• Smart Structures and Systems
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• v.8 no.1
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• pp.53-67
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• 2011

Human state in human-machine systems highly affects the overall system performance, and should be detected and monitored. Physiological cues are essential indicators of human state and useful for the purpose of monitoring. The study presented in this paper was focused on developing a bio-inspired sensing system, i.e., Nano-Skin, to non-intrusively measure physiological cues on human-machine contact surfaces to detect human state. The paper is presented in three parts. The first part is to analyze the relationship between human state and physiological cues, and to introduce the conceptual design of Nano-Skin. Generally, heart rate, skin conductance, skin temperature, operating force, blood alcohol concentration, sweat rate, and electromyography are closely related with human state. They can be measured through human-machine contact surfaces using Nano-Skin. The second part is to discuss the technologies for skin temperature measurement. The third part is to introduce the design and manufacture of the Nano-Skin for skin temperature measurement. Experiments were performed to verify the performance of the Nano-Skin in temperature measurement. Overall, the study concludes that Nano-Skin is a promising product for measuring physiological cues on human-machine contact surfaces to detect human state.

• BMB Reports
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• v.56 no.5
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• pp.287-295
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• 2023

The tumor microenvironment (TME) is a complex system composed of many cell types and an extracellular matrix (ECM). During tumorigenesis, cancer cells constantly interact with cellular components, biochemical cues, and the ECM in the TME, all of which make the environment favorable for cancer growth. Emerging evidence has revealed the importance of substrate elasticity and biomechanical forces in tumor progression and metastasis. However, the mechanisms underlying the cell response to mechanical signals-such as extrinsic mechanical forces and forces generated within the TME-are still relatively unknown. Moreover, having a deeper understanding of the mechanisms by which cancer cells sense mechanical forces and transmit signals to the cytoplasm would substantially help develop effective strategies for cancer treatment. This review provides an overview of biomechanical forces in the TME and the intracellular signaling pathways activated by mechanical cues as well as highlights the role of mechanotransductive pathways through mechanosensors that detect the altering biomechanical forces in the TME.

• BMB Reports
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• v.50 no.2
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• pp.71-78
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• 2017

The Hippo signaling pathway plays an essential role in adult-tissue homeostasis and organ-size control. In Drosophila and vertebrates, it consists of a highly conserved kinase cascade, which involves MST and Lats that negatively regulate the activity of the downstream transcription coactivators, YAP and TAZ. By interacting with TEADs and other transcription factors, they mediate both proliferative and antiapoptotic gene expression and thus regulate tissue repair and regeneration. Dysregulation or mutation of the Hippo pathway is linked to tumorigenesis and cancer development. Recent studies have uncovered multiple upstream inputs, including cell density, mechanical stress, G-protein-coupled receptor (GPCR) signaling, and nutrients, that modulate Hippo pathway activity. This review focuses on the role of the Hippo pathway as effector of these biophysical cues and its potential implications in tissue homeostasis and cancer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.6 s.261
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• pp.686-693
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• 2007

To perceive body movement, the nervous system uses multi-sensory cues such as vision, vestibular signals, and somatosensation. Among the multi-sensory modality, the previous researchers reported that the lower limb somatosensation plays an important role on maintaining postural balance. In this study, we examined the contribution of somatosensory cues to linear motion perception by measuring the detection threshold of the direction of linear motion with and without lower limb somatosensory constraints. Six healthy male volunteers participated in randomly ordered 33 single sinusoidal acceleration trials with the stimulus at 0.25Hz with peak magnitude ranged from 0 to 8mG. After each stimulus, subjects reported their perceived direction of motion by button press. Results showed that the reduced lower limb somatosensation significantly increased perception threshold. Without constraints, mean threshold was $0.82{\pm}0.23mG$, while it was $1.23{\pm}0.35mG$ with reduced lower limb somatosensation. The results suggest that without visual cues, perception of the movement direction strongly depends on the lower limb somatosensory information.

• Tissue Engineering and Regenerative Medicine
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• v.15 no.6
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• pp.761-769
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• 2018

BACKGROUND: Bioprinting has recently appeared as a powerful tool for building complex tissue and organ structures. However, the application of bioprinting to regenerative medicine has limitations, due to the restricted choices of bio-ink for cytocompatible cell encapsulation and the integrity of the fabricated structures. METHODS: In this study, we developed hybrid bio-inks based on acrylated hyaluronic acid (HA) for immobilizing bio-active peptides and tyramine-conjugated hyaluronic acids for fast gelation. RESULTS: Conventional acrylated HA-based hydrogels have a gelation time of more than 30 min, whereas hybrid bio-ink has been rapidly gelated within 200 s. Fibroblast cells cultured in this hybrid bio-ink up to 7 days showed >90% viability. As a guidance cue for stem cell differentiation, we immobilized four different bio-active peptides: BMP-7-derived peptides (BMP-7D) and osteopontin for osteogenesis, and substance-P (SP) and Ac-SDKP (SDKP) for angiogenesis. Mesenchymal stem cells cultured in these hybrid bio-inks showed the highest angiogenic and osteogenic activity cultured in bio-ink immobilized with a SP or BMP-7D peptide. This bio-ink was loaded in a three-dimensional (3D) bioprinting device showing reproducible printing features. CONCLUSION: We have developed bio-inks that combine biochemical and mechanical cues. Biochemical cues were able to regulate differentiation of cells, and mechanical cues enabled printing structuring. This multi-functional bio-ink can be used for complex tissue engineering and regenerative medicine.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.798-802
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• 2003

