• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.12
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• pp.59-66
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• 2019

In this study, we developed a novel laser sintering deposition system (LSDS) based on solid free-form fabrication (SFF) technology as it has the potential to fabricate complex geometries with controllable architecture for bone tissue engineering applications. The 3D biphasic calcium phosphate (BCP) scaffolds were fabricated with a pore size of 800㎛, a line width and height of 1000㎛, and an overall size of 8.2×8.2×8.0 mm3 according to the design of experiment (DOE) results. Additionally, an optimized manufacturing process using response surface analysis was established to fabricate 3D BCP scaffolds. The fabricated 3D BCP scaffolds were sintered at 950℃, 1050℃, 1150℃, and 1250℃ according to sintering processes with a furnace. As the sintering temperature increased, the porosity increased. Through the compressive strength test, the 3D BCP scaffolds sintered at 1050℃ presented good results of about 0.76 MPa. These results suggest that fabrication methods for 3D bioceramic scaffolds using LSDS may meet the basic requirements for bone tissue engineering.

• Journal of Biomedical Engineering Research
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• v.26 no.1
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• pp.37-42
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• 2005

We construct and test the polarization-sensitive optical coherence tomography (PS-OCT) system for imaging porcine and human articular cartilages. PS-OCT is a new imaging technology that provides information regarding not only the tissue structures but tissue components that show birefringence such as collagen. In this study, we measure the cartilage thickness of the porcine joint and the phase retardation due to collagen birefringence. Also, we demonstrate that changes of the collagen fiber orientation could be detected by the PS-OCT system. Finally, differences between normal and damaged human articular cartilage are observed using the PS-OCT system, which is then compared with the regular histology pictures. As a result, the PS-OCT system is proven to be effective for diagnosis of the pathology related to the cartilage. In the future, this technology may be used for discrimination of the collagen types. When combined with endoscope technologies, the PS-OCT images may become a useful tool for in vivo tissue testing.

• Macromolecular Research
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• v.15 no.3
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• pp.238-243
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• 2007

Nanofibers were prepared by electrospinning a solution of poly(lactic-co-glycolic acid) (PLGA) and their mean diameter was 340 nm. The PLGA nanofibers were treated with a plasma in the presence of either oxygen or ammonia gas to change their surface characteristics. The hydrophilicity of the electrospun PLGA nanofibers was significantly increased by the gas plasma treatment, as confirmed by contact angle measurements. XPS analysis demonstrated that the chemical composition of the PLGA nanofiber surface was influenced by the plasma treatment, resulting in an increase in the number of polar groups, which contributed to the enhanced surface hydrophilicity. The degradation behavior of the PLGA nanofibers was accelerated by the plasma treatment, and the adhesion and proliferation of mouse fibroblasts on the plasma-treated nanofibers were significantly enhanced. This approach to controlling the surface characteristics of nanofibers prepared from biocompatible polymers could be useful in the development of novel polymeric scaffolds for tissue engineering.

• Journal of Biomedical Engineering Research
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• v.43 no.4
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• pp.219-229
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• 2022

In this study, we propose a miniaturized micro-ceramic heater device. After screen-printing a silver paste between pre-sintered two aluminum oxide plates to integrate a heating circuit, the device was fabricated through a low-temperature sintering process. In order to configure the optimal heating circuit integration condition, the output current evaluation and heating test were performed according to the number of screen prints of the silver paste at various voltages. A silver paste-based heating circuit printed with a line width of 200 ㎛ and a thickness of 60 ㎛ was successfully integrated on a pre-sintered alumina substrate through a low-temperature sintering process. In the case of the 5 times printed device, the thermal response showed a response rate of 18.19 ℃/sec. To demonstrate feasibility of the proposed device in the medical field, such as bio-tissue suturing and hemostasis, a voltage was applied to pig tissue in the device to test tissue change due to heat generated from the device. These results show the possibility that the proposed small ceramic heater could be used in the medical field based on its excellent temperature response.

• Journal of Plant Biotechnology
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• v.5 no.1
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• pp.25-31
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• 2003

As a consequence of tissue culture of rice, RAPD analysis was peformed to determine whether extended culture periods as undifferentiated calli affected the subsequent genetic constancy, and whether any resulting DNA rearrangements could be detected between sibling plants produced from the same callus. Somaclonal variation was induced at the initial stage of tissue culture and it increased with the length of culture maintenance. Of the 192 total bands, the number of polymorphic bands was 22 (11.5%), 33 (17.2%), and 49 (25.5%) in the callus of 1,3, and 6 months culture, respectively. A significantly higher level of genotypic polymorphisms between regenerants from two different somaclones was also detected, although all the regenerants were derived from a single genotype. In comparison of DNA polymorphisms between regenerants from non-irradiated and from irradiated calli, a scope of variation spectrum by gamma ray irradiation was larger than that by tissue culture. Consideration must be given to this genomic variation where attempts are to be made to use desirable somaclonal variants for plant breeding purpose and in genetic engineering program.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.2
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• pp.71-77
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• 2023

Absorbable periodontal tissue regeneration barrier membranes (total 6; domestic 4; import 2) were comparatively analyzed. In the case of the xenograft barrier membrane, the collagen product had excellent tensile strength but low strain, and the porcine pericardial membrane had good mechanical properties, but its thickness was too thick to control. The synthetic PLLA membrane manufactured by the electrospinning had a relatively low water absorption capacity. However, the hybrid barrier membrane was able to control mechanical properties and biocompatibility through proper mixing of synthetic polymer and natural polymer. DA02 (PLLA/gelatin), a newly developed hybrid absorbable periodontal tissue regeneration membrane that is entirely dependent on imports, can be applied to an absorbable periodontal tissue regeneration barrier membrane due to suitable mechanical properties and biocompatibility.

