• Polymer(Korea)
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• v.35 no.5
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• pp.378-384
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• 2011

Silk fibroin is a biocompatible and slowly biodegradable natural polymer. This natural polymer has excellent mechanical properties, non-toxicity, and non-immunogenic properties and has been demonstrated to support tissue regeneration. Also, gelatin is a natural material derived from collagen by hydrolysis and has an almost identical composition as that of collagen. Silk fibroin/gelatin scaffolds have been fabricated by using the freeze-drying method. To establish the scaffold manufacturing condition for silk fibroin and gelatin, we made scaffolds with various compositions of gelatin, glutaldehyde and silk fibroin. The silk fibroin/gelatin scaffolds were characterized using SEM, DSC, and water absorption ability tests. The cellular proliferation was evaluated by WST assay. These results suggested that a scaffold containing 8% of gelatin, 1% of glutaldehyde and 0.3 g of silk fibroin provided suitable characterstics for cell adhesion and proliferation. In conclusion, the silk fibroin/gelatin scaffold may serve as a potential cell delivery vehicle and a structural basis for tissue engineering.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.231-235
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• 2005

Most tissue engineering strategies for creating functional replacement tissues or organs rely on the application of temporary three-dimensional scaffolds to guide the proliferation and spread of seeded cells in vitro and in vivo. Scaffolds should be satisfied following requirements; macrostructure to promote cell proliferation, pore interconnectivity, pore size ranging from 200 to $400{\mu}m$, surface chemistry and mechanical properties. Rapid prototyping techniques have often been used as an useful process that fabricates scaffolds with complex structures. In this study, a new process to fabricate a three-dimensional scaffolds using bio-compatible polymer has been developed. It employs a highly accurate three-dimensional positioning system with pressure-controlled syringe to deposit biopolymer structures. The pressure-activated microsyringe is equipped with fine-bore nozzles of various inner-diameters. In order to examine relationships between line width and process parameters such as nozzle height, applied pressure, and speed of needle, experiments were carried out. Based on the experimental results, three-dimensional scaffold was fabricated using the apparatus. It shows the validity of the proposed process.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.6
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• pp.686-692
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• 2012

Solid free-form fabrication (SFF) technology was developed to fabricate three-dimensional (3D) scaffolds for tissue engineering (TE) applications. In this study, we developed a polymer deposition system (PDS) and created 3D microstructures using a bioresorbable polycaprolactone (PCL) polymer. Fabrication of 3D scaffolds by PDS requires a combination of several devices, including a heating system, dispenser, and motion controller. The system can process a polymer with extremely high precision by using a 200 ${\mu}m$ nozzle. Based on scanning electron microscope (SEM) images, both the line width and the piled line height were fine and uniform. Several 3D micro-structures, including the ANU pattern (a pattern named after Andong National University), $45^{\circ}$ pattern square, frame, cylindrical, triangular, cross-shaped, and hexagon, have been fabricated using the polymer deposition system.

• Polymer(Korea)
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• v.34 no.5
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• pp.474-479
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• 2010

We developed laminated cylindrical scaffolds composed of poly(lactide-co-glycolide)(PLGA) and keratin, and investigated their potential for tissue engineering and disk regeneration. The scaffold was designed to have two parts, i.e. inner cylinder and outer disk, to mimic a natural disk. The outer disk was composed of PLGA and the inner cylinder was prepared using PLGA film or PLGA/keratin hybrid film. In this study, we investigated the effects of keratin on the growth and proliferation of annulus fibrous(AF) cells in the cylindrical scaffolds. Scaffolds containing PLGA/keratin films showed a significantly higher cell proliferation and expression of collagen I and II than the counterpart with PLGA films. Keratin containing scaffolds also exhibited an excellent mechanical strength, demonstrating that keratin influences the proliferation of annulus fibrous cells. The results provide valuable information on PLGA/keratin films for tissue engineered disk regeneration.

• Polymer(Korea)
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• v.28 no.5
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• pp.382-390
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• 2004

One of the significant natural bioactive materials is demineralized bone particle (DBP) whose has a powerful induce. of new bone growth. In this study, we developed the DBP loaded poly-lactide (PLA) and poly(L-lactide-co-glycolide) (PLGA) scaffolds for the possibility of the application of the tissue engineered bone. PLA/DBP and PLGA/DBP scaffolds were prepared by solvent casting/salt leaching method and were characterized by porosimeter, scanning electron microscopy. BMSCs were stimulated by osteogenic medium and characterized by histological stained Wright-Giemsa, Alizarin red, von Kossa, and alkaline phosphate activity (ALP). DBP impregnated scaffolds with BMSCs were implanted into the back of athymic nude mouse to observe the effect of DBP on the osteoinduction compared with control scaffolds. It can be observed that the porosity was above $90.2\%$ and the pore size was above 69.1$\mu$m. BMSCs could be differentiated into osteoprogenitor cells as result of wright-giemsa, alizarin red, von Kossa and ALP staining. In in vivo study, we could observed calcification region in PLA/DBP and PLGA/DBP groups, but calcification did not occur almost in control scaffolds. From these results, it seems that DBP as well as BMSCs play an important role for bone induction in PLA/DBP and PLGA/DBP scaffolds.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.268-268
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• 2006

