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Conboy JP, Istúriz Petitjean I, van der Net A, Koenderink GH. How cytoskeletal crosstalk makes cells move: Bridging cell-free and cell studies. BIOPHYSICS REVIEWS 2024; 5:021307. [PMID: 38840976 PMCID: PMC11151447 DOI: 10.1063/5.0198119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 05/13/2024] [Indexed: 06/07/2024]
Abstract
Cell migration is a fundamental process for life and is highly dependent on the dynamical and mechanical properties of the cytoskeleton. Intensive physical and biochemical crosstalk among actin, microtubules, and intermediate filaments ensures their coordination to facilitate and enable migration. In this review, we discuss the different mechanical aspects that govern cell migration and provide, for each mechanical aspect, a novel perspective by juxtaposing two complementary approaches to the biophysical study of cytoskeletal crosstalk: live-cell studies (often referred to as top-down studies) and cell-free studies (often referred to as bottom-up studies). We summarize the main findings from both experimental approaches, and we provide our perspective on bridging the two perspectives to address the open questions of how cytoskeletal crosstalk governs cell migration and makes cells move.
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Affiliation(s)
- James P. Conboy
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Irene Istúriz Petitjean
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Anouk van der Net
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Gijsje H. Koenderink
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
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2
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Kwon Y, Singh S, Rodriguez D, Chau AL, Pitenis AA, De Tomaso AW, Valentine MT. Mechanical resilience of the sessile tunicate Botryllus schlosseri. J Exp Biol 2023; 226:jeb245124. [PMID: 37929758 PMCID: PMC10753489 DOI: 10.1242/jeb.245124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 10/23/2023] [Indexed: 11/07/2023]
Abstract
We demonstrate that the sessile tunicate Botryllus schlosseri is remarkably resilient to applied loads by attaching the animals to an extensile substrate subjected to quasistatic equiradial loads. Animals can withstand radial extension of the substrate to strain values as high as 20% before they spontaneously detach. In the small to moderate strain regime, we found no relationship between the dynamic size of the external vascular bed and the magnitude of applied stretch, despite known force sensitivities of the vascular tissue at the cellular level. We attribute this resilience to the presence and mechanical properties of the tunic, the cellulose-enriched gel-like substance that encases the animal bodies and surrounding vasculature.
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Affiliation(s)
- Younghoon Kwon
- Department of Mechanical Engineering, University of California, Santa Barbara, Santa Barbara, CA 93117, USA
| | - Shambhavi Singh
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93117, USA
| | - Delany Rodriguez
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93117, USA
| | - Allison L. Chau
- Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93117, USA
| | - Angela A. Pitenis
- Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93117, USA
| | - Anthony W. De Tomaso
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93117, USA
| | - Megan T. Valentine
- Department of Mechanical Engineering, University of California, Santa Barbara, Santa Barbara, CA 93117, USA
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3
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Lorenz C, Köster S. Multiscale architecture: Mechanics of composite cytoskeletal networks. BIOPHYSICS REVIEWS 2022; 3:031304. [PMID: 38505277 PMCID: PMC10903411 DOI: 10.1063/5.0099405] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 07/27/2022] [Indexed: 03/21/2024]
Abstract
Different types of biological cells respond differently to mechanical stresses, and these responses are mainly governed by the cytoskeleton. The main components of this biopolymer network are actin filaments, microtubules, and intermediate filaments, whose mechanical and dynamic properties are highly distinct, thus opening up a large mechanical parameter space. Aside from experiments on whole, living cells, "bottom-up" approaches, utilizing purified, reconstituted protein systems, tremendously help to shed light on the complex mechanics of cytoskeletal networks. Such experiments are relevant in at least three aspects: (i) from a fundamental point of view, cytoskeletal networks provide a perfect model system for polymer physics; (ii) in materials science and "synthetic cell" approaches, one goal is to fully understand properties of cellular materials and reconstitute them in synthetic systems; (iii) many diseases are associated with cell mechanics, so a thorough understanding of the underlying phenomena may help solving pressing biomedical questions. In this review, we discuss the work on networks consisting of one, two, or all three types of filaments, entangled or cross-linked, and consider active elements such as molecular motors and dynamically growing filaments. Interestingly, tuning the interactions among the different filament types results in emergent network properties. We discuss current experimental challenges, such as the comparability of different studies, and recent methodological advances concerning the quantification of attractive forces between filaments and their influence on network mechanics.
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Affiliation(s)
- C. Lorenz
- Institute for X-Ray Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - S. Köster
- Author to whom correspondence should be addressed:
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4
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Mao Y, Nielsen P, Ali J. Passive and Active Microrheology for Biomedical Systems. Front Bioeng Biotechnol 2022; 10:916354. [PMID: 35866030 PMCID: PMC9294381 DOI: 10.3389/fbioe.2022.916354] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Accepted: 06/08/2022] [Indexed: 12/12/2022] Open
Abstract
Microrheology encompasses a range of methods to measure the mechanical properties of soft materials. By characterizing the motion of embedded microscopic particles, microrheology extends the probing length scale and frequency range of conventional bulk rheology. Microrheology can be characterized into either passive or active methods based on the driving force exerted on probe particles. Tracer particles are driven by thermal energy in passive methods, applying minimal deformation to the assessed medium. In active techniques, particles are manipulated by an external force, most commonly produced through optical and magnetic fields. Small-scale rheology holds significant advantages over conventional bulk rheology, such as eliminating the need for large sample sizes, the ability to probe fragile materials non-destructively, and a wider probing frequency range. More importantly, some microrheological techniques can obtain spatiotemporal information of local microenvironments and accurately describe the heterogeneity of structurally complex fluids. Recently, there has been significant growth in using these minimally invasive techniques to investigate a wide range of biomedical systems both in vitro and in vivo. Here, we review the latest applications and advancements of microrheology in mammalian cells, tissues, and biofluids and discuss the current challenges and potential future advances on the horizon.
