• Journal of Veterinary Clinics
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• v.19 no.2
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• pp.228-235
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• 2002

Mastitis is the most costly disease results in lost milk production, decreased milk quality, milk discard, early culling of cows, drug costs and labor costs in dairy cow. Until now, a antibiotic administration at the end of lactation, dry cow therapy has been known the most effective and widely used mastitis control method. However, dry cow therapy do not control a new infection in the late dry and prepartum period because dry cow products have only persistent activity in the early dry period. Therefore, this study was conducted to evaluate clinical effect of sustained released biodegradable cephalexin microsphere using PLGA in bovine mastitis control during dry period. PLGA has been approved as controlled drug release system because of non-toxic, non-tissue reactive and bioerodible characteristics. This study revealed that cephalexin microsphere had a spherical shape with characteristic porous structure on the surface. Also, in vitro drug release studies are clearly observed that the release rate of cephalexin from PLGA microsphere decrease during the first 21 days after initial burst and then increase again between 3 and 4 weeks showing pulsatile releasing pattern. On the other hand, as tried in field the new infection rate, cure rate and mean SCC after parturition in cephalexin microsphere infused group were significantly differenced as compared to the control group. Accordingly, a sustained release of cephalexin from a biodegradable microsphere could make dry cow therapy more efficiently by preventing a new infection and decreasing the number of existing infection of mammary gland during dry period.

• Polymer(Korea)
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• v.29 no.5
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• pp.468-474
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• 2005

PLGA and PCL copolymers initiated by carbitol as drug carriers were synthesized by ring-opening polymerization of L-lactide (LA), glycolide (GA), and $\varepsilon-caprolactone(\varepsilon-CL)$. Implantable wafers were simply fabricated by direct compression method after physical mixing of copolymers and bovine serum albumin-fluorescein isothiocyanate (BSA-FITC) as a model protein drug. The release amounts of BSA-FITC from wafers were determined by fluorescence intensity using the fluorescence spectrophotometer. Also, the release behavior of BSA-FITC on wafers was controlled by adding the additives such as collagen, small intestinal submucosa (SIS), poly(vinyl pyrrolidone) (PVP), and poly(thylene glycol) (PEG). The wafer prepared by PLGA and PCL exhibited slow release within $10\%$ for 30 days. But, those prepared by a variety of additives exhibited the controlled BSA release patterns with a dependence on the additive contents. furthermore, the wafers containing natural materials such as collagen and SIS showed more zero-order release profile than that with synthetic materials such as PVP and PEG. It was confirmed that the release of BSA from implantable wafers could be easily controlled by adding natural additives.

• Polymer(Korea)
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• v.38 no.2
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• pp.164-170
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• 2014

This study was designed to find an appropriate biomaterial to proliferate Schwann cell (SC). Poly(lactic-co-glycolic acid) (PLGA) films mixed with demineralized bone particle (DBP), small intestine submucosa (SIS), and silk were fabricated by a solvent casting method. Analysis of MTT, SEM and RT-PCR were performed to confirm adhesion and proliferation of SC. Contact angle of films was assayed for hydrophilicity of films. We confirmed that PLGA/DBP 20% film showed higher hydrophilicity, promoted adhesion and proliferation of SC than other films. It was concluded that PLGA/DBP film can be applied for the scaffold biomaterials for the regeneration of central nerve system.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.5
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• pp.1725-1728
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• 2015

Objective: To explore effects of paclitaxel-loaded poly lactic-co-glycolic acid (PLGA) particles on the viability of human hepatocellular carcinoma (HCC) HepG2 cells. Materials and Methods: The viability of HepG2 cells was assessed using MTT under different concentrations of prepared paclitaxel-loaded particles and paclitaxel (6.25, 12.5, 25, 50, and 100 mg/L), and apoptosis was analyzed using Hochest33342/Annexin V-FITC/PI combined with an IN Cell Analyzer 2000. Results: Paxlitaxel-loaded nanoparticles were characterized by narrow particle size distribution (158.6 nm average particle size). The survival rate of HepG2 cells exposed to paclitaxel-loaded PLGA particles decreased with the increase of concentration and time period (P<0.01 or P<0.05), the dose- and time-dependence indicating sustained release (P<0.05). Moreover, apoptosis of HepG2 cells was induced, again with an obvious dose- and time-effect relationship (P<0.05). Conclusions: Paclitaxel-loaded PLGA particles can inhibit the proliferation and induce the apoptosis of HCC HepG2 cells. This new-type of paclitaxel carrier body is easily made and has low cost, good nanoparticle characterization and sustained release. Hence, paclitaxel-loaded PLGA particles deserve to be widely popularized in the clinic.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.38.2-38.2
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• 2009

