• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3208-3212
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• 2012

Controlled drug delivery systems employing microparticles offer lots of advantages over conventional drug dosage formulations. Microencapsulation technique have been conducted with biodegradable polymers such as poly(lactic-co-glycolic acid) (PLGA) and poly(lactic acid) (PLA) for its adjustable biodegradability and biocompatibility. In this study, we evaluated two techniques, oil-in-water (o/w) emulsion solvent evaporation and spray drying, for preparation of polymeric microparticles encapsulating a newly synthesized drug, SS-AG20, for the long-term drug delivery of this low-molecular-weight drug with a very short half-life. Drug-loaded microparticles prepared by the solvent evaporation method showed a smoother morphology; however, relatively poor encapsulation efficiency and drastic initial burst were discovered as drawbacks. Spray-dried drug-loaded microparticles had an imperfect surface with pores and distorted portions so that its initial burst was critical (70.05-87.16%) when the preparation was carried out with a 5% polymeric solution. By increasing the concentration of the polymer, the morphology was refined and undesirable initial burst was circumvented (burst was reduced to 35.93-74.85%) while retaining high encapsulation efficiency. Moreover, by encapsulating the drug with various biodegradable polymers using the spray drying method, gradual and sustained drug release, for up to 2 weeks, was achieved.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.3066-3068
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• 2009

• Applied Chemistry for Engineering
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• v.30 no.1
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• pp.88-94
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• 2019

Triplet-triplet annihilation upconversion (TTA-UC) is a photochemical process wherein two or more low-energy photons are converted to a high-energy photon through a special energy transfer mechanism. Herein, we report a strategy to enhance the efficiency of TTA-UC through the light-scattering effect induced by silica microparticles (SM) embedded in polymeric thin films. By incorporating monodisperse uniform silica microparticles with a uniform size of 950 nm synthesized by $St{\ddot{o}}ber$-based seeded growth method into UC polymeric thin films, the UC intensity in the 430-570 nm range was enhanced by as much as 64% when irradiated by 635 nm laser. Analyzing the lifetime of PdTPBP phosphorescence revealed that the presence of SM in the UC layer does not affect triplet-triplet energy transfer (TTET) between sensitizers and acceptors, supporting the enhancement of TTA-UC originated from the light-scattering effect. On the other hand, the incorporation of SM in UC layer is shown to enhance the triplet-triplet annihilation (TTA) efficiency, which results in a 1.5-fold increase of the ${\Phi}_{UC}$, by scattering light source and thus increasing the number of excited photons to be utilized in TTA-UC process.

• 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.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.5
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• pp.126-133
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• 2015

Recently, there has been demand for polymeric porous membranes in various fields, such as environmental engineering, pharmaceutics, tissue engineering, drug delivery, biology, and fuel cells. In this study, it is proposed that a polymer particle-based porous membrane can be fabricated using electrospraying and sintering processes. Electrospraying can fabricate polymeric particles with diameters ranging from several micrometers to tens of nanometers without the cumbersome particle aggregation problem. Additionally, the particles can be sintered through thermo-compression under the glass transition temperature. In this study, a polymethyl methacrylate particle-based porous membrane with an average pore size of less than 500 nm is fabricated using the proposed method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1495-1498
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• 2003

Recently, self-healing methods of a cracked matrix, especially polymeric composite materials, became the center of engineering researchers. In this paper, we summarized the self-healing concept for polymeric composite materials and investigated the effect of microparticle on the crack growth behavior in colorless and transparent matrix by experimental observation to describe the crack propagation around the microparticle inside epoxy matrix composite. Compression splitting test for the specimen involving microparticle was conducted. In addition, FE analysis was pursued to present the stress contour around microparticle in the matrix. Through the experiments and FE analysis, we found that the size. relative position, bonding condition and relative stiffness of microparticle are important parameters to decide the direction of crack propagation, which is related to the rupture of microparticle for self-healing

• Polymer(Korea)
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• v.33 no.4
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• pp.353-357
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• 2009

