The Experts below are selected from a list of 59877 Experts worldwide ranked by ideXlab platform
Baojun Bai - One of the best experts on this subject based on the ideXlab platform.
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in situ surface decorated polymer microsphere technology for enhanced oil recovery in high temperature petroleum reservoirs
Energy & Fuels, 2018Co-Authors: Baojun Bai, Daoyi Zhu, Jirui Hou, Yuguang Chen, Shuda ZhaoAbstract:Polymer Microspheres have been applied for petroleum reservoir enhanced oil recovery (EOR) in the past decade because they can overcome some drawbacks inherent in in situ polymer gel systems. A novel in situ surface decorated polymer microsphere technology was developed for chemical EOR in high-temperature reservoirs. The swelling performance of the conventional polymer Microspheres at room temperature was systematically analyzed and verified by an environmental scanning electron microscope. Their swelling and degradation mechanisms at a high temperature (150 °C) were also examined. To improve the long-term thermal stability of the polymer microsphere, different concentrations of polyethylenimine (PEI) were used as an in situ surface decorating agent. The decorated Microspheres remained stable at 150 °C for more than three months, and thermogravimetric analysis indicated that the in situ surface decorated polymer Microspheres could remain stable at temperatures up to 310 °C. PEI-decorated 3D network struc...
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research on matching mechanism between polymer Microspheres with different storage modulus and pore throats in the reservoir
Powder Technology, 2017Co-Authors: Hongbin Yang, Wanli Kang, Xia Yin, Xuechen Tang, Shuyang Song, Zeeshan Ali Lashari, Baojun Bai, Bauyrzhan SarsenbekulyAbstract:Abstract Polymer microsphere profile control technology has been a promising new profile control technology in heterogeneous reservoirs. The matching between polymer microsphere and pore throat of the reservoirs is crucial for profile control treatment. In this paper, the matching mechanism between polymer microsphere and pore throat had been systematically studied by sand pack models and micro models. The optical microscope and laser particle size analyzer were used to analyze the morphology and particle size of polymer Microspheres before and after injection. The matching factor was proposed to evaluate the compatibility. The long sand pack model was used to evaluate the migration rule of polymer Microspheres. Three modes including the migration mode, blockage mode and seepage mode were concluded and five passing through patterns, which were deformable passing through, partition passing through, blockage, adhesion and direct passing through, were observed. The specific corresponding statistical data of matching factors and passing through patterns in different storage modulus was established. The long sand pack displacement experiment showed that polymer Microspheres could migrate into the deep reservoir. The comprehensive correlation equation pin = 3.3072 × 10− 7G′2.6492R2.3882G′−0.0568 was derived according to the laboratory physical simulation data and the stable injection pressure of polymer microsphere with different storage modulus in different matching factors was predicted. This research will provide theoretical support for the further EOR research and field application of polymer Microspheres profile control system.
Taishung Chung - One of the best experts on this subject based on the ideXlab platform.
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poe peg poe triblock copolymeric Microspheres containing protein i preparation and characterization
Journal of Controlled Release, 2001Co-Authors: Yi Yan Yang, Jinping Wan, Pramoda Kumari Pallathadka, Steve Ng, Taishung Chung, Jorge HellerAbstract:Abstract Poly(ortho ester) (POE)–poly (ethylene glycol) (PEG) triblock copolymers (POE–PEG–POE) with different PEG contents were synthesised as carriers for controlled protein delivery. POE–PEG–POE Microspheres containing bovine serum albumin (BSA) were prepared using a double-emulsion (water-in-oil-in-water) process. In this first paper of a two-part series, we report the fundamentals of the fabrication and characterization of POE–PEG–POE Microspheres. Because the triblock copolymer is more hydrophilic than neat poly(ortho ester), the triblock copolymer yields a more stable first emulsion (water-in-oil) and a greater BSA encapsulation efficiency (90% vs. 30%). No BSA is found on POE–PEG–POE microsphere surfaces measured by X-ray photoelectron spectroscopy, while uniform BSA distributions are observed within the Microspheres by confocal microscopy. SEM pictures show that an increase in PEG content results in Microspheres with a denser cross-section because of a more stable first emulsion and better affinity between the copolymer and water. POE–PEG(20%)–POE suffers significant swelling during the fabrication process and yields the biggest Microspheres. However, the POE–PEG(30%)–POE Microspheres are much smaller since the dissolution loss of POE–PEG(30%)–POE in the external water phase may be much higher than that of POE–PEG(20%)–POE. The salt concentration in the external water phase significantly affects the morphology of the resultant Microspheres. Microspheres with a dense wall are produced when using pure water as the external water phase. Polymer concentration has less impact on BSA encapsulation efficiency but has a considerable effect on microsphere size and morphology. Increasing the concentration of the polyvinyl alcohol emulsifier does not cause an obvious decrease in microsphere size. However, increased BSA loading results in bigger Microspheres.
