• Polymer Science and Technology
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• v.21 no.1
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• pp.41-44
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• 2010

• Proceedings of the PSK Conference
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• 2000.04a
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• pp.216.2-216.2
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• 2000

• Membrane Journal
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• v.24 no.2
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• pp.113-122
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• 2014

Porous poly(L-lactic acid)(PLLA) scaffold membranes were prepared via. phase separation process. Chloroform, dichloromethane and 1,4-dioxane were used as solvent and, ethyl alcohol was used as non-solvent. Morphologies, mechanical properties and mass transfer characteristics of the scaffold membranes were investigated through SEM, stress-strain test and glucose diffusion test. The scaffold membranes obtained from the casting solutions with chloroform and with dichloromethane showed similar morphologies. They showed sponge-like porous structure with the pore size in the range of $3-10{\mu}m$ and, their porosities were in 50-80% range. Using 1,4-dioxane as solvent, nano-fibrous scaffold membranes with porosities over 80% were fabricated. When the polymer content in the solution with 1,4-dioxane was lowered to 4%, highly porous, macroporous and nano-fibrous scaffold membranes were obtained. The size of the macropore was tens of the microns and the porosity was around 90%. These results indicate that the solvent has significant effect on the scaffold membrane structure and, that scaffold membranes with various structures can be fabricated through phase separation method by choosing solvent and by controlling polymer concentration in the casting solution.

• Membrane Journal
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• v.25 no.1
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• pp.48-59
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• 2015

This paper reports a fabrication of poly(L-lactic acid) (PLLA) scaffold membranes through phase separation process using pure and mixed solvents. Chloroform and 1,4-dioxane were used as pure solvents and mixed solvents were obtained by mixing the pure solvents together. Morphologies, mechanical properties and mass transfer characteristics of the scaffold membranes were investigated through SEM, stress-strain test and glucose diffusion test. Scaffold membranes from the solution with pure chloroform showed solid-wall pore structure. In contrast, nano-fibrous membranes were fabricated from the solution with pure 1,4-dioxane. In case of mixed solvents, the scaffold membranes showed various structures with changing composition of the solvents. When 1,4-dioxane content was lower than 20 wt% in the solvent, scaffold membrane showed solid-wall pore structure. When the content was 20 wt%, scaffold membranes with macropores with the maximum size of $100{\mu}m$ was obtained. In the concentration range of 1,4-dioxane over 25 wt%, the scaffold membranes showed nano-fibrous structures. In this range, the fibers showed different diameters with changing composition of the solvent. The minimum fiber diameter was about $15{\mu}m$, when 1,4-dioxane composition was 80 wt%. These results indicate that the composition of the solvent showed a significant effect on the structure of scaffold membrane.

• Journal of Korean Neurosurgical Society
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• v.64 no.6
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• pp.853-863
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• 2021

Objective : Biodegradable poly-L-lactic acid (PLLA) with a highly biocompatible surface via tantalum (Ta) ion implantation can be an innovative solution for the problems associated with current biodegradable stents. The purpose of this study is to develop a Taimplanted PLLA stent for clinical use and to investigate its biological performance capabilities. Methods : A series of in vitro and in vivo tests were used to assess the biological performance of bare and Ta-implanted PLLA stents. The re-endothelialization ability and thrombogenicity were examined through in vitro endothelial cell and platelet adhesion tests. An in vivo swine model was used to evaluate the effects of Ta ion implantation on subacute restenosis and thrombosis. Angiographic and histologic evaluations were conducted at one, two and three months post-treatment. Results : The Ta-implanted PLLA stent was successfully fabricated, exhibiting a smooth surface morphology and modified layer integration. After Ta ion implantation, the surface properties were more favorable for rapid endothelialization and for less platelet attachment compared to the bare PLLA stent. In an in vivo animal test, follow-up angiography showed no evidence of in-stent stenosis in either group. In a microscopic histologic examination, luminal thrombus formation was significantly suppressed in the Ta-implanted PLLA stent group according to the 2-month follow-up assessment (21.2% vs. 63.9%, p=0.005). Cells positive for CD 68, a marker for the monocyte lineage, were less frequently identified around the Ta-implanted PLLA stent in the 1-month follow-up assessments. Conclusion : The use of a Ta-implanted PLLA stent appears to promote re-endothelialization and anti-thrombogenicity.

