• Journal of Biomedical Engineering Research
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• v.28 no.2
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• pp.244-249
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• 2007

Fluidic conditions for the separation of phases were surveyed in a microfluidic aqueous two-phase extraction system. The infusion ratio between polyethylene glycol (PEG) and dextran solution defines the concentrations of each polymer in micro-channel, which determine the phase-separation. The appropriate ratio between PEG (M.W. 8000, 10%, w/v) and dextran T500 (M.W. 500000, 5%, w/v) in order to perform the separation of phases of both polymers was observed as changing the mixed ratio of both polymers. Based on the fluidic conditions, stable two-phase solutions were obtained within 4% to 8% and 3% to 1% of PEG and dextran, respectively. In addition, the characteristics of the two-phase were discussed. The separation technique studied in the paper can be applied for the implementation of a lab-on-a chip which can detect various biological entities such cells, bacterium, and virus in an integrated manner using built in a biosensor inside the chip.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.6
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• pp.516-521
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• 2005

Drug delivery to the lymphatic system may be important in terms of the treatment with lymphatic involvement, such as tumor metastases and immunization. Especially, drug transport via the intestinal lymphatics after oral administration has been attracted lots of interests. The purpose of this study was to prepare cyclosporin A (CSA)-loaded liposomes, with different characteristics, and evaluate their mucoadhesivity. Three liposome preparations were formulated: cationic stearylamine liposomes (SA-Lip), anionic phosphatidylserine liposomes (PS-Lip), Polymer (chitosan)-coated liposomes (CS-Lip), and characterized. The liposome preparations were found to be spherical in shape, with PS-Lip being the smallest. The liposome preparations exhibited entrapment efficiencies in the order: PS-Lip $(52.5{\pm}2.9%)$ > SA-Lip $(48.8{\pm}3.3%)$ > CS-Lip $(41.7{\pm}4.2%)$. Finally, mucoadhesive tests were carried out using rat intestine, with SA-Lip (67%) showing the best adhesive rate of the three preparations (PS-Lip: 56%, CS-Lip: 61%). These results suggest that a positive charge on the surface of drug carriers may be an important factor for the intestinal drug delivery.

• Macromolecular Research
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• v.17 no.7
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• pp.533-537
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• 2009

This paper introduces a modified electro spinning system for biomedical wound-healing applications. The conventional electrospinning process requires a grounded electrode on which highly charged electro spun ultrafine fibers are deposited. Biomedical wound-healing membranes, however, require a very low charge and a low level of remnant solvent on the electrospun membrane, which the conventional process cannot provide. An electrohydrodynamic process complemented with field-controllable electrodes (an auxiliary electrode and guiding electrodes) and an air blowing system was used to produce a membrane, with a considerably reduced charge and low remnant solvent concentration compared to one fabricated using the conventional method. The membrane had a small average pore size (102 nm) and high porosity (85.1%) for prevention of bacterial contamination. In vivo tests on rats showed that these directly electro spun fibrous membranes produced using the modified electro spinning process supported the good healing of skin bums.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.1-8
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• 2023

Polyethylenimine (PEI) is a cationic polymer that can bind to negatively charged biomaterials such as nucleic acids through strong electrostatic interactions. Based on these properties, PEI has been used as an efficient drug delivery system for a long time. However, the strong cationic nature of PEI has the problem of causing cytotoxicity by non-specific interaction with anionic biological materials in the cells. In order to overcome these problems, many researchers have developed various types of biocompatible PEI-based materials. In this review, we would like to introduce the recent developments of functional PEI and their applications in biomedical research.

• Applied Chemistry for Engineering
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• v.23 no.5
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• pp.462-466
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• 2012

$\beta$-cyclodextrin ($\beta$-CD) polymers were prepared in a strong alkali condition solution (NaOH solution 30% (w/v)) using epichlorohydrin (EPI) as a cross-linker, and the molar ratio of EPI to $\beta$-CD was 10 : 1. The $\beta$-CD content in $\beta$-CD polymers is about 52%. In order to get the photo-responsible and pH-responsible, cinnamic acid was added to be inserted into the cavities of $\beta$-CD due to the hydrophobic interaction. The complex formation was confirmed using transmission electron microscope. The dimerization degree of complexes increased under UV irradiation at $\lambda$ = 365 nm but decreased under the UV irradiation at $\lambda$ = 254 nm. Dynamic light scattering analysis of particle sizes showed that the sizes of complexes did not change with different UV wavelength. Moreover, the complexes were pH-responsible because of the carboxyl group of cinnamic acid, but the size and zeta potential of the complex did not change in strong acid and alkali conditions.

