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Reduction in oxidative stress during cellular responses to chemically functionalised graphene
Yoon, Ok Ja,Jung, Chang Yong,Sohn, Il Yung,Son, Young Min,Hwang, Byeong-Ung,Kim, Il Jin,Lee, Nae-Eung The Royal Society of Chemistry 2014 Journal of Materials Chemistry B Vol.2 No.32
<P>The two-dimensional nanocarbon material graphene (Gr) has been extensively studied due to its many potential biomedical applications including regenerative medicine, drug delivery, bioimaging, and biosensing. The effects of nitrogen-functionalisation on chemically driven Gr (CDG) cellular responses were studied by investigating the generation of reactive oxygen species (ROS) and mitochondrial morphology as well as focal adhesion, shape, proliferation and viability of HeLa cells grown on functionalised CDG (f-CDG) films. The drop casting of CDG nanosheets formed thin CDG films and the formation of nitrogen groups on the f-CDG thin films was mediated by N2plasma treatment without the formation of observable surface defects. N-containing functional groups on the CDG thin films contributed to an increase in hydrophilicity. The proliferation and viability of HeLa cells grown on the f-CDG thin films were enhanced compared to those grown on CDG films alone and control samples. N-functionalisation of CDG thin films effectively reduced the ROS generated from cells on the f-CDG films. These results indicate that N2plasma treatment of CDG is very useful in improving biocompatibility for the bio-application of graphene materials.</P>
Oil Absorption Capacity of Polyethylene Oxide Nanofiber Sheets for Oil Blotting Cosmetic Sheets
Ok Ja Yoon(윤옥자) 한국고분자학회 2016 폴리머 Vol.40 No.6
본 연구는 기존에 시판되고 있는 화장용 기름 흡수 쉬트 제품들과 비교하여 친환경적으로 분해성이 좋고 높은 표면적과 기름 흡수 능력을 가지는 제품 개발를 목적으로 하였다. 유기용매를 사용하지 않고 물에 잘 녹는 양친성 고분자인 폴리에틸렌 옥사이드(PEO)를 전기방사 방법을 이용하여 직경이 다른 두 종류의 나노섬유 쉬트를 개발하였고, 기름 흡수 및 보유 능력, 기름 흡수 후 광 투과성, 표면적, 열적 및 기계적 특성 평가를 수행하였다. 표면적이 높은 PEO 나노섬유 쉬트가 기존 제품과 비교하여 기름 흡수 능력이 11배 증가하였고 열적 및 기계적 특성 또한 향상됨을 확인하였다. 이러한 결과를 통하여 화장품 시장 및 의료 분야에 응용가능성을 확인하였다. Oil blotting cosmetic sheets are important products in the cosmetic and healthcare applications. However, they are limited by their relatively low oil absorption capacity due to their low surface area. In this study, I used an electrospinning method to develop two types of polyethylene oxide (PEO) nanofiber sheets with a large surface area. The properties of sheet, such as the change in the optical transmittance due to oil absorption, the oil absorption capacity, the oil retention capacity, the specific surface area, and thermal and mechanical properties, were evaluated. The oil absorption capacity of PEO nanofiber sheets (25 gauge) was found to be about 11 times greater than that of commercial oil blotting cosmetic sheets and the surface area, as well as the thermal and mechanical properties, increased slightly compared to PEO nanofiber sheets (21 gauge). PEO exhibit ideal characteristics of oil sorbent materials. Therefore, PEO nanofiber sheets with a high surface area are expected to exhibit greater oil absorption capacity than conventional oil blotting cosmetic sheets.