Regeration of natural tissuesor to create biological substitutes for defective or lost tissues and organs through the use of cells. In addition to cells and their porous, drugs are required to promote tissue regeneration. Therefore, the present studies were prepared using simvastatim loaded porous poly(lactide-co-glycolide) (PLGA) by double emulsion solvent evaporation water-in-oil-in-water technique (W/O/W) as drug delivery system strategies for injuring tissue. The resulting microspheres were evaluated for morphology, particle size, encapsulation efficiency, degradation of PLGA microspheres in vitro drug release and in vitro cell viability. Scanning electronic microscopic (SEM) showed that the porosities of the particles was changed by experimental conditions and cultured cells were attached well on porous microspheres surface. The X-ray diffraction (XRD) and differential scanning calometry (DSC) analysis indicate thatsimvastatim was highly dipersed in the microsphere at amorphousstate.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.141-144
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• 2000

Highly open porous polymer matrices are required for high density cell seeding, efficient nutrient, and oxygen supply to the cells cultured in the three dimensional matrices. However, there are severe problems of mass transfer limitations within the cell/scaffolds culture system. Thus we hypothesize that continuos-flow culture conditioning of cells with the scaffolds may improve the cell viability and the differentiated function. In this study, we fabricated porous PLGA scaffolds by using gas-foaming/salt-leaching method as previous described. Viscous PLGA gel paste contains ammonium bicarbonate particulates, acting as a gas-foaming agent as well as a salt-leaching porogen, were cast into Teflon mold and dried. Ammonium bicarbonate salt upon contact to an acidic aqueous solution evloves gaseous ammonia and carbon dioxide by itself. And we conjugated galactose moiety [AGA; $N-(aminobuty1)-O-{\beta}-D-galactopyranosyl-(1{\rightarrow}4)-D-glucoamide]$ to the terminal end group of a PLGA to increase the cell adhesion and matain the differentiated function of hepatocytes. Cell-seeded scaffolds were secured in a flow bioreactor chamber and exposed to continuous flow at 5 ml/min. As a result of our study, the high yield of hepatocytes attachment was accomplished by increasing the concentration of PLGA-AGA conjugate in polymer scaffolds and cells in the scaffolds under continuos flow condition maintained a high level of viability and albumin secretion rate of cultured hepatocytes showed a higher level that of control groups.

• Journal of Pharmaceutical Investigation
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• v.41 no.6
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• pp.323-329
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• 2011

In order to develop new protein carrier replacing poly(DL-lactic acid-co-glycolic acid) (PLGA) microspheres, succinylated pullulan acetate (SPA) was investigated to fabricate a long term protein delivery carrier. SPA microspheres loaded with lysozyme (Lys) as a model protein drug were prepared by a water/oil/water (W/O/W) double emulsion method. An acidity test of SPA copolymers after hydrolysis was performed to estimate the change of protein stability during releasing proteins from the microspheres. There was no pH change of SPA copolymers, but pH of PLGA polymers after hydrolysis was significantly decreased to around pH 2, indicating that the long-term stability of proteins released from SPA microspheres can be guaranteed. Loading efficiency of proteins into SPA microspheres was three times higher than those into conventional PLGA microspheres, indication of inducing stronger charge interaction between proteins and succinyl groups in SPA microspheres. Although initial burst behaviors were monitored in Lys-loaded SPA microspheres due to relatively strong hydrophilic succinyl segments in SPA microspheres, initial burst issues would be circumvented if the ratio of charge density of succinyl moieties and hydrophobic acetate groups is harmonically controlled. Therefore, in this study, a new attempt of protein delivery system was made and functional SPA was successfully confirmed as a new protein carrier.

