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Kilwon Cho - One of the best experts on this subject based on the ideXlab platform.
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incorporation and Release Behavior of hydrophobic drug in functionalized poly d l lactide block poly ethylene oxide micelles
Journal of Controlled Release, 2004Co-Authors: Jaeyoung Lee, Eun Chul Cho, Kilwon ChoAbstract:The poly(ethylene oxide)–poly(lactide) (PEO–PLA) block copolymers containing a small quantity of carboxylic acid in the PLA block were synthesized. The microscopic characteristics of nanoparticles with carboxylic acid content in the copolymer were analyzed, and the effect of specific interactions between the copolymer and the model drug on the drug loading capacity and the Release Behavior were investigated systematically. The sizes of nanoparticles prepared by a dialysis method are within the range of 30–40 nm. The nanoparticles prepared from functionalized block copolymers have a very low critical micelle concentration (CMC) value as low as ∼10−3 mg/ml, which indicates a good stability of the nanoparticles in spite of the presence of carboxylic acid. The drug loading efficiency of nanoparticles dramatically increased when carboxylic acid content was increased in the block copolymer. This result may be attributed to the increase of interactions between the copolymer and the drug. The Release rate of the drug was much slower from nanoparticles containing higher amounts of carboxylic acid in the copolymer, which might be associated with the enhanced interaction between the carboxylic group of copolymers and the drug. These experimental results suggest that the nanoparticles prepared from functionalized PEO–PLA block copolymers could be a good candidate for an injectable drug delivery carrier.
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incorporation and Release Behavior of hydrophobic drug in functionalized poly d l lactide block poly ethylene oxide micelles
Journal of Controlled Release, 2004Co-Authors: Jaeyoung Lee, Eun Chul Cho, Kilwon ChoAbstract:The poly(ethylene oxide)-poly(lactide) (PEO-PLA) block copolymers containing a small quantity of carboxylic acid in the PLA block were synthesized. The microscopic characteristics of nanoparticles with carboxylic acid content in the copolymer were analyzed, and the effect of specific interactions between the copolymer and the model drug on the drug loading capacity and the Release Behavior were investigated systematically. The sizes of nanoparticles prepared by a dialysis method are within the range of 30-40 nm. The nanoparticles prepared from functionalized block copolymers have a very low critical micelle concentration (CMC) value as low as approximately 10(-3) mg/ml, which indicates a good stability of the nanoparticles in spite of the presence of carboxylic acid. The drug loading efficiency of nanoparticles dramatically increased when carboxylic acid content was increased in the block copolymer. This result may be attributed to the increase of interactions between the copolymer and the drug. The Release rate of the drug was much slower from nanoparticles containing higher amounts of carboxylic acid in the copolymer, which might be associated with the enhanced interaction between the carboxylic group of copolymers and the drug. These experimental results suggest that the nanoparticles prepared from functionalized PEO-PLA block copolymers could be a good candidate for an injectable drug delivery carrier.
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effects of crystalline microstructure on drug Release Behavior of poly e caprolactone microspheres
Journal of Controlled Release, 2003Co-Authors: Jongcheol Jeong, Jaeyoung Lee, Kilwon ChoAbstract:This study investigates the Release Behavior of papaverine from poly(epsilon-caprolactone) (PCL) microparticles prepared by the oil/water solvent evaporation method. Microparticles were characterized in terms of crystalline morphology, size, drug loading, and encapsulation efficiency by using differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and UV spectrometry. The Release Behavior of papaverine was governed by the microstructure of PCL microparticles, suggesting that the environment for diffusion changes according to processing conditions such as polymer solution concentration, thermal history, and polymer molecular weight. As the PCL solution concentration increased, the drug Release Behavior showed a more sustained pattern. This result indicates that the size of the PCL microparticles is a determining factor for drug Release. And when higher PCL molecular weight is used for preparation of microparticles, it led to a rapid Release. Furthermore, a more delayed pattern of drug Release profile was obtained in the sample prepared with higher thermal treatment. These results suggest that the crystalline microstructure of PCL microparticles plays an important role in its drug Release Behavior.