Ok Ja Yoon(윤옥자) 한국고분자학회 2018 폴리머 Vol.42 No.6
다양한 바이오 응용에서 중요한 측정 인자인 과산화 수소(H₂O₂) 센서를 개발하기 위하여, 알지네이트(A) 용액에 수용성 프러시안 블루(s-PB), 그리고 환원된 그래핀 옥사이드(rGO)를 분산시켜 전극 소재를 만들었고 탄소 스크린 프린트 전극에 복합 용액을 젤화 과정을 통해 전극에 고정시켰다. 젤화 과정에서 전극 소재에 남아 있는 염을 제거하기 위하여 충분히 수세를 한 후 실온에서 건조하였다. 전극 소재의 특성은 푸리에 변환 적외선 (FTIR), 전계방출 주사 전자 현미경(FE-SEM)으로 조사하였다. A/s-PB/rGO 전극을 이용한 순환 전류(CV) 측정 결과를 통해 전극으로써 우수한 전기 화학 반응, 안정성, 재현성을 확인하였고, 미분 펄스 볼타 그램(DPV)으로 측정한 산화 전류는 4 mM(S/N = 3)의 검출 한계와 높은 감도(2.7 ㎂ · mM-1· ㎝-2)를 나타내었다. 전기화학적 센서 기반의 전극 개발은 의학 및 환경 응용 분야에서 매우 중요하게 활용될 것으로 판단된다. An electrochemical H₂O₂ sensor was developed using an alginate/water-soluble prussian blue/reduced graphene oxide (A/s-PB/rGO) composite on carbon screen printed electrodes for use in bioapplications. Carbon screenprinted working electrodes were modified with A/s-PB, A/rGO, and A/s-PB/rGO composite solutions by in situ gelation. The composites were characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The cyclic voltammetric measurements made using the electrode modified by A/s-PB/rGOs showed improved electrochemical reaction and stability over the A/s-PB and A/rGO modified electrodes. A two-electron transfer process is indicated at the modified electrode surface. The oxidation current showed a detection limit of 4 mM (S/N = 3) and linear range of 4–28 mM. The A/s-PB/rGO modified electrode provides a tool for high-sensitivity (2.7 ㎂·mM-1·㎝-2) and stable H₂O₂ analyses with a low limit of detection. Development of biosensor-based modified electrodes is important for biomedical and environmental applications.
Cellular Oxidative Stress Response to Graphene Oxide Films Functionalized by NH<sub>3</sub> Plasma
Yoon, Ok Ja,Son, Young Min,Hwang, Byeong-Ung,Sohn, Il-Yung,Lee, Nae-Eung American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.11
<P>Functionalization of graphene oxide (GO) films was performed for the enhancement of bioaffinity by NH3 plasma treatment. Our results demonstrated that the damage free treatments caused a significant change in the surface charge states from negatively charged states with oxygen containing groups on the pristine GO to positively charged states with amine groups on the functionalized GO (f-GO) films. The effects of the conversion of the surface charge states of GO on bioaffinity and biocompatibility were investigated through studies of the reactive oxygen species (ROS) generation mitochondrial morphology and cell proliferation and viability during the growth of HeLa cells on GO and f-GO films. The proliferation and viability of HeLa cells on GO and f-GO films were enhanced compared to those of the control cells. Also the ROS generation on the f-GO (20s treatment) films compared to the other films was reduced. The different physicochemical properties of f-GO induced by plasma-chemical functionalization had a decisive influence on the ROS generation and the proliferation and viability of cells.</P>
Ja Hyun Koo,Jin Pyo Hong,Chae Ok Kim,Il Jae Shin,이종현,Kap Soo Yoon,Ki Woong Kim,Young Deung Kim 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.3
An ultra-thin AlOx tunnel barrier was prepared to obtain high quality of magnetic tunnel junctions (MTJs) using a remote rf oxidation process. The tunnel barrier was schematically investigated as a function of mixed gas ratio with Ar and O2, and various oxidation times. Electrical breakdown voltage and magneto-resistance of MTJs were about 1.2 V and 22 %, respectively. Especially the dielectric properties of our tunnel barriers were optically analyzed by using a surface plasmon resonance spectroscopy (SPRS) to observe the oxidation state inside the barrier. The observed SPRS result exhibits that the AlOx tunnel barrier was a bulk-property of Al2O3 at optimum oxidation time of 75 s, resulting in the highest magnetoreistance.