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Measuring Cell Mechanical Properties Using Microindentation. Methods Mol Biol 2023; 2600:3-23. [PMID: 36587087 DOI: 10.1007/978-1-0716-2851-5_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Quantifying cell mechanical properties is of interest to better understand both physiological and pathological cellular processes. Cell mechanical properties are quantified by a finite set of parameters such as the effective Young's modulus or the effective viscosity. These parameters can be extracted by applying controlled forces to a cell and by quantifying the resulting deformation of the cell.Microindentation consists in pressing a cell with a calibrated spring terminated by a rigid tip and by measuring the resulting indentation of the cell. We have developed a microindentation technique that uses a flexible micropipette as a spring. The micropipette has a microbead at its tip, and this spherical geometry allows using analytical models to extract cell mechanical properties from microindentation experiments. We use another micropipette to hold the cell to be indented, which makes this technique well suited to study nonadherent cells, but we also describe how to use this technique on adherent cells.
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Khattak HK, Karpitschka S, Snoeijer JH, Dalnoki-Veress K. Direct force measurement of microscopic droplets pulled along soft surfaces. Nat Commun 2022; 13:4436. [PMID: 35907882 PMCID: PMC9338979 DOI: 10.1038/s41467-022-31910-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 07/08/2022] [Indexed: 11/21/2022] Open
Abstract
When a droplet is placed on a soft surface, surface tension deforms the substrate, creating a capillary ridge. We study how the motion of the ridge dissipates energy in microscopic droplets. Using a micropipette based method, we are able to simultaneously image and measure forces on a microscopic droplet moving at a constant speed along a soft film supported on a rigid substrate. Changing the thickness of the thin film tunes the effective stiffness of the substrate. Thus we can control the ridge size without altering the surface chemistry. We find that the dissipation depends strongly on the film thickness, decreasing monotonically as effective stiffness increases. This monotonic trend is beyond the realm of small deformation theory, but can be explained with a simple scaling analysis. Elastic deformation of soft substrates occurs upon wetting, yet it is challenging to follow its dynamics at a microscale. Khattak et al. show that the force required to pull a droplet along a soft surface decreases monotonically as the film thickness decreases and explain the phenomenon using a scaling analysis.
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Affiliation(s)
- Hamza K Khattak
- Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4M1, Canada
| | - Stefan Karpitschka
- Max Planck Institute for Dynamics and Self-Organization, 37077, Göttingen, Germany
| | - Jacco H Snoeijer
- Physics of Fluids Group, Mesa+ Institute, University of Twente, 7500, AE Enschede, The Netherlands
| | - Kari Dalnoki-Veress
- Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4M1, Canada. .,UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 75005, Paris, France.
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3
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Fortais A, Loukiantchenko E, Dalnoki-Veress K. Writhing and hockling instabilities in twisted elastic fibers. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2021; 44:149. [PMID: 34905133 DOI: 10.1140/epje/s10189-021-00135-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Accepted: 10/06/2021] [Indexed: 06/14/2023]
Abstract
The buckling and twisting of slender, elastic fibers is a deep and well-studied field. A slender elastic rod that is twisted with respect to a fixed end will spontaneously form a loop, or hockle, to relieve the torsional stress that builds. Further twisting results in the formation of plectonemes-a helical excursion in the fiber that extends with additional twisting. Here we use an idealized, micron-scale experiment to investigate the energy stored, and subsequently released, by hockles and plectonemes as they are pulled apart, in analogy with force spectroscopy studies of DNA and protein folding. Hysteresis loops in the snapping and unsnapping inform the stored energy in the twisted fiber structures.
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Affiliation(s)
- Adam Fortais
- Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4M1, Canada
| | - Elsie Loukiantchenko
- Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4M1, Canada
| | - Kari Dalnoki-Veress
- Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4M1, Canada.
- UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 75005, Paris, France.
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4
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Maksymov IS, Pototsky A. Excitation of Faraday-like body waves in vibrated living earthworms. Sci Rep 2020; 10:8564. [PMID: 32444625 PMCID: PMC7244598 DOI: 10.1038/s41598-020-65295-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Accepted: 04/28/2020] [Indexed: 12/03/2022] Open
Abstract
Biological cells and many living organisms are mostly made of liquids and therefore, by analogy with liquid drops, they should exhibit a range of fundamental nonlinear phenomena such as the onset of standing surface waves. Here, we test four common species of earthworm to demonstrate that vertical vibration of living worms lying horizontally on a flat solid surface results in the onset of subharmonic Faraday-like body waves, which is possible because earthworms have a hydrostatic skeleton with a flexible skin and a liquid-filled body cavity. Our findings are supported by theoretical analysis based on a model of parametrically excited vibrations in liquid-filled elastic cylinders using material parameters of the worm's body reported in the literature. The ability to excite nonlinear subharmonic body waves in a living organism could be used to probe, and potentially to control, important biophysical processes such as the propagation of nerve impulses, thereby opening up avenues for addressing biological questions of fundamental impact.