Yoshiaki Kawashima - One of the best experts on this subject based on the ideXlab platform.
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in vitro drug Release Behavior of d l lactide glycolide copolymer plga nanospheres with nafarelin acetate prepared by a novel spontaneous emulsification solvent diffusion method
Journal of Pharmaceutical Sciences, 1994Co-Authors: Toshiyuki Niwa, Noriyuki Kunou, Hirofumi Takeuchi, Tomoaki Hino, Yoshiaki KawashimaAbstract:Abstract Nanospheres with D, L‐lactide/glycolide copolymer (PLGA) were prepared as a biodegradable and biocompatible polymeric carrier for peptide drugs by a novel spontaneous emulsification solvent diffusion mathod. Nafarelin acetate (NA), a luteinizing hormone‐releasing hormone analogue, was employed as a model peptide drug to investigate the encapsulation efficiency. The drug and PLGA, dissolved in an acetone–dichloromethane–water mixture, were poured into an aqueous solution of polyvinyl alcohol under moderate stirring at room temperature. Spontaneous emulsification arising from a rapid diffusion of acetone from the organic to the aqueous phase enables preparation of PLGA submicron spheres 200–300 nm in size. The entrapment of NA in nanospheres was improved by blending low molecular weight (Mw = 4500) PLGA with higher molecular weight PLGA due to the synergistic effect of thrapid deposition of PLGA and the ionic interaction between NA and PLGA. By coadmixing a small amount of negatively charged phospholipids such as dipalmitoyl phosphatidylglycerol or dicetyl phosphate, the leakage of water‐soluble NA was further prevented. The NA encapsulated in PLGA nanospheres was more stable than native NA in acidic medium (pH = 1.2). The drug‐Release Behavior from nanospheres suspended in the disintegration test solution no. 1 (Japanese Pharmacopeia XII) exhibited a biphasic pattern. It was found that the initial burst of Release might be due to the degradation of the PLGA chain, as monitored by gel permeation chromatography. At a later stage, the drug was Released more slowly, the rate of which was determined by the diffusion of the drug in the poruos matrix structure. In the test solution no. 2(pH = 6.8), the drug Release rate from the nanospheres was much slower than that in solution no. 1.
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preparations of biodegradable nanospheres of water soluble and insoluble drugs with d l lactide glycolide copolymer by a novel spontaneous emulsification solvent diffusion method and the drug Release Behavior
Journal of Controlled Release, 1993Co-Authors: Toshiyuki Niwa, Noriyuki Kunou, Hirofumi Takeuchi, Tomoaki Hino, Yoshiaki KawashimaAbstract:Abstract Nanospheres with d , l -lactide/glycolide copolymer (PLGA) were prepared as a biodegradable polymeric carrier for both water-soluble and insoluble drugs by a novel spontaneous emulsification solvent diffusion method. Indomethacin and 5-fluorouracil (5-FU) were employed as poorly water-soluble and water-soluble model drugs, respectively, to investigate the encapsulation efficiency. The drug and PLGA, dissolved in an acetone-dichloromethane (or acetone-chloroform) mixture, were poured into an aqueous solution of polyvinyl alcohol with stirring using a high-speed homogenizer when necessary. The dispersed droplets were finely emulsified into nanometer-sized spheres. The marked decrease of the interfacial tension between organic and aqueous phases and the spontaneous mixing caused by a rapid diffusion of acetone from the organic to aqueous phase resulted in the formation of submicron-sized PLGA spheres. The recovery of indomethacin entrapped in the nanospheres (mean diameter: 400–600 nm) increased to 75% at maximum. The rapid deposition of polymeric film on the droplet was required for improving the encapsulation of 5-FU to prevent leakage from the droplet. The mean diameter of nanospheres formulated with 5-FU were successfully decreased to 200–300 nm even without high-speed homogenizing. The drug Release Behavior from nanospheres suspended in buffered solution exhibited a biphasic pattern. The initial burst of Release might be due to the rapid Release of drugs deposited on the surface and in the water channels of nanospheres. At a later stage, the drug Release rate was reduced. During the Release test, PLGA was not degradated for 100 h irrespective of the molecular weight. The molecular weight of polymer was a main factor in controlling the drug Release rate from the nanospheres.
