Changmo Hwang | University of Ulsan, Korea (south) (original) (raw)

Papers by Changmo Hwang

Tissue Engineering and Regenerative Medicine, 2016

2009 IEEE 35th Annual Northeast Bioengineering Conference, 2009

Investigative Ophthalmology & Visual Science, 2015

La presente invention concerne une pompe a sang rotative qui s'implante dans le corps du pati... more La presente invention concerne une pompe a sang rotative qui s'implante dans le corps du patient pour faciliter le refoulement du sang dans l'aorte depuis le coeur. Cette pompe comporte un boitier cylindrique, un premier et un second stator montes a demeure dans le boitier, une turbine cylindrique inseree autour d'une partie etendue du premier stator, un moteur faisant tourner la turbine autour de la partie etendue du premier stator, des paliers magnetiques pour conserver une position radiale et axiale predeterminee de la turbine en suspension magnetique, et un detecteur d'intervalle pour mesurer une distance entre la turbine et le second stator. La turbine est suspendue et mise en rotation dans le boitier par effet magnetique. La rotation de la turbine permet a la pompe a sang rotative de refouler le sang depuis une entree vers une sortie du boitier. La turbine est capable de produire un flux de sang par sa mise en rotation en suspension magnetique sans risque de co...

The present invention comprises a first electrode tip formed on the distal end of the first elect... more The present invention comprises a first electrode tip formed on the distal end of the first electrode 110 and the second electrode, and a 120, the first electrode 110 which is guided by the introducer sheath 60 is inserted into the body tissue ( 112) and the second electrode tip (122 formed at the distal end of the second electrode 120) is directed to a radiation frequency electrode body for the selective removal of the body tissue coupled with a predetermined gap. Specifically, the electrode and the end of the first electrode 110 and second electrode 120 of the body is coupled a coil spring, the coil spring is true end is bent in a free state shape is then the first electrode and the second It is pulling the at least one deformation of the electrodes. The electrode body in the desired tissue site by using a sieve, by easily controlling the direction and the position of the electrode tip to the radiation frequency can be easily procedure.

Tissue engineering. Part A, Jan 23, 2015

The aggregation of multiple cells, such as mesenchymal condensation, is an important biological p... more The aggregation of multiple cells, such as mesenchymal condensation, is an important biological process in skeletal muscle development, osteogenesis, and adipogenesis. Due to limited in vivo study model systems, a simple and effective in vitro three-dimensional (3D) aggregation system is required to study the mechanisms of multicellular aggregation and its applications. We first generated controlled mesenchymal stem cell (MSC) aggregates using a bio-printing technique to monitor their aggregation and sprouting. We induced the angiogenic potential of the MSCs through chemical inhibition of the Rho/Rho-associated protein kinase (ROCK) pathway, which led to hairy sprouting in the aggregates. The angiogenic potential of this 3D construct was then tested by subcutaneously implanting the Matrigel with 3D MSC aggregates in a rat. Treatment of 3D MSCs with the ROCK inhibitor, Y27632, increased their angiogenic activity in vivo. The gene expressions and histological staining indicated that a...

2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2009

Cell migration and proliferation are major process in wound healing, cancer metastasis and organo... more Cell migration and proliferation are major process in wound healing, cancer metastasis and organogenesis during development. Many cells are related to recovery process of wound. Especially, fibroblasts act an important role in wound healing. Various cytokines such as platelet derived growth factor (PDGF) can induce fibroblast migration and widely studied to investigate the cell response under controlled cytokine microenvironments during wound healing. In real tissue healing process, cell microenvironments change with tissue types and anatomical characteristics of organs. With microfluidic system, we tried to mimic the natural microenvironment of wound healing, with gradient of PDGF, a fibroblast migration inducing cytokine, and patterned substrate with different orientation to PDGF gradient. Fibroblasts cultured in PDGF gradient micro fluidic chip showed cell migration under various micro environmental gradient conditions. Cells were cultured under PDGF gradient condition and different substrate pattern. Mouse fibroblast L929 cells were cultured in the microfluidic gradient. The results showed that most cells migrated along the substrate topological patterns under high concentration of PDGF. We developed long range sustaining micro fluidic channel and could analyze cell migration along the gradient of PDGF. Also, the cell migration on patterned extracellular environment shows that cells migrate along the extracellular 3D pattern rather than directly along the cytokine gradient when the pattern height is less than 1 microm. In this study, we could demonstrate that the extracellular pattern is more dominant to cell migration in combination with cytokine gradient in the wounded tissue when the environmental cues are 20 microm.