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Affiliation(s)
- Ivan S Maksymov
- Centre for Micro-Photonics, Swinburne University of Technology, Hawthorn, Victoria, 3122, Australia.
| | - Andrey Pototsky
- Department of Mathematics, Faculty of Science Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria, 3122, Australia.
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5
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Böddeker TJ, Karpitschka S, Kreis CT, Magdelaine Q, Bäumchen O. Dynamic force measurements on swimming Chlamydomonas cells using micropipette force sensors. J R Soc Interface 2020; 17:20190580. [PMID: 31937233 PMCID: PMC7014799 DOI: 10.1098/rsif.2019.0580] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 12/10/2019] [Indexed: 11/12/2022] Open
Abstract
Flagella and cilia are cellular appendages that inherit essential functions of microbial life including sensing and navigating the environment. In order to propel a swimming microorganism they displace the surrounding fluid by means of periodic motions, while precisely timed modulations of their beating patterns enable the cell to steer towards or away from specific locations. Characterizing the dynamic forces, however, is challenging and typically relies on indirect experimental approaches. Here, we present direct in vivo measurements of the dynamic forces of motile Chlamydomonas reinhardtii cells in controlled environments. The experiments are based on partially aspirating a living microorganism at the tip of a micropipette force sensor and optically recording the micropipette's position fluctuations with high temporal and sub-pixel spatial resolution. Spectral signal analysis allows for isolating the cell-generated dynamic forces caused by the periodic motion of the flagella from background noise. We provide an analytic, elasto-hydrodynamic model for the micropipette force sensor and describe how to obtain the micropipette's full frequency response function from a dynamic force calibration. Using this approach, we measure the amplitude of the oscillatory forces during the swimming activity of individual Chlamydomonas reinhardtii cells of 26 ± 5 pN, resulting from the coordinated flagellar beating with a frequency of 49 ± 5 Hz. This dynamic micropipette force sensor technique generalizes the applicability of micropipettes as force sensors from static to dynamic force measurements, yielding a force sensitivity in the piconewton range. In addition to measurements in bulk liquid environment, we study the dynamic forces of the biflagellated microswimmer in the vicinity of a solid/liquid interface. As we gradually decrease the distance of the swimming microbe to the interface, we measure a significantly enhanced force transduction at distances larger than the maximum extent of the beating flagella, highlighting the importance of hydrodynamic interactions for scenarios in which flagellated microorganisms encounter surfaces.
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Affiliation(s)
| | | | | | | | - Oliver Bäumchen
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077 Göttingen, Germany
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6
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Micropipette force sensors for in vivo force measurements on single cells and multicellular microorganisms. Nat Protoc 2019; 14:594-615. [PMID: 30697007 DOI: 10.1038/s41596-018-0110-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Measuring forces from the piconewton to millinewton range is of great importance for the study of living systems from a biophysical perspective. The use of flexible micropipettes as highly sensitive force probes has become established in the biophysical community, advancing our understanding of cellular processes and microbial behavior. The micropipette force sensor (MFS) technique relies on measurement of the forces acting on a force-calibrated, hollow glass micropipette by optically detecting its deflections. The MFS technique covers a wide micro- and mesoscopic regime of detectable forces (tens of piconewtons to millinewtons) and sample sizes (micrometers to millimeters), does not require gluing of the sample to the cantilever, and allows simultaneous optical imaging of the sample throughout the experiment. Here, we provide a detailed protocol describing how to manufacture and calibrate the micropipettes, as well as how to successfully design, perform, and troubleshoot MFS experiments. We exemplify our approach using the model nematode Caenorhabditis elegans, but by following this protocol, a wide variety of living samples, ranging from single cells to multicellular aggregates and millimeter-sized organisms, can be studied in vivo, with a force resolution as low as 10 pN. A skilled (under)graduate student can master the technique in ~1-2 months. The whole protocol takes ~1-2 d to finish.
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7
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Agudo-Canalejo J, Discher DE. Biomembrane Adhesion to Substrates Topographically Patterned with Nanopits. Biophys J 2018; 115:1292-1306. [PMID: 30177442 DOI: 10.1016/j.bpj.2018.08.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 07/26/2018] [Accepted: 08/06/2018] [Indexed: 01/24/2023] Open
Abstract
We examine the adhesion of biomembranes to substrates topographically patterned with concave nanopits and identify several universal features in the adhesion process. We find three distinct states, depending on whether the membrane remains flat above the nanopit, partially enters it, or completely adheres to it, and derive analytical conditions for the stability of these states valid for a very general class of nanopit shapes. Surprisingly, completely adhered states are always (meta)stable. We also show that the presence of many nanopits can increase or decrease the effective adhesiveness of a substrate, depending on the tension of the membrane and the strength of the membrane-substrate attraction. Our results have implications regarding several experimental methods, which involve the formation of supported lipid bilayers on substrates patterned with nanopits, as well as observations of decreased spreading of cells and migration of cells toward regions of lower nanopit density on topographically patterned substrates. Furthermore, our predictions can also be directly tested in experiments exploring the adhesion of micropipette-aspirated giant vesicles to such substrates.
