• Title, Summary, Keyword: Poly(l-lactide)

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Bending and Compressive Properties of Crystallized TCP/PLLA Composites

  • Kobayashi, Satoshi;Sakamoto, Kazuki
    • Advanced Composite Materials
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    • v.18 no.3
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    • pp.287-295
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    • 2009
  • $\beta$-Tricalcium phosphate ($\beta$-TCP) particles reinforced bioresorbable plastics poly-L-lactide (PLLA) composites were prepared by injection molding. The nominal weight ratio of $\beta$-TCP was selected as 5, 10 and 15%. In order to clarify effects of the PLLA crystallinity on the mechanical properties, the specimens were heat treated isothermally. Results of differential scanning calorimetry indicated that the PLLA crystallinity increased with increasing heat treatment temperature. Bending and compressive tests were conducted on the specimen with different $\beta$-TCP contents and crystallinities. The results show that the bending and compressive moduli increased with increasing $\beta$-TCP contents and crystallinity. On the other hand, bending strength decreased with increasing $\beta$-TCP contents. Maximum bending strength was obtained at the heat treatment of $70^{\circ}C$ for 24 h, whereas compressive 0.2% proof strength increased with increasing heat treatment temperature. This difference is attributed to the difference in the microscopic damages.

pH-Induced Micellization of Biodegradable Block Copolymers Containing Sulfamethazine

  • Shim, Woo-Sun;Lee, Jae-Sung;Lee, Doo-Sung
    • Macromolecular research
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    • v.13 no.4
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    • pp.344-351
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    • 2005
  • pH-sensitive block copolymers were synthesized by coupling reaction of sulfamethazine and amphiphilic diblock copolymer, and their micellization-demicellization behavior was investigated. Sulfamethazine (SM), a derivative of sulfonamide, was introduced as a pH responsive moiety while methoxy poly(ethylene glycol)poly(D,L-lactide) (MPEG-PDLLA) and methoxy poly(ethylene glycol)-poly($D,L-lactide-co-{\varepsilon}-caprolactone$) (MPEG-PCLA) were used as biodegradable amphiphilic diblock copolymers. After the sulfamethazine was carboxylated by the reaction with succinic anhydride, the diblock copolymer was conjugated with sulfamethazine by coupling reaction in the presence of DCC. The critical micelle concentration (CMC) and mean diameter of the micelles were examined at various pH conditions through fluorescence spectroscopy, dynamic light scattering and transmission electron microscopy. For MPEG-PDLLA-SM and MPEG-PCLA-SM solutions, the pH-dependent micellization-demicellization was achieved within a narrow pH band, which was not observed in the MPEG-PDLLA and MPEG-PCLA solutions. The micelle showed a spherical morphology and had a very narrow size distribution. This pH-sensitive block copolymer shows potential as a site-targeted drug carrier.

Doxorubicin Release from Core-Shell Type Nanoparticles of Poly(DL-lactide-co-glycolide)-Grafted Dextran

  • Jeong, Young-Il;Choi, Ki-Choon;Song, Chae-Eun
    • Archives of Pharmacal Research
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    • v.29 no.8
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    • pp.712-719
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    • 2006
  • In this study, we prepared core-shell type nanoparticles of a poly(DL-lactide-co-glycolide) (PLGA) grafted-dextran (DexLG) copolymer with varying graft ratio of PLGA. The synthesis of the DexLG copolymer was confirmed by $^1H$ nuclear magnetic resonance (NMR) spectroscopy. The DexLG copolymer was able to form nanoparticles in water by self-aggregating process, and their particle size was around $50\;nm{\sim}300\;nm$ according to the graft ratio of PLGA. Morphological observations using a transmission electron microscope (TEM) showed that the nanoparticles of the DexLG copolymer have uniformly spherical shapes. From fluorescence probe study using pyrene as a hydrophobic probe, critical association concentration (CAC) values determined from the fluorescence excitation spectra were increased as increase of DS of PLGA. $^1H-NMR$ spectroscopy using $D_2O$ and DMSO approved that DexLG nanoparticles have core-shell structure, i.e. hydrophobic block PLGA consisted inner-core as a drug-incorporating domain and dextran consisted as a hydrated outershell. Drug release rate from DexLG nano-particles became faster in the presence of dextranase in spite of the release rate not being significantly changed at high graft ratio of PLGA. Core-shell type nanoparticles of DexLG copolymer can be used as a colonic drug carrier. In conclusion, size, morphology, and molecular structure of DexLG nanoparticles are available to consider as an oral drug targeting nanoparticles.