M Ravi N V Kumar - One of the best experts on this subject based on the ideXlab platform.
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plga nanoparticles for oral delivery of hydrophobic drugs influence of organic solvent on nanoparticle formation and Release Behavior in vitro and in vivo using estradiol as a model drug
Journal of Pharmaceutical Sciences, 2008Co-Authors: D K Sahana, V Bhardwaj, Gaurav Mittal, M Ravi N V KumarAbstract:The aim of present investigation was to screen different solvents for optimizing nanoparticle preparation in terms of particle size, entrapment efficiency, and finally, Release Behavior using a model drug estradiol. Nanoparticles were prepared following emulsion-diffusion-evaporation method using didodecyldimethyl ammonium bromide (DMAB) or polyvinyl alcohol (PVA) as stabilizers. Ethyl acetate (EA), acetone (ACE), chloroform (CHL), and dichloromethane (DCM) were used as organic solvents either individually or in combinations. DMAB when used as surfactant led to smaller particle size as compared to PVA irrespective of the solvents and combinations used, but on the other hand, PVA produced particles with higher entrapment when combinations of solvents used. DCM in combination with EA resulted in highest entrapment with both the stabilizers. All the formulations exhibited similar in vitro Release profile (Zero order) irrespective of stabilizer (DMAB or PVA) used, however, the average Release per day was higher in case of DCM formulations due to greater entrapment. In situ uptake studies suggest that smaller the particle size better is the uptake. The bioavailability from nanoparticles was assessed in male Sprague Dawley (SD) rats at a dose of 1 mg drug/rat. EA/DMAB (size 116.0 ± 2.6 nm) and DCM:EA 70:30/DMAB (size 253.0 ± 5.5 nm) showed the Release for 9 and 5 days, respectively, whereas EA/PVA (size 279.3 ± 2.5 nm) Released the drug over the periods of 3 days suggesting that particle size has significant role in determining the fate of nanoparticles in vivo. Histopathological examination revealed absence of any inflammatory response with the formulations under the studied period.
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estradiol loaded plga nanoparticles for oral administration effect of polymer molecular weight and copolymer composition on Release Behavior in vitro and in vivo
Journal of Controlled Release, 2007Co-Authors: Garima Mittal, D K Sahana, V Bhardwaj, M Ravi N V KumarAbstract:Abstract The present investigation was aimed at optimization of estradiol loaded PLGA nanoparticulate formulations resulting in improved oral bioavailability and sustained Release of estradiol by varying the molecular weight and copolymer composition of PLGA. Nanoparticles were prepared following emulsion–diffusion–evaporation method employing didodecyldimethyl ammonium bromide (DMAB) as stabilizer. The effect of polymer molecular weight and copolymer composition on particle properties and Release Behavior (in vitro and in vivo) has been reported. Drug Release in vitro decreased with increase in molecular weight and lactide content of PLGA. Zero order Release was obtained with low molecular weight (14,500 and 45,000 Da) PLGA, while high molecular weight (85,000 and 213,000 Da) and different copolymer compositions followed square root of time (Higuchi's pattern) dependent Release. The bioavailability of estradiol from nanoparticles was assessed in male Sprague Dawley (SD) rats at a dose of 1 mg estradiol/rat. The in vivo performance of the nanoparticles was found to be dependent on the particle size, polymer molecular weight and copolymer composition. The Cmax of drug in the plasma was dependent on the polymer molecular weight and composition while particle size was found to influence the duration of Release, suggesting smaller is better. The histopathological examination revealed absence of any inflammatory response with the formulations prepared of low/high molecular weight or high lactide content polymers for the studied period. Together, these results indicate that nanoparticulate formulations are ideal carriers for oral administration of estradiol having great potential to address the dose related issues of estradiol.
