• KSBB Journal
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• v.18 no.5
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• pp.385-392
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• 2003

Biodegradable poly (L-lactide) (L-PLA) solution in methylene chloride was precipitated into microparticles by using supercritical carbon dioxide modified with polar cosolvents. The effects of the amount of polar cosolvents, solution concentration, temperature, and solution flow rate on the formation of microparticles were investigated. The mean particle size was found to increase with the increase of solution concentration and flow rate. It was also observed that the particle size not only increases but the size distribution also becomes less uniform as the temperature increases. The percent recovery of microparticles was found to be 30∼40% at all experimental conditions. The supercritical carbon dioxide modified with methanol and ethanol was employed to enhance the recovery, resulting in significant improvement up to about 80 and 70%, for methanol and ethanol, respectively. Furthermore, the mean diameter of L-PLA microparticles was found to be less than 1 $\mu\textrm{m}$ for both cosolvents.

• Polymer(Korea)
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• v.26 no.1
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• pp.128-138
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• 2002

1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU, Carmustine)-loaded poly(D, L-lactide-co-glycolide) (PLGA, lactide/glycolide mole ratio 75 : 25) microparticles were prepared and fabricated into wafers in an attempt to study the possibility for the treatment of malignant glioma by direct inserting the wafers to the tumor or the cavity remained after surgical resection of the tumor. SEM observation of the microparticles prepared by spray drying method revealed that the microparticles were spherical, i. e. microspheres. Significant reduction of the crystallinity of BCNU encapsulated in PLGA was confirmed by X-ray diffraction and differential scanning calorimetry analyses of the BCNU-loaded PLGA microparticles. Release pattern of BCNU was dependent on several preparation parameters, such as the molecular weight and concentration of PLGA, and initial BCNU loading amount, etc. In vitro release of BCNU was prolonged over 8 weeks with close to zero-order release pattern after initial burst effect. Observations of morphological change of wafers and pH change of release media during release test period confirmed that hydration and degradation of PLGA would be facilitated with an increase of BCNU-loading amount.

• Korean Journal of Medicinal Crop Science
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• v.8 no.3
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• pp.225-233
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• 2000

There was not noticeable differences in decreasing blood alcohol concentrations between Korea and China-produced Hovenia dulcis $T_{HUNB}$, showing only 1-2 % higher decreasing rate for Korea-produced seed extracts than those from China. It was also found that the blood alcohol decreasing ability was greatly enhanced by partitioning the crude extracts produced from both places. The both extracts (crude and partitioned) accelerated the reducing rate of blood alcohol concentrations down to 1-2 hours, compared to that of control (taking only ethanol). The crude extracts from imported seeds seemed to have slightly better effect on improving in vivo ADH and ALDH activities than domestic ones; however, not for partitioned extracts. It was interesting that the partitioned extracts from both countries enhanced ADH enzyme activity up to 60% than the crude, compared to the control, while ALDH activity was not much affected by the partitioned extracts. It was also confirmed that both ADH and ALDH activities were well balanced in controlling blood alcohol concentration maintaining 28-29% of enzyme activities in vivo. The extracts proved to have better effect on enhancing ALDH activity than ADH activity, which is one of possible explanation that Hovenia dulcis $T_{HUNB}$ can effectively relieve the hangover by fast decreasing acetaldehyde concentration in the liver and blood. GST activity was also increased in the range of 120 to 300% by adding crude or partitioned extracts from both countries; however, there was no difference in enhancing GST activity between the extracts from two countries. The extracts showed competitive inhibition with GST activity, showing the reduction of enzyme activity at higher than 0. 6 (g/L) of the imported extracts.

• The Korean Journal of Pesticide Science
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• v.16 no.2
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• pp.187-193
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• 2012

Acute toxicity, water resolvability and short term reproduction test on Japanese medaka (Oriyzias latipes) for evaluating alachlor susceptibility to endocrine system were studied. Alachlor is known for suspected endocrine distruptors. As the results of tests, $LC_{50}$ (Median lethal concentration) was determined as 2.36 (1.994~2.805) mg/L, and test water replaced at 7 day intervals as its water resolvability was less than 20% in 7 days. The short term reproduction tests on Japanese medaka (Oriyzias latipes) were performed with a solvent control group, a treated group (alachlor concentrations of 0.02, 0.04, 0.11, 0.27, 0.68 ppm) and a positive control group (17 ${\beta}$ estradiol, 0.01, 0.1, 0.5 ppb). The number of spawning and embryo rates were declined in a alachlor-dose dependent manner, and the number of unfertilized eggs rates were in contrast increased depending on the concentrations. Further study should be needed to confirm whether the adverse effects may be effected by the concentrations. Additionally, alachlor was evaluated as a non-vitellogenin by the result of a test of significance of the vitellogenin content test for determination of the effect of estrogen among the endocrine disruptors.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.4 no.1
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• pp.31-41
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• 1971

