The Experts below are selected from a list of 354 Experts worldwide ranked by ideXlab platform
Denis Wirtz - One of the best experts on this subject based on the ideXlab platform.
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High-throughput ballistic injection Nanorheology to measure cell mechanics
Nature Protocols, 2012Co-Authors: Pei-hsun Wu, Wei-chiang Chen, Yiider Tseng, Christopher M Hale, Denis WirtzAbstract:High-throughput ballistic injection Nanorheology is a method for the quantitative study of cell mechanics. Cell mechanics are measured by ballistic injection of submicron particles into the cytoplasm of living cells and tracking the spontaneous displacement of the particles at high spatial resolution. The trajectories of the cytoplasm-embedded particles are transformed into mean-squared displacements, which are subsequently transformed into frequency-dependent viscoelastic moduli and time-dependent creep compliance of the cytoplasm. This method allows for the study of a wide range of cellular conditions, including cells inside a 3D matrix, cell subjected to shear flows and biochemical stimuli, and cells in a live animal. Ballistic injection lasts
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high throughput ballistic injection Nanorheology to measure cell mechanics
Nature Protocols, 2012Co-Authors: Pei-hsun Wu, Wei-chiang Chen, Yiider Tseng, Christopher M Hale, Denis WirtzAbstract:High-throughput ballistic injection Nanorheology is a method for the quantitative study of cell mechanics. Cell mechanics are measured by ballistic injection of submicron particles into the cytoplasm of living cells and tracking the spontaneous displacement of the particles at high spatial resolution. The trajectories of the cytoplasm-embedded particles are transformed into mean-squared displacements, which are subsequently transformed into frequency-dependent viscoelastic moduli and time-dependent creep compliance of the cytoplasm. This method allows for the study of a wide range of cellular conditions, including cells inside a 3D matrix, cell subjected to shear flows and biochemical stimuli, and cells in a live animal. Ballistic injection lasts <1 min and is followed by overnight incubation. Multiple particle tracking for one cell lasts <1 min. Forty cells can be examined in <1 h.
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chapter 18 sensing cytoskeletal mechanics by ballistic intracellular Nanorheology bin coupled with cell transfection
Methods in Cell Biology, 2008Co-Authors: Melissa S Thompson, Denis WirtzAbstract:Abstract Key processes in normal and diseased cells depend directly or indirectly on the viscoelastic properties of the cytoplasm. Particle‐tracking microrheology is a highly versatile method that measures the viscoelastic properties of cytoplasm directly by tracking fluorescent nanoparticles embedded in the cytoskeleton with high spatial and temporal resolutions. Here we present a new method that combines cell transfection, ballistic injection, and particle‐tracking microrheology to monitor changes in cytoplasmic micromechanics following controlled changes in protein expression. We demonstrate that cells transfected with GFP (green fluorescent protein) display viscoelastic properties identical to untransfected fibroblasts, that low levels of expression of GFP‐α‐actinin do not affect cell microrheology, and that the transient transfection with GFP‐C3 transferase reduces the elasticity of the cytoplasm of fibroblasts to a similar extent as C3 transferase toxin, which de‐activates the GTPase Rho. Combining cell transfection with particle‐tracking microrheology opens the way to quantitative, single live‐cell mechanical studies where stable cell lines cannot be easily established, but where commonly used transfections can be exploited to manipulate cytoskeletal organization.