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effect of preparation temperature on the characteristics and release profiles of plga Microspheres containing protein fabricated by double emulsion solvent extraction evaporation method
Journal of Controlled Release, 2000Co-Authors: Yi Yan Yang, Huihui Chia, Taishung ChungAbstract:Abstract This study describes the influence of preparation temperature on the various characteristics and release profiles of poly( dl -lactide-co-glycolide) (PLGA) Microspheres. The bovine serum albumin (BSA)-loaded Microspheres were prepared using the water-in-oil-in-water (w/o/w) technique with poly(vinyl alcohol) as surfactant in the external aqueous phase. We have varied the preparation temperature to observe its effect on microsphere characteristics such as the microsphere shrinking rate during formation, particle size, density, surface and internal morphology, BSA encapsulation efficiency, BSA initial release, microsphere degradation and BSA in vitro release behaviour. During fabrication, a low preparation temperature of 5°C gives the fastest initial but the slowest overall shrinking rate. Microspheres formed at high temperatures of 38°C and 42°C on the other hand have the lowest initial yet the highest overall shrinking rate. Subsequently, microsphere mean size increases and the particle size distribution widens with increase in the preparation temperature. Although all the Microspheres have a porous surface as well as internal structure, Microspheres fabricated at high temperatures have a uniform internal pore distribution and a very thin dense skin layer, while Microspheres fabricated at lower temperatures have a thicker but porous skin layer and bigger pores in the middle of the sphere. Microspheres formed at 33°C are found to give the highest initial burst release. In terms of in vitro release, Microspheres fabricated at low temperatures (5°C, 15°C and 22°C) exhibit similar, steady rates. Microspheres formed at higher temperatures however give very low release rates after their initial release. The results obtained suggest that preparation temperature significantly affects microsphere formation, resulting in their structural and protein release profile differences. These differences ultimately work together to affect the initial release and overall release patterns of the Microspheres.
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effect of preparation temperature on the characteristics and release profiles of plga Microspheres containing protein fabricated by double emulsion solvent extraction evaporation method
Journal of Controlled Release, 2000Co-Authors: Yi Yan Yang, Huihui Chia, Taishung ChungAbstract:This study describes the influence of preparation temperature on the various characteristics and release profiles of poly(DL-lactide-co-glycolide) (PLGA) Microspheres. The bovine serum albumin (BSA)-loaded Microspheres were prepared using the water-in-oil-in-water (w/o/w) technique with poly(vinyl alcohol) as surfactant in the external aqueous phase. We have varied the preparation temperature to observe its effect on microsphere characteristics such as the microsphere shrinking rate during formation, particle size, density, surface and internal morphology, BSA encapsulation efficiency, BSA initial release, microsphere degradation and BSA in vitro release behaviour. During fabrication, a low preparation temperature of 5 degrees C gives the fastest initial but the slowest overall shrinking rate. Microspheres formed at high temperatures of 38 degrees C and 42 degrees C on the other hand have the lowest initial yet the highest overall shrinking rate. Subsequently, microsphere mean size increases and the particle size distribution widens with increase in the preparation temperature. Although all the Microspheres have a porous surface as well as internal structure, Microspheres fabricated at high temperatures have a uniform internal pore distribution and a very thin dense skin layer, while Microspheres fabricated at lower temperatures have a thicker but porous skin layer and bigger pores in the middle of the sphere. Microspheres formed at 33 degrees C are found to give the highest initial burst release. In terms of in vitro release, Microspheres fabricated at low temperatures (5 degrees C, 15 degrees C and 22 degrees C) exhibit similar, steady rates. Microspheres formed at higher temperatures however give very low release rates after their initial release. The results obtained suggest that preparation temperature significantly affects microsphere formation, resulting in their structural and protein release profile differences. These differences ultimately work together to affect the initial release and overall release patterns of the Microspheres.