The robustness and reliability of vision algorithms is the key issue in robotic research and industrial applications. In this paper, the robust real time visual tracking in complex scene is considered. A common approach to increase robustness of a tracking system is to use different models (CAD model etc.) known a priori. Also fusion of multiple features facilitates robust detection and tracking of objects in scenes of realistic complexity. Because voting is a very simple or no model is needed for fusion, voting-based fusion of cues is applied. The approach for this algorithm is tested in a 3D Cartesian robot which tracks a toy vehicle moving along 3D rail, and the Kalman filter is used to estimate the motion parameters, namely the system state vector of moving object with unknown dynamics. Experimental results show that fusion of cues and motion estimation in a tracking system has a robust performance.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.38-38
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• 2013

The mechanical cues that adherent cells derive from the extracellular matrix (ECM) can effect dramatic changes in cell migration, proliferation, and differentiation. Using a thin film of Type I collagen fibrils comprised of 100 nm to 200 nm collagen fibrils overlaying a bed of smaller fibrils, changes in cellular response to systematically controlled changes in mechanical properties of collagen was investigated. Further, an experimental and modeling approaches to calculate the elastic modulus of individual collagen fibrils, and thereby the effective stiffness of the entire collagen thin film matrix, from atomic force microscopy force spectroscopy data was performed. These results demonstrate an approach to analysis of fundamental properties of thin, heterogeneous, organic films, and add further insights into the mechanical properties of collagen fibrils that are of relevance to cell response to the ECM.

• Journal of the Korean Society of Visualization
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• v.19 no.1
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• pp.74-80
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• 2021

Cells regulate their shapes and motility by sensing the cues from the internal and external microenvironment. Under different circumstances, microglia, the brain resident immune cells, undergo dynamic phenotypic changes, one of which is a remarkable periodic oscillatory migration in vitro. However, very little is known about the kinematic and dynamic perspectives of this oscillatory behavior. In this study, we tracked the changes in cell morphology and nuclear displacement, and visualized the forces using traction force microscopy (TFM). By correlation analyses, we confirmed that the lamellipodia formation preceded the nuclear translocation. Moreover, traction, developed following lamellipodia formation, was found to be localized and fluctuated at two ends of the oscillating cells. Taken together, our results imply that oscillatory microglial cells feature a viscoelastic migration, which will contribute to the field of cell mechanics.

• BMB Reports
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• v.51 no.3
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• pp.151-156
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• 2018

The Hippo signaling pathway controls nuclear accumulation and stability of the transcriptional coregulator YAP and its paralog TAZ. The activity of Hippo-YAP signaling is influenced not only by biochemical signals, but also by cell shape and mechanical tension transmitted through cell-cell junctions and cell-matrix adhesions. Data accumulated thus far indicates that the actin cytoskeleton is a key mediator of the regulation of Hippo-YAP signaling by means of a variety of biochemical and mechanical cues. In this review, we have outlined the role of actin dynamics and actin-associated proteins in the regulation of Hippo-YAP signaling. In addition, we discuss actin-mediated regulation of YAP/TAZ activity independent of the core Hippo kinases MST and LATS. Although our understanding of the link between Hippo-YAP signaling and the actin cytoskeleton is progressing rapidly, many open questions remain.

• Journal of the Korean Society of Visualization
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• v.20 no.2
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• pp.70-77
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• 2022

Skeletal muscle tissues feature cellular heterogeneity, including differentiated myofibers, myoblasts, and satellite cells. Thanks to the presence of undifferentiated myoblasts and satellite cells, skeletal muscle tissues can self-regenerate after injury. In skeletal muscle regeneration, the collective motions among these cell types must play a significant role, but little is known about the dynamic collective behavior during the regeneration. In this study, we constructed in vitro platform to visualize the migration behavior of skeletal muscle cells in specific conditions that mimic the biochemical environment of injured skeletal muscles. We then visualized the spatiotemporal distribution of stresses arising from the differential collectiveness in the cellular clusters under different conditions. From these analyses, we identified that the heterogeneous population of muscle cells exhibited distinct collective migration patterns in the injury-mimicking condition, suggesting selective activation of a specific cell type by the biochemical cues from the injured skeletal muscles.