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drug Release Behavior of beads and microgranules of chitosan
Biomaterials, 2000Co-Authors: K Gupta, M Ravi N V KumarAbstract:Beads and microgranules carriers have important potential applications for the administration of therapeutic molecules. A novel approach for the preparation of chitosan beads and microgranules is presented. The present work is an investigation of the in vitro Release kinetics of diclofenac sodium (DFS) from chitosan beads and microgranules. The in vitro Release profiles of DFS from chitosan beads and microgranules are monitored using Shimadzu 1601 UV-VIS spectrophotometer. Drug Release Behavior of beads and microgranules has been compared. The Release rate of DFS from the beads has been found to be slower in comparison to the microgranules. It may also be noted that the percent and amount of the drug Release were much higher in acidic solution than in basic solution, probably due to the swelling properties of the matrix at acidic pH.
Jaeyoung Lee - One of the best experts on this subject based on the ideXlab platform.
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incorporation and Release Behavior of hydrophobic drug in functionalized poly d l lactide block poly ethylene oxide micelles
Journal of Controlled Release, 2004Co-Authors: Jaeyoung Lee, Eun Chul Cho, Kilwon ChoAbstract:The poly(ethylene oxide)–poly(lactide) (PEO–PLA) block copolymers containing a small quantity of carboxylic acid in the PLA block were synthesized. The microscopic characteristics of nanoparticles with carboxylic acid content in the copolymer were analyzed, and the effect of specific interactions between the copolymer and the model drug on the drug loading capacity and the Release Behavior were investigated systematically. The sizes of nanoparticles prepared by a dialysis method are within the range of 30–40 nm. The nanoparticles prepared from functionalized block copolymers have a very low critical micelle concentration (CMC) value as low as ∼10−3 mg/ml, which indicates a good stability of the nanoparticles in spite of the presence of carboxylic acid. The drug loading efficiency of nanoparticles dramatically increased when carboxylic acid content was increased in the block copolymer. This result may be attributed to the increase of interactions between the copolymer and the drug. The Release rate of the drug was much slower from nanoparticles containing higher amounts of carboxylic acid in the copolymer, which might be associated with the enhanced interaction between the carboxylic group of copolymers and the drug. These experimental results suggest that the nanoparticles prepared from functionalized PEO–PLA block copolymers could be a good candidate for an injectable drug delivery carrier.
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incorporation and Release Behavior of hydrophobic drug in functionalized poly d l lactide block poly ethylene oxide micelles
Journal of Controlled Release, 2004Co-Authors: Jaeyoung Lee, Eun Chul Cho, Kilwon ChoAbstract:The poly(ethylene oxide)-poly(lactide) (PEO-PLA) block copolymers containing a small quantity of carboxylic acid in the PLA block were synthesized. The microscopic characteristics of nanoparticles with carboxylic acid content in the copolymer were analyzed, and the effect of specific interactions between the copolymer and the model drug on the drug loading capacity and the Release Behavior were investigated systematically. The sizes of nanoparticles prepared by a dialysis method are within the range of 30-40 nm. The nanoparticles prepared from functionalized block copolymers have a very low critical micelle concentration (CMC) value as low as approximately 10(-3) mg/ml, which indicates a good stability of the nanoparticles in spite of the presence of carboxylic acid. The drug loading efficiency of nanoparticles dramatically increased when carboxylic acid content was increased in the block copolymer. This result may be attributed to the increase of interactions between the copolymer and the drug. The Release rate of the drug was much slower from nanoparticles containing higher amounts of carboxylic acid in the copolymer, which might be associated with the enhanced interaction between the carboxylic group of copolymers and the drug. These experimental results suggest that the nanoparticles prepared from functionalized PEO-PLA block copolymers could be a good candidate for an injectable drug delivery carrier.