Biotechnology and Bioengineering, 2010

In this article, we describe an approach to generate microporous cell-laden hydrogels for fabrica... more In this article, we describe an approach to generate microporous cell-laden hydrogels for fabricating biomimetic tissue engineered constructs. Micropores at different length scales were fabricated in cell-laden hydrogels by micromolding fluidic channels and leaching sucrose crystals. Microengineered channels were created within cell-laden hydrogel precursors containing agarose solution mixed with sucrose crystals. The rapid cooling of the agarose solution was used to gel the solution and form micropores in place of the sucrose crystals. The sucrose leaching process generated homogeneously distributed micropores within the gels, while enabling the direct immobilization of cells within the gels. We also characterized the physical, mechanical, and biological properties (i.e., microporosity, diffusivity, and cell viability) of cell-laden agarose gels as a function of engineered porosity. The microporosity was controlled from 0% to 40% and the diffusivity of molecules in the porous agarose gels increased as compared to controls. Furthermore, the viability of human hepatic carcinoma cells that were cultured in microporous agarose gels corresponded to the diffusion profile generated away from the microchannels. Based on their enhanced diffusive properties, microporous cell-laden hydrogels containing a microengineered fluidic channel can be a useful tool for generating tissue structures for regenerative medicine and drug discovery applications.

ASAIO Journal, 2006

We developed a real-time remote managing system for an artificial heart using CDMA-based PDA phon... more We developed a real-time remote managing system for an artificial heart using CDMA-based PDA phone. It can both telemonitor and telecontrol the operating status of an artificial heart. The system consists of an artificial heart controller that contains cellular phone module, a PDA phone, and a gateway server computer that connects an heart controller and a PDA phone via TCP/IP network. Using this managing system, a medical staff can connect to the artificial heart controller remotely anytime, anywhere, see the operating status of an artificial heart, and adjust control parameters of the heart controller if needed. For security and reliability, several techniques are involved that checks communication error and user identification. Developed system showed satisfactory performance at in vitro and animal experiments. Using this mobile-based remote managing technique, more efficient outpatient treatment are possible. And also, the technique used for artificial heart remote managing can be applied to various medical fields.

ASAIO Journal, 2005

LAR ASSIST DEVICE Changmo Hwang, Gi Seog Jeong, Min Woo Jung, Jung Soo Kang, Jung Joo Lee, Yong D... more LAR ASSIST DEVICE Changmo Hwang, Gi Seog Jeong, Min Woo Jung, Jung Soo Kang, Jung Joo Lee, Yong Doo Park, Kyu Baek Lee, Kyung Sun. Korea Artificial Organ Center, Korea University, Seoul, Korea; Brain Korea 21 Program for Biomedical Science, Korea University College of Medicine, Seoul, Korea; Department of Biomedical Engineering, Korea University College of Medicine, Seoul, Korea; Department of Thoracic and Cardiovascular Surgery, Korea University College of Medicine, Seoul, Korea. The conventional pneumatic drivers for ventricular assist device(VAD) have been relatively large in size and heavy in weight. Recently, portable size drivers are developed and applied in clinical area to give the patients extended scope of activity and convenience of daily life. Additionally, they contributed out of hospital home discharge of pneumatic VAD patients in the clinical aspect. There is still possibility of reducing the size and weight of the pneumatic driver for wearable size. In this paper, simple driving mechanism is suggested for electropneumatic biventricular assist device actuator with smaller size and reduced weight. Our electropneumatic actuator is composed of brushless DC motor, ball screw, two push plates and bellows as major part. The push plates modulate the volume of the bellows. This bellows volume change generates the pressure of the pneumatic circuit for blood pumping. The bellows is manufactured by dipping process with durable polyurethane. The bellows mechanism enabled smaller driver size of 20x30x8cm and reduced weight of 4.0kg including the actuator, controller and battery. To restore the gas leakage, gas compensating system is included, and the short range wireless monitoring is possible with bluetooth module. This wireless monitor/controlling function will improve the mobility of the patients. From the in vitro experiment result, this driver can support 6.5L/min at 100 bpm. And the in vivo animal study showed good performance as biventricular assist device. NUMERICAL STUDY OF THE UNSTEADY BLOOD FLOW IN THE BLOOD SAC OF THE PNEUMATIC VENTRICULAR ASSIST DEVICE GS Jeong, CM Hwang, K Sun. Brain Korea 21 Program for Biomedical Science, Korea University College of Medicine, Seoul, Republic of Korea; Korea Artificial Organ Center, Korea University, Seoul, Republic of Korea; Department of Biomedical Engineering, Korea University College of Medicine, Seoul, Republic of Korea; Department of Thoracic and Cardiovascular Surgery, College of Medicine, Korea University, Seoul, Republic of Korea. Many researchers have studied the hemocompatibility of blood contacting surface in the pneumatic VAD(Ventricular Assist Device), which is widely used in cardiac support. The blood sac in the pneumatic VAD is important in the point of hemocompatibility, because it contacts with blood directly. Among many factors that affect the hemocompatibility, the characteristic of blood flow is important also in the point of thrombosis formation and hemolysis. The recirculation flow and the excessive shear stress imposed to the blood cells lead to thrombosis formation and hemolysis. In this study, the three dimensional numerical analysis about the hemodynamics in the blood sac was performed. Commercial code ADINA based on finite element method is employed to compute blood flow in the blood sac. To analyze the blood flow, FSI(Fluid-Structure Interaction) method is included. The results showed the higher shear stress region at the inlet and outlet region. The recirculation flow was observed in the center of blood sac during systolic period. This numerical study suggests important information in designing the blood sac of pneumatic VAD in the point of hemodynamics.

