Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Volume 67, Number 19
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session T05: Biological Fluid Dynamics: Cells |
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Chair: Luoding Zhu, Indiana University-Purdue University Indianapolis Room: 132 |
Monday, November 21, 2022 4:10PM - 4:23PM |
T05.00001: Modeling the interplay of mechanosensitive adhesion and membrane tension for polarization and shape determination in crawling cells Yuzhu Chen, Padmini Rangamani, David Saintillan The initiation of directional cell motion requires symmetry breaking that can happen both with or without external stimuli. During cell crawling, forces generated by the cytoskeleton and their transmission through mechanosensitive adhesions to the extracellular substrate play a crucial role. In a recently proposed 1D model (Sens, PNAS 2020), a mechanical feedback loop between force-sensitive adhesions and cell tension was shown to be sufficient to explain spontaneous symmetry breaking and multiple motility patterns through stick-slip dynamics, without the need to account for signaling networks or active polar gels. We extend this model to 2D to study the interplay between cell shape and mechanics during crawling. Through a local force balance along the deformable boundary, we show that the membrane tension coupled with shape change can regulate the spatiotemporal evolution of the stochastic binding of mechanosensitive adhesions. Based on this model, we perform a linear stability analysis and determine the unstable parameter regimes where spontaneous symmetry breaking can take place. Using non-linear simulations, we show that starting from a randomly perturbed circular shape, this instability can lead to keratocyte-like shapes that are robust for a wide range of parameters. |
Monday, November 21, 2022 4:23PM - 4:36PM |
T05.00002: Extremely fast firing mechanism of sea anemone's stinging cell Elijah G James, Leslie Babonis, Chris Roh Cnidarians are known for their explosive cnidocyte (stinging cell), used mainly for predation. They use these explosive cells in aqueous environments to capture prey and defend themselves in seemingly unfavorable conditions given the dense medium that imposes a high drag. Moreover, previous studies show that cnidocytes vary in size, shape, and firing mechanisms. Beyond the biology of cnidocytes, the lack of pre-existing research surrounding the harpoon firing apparatus necessitates a kinematic and mechanical analysis. Recently, we have successfully imaged the firing mechanism of a cnidocyte of Nematostella vectensis using micro-high speed videography. The video shows that the firing mechanism utilizes the release of large amounts of strain energy stored in a bent elastic harpoon. To further study the newly identified firing mechanism in a more controlled setting, we experimentally modeled the firing mechanism using bent Nitinol wire. The mechanical model operating at a wide range of Reynolds number were tested. |
Monday, November 21, 2022 4:36PM - 4:49PM |
T05.00003: Artificial cytoplasmic streaming Weida Liao, Moritz Kreysing, Eric Lauga Recent experiments in cell biology have probed the impact of artificially-induced intracellular flows and transport in cell division. Using focused light localised in a small region of the cell, a global thermo-viscous flow was induced inside the cell in these studies; this is known as focused-light-induced cytoplasmic streaming (FLUCS). Here we present an analytical, theoretical model of FLUCS. The focused light induces a small, local temperature change, causing a small change in the density and viscosity of the fluid locally. This heat spot translates along a finite scan path. We show that the leading-order instantaneous flow results from thermal expansion and depends linearly on the heat-spot amplitude. The net displacement of a passive tracer after a full scan period is quadratic in the heat-spot amplitude and is due to both thermal expansion and thermal viscosity changes. The far-field average velocity of tracers is a source dipole, showing excellent agreement with recent experimental data. Our quantitative model will enable future work on artificial cytoplasmic streaming. |
Monday, November 21, 2022 4:49PM - 5:02PM |
T05.00004: Surface-morphology-induced oriented growth in natural and artificial tip-growing systems Chan Jin Park, Ho-Young Kim Tip growth is a growth scheme adopted by various cells that transcend species, as exemplified by pollen tubes and root hairs of plants, and germ tubes of fungi. We have previously developed an artificial tip-growing system based on non-solvent induced phase separation (NIPS) of a polymer solution. With the goal of enhancing our understandings of the tip-growing cells using the artificial system, we here show that on a linearly grooved surface, the tip-growing polymer precipitates tend to grow in the direction perpendicular to the pattern. We rationalize how the tip-growing scheme found in natural and artificial systems results in such surface-morphology-induced oriented growth. We also construct a theoretical model to predict the growth direction change upon passing the pattern, and validate the model using experimental results. |
