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Jeon, Hojeong,Lee, Yongku,Jin, Songwan,Koo, Sangmo,Lee, Chang-Soo,Yoo, Jung Yul Springer US 2009 BIOMEDICAL MICRODEVICES Vol.11 No.5
<P>A microfluidic device to quantify bacterial chemotaxis has been proposed, which generates a linear concentration gradient of chemoattractant in the main channel only by convective and molecular diffusion, and which enables the bacteria to enter the main channel in a single file by hydrodynamic focusing technique. The trajectory of each bacterium in response to the concentration gradient of chemoattractant is photographed by a CCD camera and its velocity is acquired by a simple PTV (Particle Tracking Velocimetry) algorithm. An advantage of this assay is to measure the velocity of a single bacterium and to quantify the degree of chemotaxis by analyzing the frequency of velocities concurrently. Thus, the parameter characterizing the motility of wild-type <I>Escherichia coli</I> strain RP437 in response to various concentration gradients of L-aspartate is obtained in such a manner that the degree of bacterial chemotaxis is quantified on the basis of a newly proposed Migration Index.</P>
초정밀 레이저 나노패터닝 기술을 이용한 세포 거동 제어
전호정(Hojeong Jeon) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Recent progress in developing techniques for micro/nano-fabrication of biomaterials helps recapitulate many extracellular matrix cues, making them progressively more useful for applications in biology and regenerative medicine. This talk presents a study of femtosecond laser assisted nanofabrication applicable for the biomaterials design aiming at achieving deliberate control of the cell behavior. We applied femtosecond laser induced multiphoton laser ablation lithography to fabricate precisely defined two-dimensional chemical and topographical patterned surface in nanometer to micrometer length scale to be used in studies addressing fundamental issues concerning control of cell adhesion, migration and stem cell differentiation.
전호정(Hojeong Jeon),이용구(Yongkoo Lee),진송완(Songwan Jin),구상모(Sangmo Koo),이창수(Chang-Soo Lee),유정열(Jung Yul Yoo) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
Bacterial chemotaxis may have a significant impact on the study of structure and function of bacteria. Quantification of chemotactic motion is necessary to identify chemoeffectors and to determine the bacterial transport parameters used in prediction models of chemotaxis. Although many studies have accumulated the knowledge about chemotaxis for many years, the motion of a single bacterium has not been studied yet. In this study we propose a device microfabricated by soft lithography and consisting of microfluidic channels, which can generate a gradient of chemoeffectors in the main channel so that a single bacterium is injected into this channel by hydrodynamic focusing. This microfluidic assay offers superior performance to measure a single cell or a group of cells and to quantify their motion, and it also builds a delicate gradient of chemoeffectors to raise accuracy of measuring the bacterial motion.
유체역학적 집속 효과를 이용한 단일 박테리아 주화성의 정량적 분석
전호정(Hojeong Jeon),이용구(Yongkoo Lee),진송완(Songwan Jin),구상모(Sangmo Koo),이창수(Chang-Soo Lee),유정열(Jung Yul Yoo) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Bacterial chemotaxis may have a significant impact on the study of structure and function of bacteria. Quantification of chemotactic motion is necessary to identify chemoattractant and to determine the bacterial transport parameters used in prediction models of chemotaxis. Although many studies have accumulated the knowledge about chemotaxis for many years, the motion of a single bacterium has not been studied yet. In this study we propose a device microfabricated by soft lithography and consisting of microfluidic channels, which can generate a gradient of chemoattractant in the main channel so that a single bacterium is injected into this channel by hydrodynamic focusing. Additionally, we measure and analyze the motility of bacteria through the concentration gradient of chemoattractant quantitatively and statistically by using this microfluidic assay.
Jin‑Kyung Jeon,Hyunseon Seo,Jimin Park,Soo Ji Son,Yeong Rim Kim,Eun Shil Kim,Jong Woong Park,Woong‑Gyo Jung,Hojeong Jeon,Yu‑Chan Kim,Hyun‑Kwang Seok,Jae Ho Shin,Myoung‑Ryul Ok 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4
The excessive initial corrosion rate of Mg is a critical limitation in the clinical application of biodegradable Mg implantsbecause the device loses its fi xation strength before the fractured bone heals. This study suggests a new approach to overcomethis hurdle by accelerating tissue regeneration instead of delaying the implant biodegradation. As angiogenesis is anessential process in early bone regeneration, a Mg implant coated with electrospun nanofi bers containing nitric oxide (NO),which physiologically promotes angiogenesis, is designed. The integrated device enables adjustable amounts of NO to bestored on the NO donor-conjugated nanofi ber coating, stably delivered, and released to the fractured bone tissue near theimplanted sites. An in vitro corrosion test reveals no adverse eff ect of the released NO on the corrosion behavior of the Mgimplant. Simultaneously, the optimal concentration level of NO released from the implant signifi cantly enhances tube networkformation of human umbilical vein endothelial cells without any cytotoxicity problem. This indicates that angiogenesis canbe accelerated by combining NO-releasing nanofi bers with a Mg implant. With its proven feasibility, the proposed approachcould be a novel solution for the initial stability problem of biodegradable Mg implants, leading to successful bone fi xation.
Hojeong Lee,Dong Woon Kim,Ji Hyeon Joo,Yongkan Ki,Wontaek Kim,Dahl Park,Jiho Nam,Dong Hyeon Kim,Hosang Jeon Korean Society of Medical Physics 2022 의학물리 Vol.33 No.4
Purpose: Radiotherapy after bladder filling protocol (BFP) is known to enhance treatment quality and reduce side effects in prostate cancer, a common male solid cancer globally. However, due to the need to hold back urine during treatment, patients frequently complain of discomfort, and treatment is frequently suspended when patients urinate during treatment and urine penetrates the treatment device, causing malfunction. Therefore, the effect of minimizing treatment time when partial-arc volumetric modulated arc therapy (VMAT) was used instead of full-arc was assessed in this study. Methods: A total of 70 plans were created in 10 patients using 7 different arc sizes, and the treatment time for each plan was calculated. Results: Reduced arc size by half resulted in a 54.4% decrease in mean treatment duration, with a proportional tendency observed. Furthermore, the effect of VMAT arc size reduction on target dose homogeneity was significantly limited, and the effect on surrounding organs at risk (OAR) was negligible. It should be noted, however, that when the arc size decreases by >40%, the dose increases in the area without OAR around the target. Conclusions: The results of this study demonstrated that partial-arc VMAT for enhancing treatment convenience and efficacy of prostate cancer patients undergoing BFP can achieve a considerable reduction in treatment time while preserving treatment quality, and it is expected to be useful for partial-arc VMAT plan design and implementation in practice.