Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session F5: Single Cells and Bacteria IBio Fluids: Internal
|
Hide Abstracts |
Chair: David Bark Jr., Colorado State University Room: 405 |
Monday, November 20, 2017 8:00AM - 8:13AM |
F5.00001: Probing eukaryotic cell mechanics via mesoscopic simulations Igor V. Pivkin, Kirill Lykov, Yasaman Nematbakhsh, Menglin Shang, Chwee Teck Lim We developed a new mesoscopic particle based eukaryotic cell model which takes into account cell membrane, cytoskeleton and nucleus. The breast epithelial cells were used in our studies. To estimate the viscoelastic properties of cells and to calibrate the computational model, we performed micropipette aspiration experiments. The model was then validated using data from microfluidic experiments. Using the validated model, we probed contributions of sub-cellular components to whole cell mechanics in micropipette aspiration and microfluidics experiments. We believe that the new model will allow to study in silico numerous problems in the context of cell biomechanics in flows in complex domains, such as capillary networks and microfluidic devices. [Preview Abstract] |
Monday, November 20, 2017 8:13AM - 8:26AM |
F5.00002: High-Efficiency Multiscale Modeling of Cell Deformations in Confined Microenvironments in Microcirculation and Microfluidics Huijie Lu, Zhangli Peng We developed a high-efficiency multiscale modeling method to predict the stress and deformation of cells during the interactions with their microenvironments in microcirculation and microfluidics, including red blood cells (RBCs) and circulating tumor cells (CTCs). There are more than 1 billion people in the world suffering from RBC diseases. The mechanical properties of RBCs are changed in these diseases due to molecular structure alternations, which is not only important for understanding the disease pathology but also provides an opportunity for diagnostics. On the other hand, the mechanical properties of cancer cells are also altered compared to healthy cells. This can lead to acquired ability to cross the narrow capillary networks and endothelial gaps, which is crucial for metastasis, the leading cause of cancer mortality. Therefore, it is important to predict the deformation and stress of RBCs and CTCs in microcirculations. We develop a high-efficiency multiscale model of cell-fluid interaction. We pass the information from our molecular scale models to the cell scale to study the effect of molecular mutations. Using our high-efficiency boundary element methods of fluids, we will be able to run 3D simulations using a single CPU within several hours, which will enable us to run extensive parametric studies and optimization. [Preview Abstract] |
Monday, November 20, 2017 8:26AM - 8:39AM |
F5.00003: Jellyfish stinging is driven by the moving front of the nematocyst's tubule Uri Shavit, Sinwook Park, Gadi Piriatinskiy, Gilad Yossifon, Tamar Lotan Nematocysts are ultra-fast stinging organelles that are utilized by the Cnidaria phylum for prey capture, defense and locomotion. They consist of a capsule and a tubule and exert high pressure and acceleration to penetrate the target organism. Previous studies report that the ejection and elongation of the tubule are driven by a buildup of osmotic potential in the capsule. We question this explanation using a microfluidic system that controls the osmotic potential by directing the tubule through oil, where no osmotic potential can develop, while keeping the capsule in water. It was found that the time needed for elongation through oil is orders of magnitude larger than through water. Our mathematical model shows that the p$\gamma $Glu concentration in the tubule is higher than in the capsule and the internal pressure that develops there serves as the elongation driving force. These findings imply that modifications of the environment along the tubule route have the potential to slow down the process and reduce its impact. This may shed light on prey defense strategies, human protection against jellyfish stinging, the use of nematocysts for drug delivery and exploration of osmotic based methods for nanotubes production and elongation. [Preview Abstract] |
Monday, November 20, 2017 8:39AM - 8:52AM |
F5.00004: A mathematical model of breast cancer cell motion through a microfluidic device. Jared Barber Deaths due to breast cancer are usually caused by metastases at other locations (e.g. bone), not by the primary tumor. Much research has targeted understanding how to lower the metastatic potential of individual breast cancer cells with the end goal being the mitigation of the effects of breast cancer on the 3.5 million people in the US affected by the disease. Experiments show that metastatic potential correlates well with the physical properties of a cell and its surrounding environment. Biology also suggests that mechanotransduction of cellular pathways (e.g. apoptosis, division) can affect metastatic potential. Because of these insights, we are developing a mechanical model of breast cancer cell translocation in microvessels. Our first model is a two-dimensional model with interconnected viscoelastic elements submersed in a surrounding Stokes flow. This model has been used to consider breast cancer cell translocation through a microfluidic device that was designed as a diagnostic tool for assessing the metastatic potential of breast cells. We will present this current model and share results. We believe that further development of this model will allow consideration of metastatic potential in both in vitro and in vivo settings. [Preview Abstract] |
Monday, November 20, 2017 8:52AM - 9:05AM |
F5.00005: Multiscale modelling of Flow-Induced Blood Cell Damage Yaling Liu, Salman Sohrabi We study red blood cell (RBC) damage and hemolysis at cellular level. Under high shear rates, pores form on RBC membranes through which hemoglobin (Hb) leaks out and increases free Hb content of plasma leading to hemolysis. By coupling lattice Boltzmann and spring connected network models through immersed boundary method, we estimate hemolysis of a single RBC under various shear rates. The developed cellular damage model can be used as a predictive tool for hydrodynamic and hematologic design optimization of blood-wetting medical devices. [Preview Abstract] |
