• Elastomers and Composites
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• v.49 no.1
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• pp.13-23
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• 2014

In this work, glycolide, L-lactide and ${\varepsilon}$-caprolactone monomers were polymerized into the triblock copolymers by two step polymerization method and their non-isothermal crystallization behaviors were studied by combination of modified Avrami and Ozawa formula for further analysis of their behaviors. The result showed that PGCLA21 gave the highest value for supercooling analysis and super cooling degree increased with L-lactide content. Crystallization velocity constant, however, showed no significant change. The result of cooling function in specific relative crystallization degree showed that the increase of L-lactide content made an effect on the more enhancement of crystallization velocity of the PGCLA than PGCL. The result of big logF(T) value with the L-lactide content above critical point for PGCLA41 and PGCLA21 showed that bigger cooling velocity needed to gain same crystal size compared with PGCL. This means that it gives negative effect in the increase of crystallization velocity.

• Journal of the Korean Chemical Society
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• v.42 no.1
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• pp.92-98
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• 1998

Poly(DL-lactide-co-glycolide) (80:20) was synthesized from DL-lactide and glycolide, and the copolymers was made to micelles containing clonazepam for drug delivery system. The release experiments of the drug from micelles were operated at pH 7.4 phosphate buffer solution $37.0{\pm}0.05^{\circ}C$. The linearly-releasing time ranges of the drug from micelles prepared with the copolymer/drug weight ratio of 20:40, 20:20, and 40:20 (mg) were 50, 41, and 29 days, respectively. So the linearly-releasing time of drug showed the order of micelles 20/40 > micelles 20/20 > micelles 40/20. In short, the formulation allows polymeric micelles to suppress the burst effect of the drug release mechanism, which led to the controlled release pattern and the possibility of drug delivery system for veinous injection.

• Macromolecular Research
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• v.17 no.12
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• pp.1010-1014
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• 2009

Monodispersed microparticles with a poly(D,L-lactide-co-glycolide) (PLGA) core and a poly(ethyl 2-cyanoacrylate) (PE2CA) shell were prepared by Shirasu porous glass (SPG) membrane emulsification to reduce the initial burst release of doxorubicin (DOX). Solution mixtures with different weight ratios of PLGA polymer and E2CA monomer were permeated under pressure through an SPG membrane with $1.9\;{\mu}m$ pore size into a continuous water phase with sodium lauryl sulfate as a surfactant. Core-shell structured microparticles were formed by the mechanism of anionic interfacial polymerization of E2CA and precipitation of both polymers. The average diameter of the resulting microparticles with various PLGA:E2CA ratios ranged from 1.42 to $2.73\;{\mu}m$. The morphology and core-shell structure of the microparticles were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The DOX release profiles revealed that the microparticles with an equivalent PLGA:E2CA weight ratio of 1:1 exhibited the optimal condition to reduce the initial burst of DOX. The initial release rate of DOX was dependent on the PLGA:E2CA ratio, and was minimized at a 1:1 ratio.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.550-553
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• 2000

The polymeric matrices made with poly(D,L-lactide-co-glycolide) were prepared using copolymer of poly(D,L-lactide) and poly(ethylene glycol) for application of drug delivery systems. Catalyst made use of stannous actoate. Particle size were differ greatly$(435.3{\pm}11.2{\sim}2284.1{\pm}188.5)$ that nanoparticle made use of according to solvent of various kinds. Polymer could a sharp distinction with copolymerized among LE-1, LE-2 and LE-3 of PLA and PEG of content that to examine $^1H-NMR$ of copolymer make refine and reprecipitation. Drug delivery effect at PLGA nanoparticle : PLA amount more then proved highly drug delivery amount that each LE-1, LE-2, LE-3, drug and solvent was 40mg, 20mg and 10mg. Drug delivery effect proved higher 20mg that change(10mg, 20mg, 40mg) at drug feeding amount with LE-2. The first a lot of drug proved delivery. LE-3 most lactide content proved much delivery since biodegradable on PLGA copolymer result from lactide. Also biodegradable rate was highest at LE-3 much of lactide content, because influence at biodegradable effect of lactide by inclusive of soft PEG.

• Journal of Biomedical Engineering Research
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• v.13 no.2
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• pp.147-154
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• 1992

Poly (glycolic aclu-co-glycine-L-lactic aclu) has been prepared by rlng opening polymerlzation. The monomer 6-methyl morpholine-2, 5-dlone was synthe-slzed by bromoproplonylation of 2 bromopropionyl bromide with glycine. Glycolide and 6-methyl morpholine-2, 5-dione have been used as starling materials for polydepsipeptides. The synthesized copolymers have been Identlrled by NMR and FT-lR spectrophotometer. The Tg value of poly(glycollc aclu-co glycine-L-tactic acld ) Is In creased with increasing mole fraction of 6-methylmorpholine-2, 5-dlone(60-$84^{\circ}C$). The glass trasltion temperature of poly(glycolic acid-co-glycine-L-lactic-acid) (62-$86^{\circ}C$) is lower than that of poly (L-lactic acrid-co-glycine-L-lactic acid ). The thermal degradation of poly( L-lactic acid-co- glycine-L-lactic acid ) Is decreased with increasing mole fraction of L-lactide. The thermal degrada pion of poly(glycolic acrid-co-91ycine-L-lactic aclu ) is increased with increasing mole Fraction of glycolide.