Due to their multipotency, stem cells can differentiate into a variety of specialized cell types, such as chondrocytes, osteoblasts, myoblasts, and nerve cells. As an alternative to mature tissue cells, stem cells are of importance in tissue engineering and regenerative medicine. Since interactions between scaffold and cells play an important role in the tissue development in vitro, synthetic oligopeptides have been immobilized onto polymeric scaffolds to improve specific cell attachment and even to stimulate cell differentiation. In this study, chondrogenic differentiation of stem cells was evaluated using surface-modified PLLA scaffolds, i.e., either hydrophilic acrylic acid (AA)-grafted PLLA or RGD-immobilized one. Porous PLLA scaffolds were prepared using a gas foaming method, followed by plasma treatment and subsequent grafting of AA to introduce a hydrophilicity (PLLA-PAA). This was further processed to fix RGD peptide to make an RGD-immobilized scaffold (PLLA-PAA-RGD). Stem cells were seeded at $1{\times}10^{6}$ cells per scaffold and the cell-PLLA constructs were cultured for up to 4 weeks in the chondrogenic medium. Using these surface-modified scaffolds, adhesion, proliferation, and chondrogenic differentiation of stem cells were evaluated. The surface of PLLA scaffolds turned hydrophilic (water contact angle, 45 degrees) with both plasma treatment and AA grafting. The hydrophilicity of RGD-immobilized surface was not significantly altered. Cell proliferation rate on the either PLLA-PAA or PLLA-PAA-RGD surface was obviously improved, especially with the RGD-immobilized one as compared to the control PLLA one. Chondrogenic differentiation was clearly identified with Safranin O staining of GAG in the AA- or RGD-grafted PLLA substrates. This study demonstrated that modified polymer surfaces may provide better environment for chondrogenesis of stem cells.

• Polymer(Korea)
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• v.38 no.2
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• pp.156-163
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• 2014

Hydroxyapatite has osteoconductivity, biocompatibility and noninflammatory, and it has been used clinically as artificial bone. In this study, we prepared hydroxyapatite/poly(lactic-co-glycolic acid) (PLGA) scaffolds using 0, 10, 20, 40 and 60 wt% of hydroxyapatite. We analyzed compressive strength, SEM analysis and FTIR for mechanical property of 3D hydroxyapatite/PLGA scaffolds. For biocompatibility tests, cell proliferation and viability were measured via MTT assay and SEM. We analyzed RT-PCR, FACS, histology (H&E, ED-1) for anti-inflammatory effect. This study showed that hydroxyapatite hybrid scaffolds have low inflammatory reaction compared with the PLGA. This result has a potential for the application of artificial bone graft material.

• Macromolecular Research
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• v.16 no.4
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• pp.303-307
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• 2008

A series of biodegradable polymeric scaffolds was prepared by using a combination of natural (collagen) and synthetic (poly(caprolactone)) (PCL) polymers in various compositions. These scaffolds were soft, spongy, porous and transparent in nature and were characterized by thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopy. The entrapment efficiency and drug release activity of the scaffolds were analyzed using penicillin and tetracycline as antimicrobial drugs. The drug release activity of the scaffolds with various combinations of collagen and PCL were studied by measuring the optical density in a spectrophotometer at the following time intervals: 1,4, 24, 48 and 60 h. These scaffolds showed better and continuous drug release for up to 60 h. Even after such a long duration, a portion of the drug remained entrapped in the scaffolds, indicating that they can be utilized for wound healing applications.

• Journal of the Korean Applied Science and Technology
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• v.20 no.4
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• pp.324-331
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• 2003

Particulate leaching method for the preparation of porous PLLA scaffolds was carried out and especially, the effect of PLLA/$CHCl_3$ solution concentration on the salt leaching rate and the pore structure of PLLA scaffolds were considered. It was found that maintaining lower PLLA/$CHCl_3$ concentration and higher $CHCl_3$ evaporation temperature in the preparation of PLLA/NaCl mixtures resulted in the enhancement of salt leaching rat e and higher porosity. This is understood that those conditions could minimize the formation of dense PLLA layer on the surface of PLLA/NaCl mixture as well as introducing better porosity on the surface. Higher salt leaching temperature accelerated the salt leaching rate but it seems that there is no influence on the porosity of PLLA scaffolds.

• Fibers and Polymers
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• v.2 no.2
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• pp.51-57
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• 2001

Tissue engineering is one exciting approach to treat patients who need a new organ or tissue. A critical element in this approach is the polymer scaffold, as it provides a space for new tissue formation and mimics many roles of natural extra-cellular matrices. In this review, we describe several design parameters of polymer matrices that can significantly affect cellular behavior, as well as various polymers which are frequently used to date or potentially useful in many tissue engineering applications. Interactions between cells and polymer scaffolds, including specific receptor-ligand interactions, physical and degradation feature of the scaffolds, and delivery of soluble factors, should be considered in the design and tailoring of appropriate polymer matrices to be used in tissue engineering applications, as these interactions control the function and structure of engineered tissues.