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Affiliation(s)
- Yating Mao
- Department of Chemical and Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL, United States
- National High Magnetic Field Laboratory, Tallahassee, FL, United States
| | - Paige Nielsen
- Department of Chemical and Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL, United States
- National High Magnetic Field Laboratory, Tallahassee, FL, United States
| | - Jamel Ali
- Department of Chemical and Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL, United States
- National High Magnetic Field Laboratory, Tallahassee, FL, United States
- *Correspondence: Jamel Ali,
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5
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Sheung JY, Achiriloaie DH, Currie C, Peddireddy K, Xie A, Simon-Parker J, Lee G, Rust MJ, Das M, Ross JL, Robertson-Anderson RM. Motor-Driven Restructuring of Cytoskeleton Composites Leads to Tunable Time-Varying Elasticity. ACS Macro Lett 2021; 10:1151-1158. [PMID: 35549081 DOI: 10.1021/acsmacrolett.1c00500] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The composite cytoskeleton, comprising interacting networks of semiflexible actin and rigid microtubules, generates forces and restructures by using motor proteins such as myosins to enable key processes including cell motility and mitosis. Yet, how motor-driven activity alters the mechanics of cytoskeleton composites remains an open challenge. Here, we perform optical tweezers microrheology and confocal imaging of composites with varying actin-tubulin molar percentages (25-75, 50-50, and 75-25), driven by light-activated myosin II motors, to show that motor activity increases the elastic plateau modulus by over 2 orders of magnitude by active restructuring of both actin and microtubules that persists for hours after motor activation has ceased. Nonlinear microrheology measurements show that motor-driven restructuring increases the force response and stiffness and suppresses actin bending. The 50-50 composite exhibits the most dramatic mechanical response to motor activity due to the synergistic effects of added stiffness from the microtubules and sufficient motor substrate for pronounced activity.
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Affiliation(s)
- Janet Y. Sheung
- W. M. Keck Science Department, Scripps College, Pitzer College, and Claremont McKenna College, 925 N. Mills Ave., Claremont, California 91711, United States
| | - Daisy H. Achiriloaie
- W. M. Keck Science Department, Scripps College, Pitzer College, and Claremont McKenna College, 925 N. Mills Ave., Claremont, California 91711, United States
| | - Christopher Currie
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, California 92110, United States
| | - Karthik Peddireddy
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, California 92110, United States
| | - Aaron Xie
- W. M. Keck Science Department, Scripps College, Pitzer College, and Claremont McKenna College, 925 N. Mills Ave., Claremont, California 91711, United States
| | - Jessalyn Simon-Parker
- W. M. Keck Science Department, Scripps College, Pitzer College, and Claremont McKenna College, 925 N. Mills Ave., Claremont, California 91711, United States
| | - Gloria Lee
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, California 92110, United States
| | - Michael J. Rust
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois 60637, United States
| | - Moumita Das
- School of Physics and Astronomy, Rochester Institute of Technology, Rochester, New York 14623, United States
| | - Jennifer L. Ross
- Department of Physics, Syracuse University, Syracuse, New York 13244, United States
| | - Rae M. Robertson-Anderson
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, California 92110, United States
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6
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Aermes C, Hayn A, Fischer T, Mierke CT. Cell mechanical properties of human breast carcinoma cells depend on temperature. Sci Rep 2021; 11:10771. [PMID: 34031462 PMCID: PMC8144563 DOI: 10.1038/s41598-021-90173-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 04/30/2021] [Indexed: 12/21/2022] Open
Abstract
The knowledge of cell mechanics is required to understand cellular processes and functions, such as the movement of cells, and the development of tissue engineering in cancer therapy. Cell mechanical properties depend on a variety of factors, such as cellular environments, and may also rely on external factors, such as the ambient temperature. The impact of temperature on cell mechanics is not clearly understood. To explore the effect of temperature on cell mechanics, we employed magnetic tweezers to apply a force of 1 nN to 4.5 µm superparamagnetic beads. The beads were coated with fibronectin and coupled to human epithelial breast cancer cells, in particular MCF-7 and MDA-MB-231 cells. Cells were measured in a temperature range between 25 and 45 °C. The creep response of both cell types followed a weak power law. At all temperatures, the MDA-MB-231 cells were pronouncedly softer compared to the MCF-7 cells, whereas their fluidity was increased. However, with increasing temperature, the cells became significantly softer and more fluid. Since mechanical properties are manifested in the cell's cytoskeletal structure and the paramagnetic beads are coupled through cell surface receptors linked to cytoskeletal structures, such as actin and myosin filaments as well as microtubules, the cells were probed with pharmacological drugs impacting the actin filament polymerization, such as Latrunculin A, the myosin filaments, such as Blebbistatin, and the microtubules, such as Demecolcine, during the magnetic tweezer measurements in the specific temperature range. Irrespective of pharmacological interventions, the creep response of cells followed a weak power law at all temperatures. Inhibition of the actin polymerization resulted in increased softness in both cell types and decreased fluidity exclusively in MDA-MB-231 cells. Blebbistatin had an effect on the compliance of MDA-MB-231 cells at lower temperatures, which was minor on the compliance MCF-7 cells. Microtubule inhibition affected the fluidity of MCF-7 cells but did not have a significant effect on the compliance of MCF-7 and MDA-MB-231 cells. In summary, with increasing temperature, the cells became significant softer with specific differences between the investigated drugs and cell lines.