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effects of crystalline microstructure on drug Release Behavior of poly e caprolactone microspheres
Journal of Controlled Release, 2003Co-Authors: Jongcheol Jeong, Jaeyoung Lee, Kilwon ChoAbstract:This study investigates the Release Behavior of papaverine from poly(epsilon-caprolactone) (PCL) microparticles prepared by the oil/water solvent evaporation method. Microparticles were characterized in terms of crystalline morphology, size, drug loading, and encapsulation efficiency by using differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and UV spectrometry. The Release Behavior of papaverine was governed by the microstructure of PCL microparticles, suggesting that the environment for diffusion changes according to processing conditions such as polymer solution concentration, thermal history, and polymer molecular weight. As the PCL solution concentration increased, the drug Release Behavior showed a more sustained pattern. This result indicates that the size of the PCL microparticles is a determining factor for drug Release. And when higher PCL molecular weight is used for preparation of microparticles, it led to a rapid Release. Furthermore, a more delayed pattern of drug Release profile was obtained in the sample prepared with higher thermal treatment. These results suggest that the crystalline microstructure of PCL microparticles plays an important role in its drug Release Behavior.
Hesheng Xia - One of the best experts on this subject based on the ideXlab platform.
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fast Release Behavior of block copolymer micelles under high intensity focused ultrasound redox combined stimulus
Journal of Materials Chemistry B, 2013Co-Authors: Rui Tong, Hesheng XiaAbstract:Aiming at the development of a controlled redox responsive polymeric micelle system, a series of redox-sensitive ABA triblock degradable copolymers with different amounts of disulfide bonds were synthesized. These multi-disulfide-containing amphiphilic copolymers are able to self-assemble in aqueous solution to form spherical micelles with a hydrophobic polyurethane block forming the hydrophobic core. The presence of dynamic and labile disulfide bonds in the copolymer makes the copolymer and its micelle have responsivity to stimuli such as redox agents and ultrasound. The micellar properties and Release kinetics of encapsulated guest molecules in response to stimuli were investigated using hydrophobic pyrene as a fluorescent probe and DTT as a redox agent. The redox-responsive Behavior could be adjusted by changing the amount of disulfide bonds within the copolymer backbone. A relatively fast Release Behavior was observed for micelles formed by the copolymers in which every repeat unit of the hydrophobic block contains a disulfide bond. Furthermore, the Release rate could be greatly enhanced and adjusted remotely under HIFU irradiation in the presence of DTT. The HIFU/redox combined stimulus for the specially designed copolymer micelles containing disulfide bonds provides a novel modality for drug delivery systems.
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high intensity focused ultrasound responsive Release Behavior of pla b peg copolymer micelles
Journal of Controlled Release, 2009Co-Authors: Hongji Zhang, Hesheng Xia, Jie WangAbstract:Poly(lactic acid) (PLA) was synthesized by solution polycondensation of L-lactic acid and further reacted with dihydroxyl poly(ethylene glycol) (PEG) to obtain the amphiphilic block copolymer PLA-b-PEG. The biodegradable PLA-b-PEG copolymer can self-assemble into spherical micelles in aqueous solution. Nile Red, as a payload model, was used to examine the Release Behavior of the micelles. The hydrophobic Nile Red can be adsolubilized into the hydrophobic inner core of PLA-b-PEG micelles. With the introduction of Nile Red, the size of micelles increased. Moreover, high intensity focused ultrasound (HIFU), as a non-contact and remote control approach, was introduced to control the Release Behavior of PLA-b-PEG micelles containing Nile Red. The Release Behavior of Nile Red was monitored by fluorescence emission spectra. The results showed that HIFU can trigger the Release of the encapsulated Nile Red from PLA-b-PEG micelles. By adjusting the HIFU time, intensity and location, the Release Behavior of Nile Red from micelles can be tuned. Base on the results, an irreversible Release mechanism under HIFU was proposed. The irreversible Release of Nile Red from the PLA-b-PEG micelle was attributed to a chemically breaking process of micelle structure due to the degradation of the PLA-b-PEG chain that resulted from the transient cavitation in the HIFU focal spot.
