• Macromolecular Research
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• 제16권2호
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• pp.169-177
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• 2008

This paper reports a facile synthesis of new water-soluble poly(ethylene oxide) (PEO)-based amphiphilic block copolymers showing pH sensitive phase transition behaviors. The copolymers were prepared by atom transfer radical polymerization (ATRP) of methacrylamide type of monomers carrying a sulfonamide group using a PEO-based macroinitiator and a Cu(I)Br/$Me_6TREN$ catalytic system in aqueous media. The resulting polymers were characterized by a combination of $^1H$-NMR, size exclusion chromatography, and UV/Visible spectrophotometeric analysis. The micellization of the block copolymers as a drug-loading mechanism in aqueous media using fluorescein salt was examined as a function of pH. The stable micelle formation and its loading efficacy suggest that the block copolymers can be used as precursors for drug-nanocontainers.

• Asian Pacific Journal of Cancer Prevention
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• 제15권1호
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• pp.49-54
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• 2014

Background: Hydrogels are a class of polymers that can absorb water or biological fluids and swell to several times their dry volume, dependent on changes in the external environment. In recent years, hydrogels and hydrogel nanocomposites have found a variety of biomedical applications, including drug delivery and cancer treatment. The incorporation of nanoparticulates into a hydrogel matrix can result in unique material characteristics such as enhanced mechanical properties, swelling response, and capability of remote controlled actuation. Materials and Methods: In this work, synthesis of hydrogel nanocomposites containing magnetic nanoparticles are studied. At first, magnetic nanoparticles ($Fe_3O_4$) with an average size 10 nm were prepared. At second approach, thermo and pH-sensitive poly (N-isopropylacrylamide -co-methacrylic acid-co-vinyl pyrrolidone) (NIPAAm-MAA-VP) were prepared. Swelling behavior of co-polymer was studied in buffer solutions with different pH values (pH=5.8, pH=7.4) at $37^{\circ}C$. Magnetic iron oxide nanoparticles ($Fe_3O_4$) and doxorubicin were incorporated into copolymer and drug loading was studied. The release of drug, carried out at different pH and temperatures. Finally, chemical composition, magnetic properties and morphology of doxorubicin-loaded magnetic hydrogel nanocomposites were analyzed by FT- IR, vibrating sample magnetometry (VSM), scanning electron microscopy (SEM). Results: The results indicated that drug loading efficiency was increased by increasing the drug ratio to polymer. Doxorubicin was released more at $40^{\circ}C$ and in acidic pH compared to that $37^{\circ}C$ and basic pH. Conclusions: This study suggested that the poly (NIPAAm-MAA-VP) magnetic hydrogel nanocomposite could be an effective carrier for targeting drug delivery systems of anti-cancer drugs due to its temperature sensitive properties.

• Macromolecular Research
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• 제16권8호
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• pp.670-675
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• 2008

A series of pH and temperature-responsive (N,N-diethylacrylamide-co-methylacrylic acid) copolymers were synthesized by radical copolymerization and characterized by elemental analysis, Fourier-transform infrared (FT-IR), nuclear magnetic resonance (NMR) $^1H$, $^{13}C$ and LLS. The effects of salt and pH on the phase transition behaviors of the copolymers were investigated by uv. With increasing NaCl concentration, significant salt effects on their phase transition behaviors were observed. UV spectroscopic studies showed that the phase transition became faster with increasing NaCl concentration. In addition, the phase transition behaviors of copolymers were sensitive to pH. The pH and temperature sensitivity of these copolymers would make an interesting drug delivery system.