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Nuclear Lamin A/C Deficiency Induces Defects in Cell Mechanics, Polarization, and Migration ☆
Biophysical Journal, 2007Co-Authors: Christopher M Hale, Yiider Tseng, Porntula Panorchan, Shyam B Khatau, Jerry P. George, Colin L. Stewart, Didier Hodzic, Denis WirtzAbstract:Lamin A/C is a major constituent of the nuclear lamina, a thin filamentous protein layer that lies beneath the nuclear envelope. Here we show that lamin A/C deficiency in mouse embryonic fibroblasts (Lmna−/− MEFs) diminishes the ability of these cells to polarize at the edge of a wound and significantly reduces cell migration speed into the wound. Moreover, lamin A/C deficiency induces significant separation of the microtubule organizing center (MTOC) from the nuclear envelope. Investigations using ballistic intracellular Nanorheology reveal that lamin A/C deficiency also dramatically affects the micromechanical properties of the cytoplasm. Both the elasticity (stretchiness) and the viscosity (propensity of a material to flow) of the cytoplasm in Lmna−/− MEFs are significantly reduced. Disassembly of either the actin filament or microtubule networks in Lmna+/+ MEFs results in decrease of cytoplasmic elasticity and viscosity down to levels found in Lmna−/− MEFs. Together these results show that both the mechanical properties of the cytoskeleton and cytoskeleton-based processes, including cell motility, coupled MTOC and nucleus dynamics, and cell polarization, depend critically on the integrity of the nuclear lamina, which suggest the existence of a functional mechanical connection between the nucleus and the cytoskeleton. These results also suggest that cell polarization during cell migration requires tight mechanical coupling between MTOC and nucleus, which is mediated by lamin A/C.
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probing cellular mechanical responses to stimuli using ballistic intracellular Nanorheology
Methods in Cell Biology, 2007Co-Authors: Porntula Panorchan, Yiider Tseng, Denis Wirtz, Brian R Daniels, Thomas P KoleAbstract:Abstract We describe a new method to measure the local and global micromechanical properties of the cytoplasm of single living cells in their physiological milieu and subjected to external stimuli. By tracking spontaneous, Brownian movements of individual nanoparticles of diameter ≥100 nm distributed within the cell with high spatial and temporal resolutions, the local viscoelastic properties of the intracellular milieu can be measured in different locations within the cell. The amplitude and the time‐dependence of the mean‐squared displacement of each nanoparticle directly reflect the elasticity and the viscosity of the cytoplasm in the vicinity of the nanoparticle. In our previous versions of particle tracking, we delivered nanoparticles via microinjection, which limited the number of cells amenable to measurement, rendering our technique incompatible with high‐throughput experiments. Here we introduce ballistic injection to effectively deliver a large number of nanoparticles to a large number of cells simultaneously. When coupled with multiple particle tracking, this new method—ballistic intracellular Nanorheology (BIN)—makes it now possible to probe the viscoelastic properties of cells in high‐throughput experiments, which require large quantities of injected cells for seeding in various conditions. For instance, BIN allows us to probe an ensemble of cells embedded deeply inside a three‐dimensional extracellular matrix or as a monolayer of cells subjected to shear flows.
Yiider Tseng - One of the best experts on this subject based on the ideXlab platform.
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mechanics
Nat Protoc., 2015Co-Authors: Pei-hsun Wu, C. Hale, Wei-chiang Chen, Jerry S.h. Lee, Yiider Tseng, Daniel WirtzAbstract:High-throughput ballistic injection Nanorheology is a method for the quantitative study of cell mechanics. Cell mechanics are measured by ballistic injection of submicron particles into the cytoplasm of living cells and tracking the spontaneous displacement of the particles at high spatial resolution. The trajectories of the cytoplasm-embedded particles are transformed into mean-squared displacements, which are subsequently transformed into frequency-dependent viscoelastic moduli and time-dependent creep compliance of the cytoplasm. This method allows for the study of a wide range of cellular conditions, including cells inside a 3D matrix, cell subjected to shear flows and biochemical stimuli, and cells in a live animal. Ballistic injection lasts < 1 min and is followed by overnight incubation. Multiple particle tracking for one cell lasts < 1 min. Forty cells can be examined in < 1 h.
