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RISS 인기검색어
- 검색키워드
- 저자 : Kim Joonhui (검색결과 6 건)
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Kim Seong-Oh,Kim Joonhui,Okajima Takaharu,Cho Nam-Joon 나노기술연구협의회 2017 Nano Convergence Vol.4 No.5
Background Cell fixation is an essential step to preserve cell samples for a wide range of biological assays involving histochemical and cytochemical analysis. Paraformaldehyde (PFA) has been widely used as a cross-linking fixation agent. It has been empirically recognized in a gold standard protocol that the PFA concentration for cell fixation, C PFA, is 4%. However, it is still not quantitatively clear how the conventional protocol of C PFA is optimized. Methods Here, we investigated the mechanical properties of cell fixation as a function of C PFA by using atomic force microscopy and scanning ion conductance microscopy. The goal of this study is to investigate the effect of C PFA (0–10 wt%) on the morphological and mechanical properties of live and fixed mouse fibroblast cells. Results We found that both Young’s modulus, E, and the fluctuation amplitude of apical cell membrane, a m, were almost constant in a lower C PFA (<10−4%). Interestingly, in an intermediate C PFA between 10−1 and 4%, E dramatically increased whereas a m abruptly decreased, indicating that entire cells begin to fix at C PFA = ca. 10−1%. Moreover, these quantities were unchanged in a higher C PFA (>4%), indicating that the cell fixation is stabilized at C PFA = ca. 4%, which is consistent with the empirical concentration of cell fixation optimized in biological protocols. Conclusions Taken together, these findings offer a deeper understanding of how varying PFA concentrations influence the mechanical properties of cells and suggest new avenues for establishing refined cell fixation protocols. Background Cell fixation is an essential step to preserve cell samples for a wide range of biological assays involving histochemical and cytochemical analysis. Paraformaldehyde (PFA) has been widely used as a cross-linking fixation agent. It has been empirically recognized in a gold standard protocol that the PFA concentration for cell fixation, C PFA, is 4%. However, it is still not quantitatively clear how the conventional protocol of C PFA is optimized. Methods Here, we investigated the mechanical properties of cell fixation as a function of C PFA by using atomic force microscopy and scanning ion conductance microscopy. The goal of this study is to investigate the effect of C PFA (0–10 wt%) on the morphological and mechanical properties of live and fixed mouse fibroblast cells. Results We found that both Young’s modulus, E, and the fluctuation amplitude of apical cell membrane, a m, were almost constant in a lower C PFA (<10−4%). Interestingly, in an intermediate C PFA between 10−1 and 4%, E dramatically increased whereas a m abruptly decreased, indicating that entire cells begin to fix at C PFA = ca. 10−1%. Moreover, these quantities were unchanged in a higher C PFA (>4%), indicating that the cell fixation is stabilized at C PFA = ca. 4%, which is consistent with the empirical concentration of cell fixation optimized in biological protocols. Conclusions Taken together, these findings offer a deeper understanding of how varying PFA concentrations influence the mechanical properties of cells and suggest new avenues for establishing refined cell fixation protocols.
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Kim, Joonhui,Choi, MyungHoon,Jung, Goo-Eun,Ferhan, Abdul Rahim,Cho, Nam-Joon,Cho, Sang-Joon Institute of Pure and Applied Physics 2016 Japanese Journal of Applied Physics Vol. No.
<P>The range of scanning probe microscopy (SPM) applications for atomic force microscopy (AFM) is expanding in the biological sciences field, reflecting an increasing demand for tools that can improve our fundamental understanding of the physics behind biological systems. However, the complexity associated with applying SPM techniques in biomedical research hampers the full exploitation of its capabilities. Recently, the development of scanning ion conductance microscopy (SICM) has overcome these limitations and enabled contact-free, high resolution imaging of live biological specimens. In this work, we demonstrate the limitation of AFM for imaging biological samples in liquid due to artifacts arising from AFM tip-sample interaction, and how SICM imaging is able to overcome those limitations with contact-free scanning. We also demonstrate that SICM measurements, when compared to AFM, show better fit to the actual dimensions of the biological samples. Our results highlight the superiority of SICM imaging, enabling it to be widely adopted as a general and versatile research tool for biological studies in the nanoscale. (C) 2016 The Japan Society of Applied Physics</P>
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Cha, Jaemin,Kim, Joonhui,Ryu, Seongwoo,Hong, Soon H. Elsevier 2019 Composites. Part B, Engineering Vol.162 No.-
<P><B>Abstract</B></P> <P>Low-dimension carbon nanomaterials, such as carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs), are effective mechanical reinforcements in polymer composites. Epoxy matrix composites were fabricated by functionalizing CNT and GNP nanofillers using melamine and nondestructive ball milling. This noncovalent functionalization prevents agglomeration of nanofiller and produces direct CN bonds with the epoxy matrix. Compared to pristine CNTs and GNPs/epoxy nanocomposites, melamine-functionalized CNT (M-CNT)/epoxy and melamine-functionalized GNP (M-GNP)/epoxy nanocomposites exhibited considerably higher tensile strengths and fracture toughness (single edge notch bending, SENB). At 2 wt%, both M-CNT/epoxy and M-GNP/epoxy nanocomposites exhibited enhanced Young's modulus values (M-CNT: 64% and M-GNP: 71%) and ultimate tensile strengths (M- CNT: 22% and M-GNP: 23%). Fracture toughness increased by 95% with the 2 wt% M-CNT/epoxy and by 124% with the 2 wt% M-GNP/epoxy nanocomposite. The reinforcing effects of the two-dimensional M-GNPs were greater than those of the one-dimensional M-CNTs due to differences in pull-out mechanisms and bridging effects. Crack propagation in the nanocomposites, as it relates to fracture toughness, was also investigated.</P>
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원자현미경을 이용한 나노구조체의 각도측정 방법 및 조건
조상준(Cho Sang-Joon),안병운(Ahn Byung-Woon),김준휘(Kim Joonhui),정상한(Chung Sang Han) 표준인증안전학회 2012 표준인증안전학회지 Vol.2 No.1
Invention of the atomic force microscopy (AFM) has provided a powerful measurement capability for sub-nano scale science and technology. Since invention, AFM has been significantly improved, and numerous innovative mechanisms and measuring modes have been developed. As the progress of miniaturization in patterns and photoresist structures in semiconductor, microelectronics, and glass industry, along with the fast advance of the extremely versatile nanotechnology applications, in a great number of industrial processes calls for reliable and comparable quantitative dimensional measurements in the micro- and submicrometer range. To make matters worse, there has been an increasing demand for measuring characteristics of sidewalls like line edge and line width roughness, wave pattern of sidewalls and angles of overhang features. Realizing that currently available CD-AFM or CD-SEM techniques do not satisfy this demand, new measurement standards are required for angles of micro- and nano-structures. In spite of the many capabilities of AFM, quite a few conditions have to be considered to measure critical dimensions (CD) quantitatively with repeatability and reproducibility. Piezo hysteresis, drift, tip shape and consistency, scanner orthogonality and other things are included in the conditions. The requirements and process to measure critical angle of nano- and micro-structure using AFM will be described in this paper.
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