• Journal of Pharmaceutical Investigation
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• v.26 no.3
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• pp.201-205
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• 1996

Poloxamer, block copolymers of ethylene oxide and propylene oxide was crosslinked by diisocyanates and triisocyanates to form water-swellable, physically strong, rubber-like elastic, high biocompatible polyurethanes. The isocyanate-hydroxyl stoichiometry was kept 1:1, but the crosslinking density was varied. The variations examined were the ratio of diisocyanate and triisocyanate. The delivery of two drugs of different water solubilities from hydrogel matrices was studied. It appeared that the drug nature greatly influenced its release kinetics possibly due to drug-polymer interactions. The release profiles, however, could be modified to a great extent by adjusting the polymer network structure Generally the high crosslinking density was required for prolonged drug delivery.

• Journal of Pharmaceutical Investigation
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• v.21 no.2
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• pp.91-95
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• 1991

Polyethylene glycol, polypropylene glycol and block copolymer of ethylene glycol and propylene glycol were crosslinked by triisocyanate to form water swellable, rubbery polymer. The equilibrium swelling of the hydrogels ranged from 3% to 60% according to the hydrophobic-hydrophilic properties of the prepolymers. Model drugs, sodium salicylate and prednisolone were incorporated in the polymer matrices by swelling loading. Physical properties of the drugs affected the drug release mechanisms due to the change in the swelling behaviors of the polymeric devices. Zero order release was observed in the case of relatively hydrophobic polymer matrices.

• Journal of Pharmaceutical Investigation
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• v.25 no.3
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• pp.53-59
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• 1995

Ethinylestradiol (EE)-containing matrix was fabricated with ethylene-vinyl acetate(EVA) copolymer to control the release of the drug, Effect of addition of PEG 400 as receptor solution, the stripping of skin and Azone pretreatment on skin on the permeation of EE through the excised mouse skin was also studied. The permeation rate of EE through the excised mouse skin was affected by the PEG 400 volume fraction. The Azone pretreatment on skin didn't affect on the steady state flux, however, the lag time was shortened. The permeation rate of EE through the stripped skin was much larger than that through the whole skin. It showed that the stratum corneum acts as a barrier of skin permeation. The fact that there is little difference in EE permeation between the intact skin and the stripped skin with EVA membrane shows the permeation of EE through the mouse skin is mainly controlled by the membrane.

• Polymer(Korea)
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• v.28 no.4
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• pp.328-334
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• 2004

A series of methoxy poly(ethylene glycol) (MPEG)-poly(L-lactide-co-glycolide) (PLGA) diblock copolymers were synthesized by ring-opening polymerization of L-lactide and glycolide with carbitol (134 g/mole) or different molecular weights of MPEG (550, 2000, and 5000 g/mole) as an initiator in presence of Sn(Oct)$_2$. The properties of diblock copolymers were characterized by using $^1$H-NMR, GPC, and XRD. After uniform mixing of block copolymers and 1% albumin bovine-fluorescein isothiocyanate(FITC-BSA) with a freeze miller, the wafers loaded FITC-BSA were fabricated by using a mold with a dimensions of 3 mm${\times}$1mm diameter. The release profiles of FITC-BSA and the pH changes of wafer were examined using pH 7.4 PBS for 30 days at 37$^{\circ}C$. The release profiles of albumin showed fast initial burst as the molecular weights of MPEG increased. As a result of this study, the release behavior of BSA was controlled with introducing MPEG in the block copolymers.

• Polymer(Korea)
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• v.28 no.3
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• pp.232-238
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• 2004

MPEG-PCL diblock copolymers consisting of methoxy poly(ethylene glycol) (MPEG) and $\varepsilon$-caprolactone (CL) as drug carriers were synthesized by ring-opening polymerization MPEG-PCL diblock copolymers were characterized by X-ray diffraction and differential scanning calorimetry. After freeze milling of block copolymers and albumin bovine-fluorescein isothiocyanate (FITC-BSA) as model protein, the wafers loaded FITC-BSA were fabricated by direct compression method. The release profiles of FITC-BSA were examined using pH 7.4 PBS for 14 days at 37$^{\circ}C$. The release amount was determined by fluorescence intensity by using the fluorescence spectrophotometer. The morphological change of wafers was observed by digital camera and scanning electron microscope. The release rate and initial burst of BSA increased with increasing PEG molecular weights and decreasing PCL molecular weights in the segments of MPEG -PCL diblock copolymers.

