• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.181-181
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• 2006

We developed a novel method to fabricate a nerve guide conduit (NGC) with the porosity of submicron pore sizes (to prevent fibrous tissue infiltration) and hydrophilicity (for effective oxygen and nutrient permeation) using poly(lactic-co-glycolic acid) (PLGA) and Pluronic F127 by a modified immersion precipitation method designed by our laboratory. It was recognized that the hydrophilized PLGA/F127 (3 wt%) tube can be a good candidate as a NGC from the analyses of its morphology, mechanical strength, hydrophilicity, model nutrient permeability and in vivo nerve regeneration behavior using a rat model.

• Journal of Environmental Science International
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• v.24 no.1
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• pp.9-15
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• 2015

Sustainable and eco-friendly polymers, natural polymers, bio-based polymers, and degradable polyesters, are of growing interest because of environmental concerns associated with waste plastics and emissions of carbon dioxide from preparation of petroleum-based polymers. Degradable polymers, poly(butylene adipate-co-terephthalate) (PBAT), poly(propylene carbonate) (PPC), and poly(L-lactic acid) (PLLA), are related to reduction of carbon dioxide in processing. To improve a weak mechanical property of a degradable polymer, a blending method is widely used. This study was forced on the component separation of degradable polymer blends for effective recycling. The melt-mixed blend films in a specific solvent were separated by two layers. Each layer was analysed by FT-IR, DSC, and contact angle measurements. The results showed that each component in the PPC/PLLA and PPC/PBAT blends was successfully separated by a solvent.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.251-258
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• 2015

In the study, PLLA with 12,000 g/mol ($M_n$) and 14,000 g/mol ($M_w$) was synthesized from L-lactide, and used to synthesize PLLA-Br intermediate. PLLA-block-PMMA with 84,000 g/mol ($M_n$) and 126,000 g/mol ($M_w$) was finally synthesized from PLLA-Br intermediate. The glass transition temperature ($T_g$) and initial pyrolysis temperature of PLLA-block-PMMA are $95.5^{\circ}C$ and $289^{\circ}C$, respectively. The PLA film of $50{\pm}3{\mu}m$ thickness was prepared by blending PLA with 9 phr PLLA-block-PMMA followed by stretching biaxially at 3 times under $95^{\circ}C$, and annealing at $120^{\circ}C$ for 2 min. The light transmittance at 550 nm and tensile strength of the film are 88.5% and 44.5 MPa, respectively. To enhance the tensile strength of PLA film, it was required to keep the film more than 2 min at $120^{\circ}C$ during the annealing step after a biaxially orientation.

• Journal of Biosystems Engineering
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• v.32 no.1 s.120
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• pp.50-56
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• 2007

Highly porous composite bioceramic bone scaffolds were developed using sintered gnotobiotic pig bones. These scaffolds consisted of poly-D,L-lactic acid (P(D,L)LA) and bioceramic materials of pig bone powder. The bone scaffolds were able to promote biocompatibility and possess interconnected pores that would support cell adhesion and proliferation adequately. The composite scaffolds were tested with dental pulp stem cells for cytotoxicity test. Cells seeded on the composite scaffolds were readily attached, well proliferated, as confirmed by cytotoxicity test, and cell adhesion assessment. The composite bone scaffold had no toxicity in cytotoxicity test on the extract of 0.013 g scaffold to 2 ml culture medium. The cells on the composite bone scaffold proliferated better than cells on the P(D,L)LA scaffolds.

• Polymer(Korea)
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• v.36 no.3
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• pp.357-363
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• 2012

Surface-modified poly(L-lactic acid) (PLLA) films and scaffolds were treated with plasma discharge in oxygen gas and subsequently subjected to $in$ $situ$ grafting of acrylic acid (AA) in order to increase the cell compatibility. The surface of AA-grafted PLLA was converted to hydroxyapatite (HA)-deposited PLLA in stimulated body fluid (SBF). After the samples were immersed in phosphate-buffered saline (PBS), fetal bovine serum (FBS), normal saline, or cell medium, the water contact angles were significantly reduced on the surface of HA-deposited PLLA. Chondrocyte and osteoblast showed a higher attachment and cell proliferation on HA-deposited surfaces and in particular, it was confirmed that chondrocyte was considerably influenced by HA. However, osteoblast showed better cell proliferation on the surfaces immersed in FBS, cell medium or HA-deposited surface. In addition, the cell proliferation in 3D scaffolds was much higher than that on film type, irrespective of chondrocyte and osteoblast. Therefore, such surface-modified PLLAs are expected to be useful as organic-inorganic hybrid scaffolds in the regeneration of cartilage and bone.