Daoyi Zhu - One of the best experts on this subject based on the ideXlab platform.
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in situ surface decorated polymer microsphere technology for enhanced oil recovery in high temperature petroleum reservoirs
Energy & Fuels, 2018Co-Authors: Baojun Bai, Daoyi Zhu, Jirui Hou, Yuguang Chen, Shuda ZhaoAbstract:Polymer Microspheres have been applied for petroleum reservoir enhanced oil recovery (EOR) in the past decade because they can overcome some drawbacks inherent in in situ polymer gel systems. A novel in situ surface decorated polymer microsphere technology was developed for chemical EOR in high-temperature reservoirs. The swelling performance of the conventional polymer Microspheres at room temperature was systematically analyzed and verified by an environmental scanning electron microscope. Their swelling and degradation mechanisms at a high temperature (150 °C) were also examined. To improve the long-term thermal stability of the polymer microsphere, different concentrations of polyethylenimine (PEI) were used as an in situ surface decorating agent. The decorated Microspheres remained stable at 150 °C for more than three months, and thermogravimetric analysis indicated that the in situ surface decorated polymer Microspheres could remain stable at temperatures up to 310 °C. PEI-decorated 3D network struc...
Yi Yan Yang - One of the best experts on this subject based on the ideXlab platform.
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poe peg poe triblock copolymeric Microspheres containing protein i preparation and characterization
Journal of Controlled Release, 2001Co-Authors: Yi Yan Yang, Jinping Wan, Pramoda Kumari Pallathadka, Steve Ng, Taishung Chung, Jorge HellerAbstract:Abstract Poly(ortho ester) (POE)–poly (ethylene glycol) (PEG) triblock copolymers (POE–PEG–POE) with different PEG contents were synthesised as carriers for controlled protein delivery. POE–PEG–POE Microspheres containing bovine serum albumin (BSA) were prepared using a double-emulsion (water-in-oil-in-water) process. In this first paper of a two-part series, we report the fundamentals of the fabrication and characterization of POE–PEG–POE Microspheres. Because the triblock copolymer is more hydrophilic than neat poly(ortho ester), the triblock copolymer yields a more stable first emulsion (water-in-oil) and a greater BSA encapsulation efficiency (90% vs. 30%). No BSA is found on POE–PEG–POE microsphere surfaces measured by X-ray photoelectron spectroscopy, while uniform BSA distributions are observed within the Microspheres by confocal microscopy. SEM pictures show that an increase in PEG content results in Microspheres with a denser cross-section because of a more stable first emulsion and better affinity between the copolymer and water. POE–PEG(20%)–POE suffers significant swelling during the fabrication process and yields the biggest Microspheres. However, the POE–PEG(30%)–POE Microspheres are much smaller since the dissolution loss of POE–PEG(30%)–POE in the external water phase may be much higher than that of POE–PEG(20%)–POE. The salt concentration in the external water phase significantly affects the morphology of the resultant Microspheres. Microspheres with a dense wall are produced when using pure water as the external water phase. Polymer concentration has less impact on BSA encapsulation efficiency but has a considerable effect on microsphere size and morphology. Increasing the concentration of the polyvinyl alcohol emulsifier does not cause an obvious decrease in microsphere size. However, increased BSA loading results in bigger Microspheres.