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High-throughput ballistic injection Nanorheology to measure cell mechanics
Nature Protocols, 2012Co-Authors: Pei-hsun Wu, Wei-chiang Chen, Yiider Tseng, Christopher M Hale, Denis WirtzAbstract:High-throughput ballistic injection Nanorheology is a method for the quantitative study of cell mechanics. Cell mechanics are measured by ballistic injection of submicron particles into the cytoplasm of living cells and tracking the spontaneous displacement of the particles at high spatial resolution. The trajectories of the cytoplasm-embedded particles are transformed into mean-squared displacements, which are subsequently transformed into frequency-dependent viscoelastic moduli and time-dependent creep compliance of the cytoplasm. This method allows for the study of a wide range of cellular conditions, including cells inside a 3D matrix, cell subjected to shear flows and biochemical stimuli, and cells in a live animal. Ballistic injection lasts
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high throughput ballistic injection Nanorheology to measure cell mechanics
Nature Protocols, 2012Co-Authors: Pei-hsun Wu, Wei-chiang Chen, Yiider Tseng, Christopher M Hale, Denis WirtzAbstract:High-throughput ballistic injection Nanorheology is a method for the quantitative study of cell mechanics. Cell mechanics are measured by ballistic injection of submicron particles into the cytoplasm of living cells and tracking the spontaneous displacement of the particles at high spatial resolution. The trajectories of the cytoplasm-embedded particles are transformed into mean-squared displacements, which are subsequently transformed into frequency-dependent viscoelastic moduli and time-dependent creep compliance of the cytoplasm. This method allows for the study of a wide range of cellular conditions, including cells inside a 3D matrix, cell subjected to shear flows and biochemical stimuli, and cells in a live animal. Ballistic injection lasts <1 min and is followed by overnight incubation. Multiple particle tracking for one cell lasts <1 min. Forty cells can be examined in <1 h.
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Nuclear Lamin A/C Deficiency Induces Defects in Cell Mechanics, Polarization, and Migration ☆
Biophysical Journal, 2007Co-Authors: Christopher M Hale, Yiider Tseng, Porntula Panorchan, Shyam B Khatau, Jerry P. George, Colin L. Stewart, Didier Hodzic, Denis WirtzAbstract:Lamin A/C is a major constituent of the nuclear lamina, a thin filamentous protein layer that lies beneath the nuclear envelope. Here we show that lamin A/C deficiency in mouse embryonic fibroblasts (Lmna−/− MEFs) diminishes the ability of these cells to polarize at the edge of a wound and significantly reduces cell migration speed into the wound. Moreover, lamin A/C deficiency induces significant separation of the microtubule organizing center (MTOC) from the nuclear envelope. Investigations using ballistic intracellular Nanorheology reveal that lamin A/C deficiency also dramatically affects the micromechanical properties of the cytoplasm. Both the elasticity (stretchiness) and the viscosity (propensity of a material to flow) of the cytoplasm in Lmna−/− MEFs are significantly reduced. Disassembly of either the actin filament or microtubule networks in Lmna+/+ MEFs results in decrease of cytoplasmic elasticity and viscosity down to levels found in Lmna−/− MEFs. Together these results show that both the mechanical properties of the cytoskeleton and cytoskeleton-based processes, including cell motility, coupled MTOC and nucleus dynamics, and cell polarization, depend critically on the integrity of the nuclear lamina, which suggest the existence of a functional mechanical connection between the nucleus and the cytoskeleton. These results also suggest that cell polarization during cell migration requires tight mechanical coupling between MTOC and nucleus, which is mediated by lamin A/C.
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probing cellular mechanical responses to stimuli using ballistic intracellular Nanorheology
Methods in Cell Biology, 2007Co-Authors: Porntula Panorchan, Yiider Tseng, Denis Wirtz, Brian R Daniels, Thomas P KoleAbstract:Abstract We describe a new method to measure the local and global micromechanical properties of the cytoplasm of single living cells in their physiological milieu and subjected to external stimuli. By tracking spontaneous, Brownian movements of individual nanoparticles of diameter ≥100 nm distributed within the cell with high spatial and temporal resolutions, the local viscoelastic properties of the intracellular milieu can be measured in different locations within the cell. The amplitude and the time‐dependence of the mean‐squared displacement of each nanoparticle directly reflect the elasticity and the viscosity of the cytoplasm in the vicinity of the nanoparticle. In our previous versions of particle tracking, we delivered nanoparticles via microinjection, which limited the number of cells amenable to measurement, rendering our technique incompatible with high‐throughput experiments. Here we introduce ballistic injection to effectively deliver a large number of nanoparticles to a large number of cells simultaneously. When coupled with multiple particle tracking, this new method—ballistic intracellular Nanorheology (BIN)—makes it now possible to probe the viscoelastic properties of cells in high‐throughput experiments, which require large quantities of injected cells for seeding in various conditions. For instance, BIN allows us to probe an ensemble of cells embedded deeply inside a three‐dimensional extracellular matrix or as a monolayer of cells subjected to shear flows.