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Affiliation(s)
- Christian Aermes
- Biological Physics Division, Faculty of Physics and Earth Science, Peter Debye Institute of Soft Matter Physics, University of Leipzig, Linnéstr. 5, 04103, Leipzig, Germany
| | - Alexander Hayn
- Biological Physics Division, Faculty of Physics and Earth Science, Peter Debye Institute of Soft Matter Physics, University of Leipzig, Linnéstr. 5, 04103, Leipzig, Germany
| | - Tony Fischer
- Biological Physics Division, Faculty of Physics and Earth Science, Peter Debye Institute of Soft Matter Physics, University of Leipzig, Linnéstr. 5, 04103, Leipzig, Germany
| | - Claudia Tanja Mierke
- Biological Physics Division, Faculty of Physics and Earth Science, Peter Debye Institute of Soft Matter Physics, University of Leipzig, Linnéstr. 5, 04103, Leipzig, Germany.
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7
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Anderson SJ, Garamella J, Adalbert S, McGorty RJ, Robertson-Anderson RM. Subtle changes in crosslinking drive diverse anomalous transport characteristics in actin-microtubule networks. SOFT MATTER 2021; 17:4375-4385. [PMID: 33908593 PMCID: PMC8189643 DOI: 10.1039/d1sm00093d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Anomalous diffusion in crowded and complex environments is widely studied due to its importance in intracellular transport, fluid rheology and materials engineering. Specifically, diffusion through the cytoskeleton, a network comprised of semiflexible actin filaments and rigid microtubules that interact both sterically and via crosslinking, plays a principal role in viral infection, vesicle transport and targeted drug delivery. Here, we elucidate the impact of crosslinking on particle diffusion in composites of actin and microtubules with actin-actin, microtubule-microtubule and actin-microtubule crosslinking. We analyze a suite of transport metrics by coupling single-particle tracking and differential dynamic microscopy. Using these complementary techniques, we find that particles display non-Gaussian and non-ergodic subdiffusion that is markedly enhanced by cytoskeletal crosslinking, which we attribute to suppressed microtubule mobility. However, the extent to which transport deviates from normal Brownian diffusion depends strongly on the crosslinking motif - with actin-microtubule crosslinking inducing the most pronounced anomalous characteristics. Our results reveal that subtle changes to actin-microtubule interactions can have complex impacts on particle diffusion in cytoskeleton composites, and suggest that a combination of reduced filament mobility and more variance in actin mobilities leads to more strongly anomalous particle transport.
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Affiliation(s)
- S J Anderson
- Department of Physics & Biophysics, University of San Diego, San Diego, CA 92110, USA.
| | - J Garamella
- Department of Physics & Biophysics, University of San Diego, San Diego, CA 92110, USA.
| | - S Adalbert
- Department of Physics & Biophysics, University of San Diego, San Diego, CA 92110, USA.
| | - R J McGorty
- Department of Physics & Biophysics, University of San Diego, San Diego, CA 92110, USA.
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8
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Asgharzadeh P, Birkhold AI, Trivedi Z, Özdemir B, Reski R, Röhrle O. A NanoFE simulation-based surrogate machine learning model to predict mechanical functionality of protein networks from live confocal imaging. Comput Struct Biotechnol J 2020; 18:2774-2788. [PMID: 33101614 PMCID: PMC7559262 DOI: 10.1016/j.csbj.2020.09.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 09/12/2020] [Accepted: 09/13/2020] [Indexed: 02/07/2023] Open
Abstract
Sub-cellular mechanics plays a crucial role in a variety of biological functions and dysfunctions. Due to the strong structure-function relationship in cytoskeletal protein networks, light can be shed on their mechanical functionality by investigating their structures. Here, we present a data-driven approach employing a combination of confocal live imaging of fluorescent tagged protein networks, in silico mechanical experiments and machine learning to investigate this relationship. Our designed image processing and nanoFE mechanical simulation framework resolves the structure and mechanical behaviour of cytoskeletal networks and the developed gradient boosting surrogate models linking network structure to its functionality. In this study, for the first time, we perform mechanical simulations of Filamentous Temperature Sensitive Z (FtsZ) complex protein networks with realistic network geometry depicting its skeletal functionality inside organelles (here, chloroplasts) of the moss Physcomitrella patens. Training on synthetically produced simulation data enables predicting the mechanical characteristics of FtsZ network purely based on its structural features (R2⩾0.93), therefore allowing to extract structural principles enabling specific mechanical traits of FtsZ, such as load bearing and resistance to buckling failure in case of large network deformation.