• 접착 및 계면
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• 제12권2호
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• pp.56-61
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• 2011

본 연구에서는 glucose oxidase와 catalase를 혼합 분산시키지 않고 phenylboronic acid (PBA)을 이용하여 glucose에 반응하는 hydrogel을 합성하였으며, 합성된 hydrogel의 pH 및 glucose 농도 및 이온 농도에 따른 팽윤-수축 거동에 대하여 연구하였다. PBA를 사용하여 합성된 hydrogel은 glucose의 농도에 따라 팽윤비가 증가되는 것으로 나타났으며, pH의 변화에 따라 급격한 부피 변동성을 나타냈다. 그러나 이온농도에 따른 부피의 변화는 상대적으로 작게 나타난 것으로 보아 안정적인 hydrogel임을 확인할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.265-269
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• 2000

Nowadays the hydrophilic polymeric networks (polymer hydrogels) due to the complex of benefit physico-chemical properties attract a wide attention of specialists working in various fields of science, medicine and technology. The special attention of chemists is aimed on so-called stimuli-sensitive or intelligent hydrogels, which can undergo a volume phase transition in response to change in environmental parameters such as temperature, pH, solvent composition, etc [1]. Scientific group of Kazak State National University, Department of Macromolecular Chemistry works in this field [2-5]. Here we report about our achievements on pH-sensitive hydrogens.

• KSBB Journal
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• 제24권5호
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• pp.432-438
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• 2009

본 연구는 환경샘플 중 병원균을 진단하기 위한 목적을 가진다. 최소 챔버 칩에서 환경 샘플 중 병원균을 농축하고 mRNA를 증폭하여 효과적이고 간단한 진단방법을 고안하였다. PDMS로 면적 $1.5\;cm{\times}\;1.5\;cm$, 높이 $100\;{\mu}L$의 칩을 제작하여 유리에 부착시켰다. RNase에 의한 진단 오류 또는 실패를 막고자 RNase away 처리를 하고, RNA와 PDMS의 결합을 막기 위해 BSA 처리를 하였다. 수질에 있는 병원균은 매우 적은 농도로 존재하므로 농축의 과정이 필요하다. 농축의 방법에는 여러 가지가 있으나 본 연구에서는 유리 비드를 칩 내에 삽입하고 저농도의 시료를 주입함으로서 고농도로 농축을 하는 방법을 사용하였다. 그러나 부피가 작은 칩 내에서 수행하기에는 내부 압력이 작용하여 문제가 발생하여 $100\;{\mu}m$의 유리 비드를 사용하고 유리비드의 칩 내부 이탈을 방지하기 위하여 댐을 만들어 농축에 가장 적합한 칩의 형태를 잡았다. 시료의 주입속도에 따라 내부 압력이 상승하여 댐의 기능이 상실하여 유리 비드가 이탈하게 되므로 그것을 방지하기 위하여 칩 내에 댐을 강화하여 만들고 내부압력 증가가 방지되는 최적의 댐을 개발하여 시료의 주입 속도 5 mL/min까지 유리 비드의 이탈을 막았다. 유리 비드에서의 RNA 농축은 pH 5에서 효과적이고 pH가 증가할수록 유리 비드와 RNA의 결합이 끊어지는 현상을 보였으므로 시료에 pH 5의 버퍼를 첨가하여 농축을 진행하고 중성의 NASBA 용액을 주입하여 유리비드에서 탈착된 농축된 고농도의 RNA를 증폭하였다. NASBA는 항온 수조에서 온도에 변화 없이 $41^{\circ}C$에서 1시간 30분 동안 진행하며 증폭된 mRNA는 직접 확인하였다. 이 방법은 LOC 기술을 적용하여 저농도의 시료를 효과적으로 측정할 수 있도록 편리한 바이오 칩을 개발함으로써 대용량의 샘플 중 극 저농도의 대장균을 효과적으로 검출할 수 있는 장점을 가지고 있다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제6권4호
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• pp.205-212
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• 2001

One of the important characteristics of biological systems os their ability to change im-portant properties in response to small environmental signals. The molecular mechanisms that biological molecules utilize to sense and respond provide interesting models for the development of "smart" polymeric biomaterials with biomimetic properties. An important example of this is the protein coat of viruses, which contains peptide units that facilitate the trafficking of the virus into the cell via endocytosis, then out of the endosome into the cytoplasm, and from there into the nucleus, We have designed a family of synthetic polymers whose compositions have been de-signed to mimic specific peptides on viral coats that facilitate endosomal escape. Our biomimetic polymers are responsive to the lowered pH whinin endosomes, leading to distruption of the en-dosomal membrane and release of important biomolecular druges such as DNA, RNA, peptides and proteins to the cytoplasm before they are trafficked to lysosomes and degraded by lysosomal en-zymes. In this article, we review our work on the design, synthesis and action of such smart, pH-sensitive polymers.