Steve Granick - One of the best experts on this subject based on the ideXlab platform.
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An integrated platform for surface forces measurements and fluorescence correlation spectroscopy
Review of Scientific Instruments, 2003Co-Authors: Ashis Mukhopadhyay, Jiang Zhao, Steve GranickAbstract:We describe an apparatus to measure the diffusion of dilute fluorophores in molecularly thin liquid films within a surface forces apparatus (SFA). The design is a significant modification of the traditional SFA in that it allows one to combine Nanorheology with the single-molecule sensitive technique of fluorescence correlation spectroscopy. The primary enabling idea was to place a miniaturized SFA onto the stage of an optical microscope equipped with a long working distance objective and illuminated by a femtosecond laser. A secondary enabling idea was that the silver coating on the backside of mica, normally used in the traditional SFA design for interferometric measurements of the film thickness, was replaced by multilayer dielectric coatings that allowed simultaneous interferometry and fluorescence measurements in different regions of the optical spectrum. To illustrate the utility of this instrument, we contrast the translational diffusion of rhodamine dye molecules (in the solvent, 1,2-propane diol)...
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Nanorheology of aqueous polyethylene glycol peg
Macromolecules, 2002Co-Authors: Xueyan Zhang, Steve GranickAbstract:Static and dynamic surface interactions in deionized water were studied between poly(ethylene glycol) (PEG) and an opposed layer of either the same PEG or a highly charged cationic polymer, quaternized polyvinylpyridine (QPVP). The PEG, molecular weight 5000 g mol-1, was end-attached to hydrophobized mica by hydrophobic-driven adsorption of the lipid portion (distearoyl-phosphatidylethanolamine) of PEG-lipid diblock copolymers. The QPVP homopolymer, 98% quaternized and molecular weight 39,000 g mol-1, was allowed to adsorb statistically onto mica. Within the scatter of the data the force−distance curves could be fit equally well by the Alexander-de Gennes expression for brush-brush interactions or by exponential decay (decay length 4 nm). However, at every film thickness, the shear modulus of the PEG-PEG interface was less than that of PEG-QPVP by an order of magnitude. When the layers were compressed strongly, they remained demonstrably fluid, even in the most strongly compressed state, in the sense that...
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micro and Nanorheology
Current Opinion in Colloid and Interface Science, 2001Co-Authors: Ashis Mukhopadhyay, Steve GranickAbstract:‘Microrheology’, the determination of viscoelastic properties of soft media from the observed motion of microscopic-sized tracer particles, has undergone a recent surge of development because it allows access to an unprecedented range of frequency response with unprecedented spatial resolution. Several complementary techniques have been developed, but discrepancies have been found among different experiments especially in complex systems, and the validity of interpretation is under debate. ‘Nanorheology’ after explicit confinement of samples to variable thickness, 1 nm to 1 m, is also enjoying rapid development, particularly Nanorheology integrated with spectroscopy. Developments, limitations, and opportunities are discussed. 2001 Elsevier Science Ltd. All rights reserved.
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Micro- and Nanorheology
Current Opinion in Colloid and Interface Science, 2001Co-Authors: Ashis Mukhopadhyay, Steve GranickAbstract:Abstract ‘Microrheology’, the determination of viscoelastic properties of soft media from the observed motion of microscopic-sized tracer particles, has undergone a recent surge of development because it allows access to an unprecedented range of frequency response with unprecedented spatial resolution. Several complementary techniques have been developed, but discrepancies have been found among different experiments especially in complex systems, and the validity of interpretation is under debate. ‘Nanorheology’ after explicit confinement of samples to variable thickness, 1 nm to 1 μm, is also enjoying rapid development, particularly Nanorheology integrated with spectroscopy. Developments, limitations, and opportunities are discussed.