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Affiliation(s)
- Pouyan Asgharzadeh
- Institute for Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Stuttgart, Germany.,Stuttgart Center for Simulation Science (SC SimTech), Stuttgart, Germany
| | - Annette I Birkhold
- Institute for Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Stuttgart, Germany.,Stuttgart Center for Simulation Science (SC SimTech), Stuttgart, Germany
| | - Zubin Trivedi
- Institute for Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Stuttgart, Germany
| | - Bugra Özdemir
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, Freiburg, Germany
| | - Ralf Reski
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, Freiburg, Germany.,Cluster of Excellence livMatS @ FIT - Freiburg Centre for Interactive Materials and Bioinspired Technologies, Freiburg, Germany
| | - Oliver Röhrle
- Institute for Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Stuttgart, Germany.,Stuttgart Center for Simulation Science (SC SimTech), Stuttgart, Germany
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9
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Wulstein DM, Regan KE, Garamella J, McGorty RJ, Robertson-Anderson RM. Topology-dependent anomalous dynamics of ring and linear DNA are sensitive to cytoskeleton crosslinking. SCIENCE ADVANCES 2019; 5:eaay5912. [PMID: 31853502 PMCID: PMC6910835 DOI: 10.1126/sciadv.aay5912] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 10/18/2019] [Indexed: 05/21/2023]
Abstract
Cytoskeletal crowding plays a key role in the diffusion of DNA molecules through the cell, acting as a barrier to effective intracellular transport and conformational stability required for processes such as transfection, viral infection, and gene therapy. Here, we elucidate the transport properties and conformational dynamics of linear and ring DNA molecules diffusing through entangled and crosslinked composite networks of actin and microtubules. We couple single-molecule conformational tracking with differential dynamic microscopy to reveal that ring and linear DNA exhibit unexpectedly distinct transport properties that are influenced differently by cytoskeleton crosslinking. Ring DNA coils are swollen and undergo heterogeneous and biphasic subdiffusion that is hindered by crosslinking. Conversely, crosslinking actually facilitates the single-mode subdiffusion that compacted linear chains exhibit. Our collective results demonstrate that transient threading by cytoskeleton filaments plays a key role in the dynamics of ring DNA, whereas the mobility of the cytoskeleton dictates transport of linear DNA.
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Affiliation(s)
| | | | - Jonathan Garamella
- Department of Physics and Biophysics, University of San Diego, San Diego, CA 92110, USA
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10
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Francis ML, Ricketts SN, Farhadi L, Rust MJ, Das M, Ross JL, Robertson-Anderson RM. Non-monotonic dependence of stiffness on actin crosslinking in cytoskeleton composites. SOFT MATTER 2019; 15:9056-9065. [PMID: 31647488 PMCID: PMC6854303 DOI: 10.1039/c9sm01550g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The cytoskeleton is able to precisely tune its structure and mechanics through interactions between semiflexible actin filaments, rigid microtubules and a suite of crosslinker proteins. However, the role that each of these components, as well as the interactions between them, plays in the dynamics of the composite cytoskeleton remains an open question. Here, we use optical tweezers microrheology and fluorescence confocal microscopy to reveal the surprising ways in which actin crosslinking tunes the viscoelasticity and mobility of actin-microtubule composites from steady-state to the highly nonlinear regime. While previous studies have shown that increasing crosslinking in actin networks increases elasticity and stiffness, we instead find that composite stiffness displays a striking non-monotonic dependence on actin crosslinking - first increasing then decreasing to a response similar to or even lower than un-linked composites. We further show that actin crosslinking has an unexpectedly strong impact on the mobility of microtubules; and it is in fact the microtubule mobility - dictated by crosslinker-driven rearrangements of actin filaments - that controls composite stiffness. This result is at odds with conventional thought that actin mobility drives cytoskeleton mechanics. More generally, our results demonstrate that - when crosslinking composite materials to confer strength and resilience - more is not always better.
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Affiliation(s)
- Madison L Francis
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, CA 92110, USA.
| | - Shea N Ricketts
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, CA 92110, USA.
| | - Leila Farhadi
- Department of Physics, University of Massachusetts, Amherst, 666 N. Pleasant St., Amherst, MA 01003, USA
| | - Michael J Rust
- Department of Molecular Genetics and Cell Biology, University of Chicago, 900 E 57th St, Chicago, IL 60637, USA
| | - Moumita Das
- School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623, USA
| | - Jennifer L Ross
- Department of Physics, University of Massachusetts, Amherst, 666 N. Pleasant St., Amherst, MA 01003, USA
| | - Rae M Robertson-Anderson
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, CA 92110, USA.
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11
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Ricketts SN, Francis ML, Farhadi L, Rust MJ, Das M, Ross JL, Robertson-Anderson RM. Varying crosslinking motifs drive the mesoscale mechanics of actin-microtubule composites. Sci Rep 2019; 9:12831. [PMID: 31492892 PMCID: PMC6731314 DOI: 10.1038/s41598-019-49236-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Accepted: 08/21/2019] [Indexed: 12/15/2022] Open
Abstract
The cytoskeleton precisely tunes its mechanics by altering interactions between semiflexible actin filaments, rigid microtubules, and crosslinking proteins. We use optical tweezers microrheology and confocal microscopy to characterize how varying crosslinking motifs impact the mesoscale mechanics and mobility of actin-microtubule composites. We show that, upon subtle changes in crosslinking patterns, composites can exhibit two distinct classes of force response - primarily elastic versus more viscous. For example, a composite in which actin and microtubules are crosslinked to each other but not to themselves is markedly more elastic than one in which both filaments are independently crosslinked. Notably, this distinction only emerges at mesoscopic scales in response to nonlinear forcing, whereas varying crosslinking motifs have little impact on the microscale mechanics and mobility. Our unexpected scale-dependent results not only inform the physics underlying key cytoskeleton processes and structures, but, more generally, provide valuable perspective to materials engineering endeavors focused on polymer composites.