Evaluation of the Stability of Biodegradable Nanoparticle with Time via Particle Size Measurement (입자 크기 측정을 통한 생분해성 나노입자의 시간에 따른 분산 안정성 평가)

  • Cho, Kuk-Young;Yim, Jin-Heong;Park, Jung-Ki;Lee, Ki-Seok
    • Polymer Korea
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    • v.32 no.3
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    • pp.246-250
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    • 2008
  • Colloidal stability of the biodegradable nanoparticle was characterized by measuring the variation of particle size with time using photon correlation spectroscopy. Three kinds of polymers, namely, poly(D,L-lactide-co-glycolide)(PLGA), PLGA/poly(L-lactide) blends, and PLGA/poly(L-lactide)-g-poly(ethylene glycol) blends were used as matrix material for nanoparticle preparation. Nanoparticles were prepared with or without using poly(vinyl alcohol)(PVA) as suspension stabilizer to evaluate the condition of preparation. Nanoparticles from the blend of amphiphilic graft copolymer with short poly(ethylene glycol) chain and PLGA maintained suspension for 1 day when protein stock solution was introduced. This is somewhat improvement in colloidal stability against protein adsorption compared with that of nanoparticles without PEG moiety. Suspension stabilizer, PVA, had a significant effect on the colloidal stability against freezing and protein adsorption which led to coagulation of nanoparticles. It is important to consider effect of suspension stabilizer as well as materials used to prepare nanoparticle on the colloidal stability.

Surface Modification of Poly(L-lactide-co-ε-caprolactone) Nanofibers by Electron-beam Irradiation (전자선 조사 방법을 통한 생분해성고분자의 표면개질 특성 평가)

  • Kim, Woo-Jin;Shin, Young Min;Park, Jong-Seok;Gwon, Hui-Jeong;Nho, Young-Chang;Lim, Youn-Mook
    • Journal of Radiation Industry
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    • v.5 no.4
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    • pp.365-370
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    • 2011
  • Electrospun nanofibers prepared with synthetic biodegradable polymer have some limitations in regulating adhesion, proliferation, and spreading of cells because of their surface hydrophobicity and absence of cell-interaction. In this study, we functionalized the electrospun poly(L-lactide-co-${\varepsilon}$-caprolactone) (PLCL) nanofibers with acrylic acid (AAc) to modulate their surface hydrophilicity using electron-beam irradiation method and then measured grafting ratio of AAc, water contact angle, and ATR-FTIR of AAc-grafted nanofibers. A grafting ratio of AAc on the nanofibers was increased as irradiation dose and AAc concentration were increased. AAc-grafted nanofibers also have higher wettability than non-modified nanofibers. In conclusion, those surface-modified nanofibers may be an essential candidate to regulate cell attachment in tissue engineering applications.

Isolation of a Poly (L-lactide) Degrading Bacterium and Improvement of its Degradation Capacity (Poly(L-lactide)분해 세균의 분리 및 활성 증진)

  • Kim, Mal-Nam;Park, Sang-Tae
    • Korean Journal of Environmental Biology
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    • v.25 no.3
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    • pp.260-266
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    • 2007
  • A thermophilic bacterium capable of poly (L-lactide)(PLLA) degradation was isolated from cultivating soil in Korea. The isolate was Gram positive rod-shaped bacterium, and was identified as Geobacillus caldoxylosilyticus based on the 16S rDNA sequence analysis. The strain proved to be a new PLLA degrading bacterium which has not been reported in the open literatures yet. The degradation activity of the strain was assessed in a sterilized compost inoculated with the strain under controlled compost condition at $58^{\circ}C$ for 40 days. The strain mineralized 66%, 57%, 41% and 40% of PLLA5000, PLLA11000, PLLA34000 and PLLA256000 whose weight average molecular weights were 5000, 11000, 34000 and 256000, respectively. Incorporation of 0.1% each of gelatin, yeast extract and ammonium sulfate in the compost containing PLLA256000 as a nutritional supplement raised the biodegradation activity by 27%, 13% and 10%, respectively. Increase of the inoculum size from $10^9cfu\;g^{-1}\;to\;10^{10}cfu\;g^{-1}\;and\;10^{11}cfu\;g^{-1}$ also enhanced the biodegradation activity by 14% and 20%, respectively.