• YAKHAK HOEJI
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• v.45 no.6
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• pp.623-633
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• 2001

Various bupivacaine-loaded microspheres were prepared using poly(d,1-lactide) (PLA) and poly(d,1-lactic-co-glycolide) (PLGA) by a solvent evaporation method for the sustained release of drug. The effects of process conditions such as drug loading, polymer type and solvent type on the characteristics of microspheres were investigated. The prepared microspheres were characterized for their drug loading, size distribution, surface morphology and release kinetics. Drug loading efficiency and yield of PLGA micro- spheres were higher than those of PLA microspheres. The prepared microspheres had an average particle size below 5${\mu}{\textrm}{m}$. The particle size range of microspheres was 1.65~2.24${\mu}{\textrm}{m}$. As a result of SEM, the particle size of PLA microspheres was smaller than that of PLGA microspheres. In morphology studies, microspheres showed a spherical shape and smooth surface in all process conditions. In thermal analysis, bupivacaine-loaded microspheres showed no peaks originating from bupivacaine. This suggested that bupivacaine base was molecular-dispersed in the polymer matrix of microspheres. The release pattern of the drug from microspheres was evaluated for 96 hours. The initial burst release of bupivacaine base decreased with increasing the molecular weight of PLGA, and the drug from microspheres released slowly. In conclusion, bupivacaine-loaded microspheres were successfully prepared from poly(d,1-lactide) and poly (d,1- lactic-co-glycolide) polymers with different molecular weights allowing control of the release rate.

• Journal of Biomedical Engineering Research
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• v.41 no.1
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• pp.62-66
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• 2020

Controlled drug release is important for effective treatment of cancer. Poly(DL-lactide-co-glycolide) acid (PLGA) is a Food and Drug Administration (FDA) approved polymer and have been extensively studied as drug delivery carriers with biodegradable and biocompatible properties. However, PLGA drug delivery carriers are limited due to the initial burst release of drug. Certain drugs require an early rapid release, but in many cases the initial rapid release can be inefficient, reducing therapeutic effects and also increasing side effects. Therefore, sustained release is important for effective treatment. Poly Lactic Acid stereo complex (PLA SC) is resistant to hydrolysis and has high stability in aqueous solutions. Therefore, in this work, PLGA based discoidal polymeric particles are modified by Poly Lactic Acid stereocomplex (PLAsc DPPs). PLAsc DPPs are 3 ㎛ in diameter, also showing a relatively sustained release profile. Fluorescein 5(6)-isothiocyanate (FITC) released from PLAsc DPPs was continuously observed until 38 days, which showed the initial release of FITC from PLAsc DPPs was about 3.9-fold reduced as compared to PLGA based DPPs at 1 hour.

• IMMUNE NETWORK
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• v.11 no.3
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• pp.163-168
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• 2011

Background: Nanoparticles (NPs) prepared from biodegradable polymers, such as poly (D,L-lactic acid-co-glycolic acid) (PLGA), have been studied as vehicles for the delivery of antigens to phagocytes. This paper describes the preparation of antigen-loaded PLGA-NPs for efficient cross-priming. Methods: NPs containing a similar amount of ovalbumin (OVA) but different sizes were produced using a micromixer-based W/O/W solvent evaporation procedure, and the efficiency of the NPs to induce the cross-presentation of OVA peptides were examined in dendritic cells (DCs). Cellular uptake and biodistribution studies were performed using fluorescein isothiocyanate (FITC)-loaded NPs in mice. Results: The NPs in the range of $1.1{\sim}1.4{\mu}m$ in size were the most and almost equally efficient in inducing the cross-presentation of OVA peptides via $H-2K^b$ molecules. Cellular uptake and biodistribution studies showed that opsonization of the NPs with mouse IgG greatly increased the percentage of FITC-positive cells in the spleen and lymph nodes. The major cell type of FITC-positive cells in the spleen was macrophages, whereas that of lymph nodes was DCs. Conclusion: These results show that IgG-opsonized PLGA-NPs with a mean size of $1.1{\mu}m$ would be the choice of biodegradable carriers for the targeted-delivery of protein antigens for cross-priming in vivo.