• IMMUNE NETWORK
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• v.13 no.1
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• pp.16-24
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• 2013

CTLA-4Ig is regarded as an inhibitory agent of the T cell proliferation via blocking the costimulatory signal which is essential for full T cell activation. To improve applicability, we developed the CTLA-4Ig-CTKC in which the c-terminal lysine had been replaced by cysteine through single amino acid change. The single amino acid mutation of c-terminus of CTLA-4Ig was performed by PCR and was checked by in vitro transcription and translation. DNA construct of mutant form was transfected to Chinese hamster ovary (CHO) cells by electroporation. The purified proteins were confirmed by Western blot and B7-1 binding assay for their binding ability. The suppressive capacity of CTLA-4Ig-CTKC was evaluated by the mixed lymphocyte reaction (MLR) and in the allogeneic pancreatic islet transplantation model. CTLA-4Ig-CTKC maintained binding ability to B7-1 molecule and effectively inhibits T cell proliferation in MLR. In the murine allogeneic pancreatic islet transplantation, short-term treatment of CTLA-4Ig-CTKC prolonged the graft survival over 100 days. CTLA-4Ig-CTKC effectively inhibits immune response both in MLR and in allogeneic islet transplantation model, indicating that single amino acid mutation does not affect the inhibitory function of CTLA-4Ig. CTLA-4Ig-CTKC can be used in vehicle-mediated drug delivery system such as liposome conjugation.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2295-2298
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• 2012

We describe herein a three-dimensionally diverse micropatterning of poly(lactic acid), as a biopolymer, using 1-butyl-3-methylimidazolium-based room-temperature ionic liquids (bmim-based RTILs), [bmim]X (X = $SbF_6$, $PF_6$, $NTf_2$, Cl). Utilizing the hydrophobic bmim-based RTILs, [bmim]X (X = $SbF_6$, $PF_6$, $NTf_2$) and a phase separation technique, we were able to produce white and opaque membranes with a three-dimensional structure closely packed with particles ($10-50{\mu}m$ in diameter). The particlulate structure, made by the assistance of [bmim]$NTf_2$ and DCM, interestingly transformed to a fibrous structure by using a cosolvent, e.g., DCM/$CF_3CH_2OH$. When we used an increased amount of [bmim]$NTf_2$, the particles were effectively detached and macrosized ($100-500{\mu}m$ in diameter) and the oval-shaped beads were obtained in a powder form. By varying the counter-anion type of the imidazolium-based RTIL, for example from $NTf_2^-$ to $Cl^-$, the particulate 3D-morphology was once more transformed to a porous structure. These reserch results could be potentially useful, as a method to fabricate particulate scaffolds, fibrous or porous scaffolds, and beads as a biopolymer device in diverse fields including drug delivery, tissue regeneration, and biomedical engineering.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3740-3744
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• 2010

A typically designed 'Peptide Lego' has two distinct surfaces: a hydrophilic side that contains the complete charge distribution and a hydrophobic side. In this article, we describe the fabrication of a unique lego-type peptide with the AEAEYAKAK sequence. The novel peptide with double amphiphilic surfaces is different from typical peptides due to special arrangement of the residues. The results of CD, FT-IR, AFM and DLS demonstrate that the peptide with the random coil characteristic was able to form stable nanostructures that were mediated by non-covalent interactions in an aqueous solution. The data further indicated that despite its different structure, the peptide was able to undergo self-assembly similar to a typical peptide. In addition, the use of hydrophobic pyrene as a model allowed the peptide to provide a new type of potential nanomaterial for drug delivery. These efforts collectively open up a new direction in the fabrication of nanomaterials that are more perfect and versatile.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3623-3631
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• 2010

We prepared several novel molecular transporters built on myo- and scyllo-inositol scaffolds with variations in the number of guanidine residues, linker chain lengths and patterns. Some of these transporters were found to localize in mitochondria, and the mitochondrial affinity seems to be substantially related to the scaffold stereochemistry.

• Journal of Biomedical Engineering Research
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• v.29 no.3
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• pp.173-178
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• 2008

Recent advancements in the electrospinning method enable the production of ultrafine solid and continuous fibers with diameters ranging from a few nanometers to a few hundred nanometers with controlled surface and morphological features. A wide range of biopolymers can be electrospun into mats with a specific fiber arrangement and structural integrity. These features of nanofiber mats are morphologically similar to the extracellular matrix of natural tissues, which are characterized by a wide pore diameter distribution, a high porosity, effective mechanical properties, and specific biochemical properties. This has resulted in various kinds of applications for polymer nanofibers in the field of biomedicine and biotechnology. The current emphasis of research is on exploiting these properties and focusing on determining the appropriate conditions for electrospinning various biopolymers for biomedical applications, including scaffolds used in tissue engineering, wound dressing, drug delivery, artificial organs, and vascular grafts, and for protective shields in specialty fabrics. This paper reviews the research on biomedical applications of electrospun nanofibers.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1532-1533
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• 2007