The present study was directed to define the degradation pattern of the nucleotides and their related compounds in the muscle of anchovy during drying. Three kinds of samples, fresh, sun dried and boiled-and-dried anchovy, were prepared and the contents of nucleotides and related compounds of samples were determined by ion exchange chromatography. The results obtained are summarized as follows: Almost all of ATP disappeared in both muscle of sun dried and boiled-and-dried anchovy, although the initial content of ATP in fresh muscle was very low ($1.8{\mu}moles/g$, dry basis). But the remainning amount of ADP was considerably high while the other nucleotide almost entirely disappeared. This suggested that the residual ADP is responsible to the 'bound nucleotide' of myofibrils. In general, AMP content was comparatively lower than that of other nucleotides. Among three samples, the boiled-and-dried sample showed relatively higher AMP value than others. The amount of IMP remained in muscle remarkably varied between the boiled-and-dried anchovy and sun dried anchovy, the former's value being sixteen times higher than that of latter. In the contents of inosine and hypoxanthine, the sun dried anchovy marked an exceedingly high value equivalent to 2.7 times of the boiled-and-dried anchovy. In comparison of the ratio of inosine and hypoxanthine, hypoxanthine was accumulating in boiled-and-dried anchovy whereas inosine was in the sun-dried anchovy. Eighty three percent of total nucleotides in the fresh anchovy retained in the boiled-and-dried anchovy and IMP ratio in total nucleotides was $73\%$. On the contrary, the sun dried anchovy showed barely $10\%$ of retention rate and IMP ratio was only $38\%$. Considered from the flavor quality of dried anchovy, so far as concerned IMP content, it may be said that the boiled-and-drying method is more favorable process for dried product of anchovy than the sun-drying method.

• Polymer(Korea)
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• v.34 no.3
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• pp.253-260
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• 2010

In this study, we prepared and evaluated a series of biocompatible and biodegradable block copolymer hydrogels with a delayed swelling property for tissue expander application. The hydrogels were synthesized via a radical crosslinking reaction of poly(ethylene glycol) (PEG) diacrylate and poly(D,L-lactide-co-glycolide)-poly(ethylene glycol)-poly(D,L-lactide-co-glycolide)(PLGA-PEG-PLGA) triblock copolymer diacrylate as a swelling/degradation controller (SDC). For the synthesis of various SDCs that can lead to different degradation and swelling properties, various PLGA-PEG-PLGA triblock copolymers with different LA/GA ratios and different PLGA block lengths were synthesized and modified to have terminal acrylate groups. The resultant hydrogels were flexible and elastic even in the dry state. The in vitro degradation tests showed that the delayed swelling properties of the hydrogels could be modulated by varying the chemical composition of the biodegradable crosslinker (SDC) and the block ratio of SDC/PEG. The histopathologic observation after implantation of hydrogels in mice was performed and evaluated by macrography and microscopy. Any significant inflammation or necrosis was not observed in the implanted tissues. Due to their biocompatibility, elasticity, sufficient swelling pressure, delayed swelling and controllable degradability, the hydrogels could be useful for tissue expansion and other biomedical applications.

• Polymer(Korea)
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• v.35 no.4
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• pp.289-295
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• 2011

Biomaterials for retinal tissue engineering must demonstrate several critical features for potential utility, including mechanical integrity, biocompatibility, and slow biodegradation. Silk film biomaterials were designed and characterized to meet these functional requirements. We prepared natural/synthetic hybrid silk/PLGA films using 0, 10, 20, 40, and 80 wt% of silk by a solvent evaporation method. MIT assay was used to confirm the number of cells attached on film at 1, 2, and 3 days, respectively. The morphology of cellular adhesion on films was also confirmed by scanning electron microscope (SEM). RT-PCR was conducted to confrrm mRNA expression of retinal pigment epithelitun (RPE) using RPE65 as a RPEs marker and the expression of cytokeratin were determined by immunofluorescence staining. We confirmed that the silk/PLGA film of 20~40 wt% silk was superior for the adhesion and proliferation of RPEs.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.50 no.2
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• pp.103-110
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• 2024

