• Journal of Pharmaceutical Investigation
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• 제38권4호
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• pp.229-234
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• 2008

In the present study, chitosan-glycerophosphate sodium salt solution as a thermosensitive system (TSS) was used to formulate a temperature-sensitive drug delivery system (TSDDS) containing acetaminophen (AAP). The optimized TSS was prepared by measuring gelation temperature, gelation time and rheological properties of TSS. The optimized gelation temperature and time of TSS were $36^{\circ}C$ and 100 seconds, respectively. The viscosity of TSS was also suitable for maintaining gel structure at $37.2^{\circ}C$. The release profiles of TSDDS in PBS/pH 7.4 with various apparatuses and mass loss of TSDDS were investigated. The time required to release 50% of AAP from TSDDS ($t_{50%}$) was 120 min with the formation of pore on the surfaces, which was 2 times longer than that from AAP-chitosan gel. In addition, TSDDS was degraded approximately 80% within 4 hr and then degraded slowly for 20 hrs. In conclusion, AAP-TSS (TSDDS) formulated in this study might be suitable for some specific uses such as subcutaneous injection and rectal formulation.

• 폴리머
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• 제30권1호
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• pp.1-9
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• 2006

생체의료용 기능성 고분자재료의 개발에 관한 연구를 고분자의 기능성, 생체적합성 및 생분해성을 토대로 다루었다. 본 연구실에서 합성한 기능성 생분해 고분자들을 비롯하여 생분해성 고분자 생체재료, 온도 감응성 고분자재료, 양이온성 고분자재료, 비축합성 고분자 생체재료, 조직공학을 위한 생체고분자 DNA 매트릭스 및 RNAi 기법을 위한 고분자 등의 기능성 고분자 생체재료에 관련된 연구들을 정리하고, 가까운 장래에 의료용으로 이용될 수 있는 기능성 생체고분자에 대한 연구들을 제안하였다.

• Bulletin of the Korean Chemical Society
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• 제24권7호
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• pp.901-905
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• 2003

The lower critical solution temperature (LCST) of thermosensitive poly(organophosphazenes) with methoxypoly(ethylene glycol) (MPEG) and amino acid esters as side groups was studied as a function of saccharide concentration in aqueous solutions of mono-, di-, and polysaccharides. Most of the saccharides decreased the LCST of the polymers, and the LCST decrease was more prominently observed by saccharides containing a galactose ring, such as D-galactose, D-galactosamine and D-lactose, and also the polysacccharide, 1-6-linked D-dextran effectively decreased the LCST of the polymers. Such an effect was discussed in terms of intramolecular hydrogen bonding of saccharides in polymer aqueous solution. The saccharide effect was found to be almost independent on the kinds of the amino acid esters and MPEG length of the polymers. Such a result implies that the polymer-saccharide interaction in aqueous solution is clearly influenced by the structure of sacchardes rather than by that of the polymers. The acid saccharides such as D-glucuronic and D-lactobionic acid increased the LCST, which seems to be due to their pH effect.

• 미생물학회지
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• 제29권6호
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• pp.392-396
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• 1991

Pseudomonas sp. DJ77의 chromosomal DNA로부터 6.9kb XhoI 절편 상에 존재하는 phenanthrene 분해에 관련된 유전자군을 vector pBLUESCRIPT SK(+)에 클로닝하였다. 이렇게 얻은 재조합 plasmid인 pHENX7을 가지고 있는 JM101 균주는 3-methylcarechol을 노란색의 meta-cleavage 화합물로 전환할 수 있었다. 그러나 삽입된 절편의 방향이 반대가 되도록 제조한 pHENX7은 extradiol dioxygenase 활성을 나타내지 않기 때문에 전사방향을 알 수 있었다. pHENX7과 이의 듀도체들을 지니는 JH101균주에서 PhnC(24kDa), PhnD(31KDa), PhnE(34kDa), PhnF(KDa)의 4 polypeptide를 확인 할 수 있었고 개개의 유전자의 위치와 범위를 알 수 있었다. 유전자 순서는 phnC-phnD-phnE-phnF-phnG이었으며, phnC, phnD, phnE, phnF, phnG는 각기 glutathione S-transferase, meta-cleavage compound hydrolase extradiol dioxygenase, meta-cleavage compound dehydrogenase의 유전자이었다.

