• Journal of Microbiology and Biotechnology
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• v.26 no.12
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• pp.2098-2105
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• 2016

Massive reserves of methane ($CH_4$) remain unexplored as a feedstock for the production of liquid fuels and chemicals, mainly because of the lack of economically suitable and sustainable strategies for selective oxidation of $CH_4$ to methanol. The present study demonstrates the bioconversion of $CH_4$ to methanol mediated by Type I methanotrophs, such as Methylomicrobium album and Methylomicrobium alcaliphilum. Furthermore, immobilization of a Type II methanotroph, Methylosinus sporium, was carried out using different encapsulation methods, employing sodium-alginate (Na-alginate) and silica gel. The encapsulated cells demonstrated higher stability for methanol production. The optimal pH, temperature, and agitation rate were determined to be pH 7.0, $30^{\circ}C$, and 175 rpm, respectively, using inoculum (1.5 mg of dry cell mass/ml) and 20% of $CH_4$ as a feed. Under these conditions, maximum methanol production (3.43 and 3.73 mM) by the encapsulated cells was recorded. Even after six cycles of reuse, the Na-alginate and silica gel encapsulated cells retained 61.8% and 51.6% of their initial efficiency for methanol production, respectively, in comparison with the efficiency of 11.5% observed in the case of free cells. These results suggest that encapsulation of methanotrophs is a promising approach to improve the stability of methanol production.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.11
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• pp.1335-1341
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• 1988

A pH-ISEFET microprobe for in vivo measurements has been fabricated by combining ISFET (SL-IIS) chip and capillary thin film reference electrode. A two-step TCE oxidation for the gate oxide layer and multilayer encapsulation using silicone rubber and epoxy were specially used for the improvement of the stability and temperature dependence of the ISFET's. The measured sensitivit, response time and temperature dependence of the pH-ISFET microprobes are 50 mV/pH, less than one second, and - 0.01 pH/$^{\circ}$ , respectively. By operating continuously more than 40 days, a long term stability of 0.016 pH/day is obtained. The result of pH monitoring of femoral arterial blood in a rabbit is fairly good agreement with the value of blood gas analysis.

• Food Science and Biotechnology
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• v.18 no.1
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• pp.185-189
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• 2009

Microencapsulation of flavor was carried out by molecular inclusion process using $\beta$-cyclodextrin (${\beta}CD$). ${\beta}CD$-flavor complex was prepared at various flavor-to-${\beta}CD$ ratios (1:6-1:12) to determine the effect of ${\beta}CD$ concentration on the inclusion efficiency. Maximum total oil retention and minimal surface oil content were obtained at flavors to ${\beta}CD$ ratio of 1:10. The physical properties and controlled release pattern of flavors from ${\beta}CD$-flavor complex were measured and compared with spray-dried microcapsules prepared using carbohydrate wall system. ${\beta}CD$-flavor complex showed higher total oil retention and surface oil contents, smaller mean particle size, lower moisture uptake, and higher oxidation stability than spray-dried microcapsule. Oxidative stability of flavor was correlated with hygroscopicity of wall materials. The controlled release mechanism was highly affected by temperature and characteristics of wall materials.

• Korean Journal of Food Science and Technology
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• v.50 no.6
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• pp.636-641
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• 2018

This study was conducted to compare the stability between branched-chain amino acid (BCAA)-encapsulated liposome and double emulsion (DE). Liposome was produced by high-speed homogenization and ultrasonication whereas DE was prepared by homogenizing with surfactants. All samples were fixed at pH 4 and 7 and stored at 4, 25, and $40^{\circ}C$ for 5 days. Encapsulation efficiency and cumulative release rate were measured under $4^{\circ}C$ and at $25^{\circ}C$. The results showed that the size of BCAA-coated liposome was greater at pH 7 than at pH 4. The zeta-potential value of BCAA-coated liposome was greater at pH 4 than at pH 7. It was supposed that the negatively charged liposomes attracted the positively charged BCAAs at pH 4 resulting in the formation of the vesicle with smaller size. Particle size of DE was smaller than $100{\mu}m$. Encapsulation efficiencies of BCAA in DE or liposome were over 97%, approximately, and the cumulative release rates of them were below 30% for 5 days.

• Archives of Pharmacal Research
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• v.28 no.5
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• pp.626-635
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• 2005

Liposome as a carrier of topotecan (TPT), a promising anticancer drug, has been reported in attempt to improve the stability and antitumor activity of TPT. However, the biodistr ibution pattern of TPT liposome in vivo and PEG-modified liposome containing TPT have not been studied systemically. In this paper, the in vitro stability and in vivo biodistribution behavior of several liposomes containing TPT with different lipid compositions and PEG-modification were studied. Compared with the 'fluid' liposome (S-Lip) composed of soybean phosphatidylcholine (SPC), the 'solid' liposome (H-Lip) composed of hydrogenated soybean phosphatidylcholine HSPC decreased the leaking efficiency of TPT from liposome and enhanced the stability of liposome in fetal bovine serum (FBS) or human blood plasma (HBP). The results of biodistribution studies in S$_{180}$ tumor-bearing mice showed that liposomal encapsulation increased the concentrations of total TPT and the ratio of lactone form in plasma. Compared with free TPT, S-Lip and H-Lip resulted in 5- and 19- fold increase in the area under the curve (AUC$_{0\rightarrow\propto}$), respectively. PEG- modified H-Lip (H-PEG) showed 3.7-fold increase in AUC$_{0\rightarrow\propto}$ compared with H-Lip, but there was no significant increase in t$_{1/2}$ and AUC$_{0\rightarrow\propto}$ for PEG-modified S-Lip (S-PEG) compared with S-Lip. Moreover, the liposomal encapsulation changed the biodistribution behavior, and H-Lip and H-PEG dramatically increased the accumulation of TPT in tumor, and the relative tumor uptake ratios were 3.4 and 4.3 compared with free drug, respectively. There was also a marked increase in the distribution of TPT in lung when the drug was encapsulated into H-Lip and H-PEG. Moreover, H-PEG decreased the accumulation of TPT in bore marrow compared with unmodified H-Lip. All these results indicated that the membrane fluidity of liposome has an important effect on in vitro stability and in vivo biodistribution pattern of liposomes containing TPT, and PEG-modified 'solid' liposome may be an efficient carrier of TPT.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.147.1-147.1
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• 2016