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Affiliation(s)
- Jaime Agudo-Canalejo
- Theory & Bio-Systems Department, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany; Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford, United Kingdom; Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania.
| | - Dennis E Discher
- Biophysical Engineering, University of Pennsylvania, Philadelphia, Pennsylvania
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Petit J, Thomi L, Schultze J, Makowski M, Negwer I, Koynov K, Herminghaus S, Wurm FR, Bäumchen O, Landfester K. A modular approach for multifunctional polymersomes with controlled adhesive properties. SOFT MATTER 2018; 14:894-900. [PMID: 29303200 DOI: 10.1039/c7sm01885a] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The bottom-up approach in synthetic biology involves the engineering of synthetic cells by designing biological and chemical building blocks, which can be combined in order to mimic cellular functions. The first step for mimicking a living cell is the design of an appropriate compartment featuring a multifunctional membrane. This is of particular interest since it allows for the selective attachment of different groups or molecules to the membrane. In this context, we report on a modular approach for polymeric vesicles, so-called polymersomes, with a multifunctional surface, namely hydroxyl, alkyne and acrylate groups. We demonstrate that the surface of the polymersome can be functionalized to facilitate imaging, via fluorescent dyes, or to improve the specific adhesion to surfaces by using a biotin functionalization. This generally applicable multifunctionality allows for the covalent integration of various molecules in the membrane of a synthetic cell.
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Affiliation(s)
- Julien Petit
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Göttingen, Germany.
| | - Laura Thomi
- Max Planck Institute for Polymer Research (MPIP), 55128 Mainz, Germany.
| | - Jennifer Schultze
- Max Planck Institute for Polymer Research (MPIP), 55128 Mainz, Germany.
| | - Marcin Makowski
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Göttingen, Germany.
| | - Inka Negwer
- Max Planck Institute for Polymer Research (MPIP), 55128 Mainz, Germany.
| | - Kaloian Koynov
- Max Planck Institute for Polymer Research (MPIP), 55128 Mainz, Germany.
| | - Stephan Herminghaus
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Göttingen, Germany.
| | - Frederik R Wurm
- Max Planck Institute for Polymer Research (MPIP), 55128 Mainz, Germany.
| | - Oliver Bäumchen
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Göttingen, Germany.
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Sawicka A, Babataheri A, Dogniaux S, Barakat AI, Gonzalez-Rodriguez D, Hivroz C, Husson J. Micropipette force probe to quantify single-cell force generation: application to T-cell activation. Mol Biol Cell 2017; 28:3229-3239. [PMID: 28931600 PMCID: PMC5687025 DOI: 10.1091/mbc.e17-06-0385] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 09/08/2017] [Accepted: 09/12/2017] [Indexed: 11/11/2022] Open
Abstract
We describe the micropipette force probe, a novel technique that uses a micropipette as a flexible cantilever that aspirates a coated microbead and brings it into contact with a cell. We apply the technique to quantify mechanical and morphological events occurring during T-cell activation. In response to engagement of surface molecules, cells generate active forces that regulate many cellular processes. Developing tools that permit gathering mechanical and morphological information on these forces is of the utmost importance. Here we describe a new technique, the micropipette force probe, that uses a micropipette as a flexible cantilever that can aspirate at its tip a bead that is coated with molecules of interest and is brought in contact with the cell. This technique simultaneously allows tracking the resulting changes in cell morphology and mechanics as well as measuring the forces generated by the cell. To illustrate the power of this technique, we applied it to the study of human primary T lymphocytes (T-cells). It allowed the fine monitoring of pushing and pulling forces generated by T-cells in response to various activating antibodies and bending stiffness of the micropipette. We further dissected the sequence of mechanical and morphological events occurring during T-cell activation to model force generation and to reveal heterogeneity in the cell population studied. We also report the first measurement of the changes in Young’s modulus of T-cells during their activation, showing that T-cells stiffen within the first minutes of the activation process.
