• 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.

• Journal of Pharmaceutical Investigation
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• v.40 no.4
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• pp.245-250
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• 2010

Porous poly(lactic-co-glycolic acid) microspheres (PLGA MS) have been utilized as an inhalation delivery system and a matrix scaffold system for tissue engineering. Here, gelatin (type A) is introduced as an extractable pH-responsive porogen, which is capable of controlling the porosity and pore size of PLGA microspheres. Porous PLGA microspheres were prepared by a water-in-oil-in-water ($w_1/o/w_2$) double emulsification/solvent evaporation method. The surface morphology of these microspheres was examined by varying pH (2.0~11.0) of water phases, using scanning electron microscopy (SEM). Also, their porosity and pore size were monitored by altering acidification time (1~5 h) using a phosphoric acid solution. Results showed that the pore-forming capability of gelatin was optimized at pH 5.0, and that the surface pore-formation was not significantly observed at pHs of < 4.0 or > 8.0. This was attributable to the balance between gel-formation by electrostatic repulsion and dissolution of gelatin. The appropriate time-selection between PLGA hardening and gelatin-washing out was considered as a second significant factor to control the porosity. Delaying the acidification time to ~5 h after emulsification was clearly effective to make pores in the microspheres. This finding suggests that the porosity and pore size of porous microspheres using gelatin can be significantly controlled depending on water phase pH and gelatin-removal time. The results obtained in this study would provide valuable pharmaceutical information to prepare porous PLGA MS, which is required to control the porosity.

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.257-262
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• 2019

The control of microstructure is critical for the porous fuel particles used for infiltrating actinide nuclides. This study concerns the effect of heating processes on properties and microstructure of the fuel particles. The uniform gel precursor beads were synthesized by a microfluidic sol-gel process and then the porous $CeO_2$ microspheres, as a surrogate for the ceramic nuclear fuel particles, were obtained by heating treatment of the gel precursors. The fabricated $CeO_2$ microspheres have a narrow size distribution and good sphericity due to the feature of microfluidics. The effects of heating processes parameters, such as heating mode and peak temperatures on the properties of microspheres were studied in detail. An optimized heating mode and the peak temperature of $650^{\circ}C$ were selected to produce porous $CeO_2$ microspheres. The optimized heating mode can avoid the appearance of broken or crack microspheres in the heating process, and as-prepared porous microspheres were of suitable pore size distribution and pore volume for loading minor actinide (MA) solution by an infiltration method that is used for fabrication of MA-bearing nuclear fuel beads. After the infiltration process, $1000^{\circ}C$ was selected as the final temperature to improve the compressive strength of microspheres.

• 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.

• 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.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.403-409
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• 2015

Porous alumina ceramics are involved in many industrial applications due to the exceptional properties of these products. This study addresses the preparation of porous alumina ceramics using hollow microspheres as a pore-forming agent and slip casting as a green-body-forming technique. A uniform distribution of pores is a basic requirement of a porous material. This study investigates three different slurry systems, i.e., as-prepared alumina slurry, alumina slurry electrostatically dispersed by hydrochloric acid (HCl), and slurry dispersed by the commercial dispersant 'Darvan C-N'. At a low viscosity, the hollow microspheres in the slurry tend to float, which causes a non-uniform pore distribution. To avoid this phenomenon, the viscosity of the slurry was increased to the extent that the movement of hollow microspheres ceased in the slurry. As a result, a uniform pore distribution was achieved.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.29 no.1
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• pp.89-101
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• 2003

A new collolidal silver (Ag) system is present in which a fine colloidal Ag is in situ deposited onto functionalized porous poly(ethylene glycol dimethacrylate) (poly (EGDMA)) microspheres. The effectiveness of Ag deposition was investigated considering the surface characteristics of poly (EGDMA) microspheres, The result reported in this study illustrates that the control of surface area and surface functionality (in this study, a hydroxyl group) of poly (EGDMA) microspheres is an important factor that determines practically the degree of deposition of colloidal Ag. The x-ray analysis showed that Ag nanoparticles were dispersed evenly inner and outer surfaces and has a face center cubic(fcc) phase. In the preservation test, the Ag-containing poly (EGDMA) microspheres had a powerful anti-bacterial performance, showing a high potential for a new preservative.