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Affiliation(s)
- Shea N Ricketts
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, CA, 92110, USA
| | - Madison L Francis
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, CA, 92110, USA
| | - Leila Farhadi
- Department of Physics, University of Massachusetts, Amherst, 666N. Pleasant St., Amherst, MA, 01003, USA
| | - Michael J Rust
- Department of Molecular Genetics and Cell Biology, University of Chicago, 900 E 57th St., Chicago, IL, 60637, USA
| | - Moumita Das
- School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY, 14623, USA
| | - Jennifer L Ross
- Department of Physics, University of Massachusetts, Amherst, 666N. Pleasant St., Amherst, MA, 01003, USA
| | - Rae M Robertson-Anderson
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, CA, 92110, USA.
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12
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Ricketts SN, Ross JL, Robertson-Anderson RM. Co-Entangled Actin-Microtubule Composites Exhibit Tunable Stiffness and Power-Law Stress Relaxation. Biophys J 2018; 115:1055-1067. [PMID: 30177441 PMCID: PMC6139891 DOI: 10.1016/j.bpj.2018.08.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 07/19/2018] [Accepted: 08/06/2018] [Indexed: 12/25/2022] Open
Abstract
We use optical tweezers microrheology and fluorescence microscopy to characterize the nonlinear mesoscale mechanics and mobility of in vitro co-entangled actin-microtubule composites. We create a suite of randomly oriented, well-mixed networks of actin and microtubules by co-polymerizing varying ratios of actin and tubulin in situ. To perturb each composite far from equilibrium, we use optical tweezers to displace an embedded microsphere a distance greater than the lengths of the filaments at a speed much faster than their intrinsic relaxation rates. We simultaneously measure the force the filaments exert on the bead and the subsequent force relaxation. We find that the presence of a large fraction of microtubules (>0.7) is needed to substantially increase the measured force, which is accompanied by large heterogeneities in force response. Actin minimizes these heterogeneities by reducing the mesh size of the composites and supporting microtubules against buckling. Composites also undergo a sharp transition from strain softening to stiffening when the fraction of microtubules (ϕT) exceeds 0.5, which we show arises from faster poroelastic relaxation and suppressed actin bending fluctuations. The force after bead displacement relaxes via power-law decay after an initial period of minimal relaxation. The short-time relaxation profiles (t < 0.06 s) arise from poroelastic and bending contributions, whereas the long-time power-law relaxation is indicative of filaments reptating out of deformed entanglement constraints. The scaling exponents for the long-time relaxation exhibit a nonmonotonic dependence on ϕT, reaching a maximum for equimolar composites (ϕT = 0.5), suggesting that reptation is fastest in ϕT = 0.5 composites. Corresponding mobility measurements of steady-state actin and microtubules show that both filaments are indeed the most mobile in ϕT = 0.5 composites. This nonmonotonic dependence of mobility on ϕT demonstrates the important interplay between mesh size and filament rigidity in polymer networks and highlights the surprising emergent properties that can arise in composites.
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Affiliation(s)
- Shea N Ricketts
- Department of Physics and Biophysics, University of San Diego, San Diego, California
| | - Jennifer L Ross
- Department of Physics, University of Massachusetts Amherst, Amherst, Massachusetts
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13
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Rajagopal V, Holmes WR, Lee PVS. Computational modeling of single-cell mechanics and cytoskeletal mechanobiology. WILEY INTERDISCIPLINARY REVIEWS. SYSTEMS BIOLOGY AND MEDICINE 2018; 10:e1407. [PMID: 29195023 PMCID: PMC5836888 DOI: 10.1002/wsbm.1407] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 08/19/2017] [Accepted: 09/07/2017] [Indexed: 01/10/2023]
Abstract
Cellular cytoskeletal mechanics plays a major role in many aspects of human health from organ development to wound healing, tissue homeostasis and cancer metastasis. We summarize the state-of-the-art techniques for mathematically modeling cellular stiffness and mechanics and the cytoskeletal components and factors that regulate them. We highlight key experiments that have assisted model parameterization and compare the advantages of different models that have been used to recapitulate these experiments. An overview of feed-forward mechanisms from signaling to cytoskeleton remodeling is provided, followed by a discussion of the rapidly growing niche of encapsulating feedback mechanisms from cytoskeletal and cell mechanics to signaling. We discuss broad areas of advancement that could accelerate research and understanding of cellular mechanobiology. A precise understanding of the molecular mechanisms that affect cell and tissue mechanics and function will underpin innovations in medical device technologies of the future. WIREs Syst Biol Med 2018, 10:e1407. doi: 10.1002/wsbm.1407 This article is categorized under: Models of Systems Properties and Processes > Mechanistic Models Physiology > Mammalian Physiology in Health and Disease Models of Systems Properties and Processes > Cellular Models.