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Affiliation(s)
- Anna Sawicka
- Laboratoire d'Hydrodynamique (LadHyX), Department of Mechanics, Ecole polytechnique-CNRS UMR7646, 91128 Palaiseau, France.,Institut Curie Section Recherche, INSERM U932 and PSL Research University, 75005 Paris, France
| | - Avin Babataheri
- Laboratoire d'Hydrodynamique (LadHyX), Department of Mechanics, Ecole polytechnique-CNRS UMR7646, 91128 Palaiseau, France
| | - Stéphanie Dogniaux
- Institut Curie Section Recherche, INSERM U932 and PSL Research University, 75005 Paris, France
| | - Abdul I Barakat
- Laboratoire d'Hydrodynamique (LadHyX), Department of Mechanics, Ecole polytechnique-CNRS UMR7646, 91128 Palaiseau, France
| | | | - Claire Hivroz
- Institut Curie Section Recherche, INSERM U932 and PSL Research University, 75005 Paris, France
| | - Julien Husson
- Laboratoire d'Hydrodynamique (LadHyX), Department of Mechanics, Ecole polytechnique-CNRS UMR7646, 91128 Palaiseau, France
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10
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Yang Y, Jiang H. Shape and Dynamics of Adhesive Cells: Mechanical Response of Open Systems. PHYSICAL REVIEW LETTERS 2017; 118:208102. [PMID: 28581769 DOI: 10.1103/physrevlett.118.208102] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Indexed: 06/07/2023]
Abstract
Cell adhesion is an essential biological process. However, previous theoretical and experimental studies ignore a key variable, the changes of cellular volume and pressure, during the dynamic adhesion process. Here, we treat cells as open systems and propose a theoretical framework to investigate how the exchange of water and ions with the environment affects the shape and dynamics of cells adhered between two adhesive surfaces. We show that adherent cells can be either stable (convex or concave) or unstable (spontaneous rupture or collapse) depending on the adhesion energy density, the cell size, the separation of two adhesive surfaces, and the stiffness of the flexible surface. Strikingly, we find that the unstable states vanish when cellular volume and pressure are constant. We further show that the detachments of convex and concave cells are very different. The mechanical response of adherent cells is mainly determined by the competition between the loading rate and the regulation of the cellular volume and pressure. Finally, we show that as an open system the detachment of adherent cells is also significantly influenced by the loading history. Thus, our findings reveal a major difference between living cells and nonliving materials.
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Affiliation(s)
- Yuehua Yang
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Hongyuan Jiang
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China
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11
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Schulman RD, Porat A, Charlesworth K, Fortais A, Salez T, Raphaël E, Dalnoki-Veress K. Elastocapillary bending of microfibers around liquid droplets. SOFT MATTER 2017; 13:720-724. [PMID: 27935001 DOI: 10.1039/c6sm02095j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report on the elastocapillary deformation of flexible microfibers in contact with liquid droplets. A fiber is observed to bend more as the size of the contacting droplet is increased. At a critical droplet size, proportional to the bending elastocapillary length, the fiber is seen to spontaneously wind around the droplet. To rationalize these observations, we invoke a minimal model based on elastic beam theory, and find agreement with experimental data. Further energetic considerations provide a consistent prediction for the winding criterion.
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Affiliation(s)
- Rafael D Schulman
- Department of Physics and Astronomy, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1, Canada.
| | - Amir Porat
- Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 75005 Paris, France
| | - Kathleen Charlesworth
- Department of Physics and Astronomy, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1, Canada.
| | - Adam Fortais
- Department of Physics and Astronomy, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1, Canada.
| | - Thomas Salez
- Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 75005 Paris, France and Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Hokkaido 060-0808, Japan
| | - Elie Raphaël
- Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 75005 Paris, France
| | - Kari Dalnoki-Veress
- Department of Physics and Astronomy, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1, Canada. and Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 75005 Paris, France
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12
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Abstract
We have developed a technique to directly quantify cell-substrate adhesion force using micropipette aspiration. The micropipette is positioned perpendicular to the surface of an adherent cell and a constant-rate aspiration pressure is applied. Since the micropipette diameter and the aspiration pressure are our control parameters, we have direct knowledge of the aspiration force, whereas the cell behavior is monitored either in brightfield or interference reflection microscopy. This setup thus allows us to explore a range of geometric parameters, such as projected cell area, adhesion area, or pipette size, as well as dynamical parameters such as the loading rate. We find that cell detachment is a well-defined event occurring at a critical aspiration pressure, and that the detachment force scales with the cell adhesion area (for a given micropipette diameter and loading rate), which defines a critical stress. Taking into account the cell adhesion area, intrinsic parameters of the adhesion bonds, and the loading rate, a minimal model provides an expression for the critical stress that helps rationalize our experimental results.
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13
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Schulman RD, Dalnoki-Veress K. Liquid Droplets on a Highly Deformable Membrane. PHYSICAL REVIEW LETTERS 2015; 115:206101. [PMID: 26613455 DOI: 10.1103/physrevlett.115.206101] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2015] [Indexed: 06/05/2023]
Abstract
We examine the deformation produced by microdroplets atop thin elastomeric and glassy free-standing films. Because of the Laplace pressure, the droplets deform the elastic membrane thereby forming a bulge. Thus, two angles define the droplet or membrane geometry: the angles the deformed bulge and the liquid surface make with the film. These angles are measured as a function of the film tension, and are in excellent agreement with a force balance at the contact line. Finally, we find that if the membrane has an anisotropic tension, the droplets are no longer spherical but become elongated along the direction of high tension.
