• Journal of Pharmaceutical Investigation
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• v.34 no.1
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• pp.1-14
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• 2004

A promising approach to the development of a new single-step vaccine, which would eliminate the requirement for multiple injections, involves the encapsulation of antigens into microspheres. Biodegradable poly(lactide-co-glycolide) (PLGA) microspheres gave us a bright insight for controling antigen release in a pulsatile fashion, thereby mimicking two or tree boosting injections. However, in spite of the above merits, the level of immunization induced by a single-shot vaccination is often lower tan two doses of alum-adsorbed antigen. Therefore, optima modification of the microsphere is essential for the development of single-step vaccines. In the review, we discuss the stability of antigen in microsphere, safety and non-toxic in human and encapsulation technology. Also, we attempted to outline relevant physicochemical properties on the immunogenicity of microsphere vaccine and attainment of pulsatile release pater by combination of different microsphere, as well as to analyze immunological data associated with antigen delivery by microsphere. Although a lot of variables are related to the optimized microsphere formulation, we could conclude that judicious choice of proper polymer type, adjustment of particles size, and appropriate immunization protocol along with a suitable adjuvant might be a crucial factor for the generation of long-lasting immune response from a single-step vaccine formulation employing PLGA microsphere.

• 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.39 no.1
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• pp.144-150
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• 2015

Gellan gum as a natural polysaccharide has good heat resistance, acid resistance and enzymes resistance. However, one of the drawbacks of gellan gum might be the lower mechanical strength. In this work, gellan gum scaffolds were mixed with poly(lactic-co-glycolic acid) (PLGA) microsphere in order to improve mechanical properties. The gellan gum scaffolds with various contents of PLGA microsphere were prepared for the regeneration of disc tissues. To evaluate the mechanical strength of hybrid structure of gellan gum and PLGA microsphere, compression strength of the fabricated scaffolds was measured. MTT analysis, SEM observation, histological evaluation and RT-PCR were performed to confirm the effect on the cell growth and extracellular matrix secretion. As a result, it showed the best cell proliferation and extracellular matrix secretion in gellan gum sponge containing 50% PLGA microspheres. In conclusion, this study confirmed that the hybrid structure of gellan gum and PLGA microspheres was found suitable in regeneration of the intervertebral disc.

• KSBB Journal
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• v.17 no.1
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• pp.33-37
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• 2002

To improve in vitro release kinetic of G-CSF in PLGA microsphere, G-CSF was PEGylated with methoxy polyethylene glycol-aldehyde (mPEG-aldehyde, MW 5000). The majority of G-CSF was mono-PEGylated and it was characterized using SDS-PAGE, HPLC, and peptide mapping. The PLGA microencapsulation with the native, or PEGylated G-CSF was performed using W/O/w method, where the encapsulation efficiency was high. For the high loading of G-CSF to microsphere, G-CSF and PEGylated G-CSF were concentrated and then verified the protein stability using native gel and gel filtration chromatography. In comparison with native G-CSF, PEGylated G-CSF was released during the extended period and its maximum amount of released G-CSF was also increased.

• Journal of Microbiology and Biotechnology
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• v.15 no.3
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• pp.510-518
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• 2005

In this study, we investigated whether PLGA microspheres in combination with hyaluronic acid (HA) gel have appropriate properties as a bulking agent for urologic injection therapies and whether the implantation of PLGA microspheres and HA gel induces angiogenesis in the newly formed tissues. In order to investigate whether this bulking agent is injectable, this material was injected through 24-gauge needles into the subcutaneous dorsum of the mouse. The bulking agent was easily injected without needle obstruction. Histological analyses of the hybrid tissues at 2 weeks showed that host cells at the surrounding tissues migrated into the spaces between the implanted PLGA microspheres and formed tissue-like structures. An inflammatory response to the implants was mild at 2 weeks and diminished at 8 weeks. Importantly, extensive ingrowth of blood vessels was observed in the hybrid tissues formed by the injection of PLGA microspheres and HA, whereas blood vessels rarely formed in the hybrid tissues formed by the injection of PLGA microspheres only. The implant volume was conserved for almost the entire implantation period. Histological analyses of the distant organs of the bulking agent-implanted animals, such as the lungs, liver, heart, brain, kidney, and spleen, showed no evidence of the injected microsphere migration. These results show that PLGA microspheres in combination with HA possess the appropriate characteristics for a bulking agent for urologic injection therapies and induce extensive blood vessel formation in the hybrid tissues.