• 환경생물
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• 제20권4호
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• pp.277-286
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• 2002

An increase in the overall biological effect under the combined action of ionizing radiation with another inactivating agent can be explained in two ways. One is the supposition that synergism may attribute to a reduced cellular capacity of damn-ge repair after the combined action. The other is the hypothesis that synergism may be related to an additional lethal or potentially lethal damage that arises from the interaction of sublesions induced by both agents. These sublesions ave considered to be in-effective when each agent is applied separately. Based on this hypothesis, a simple mathematical model was established. The model can predict the greatest value of the synergistic effect, and the dependence of synergy on the intensity of agents applied, as well. This paper deals with the model validation and the peculiarity of simultaneous action of various factors with radiation on biological systems such as bacteriophage, bacterial spores, yeast and mammalian cells. The common rules of the synergism aye as follows. (1) For any constant rate of exposure, the synergy can be observed only within a certain temperature range. The temperature range which synergistically increases the effects of radiation is shifted to the lower temperature fer thermosensitive objects. Inside this range, there is a specific temperature that maximizes the synergistic effect. (2) A decrease in the exposure rate results in a decrease of this specific temperature to achieve the greatest synergy and vice versa. For a constant temperature at which the irradiation occurs, synergy can be observed within a certain dose rate range. Inside this range an optimal intensity of the physical agent may be indicated, which maximizes the synergy. As the exposure temperature reduces, the optimal intensity decreases and vice versa. (3) The recovery rate after combined action is decelerated due to an increased number of irreversible damages. The probability of recovery is independent of the exposure temperature for yeast cells irradiated with ionizing or UV radiation. Chemical inhibitors of cell recovery act through the formation of irreversible damage but not via damaging the recovery process itself.

• Molecules and Cells
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• 제43권6호
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• pp.572-580
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• 2020

Transient receptor potential ankyrin 1 from rattlesnakes (rsTRPA1) and boas (bTRPA1) was previously proposed to underlie thermo-sensitive infrared sensing based on transcript enrichment in infrared-sensing neurons and hyper-thermosensitivity expressed in Xenopus oocytes. It is unknown how these TRPA1s show thermosensitivities that overwhelm other thermoreceptors, and why rsTRPA1 is more thermosensitive than bTRPA1. Here, we show that snake TRPA1s differentially require Ca²⁺ for hyper-thermosensitivity and that predisposition to cytosolic Ca²⁺ potentiation correlates with superior thermosensitivity. Extracellularly applied Ca²⁺ upshifted the temperature coefficients (Q10s) of both TRPA1s, for which rsTRPA1, but not bTRPA1, requires cytosolic Ca²⁺. Intracellular Ca²⁺ chelation and substitutive mutations of the conserved cytosolic Ca²⁺-binding domain lowered rsTRPA1 thermosensitivity comparable to that of bTRPA1. Thapsigargin-evoked Ca²⁺ or calmodulin little affected rsTRPA1 activity or thermosensitivity, implying the importance of precise spatiotemporal action of Ca²⁺. Remarkably, a single rattlesnake-mimicking substitution in the conserved but presumably dormant cytosolic Ca²⁺-binding domain of bTRPA1 substantially enhanced thermosensitivity through cytosolic Ca²⁺ like rsTRPA1, indicating the capability of this single site in the determination of both cytosolic Ca²⁺ dependence and thermosensitivity. Collectively, these data suggest that Ca²⁺ is essential for the hyper-thermosensitivity of these TRPA1s, and cytosolic potentiation by permeating Ca²⁺ may contribute to the natural variation of infrared senses between rattlesnakes and boas.

• 폴리머
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• 제28권4호
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• pp.344-351
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• 2004

온도에 반응하는 고분자로서 폴리(에틸렌 글리콜)을 기본으로 다이블록 및 트리블록 폴리에스테르 공중합체들은 비독성과 생체적합성 그러고 생분해성 특징 때문에 주사제형의 약물전달체로서 많은 응용이 이루어지고 있다. 본 연구에서는 다이블록 공중합체를 이용한 새로운 솔-젤 전이 현상을 갖는 고분자를 준비하고자, 평균분자량 750g/mole의 메톡시 폴리(에틸렌 글리콜)과 카프로락톤을 실온에서 HCI $.$ Et$_2$O 존재 하에서 개환중합을 실시하였다. 합성된 고분자는 시차주사열량계와 X-선 회절기를 이용하여 특성을 분석하였고, 수용액상에서의 고분자 용액은 실온에서 신체온도로 온도를 상승시키면 졸에서 겔 상으로의 상변화를 보였다. 신체온도 부근에서의 겔 형성을 확인하기 위하여 20 W% 졸 상태의 고분자용액을 쥐의 피하에 주입한 결과 분산 없이 겔이 잘 형성되었고 2개월 간 겔이 유지됨을 확인하였다. 이러한 연구 결과로, 새로운 솔-젤 상전이 현상을 보이는 다이블록 공중합체를 합성하였고, 주사형 이식 재료로의 가능성을 확인하였다.

