Electrically conductive graphene/polyacrylamide hydrogels produced by mild chemical reduction for enhanced myoblast growth and differentiation

Jo, Hyerim,Sim, Myeongbu,Kim, Semin,Yang, Sumi,Yoo, Youngjae,Park, Jin-Ho,Yoon, Tae Ho,Kim, Min-Gon,Lee, Jae Young Elsevier 2017 Acta Biomaterialia: structure-property-function re Vol.48 No.-

<P><B>Abstract</B></P> <P>Graphene and graphene derivatives, such as graphene oxide (GO) and reduced GO (rGO), have been extensively employed as novel components of biomaterials because of their unique electrical and mechanical properties. These materials have also been used to fabricate electrically conductive biomaterials that can effectively deliver electrical signals to biological systems. Recently, increasing attention has been paid to electrically conductive hydrogels that have both electrical activity and a tissue-like softness. In this study, we synthesized conductive graphene hydrogels by mild chemical reduction of graphene oxide/polyacrylamide (GO/PAAm) composite hydrogels to obtain conductive hydrogels. The reduced hydrogel, r(GO/PAAm), exhibited muscle tissue-like stiffness with a Young’s modulus of approximately 50kPa. The electrochemical impedance of r(GO/PAAm) could be decreased by more than ten times compared to that of PAAm and unreduced GO/PAAm. <I>In vitro</I> studies with C2C12 myoblasts revealed that r(GO/PAAm) significantly enhanced proliferation and myogenic differentiation compared with unreduced GO/PAAm and PAAm. Moreover, electrical stimulation of myoblasts growing on r(GO/PAAm) graphene hydrogels for 7days significantly enhanced the myogenic gene expression compared to unstimulated controls. As results, our graphene-based conductive and soft hydrogels will be useful as skeletal muscle tissue scaffolds and can serve as a multifunctional platform that can simultaneously deliver electrical and mechanical cues to biological systems.</P> <P><B>Statement of Significance</B></P> <P>Graphene-based conductive hydrogels presenting electrical conductance and a soft tissue-like modulus were successfully fabricated via mild reduction of graphene oxide/polyacrylamide composite hydrogels to study their potential to skeletal tissue scaffold applications. Significantly promoted myoblast proliferation and differentiation were obtained on our hydrogels. Additionally, electrical stimulation of myoblasts via the graphene hydrogels could further upregulate myogenic gene expressions. Our graphene-incorporated conductive hydrogels will impact on the development of new materials for skeletal muscle tissue engineering scaffolds and bioelectronics devices, and also serve as novel platforms to study cellular interactions with electrical and mechanical signals.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A report of 20 unrecorded bacterial species isolated from the coastal area of Korean islands in 2022

Hyerim Cho,Yeonjung Lim,Sumin Kim,Hyunyoung Jo,김미래,조장천 국립생물자원관 2023 Journal of species research Vol.12 No.2

Bacterial communities inhabiting islands play a vital role in the functioning and formation of a unique, isolated ecosystem. Nevertheless, there has been a lack of systematic research on the indigenous microbiological resources of the islands in Korea. To excavate microbial resources for further studies on the metabolism and biotechnological potential, a standard dilution plating was applied to coastal seawater samples collected from islands along the west coast of the Korean Peninsula, including Deokjeokdo, Baengnyeongdo, and Daebudo in 2022. A total of 2,007 bacterial strains were isolated from the samples as single colonies and identified using 16S rRNA gene sequence analyses. A total of 20 strains, with ≥98.7% 16S rRNA gene sequence similarity to bacterial species having validly published names but not reported in Korea, were designated as unrecorded bacterial species in Korea. The unrecorded bacterial strains were phylogenetically diverse and belonged to four phyla, five classes, 12 orders, 17 families, and 18 genera. The unreported species were assigned to Algimonas, Amylibacter, Notoacmeibacter, Roseibium, and Terasakiella of the class Alphaproteobacteria; Alteromonas, Congregibacter, Marinagarivorans, Marinicella, Oceanospirillum, Psychromonas, Thalassotalea, Umboniibacter, and Vibrio of the class Gammaproteobacteria; Lutibacter and Owenweeksia of the class Flavobacteriia; Paenibacillus of the class Bacilli; and Pelagicoccus of the class Opitutae. The taxonomic characteristics of the unreported species, including morphology, biochemistry, and phylogenetic position are provided in detail.

