• Macromolecular Research
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• v.10 no.3
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• pp.158-167
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• 2002

In order to endow with new bioactive functionality from small intestine submucosa (SIS) powder as natural source to poly (L-lactide) (PLA) and poly (lactide-co-glycolide) (PLGA) synthetic biodegradable polymer, porous SIS/PLA and SIS/PLGA as natural/synthetic composite scaffolds were prepared by means of the solvent casting/salt leaching methods for the possibility of the application of tissue engineered bone and cartilage. A uniform distribution of good interconnected pores from the surface to core region was observed the pore size of 40~500 ${\mu}{\textrm}{m}$ independent with SIS amount using the solvent casting/salt leaching method. Porosities, specific pore areas as well as pore size distribution also were almost same. After the fabrication of SIS/PLA hybrid scaffolds, the wetting properties was greatly enhanced resulting in more uniform cell seeding and distribution. Five groups as PGA non-woven mesh without glutaraldehyde (GA) treatment, PLA scaffold without or with GA treatment, and SIS/PLA (Code No.3 ; 1 : 12 of salt content, (0.4 : 1 of SIS content, and 144 ${\mu}{\textrm}{m}$ of median pore size) without or with GA treatment were implanted into the back of nude mouse to observe the effect of SIS on the induction of cells proliferation by hematoxylin and eosin, and von Kossa staining for 8 weeks. It was observed that the effect of SIS/PLA scaffolds with GA treatment on bone induction are stronger than PLA scaffolds, that is to say, in the order of PLA/SIS scaffolds with GA treatment > PLA/SIS scaffolds without GA treatment > PGA nonwoven > PLA scaffolds only with GA treatment = PLA scaffolds only without GA treatment for the osteoinduction activity. The possible explanations are (1) many kinds of secreted, circulating, and extracellular matrix-bound growth factors from SIS to significantly affect critical processes of tissue development and differentiation, (2) the exposure of SIS to GA resulted in significantly calcification, and (3) peri-implant fibrosis due to covalent bonding between collagen molecule by crosslinking reaction. In conclusion, it seems that SIS plays an important role for bone induction in SIS/PLA scaffolds for the application of tissue engineering area.

• Archives of Pharmacal Research
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• v.26 no.2
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• pp.173-181
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• 2003

A polymeric micelle drug delivery system was developed to enhance the solubility of poorly-water soluble drug, biphenyl dimethyl dicarboxylate, DDB. The block copolymers consisting of poly(D,L-lactide) (PLA) as the hydrophobic segment and methoxy poly(ethylene glycol) (mPEG) as the hydrophilic segment were synthesized and characterized by NMR, DSC and MALDI-TOF mass spectroscopy. The size of the polymeric micelles measured by dynamic light scattering showed a narrow monodisperse size distribution with the average diameter less than 50 nm. The MW of mPEG-PLA, 3000 (MW of mPEG, 2 K; MW of PLA, 1K), and the presence of hydrophilic and hydrophobic segments on the polymeric micelles were confirmed by MALDI-TOF mass spectroscopy and NMR, respectively. Polymeric micelle solutions of DDB were prepared by three different methods, i.e. the matrix method, emulsion method and dialysis method. In the matrix method, DDB solubility was reached to 13.29 mg/mL. The mPEG-PLA 2K-1K micelle system was compared with the poloxamer 407 micelle system for their critical micelle concentration, micelle size, solubilizing capacity, stability in dilution and physical state. DDB loaded-polymeric micelles prepared by the matrix method showed a significantly increased aqueous solubility (＞5000 fold over intrinsic solubility) and were found to be superior to the poloxamer 407 micelles as a drug carrier.

• Journal of Pharmaceutical Investigation
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• v.32 no.3
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• pp.199-207
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• 2002

In order to develop a sustained release formulation of bovine somatotropin (BST), which has been used to increase the body weight of oxen or the milk production of dairy cows, poly(D,L-lactide-co-glyceride)(PLGA) microspheres were made by W/O/W multiple emulsification method and solvent extraction method. Physical properties including particle size, drug entrapment, drug release, protein denaturation, and in vivo body weight increase in rats were characterized. The size of the microspheres was increased as the molecular weight of PLGA increased. When Span 65 and stearic acid during preparation were added, the size was decreased but the amount of surface protein was increased, resulting in a high loading efficiency, with fast release of BST from the microspheres. Aggregation or fragmentation of BST by SDS-PAGE during microsphere preparation and drug release study was not observed. Body weight of Sprague-Dawley's male rats was significantly increased after subcutaneous administrations of BST-loaded PLGA microspheres. There was a good correlation between in vivo weight gain and in vitro release rate of microspheres. PLGA microspheres with a high surface protein ratio could be a good candidate for the sustained delivery of BST.