• Journal of Pharmaceutical Investigation
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• v.39 no.3
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• pp.167-171
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• 2009

Poly(lactic-co-glycolic acid) (PLGA) microspheres have been a useful tool as a controlled drug delivery system for peptides and proteins. Recently, porous microspheres have gained great attention as inhalation drug delivery system due to their low aerodynamic densities. Here, we report highly porous PLGA microspheres, which were prepared by using a single o/w emulsification/solvent evaporation method. Two types of porogen, i.e., (i) extractable Pluronic F127 and (ii) gas foaming salt of ammonium bicarbonate, were used to induce pores on the surface of PLGA microspheres. The respective preparation conditions on dp/cp ratio and porogen concentration were determined by the previous preliminary experiments, and other preparation factors were further optimized on the basis of PLGA Mw and porogen type. The morphological features examined by scanning electron microscope (SEM) show these porous microspheres have highly porous surface structure with a diameter range of 20${\sim}$30 ${\mu}$m. These highly porous PLGA microspheres, which have much lower density, would be a practical aerosol system for pulmonary drug delivery.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1465-1470
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• 2011

In this study, a poly(lactic-co-glycolic acid) (PLGA) microspheres was fabricated using emulsion solvent evaporation technique. During the procedure fabrication, some parameters process have effected on the formation of micro-carriers. The structure and morphology of micro-carriers were evaluated by SEM observation. Beside, heparin incorporated into microspheres was determined using toluidine blue method. Specifically, the effects of some parameters process such as ultrasonic levels, PLGA concentrations and freeze-dry times on the size, structure, porous formation and heparin entrapment of micro-carriers were studied carefully. We found that, the morphology and structure of carriers were influenced by the all above parameters. The diameter of the carriers varied from 20 to 400 ${\mu}M$ depending on experimental conditions. At suitable freeze-dry time, the pores were automatically formation on surface of microspheres with a significantly in the numbers of pore. After heparin incorporated porous PLGA microspheres, it was suggested that the highly heparin incorporated into porous PLGA microspheres could enhance of angiogenesis for tissue regeneration easily.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2489-2493
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• 2012

A new fluorescent system (acridine/RTIL hybrid gel) confined in the 3D micro-structure of a poly(lactic acid) membrane were prepared from 1-butyl-3-methylimidazolium-based ionic liquids ([bmim]X (X = $SbF_6$, $NTf_2$, Cl); RTILs), poly(lactic acid) (PLA), and acridine via the sol-gel route. SEM images showed that, in the presence of [bmim]$SbF_6$ and [bmim]$NTf_2$, 3D-ly paticulated structures were created inside the PLA membranes and acridine/RTIL hybrid gels were confined in gabs of particulates. However, the use of [bmim]Cl induced the formation of a 3D-ly porous structure containing the hybrid gel of acridine/[bmimCl in the micropores. The three fluorescent systems exhibited different fluorescence behaviors (fluorescence maximum and intensity) depending on the C2-H acidity scale of the RTILs (or their anion type). Acridine gels hybridized with [bmim]$SbF_6$ and [bmim]$NTf_2$ showed blue fluorescence with relative high intensity, whereas the hybrid gel with [bmim]Cl exhibited almost no fluorescence under dry conditions. However, the acridine/[bmim]Cl hybrid system in the micro-porous PLA membrane started to emit fluorescent light under humid conditions and showed a possible response, indicating that it could be applied as a humidity sensor.

• Journal of Microbiology and Biotechnology
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• v.27 no.4
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• pp.768-774
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• 2017

Horseradish peroxidase (HRP) catalyzes the oxidation of aromatic compounds by hydrogen peroxide via insoluble polymer formation, which can be precipitated from the wastewater. For HRP immobilization, poly(lactic-co-glycolic acid) (PLGA) fine carrier supports were produced by using the Nano Spray Dryer B-90. Immobilized HRP was used to remove the persistent 2,4-dichlorophenol from model wastewater. Both extracted (9-16 U/g) and purified HRP (11-25 U/g) retained their activity to a high extent after crosslinking to the PLGA particles. The immobilized enzyme activity was substantially higher in both the acidic and the alkaline pH regions compared with the free enzyme. Optimally, 98% of the 2,4-dichlorophenol could be eliminated using immobilized HRP due to catalytic removal and partly to adsorption on the carrier supports. Immobilized enzyme kinetics for 2,4-dichlorophenol elimination was studied for the first time, and it could be concluded that competitive product inhibition took place.

• Journal of the Korean Society of Radiology
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• v.13 no.7
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• pp.909-916
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• 2019

Radiation therapy of oral and head and neck cancers often involves skin in the therapeutic range, and the use of bolus is frequently used. Dose irregularities provide dose uncertainty in patient application. In this study, the physical properties of patients with gel bolus, poly lactic acid (PLA), and silicon using 3D printing were fabricated. Dose uncertainties arising from the actual radiation dose delivery were measured. As a result, PLA bolus was stable in the Common irregularities. Silicon bolus may be useful for patients with severe irregularities or frequent changes in patient's body shape.