• Polymer(Korea)
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• v.38 no.6
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• pp.815-819
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• 2014

Scaffolds of tissue engineering should be biocompatible and biodegradable for cell attachment, proliferation and differentiation. In the various scaffold fabrication, 3D printing technique can make the three dimensional scaffold with interconnected pores for cell ingrowth. Polycaprolactone (PCL) is biodegradable polyester with a low melting temperature and has been approved by the Food and Drug Administration (FDA). In this study, PCL scaffold was fabricated by 3D bioprinting system and surface modification of PCL scaffold was controlled by NaOH treatment. Morphological change and wetability of NaOH-treated scaffold were observed by SEM and contact angle measurement system. The remnant of PCL treated with NaOH was measured by ATR-FTIR. In vitro study of scaffolds was evaluated with WST-1 and ALP activity assay. NaOH treatment of PCL scaffolds increased surface roughness, hydrophilicity, cell proliferation and osteogenic differentiation. These results indicate that NaOH-treated PCL scaffold made by 3D bioprinting has tissue engineered potential for the development of biocompatible material.

• Journal of Microbiology and Biotechnology
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• v.18 no.10
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• pp.1729-1734
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• 2008

Chitosan, a cationic polysaccharide, has been widely used as a dietary supplement and in a variety of pharmacological and biomedical applications. The antifungal activity and mechanism of action of low molecular weight water-soluble chitosan (LMWS-chitosan) were studied in fungal cells and vesicles containing various compositions of fungal lipids. LMWS-chitosan showed strong antifungal activity against various pathogenic yeasts and hyphae-forming fungi but no hemolytic activity or cytotoxicity against mammalian cells. The degree of calcein leakage was assessed on the basis of lipid composition (PC/CH; 10:1, w/w). Our result showing that LMWS-chitosan interacts with liposomes demonstrated that chitosan induces leakage from zwitterionic lipid vesicles. Confocal microscopy revealed that LMWS-chitosan was located in the plasma membrane. Finally, scanning electron microscopy revealed that LMWS-chitosan causes significant morphological changes on fungal surfaces. Its potent antibiotic activity suggests that LMWS-chitosan is an excellent candidate as a lead compound for the development of novel anti-infective agents.

• Macromolecular Research
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• v.17 no.12
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• pp.1010-1014
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• 2009

Monodispersed microparticles with a poly(D,L-lactide-co-glycolide) (PLGA) core and a poly(ethyl 2-cyanoacrylate) (PE2CA) shell were prepared by Shirasu porous glass (SPG) membrane emulsification to reduce the initial burst release of doxorubicin (DOX). Solution mixtures with different weight ratios of PLGA polymer and E2CA monomer were permeated under pressure through an SPG membrane with $1.9\;{\mu}m$ pore size into a continuous water phase with sodium lauryl sulfate as a surfactant. Core-shell structured microparticles were formed by the mechanism of anionic interfacial polymerization of E2CA and precipitation of both polymers. The average diameter of the resulting microparticles with various PLGA:E2CA ratios ranged from 1.42 to $2.73\;{\mu}m$. The morphology and core-shell structure of the microparticles were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The DOX release profiles revealed that the microparticles with an equivalent PLGA:E2CA weight ratio of 1:1 exhibited the optimal condition to reduce the initial burst of DOX. The initial release rate of DOX was dependent on the PLGA:E2CA ratio, and was minimized at a 1:1 ratio.

• Polymer(Korea)
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• v.38 no.4
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• pp.484-490
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• 2014

Reduced graphene oxide (RGO) was fabricated using gelatin as a reductant, and it could be stably dispersed in gelatin solution without aggregation. A series of RGO/gelatin composite films with various RGO contents were prepared by a solution-casting method. The structure and thermal properties of the RGO/gelatin composite films were characterized by UV-vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA). The addition of RGO enhances the degree of crosslinking of gelatin films and decreases the swelling ability of the gelatin films in water, indicating that RGO/gelatin composite films have a better wet stability than gelatin films. The glass transition temperature ($T_g$) of gelatin films is also increased with the incorporation of RGO. The presence of RGO slightly increases the degradation temperature of gelatin films due to the very low content of RGO in the composite films. Since gelatin is a natural and nontoxic biomacromolecule, the RGO/gelatin composite films are expected to have potential applications in the biomedical field.

• Food Science and Biotechnology
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• v.15 no.6
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• pp.937-941
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• 2006

Chitosan has a wide range of applications in biomedical materials as well as in dietary supplements. Chitosan oligosaccharide with free-amine group (COFa) is an improvement over traditional chitosan that lacks the usual impurities and materials detrimental to the body. Based on a previous study of water soluble chitosan (WSC, chitosan lactate), we investigated the molecular weight (Mw) - dependent absorption phenomena of COFa in vitro and in vivo with various Mws. The absorption of CO Fa was significantly influenced by its molecular weight. As Mw increases, the absorption decreases. The absorption profiles for 5 K COFa (Mw=5 kDa) were observed to be more than 10 times higher than those of high molecular weight chitosan (100 K HWSC Mw=100 kDa) in both in vitro and in vivo transport experiments. Furthermore, the in vitro transport experiment suggested that transcellular transport of the COFa (Mw <10 kDa) through Caco-2 cell layer could occur with a negligible cytotoxic effect. The COFas showed a cytotoxic effect on Caco-2 cells that was dependent on dose and Mw. COFa could be transported transcellularly through the Caco-2 cell layer.