Monday, November 21, 2022 5:02PM - 5:15PM |
T05.00005: Self-Assembly and Morpho-Topological Changes of Klebsiella Pneumoniae in drying droplets Abdur Rasheed, Omkar Hegde, Ritika Chatterjee, Srinivas R Sampathirao, Dipshikha chakravortty, Saptarshi Basu Biofluid droplets ejected from infected humans and animals are a significant source of disease transmission.. The fate of pathogens in these droplets depend on their resistance to the Physico-chemical changes in their environment(droplet). While many pathogens die during the phase change process, some survive these conditions. The study focus on bacteria-laden droplets, drying on a glass substrate. Klebsiella pneumoniae, an opportunistic bacterium that commonly infects humans, is suspended in Milli-Q water and surrogate respiratory fluid and the droplets are allowed to dry in a controlled environment. Micro-PIV quantifies the flow inside the droplet, while microscopy interferometry technique is used to analyze the thin film instability. Confocal microscopies reveal the bacterial self-assembly mechanism. SEM and AFM reveal the morpho-topological variations in bacterial deposits. An order to disorder transition in bacterial packing is seen at the edge deposits. The packing density variation correlates well with the viability and infectivity variations of the deposited bacteria. The insights obtained from this study will help understand disease transfer through droplets, e.g., through open wounds. |
Monday, November 21, 2022 5:15PM - 5:28PM |
T05.00006: Modeling and simulation of an osteocyte cellular process interacting with fluid flow in three dimensions Jared Barber, Luoding Zhu, Maxim Mukhin, Vanessa Maybruck An osteocyte is a bone cell located inside hard bone matrix in an interstice called a lacuna. It has many dendritic structures called processes that extend outward through the bone matrix through openings called canaliculi. Osteocytes are believed to play an important role in bone development as they can sense stress applied by the interstitial fluid flow and respond by releasing signals that regulate bone remodeling. Experiments have suggested that the stress and strain typically experienced at the macroscale tissue level have to be amplified at least 10X in order for osteocytes to have a significant response in vivo. The mechanisms by which stress/strain is amplified and localized is not yet well understood. |
Monday, November 21, 2022 5:28PM - 5:41PM |
T05.00007: A three-dimensional mathematical model of a viscoelastic osteocyte and its interaction with the surrounding flow Nigar Karimli, Jared Barber, Luoding Zhu Osteocytes, the most prevalent bone cells, regulate bone remodeling through mechanotransduction whereby they sense mechanical stimuli and respond by releasing biochemical signals that, in this context, cause other cells to grow or degrade bone. The cells are encased in bone with arms or processes that connect to each other through the surrounding bone material. The bone's hardness can make experimental studies difficult. Models have risen as a promising alternative. At the same time, the complex geometry of the system can prove challenging for modelers and many have made simplifying assumptions in their studies. While this is understandable and useful, we wish to fully understand the implications of these assumptions and to also better understand the forces that can arise during mechanotransduction. To consider such questions, we have developed a three-dimensional model of an osteocyte that can be used to consider the forces that the surrounding fluid exerts on the osteocyte. We model the cell membrane and cytoskeleton as an interconnected network of viscoelastic elements or damped springs. In addition to the viscoelastic forces along each spring, we include other forces to model the properties of the cell that include a non-negligible bending rigidity, total and local area conservation of the membrane, and total volume conservation. They are prescribed using corresponding energies and the resulting forces are computed using the principle of virtual work. The fluid is modeled using the lattice-Boltzmann (D3Q19) method and the fluid-structure interactions are handled using the immersed boundary method. We share our results for this model including estimated motion and forces on an idealized ellipsoidal osteocyte immersed in the flow. |