Spray drying is an effective and stable process, which has been widely used to produce pharmaceutical powders. In the traditional spray drying process, it was not quite easy to control the aggregation and the size of particles. Particularly, the preparation of polymeric particles was relatively hard compared to the preparation of food and pharmaceutical ingredients, typically organic materials of small molecular weights. In this study, modification of a conventional spray dryer was tried to use electrical charge and co-axial nozzles to prepare polymeric particles. Poly(ethylene glycol) and poly (D,L-lactide-co-glycolide) were used as the inner polymeric materials, and lactose as the outer shell materials. The results showed that electrohydrodynamic spray-dried particles had a relatively uniform size and particle morphology, and the aggregation of particles could be suppressed compared to the conventional spray-dried particles. The electrohydrodynamic spray-dried powders consisted of spherical particles of $2{\sim}5{\mu}m$ diameters.

• Archives of Pharmacal Research
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• v.27 no.1
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• pp.1-12
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• 2004

Initial burst is one of the major challenges in protein-encapsulated microparticle systems. Since protein release during the initial stage depends mostly on the diffusional escape of the protein, major approaches to prevent the initial burst have focused on efficient encapsulation of the protein within the microparticles. For this reason, control of encapsulation efficiency and the extent of initial burst are based on common formulation parameters. The present article provides a literature review of the formulation parameters that are known to influence the two properties in the emulsion-solvent evaporation/extraction method. Physical and chemical properties of encapsulating polymers, solvent systems, polymer-drug interactions, and properties of the continuous phase are some of the influential variables. Most parameters affect encapsulation efficiency and initial burst by modifying solidification rate of the dispersed phase. In order to prevent many unfavorable events such as pore formation, drug loss, and drug migration that occur while the dispersed phase is in the semi-solid state, it is important to understand and optimize these variables.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.43 no.1
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• pp.11-18
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• 2017

An anti-aging compound ethyl (4-(2,3-dihydro-1H-indene-5-carboxyamido) benzoate) rapidly crystallizes in emulsion systems, and a flavonoid 3,5,7-trihydroxy-4'-methoxy-8-prenylflavone bearing a whitening function causes coloration of cosmetic compounds when mixed with metal oxides. In this study, an electrospray method was used to encapsulate water-insoluble bioactive compounds in polymeric microparticles. Poly (methyl methacrylate) and polycaprolactone were used to encapsulate ethyl (4-(2,3-dihydro-1H-indene-5-carboxyamido) benzoate) and 3,5,7-trihydroxy-4'-methoxy-8-prenylflavone, respectively. It was found that polymer concentration, the structure of electrospray nozzle, and compatibility between polymers and bioactive compounds were important factors in the preparation of the particles. Polycaprolactone particles encapsulating 3,5,7-trihydroxy-4'-methoxy-8-prenylflavone was effective in preventing coloration of a cosmetic compound when mixed with metal oxides.

• Journal of Pharmaceutical Investigation
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• v.37 no.6
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• pp.349-354
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• 2007

For decades, the various virtues of ${\alpha}-lipoic$ acid (ALA), a natural material synthesized in most cells, have been intensively studied and proved. Recently it was reported that ALA caused significant bodyweight reduction via appetite suppression. Unfortunately, the efficacy requires an administration over 50 mg/kg. The low bioavailability and the short plasma half life of ALA lead us to explore novel pharmaceutical dosage forms using nanoparticles. In this study, the effect of polymeric stabilizers on the bioavailability improvement of ALA nanoparticles was investigated. The reduction of particle size via nano-comminution technology was successful resulting in volume average particle sizes of 320 - 340 nm. The in vitro release rate of ALA did not reflect the decrease of particle size, possibly because of the self polymerization of ALA during nano-comminution. The type of polymeric stabilizers could not affect the release rate either. However, the in vivo food intake results of ALA showed that nano-suspensions were more effective than microparticles or a salt form. The nano-suspension containing polyvinyl pyrrolidone as the primary stabilizer and polyacrylic acid as the secondary stabilizer showed more improved efficacy for 2 hours.