• Polymer(Korea)
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• v.30 no.2
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• pp.146-151
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• 2006

Linear and branched copolymers consisting of poly(ethylene glycol) (PEG) and $Poly({\varepsilon}-caprolactone)$ (PCL) were prepared to compare the characterization of star-shaped copolymers with various molecular architecture. Linear and branched PEG-PCL (1-arm, 2-arm, 4-arm, and 8-arm) copolymers were synthesized by the ring-opening polymerization of ${\varepsilon}-caprolactone$ in the presence of HCl $Et_2O$ as a monomer activator at room temperature. The synthesized copolymers were characterized with $^1H-NMR$, GPC, DSC, and XRD. As a result of the DSC and XRD, each copolymers showed different thermal properties and crystallinity according to the number of ms. The micellar characterization of linear and branched copolymers in an aqueous phase was carried out by using NMR, dynamic light scattering, AM, and fluorescence techniques. The critical micelle concentration (CMC) and diameters of micelles depended on the number of arms. Most micelles exhibited a spherical shape in AFM. In this study, we characterized star-shaped PEG-PCL copolymers and investigated their molecular architecture effect on the various properties. Furthermore, we confirmed that the micelles termed with linear and branched PEG-PCL copolymers have possibility as a potential hydrophobic drug delivery vehicle.

• Macromolecular Research
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• v.16 no.8
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• pp.704-710
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• 2008

Injectable hydrogels are quite promising materials due to their potential to minimize invasive implantation and this provides versatile fitness irrespective of the damaged regions and facilitates the incorporation of bioactive agents or cells. In situ gel formation through stereocomplex formation is a promising candidate for injectable hydrogels. In this paper, a new series of enantiomeric, four-arm, PEG-PLA block copolymers and their stereocomplexed hydrogels were prepared by bulk ring-opening polymerization of D-lactide and L-lactide, respectively, with stannous octoate as a catalyst. The prepared polymers were characterized by $^1H$ nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FT IR) spectroscopy, gel permeation chromatography (GPC) and thermal gravitational analysis (TGA), confirming the tailored structure and chain lengths. The swelling and degradation behavior of the hydrogels formed from a selected copolymer series were observed in different concentrations. The degradation rate decreased with increasing polymer content in the solution. The rheological behavior indicated that the prepared hydrogel underwent in situ gelation and had favorable mechanical strength. In addition, its feasibility as an injectable scaffold was evaluated using a media dependence test for cell culture. A Tris solution was more favorable for in situ gel formation than PBS and DMEM solutions were. These results demonstrated the in situ formation of hydrogel through the construction of a stereocomplex with enantiomeric, 4-arm, PEG-PLA copolymers. Overall, enantiomeric, 4-arm, PEG-PLA copolymers are a new species of stereocomplexed hydrogels that are suitable for further research into injectable hydrogels.

• Journal of Pharmaceutical Investigation
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• v.40 no.3
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• pp.175-180
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• 2010

Albumin-modification has been viewed as one of the most effective ways of extending the short in vivo lifetimes of peptide drugs by delaying glomerular filtration. In this study, we describe a new type 2 anti-diabetic exendin-4 (Ex4) peptide derivative with significant binding ability to human serum albumin (HSA). This exendin-4 derivative consists of a 4-branched polyethylene glycol $(PEG)_{5k}$ (Mw: 20 kDa) modified with three stearylamines ($C_{18}-NH_2$) and one exendin-4 on its branches. PEG and stearylamine were selected to provide functionality to increase molecular size and bind to albumin, respectively. This derivative ($3C_{18}-4PEG_{5k}$-Ex4) was shown to have larger molecular size (Ca. 152 kDa) than actual (25.0 kDa) when subjected to size-exclusion chromatography, and the fluorescein-tagged $3C_{18}-4PEG_{5k}$-Ex4 displayed significant binding to the HSA-immobilized Sepharose CL-4B resin using confocal laser scanning microscopy. Furthermore, $3C_{18}-4PEG_{5k}$-Ex4 was found to have acceptable anti-hyperglycemic efficacy via three consecutive oral glucose tolerance testings (OGTT) in fasted type 2 diabetic db/db mice. The $HD_{total}$ value ($57.6{\pm}12.3%$) of $3C_{18}-4PEG_{5k}$-Ex4 at a 50 nmol/kg dose was 2-fold greater than that ($31.0{\pm}8.7%$) of native exendin-4 in non-fasted db/db mice. Especially, the blood glucose levels in the mice group treated with $3C_{18}-4PEG_{5k}$-Ex4 did not rebound to ~150 mg/dL until 24 h after the injection, which obviously shows the extended hypoglycemia. We believe that this derivative has great pharmaceutical potential as a novel long-acting type 2 anti-diabetic injection treatment.

• Journal of the Korea Convergence Society
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• v.2 no.1
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• pp.7-13
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• 2011

Informations of multimedia centering in the images, are combined acoustic and letter, etc. Although the network advances and the capacity of the storage media extends, these huge informations will not be able to accommodate. From meaning which is like this, International standards for the compression and a multiplexing of image, acoustic and voice H261 where admits standard, JPEG, JBIG, MPEG-l, MPEG-2, MPEG-4 and H263, G series etc, are core techniques of multimedia. At initial step of the base technique which creates the base of like this multimedia service time, we developed the real-time MPEG-4 transmission systems to provides real-time MPEG-4 multimedia services. This system means becomes the base technique which hereafter is developed and is applied various system. This system Will be able to apply from a videoconference, a building protection system and a VOD video system to use the Internet. And, They, the image sensing, embedded linux, and MPEG4 software, will become sourceful technique to develop the different system.