멀티모달 스파이킹 뉴럴 네트워크의 성능 분석

한혜림(Hyerim Han),조정희(Jeonghee Jo),박종길(Jongkil Park),박성식(Seongsik Park) 대한전자공학회 2023 대한전자공학회 학술대회 Vol.2023 No.6

Multimodal models have been studied as promising model that can overcome the disadvantages of the unimodal models. However, not much research has been conducted on the effectiveness of multimodality in spiking neural networks (SNNs), which have been considered a next-generation artificial neural network for their energy efficiency. Thus, in this paper, we analyzed the effectiveness through experiments on modality, model size, and noise. According to our analysis, we validated that SNNs showed greater effectiveness in multimodality than DNNs.

메타버스 가상농장 ‘메타팜’의 효과 분석과 활용 방안

조예슬(Yeseul Jo),정환석(Hwan Suk Cheong),이혜림(Hyerim Lee),심준용(Joon Yong Sim),임세라(Sera Lim),정윤미(Yunmi Jeong) 한국원예학회 2023 한국원예학회 학술발표요지 Vol.2023 No.10

Southern Indian Ocean Dipole as a trigger for Central Pacific El Niño since the 2000s

Hyun-Su Jo,Yoo-Guen Ham,Jong-Seong Kug,Tim Li,Jeong-Hwan Kim,Ji-Gwang Kim,Hyerim Kim 한국기상학회 2023 한국기상학회 학술대회 논문집 Vol.2023 No.4

블루투스를 활용한 IoT(Internet of Things) 기반의 스마트오피스

조항준(Hangjoon Jo),유준우(Joonwoo Yoo),홍혜림(Hyerim Hong),이영재(Yeongjae Lee) 한국정보기술학회 2021 Proceedings of KIIT Conference Vol.2021 No.6

블루투스를 활용하여 IoT(Internet of Things) 기반의 스마트오피스를 구축했다. 아두이노 센서와 사용자의 스마트폰 간에 블루투스 통신을 이용해 데이터를 주고받으며 사용자의 개입 없이 자동으로 상황을 파악하고 그에 맞는 제어를 하게 된다. 오피스의 온도가 높아지면 온도를 낮추고, 습도가 높으면 습도를 낮추는 등의 과정이 자동으로 이루어진다. 또한, 사용자가 필요로 할 시 직접 안드로이드 앱을 이용하여 제어할 수 있다. 사용자에게 정보를 제공하는 과정에서 기존 텍스트를 사용하여 상황을 알리는 방식과는 다르게 안드로이드 앱을 이용해 제작한 GUI(Graphic User Interface)를 통해 더욱 직관적으로 상황을 사용자에게 전달할 수 있다. 또한, 하나의 캐릭터를 제작하여 사용자에게 친밀감과 재미를 유도할 수 있게 했다. LED와 서보모터의 작동을 확인하기 위해 각각 CDS(Cadmium sulfide) 센서, 충돌 센서를 이용하여 진단 프로그램을 작성하였다. We built a smart office based on IoT (Internet of Things) using Bluetooth. Data is transmitted using Bluetooth communication between the Arduino sensor and the user"s smartphone. It gives and receives, automatically grasps the situation without user intervention, and controls accordingly. When the office temperature rises, the temperature is lowered, and when the humidity is high, the humidity is lowered automatically. The process takes place automatically.In addition, if the user needs it, it can be controlled directly using the Android app. In the process of providing information to the user, unlike the method of notifying the situation using existing text, it is through a GUI (Graphic User Interface) created using an Android app. The situation can be communicated to the user more intuitively. In addition, by creating a single character, users can induce intimacy and fun.In order to check the operation of LED and 서보 motor, a diagnostic program was prepared using CDS(Cardmium sulfide) sensor and collision sensor, respectively.

How Elementary English Teachers Think about Using Literary Texts in Korean EFL Classes

Sol Kim,Hyerim Nam,Kyuhee Jo,Yong seok Cha,Sumi Choi,Dong hwan Lee 한국초등영어교육학회 2017 한국초등영어교육학회회보 Vol.2017 No.-

기만기 적용 고무 O-ring의 온도에 따른 가속수명시험을 통한 수명예측에 관한 연구

조희진(Hee-Jin Jo),김민우(Minwoo Kim),곽혜림(Hyerim Gwak) 한국산학기술학회 2016 한국산학기술학회논문지 Vol.17 No.10