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Affiliation(s)
- Vijay Rajagopal
- Cell Structure and Mechanobiology Group, Department of Biomedical EngineeringUniversity of MelbourneMelbourneAustralia
| | - William R. Holmes
- Department of Physics and AstronomyVanderbilt UniversityNashvilleTNUSA
| | - Peter Vee Sin Lee
- Cell and Tissue Biomechanics Laboratory, Department of Biomedical EngineeringUniversity of MelbourneMelbourneAustralia
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14
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Johnson KC, Clemmens E, Mahmoud H, Kirkpatrick R, Vizcarra JC, Thomas WE. A multiplexed magnetic tweezer with precision particle tracking and bi-directional force control. J Biol Eng 2017; 11:47. [PMID: 29213305 PMCID: PMC5712100 DOI: 10.1186/s13036-017-0091-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 11/22/2017] [Indexed: 11/17/2022] Open
Abstract
Background In the past two decades, methods have been developed to measure the mechanical properties of single biomolecules. One of these methods, Magnetic tweezers, is amenable to aquisition of data on many single molecules simultaneously, but to take full advantage of this "multiplexing" ability, it is necessary to simultaneously incorprorate many capabilities that ahve been only demonstrated separately. Methods Our custom built magnetic tweezer combines high multiplexing, precision bead tracking, and bi-directional force control into a flexible and stable platform for examining single molecule behavior. This was accomplished using electromagnets, which provide high temporal control of force while achieving force levels similar to permanent magnets via large paramagnetic beads. Results Here we describe the instrument and its ability to apply 2–260 pN of force on up to 120 beads simultaneously, with a maximum spatial precision of 12 nm using a variety of bead sizes and experimental techniques. We also demonstrate a novel method for increasing the precision of force estimations on heterogeneous paramagnetic beads using a combination of density separation and bi-directional force correlation which reduces the coefficient of variation of force from 27% to 6%. We then use the instrument to examine the force dependence of uncoiling and recoiling velocity of type 1 fimbriae from Eschericia coli (E. coli) bacteria, and see similar results to previous studies. Conclusion This platform provides a simple, effective, and flexible method for efficiently gathering single molecule force spectroscopy measurements.
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Affiliation(s)
- Keith C Johnson
- Mechanical Engineering, University of Washington, Seattle, USA
| | | | - Hani Mahmoud
- Bioengineering, University of Washington, Seattle, USA
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15
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Pegoraro AF, Janmey P, Weitz DA. Mechanical Properties of the Cytoskeleton and Cells. Cold Spring Harb Perspect Biol 2017; 9:9/11/a022038. [PMID: 29092896 DOI: 10.1101/cshperspect.a022038] [Citation(s) in RCA: 156] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
SUMMARYThe cytoskeleton is the major mechanical structure of the cell; it is a complex, dynamic biopolymer network comprising microtubules, actin, and intermediate filaments. Both the individual filaments and the entire network are not simple elastic solids but are instead highly nonlinear structures. Appreciating the mechanics of biopolymer networks is key to understanding the mechanics of cells. Here, we review the mechanical properties of cytoskeletal polymers and discuss the implications for the behavior of cells.
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Affiliation(s)
- Adrian F Pegoraro
- Department of Physics and School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138
| | - Paul Janmey
- Institute for Medicine and Engineering and Department of Physiology, Perelman School of Medicine, and Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - David A Weitz
- Department of Physics and School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138
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16
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Gurmessa B, Ricketts S, Robertson-Anderson RM. Nonlinear Actin Deformations Lead to Network Stiffening, Yielding, and Nonuniform Stress Propagation. Biophys J 2017; 113:1540-1550. [PMID: 28214480 PMCID: PMC5627063 DOI: 10.1016/j.bpj.2017.01.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 12/16/2016] [Accepted: 01/17/2017] [Indexed: 01/07/2023] Open
Abstract
We use optical tweezers microrheology and fluorescence microscopy to apply nonlinear microscale strains to entangled and cross-linked actin networks, and measure the resulting stress and actin filament deformations. We couple nonlinear stress response and relaxation to the velocities and displacements of individual fluorescent-labeled actin segments, at varying times throughout the strain and varying distances from the strain path, to determine the underlying molecular dynamics that give rise to the debated nonlinear response and stress propagation of cross-linked and entangled actin networks at the microscale. We show that initial stress stiffening arises from acceleration of strained filaments due to molecular extension along the strain, while softening and yielding is coupled to filament deceleration, halting, and recoil. We also demonstrate a surprising nonmonotonic dependence of filament deformation on cross-linker concentration. Namely, networks with no cross-links or substantial cross-links both exhibit fast initial filament velocities and reduced molecular recoil while intermediate cross-linker concentrations display reduced velocities and increased recoil. We show that these collective results are due to a balance of network elasticity and force-induced cross-linker unbinding and rebinding. We further show that cross-links dominate entanglement dynamics when the length between cross-linkers becomes smaller than the length between entanglements. In accord with recent simulations, we demonstrate that post-strain stress can be long-lived in cross-linked networks by distributing stress to a small fraction of highly strained connected filaments that span the network and sustain the load, thereby allowing the rest of the network to recoil and relax.