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effect of preparation temperature on the characteristics and release profiles of plga Microspheres containing protein fabricated by double emulsion solvent extraction evaporation method
Journal of Controlled Release, 2000Co-Authors: Yi Yan Yang, Huihui Chia, Taishung ChungAbstract:Abstract This study describes the influence of preparation temperature on the various characteristics and release profiles of poly( dl -lactide-co-glycolide) (PLGA) Microspheres. The bovine serum albumin (BSA)-loaded Microspheres were prepared using the water-in-oil-in-water (w/o/w) technique with poly(vinyl alcohol) as surfactant in the external aqueous phase. We have varied the preparation temperature to observe its effect on microsphere characteristics such as the microsphere shrinking rate during formation, particle size, density, surface and internal morphology, BSA encapsulation efficiency, BSA initial release, microsphere degradation and BSA in vitro release behaviour. During fabrication, a low preparation temperature of 5°C gives the fastest initial but the slowest overall shrinking rate. Microspheres formed at high temperatures of 38°C and 42°C on the other hand have the lowest initial yet the highest overall shrinking rate. Subsequently, microsphere mean size increases and the particle size distribution widens with increase in the preparation temperature. Although all the Microspheres have a porous surface as well as internal structure, Microspheres fabricated at high temperatures have a uniform internal pore distribution and a very thin dense skin layer, while Microspheres fabricated at lower temperatures have a thicker but porous skin layer and bigger pores in the middle of the sphere. Microspheres formed at 33°C are found to give the highest initial burst release. In terms of in vitro release, Microspheres fabricated at low temperatures (5°C, 15°C and 22°C) exhibit similar, steady rates. Microspheres formed at higher temperatures however give very low release rates after their initial release. The results obtained suggest that preparation temperature significantly affects microsphere formation, resulting in their structural and protein release profile differences. These differences ultimately work together to affect the initial release and overall release patterns of the Microspheres.
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effect of preparation temperature on the characteristics and release profiles of plga Microspheres containing protein fabricated by double emulsion solvent extraction evaporation method
Journal of Controlled Release, 2000Co-Authors: Yi Yan Yang, Huihui Chia, Taishung ChungAbstract:This study describes the influence of preparation temperature on the various characteristics and release profiles of poly(DL-lactide-co-glycolide) (PLGA) Microspheres. The bovine serum albumin (BSA)-loaded Microspheres were prepared using the water-in-oil-in-water (w/o/w) technique with poly(vinyl alcohol) as surfactant in the external aqueous phase. We have varied the preparation temperature to observe its effect on microsphere characteristics such as the microsphere shrinking rate during formation, particle size, density, surface and internal morphology, BSA encapsulation efficiency, BSA initial release, microsphere degradation and BSA in vitro release behaviour. During fabrication, a low preparation temperature of 5 degrees C gives the fastest initial but the slowest overall shrinking rate. Microspheres formed at high temperatures of 38 degrees C and 42 degrees C on the other hand have the lowest initial yet the highest overall shrinking rate. Subsequently, microsphere mean size increases and the particle size distribution widens with increase in the preparation temperature. Although all the Microspheres have a porous surface as well as internal structure, Microspheres fabricated at high temperatures have a uniform internal pore distribution and a very thin dense skin layer, while Microspheres fabricated at lower temperatures have a thicker but porous skin layer and bigger pores in the middle of the sphere. Microspheres formed at 33 degrees C are found to give the highest initial burst release. In terms of in vitro release, Microspheres fabricated at low temperatures (5 degrees C, 15 degrees C and 22 degrees C) exhibit similar, steady rates. Microspheres formed at higher temperatures however give very low release rates after their initial release. The results obtained suggest that preparation temperature significantly affects microsphere formation, resulting in their structural and protein release profile differences. These differences ultimately work together to affect the initial release and overall release patterns of the Microspheres.
Daniel W Pack - One of the best experts on this subject based on the ideXlab platform.