• Bulletin of the Korean Chemical Society
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• v.31 no.8
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• pp.2265-2271
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• 2010

In this study, wormorm-like polymeric micelles were construted from poly(L-lactic acid)-b-poly(ethyelen glycol) (PLLA-b-PEG) block copolymers via worm-like (or cylindrical) self- assembly that consisted of a relatively long PLLA block ($M_n$ 7K Daltons) at the core and a relatively short PEG block ($M_n$ 2K Daltons) as the shell. Several cancer-targeting moieties (such as folate, cobalamin, and cyclic arginine-glycine-aspartic (RGD) peptide) were chemically coupled with the succinylated or maleimided PEG block of PLLA-b-PEG to act as a cancer cell-specific targeting ligand for breast cancer. The worm-like micelles with muplite cancer cell-specific ligands proved to be successful in recognizing different breast cancer cells at once. This has the potential to aid in cancer-specific drug delivery and to be used as an effective treatment for breast cancer.

• Journal of Microbiology and Biotechnology
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• v.19 no.11
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• pp.1490-1495
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• 2009

The development of nanotechnology has penetrated the fields of biology and medicine, resulting in remarkable applications for tissue regeneration. In order to apply this technology to tissue engineering, we have developed nano-scaled 3D scaffolds consisting of growth factor-loaded heparin/poly(l-lysine) nanoparticles (NPs) attached to the surface of polymeric micro spheres via polyionic complex methods. Growth factor-loaded NPs were simply produced as polyelectrolyte complexes with diameters of 100-200 nm. They were then coated onto positively charged poly(lactic-co-glycolic acid) (PLGA) pretreated with polyethyleneimine to enable cell adhesion, proliferation, and stimulation of neurite outgrowth. Propidium iodide staining and $\beta$-tubulin analysis revealed that neuronal PC12 cells proliferated extensively, expressed significant amounts of b-tubulin, and showed well-structured neurite outgrowth on polymeric microspheres by stimulation with growth factors. These results suggest that cellular adhesion and biological functionality on prepared PLGA microspheres enabled terminal differentiation of neuronal cells.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.541-545
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• 2000

For the sustained release formulation of recombinant human growth hormone (rhGH), dissociable rhGH aggregates were microencapsulated within poly(D,L-lactic-co-glycolic acid) [PLGA] microparticles. rhGH aggregates with 2 - 3 m Particle diameter were first produced by adding a small volume of aqueous rhGH solution into a partially water miscible organic solvent phase(ethyl acetate) containing PLGA. These rhGH aggregates were then microencapsulated within PLGA polymer phase by extracting ethyl acetate into an aqueous phase pre-saturated with ethyl acetate. The resultant microparticles were 2 - 3 m in diameter similar to the size of rhGH aggregates, suggesting that PLGA polymer was coated around the protein aggregates. Release profiles of rhGH from these microparticles were greatly affected by changing the volume of the incubation medium. The release rhGH species consisted of mostly monomeric form with having a correct conformation. This study reveals that sustained rhGH release could be achieved by microencapsulating reversibly dissociable protein aggregates within biodegradable polymers.

• Archives of Plastic Surgery
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• v.41 no.1
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• pp.77-80
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• 2014

We report a case of sternal reconstruction using bilateral sternal bar turnover flaps in a 4-year-old boy with an inferior sternal cleft, as part of Cantrell's pentad. When the patient was 10 months old, he underwent sternal reconstruction using a resorbable poly-L-lactic-polyglycolic acid plate in the first stage when there was insufficient autogenous tissue to provide a reliable reconstruction. Bilateral sternal bar turnover was performed in the second stage at 4 years of age. This operative technique is described in this report. This novel technique provides a robust, dynamic, and reliable reconstruction for inferior sternal defects.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.3
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• pp.217-224
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• 2018

Thread lifting has become popular as a minimally invasive technique for facial rejuvenation. Commercially available threads are composed of poly-L-lactic acid (PLLA), polycaprolactone (PCL), or polydioxanone (PDO). However, the histological changes that occur in response to implanted threads are unclear. The aim of this study was to evaluate histological changes that occur in response to implantation with three types of bioresorbable threads (PLLA, PCL, PDO) in rat skin. PLLA, PCL and PDO threads were implanted in the dorsal skin of Sprague Dawley rats and tissue samples were harvested 2, 4, 8 and 12 weeks post-implantation. To evaluate histologic changes induced by bioresorbable face-lifting threads, tissue samples were stained with hematoxylin & eosin, Masson's trichrome stain and Herovici's collagen stain. All three threads induced neocollagenesis of type 3 collagen in the rat skin. The amount of collagen induced by the threads was dependent on the thread surface area. The PDO cavern-type thread was most effective in inducing neocollagenesis due to its extensive surface area. Our results suggest that type 3 collagen induced by bioresorbable threads depends on the thread surface area to uphold the dermis and contributes to facial rejuvenation.