Monday, November 20, 2017 9:05AM - 9:18AM |
F5.00006: Transport effect of \textit{Vorticella}'s stalk contraction cycle is more effective for motile food particles Sangjin Ryu, Jiazhong Zhou, David Admiraal The coiling stalk of \textit{Vorticella} contracts in a few milliseconds and then relaxes over a few seconds. During this cycle, the cell body (zooid) of this sessile protozoan is translated toward and then away from the no-slip substrate to which \textit{Vorticella} is attached. As a result, the surrounding water flows with a maximum Reynolds number of \textasciitilde 1 and \textless \textless 1 during stalk contraction and relaxation, respectively. To elucidate how \textit{Vorticella} uses its stalk contraction-relaxation cycle, we investigated the resultant water flow using a CFD model for \textit{Vorticella}. The simulated flow shows that one cycle can displace virtual particles around the \textit{Vorticella }up to \textasciitilde 190 $\mu $m with a maximum net vertical displacement of 3--4 $\mu $m. This transport effect seems to be caused by asymmetry in the flow field between the contraction and relaxation phases, and it appears to be more effective on motile food particles than non-motile ones. Therefore, our \textit{Vorticella} model enabled investigating the hypothesis that \textit{Vorticella}'s stalk contraction can enhance food transport near the substrate. [Preview Abstract] |
Monday, November 20, 2017 9:18AM - 9:31AM |
F5.00007: Rheology of platelets at late stages of activation and their role in thrombo-inflammatory responses David Bark Jr., Katrina Ashworth, Yuping Yuan, Jorge DiPaola, Shaun Jackson Thrombo-inflammatory responses can lead to death and can be found in reperfusion injury, deep vein thrombosis, and organ transplantation. Key characteristics include microvascular thrombi and intravascular leukocyte aggregation. We demonstrate that the heterotypic interaction of platelets and leukocytes is highly dependent on flow and platelet rheology. For this work, we visualize platelets at various stages of activation and their interactions with leukocytes in microfluidic flow chambers at various wall shear rates. We further investigate the binding mechanisms supporting the interactions by using blood from a Nbeal2$^{KO}$ mouse. Through this work, we find that as platelets reach late stages of activation, they lose their structural integrity, resulting a membrane shell. Through flow experiments, we find that the shell increasingly deforms as the wall shear rate increases to 28,800 s$^{-1}$, with little link between wall shear rate and membrane rupture. However, when quantifying membrane tension, rupture occurs consistently at 20 pN/$\mu$m. By further exposing P-selectin on their surface, platelets can support leukocyte binding at a shear rate of 200 s$^{-1}$ or less, supporting membrane tension that exceeds the rupture limit, due to drag forces associated with leukocyte size. [Preview Abstract] |
Monday, November 20, 2017 9:31AM - 9:44AM |
F5.00008: Multiscale Modeling of Primary Cilium Deformations Under Local Forces and Shear Flows Zhangli Peng, Zhe Feng, Andrew Resnick, Yuan-Nan Young We study the detailed deformations of a primary cilium under local forces and shear flows by developing a multiscale model based on the state-of-the-art understanding of its molecular structure. Most eukaryotic cells are ciliated with primary cilia. Primary cilia play important roles in chemosensation, thermosensation, and mechanosensation, but the detailed mechanism for mechanosensation is not well understood. We apply the dissipative particle dynamics (DPD) to model an entire well with a primary cilium and consider its different components, including the basal body, microtubule doublets, actin cortex, and lipid bilayer. We calibrate the mechanical properties of individual components and their interactions from experimental measurements and molecular dynamics simulations. We validate the simulations by comparing the deformation profile of the cilium and the rotation of the basal body with optical trapping experiments. After validations, we investigate the deformation of the primary cilium under shear flows. Furthermore, we calculate the membrane tensions and cytoskeleton stresses, and use them to predict the activation of mechanosensitive channels. [Preview Abstract] |
Monday, November 20, 2017 9:44AM - 9:57AM |
F5.00009: Exploration of Structural Changes in Lactose Permease on Sugar Binding and Proton Transport through Atomistic Simulations Jin Liu, Yead Jewel, Prashanta Dutta \textit{Escherichia coli} lactose permease (LacY) actively transports lactose and other galactosides across cell membranes through lactose/H$^{\mathrm{+}}$ symport process. Lactose/H$^{\mathrm{+}}$ symport is a highly complex process that involves large-scale protein conformational changes. The complete picture of lactose/H$^{\mathrm{+}}$ symport is largely unclear. In this work, we develop the force field for sugar molecules compatible with PACE, a hybrid and coarse-grained force field that couples the united-atom protein models with the coarse-grained MARTINI water/lipid. After validation, we implement the new force field to investigate the binding of a $\beta $ -D-galactopyranosyl-1-thio-$\beta $-D-galactopyranoside (TDG) molecule to a wild-type LacY. Transitions from inward-facing to outward-facing conformations upon TDG binding and protonation of Glu269 have been achieved from microsecond simulations. Both the opening of the periplasmic side and closure of the cytoplasmic side of LacY are consistent with experiments. Our analysis suggest that the conformational changes of LacY are a cumulative consequence of inter-domain H-bonds breaking at the periplasmic side, inter-domain salt-bridge formation at the cytoplasmic side, as well as the TDG orientational changes during the transition. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700