Hydrophobic thin films are variously applicable for encapsulation of organic devices and water repulsive glass, etc. In this work, the stability of hydrophobic characteristics of plasma polymerized tetrakis (trimethylsilyloxy) silane (ppTTMSS) thin films were investigated. The films were deposited with plasma enhanced chemical vapor deposition (PECVD) on the glass. The deposition plasma power and deposition pressure was 70 W and 600 mTorr, respectively. Thereafter, deposited films were treated by 248nm KrF excimer laser. Stability of hydrophobic properties of plasma polymerized tetrakis(trimethylsilyloxy)silane film surface was tested by excimer laser irradiation, which is thought to simulate severe outdoor conditions. Excimer laser irradiation cycles changed from 10 to 200 cycles. The chemical structure and hydrophobicity of ppTTMSS films were analyzed by using Fourier transform infrared (FTIR) spectroscopy and water contact angle (WCA) measurement, respectively. Absorption spectra peaks and WCA of excimer laser treated ppTTMSS films did not change notably. These results show that our ppTTMSS films possess stable hydrophobic properties.

• Journal of Pharmaceutical Investigation
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• v.37 no.2
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• pp.113-117
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• 2007

The aim of this study was to investigate the effect of different wall material on the microencapsulation efficiency of microcapsules containing fish oil. The present work reports on the microencapsulation of fish oil by spray drying using hydroxypropyl methylcellulose (HPMC) 2910, maltodextrin, gelatin, sodium caseinate as wall materials. The emulsion stability was assessed by emulsion stability index value (ESI). The microstructural properties of microcapsules was evaluated by scanning electron microscopy (SEM) and microencapsulation efficiency (ME) was assessed by soxhlet method. The highest ESI and ME were observed in the case of a 1:1 gelatin/sodium caseinate ratio and 1:1 glycerin fatty acid ester/lecithin ratio, and ME of microcapsules was increased with increasing the ESI of emulsion. Thus, the stability of emulsion was a critical factor for the encapsulation of fish oil.

• Journal of Pharmaceutical Investigation
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• v.26 no.4
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• pp.291-297
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• 1996

Liposomes of $pSV-{\beta}-Galactosidase$ vector plasmid DNA with various lipid composition were prepared by the thin-film method. Size distribution, shape and the efficiency of plasmid DNA encapsulation were investigated. Effect of sonication time on the plasmid DNA entrapment in liposomes and stability at $4^{\circ}C$ were also examined. Sizes of neutral liposomes were about 100-200 nm and above $1\;{mu}m$, and those of cationic liposomes were about 400-600 nm and above $1\;{mu}m$. Shapes of liposomes entrapped plasmid DNA were spherical. Proper sonication time for better entrapment was below 15 minutes and stability at $4^{\circ}C$ was decreased rapidly after 1 day. Plasmid DNA entrapments of complex liposomes of various lipids were higher than those of liposomes made from one sort of lipid. Plasmid DNA entrapments of cationic liposomes were higher than those of neutral liposomes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.5
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• pp.589-595
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• 2015

Alginates are used to encapsulate various materials, including food, cosmetics, and pharmaceuticals. This study examined the properties and oxidation stability of fish oil capsules manufactured with calcium alginate gels. The fish oil capsules were manufactured by dropping sodium alginate solution and fish oil into a calcium chloride solution through nozzles. The membrane thickness, sphericity, rupture strength and deformation depth of the fish oil capsules were determined. The peroxide value of the fish oil was assayed to determine the oxidation stability of the capsules. The capsules measured approximately 3 mm with a membrane thickness of 90 μm independent of the amount of fish oil added. As the amount of fish oil encapsulated increased, the sphericity, rupture strength and deformation depth of the capsules decreased. The encapsulation efficiency increased until the amount of fish oil was 30%. The oxidation stability of fish oil in capsules was dependent on the type of nozzle, e.g., the oxidation stability of fish oil in capsules made using a double nozzle was greater than with a single nozzle. These results should lead to industrial application of fish oils including eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, as nutraceuticals.

• Applied Biological Chemistry
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• v.42 no.3
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• pp.205-209
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• 1999

Cholesterol plays an important role in various physiological responses and membrane stability. To investigate the effect of cholesterol in liposome on the stability of encapsulated ascorbic acid, the physico-chemical experiments using various amounts of cholesterol-containing liposomes were performed. The encapsulation efficiency of ascorbic acid was decreased with increasing cholesterol content in liposome, whereas size of liposome was increased. Furthermore, the stability of encapsulated ascorbic acid was increased with increasing the content of cholesterol. The stability was not affected by pH. Encapsulated ascorbic acid in liposome stored at $37^{\circ}C$ was rapidly oxidized compared to those stored at $4^{\circ}C$. These results suggest that cholesterol in liposome affects largely to the stability of encapsulated ascorbic acid.