• Macromolecular Research
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• 제17권12호
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• pp.1025-1031
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• 2009

Several kinds of biodegradable hydrogels were prepared via in situ photopolymerization of Pluronic F127/poly($\varepsilon$-caprolactone) macromer and acrylic acid (AA) comonomer in aqueous medium. The swelling kinetics measurements showed that the resultant hydrogels exhibited both thermo- and pH-sensitive behaviors, and that this stimuli-responsiveness underwent a fast reversible process. With increasing pH of the local buffer solutions, the pH sensitivity of the hydrogels was increased, while the temperature sensitivity was decreased. In vitro hydrolytic degradation in the buffer solution (pH 7.4, $37^{\circ}C$), the degradation rate of the hydrogels was greatly improved due to the introduction of the AA comonomer. The in vitro release profiles of bovine serum albumin (BSA) in-situ embedded into the hydrogels were also investigated: the release mechanism of BSA based on the Peppas equation was followed Case II diffusion. Such biodegradable dual-sensitive hydrogel materials may have more advantages as a potentially interesting platform for smart drug delivery carriers and tissue engineering scaffolds.

• Journal of Pharmaceutical Investigation
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• 제33권3호
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• pp.179-185
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• 2003

Melatonin (MT) is an indole amide pineal hormone. It has not only very short half-life but also pH-sensitive property. The sustained release dosage form which delivers MT in a circadian fashion over 8 h is clinical value. The purpose of this study is to prepare sugar beads using multiple coating methods and enteric-coated in a sustained release to evaluate in vitro release characteristics in simulated gastric and intestinal fluids. The $Eudragit^{\circledR}$ as a polymer, sustained release membrane, and triethylcitrate (TEC) as a plasticzer were used. Multi-coated melatonin delivery system was composed of sugar, various excipients, $Eudragit^{\circledR}$ and enteric materials (e.g. hydroxy propyl methyl cellulose phthalate, HPMCP), and prepared by fluid bed coater. The dissolution test was carried out using the basket method at a stirring speed of 100 rpm at $37^{\circ}C$ in simulated gastric (pH 1.2) and intestinal fluid (pH 7.4). The released amount of MT was determined by High performance liquid chromatography method. The morhologies of surface and cross section of multi-coated beads were observed by scanning electron microscope. Size of multi-coated sugar beads was ranged over $1000{\sim}1300\;{\mu}m$. The release rate of MT from coated beads was limited in simulated gastric fluid (pH 1.2), but it was sustained in intestinal fluid (pH 7.4) during $3{\sim}8$ hours. The MT beads may provide small-intestine-targeted device for oral delivery. Studies on animal and relative experiment are in process.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 춘계학술대회
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• pp.223-226
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• 1995

Polymers have been developed and applied in many biomedical areas as well as engineering and industrial fields. The first essential to achieve successful development and applications is that properties of such polymer materials would be investigated. In many cases, such investigations are accomplished by observing polymeric behavior arising from the environmental changes such as pH, temperature, and ionic concentration. It has long been known that NMR is extremely sensitive to many biochemical and physical changes occurring in the polymer samples. In the present study we focus our study on NMR Microimaging, which is one of the important NMR applications, to characterize the swelling effect by observing the time dependent spatial variations of polymer specimens. For the samples three kinds of polyvinyl alcohol (PVA) specimens are prepared with different degrees of cross linking density. $^1H$ NMR microimages are acquired as a function of time to visualize the swelling behavior as well as volumetric changes occurring in the specimens. From the acquired time dependent images, the swelling process is exploited.