Metal Surface Coating Using Electrospray of Biodegradable Polymers and $\alpha$-Lipoic Acid Release Behavior for Drug-Eluting Stents (생분해성 고분자의 전기분사를 이용한 약물방출 스텐트용 금속표면 코팅 및 ALA방출 거동)

  • Kim, Dong-Min;Lee, Bong-Soo;Park, Cheol-Ho;Park, Kwi-Deok;Son, Tae-Il;Jeong, Myeong-Ho;Han, Dong-Keun
    • Polymer Korea
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    • v.34 no.2
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    • pp.178-183
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    • 2010
  • Medical metal stents inserted to patients with a cardiovascular disease associated with coronary artery system have relatively increased the survival rate. The development of new stents is, however, urgently required due to restenosis and late thrombosis generated in metal stents. To solve these problems, the biodegradable polymers such as poly(lactide-co-glycolide) (PLGA), poly(L-lactide)(PLLA), and poly ($\varepsilon$-caprolactone)(PCL) were mixed with alpha lipoic acid (ALA), which is well known to inhibit the proliferation of neointimal hyperplasia. Subsequently, the ALA-loaded polymers were coated on stainless steel by electrospray. The drug-eluting behaviors from the coated polymers were investigated according to kinds and concentrations of polymers, spray rates, and kinds of solvents. The drug-eluting rate from PCL with the lowest glass transition temperature was the fastest among three polymers and followed by PLGA and PLLA. The surface roughness increased as the spray rate was increased and also the drug-eluting rate was affected by kinds of solvents with different boiling point. It is expected that drug-eluting stent (DES) coated with ALA-loaded polymers can be applied practically for clinical applications by controlling the behavior of drug release.

Anti-thrombogenicity and Surface Structure of a Poly(ester-ether) Consisting of Poly(L-lactic acid) and Poly(oxyethylene-co-oxypropylene) (Poly(L-lactic acid)와 Poly(oxyethylene-co-oxypropylene)을 포함한 생분해성 Poly(ester-ether)형 블록 공중합체의 항혈전성과 표면구조)

  • 이찬우;문성일;홍영기
    • Polymer Korea
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    • v.25 no.3
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    • pp.385-390
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    • 2001
  • The A-B-A type block copoly(ester-ether)s consisting of poly(L-lactic acid) (PLLA)(A) and poly(oxyethylene-co-oxypropylene)(B) were prepared to improve the mechanical properties and hydrolyzability of PLLA. The block copolymers showed an improved flexibility due to the incorporation of the soft segments. Then, the same copolymer has an improved anti-thrombogenicity probably due to the specific microphase separation structure in the surface. The AFM of the film of the block copolymer revealed that the surface was quite flat in comparison with that of PLLA. Therefore, the flatness of the surface may be related with the increased anti-thrombogenicity of the copolymer film.

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Control of Enzymatic Degradability of Biodegradable Polylactide by Blending with Non-degradable Polymers (비 분해성고분자와 블렌드를 이용한 생분해성 폴리유산의 효소분해속도 조절)

  • Jang, Seong-Ho;Park, Sang-Bo;Lee, Won-Ki
    • Journal of Environmental Science International
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    • v.19 no.9
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    • pp.1161-1167
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    • 2010
  • The effects of addition of non degradable polymers, polystyrene (PS) and poly(methyl methacrylate) (PMMA) on the rate of enzymatic degradation of biodegradable poly(l-lactide) (PLLA) have been studied in term of surface structure. Since a component in multicomponent polymeric system has shown surface enrichment, PS and PMMA which have lower surface energy than PLLA were selected as a minor blend component (5 wt%). Enzymatic degradation was carried out at $37^{\circ}C$ and pH 8.5 in the aqueous solution of Proteinase K. Two blend systems, partially miscible (PS/PLLA) and immiscible (PMMA/PLLA), showed the surface enrichment of 4 and 2 times of PS and PMMA, respectively. From the weight loss profile data, the slow degradation rate of both blend films was observed. This indicates that PS or PMMA domains which exist at surface act as a retardant of enzymatic attack.

Interaction of Fibroblast Cell onto Physicochemically Treated PLGA Surfaces (물리화학적 처리된 PLGA 표면의 섬유아세포와의 상호작용)

  • 강길선;이상진;전주형;이진호;이배방
    • Polymer Korea
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    • v.24 no.6
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    • pp.869-876
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    • 2000
  • In order to improve the cell-compatability of poly(L-lactide-co-glycolide) (75 : 25 by mole ratio of lactide to glycolide, PLGA) surfaces, the physicochemical treatments have been demonstrated. Chemical treatments were 70% perchloric acid. 50% sulfuric acid and 0.5 N sodium hydroxide solution and physical methods were corona and plasma treatment. The water contact angle of surface treated PLGA decreased from 73$^{\circ}$ to 50~60$^{\circ}$, i.e., increased hydrophilicity, due to the introduction of oxygen-containing functional group onto PLGA backbone by the measurement of an electron spectroscopy for chemical analysis. It could be observed that the adhesion and growth of fibroblast cell on physicochemically treated PLGA surfaces, especially perchloric acid treated PLGA surface, were more active than on the controt. In conclusion, it seems that surface wettability as hydrophilicity of PLGA plays an important role in cell adhesion, spreading and growth.

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