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Affiliation(s)
- Bekele Gurmessa
- Department of Physics and Biophysics, University of San Diego, San Diego, California
| | - Shea Ricketts
- Department of Physics and Biophysics, University of San Diego, San Diego, California
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17
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Hess H, Ross JL. Non-equilibrium assembly of microtubules: from molecules to autonomous chemical robots. Chem Soc Rev 2017; 46:5570-5587. [PMID: 28329028 PMCID: PMC5603359 DOI: 10.1039/c7cs00030h] [Citation(s) in RCA: 129] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Biological systems have evolved to harness non-equilibrium processes from the molecular to the macro scale. It is currently a grand challenge of chemistry, materials science, and engineering to understand and mimic biological systems that have the ability to autonomously sense stimuli, process these inputs, and respond by performing mechanical work. New chemical systems are responding to the challenge and form the basis for future responsive, adaptive, and active materials. In this article, we describe a particular biochemical-biomechanical network based on the microtubule cytoskeletal filament - itself a non-equilibrium chemical system. We trace the non-equilibrium aspects of the system from molecules to networks and describe how the cell uses this system to perform active work in essential processes. Finally, we discuss how microtubule-based engineered systems can serve as testbeds for autonomous chemical robots composed of biological and synthetic components.
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Affiliation(s)
- H Hess
- Department of Biomedical Engineering, Columbia University, USA.
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18
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Timonen JVI, Grzybowski BA. Tweezing of Magnetic and Non-Magnetic Objects with Magnetic Fields. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1603516. [PMID: 28198579 DOI: 10.1002/adma.201603516] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 10/06/2016] [Indexed: 06/06/2023]
Abstract
Although strong magnetic fields cannot be conveniently "focused" like light, modern microfabrication techniques enable preparation of microstructures with which the field gradients - and resulting magnetic forces - can be localized to very small dimensions. This ability provides the foundation for magnetic tweezers which in their classical variant can address magnetic targets. More recently, the so-called negative magnetophoretic tweezers have also been developed which enable trapping and manipulations of completely nonmagnetic particles provided that they are suspended in a high-magnetic-susceptibility liquid. These two modes of magnetic tweezing are complimentary techniques tailorable for different types of applications. This Progress Report provides the theoretical basis for both modalities and illustrates their specific uses ranging from the manipulation of colloids in 2D and 3D, to trapping of living cells, control of cell function, experiments with single molecules, and more.
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Affiliation(s)
- Jaakko V I Timonen
- Department of Applied Physics, Aalto University School of Science, Espoo, 02150, Finland
| | - Bartosz A Grzybowski
- Center for Soft and Living Matter, Ulsan National Institute of Science and Technology, Ulsan, 44919, South Korea
- Department of Chemistry, Ulsan National Institute of Science and Technology, Ulsan, 44919, South Korea
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19
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Sulfo-SMCC Prevents Annealing of Taxol-Stabilized Microtubules In Vitro. PLoS One 2016; 11:e0161623. [PMID: 27561096 PMCID: PMC4999061 DOI: 10.1371/journal.pone.0161623] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 08/09/2016] [Indexed: 11/21/2022] Open
Abstract
Microtubule structure and functions have been widely studied in vitro and in cells. Research has shown that cysteines on tubulin play a crucial role in the polymerization of microtubules. Here, we show that blocking sulfhydryl groups of cysteines in taxol-stabilized polymerized microtubules with a commonly used chemical crosslinker prevents temporal end-to-end annealing of microtubules in vitro. This can dramatically affect the length distribution of the microtubules. The crosslinker sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate, sulfo-SMCC, consists of a maleimide and an N-hydroxysuccinimide ester group to bind to sulfhydryl groups and primary amines, respectively. Interestingly, addition of a maleimide dye alone does not show the same interference with annealing in stabilized microtubules. This study shows that the sulfhydryl groups of cysteines of tubulin that are vital for the polymerization are also important for the subsequent annealing of microtubules.
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20
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Waigh TA. Advances in the microrheology of complex fluids. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:074601. [PMID: 27245584 DOI: 10.1088/0034-4885/79/7/074601] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
New developments in the microrheology of complex fluids are considered. Firstly the requirements for a simple modern particle tracking microrheology experiment are introduced, the error analysis methods associated with it and the mathematical techniques required to calculate the linear viscoelasticity. Progress in microrheology instrumentation is then described with respect to detectors, light sources, colloidal probes, magnetic tweezers, optical tweezers, diffusing wave spectroscopy, optical coherence tomography, fluorescence correlation spectroscopy, elastic- and quasi-elastic scattering techniques, 3D tracking, single molecule methods, modern microscopy methods and microfluidics. New theoretical techniques are also reviewed such as Bayesian analysis, oversampling, inversion techniques, alternative statistical tools for tracks (angular correlations, first passage probabilities, the kurtosis, motor protein step segmentation etc), issues in micro/macro rheological agreement and two particle methodologies. Applications where microrheology has begun to make some impact are also considered including semi-flexible polymers, gels, microorganism biofilms, intracellular methods, high frequency viscoelasticity, comb polymers, active motile fluids, blood clots, colloids, granular materials, polymers, liquid crystals and foods. Two large emergent areas of microrheology, non-linear microrheology and surface microrheology are also discussed.
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Affiliation(s)
- Thomas Andrew Waigh
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Oxford Rd., Manchester, M13 9PL, UK. Photon Science Institute, University of Manchester, Oxford Rd., Manchester, M13 9PL, UK
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21
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Wilcox JC, Lopez BJ, Campàs O, Valentine MT. Improved calibration of the nonlinear regime of a single-beam gradient optical trap. OPTICS LETTERS 2016; 41:2386-2389. [PMID: 27177009 DOI: 10.1364/ol.41.002386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report an improved method for calibrating the nonlinear region of a single-beam gradient optical trap. Through analysis of the position fluctuations of a trapped object that is displaced from the trap center by controlled flow we measure the local trap stiffness in both the linear and nonlinear regimes without knowledge of the magnitude of the applied external forces. This approach requires only knowledge of the system temperature, and is especially useful for measurements involving trapped objects of unknown size, or objects in a fluid of unknown viscosity.