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exploring the friction modifier phenomenon Nanorheology of n alkane chains with polar terminus dissolved in n alkane solvent
Tribology Letters, 1999Co-Authors: Hiroko Ohtani, Marina Ruths, Michael L. Greenfield, Steve GranickAbstract:Dilute solutions of two polar end-functionalized linear alkanes (1-hexadecylamine and palmitic acid), each dissolved in tetradecane, were confined between two mica surfaces and investigated using a surface forces apparatus modified to study shear Nanorheology. These two solutions showed similar nanorheological properties that differed from those observed for pure n-alkanes. In static measurements, a “hard wall”, rather than an oscillatory force, was observed as a function of film thickness. The polar alkane component formed a weakly adsorbed single layer at each mica surface, disrupting the layered structures found in neat n-tetradecane. In dynamic experiments at low shear amplitude, the storage modulus G0 exceeded the loss modulus G00 at low frequencies; above some characteristic frequencies G00 increased such that G 0 G 00 , indicating significantly more energy loss through viscous modes at higher frequency. When the amplitude was varied at fixed frequency, no stick‐slip was observed and the limiting value of the shear stress at high effective shear rate was an order of magnitude less than for unfunctionalized n-alkanes at similar loads. Together, these results show that the addition of a small amount of polar alkane component, by disrupting the layered structures that would have been formed in the neat n-alkane, is effective in suppressing static friction and reducing kinetic friction in the boundary lubrication regime.
Pei-hsun Wu - One of the best experts on this subject based on the ideXlab platform.
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mechanics
Nat Protoc., 2015Co-Authors: Pei-hsun Wu, C. Hale, Wei-chiang Chen, Jerry S.h. Lee, Yiider Tseng, Daniel WirtzAbstract:High-throughput ballistic injection Nanorheology is a method for the quantitative study of cell mechanics. Cell mechanics are measured by ballistic injection of submicron particles into the cytoplasm of living cells and tracking the spontaneous displacement of the particles at high spatial resolution. The trajectories of the cytoplasm-embedded particles are transformed into mean-squared displacements, which are subsequently transformed into frequency-dependent viscoelastic moduli and time-dependent creep compliance of the cytoplasm. This method allows for the study of a wide range of cellular conditions, including cells inside a 3D matrix, cell subjected to shear flows and biochemical stimuli, and cells in a live animal. Ballistic injection lasts < 1 min and is followed by overnight incubation. Multiple particle tracking for one cell lasts < 1 min. Forty cells can be examined in < 1 h.
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High-throughput ballistic injection Nanorheology to measure cell mechanics
Nature Protocols, 2012Co-Authors: Pei-hsun Wu, Wei-chiang Chen, Yiider Tseng, Christopher M Hale, Denis WirtzAbstract:High-throughput ballistic injection Nanorheology is a method for the quantitative study of cell mechanics. Cell mechanics are measured by ballistic injection of submicron particles into the cytoplasm of living cells and tracking the spontaneous displacement of the particles at high spatial resolution. The trajectories of the cytoplasm-embedded particles are transformed into mean-squared displacements, which are subsequently transformed into frequency-dependent viscoelastic moduli and time-dependent creep compliance of the cytoplasm. This method allows for the study of a wide range of cellular conditions, including cells inside a 3D matrix, cell subjected to shear flows and biochemical stimuli, and cells in a live animal. Ballistic injection lasts
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high throughput ballistic injection Nanorheology to measure cell mechanics
Nature Protocols, 2012Co-Authors: Pei-hsun Wu, Wei-chiang Chen, Yiider Tseng, Christopher M Hale, Denis WirtzAbstract:High-throughput ballistic injection Nanorheology is a method for the quantitative study of cell mechanics. Cell mechanics are measured by ballistic injection of submicron particles into the cytoplasm of living cells and tracking the spontaneous displacement of the particles at high spatial resolution. The trajectories of the cytoplasm-embedded particles are transformed into mean-squared displacements, which are subsequently transformed into frequency-dependent viscoelastic moduli and time-dependent creep compliance of the cytoplasm. This method allows for the study of a wide range of cellular conditions, including cells inside a 3D matrix, cell subjected to shear flows and biochemical stimuli, and cells in a live animal. Ballistic injection lasts <1 min and is followed by overnight incubation. Multiple particle tracking for one cell lasts <1 min. Forty cells can be examined in <1 h.