• Journal of Biomedical Engineering Research
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• v.34 no.3
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• pp.111-116
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• 2013

Finite element analysis(FEA) has been extensively applied in the analyses of biomechanical properties of stents. Geometrically, a closed-cell stent is an assembly of a number of repeated unit cells and exhibits periodicity in both longitudinal and circumferential directions. This study concentrates on various parameters of the FEA models for the analysis of drug-eluting biodegradable polymeric stents for application to the treatment of coronary artery disease. In order to determine the mechanical characteristics of biodegradable polymeric stents, FEA was used to model two different types of stents: tubular stents(TS) and helicoidal stents(HS). For this modeling, epigallocatechin-3-O-gallate (EGCG)-eluting poly[(L-lactide-co-${\varepsilon}$-caprolactone), PLCL] (E-PLCL) was chosen as drug-eluting stent materials. E-PLCL was prepared by blending PLCL with 5% EGCG as previously described. In addition, the effects of EGCG blending on the mechanical properties of PLCL were investigated for both types of stent models. EGCG did not affect tensile strength at break, but significantly increased elastic modulus of PLCL. It is suggested that FEA is a cost-effective method to improve the design of drug-eluting biodegradable polymeric stents.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.1671-1676
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• 2015

A unique crystallization behavior of poly(L-lactide)(PLLA)/poly(D-lactide)(PDLA) stereocomplex(SC) was observed when a PLLA/PDLA blend was subjected to the specific melting conditions. Therefore, we tried to blend PLLA and PDLA at overall composition to form PLA stereocomplexes. Moreover, impact modifier and reinforcement materials such as talc and glass fiber added to enhance the mechanical and thermal properties such as impact strength and heat distortion temperature(HDT). As a result, we got one representative result, one composite recipe with HDT $115^{\circ}C$. For more economic technology, we tried to blend PLLA and Polypropylene at overall composition and we got another representative result which could be applied to current PP/talc composites and ABS materials. The core technology of this might be the well dispersion of glass fibers into the matrix resin such as PP, PLLA and impact strength modifier.

• Macromolecular Research
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• v.11 no.3
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• pp.183-188
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• 2003

The controlled delivery of anticancer agents using biodegradable polymeric implant has been developed to solve the problem of penetration of blood brain barrier and severe systemic toxicity. This study was performed to prepare 5-FU-loaded poly (L-lactide-co-glycolide) (PLGA) wafer fabricated microparticles prepared by two different method and to evaluate their release profile for the application of the treatment of brain tumor. 5-FU-loaded PLGA microparticles were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC). SEM observation of the 5-FU-loaded PLGA microparticles prepared by rotary solvent evaporation method showed that 5-FU was almost surrounded by PLGA and significant reduction of crystallinity of 5-FU was confirmed by XRD. In case of release profile of 5-FU from 5-FU-loaded PLGA wafer fabricated microparticles prepared by mechanical mixing, the release profile of 5-FU followed near first order release kinetics. In contrast to the above result, release profile of 5-FU from 5-FU-loaded PLGA wafer fabricated microparticles prepared by rotary solvent evaporation method followed near zero order release kinetics. These results indicate that preparation method of the 5-FU-loaded PLGA microparticles to fabricate into wafers was contributed to drug release profile.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.727-732
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• 2013

In this report, we present an inverse opal scaffold that can enhance the chondrogenic differentiation of human adipose-derived stem cells (hADSCs) without drug, gene, or cytokine supplement. Inverse opal scaffolds based on poly(D,L-lactide-co-glycolide) were formed with uniform $200{\mu}m$ pores. Due to uniform pore sizes and well-controlled interconnectivity of inverse opal scaffold, hADSCs were allowed to distribute homogeneously throughout the scaffolds. As a result, high cell density culture with scaffold was possible. Since the hADSCs cultured in inverse opal scaffolds were subjected to limited supplies of oxygen and nutrients, these cells were naturally preconditioned to a hypoxic environment that stimulated the up-regulation of hypoxia-inducible factor-$1{\alpha}$ (HIF-$1{\alpha}$). As a result, apoptotic activity of hADSCs until 3 weeks after initial cell seeding was significantly reduced and chondrogenic differentiation related molecular signal cascades were up regulated (transforming growth factor-beta, phosphorylated AKT, and phosphorylated p38 expression). In contrast, hADSCs cultured with small and non-uniform porous scaffolds showed significantly increased apoptotic activity with decreased chondrogenic differentiation. Taken together, inverse opal scaffold could potentially be used as an effective tool for improving chondrogenesis using stem cells.