• Macromolecular Research
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• 제16권6호
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• pp.517-523
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• 2008

A RGD (Arg-Gly-Asp) conjugated chitosan hydrogel was used as a cell-supporting scaffold for articular cartilage regeneration. Thermosensitive chitosan-Pluronic (CP) has potential biomedical applications on account of its biocompatibility and injectability. A RGD-conjugated CP (RGD-CP) copolymer was prepared by coupling the carboxyl group in the peptide with the residual amine group in the CP copolymer. The chemical structure of RGD-CP was characterized by $^1H$ NMR and FT IR. The concentration of conjugated RGD was quantified by amino acid analysis (AAA) and rheology of the RGD-CP hydrogel was investigated. The amount of bound RGD was $0.135{\mu}g$ per 1 mg of CP copolymer. The viscoelastic parameters of RGD-CP hydrogel showed thermo-sensitivity and suitable mechanical strength at body temperature for cell scaffolds (a> 100 kPa storage modulus). The viability of the bovine chondrocyte and the amount of synthesized glycosaminoglycans (GAGs) on the RGD-CP hydrogels were evaluated together with the alginate hydrogels as a control over a 14 day period. Both results showed that the RGD-CP hydrogel was superior to the alginate hydrogel. These results show that conjugating RGD to CP hydro gels improves cell viability and proliferation, including extra cellular matrix (ECM) expression. Therefore, RGD conjugated CP hydrogels are quite suitable for a chondrocyte culture and have potential applications to the tissue engineering of articular cartilage tissue.

• 대한수의학회지
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• 제21권1호
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• pp.25-31
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• 1981

A total of 250 enteric bacteria (148 Escherichia coli, 41 Klebsiella pneumoniae, 46 Enterobacter spp. and 15 Proteus spp.) isolated from bovine udder infections in 1979 through 1980 were examined for drug resistance and prevalence of R. plasmids. The drug tested were streptomycin (SM), kanamycin (KM), ampicillin (AP), chloramphenicol (CP), tetracycline (TC), gentamicin (GM), oxolinic acid (OA) and nalidixic acid (NA). The detection of R. plasmids was performed with Escherichia coli ML 1410 NAr as the recipient. Of the 148 Escherichia coli isolated, 68(45.9%) were found to be resistant to one or more drugs tested, and about 50% of the resistant strains were multiply resistant. of the 68 drugresistant strains, 13(19.1%) were found to carry R. plasmids which were capable of performing a conjugal transfer. CP resistance was transfered together with the other resistance. Of 41 strains of Klebsiella pneumoniae isolated, 90.2% were resistant to the drugs, alone or in combination thereof. Strains resistant to AP and TC were 63.4%, and 48.8%, respectively. R. plasmids were detected in 78.4% of the drug-resistant strains, and these strains transfered all or a part of their drug resistance pattern. AP and CP resistance were transfered in 100% of AP and CP-resistant strains. Eleven (37.9%) of 29 R. plasmids showed a thermosensitive transfer. Of the 46 strains of Enterobacter spp. isolated, 37(80.4%) were resistant to the drugs tested. A high percentage of resistance was noted for AP(65.2%). All strains resistant to four or more drugs transferred their resistances to Escherichia coli ML 1410, but strains resistant to three or fewer drugs did not transfer the resistances. All of the 15 Proteus strains isolated were resistant to more than two drugs. of them, 6 were quadruple resistance to SM, KM, CP and TC, and 9 were double one to AP and TC. Three (20.0%) of the drug-resistant isolates had R.plasmids conferring AP and TC resistance. GM, OA and NA of the drugs tested were very active to all of 250 Gram-negative enteric bacteria isolated from bovine udder infections.

• Journal of Microbiology and Biotechnology
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• 제32권4호
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• pp.522-530
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• 2022

In this study we aimed to develop novel ZnO-NP/chitosan/β-glycerophosphate (ZnO-NP/CS/β-GP) antibacterial hydrogels for biomedical applications. According to the mass fraction ratio of ZnO-NPs to chitosan, mixtures of 1, 3, and 5% ZnO-NPs/CS/β-GP were prepared. Using the test-tube inversion method, scanning electron microscopy and Fourier-transform infrared spectroscopy, the influence of ZnO-NPs on gelation time, chemical composition, and cross-sectional microstructures were evaluated. Adding ZnO-NPs significantly improved the hydrogel's antibacterial activity as determined by bacteriostatic zone and colony counting. The hydrogel's bacteriostatic mechanism was investigated using live/dead fluorescent staining and scanning electron microscopy. In addition, crystal violet staining and MTT assay demonstrated that ZnO-NPs/CS/β-GP exhibited good antibacterial activity in inhibiting the formation of biofilms and eradicating existing biofilms. CCK-8 and live/dead cell staining methods revealed that the cell viability of gingival fibroblasts (L929) cocultured with hydrogel in each group was above 90% after 24, 48, and 72 h. These results suggest that ZnO-NPs improve the temperature sensitivity and bacteriostatic performance of chitosan/β-glycerophosphate (CS/β-GP), which could be injected into the periodontal pocket in solution form and quickly transformed into hydrogel adhesion on the gingiva, allowing for a straightforward and convenient procedure. In conclusion, ZnO-NP/CS/β-GP thermosensitive hydrogels could be expected to be utilized as adjuvant drugs for clinical prevention and treatment of peri-implant inflammation.