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Affiliation(s)
- Rafael D Schulman
- Department of Physics and Astronomy, McMaster University, 1280 Main St. W, Hamilton, ON, L8S 4M1, Canada
| | - Kari Dalnoki-Veress
- Department of Physics and Astronomy, McMaster University, 1280 Main St. W, Hamilton, ON, L8S 4M1, Canada
- Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI, Paris, France
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14
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Rabets Y, Backholm M, Dalnoki-Veress K, Ryu WS. Direct measurements of drag forces in C. elegans crawling locomotion. Biophys J 2015; 107:1980-1987. [PMID: 25418179 DOI: 10.1016/j.bpj.2014.09.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 09/02/2014] [Accepted: 09/03/2014] [Indexed: 12/11/2022] Open
Abstract
With a simple and versatile microcantilever-based force measurement technique, we have probed the drag forces involved in Caenorhabditis elegans locomotion. As a worm crawls on an agar surface, we found that substrate viscoelasticity introduces nonlinearities in the force-velocity relationships, yielding nonconstant drag coefficients that are not captured by original resistive force theory. A major contributing factor to these nonlinearities is the formation of a shallow groove on the agar surface. We measured both the adhesion forces that cause the worm's body to settle into the agar and the resulting dynamics of groove formation. Furthermore, we quantified the locomotive forces produced by C. elegans undulatory motions on a wet viscoelastic agar surface. We show that an extension of resistive force theory is able to use the dynamics of a nematode's body shape along with the measured drag coefficients to predict the forces generated by a crawling nematode.
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Affiliation(s)
- Yegor Rabets
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada; Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada
| | - Matilda Backholm
- Department of Physics & Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada
| | - Kari Dalnoki-Veress
- Department of Physics & Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada; Laboratoire de Physico-Chimie Théorique, UMR Centre National de la Recherche Scientifique 7083 GULLIVER, ESPCI, Paris, France
| | - William S Ryu
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada; Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada; Department of Physics, University of Toronto, Toronto, Ontario, Canada.
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15
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Backholm M, Ryu WS, Dalnoki-Veress K. The nematode C. elegans as a complex viscoelastic fluid. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2015; 38:118. [PMID: 25957177 DOI: 10.1140/epje/i2015-15036-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 03/13/2015] [Accepted: 03/13/2015] [Indexed: 06/04/2023]
Abstract
The viscoelastic material properties of the model organism C. elegans were probed with a micropipette deflection technique and modelled with the standard linear solid model. Dynamic relaxation measurements were performed on the millimetric nematode to investigate its viscous characteristics in detail. We show that the internal properties of C. elegans can not be fully described by a simple Newtonian fluid. Instead, a power-law fluid model was implemented and shown to be in excellent agreement with experimental results. The nematode exhibits shear thinning properties and its complex fluid characteristics were quantified. The bending-rate dependence of the internal damping coefficient of C. elegans could affect its gait modulation in different external environments.
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Affiliation(s)
- Matilda Backholm
- Department of Physics & Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, ON, Canada
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16
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Frostad JM, Seth M, Bernasek SM, Leal LG. Direct measurement of interaction forces between charged multilamellar vesicles†. SOFT MATTER 2014; 10:7769-7780. [PMID: 25141827 DOI: 10.1039/c3sm52785a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Depletion-attraction induced adhesion of two giant (∼ 40 μm), charged multilamellar vesicles is studied using a new Cantilevered-Capillary Force Apparatus, developed in this laboratory. The specific goal of this work is to investigate the role of dynamics in the adhesion and de-adhesion processes when the vesicles come together or are pulled apart at a constant velocity. Hydrodynamic effects are found to play an important role in the adhesion and separation of vesicles at the velocities that are studied. Specifically, a period of hydrodynamically controlled drainage of the thin film between vesicles is observed prior to adhesion, and it is shown that the force required to separate a pair of tensed, adhering vesicles increases with increasing separation velocity and membrane tension. It is also shown that the work done to separate the vesicles increases with separation velocity, but exhibits a maximum as the membrane tension is varied.
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Affiliation(s)
- John M Frostad
- Department of Chemical engineering, University of California, Santa Barbara, USA.
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Backholm M, Schulman RD, Ryu WS, Dalnoki-Veress K. Tangling of tethered swimmers: interactions between two nematodes. PHYSICAL REVIEW LETTERS 2014; 113:138101. [PMID: 25302918 DOI: 10.1103/physrevlett.113.138101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Indexed: 06/04/2023]
Abstract
The tangling of two tethered microswimming worms serving as the ends of "active strings" is investigated experimentally and modeled analytically. C. elegans nematodes of similar size are caught by their tails using micropipettes and left to swim and interact at different separations over long times. The worms are found to tangle in a reproducible and statistically predictable manner, which is modeled based on the relative motion of the worm heads. Our results provide insight into the intricate tangling interactions present in active biological systems.
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Affiliation(s)
- Matilda Backholm
- Department of Physics & Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - Rafael D Schulman
- Department of Physics & Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - William S Ryu
- Department of Physics and the Donnelly Centre, University of Toronto, Toronto, Ontario M5S 1A7, Canada
| | - Kari Dalnoki-Veress
- Department of Physics & Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1, Canada and Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI, Paris, France
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18
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Schulman RD, Backholm M, Ryu WS, Dalnoki-Veress K. Dynamic force patterns of an undulatory microswimmer. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:050701. [PMID: 25353731 DOI: 10.1103/physreve.89.050701] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Indexed: 06/04/2023]
Abstract
We probe the viscous forces involved in the undulatory swimming of the model organism C. elegans. Using micropipette deflection, we attain direct measurements of lateral and propulsive forces produced in response to the motion of the worm. We observe excellent agreement of the results with resistive force theory, through which we determine the drag coefficients of this organism. The drag coefficients are in accordance with theoretical predictions. Using a simple scaling argument, we obtain a relationship between the size of the worm and the forces that we measure, which well describes our data.