Lipid nanoparticles (LNPs) are a stable and an effective system that protects cell-impermeable biologically active compounds such as nucleic acids, proteins, and peptides against degradation caused by subtle environmental changes. This study focuses on developing LNPs encapsulating gallic acid (GA), an antioxidant, to effectively prolong the half-life of tetrahexyldecyl ascorbate (THDC), a oil-soluble vitamin C derivative. These LNPs were synthesized in small, uniform sizes at room temperature and pressure conditions using a microfluidics chip. Compared to liposomes manufactured under high pressure and high temperature conditions through conventional microfluidizers, LNPs manufactured through microfluidics chips had excellent dispersion and temperature stability, and improved skin absorption as well as improved oxidative stability of fat-soluble vitamin C derivatives. Future studies will focus on ex vivo and in vivo evaluations to study skin improvement to further validate these results.

• Journal of Sensor Science and Technology
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• v.2 no.1
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• pp.41-48
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• 1993

An ISFET urea sensor was fabricated by immobilizing the urease using polyurethane on the $H^{+}$ sensing $Si_{3}N_{4}$ thin film of pH-ISFET. The sensor could determine the urea concentration $1{\sim}50$ mg/dl with fast response of $3{\sim}5$ min. and good repeatability. For its application to clinical analysis, the results of the urea measurements in blood plasma using ISFET urea sensor were compared with these of conventional Urease-Indophenol method.

• Tuberculosis and Respiratory Diseases
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• v.50 no.4
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• pp.426-436
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• 2001

Background : Chronic obstructive pulmonary disease(COPD) is one of the major contributors to morbidity and mortality among the adult population. Cigarette smoking(CS) is undoubtedly the single most important factor in the pathogenesis of COPD. However, its mechanism is unclear. The current hypothesis regarding the pathogenesis of COPD postulates that an imbalance between proteases and antiproteases leads to the destructive changes in the lung parenchyma. This study had two aims. First, to evaluate the effect of CS exposure on histologic changes of the lung parenchyme, and second, to evaluate the effect of CS exposure on the expression of the gelatinolytic enzymes in BAL fluid cells in guinea pigs. Methods : Two groups of five guinea pigs were exposed to the whole smoke of 20 commercial cigarettes per day, 5 hours/day, 5 days/week, for 6weeks, and 12 weeks, respectively, using a smoking apparatus. Five age-matched guinea pigs exposed to room air were used as controls. Five or more sections were microscopically extamined(${\times}400$) and the number of cellular infiltration of the alveolar wall was measured in order to evaluate the effect of CS exposure on the histologic changes of lung parenchyme. The statistical significance was analyzed by a linear regression method. To evaluate the expression of the gelatinolytic enzymes in intraalveolar cells, BAL fluid was obtained and the intraalveolar cells were separated by centrifugation (500 g for 10 min at $4^{\circ}C$). Two sets of culture plates were loaded with $1{\times}10^6$ intraalveolar cells. One plate, contained O.1mM EDTA, a inhibitor of matrix metalloproteases(MMPs), and the other plate had no EDTA. Both plates were incubated for 48 hours at $37^{\circ}C$. After incubation, gelatinolytic protease expression in the supernatants was analyzed by gelatin zymography. Results : At the end of CS exposure, the level of blood carboxy Hb had increased significantly(4.1g/dl in control group, 24g/dl immediately after CS exposure, 18g/dl 30 min after CS exposure, 15g/dl 1 hour after CS exposure). Alveolar inflammatory cells were identified in the CS exposed guinea pigs. The number of alveolar cellular cells observed in a microscopic field ($400{\times}$) was $121.4{\pm}7.2$, $158.0{\pm}20.2$, $196.8{\pm}32.8$, in the control, the 6 weeks, and the 12 weeks group, respectively. The increased extent of inflammatory cellular infiltration of the lung parenchema showed a statistically significant linear relationship with the duration of CS exposure(p=0.001, $r^2=0.675$). Several types of gelatinolytic enzymes in the intraalveolar cells of CS exposed guinea pigs were expressed, of which some were inhibited by EDT A. However, the gelatinolytic enzymes were not expressed in the control groups. Conclusion : CS exposure increases inflammatory cellular infiltration of the alveolar wall and the expression of gelatinolytic proteases in guinea pigs. EDTA inhibits some of the gelatinolytic proteases. These findings suggest a possibility that CS exposure may increase MMP expression in the lungs of guinea pigs.