• Polymer(Korea)
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• v.33 no.1
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• pp.7-12
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• 2009

PLGA microspheres have been known as an injectable system for tissue engineering. The purpose of this study was to investigate the condition of emulsion formation and cell adhesion on the microsphere surface. BSA-loaded PLGA microsphere was fabricated by oil-in-water (O/W) and water-in-oil-in-water (W/O/W) solvent evaporation method. Sodium alginate was dissolved in water phase to control initial burst release and to improve lag time by PLGA bulk degradation. In addition, the morphology of cells attached on the micro spheres was studied using a scanning electron microscopy (SEM). Cellular proliferation behavior of human disc cells cultivated on PLGA micro spheres was analyzed using a MTT assay. MTT assay revealed that the cells can attach and proliferate on PLGA microspheres. According to these results, we concluded that BSA -loaded alginate/PLGA microspheres can be used as an injectable system for tissue engineering application.

• Journal of Pharmaceutical Investigation
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• v.40 no.4
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• pp.251-254
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• 2010

The formation of acylated peptide impurities in poly(lactide-co-glycolide) (PLGA) formulations is one of the major challenges to the development of successful sustained-release product. Octreotide, synthetic analogue of somatostatin, has been identified to be acylated in PLGA microsphere formulations. The purpose of this study was to investigate the pH effect on the formation of acylated octreotides by PLGA. In the incubation with PLGA in 0.1 M phosphate buffer at pH 7.4, approximately 98% of octreotide adsorbed to PLGA through 14 days and 66.3% of acylated octreotides were produced after 42 days, whereas the interaction of octreotide with PLGA was significantly inhibited in the incubation at pH 4, in which the acylated octreotides were observed to be 9.2% after 42 days. In the interaction study at pH 4.1-7.4, the production of acylated octreotides was demonstrated to be dependent on environmental pH. Below pH 5.0, the acylation of octreotide was significantly inhibited. This study indicates that the pH is the major factor for the formation of acylated octreotide in PLGA formulations.

• Polymer(Korea)
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• v.29 no.1
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• pp.69-73
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• 2005

To overcome the main disadvantages of non-viral gene delivery systems such as repeated administration due to the low transfection efficiency, poly(D,L-lactide-co-glycolide) was applied to encapsulate pDNA in its microsphere formulation. Free pDNA or various ratios (w/w) of chitosan/pDNA complexes was used for encapsulation, with the resulting encapsulation efficiency of 44%, 5%, and 8% for free pDNA, 0.7:1 and 1:1 ratios, respectively. Scanning electron micrographs of poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres encapsulating pDNA or chitosan-condensed pDNA revealed a smooth spherical shape immediately after microsphere preparation and a collapsed porous shape in 41 days due to the degradation of PLGA. In vitro release profile showed that the 0.7:1 (w/w) ratio formulation exerted 47% release in 26 days, whereas free pDNA or 1:1 (w/w) ratio formulation did only 15% or 32%, respectively.

• 한국당과학회:학술대회논문집
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• 2006.11a
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• pp.57-57
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• 2006

• Polymer(Korea)
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• v.29 no.6
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• pp.543-548
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• 2005

Double-layered spheres play an important role in controlling drug delivery for pharmaceutical application, because of the low initial burst compared with single-layered spheres and targetable delivery to specific organ. But it has drawback in loading drug and controlling size. In this study, we developed double-layered spheres using relatively simple oil-in-water (O/W) solvent evaporation method witw/without ultrasonication and investigated the size variation of the double-layered microspheres on the contents of poly(lactide- co-glycolide) (PLGA). Double - layered spheres were char-acterized by scanning elecron microscope (SEM), camscope, and confocal fluorescence laser microscope (CFLM). Double-layered spheres showed smooth surfaces and obvious difference between core and corona by SEM observation and camscope. We observed the fluorescent core in the double-walled spheres composed of FlTC-dextran and PLGA using CFLM. It was found that the core of the microsphere was dextran and the corona of the fabricate microsphere was PLGA. Also, the more PLGA concentration, the more the size of the fabricating double-layered sphere observed.