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Affiliation(s)
- Rafael D Schulman
- Department of Physics and Astronomy and The Brockhouse Institute for Materials Research, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1
| | - Matilda Backholm
- Department of Physics and Astronomy and The Brockhouse Institute for Materials Research, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1
| | - William S Ryu
- Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario, Canada M5S 1A7
| | - Kari Dalnoki-Veress
- Department of Physics and Astronomy and The Brockhouse Institute for Materials Research, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1 and Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI, Paris, France
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19
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Wu TH, Chou YW, Chiu PH, Tang MJ, Hu CW, Yeh ML. Validation of the effects of TGF-β1 on tumor recurrence and prognosis through tumor retrieval and cell mechanical properties. Cancer Cell Int 2014; 14:20. [PMID: 24581230 PMCID: PMC3973896 DOI: 10.1186/1475-2867-14-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 02/20/2014] [Indexed: 01/06/2023] Open
Abstract
Background In vivo, the transforming growth factor-beta1 (TGF-β1)-induced epithelial to mesenchymal transition (EMT) occurs in seconds during cancer cells intravasation and extravasation. Although it has been established that cellular stiffness can change as a cancer cell transformed, the precise relationship between TGF-β1-induced mesenchymal stem cell mechanics and cancer prognosis remains unclear. Accordingly, it is hard to define the effects of EMT on cell mechanical properties (CMs), tumor recurrence and metastasis risks. This study bridges physical and pathological disciplines to reconcile single-cell mechanical measurements of tumor cells. Methods and results We developed a microplate measurement system (MMS) and revealed the intrinsic divergent tumor composition of retrieval cells by cell stiffness and adhesion force and flow cytometry analysis. After flow cytometry sorting, we could measure the differences in CMs of the Sca-1+-CD44+ (mesenchymal-stem-cell-type) and the other subgroups. As well as the stiffer and heterogeneous compositions among tumor tissues with higher recurrence risk were depicted by MMS and atomic force microscopy (AFM). An in vitro experiment validated that Lewis lung carcinoma (LLC) cells acquired higher CMs and motility after EMT, but abrogated by SB-505124 inhibition. Concomitantly, the CD31, MMP13 and TGF-β1 enriched micro-environment in the tumor was associated with higher recurrence and distal lung metastasis risks. Furthermore, we report a comprehensive effort to correlate CMs to tumor-prognosis indicators, in which a decreased body weight gain ratio (BWG) and increased tumor weight (TW) were correlated with increased CMs. Conclusions Together, we determined that TGF-β1 was significantly associated with malignant tumor progressing. In terms of clinical applications, local tumor excision followed by MMS analysis offers an opportunity to predict tumor recurrence and metastasis risks.
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Affiliation(s)
| | | | | | | | | | - Ming-Long Yeh
- Institute of Biomedical Engineering, National Cheng Kung University, No,1 University Road, Tainan City 701, Taiwan.
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20
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Zablotskii V, Dejneka A, Kubinová Š, Le-Roy D, Dumas-Bouchiat F, Givord D, Dempsey NM, Syková E. Life on magnets: stem cell networking on micro-magnet arrays. PLoS One 2013; 8:e70416. [PMID: 23936425 PMCID: PMC3731273 DOI: 10.1371/journal.pone.0070416] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 06/23/2013] [Indexed: 11/18/2022] Open
Abstract
Interactions between a micro-magnet array and living cells may guide the establishment of cell networks due to the cellular response to a magnetic field. To manipulate mesenchymal stem cells free of magnetic nanoparticles by a high magnetic field gradient, we used high quality micro-patterned NdFeB films around which the stray field's value and direction drastically change across the cell body. Such micro-magnet arrays coated with parylene produce high magnetic field gradients that affect the cells in two main ways: i) causing cell migration and adherence to a covered magnetic surface and ii) elongating the cells in the directions parallel to the edges of the micro-magnet. To explain these effects, three putative mechanisms that incorporate both physical and biological factors influencing the cells are suggested. It is shown that the static high magnetic field gradient generated by the micro-magnet arrays are capable of assisting cell migration to those areas with the strongest magnetic field gradient, thereby allowing the build up of tunable interconnected stem cell networks, which is an elegant route for tissue engineering and regenerative medicine.
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21
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Su YC, Chen JZY. Pressing soft membrane on a self-avoiding polymer against a flat wall. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 87:052706. [PMID: 23767565 DOI: 10.1103/physreve.87.052706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Indexed: 06/02/2023]
Abstract
A polymer-membrane interacting system can produce a variety of structures. Here, we theoretically study a model system in which a membrane pushes a polymer against a hard surface; we show that a first-order structural phase transition can occur. Using a Monte Carlo simulation, we reveal that the system undergoes a transition from a confined (bump) state to a strongly confined (flattened-out) state as the pressure increases. A scaling argument is also made to understand the physical mechanism behind the phase transition and the properties of each state.