Hollow형 미세바늘 어레이는 주사기와 패치의 장점을 결합하여 여러 종류의 약물을 통증 없이, 전달할 수 있게 한다. 본 논문에서는 건식 식각 방법과 습식 식각 방법을 이용하여 hollow형 실리콘 미세바늘 어레이를 제작하는 제작 공정과 그 결과를 제시하였다. 미세바늘 어레이의 형태는 실리콘 웨이퍼의 앞면에서 세 번의 식각 공정을 이용해 제작되었는데, 첫 번째 건식 식각 공정으로 피부에의 침투를 원활히 하기 위해 바늘 끝을 형성하고, 두 번째 건식 식각 공정으로 바늘의 길이를 조절하며, 마지막 HNA solution을 이용한 습식 식각 공정으로 바늘을 더 가늘게 만들면서 끝을 더 날카롭게 식각한다. 바늘을 통해 약물전달이 가능하도록 웨이퍼의 뒷면으로부터 건식 식각 공정을 이용해 약물 주입통로를 형성하였다. 제작된 Hollow형 실리콘 미세바늘 어레이는 $170\;{\mu}m$의 너비와 $230\;{\mu}m$의 길이, 직경 $40\;{\mu}m$의 약물 주입통로를 가지고 있으며, $1\;cm^2$의 시편 위에 $1000\;{\mu}m$의 피치로 $9{\times}9$ 개의 바늘을 형성하였다.

• Macromolecular Research
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• v.11 no.1
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• pp.47-52
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• 2003

The objective of this study was to develop a polymeric drug delivery system for camptothecin (CPT), capable of improving its therapeutic index and reducing its side effects. A monomeric conjugate, 3,6-endo-methylene-1,2,3,6-tetrahydrophthalimidoethanoylcamptothecin in (ETECPT) between CPT and 3,6-endo-methylene-1,2,3,6-tetrahydrophthalimidoethanoic acid was synthesized. Its homo-and copolymer with acrylic acid (AA) were prepared by photopolymerization using 2,2-dimethoxy-2-phenylacetophenone (DMP) as a photoinitiator. The monomer and its polymers were characterized by IR, $^1$H- and $^{13}$ C-NMR spectra. The ETECPT content in poly(ETECPT-co-AA) obtained by elemental analysis was 82 wt%. The number-average molecular weights of the polymers determined by gel permeation chromatography were as follows: M$_{n}$ = 11,400 for poly(ETECPT), M$_{n}$ = 17,900 for poly(ETECPT-co-AA). The $IC_{50}$/ values of ETECPT and its polymers against cancer cells were much larger than that of CPT. Our results from the in vivo antitumor activity indicated that all polymers show high antitumor activity than CPT at a dose of 100 mg/kg./kg.

• Polymer(Korea)
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• v.35 no.3
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• pp.254-259
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• 2011

In electrospraying of polymer solutions, metal sample collectors are often ineffective in fully removing solvent from sprayed particles and recovering redispersable sprayed particles. Herein, a novel electro spraying system, where sprayed particles were dispersed into laminar flow of dispersant (coagulation liquid), was designed for the nano-encapsulation of protein drugs. Chitosan and polyacrylic acid were used as the encapsulation materials. Aggregation of particles could be prevented by using this new electrospraying system, and unimodal size distribution was observed at an applied voltage between 4~16 kV and a low flow rate. The effects of the applied voltage on mean particle size were not significant on the other hand.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.273-276
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• 2008

Thermoplastic resin takes place stress relaxation and creep according to temperature and time. In room temperature, time dependent deformation (TDD) of polymer was carried out at previous study. In this study, it evaluates time dependent deformation to relate temperature. Nanoscale indents can be used as cells for molecular electronics and drug delivery, slots for integration into nanodevices, and defects for tailoring the structure and properties. Therefore, it is important to control pattern depth for change of indent depth by creep when using Nanoindenter. For evaluating TDD at high temperature, it is occurred thermal-nanoindentation test by changing hold time at maximum load. Temperature is putted at $90^{\circ}C$, hold time at maximum loads are putted at 1, 10, 50, 100, 200, 300 and 500s.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.162-167
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• 2006

Nanofluid is a kind of new engineering material consisting of nanoparticles dispersed in base fluid. Nanofluids could have various applications such as magnetic fluids, heat exchanger working fluids, lubricants, drug delivery and so on in present study, various nanoparticles, such as MWCNT (Multi-walled Carbon Nanotube), fullerene, copper oxide, and silicon dioxide are used to produce nanofluids. As base fluids, DI-water, ethylene glycol, oil, and silicon oil are used. To investigate the thermo-physical properties of nanofluids, thermal conductivity and kinematic viscosity are measured. Stability estimation of nanofluid is conducted with UV-vis spectrophoto-meter. In this study, the high pressure homogenizer is the most effective method to produce nanofluid with the prepared nanoparticle and base fluid. Excellently stable nanofluids are produced with the magnetron sputtering system. Thermal conductivity of nanofluid increases with increasing particle volume fraction except water-based fullerene nanofluid which has lower thermal conductivity than base fluid due to its lower thermal conductivity, 0.4 W/mK. The experimental results can't be predicted by Jang and Choi model.