• Carbon letters
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• v.13 no.3
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• pp.173-177
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• 2012

A drug delivery system (DDS) was prepared with a temperature and pH-responsive hydrogel. Poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAAc)/poly(N-isopropylacrylamide) (PNIPAAm)/multi-walled carbon nanotube (MWCNT) nanocomposites were prepared by radical polymerization for the temperature and pH-responsive hydrogels. MWCNTs were employed to improve both the thermal conductivity and mechanical properties of the PVA/PAAc/PNIPAAm/MWCNT nanocomposite hydrogels. Various amounts of MWCNTs (0, 0.5, 1 and 3 wt%) were added to the nanocomposite hydrogels. PVA/PAAc/PNIPAAm/MWCNT nanocomposite hydrogels were characterized with a scanning electron microscope. The mechanical properties were measured with a universal testing machine. Swelling and releasing properties of nanocomposite hydrogels were investigated at various temperatures and pHs. Temperature and pH-responsive release behavior was found to be dependent on the content of MWCNTs in nanocomposite hydrogels.

• Journal of the Korean Chemical Society
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• v.58 no.1
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• pp.92-99
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• 2014

The pH sensitive hydrogels composed of N-isopropylacrylamide (NIPA) and acryloyl phenylalanine (APA) were prepared by redox polymerization using N,N'-methylenebisacrylamide (MBA) as a crosslinker. Anti-inflammatory and analgesic agent, Keterolac Tromethamine (KT), was loaded successfully into poly(NIPA-co-APA) copolymeric hydrogels by swelling equilibrium method. To understand the nature of drug in the polymeric matrix, the newly synthesized drug loaded poly(NIPA-co-APA) copolymeric hydrogels were characterized by using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. The scanning electron microscopy (SEM) technique result indicates the spherical smooth surface of the hydrogels. The drug (KT) releasing nature of the poly(NIPA-co-APA) hydrogels was studied in pH 1.2 and 7.4. Effects of drug loading, crosslinking agent, pH and the ionic strength of the external medium on swelling of hydrogels were also investigated.

• Journal of Pharmaceutical Investigation
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• v.27 no.3
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• pp.189-198
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• 1997

The purpose of the present study was to investigate the effect of medium chain fatty acid salts, reported as enhancers in insulin nasal absorption, on the rectal absorption of insulin in rats. The serum glucose and remained insulin level in perfusate were measured after rectal recirculation of insulin with or without sod. laurate, sod. caprate and sod. caprylate in situ. The addition of sod. laurate or sod. caprate reduced serum glucose concentration considerably. Sod. caprate (1.0%) showed the greatest promoting effect on the decrement of serum glucose. Eudispert hv hydrogels containing insulin with medium chain fatty acid salts were, thereby, prepared and evaluated. The release rate of insulin from Eudispert hv hydrogels was reduced with an increase in the content of Eudispert hv, and was raised with increasing NaOH concentration. Ten percent Eudispert hv hydrogels were offered for the rectal administration of insulin. The addition of 1.0% sod. caprate reduced serum glucose concentration remarkably after rectal administration of 10% Eudispert hv hydrogels containing insulin. The level of glucose decrement was greater by 30% compared to subcutaneous administration of insulin solution. From the above findings, Eudispert hv hydrogels would be used as useful rectal delivery systems of insulin.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.3
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• pp.107-114
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• 2022

Carboxymethyl cellulose/poly(ethylene glycol) (CMC/PEG) hydrogels crosslinked with citric acid (CA) are synthesized to evaluate the effect of CMC molecular weight (Mw), PEG and CA concentration on the optical property, swelling rate (SR), degradation rate (DR), and cytotoxicity and cell proliferation of hydrogels. For crosslinked CMC/PEG hydrogels, the FT-IR peak intensity associated with hydroxyl groups decreases due to PEG intercalation (esterification crosslinking) between CMC chains in a similar manner as the concentration of CA crosslinker increases. Crosslinked CMC (Mw = 90,000)/PEG hydrogels with 10 % CA dissolve regardless of PEG content. However, the SR of the CMC (Mw = 250,000)/PEG hydrogels decrease from 4923 % to 168 % with increasing PEG and CA concentrations from 0 to 20 % and from 0 to 25 %, respectively. As the Mw of CMC increases, the DR of the hydrogel is greatly improved. CMC (Mw = 250,000)/PEG10 hydrogels with 10 % CA exhibit the optimum properties of high absorbing capacity (3,200 %) with moderate DR (54 %), stiffness (1.39 ± 0.19 GPa), and cell viability (94.8 ± 1.3 %). CA-crosslinked CMC/PEG hydrogels are highly suitable for wound dressing or personal care applications due to their non-toxicity, good cell proliferation, SR, and mechanical properties.