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Affiliation(s)
- Yu-Cheng Su
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
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22
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Frostad JM, Collins MC, Leal LG. Cantilevered-capillary force apparatus for measuring multiphase fluid interactions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:4715-4725. [PMID: 23540603 DOI: 10.1021/la304115k] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A new instrument is presented for investigating interactions between individual colloidal particles, emulsion droplets, foam bubbles, and other particle-particle or particle-surface interactions. Measurement capabilities are demonstrated by measuring interfacial tension, coalescence time for emulsion droplets, adhesion between giant multilamellar vesicles, and adhesion between model food emulsion particles. The magnitude of the interaction force that can be measured or imposed, ranges from 1 nN to 1 mN for particles ranging in size from 10 μm to 1 mm in diameter.
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Affiliation(s)
- John M Frostad
- Department of Chemical Engineering, University of California, Santa Barbara, California 93016-5080, United States.
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Viscoelastic properties of the nematode Caenorhabditis elegans, a self-similar, shear-thinning worm. Proc Natl Acad Sci U S A 2013; 110:4528-33. [PMID: 23460699 DOI: 10.1073/pnas.1219965110] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Undulatory motion is common to many creatures across many scales, from sperm to snakes. These organisms must push off against their external environment, such as a viscous medium, grains of sand, or a high-friction surface; additionally they must work to bend their own body. A full understanding of undulatory motion, and locomotion in general, requires the characterization of the material properties of the animal itself. The material properties of the model organism Caenorhabditis elegans were studied with a micromechanical experiment used to carry out a three-point bending measurement of the worm. Worms at various developmental stages (including dauer) were measured and different positions along the worm were probed. From these experiments we calculated the viscoelastic properties of the worm, including the effective spring constant and damping coefficient of bending. C. elegans moves by propagating sinusoidal waves along its body. Whereas previous viscoelastic approaches to describe the undulatory motion have used a Kelvin-Voigt model, where the elastic and viscous components are connected in parallel, our measurements show that the Maxwell model, where the elastic and viscous components are in series, is more appropriate. The viscous component of the worm was shown to be consistent with a non-Newtonian, shear-thinning fluid. We find that as the worm matures it is well described as a self-similar elastic object with a shear-thinning damping term and a stiffness that becomes smaller as one approaches the tail.
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25
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Echarri A, Muriel O, Pavón DM, Azegrouz H, Escolar F, Terrón MC, Sanchez-Cabo F, Martínez F, Montoya MC, Llorca O, Del Pozo MA. Caveolar domain organization and trafficking is regulated by Abl kinases and mDia1. J Cell Sci 2012; 125:3097-113. [PMID: 22454521 DOI: 10.1242/jcs.090134] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The biology of caveolin-1 (Cav1)/caveolae is intimately linked to actin dynamics and adhesion receptors. Caveolar domains are organized in hierarchical levels of complexity from curved or flattened caveolae to large, higher-order caveolar rosettes. We report that stress fibers controlled by Abl kinases and mDia1 determine the level of caveolar domain organization, which conditions the subsequent inward trafficking of caveolar domains induced upon loss of cell adhesion from the extracellular matrix. Abl-deficient cells have fewer stress fibers, a smaller pool of stress-fiber co-aligned Cav1 and increased clustering of Cav1/caveolae at the cell surface. Defective caveolar linkage to stress fibers prevents the formation of big caveolar rosettes upon loss of cell adhesion, correlating with a lack of inward trafficking. Live imaging of stress fibers and Cav1 showed that the actin-linked Cav1 pool loses its spatial organization in the absence of actin polymerization and is dragged and clustered by depolymerizing filaments. We identified mDia1 as the actin polymerization regulator downstream of Abl kinases that controls the stress-fiber-linked Cav1 pool. mDia1 knockdown results in Cav1/caveolae clustering and defective inward trafficking upon loss of cell adhesion. By contrast, cell elongation imposed by the excess of stress fibers induced by active mDia1 flattens caveolae. Furthermore, active mDia1 rescues the actin co-aligned Cav1 pool and Cav1 inward trafficking upon loss of adhesion in Abl-deficient cells. Thus, caveolar domain organization and trafficking are tightly coupled to adhesive and stress fiber regulatory pathways.
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Affiliation(s)
- Asier Echarri
- Integrin Signaling Laboratory, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro, 3, 28029, [corrected] Madrid, Spain.