• Biomaterials and Biomechanics in Bioengineering
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• v.1 no.3
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• pp.151-162
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• 2014

Genetically-modified mesenchymal stem cells (GM-MSCs) have emerged as promising therapeutic tools for orthopedic degenerative diseases. GM-MSCs have been widely reported that they are able to increase bone and cartilage tissue regeneration not only by secreting transgene products such as growth factors in a long-term manner, also by inducing MSCs into tissue-specific cells. For example, MSCs modified with BMP-2 gene increased secretion of BMP-2 protein resulting in enhancement of bone regeneration, while MSCs with TGF-b gene did cartilage regeneration. In this review, we introduce several growth factors for gene delivery to MSCs and strategies for bone and cartilage tissue regeneration using GM-MSCs. Furthermore, we describe strategies for strengthening GM-MSCs to more intensively induce tissue regeneration by co-delivery system of multiple genes.

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.303-309
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• 2019

Tritium is an important nuclide that must be monitored for radiation safety management. In this study, HTO was orally administered to rats at the level of 37 kBq ($1{\mu}Ci$) or 370 kBq ($10{\mu}Ci$) to examine tissue distribution and excretion levels. After sacrifice, wet and dry tissue samples were weighed and analyzed for tissue free-water tritium (TFWT) and organically bound tritium (OBT). The mean tissue concentrations of TFWT (OBT) were 30.9 (17.8) and 4.4 (8.1) Bq/g on days 7 and 13 at the 37 kBq level and 30.8 (64.6) Bq/g on day 17 at the 370 kBq level. To assess the cytogenetic damage due to tritium exposure, a cytokinesis-blocked micronucleus (MN) assay was performed in blood samples from rats exposed to HTO for 14 and 21 days after oral administration. There was no significant difference in the MN frequencies between the control and exposed rats.

• Journal of Plant Biotechnology
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• v.1 no.2
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• pp.91-95
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• 1999

Genetic engineering of stone fruit species like apricot, plum, peach and cherry are hampered by the inefficient and low-level regeneration processes in tissue culture. The first transgenic stone fruit species have emerged from transformed hypocotyls. These great achievements were applauded by the scientific community contrary the fact that hypocotyl derived transgenic plants have no real brooding value. Tissue culture of different organs of valuable cultivars are recorded with an extremely low-level of regeneration in the literature. To improve the tissue culture basis of stone fruit plants an extensive tissue culture programme were launched and dozens of different media were compared including a series of hormone concentration in the tissue culture systems. Our continuous efforts were crowned by a very efficient method for achieving up to 30-40% regenerable petioles. Usually on a single petiole several well-separated meristems were induced. After 3-4 weeks of cultivation shoots were developed. The basic media $K_2$ were supplemented with 10g/L saccharose, 10g/L glucose and 10g/L maltose. The following plant hormones were used BAP 1mg/L, TDZ 1mg/L, 2-iP 1mg/L and IAA 0,1 mg/L concentrations. The Petri dishes were kept for 3 weeks in dark at a temperature 22$^{\circ}C$ for 8 hours and 22-24$^{\circ}C$ for 16 hours. The Petri dishes were sealed with Parafilm. The regeneration of the petioles were genotype independent and we were able to regenerate different plum cultivars with almost the same efficiency.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.33 no.4
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• pp.322-330
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• 2007

Backgrounds: To overcome limited amount of autogenous mucosa for the reconstruction of various mucosal defect including oral mucosal defect, tissue engineered mucosa has been recently introduced. However, introduced conventional technique of tissue engineered mucosa still have serious pitfalls such as long fabrication time, fragility of the reconstructed mucosa, and complexity of the technique. Aim of the study: To examine whether the complex of preconfluent autologous keratinocytes and autologous PRP(Platelet rich plasma) can reconstruct oral mucosa on the muscular flap with easier and faster way compared to conventional mucosal tissue engineering technique. Materials and methods: One day before the operation, oral mucosa(3mm in diameter) were taken and treated for extraction of oral keratinocytes according to the routine manner. The day of operation, oral keratinocytes were prepared in the laboratory and then moved to the operating theater. Autologous PRP was also prepared and then mixed with oral keratinocytes just before grafting on the prepared muscular flap. After keratinocyte-PRP complex was seated, then a sterilized rubber sheet was placed on the graft and the elevated skin flap was replaced and sutured. Biopsies were proceeded at 3, 5, 7, 14 and 21 days. Tissue samples were evaluated clinically, histologically, and immunohistochemically. Results: All of the oral keratinocyte-PRP complexes were successfully grafted on the recipient sites(100%). On 3 days after the operation, 1-2 continuous epithelial layer and many inflammatory cells were observed. On 5 days after the operation, increase of layers of keratinocyte was observed with less inflammatory response. Thickness of the layers was gradually increased from 7 to 21 days after the operation. Cytokeratin confirms epithelium in every specimen. Conclusions: Preconfluent graft of autogenous oral keratinocytes mixed with autogenous PRP have successfully reconstructed myo-mucosal flap. This technique could be a useful alternative for oral mucosal reconstruction in the near future.