Monday, November 21, 2022 5:41PM - 5:54PM |
T05.00008: Predicting the mechanical cues experienced by hydrogel-coated stem cells in transit to the liver Simon Finney, Sarah L Waters, Matthew Hennessy, Andreas Muench Liver diseases are the fastest-growing major cause of death in the UK, with a 400% |
Monday, November 21, 2022 5:54PM - 6:07PM |
T05.00009: Transport of breast cancer cells in micro-vessel Lahcen Akerkouch, Trung B Le, Amanda Haage, Aaron Vanyo During cancer metastasis, tumor cells disseminate from the primary tumor to other parts of the human body by exploiting the blood or lymphatic circulatory systems. This process has been studied by a number of numerical simulations. However, most computational models use an idealized spherical shape as the geometrical model for cancer cells without considering the presence of the nucleus, cytosol and cytoskeleton, which are essential to investigate the mechanical and migratory behaviors. In this work, we constructed a realistic model of a cancer cell based on confocal microscopy images where these structures are visualized with immunflourescence. The transport of the cancer cell is simulated using a fluid-structure interaction approach, which couples the dynamics of the cancer cell in fluid flows. Dissipative Particle Dynamics is used to model the cell dynamics (membrane, nucleus and cytosol). The cytoskeleton components (actin filament, intermediate filament and microtubes) are modeled using non-linear Worm-Like Chain springs. The extracellular flow is modeled with the Immersed Boundary Method, which allows the simulation of fluid flows in complex vasculatures. We will report and compare the history of cancer cell dynamics as it traverses along the fluid flows of vasculatures. |
Monday, November 21, 2022 6:07PM - 6:20PM |
T05.00010: Enhanced stiffness-based sorting of cancer cells using a microfluidic with slanted zig-zag ridges and step-wise compression Samuel K Cheng, Maryam Jalali-Mousavi, Jian Sheng The deformability of tumor cells provides information about the metastatic capabilities of cancer and the ability to sort tumor cells, especially circulating tumor cells (CTCs), based on the stiffness. CTCs of different stiffness can be sorted by hydrophoresis that utilizes slanted or herringbone uniform ridges. When CTCs are deformed by the ridges, a transverse force proportional to cell membrane stiffness is generated to enable crossflow migration. To accentuate this sorting mechanism and sensitivity, we proposed a new 3D microfluidic design that incorporates slanted zig-zag ridges and step-wise progressive compression that collectively increase the elastic forces and residence time. Numerical simulation was performed to determine the trajectories of cells with different stiffness and the optimal design parameters. Experimental validation will be performed using PC-3 cells treated with or without cytochalasin that chemically reduces cell stiffness while maintaining a similar diameter. Further comparisons will be done between the proposed new design with the conventional uniform ridges design. Additional modeling efforts on cell-compliant wall interaction will also be provided. |
Monday, November 21, 2022 6:20PM - 6:33PM |
T05.00011: Fingerprinting circulating tumor cells (CTCs) passing through narrow passages with membrane viscoelasticity Jian Sheng, Kok Suen Cheng, Kimberly Lopez Atomic force microscopy (AFM) can resolve nanoscale cell surface features and perform mechanical characterization of living cells and tissues. Anecdotal observations suggest that metastasized tumor cells bear their phenotypical signatures in their membrane characteristics. In this work, we present a new methodology allowing us to quantify the mechanical properties of cells passing through narrow passage via force-deformation relations (F-D curves) by nano-indentation, as well as develop a novel mathematical framework to quantify cell membranes viscoelasticity by performing Ting's integral over F-D measurements to differentiate cancer phenotypes. We have developed a custom-made flow cell that enables simultaneous microscopic observation and AFM experimentation. Three cell lines, prostate (PC3), breast (T47D), and lung (A549) carcinomas are used for this kernel study. Gold-coated probes (k=0.03N/m) are used to allow measurements on the soft cell membrane. Differing from past studies, we probe the membrane with large indentations. Results show distinctive hysteresis between loading and unloading of the membrane. It is also found that the multi-power law model is more suitable for cancer characterization. These viscoelasticity measurements are used to inform numerical simulation to study cell-flow-wall interactions in confinement. |
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