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Formation of oligovesicular vesicles by micromanipulation. MEMBRANES 2011; 1:265-74. [PMID: 24957868 PMCID: PMC4021875 DOI: 10.3390/membranes1040265] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 09/20/2011] [Accepted: 09/21/2011] [Indexed: 11/17/2022]
Abstract
Cell-sized lipid bilayer membrane vesicles (giant vesicles, GVs) or semi-vesicles were formed from egg yolk phosphatidylcholine on a platinum electrode under applied electric voltage by electroformation. Micromanipulation of the semi-vesicle by first pressing its membrane with a glass microneedle and then withdrawing the needle left a GV in the interior of the vesicle. During the process, an aqueous solution of Ficoll that filled the needle was introduced into the newly formed inner vesicle and remained encapsulated. Approximately 50% of attempted micromanipulation resulted in the formation of an inner daughter vesicle, “microvesiculation”. By repeating the microvesiculation process, multiple inner GVs could be formed in a single parent semi-vesicle. A semi-vesicle with inner GVs could be detached from the electrode by scraping with a microneedle, yielding an oligovesicular vesicle (OVV) with desired inner aqueous contents. Microvesiculation of a GV held on the tip of a glass micropipette was also possible, and this also produced an OVV. Breaking the membrane of the parent semi-vesicle by micromanipulation with a glass needle after microvesiculation, released the inner GVs. This protocol may be used for controlled formation of GVs with desired contents.
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Yang S, Pelton R, Raegen A, Montgomery M, Dalnoki-Veress K. Nanoparticle flotation collectors: mechanisms behind a new technology. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:10438-10446. [PMID: 21790133 DOI: 10.1021/la2016534] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
This is the first report describing a new technology where hydrophobic nanoparticles adsorb onto much larger, hydrophilic mineral particle surfaces to facilitate attachment to air bubbles in flotation. The adsorption of 46 nm cationic polystyrene nanoparticles onto 43 μm diameter glass beads, a mineral model, facilitates virtually complete removal of the beads by flotation. As little as 5% coverage of the bead surfaces with nanoparticles promotes high flotation efficiencies. The maximum force required to pull a glass bead from an air bubble interface into the aqueous phase was measured by micromechanics. The pull-off force was 1.9 μN for glass beads coated with nanoparticles, compared to 0.0086 μN for clean beads. The pull-off forces were modeled using Scheludko's classical expression. We propose that the bubble/bead contact area may not be dry (completely dewetted). Instead, for hydrophobic nanoparticles sitting on a hydrophilic surface, it is possible that only the nanoparticles penetrate the air/water interface to form a three-phase contact line. We present a new model for pull-off forces for such a wet contact patch between the bead and the air bubble. Contact angle measurements of both nanoparticle coated glass and smooth films from dissolved nanoparticles were performed to support the modeling.
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Affiliation(s)
- Songtao Yang
- McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7
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28
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Colbert MJ, Brochard-Wyart F, Fradin C, Dalnoki-Veress K. Squeezing and detachment of living cells. Biophys J 2011; 99:3555-62. [PMID: 21112279 DOI: 10.1016/j.bpj.2010.10.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Revised: 10/03/2010] [Accepted: 10/06/2010] [Indexed: 01/16/2023] Open
Abstract
The interaction of living cells with their environment is linked to their adhesive and elastic properties. Even if the mechanics of simple lipid membranes is fairly well understood, the analysis of single cell experiments remains challenging in part because of the mechanosensory response of cells to their environment. To study the mechanical properties of living cells we have developed a tool that borrows from micropipette aspiration techniques, atomic force microscopy, and the classical Johnson-Kendall-Roberts test. We show results from a study of the adhesion properties of living cells, as well as the elastic response and relaxation. We present models that are applied throughout the different stages of an experiment, which indicate that the contribution of the different components of the cell are active at various stages of compression, retraction, and detachment. Finally, we present a model that attempts to elucidate the surprising logarithmic relaxation observed when the cell is subjected to a given deformation.
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Affiliation(s)
- Marie-Josée Colbert
- Department of Physics & Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada
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Wang X, He D, Chen L, Chen T, Jin H, Cai J, Chen Y. Cell-surface ultrastructural changes during the in vitro neuron-like differentiation of rat bone marrow-derived mesenchymal stem cells. SCANNING 2011; 33:69-77. [PMID: 21445986 DOI: 10.1002/sca.20229] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Accepted: 02/28/2011] [Indexed: 05/30/2023]
Abstract
The neuron-like differentiation of bone marrow-derived mesenchymal stem cells (BMMSCs) has been extensively studied. However, the alternations of the cell-surface ultrastructures and the membrane tension/reservoir of the cells during this differentiation process are poorly understood. Therefore, atomic force microscopy (AFM) was utilized in this study to observe the cell-surface ultrastructural changes among rat bone marrow-derived mesenchymal stem cells (rBMMSCs), partially differentiated cells, and fully differentiated neuron-like cells. By analyzing the stiffness of plasma membranes, lamellipodial extensions, average heights of small membrane protrusions and relatively larger uplifted structures, and peak-peak spacing among protrusions and/or uplifted structures, we found that the membrane reservoir may potentially decrease upon the differentiation from rBMMSCs to partially differentiated cells and to fully differentiated neuron-like cells. The results may help to better understanding the membrane tension of various types of cells and related biological processes, such as membrane traffic, cell adhesion, motility, differentiation, among others. The data also implies that AFM may be a useful tool for evaluating membrane reservoir by imaging cell-surface ultrastructures.
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Affiliation(s)
- Xiaoping Wang
- Department of Anesthesiology, The First Affiliated Hospital, Jinan University, Guangzhou, China
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