• Membrane Journal
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• v.31 no.1
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• pp.52-60
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• 2021

When preparing calcium alginate microspheres using rotating membrane emulsification that rotates SPG (Shirasu porous glass) tubular membrane in the continuous phase, the optimal conditions of rotating membrane emulsification process parameters for producing monodisperse microspheres were determined. We determined the effects of process parameters of rotating membrane emulsification (the rotating speed of membrane module, the transmembrane pressure, the ratio of dispersed phase to continuous phase, the alginate concentration, the emulsifier concentration, the stabilizer concentration, the crosslinking agent concentration, and the membrane pore size) on the mean size and size distribution of alginate microspheres. As a result, the size of the microspheres decreased as the rotating speed of membrane module, the emulsifier concentration, and the crosslinking agent concentration increased among the process parameters of rotating membrane emulsification. On the contrary, as the ratio of dispersed phase to continuous phase, the transmembrane pressure, and the alginate concentration increased, the size of the microspheres increased. In the rotating membrane emulsification using an SPG membrane with a pore size of 3.2 ㎛, it was possible to finally prepare monodisperse alginate microspheres with a particle size of 4.5 ㎛ through the control of process parameters.

• Membrane Journal
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• v.14 no.3
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• pp.218-229
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• 2004

We prepared monodispersed calcium alginate microspheres by controlling various conditions of emulsification procedure using a lab-scale batch type membrane emulsification system equipped with SPG (Shirasu porous glass) tubular membranes. We determined the effects of process parameters of membrane emulsification (ratio of dispersed phase to continuous phase, alginate concentration, emulsifier concentration, type and concentration of stabilizer, transmembrane pressure, concentration of crosslinking agent, stirring speed and membrane pore size) on the mean size and size distribution of alginate microspheres. The increase of the ratio of dispersed phase to continuous phase, transmembrane pressure and alginate concentration led to the increase in the mean size of alginate microspheres. On the contrary, the increase in emulsifier concentration, stirring speed of the continuous phase and concentration of the crosslinking agent caused the reduction of the mean size of microspheres. Through controlling these parameters, monodisperse alginate microspheres with about $6{\mu}{\textrm{m}}$ of the mean size and 1.1 of the size distribution value were finally prepared in case of the using SPC membrane with the pore size of $2.9{\mu}{\textrm{m}}$.

• Biomedical Science Letters
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• v.12 no.4
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• pp.443-450
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• 2006

To demonstrate their possibilities as an enhanced vaccine delivery system, protein-loaded Poly lactide glycolide copolymer (PLGA) microspheres were prepared with different physical characteristics. Ethyl acetate (EA) solvent extraction process was employed to prepare microspheres and the effects of process parameters on drug release properties were evaluated. The biodeuadability of microspheres was also evaluated by the pH change and GPC (Gel permeation chromatography). Primary IgG antibody responses in BALB/c mice were compared with protein saline solutions as negative controls and adsorbed alum suspensions as positive controls after single subcutaneous injection for in vivo studies. The microspheres showed a erosion with a highly porous structure and did not keep their spherical shape at 45 days and this result could be confirmed by GPC. In vitro release of proteinous drug showed initial burst effect in all batches of microspheres, followed by gradual release over the next 4 weeks. PLGA microspheres were degraded until 45 days and the secondary structure of OVA was not affected by the preparation method. Enzyme-linked immunosorbent assays demonstrated that the single subcutaneous administrations of OVA-loaded PLGA microspheres induced enhanced serum IgG antibody response in comparison to negative and positive controls. These results demonstrated that microspheres providing the controlled release of antigens might be useful in advanced vaccine formulations for the parenteral carrier system.