Alex J Levine - One of the best experts on this subject based on the ideXlab platform.
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Nanorheology of viscoelastic shells application to viral capsids
Biophysical Journal, 2009Co-Authors: Tatiana Kuriabova, Alex J LevineAbstract:We study the microrheology of nanoparticle shells [A.D. Dinsmore et al., Science 298, 1006 (2002)] and viral capsids [I.L. Ivanovska et al., Proc. Natl. Acad. Sci. U.S.A. 101, 7600 (2004)] by computing the mechanical response function and thermal fluctuation spectrum of a viscoelastic spherical shell that is permeable to the surrounding solvent.We determine analytically the coupled dynamics of bending and compression modes of the viscoelastic shell coupled to solvent flows inside, outside, and through the porous viral capsid. From this calculation, we identify fundamental length and time scales in the system, and compute the finite-frequency response of the shell to pinching forces applied at antipodal points on it.This calculation determines the mechanical response of a viral capsid to an AFM-based nanoindentation study. Using these calculations, one can interpret such studies in terms of elastic and dissipative response of the viral capsid to bending and compressional deformations and thereby gain new information regarding the internal deformations of individual capsomers under stress, providing insight into their intermolecular and intramolecular interactions. As an example we study the mechanical effect of a simple allosteric transition in the capsomers.The frequency-dependent mechanics of complex, viscoelastic and possibly porous spherical shells is not only application to viruses, but also may lead to new measurements of colloidosomes, nanoparticle shells, and lipid vesicles including those that contain pore-forming proteins.
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Nanorheology of viscoelastic shells applications to viral capsids
Physical Review E, 2008Co-Authors: Tatiana Kuriabova, Alex J LevineAbstract:We study the microrheology of nanoparticle shells [A. D. Dinsmore et al., Science 298, 1006 (2002)] and viral capsids [I. L. Ivanovska et al., Proc. Natl. Acad. Sci. U.S.A. 101, 7600 (2004)] by computing the mechanical response function and thermal fluctuation spectrum of a viscoelastic spherical shell that is permeable to the surrounding solvent. We determine analytically the damped dynamics of bend and compression modes of the shell coupled to the solvent both inside and outside the sphere in the zero Reynolds number limit. We identify fundamental length and time scales in the system, and compute the thermal correlation function of displacements of antipodal points on the sphere and the mechanical response to pinching forces applied at these points. We describe how such a frequency-dependent antipodal correlation and/or response function, which should be measurable in new AFM-based microrheology experiments, can probe the viscoelasticity of these synthetic and biological shells constructed of nanoparticles.
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Nanorheology of viscoelastic shells: applications to viral capsids.
Physical review. E Statistical nonlinear and soft matter physics, 2008Co-Authors: Tatiana Kuriabova, Alex J LevineAbstract:We study the microrheology of nanoparticle shells [A. D. Dinsmore, Science 298, 1006 (2002)] and viral capsids [I. L. Ivanovska, Proc. Natl. Acad. Sci. U.S.A. 101, 7600 (2004)] by computing the mechanical response function and thermal fluctuation spectrum of a viscoelastic spherical shell that is permeable to the surrounding solvent. We determine analytically the damped dynamics of bend and compression modes of the shell coupled to the solvent both inside and outside the sphere in the zero Reynolds number limit. We identify fundamental length and time scales in the system, and compute the thermal correlation function of displacements of antipodal points on the sphere and the mechanical response to pinching forces applied at these points. We describe how such a frequency-dependent antipodal correlation and/or response function, which should be measurable in new AFM-based microrheology experiments, can probe the viscoelasticity of these synthetic and biological shells constructed of nanoparticles.