• Bulletin of the Korean Chemical Society
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• v.22 no.5
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• pp.467-475
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• 2001

A triblock copolymer based on $poly(\varepsilon-caprolactone)$ (PCL) as the hydrophobic part and poly(ethylene glycol) (PEG) as the hydrophilic portion was synthesized by a ring-opening mechanism of ${\varepsilon}-caprolactone$ with PEG containing a hydroxyl group at bot h ends as an initiator. The synthesized block copolymers of PCL/PEG/PCL (CEC) were confirmed and characterized using various analysis equipment such as 1H NMR, DSC, FT-IR, and WAXD. Core-shell type nanoparticles of CEC triblock copolymers were prepared using a dialysis technique to estimate their potential as a colloidal drug carrier using a hydrophobic drug. From the results of particle size analysis and transmission electron microscopy, the particle size of CEC core-shell type nanoparticles was determined to be about 20-60 nm with a spherical shape. Since CEC block copolymer nanoparticles have a core-shell type micellar structure and small particle size similar to polymeric micelles, CEC block copolymer can self-associate at certain concentrations and the critical association concentration (CAC) was able to be determined by fluorescence probe techniques. The CAC values of the CEC block copolymers were dependent on the PCL block length. In addition, drug loading contents were dependent on the PCL block length: the larger the PCL block length, the higher the drug loading content. Drug release from CEC core-shell type nanoparticles showed an initial burst release for the first 12 hrs followed by pseudo-zero order release kinetics for 2 or 3 days. CEC-2 block copolymer core-shell type nanoparticles were degraded very slowly, suggesting that the drug release kinetics were governed by a diffusion mechanism rather than a degradation mechanism irrelevant to the CEC block copolymer composition.

• Journal of Pharmaceutical Investigation
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• v.41 no.4
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• pp.217-225
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• 2011

The aim of this work was to prepare porous osmotic pump tablets for controlled delivery of Aceclofenac. Aceclofenac solid dispersion was prepared to improve the solubility by using the drug - carrier (Mannitol) ratio of 1:1. The osmotic pump tablets were prepared using the solid dispersed product of Aceclofenac. The formulation contains potassium chloride as osmotic agent, cellulose acetate as semipermeable membrane, poly ethylene glycol (PEG 4000) as pore former and sodium lauryl sulphate (SLS) as solubility enhancer. The formulations were designed by the general factors such as osmotic agent and pore former. All formulations were evaluated for various physical parameters and, the in vitro release studies were conducted as per USP. The drug release kinetic studies such as zero order, first order, and Higuchi and Korsmeyer peppas were determined and compared. All the formulations gave more controlled release compared to the marketed tablet studied. Numerical optimization techniques were applied to found out the best formulation by considering the parameter of in vitro drug release kinetics and dissolution profile standards. It was concluded that the porous osmotic pump tablets (F7) composed of Aceclofenac solid dispersion/Potassium chloride/Lactose/Sodium lauryl sulphate/Magnesium Stearate (400/40/95/10/5, mg/tab) and coating composition with Cellulose acetate/ PEG 4000 (60/40 %w/w) is the most satisfactory formulation. The porous osmotic pump tablets provide prolonged, controlled, and gastrointestinal environment-independent drug release.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.711-712
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• 2005

• Polymer(Korea)
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• v.34 no.3
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• pp.198-201
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• 2010

We have worked a surface modification to release a strong agglomeration of multi-walled carbon nanotube(MWCNT) and a incorporation of hydrophilic polymer to improve compatibility between MWCNT and polymers. Carboxylated MWCNT was easily obtained by acid treatment and the carboxylate was converted to acylchloride by thionyl chloride. Then, we tried one more synthesizing routes to achieve covalent bonds with poly(ethylene oxide) having amine end groups of low molecular weight. We measured the polymer content on the surface of MWCNT by TGA and observed increased diameter of MWCNT by SEM and TEM analysis.

• Bulletin of the Korean Chemical Society
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• v.29 no.8
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• pp.1539-1544
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• 2008

A polymeric micelle, based on the poly(benzyl-L-histidine)-b-poly(ethylene glycol) (polyBz-His-b-PEG) diblock copolymer, was designed as a tumor-specific targeting carrier. The micelles (particle size: 67-80 nm, critical micelle concentration (CMC); 2-3 $\mu$g/mL) were formed from the diafilteration method at pH 7.4, as a result of self-assembly of the polyBz-His block at the core and PEG block on the shell. Removing benzyl (Bz) group from polyBz-His block provided pH-sensitivity of the micellar core; the micelles were physically destabilized in the pH range of pH 7.4-5.5, depending on the content of the His group free from Bz group. The ionization of His group at a slightly acidic pH promoted the deformation of the interior core. These pHdependent physical changes of the micelles provide the mechanism for pH-triggering anticancer drug (e.g., doxorubicin: DOX) release from the micelle in response to the tumor’s extracellular pH range (pH 7.2-6.5).