• Macromolecular Research
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• v.8 no.6
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• pp.276-284
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• 2000

A wettability chemogradient on poly(L-lactide-co-glycolide) (PLGA) films was prepared by treating the films in air with corona from a knife-type electrode whose power increases gradually along the sample length. The PLGA surfaces oxidized gradually with the increasing corona power, and the wettability chemogradient was created on the surfaces as evidenced by the measurement of water contact angles and electron spectroscopy for chemical analysis. The wettability chemogradient PLGA surfaces were used to investigate the interaction of four different types of cells such as hepatoma (Hep G2), osteoblast (MG 63), bovine aortic endothelial (CPAE), and fibroblast (NIH/3T3) cells in terms of the surface hydrophilicity/hydrophobicity of PLGA. The cells adhered and grown on the chemogradient surface along the sample length were counted and observed by scanning electron microscopy. It was observed that the cells were adhered, spread, and grown more onto the positions with moderate hydrophilicity of the wettability chemogradient PLGA surface than the more hydrophobic or hydrophillic positions, regardless of the cell types used. The maximum adhesion and growth of the cells appeared at around water contact angles of 53～55°. This result seems closely related with the serum protein adsorption on the surface; the serum proteins were also adsorbed more onto the positions with moderate hydrophilicity of the wettability chemogradient surface. It seems that the wettability plays important roles for cell adhesion, spreading and growth on the PLGA surface. The surface modification technique used in this study may be applicable tothe area of tissue engineering for the improvement of tissue compatibility of films- or scaffold-type substrates.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.27 no.2
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• pp.160-163
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• 2005

This study was designed to assess skeletal stabilily after surgical correction of mandibular prognathism by bilateral saggital split ramus osteotomy(BSSRO) and fixation with absorbable screws. From July 2001 to September 2003, 30 patients with Class III malocclusion were treated with BSSRO and mandibular setback. They underwent fixation with Biosorb$^{TM}$ FX screws. Cephalograms were obtained preoperatibely, 2 or 3 days postoperatively, and about 12 months after the operation. Changes in the position of lower incisor tip, B point, and pogonion were examined on lateral cephalograms. The mean mandibular setback just after surgery was 10.6mm. 12 months after surgery, mean relapse at pogonion represented 17.9% and 15.1% at B point. Our results suggest that fixation of the bony segments with absorbable screws after BSSO may be used effectively in properly selected cases.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.30 no.4
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• pp.323-332
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• 2008

Aim of the study: Scaffolds are crucial to tissue engineering/regeneration. Biodegradable polymer/ceramic composite scaffolds can overcome the limitations of conventional ceramic bone substitutes such as brittleness and difficulty in shaping. In this study, poly(L-lactide)/hydroxyapatite(PLLA/HA) composite scaffolds were fabricated for in vivo bone tissue engineering. Material & methods: In this study, PLLA/HA composite microspheres were prepared by double emulsion-solvent evaporation method, and were evaluated in vivo bone tissue engineering. Bone marrow mesenchymal stem cell from rat iliac crest was differentiated to osteoblast by adding osteogenic medium, and was mixed with PLLA/HA composite scaffold in fibrin gel and was injected immediately into rat cranial bone critical size defect(CSD:8mm in diameter). At 1. 2, 4, 8 weeks after implantation, histological analysis by H-E staining, histomorphometric analysis and radiolographic analysis were done. Results: BMP-2 loaded PLLA/HA composite scaffolds in fibrin gel delivered with osteoblasts differentiated from bone marrow mesenchymal stem cells showed rapid and much more bone regeneration in rat cranial bone defects than control group. Conclusion: This results suggest the feasibility and usefulness of this type of scaffold in bone tissue engineering.