• Archives of Pharmacal Research
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• v.16 no.4
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• pp.312-317
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• 1993

To confirm a new evaluation tedhnique for biodegradability of biopolymer microsphers in vivo condition, magnetic microsphere sytem was adopted for tracing the microspheres injected and lodged in micr. Microsphers of poly(DL-lactic acid), poly(L-alctic acid) and poly(DL-lactide-coglycolide)(PLGA) were prepared by solvent-extraction method and their organ distribution and biodegradation in mice was examined. Magnetic microspheres lodged in mice organs were recollected from the homogenates of mice organs with a constant flow magnetic separation apparatus. Recollected microspheres were observed by scanning electron microscopy and also were assayed for their magnetite ocntent by atomic absorption spectrophotometry to evaluate the biodegradability of polymeric microspheres. This method seems to be practical and simple to estimate the biodegradability of biopolymers over the conventional methods.

• Polymer(Korea)
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• v.28 no.4
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• pp.328-334
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• 2004

A series of methoxy poly(ethylene glycol) (MPEG)-poly(L-lactide-co-glycolide) (PLGA) diblock copolymers were synthesized by ring-opening polymerization of L-lactide and glycolide with carbitol (134 g/mole) or different molecular weights of MPEG (550, 2000, and 5000 g/mole) as an initiator in presence of Sn(Oct)$_2$. The properties of diblock copolymers were characterized by using $^1$H-NMR, GPC, and XRD. After uniform mixing of block copolymers and 1% albumin bovine-fluorescein isothiocyanate(FITC-BSA) with a freeze miller, the wafers loaded FITC-BSA were fabricated by using a mold with a dimensions of 3 mm${\times}$1mm diameter. The release profiles of FITC-BSA and the pH changes of wafer were examined using pH 7.4 PBS for 30 days at 37$^{\circ}C$. The release profiles of albumin showed fast initial burst as the molecular weights of MPEG increased. As a result of this study, the release behavior of BSA was controlled with introducing MPEG in the block copolymers.

• Polymer(Korea)
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• v.25 no.6
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• pp.884-892
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• 2001

Biodegradable wafers were prepared with poly (L-lactide-co-glycolide) (50 : 50 mole ratio of lactide to glycolide, molecular weight:5000 g/mole) by direct compression method for the sustained release of nifedipine to investigate the possibility of the treatment of hypertension. PLGA wafers were prepared by altering initial drug/polymer loading ratio, wafer thickness, and hydroxypropyl methylcellulose (HPMC) content. These wafers showed new zero-order release patterns for 11 days, and various biphasic release patterns could be obtained by altering the composition of wafers such as addition of matrix binder as HPMC to the PLGA wafer to reduce release rate of initial phase. The onset of polymer mass loss only occured after 4 days and about 40% of mass loss was observed after 11 days nifedipine release. This system had advantages in terms of simplicity in design and obviousness of drug release rate and may be useful as an implantable dosage form.

• Polymer(Korea)
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• v.24 no.4
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• pp.505-512
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• 2000

The mixture density data for poly(lactide-co-glycolide) [PLGA] with supercritical $CO_2$, CHF$_3$ and CHClF$_2$ were obtained in the temperature range of 27 to 10$0^{\circ}C$ and at pressures as high as 3000 bar (PLGA$_{x}$, Where the molar concentration of glycolide in the backbone, x, range from 0 to 50 mol%). The PLA-$CO_2$, PLA-CHF$_3$, and PLA-CHClF$_2$ systems dissolve in the pressure less than 1430 below 700, and below 100 bar, respectively. The mixture density shows from 1.084 to 1.334 g/cm$^3$ at temperatures from 27 to 93$^{\circ}C$. The PLGA$_{15}$ -$CO_2$ mixture dissolves at pressures of below 1900 bar and the mixture density is in the range of 1.158 to 1.247 g/cm$^3$ at temperatures between 37 and 92$^{\circ}C$. The solubilities of the PLGA$_{25}$ for $CO_2$, CHF$_3$, and CHClF$_2$ are shown to pressure as high as 2390, 1470, and 118 bar, respectively, and the mixture density exhibits iron 1.154 to 1.535 g/cm$^3$ at temperatures from 29 to 81$^{\circ}C$. The PLGA$_{50}$-$CO_2$ system does not dissolve at 24$0^{\circ}C$ and 3000 bar while the PLGA$_{50}$-CHCIF$_2$ does easily at 5$0^{\circ}C$ and 100 bar. The mixture density for the PLGA-CHClF$_2$ system increases even at low pressures as the glycolide molar concentration increases.es.es.

• 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.