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influence of particle size and antacid on release and stability of plasmid dna from uniform plga Microspheres
Journal of Controlled Release, 2007Co-Authors: Neelesh K Varde, Daniel W PackAbstract:PLGA Microspheres are attractive DNA delivery vehicles due to their controlled release capabilities. One major problem with PLGA Microspheres is that they develop an acidic microclimate as the polymer degrades, lowering the intraparticle pH, and potentially damaging the DNA. Antacids have recently shown promise in buffering this acidic microclimate and enhancing protein stability. We manufactured uniform plasmid DNA-encapsulating PLGA Microspheres of two sizes (47, 80 μm diameter) and antacid concentrations (0, 3% Mg(OH)2). Microspheres with antacid had a homogeneous surface coverage of small pores, which resulted in a significant reduction of the burst effect. The 47 μm Microspheres exhibited complete release of plasmid DNA over the course of two months. Incomplete release was observed from 80 μm spheres, though Microspheres with 3% Mg(OH)2 showed a higher cumulative release, suggesting that the antacid at least partially aids in increasing the stability of DNA. SEM was used to visualize the surface pore evolution and cross-sectional microsphere structure over time. Subsequent image analysis was used to quantify the increase of surface pore sizes. Cross-sectional images showed increasing internal degradation and erosion, which resulted in a hollowing-out of Microspheres. Our studies show that the incorporation of antacid into the microsphere structure has potential in addressing some of the major problems associated with DNA encapsulation and release in PLGA Microspheres.
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microsphere size precipitation kinetics and drug distribution control drug release from biodegradable polyanhydride Microspheres
Journal of Controlled Release, 2004Co-Authors: Cory Berkland, Matt J Kipper, Balaji Narasimhan, Kyekyoon Kim, Daniel W PackAbstract:Abstract A thorough understanding of the factors affecting drug release mechanisms from surface-erodible polymer devices is critical to the design of optimal delivery systems. Poly(sebacic anhydride) (PSA) Microspheres were loaded with three model drug compounds (rhodamine B, p -nitroaniline and piroxicam) with a range of polarities (water solubilities). The drug release profiles from monodisperse particles of three different sizes were compared to release from polydisperse Microspheres. Each of the model drugs exhibited different release mechanisms. Drug distribution within the polymer was investigated by laser scanning confocal microscopy and scanning electron microscopy. Rhodamine, the most hydrophilic compound investigated, was localized strongly toward the microsphere surface, while the much more hydrophobic compound, piroxicam, distributed more evenly. Furthermore, all three compounds were most uniformly distributed in the smallest Microspheres, most likely due to the competing effects of drug diffusion out of the nascent polymer droplets and the precipitation of polymer upon solvent extraction, which effectively “traps” the drug in the polymer matrix. The differing drug distributions were manifested in the drug release profiles. Rhodamine was released very quickly independent of microsphere size. Thus, extended release profiles may not be obtainable if the drug strongly redistributes in the Microspheres. The release of p -nitroaniline was more prolonged, but still showed little dependence on microsphere size. Hence, when water-soluble drugs are encapsulated with hydrophobic polymers, it may be difficult to tailor release profiles by controlling microsphere size. The piroxicam-loaded Microspheres exhibit the most interesting release profiles, showing that release duration can be increased by decreasing microsphere size, resulting in a more uniform drug distribution.
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precise control of plg microsphere size provides enhanced control of drug release rate
Journal of Controlled Release, 2002Co-Authors: Cory Berkland, Martin King, Daniel W PackAbstract:Abstract An important limitation in the development of biodegradable polymer Microspheres for controlled-release drug delivery applications has been the difficulty of specifically designing systems exhibiting precisely controlled release rates. Because microparticle size is a primary determinant of drug release, we developed a methodology for controlling release kinetics employing monodisperse poly( d,l -lactide-co-glycolide) (PLG) Microspheres. We fabricated 20-, 40- and 65-μm diameter rhodamine-containing Microspheres and 10-, 50- and 100-μm diameter piroxicam-containing Microspheres at various loadings from 1 to 20%. In vitro release kinetics were determined for each preparation. Drug release depended strongly on microsphere diameter with 10- and 20-μm particles exhibiting concave-downward release profiles while larger particles resulted in sigmoidal release profiles. Overall, the rate of release decreased and the duration increased with increasing microsphere size. Release kinetics from mixtures of uniform Microspheres corresponded to mass-weighted averages of the individual microsphere release kinetics. Appropriate mixtures of uniform Microspheres were identified that provided constant (zero-order) release of rhodamine and piroxicam for 8 and 14 days, respectively. Mixing of uniform Microspheres, as well as control of microsphere size distribution, may provide an improved methodology to tailor small-molecule drug-release kinetics from simple, biodegradable-polymer microparticles.