어뢰회피용 기만기는 수중에서 적 어뢰의 공격으로부터 자함을 보호하는 무기체계로 유사 시 우리 군의 피해를 최소화하기 위해 운용 간 고장없이 정상적으로 임무를 수행하여야 한다. 기만기는 운영 특성 상 내부로 해수가 유입되면 정상적인 임무 수행이 불가하기 때문에 운용환경을 고려하여 외부로부터 해수유입 방지를 위한 완벽한 기밀이 요구된다. 일반적으로 기만기의 수밀성능 확보를 위해 고무재질의 오링을 사용하는데 이러한 고무재질의 제품들은 시간의 경과와 주변 환경의 영향을 받아 노화되어 고무 초기 특성이 상실되어진다. 따라서 요구되는 수밀성능을 유지하기 위해 오링에 대한 정비 또는 교체가 필수적이다. 본 논문에서는 기만기에 사용되는 오링의 대표적인 물성 지표인 경도와 신장률 값을 기준으로 오링의 가속수명시험 수행을 통한 시험데이터를 바탕으로 적합한 정비주기를 선정하는 것을 목적으로 한다. 기만기 수밀성능을 보장하기 위해 사용되는 오링의 재질은 NBR(Nitrile Butadiene Rubber)로써, 선행 연구 자료를 참고하여 주요 고장 환경 인자를 온도로 선정하였으며, 고장의 기준은 대상 제품이 가지는 물성 값 중 경도와 신장률이 초기 대비 50%까지 저하되는 시점으로 선정하였다. 또한 시험에 사용되는 시편 준비 및 물성 값 측정방법은 KS M 6518 규격을 참고하여 진행하였다. 시험결과는 컴퓨터 프로그램을 통해 분석하여 기만기에 적용되는 오링의 수명을 예측하였으며, 이를 통해 오링에 대한 정비주기를 산출하였다. A decoy is a weapon system that can protect vessels from an enemy"s torpedo. Thus, the decoy should be able to operate in the field without any failure. Because the decoy can be inoperable once its sealing is broken and water permeates inside the system, the hermetic sealing capability considering the operational environment is mandatory. To be hermetically sealed, a rubber-type O-ring is generally used in a decoy system. The sealed performance of rubber-type products, however, tends to age and deteriorate with time. Therefore, the O-ring needs to be maintained or changed periodically. This paper proposes a method to estimate the proper maintenance period using the hardness and elongation percentage, which represents the performance of the O-ring product and test data from Accelerated Life Test (ALT) of the product. The O-ring used in this paper is a NBR type, and the temperature was chosen to be the main accelerating factor as referenced in many studies. The criteria for the failure of the O-ring was set for the product to be 50% degraded compared to the initial performance. In addition, the Korean standard KS M 6518 was adopted and referenced for the preparation of test samples and the calculation of estimates. The O-ring"s predicted life was simulated by analyzing the test results from a computer program, and the optimized maintenance period for the product was determined.

A trust value-based scheme for efficient contents sharing over mobile P2P networks

Kim, Sejin,Kim, Hyerim,Kim, Sung Jo Springer-Verlag 2015 The Journal of supercomputing Vol.71 No.6

Improved extraction of lipids from Atlantic salmon tissues and quantitative determination of fatty acids using GC-MS

Thi Hoai Thu Mai,Aram Jo,Hyerim Kim,Seoyoon Choi,Jaeseok Choi,Hekap Kim 한국분석과학회 2021 학술대회논문집 Vol.2021 No.11

The aim of this study was to modify and improve the lipid extraction method and optimize derivatization techniques for fatty acids analysis from Salmon tissues. Fresh salmon samples were separated and dried using a freeze-drier, and used as the material to produce lipids. The objective of the research is to evaluate the effect of the different ratio between denaturing solvent and extraction solvent (1:10, 2:10, 3:10 and 5:10), the optimization of extraction solvents (methyl tert-butyl ether and ethyl acetate) for lipid production in salmon tissues and to analyze the amount of fatty acids in the extracted lipids. The distribution of different fatty acids within the lipids was achieved after derivatizing by methanolysis at 60℃ for 5, 10, 20, 30, 60 and 120 min to produce fatty acid methyl esters (FAME). FAMEs from extracted salmon lipids were analyzed by Gas Chromatography - Mass Spectrometry (GC-MS). The results show that the highest yield of produced lipids was with the ratio of 3:10 denaturing solvent to extraction solvent; and the yield of the total lipids obtained by ethyl acetate was higher than MTBE. In twelve salmon tissue samples, the contents of EPA ranged from 0.2 mg/g to 6.5 mg/g; and the contents of DHA ranged from 1.6 mg/g to 37.6 mg/g. The results also demonstrate that salmon tissues contain 12.9 – 37% more polyunsaturated fatty acid (PUFA) in lipid fraction; and the composition of unsaturated fatty acids is more than saturated fatty acids. Statistical analysis indicates that the recovery of fatty acids from tissue samples by the simplified method is significantly higher than that by the traditional method, but there is no difference in relative fatty acid composition between the two methods. This simplified method can significantly save time and materials, and reduce the potentials of sample loss and contamination. In conclusion, our proposed method was effective and fatty acids in the extracted lipids were identified.