Advanced Functional Materials, 2010

Tissue Engineering and Regenerative Medicine, 2021

BACKGROUND: In vitro generation of three-dimensional vessel network is crucial to investigate and... more BACKGROUND: In vitro generation of three-dimensional vessel network is crucial to investigate and possibly improve vascularization after implantation in vivo. This work has the purpose of engineering complex tissue regeneration of a vascular network including multiple cell-type, an extracellular matrix, and perfusability for clinical application. METHODS: The two electrospun membranes bonded with the vascular network shape are cultured with endothelial cells and medium flow through the engineered vascular network. The flexible membranes are bonded by amine-epoxy reaction and examined the perfusability with fluorescent beads. Also, the perfusion culture for 7 days of the endothelial cells is compared with static culture on the engineered vascular network membrane. RESULTS: The engineered membranes are showed perfusability through the vascular network, and the perfused network resulted in more cell proliferation and variation of the shear stress-related genes expression compared to th...

Journal of neurointerventional surgery, Jan 27, 2014

Simultaneous use of balloon catheters with embolic materials can cause unwanted rupture of the ba... more Simultaneous use of balloon catheters with embolic materials can cause unwanted rupture of the balloon occlusion catheters, which might cause a serious problem. Therefore, knowledge of the compatibility of occlusion balloon catheters with liquid embolic materials is important in various interventional procedures. To determine the compatibility of occlusion balloon catheters with commonly used embolic materials in vitro. We used three types of occlusion balloon catheters (Scepter C, Microvention, Tustin, California, USA; Hyperform, Covidien, Irvine, California, USA; and Ascent, Codman Neurovascular, Raynham, Massachusetts, USA) to test their tolerances to Lipiodol, n-butyl cyanoacrylate (NBCA; Histoacryl; B Braun, Melsungen, Germany), and dimethyl sulfoxide (DMSO) with Onyx. The balloon was inflated just as it is in an endovascular procedure, then put on a Petri dish to observe its morphological change after one drop of liquid embolic material was added using a 1 mL syringe. The pres...

Cells

This study aims to obtain sufficient corneal endothelial cells for regenerative application. We e... more This study aims to obtain sufficient corneal endothelial cells for regenerative application. We examined the combinatory effects of Rho-associated kinase (ROCK) inhibitor Y-27632 and mesenchymal stem cell-derived conditioned medium (MSC-CM) on the proliferation and senescence of rabbit corneal endothelial cells (rCECs). rCECs were cultured in a control medium, a control medium mixed with either Y-27632 or MSC-CM, and a combinatory medium containing Y-27632 and MSC-CM. Cells were analyzed for morphology, cell size, nuclei/cytoplasmic ratio, proliferation capacity and gene expression. rCECs cultured in a combinatory culture medium showed a higher passage number, cell proliferation, and low senescence. rCECs on collagen type I film showed high expression of tight junction. The cell proliferation marker Ki-67 was positively stained either in Y-27632 or MSC-CM-containing media. Genes related to cell proliferation resulted in negligible changes in MKI67, CIP2A, and PCNA in the combinatory...

Cells, 2021

ArXiv, 2021

With rise of interventional cardiology, Catheter Ablation Therapy (CAT) has established itself as... more With rise of interventional cardiology, Catheter Ablation Therapy (CAT) has established itself as a firstline solution to treat cardiac arrhythmia. Although CAT is a promising technique, cardiologist lacks vision inside the body during the procedure, which may cause serious clinical syndromes. To support accurate clinical procedure, Contact Force Sensing (CFS) system is developed to find a position of the catheter tip through the measure of contact force between catheter and heart tissue. However, the practical usability of commercialized CFS systems is not fully understood due to inaccuracy in the measurement. To support the development of more accurate system, we develop a full pipeline of CFS system with newly collected benchmark dataset through a contact force sensing catheter in simplest hardware form. Our dataset was roughly collected with human noise to increase data diversity. Through the analysis of the dataset, we identify a problem defined as Shift of Reference (SoR), whi...

Investigative Ophthalmology & Visual Science, 2017

BACKGROUND To effectively use pancreatic cancer patient-derived xenograft (PDX) models in transla... more BACKGROUND To effectively use pancreatic cancer patient-derived xenograft (PDX) models in translational research, successful PDX engraftment of surgical specimens in immune-deficient mice is needed. MATERIALS AND METHODS A total of 102 patients underwent pancreatic cancer resection using various procedures. Tumor tissue from all patents was implanted subcutaneously into mice. Tumor engraftment and growth in mice were determined. Engraftment was tested for correlation with operation type, time, tumor size, and oncogene expression using immunohistoculture. RESULTS Multivariate analysis showed that a tumor size of more than 3.5 cm in the patient was a significant factor related to successful PDX engraftment. In contrast, there was no correlation of engraftment with surgical procedure, time needed to remove the specimen, tumor differentiation, lymph node metastasis, and protein expression of p53, Receptor tyrosine-protein kinase erbB-2 (CERBB2), or deleted in pancreatic carcinoma locus ...