• Elastomers and Composites
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• v.54 no.4
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• pp.359-367
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• 2019

Poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels modified with various co-monomers, such as N-vinyl pyrrolidone (NVP), glycidyl methacrylate (GMA), and glycerol monomethacrylate (GMMA), were prepared to investigate the effect of adding a co-monomer on the water contents, surface wettability, and tensile modulus. These polymers were synthesized by thermal- and photo-polymerization in the presence of azobisisobutyronitrile (AIBN) and diphenyl(2,4,6-trimethylbenzoyl)-phosphineoxide (TPO) as the initiators. The characteristics of the hydrogels were analyzed via FTIR and UV/Vis spectroscopies, contact angle measurements, and tensile modulus measurements with UTM. Regarding the properties of water in the hydrogels, the ratio between free to bound water was investigated using differential scanning calorimetry (DSC). The effects of adding the co-monomers on the water content, surface wettability, and tensile modulus for soft contact lenses were also investigated. In the case of p(HEMA-co-NVP) hydrogels, the increase in the equilibrium water content (EWC) was primarily due to the increase in the bound water content. For p(HEMA-co-GMMA) hydrogels, an increase in free water content was the main reason for the increased EWC. In contrast, in the case of p(HEMA-co-GMA) hydrogels, a decrease in bound water content was observed to be the main factor that reduced the EWC. Photo-polymerized PHEMA hydrogels showed enhanced surface wettability and tensile modulus as compared to those produced via thermal polymerization.

• Journal of Pharmaceutical Investigation
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• v.22 no.4
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• pp.251-266
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• 1992

A major problem with the peptide-based drugs is that these drugs must generally be administered by injection. Therefore, there is considerable research interest in alternative routes of delivery, such as buccal, nasal, gastrointestinal route and etc. Site-specific drug delivery to the colon, as an alternative to parenteral drug delivery, is of interest for the delivery of peptide-based drugs as well as the delivery of low molecular weight drugs for the treatment of colonic disease, This review describes some considerations of colon-specific drug delivery using hydrogels.

• Macromolecular Research
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• v.17 no.1
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• pp.26-30
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• 2009

To modify and strengthen the properties of PHEMA hydrogel, composite hydrogels containing varying amounts of a Pluronic (PEO-PPO-PEO) component were synthesized by bulk polymerization of HEMA in the presence of Pluronic dimethacrylate under mild photo initiating conditions. The effects of the Pluronic component on gel properties were investigated by measuring the degree of swelling with its temperature responsive behavior, the mechanical properties, and the morphology of the composite hydrogels. With increased Pluronic content, the modified PHEMA hydrogels exhibited an increase in the degree of swelling, and the swelling showed an enhanced thermo-responsive behavior that was completely reversible. In addition, improved mechanical strength and the development of a microporous gel morphology were observed in hydrogels containing Pluronic.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.281-285
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• 1996

Pulsatile swelling behaviors and their application to drug delivery system were studied by using interpenetrating polymer networks(IPN) hydrogels constructed with poly(vinyl alcohol) and poly(acrylic acid). The PVA/PAAc IPNs hydrogels were symthesized by UV irradiation tallowed by repetitive freezing and thawing method. These hydrogels showed pH and temperature sensitive swelling behaviors. From the release experiment, the release amount of model drug incorporated into these hydrogels showed pulsatile patterns. Permeability coefficients obtained by various solutes differed in response to changes of permeation conditions.

• Bulletin of the Korean Chemical Society
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• v.20 no.8
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• pp.921-924
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• 1999

Hydrogels were prepared from poly( Υ-glutamic acid) (PGA) solution by g-irradiation of 90 kGy and 170 kGy. The hydrogels were more cross-linked with a higher dosage g-irradiation and completely hydrolyzed at 85℃ within 4 hours resulting in homogeneous solution. NMR techniques were employed to clarify chemical bond formation and scission involved during γ-irradiation and hydrolysis. Characterization of these samples was carried out by taking both liquid state and solid state NMR spectra of PGA and hydrolyzed hydrogels and comparison of these spectra with the solid state NMR spectra of hydrogels. Our results indicate that complicated chemical bond formation and scission have occurred during hydrolysis and γ-irradiation. The samples prepared with higher dosage of γ-irradiation showed more diverse chemical bond formation and scission.

• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.354-360
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• 2005

Polyvinyl alcohol (PVA) hydrogels were prepared by the irradiation and heating. Irradiation and heating processes were carried out to improve the heat resistance of PVA hydrogels at high temperature. The physical properties such as gel content, degree of swelling and gel strength for the synthesized hydrogels were examined. The structure variations were investigated using the following techniques: differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Gel content and gel strength of the hydrogels were higher when the two steps of irradiation followed by heat treatment were used rather than only with the irradiation. The hydrogels prepared by the irradiation and the two steps had good heat resistance at high temperature.