the smallest fiber diameter by using Taguchi's methodology. The nanofibers produced by electrospinning a solution of Thermoplastic Polyurethane (TPU) in Dimethylformamide (DMF). Polymer concentration and process parameters were considered as the effective factors. Taguchi's L9 orthogonal design (4 parameters, 3 levels) was applied to the experiential design. Optimal electrospinning conditions were determined using the signal-to-noise (S/N) ratio with Minitab 17 software. The morphology of the nanofibers was studied by a Scanning Electron Microscope (SEM). Thereafter, a tensile tester machine was used to assess mechanical properties of nanofibrous scaffolds. The analysis of DoE experiments showed that TPU concentration was the most significant parameter. An optimum combination to reach smallest diameters was yielded at 12 wt% polymer concentration, 16 kV of the supply voltage, 0.1 ml/h feed rate and 15 cm tip-to-distance. An empirical model was extracted and verified using confirmation test. The average diameter of nanofibers at the optimum conditions was in the range of 242.10 to 257.92 nm at a confidence level 95% which was in close agreement with the predicted value by the Taguchi technique. Also, the mechanical properties increased with decreasing fibers diameter. This study demonstrated Taguchi method was successfully applied to the optimization of electrospinning conditions for TPU nanofibers and the presented scaffold can mimic the structure of Extracellular Matrix (ECM).

• Journal of Biomedical Engineering Research
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• v.16 no.1
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• pp.1-8
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• 1995

A variety of experiments of endothelial cell seeding onto artificial vessels have been performed. To improve endothelialization, one or two components of the extracellular matrix (ECM) have been used as an underlying matrix. In this study, the whole ECM excreted from fibroblasts was used as an underlying matrix. Fetal human fibroblasts were cultured on a polyurethane (PU) sheet. After a conflu; ence was attained, the cytoskeleton and the nuclei of the fibroblast were destroyed using Triton-X. Mitomycin, or irradiation. Omental microvascular endothelial cells from adult human were seeded onto various substrates. After 12 days in culture, the cells were counted. It was observed that the ECM treated by irradiation had the highest cell number. In addition, the cells on this substrate exhibited the most typical endothelial cell morphology. For preliminary animal experiments the PU vessels (inner diameter, 1.5mm) coated with ECM were implanted in the infrarena] abdominal aorta of rat. After the vessels had been implanted for 5 weeks, it was found that the surface of the PU vessels was completely covered with endothelia] cells. In conclusion, we can state that the fibroblast-derived whole ECM makes a better underlying substrate for the endothelialization of small diameter artificial vessels.

• Journal of Biomedical Engineering Research
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• v.17 no.2
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• pp.255-262
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• 1996

Antithrombogenic surFace is one of the most important things to the artificial vascular prostheses. This problem will be solved if the surface of prosthesis is covered with endothelial cells. The attachment and the growth of endothelial cells onto vascular prosthesis are very difficult. So many studies have been concentrated on the attachement of endothelial cell. But no good performance of the in uiwo experiments has been shown until now. In this study, we used the whole extracellular matrix (ECM) excreted from fibroblasts as an underlying matrix, and the endothelial cells were seeded to obtain the long term patency of vascular graft(i.e., for the patent 8 week implanted wafts in the animal model of rat). In order to study the antithrombogenic functions of cultured endothelial cells, prostaglandin(PGF 1 a) synthesis and platelet adhesion were assayed. The concentration of PGF a of stimulated group was sisnificantly higher than that of control group(21.97 $\pm$ 3.45 vs 4.93 $\pm$0.71 pg/1000 cells). The platelet adhesion of the polyurethane sheet covered with endothelial cells was lower than that of polyurethane sheet or sheet covered with ECM(1.04$\pm$0.28, 2.87$\pm$0.77, 2.89$\pm$0.70, % radioactivities, respectively). Endothelial cells grew well on polyurethane coated with ECM, synthesized the prostacyclin and functioned well as antithrombogenic. Therefore the endothelialization onto the ECM excreted from fibroblasts may be a good method for the vfudig prosthesis.