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22
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Piechocka IK, Jansen KA, Broedersz CP, Kurniawan NA, MacKintosh FC, Koenderink GH. Multi-scale strain-stiffening of semiflexible bundle networks. SOFT MATTER 2016; 12:2145-56. [PMID: 26761718 DOI: 10.1039/c5sm01992c] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Bundles of polymer filaments are responsible for the rich and unique mechanical behaviors of many biomaterials, including cells and extracellular matrices. In fibrin biopolymers, whose nonlinear elastic properties are crucial for normal blood clotting, protofibrils self-assemble and bundle to form networks of semiflexible fibers. Here we show that the extraordinary strain-stiffening response of fibrin networks is a direct reflection of the hierarchical architecture of the fibrin fibers. We measure the rheology of networks of unbundled protofibrils and find excellent agreement with an affine model of extensible wormlike polymers. By direct comparison with these data, we show that physiological fibrin networks composed of thick fibers can be modeled as networks of tight protofibril bundles. We demonstrate that the tightness of coupling between protofibrils in the fibers can be tuned by the degree of enzymatic intermolecular crosslinking by the coagulation factor XIII. Furthermore, at high stress, the protofibrils contribute independently to the network elasticity, which may reflect a decoupling of the tight bundle structure. The hierarchical architecture of fibrin fibers can thus account for the nonlinearity and enormous elastic resilience characteristic of blood clots.
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23
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Kim OV, Liang X, Litvinov RI, Weisel JW, Alber MS, Purohit PK. Foam-like compression behavior of fibrin networks. Biomech Model Mechanobiol 2016; 15:213-228. [PMID: 25982442 PMCID: PMC4873005 DOI: 10.1007/s10237-015-0683-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 05/06/2015] [Indexed: 12/28/2022]
Abstract
The rheological properties of fibrin networks have been of long-standing interest. As such there is a wealth of studies of their shear and tensile responses, but their compressive behavior remains unexplored. Here, by characterization of the network structure with synchronous measurement of the fibrin storage and loss moduli at increasing degrees of compression, we show that the compressive behavior of fibrin networks is similar to that of cellular solids. A nonlinear stress-strain response of fibrin consists of three regimes: (1) an initial linear regime, in which most fibers are straight, (2) a plateau regime, in which more and more fibers buckle and collapse, and (3) a markedly nonlinear regime, in which network densification occurs by bending of buckled fibers and inter-fiber contacts. Importantly, the spatially non-uniform network deformation included formation of a moving "compression front" along the axis of strain, which segregated the fibrin network into compartments with different fiber densities and structure. The Young's modulus of the linear phase depends quadratically on the fibrin volume fraction while that in the densified phase depends cubically on it. The viscoelastic plateau regime corresponds to a mixture of these two phases in which the fractions of the two phases change during compression. We model this regime using a continuum theory of phase transitions and analytically predict the storage and loss moduli which are in good agreement with the experimental data. Our work shows that fibrin networks are a member of a broad class of natural cellular materials which includes cancellous bone, wood and cork.
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Affiliation(s)
- Oleg V. Kim
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, Indiana
| | - Xiaojun Liang
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA
| | - Rustem I. Litvinov
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - John W. Weisel
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Mark S. Alber
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, Indiana
- Department of Medicine, Indiana University School of Medicine, Indianapolis
| | - Prashant K. Purohit
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA
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24
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Lopez BJ, Valentine MT. Molecular control of stress transmission in the microtubule cytoskeleton. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015. [PMID: 26225932 DOI: 10.1016/j.bbamcr.2015.07.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In this article, we will summarize recent progress in understanding the mechanical origins of rigidity, strength, resiliency and stress transmission in the MT cytoskeleton using reconstituted networks formed from purified components. We focus on the role of network architecture, crosslinker compliance and dynamics, and molecular determinants of single filament elasticity, while highlighting open questions and future directions for this work.
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Affiliation(s)
- Benjamin J Lopez
- Department of Mechanical Engineering and Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106-5070, USA
| | - Megan T Valentine
- Department of Mechanical Engineering and Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106-5070, USA.
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25
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Vaca C, Shlomovitz R, Yang Y, Valentine MT, Levine AJ. Bond breaking dynamics in semiflexible networks under load. SOFT MATTER 2015; 11:4899-4911. [PMID: 26012737 DOI: 10.1039/c5sm00262a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We examine the bond-breaking dynamics of transiently cross-linked semiflexible networks using a single filament model in which that filament is peeled from an array of cross-linkers. We examine the effect of quenched disorder in the placement of the linkers along the filament and the effect of stochastic bond-breaking (assuming Bell model unbinding kinetics) on the dynamics of filament cross-linker dissociation and the statistics of ripping events. We find that bond forces decay exponentially away from the point of loading and that bond breaking proceeds sequentially down the linker array from the point of loading in a series of stochastic ripping events. We compare these theoretical predictions to the observed trajectories of large beads in a cross-linked microtubule network and identify the observed jumps of the bead with the linker rupture events predicted by the single filament model.
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Affiliation(s)
- Christian Vaca
- Department of Physics & Astronomy, UCLA, Los Angeles, CA 90005, USA.
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26
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Mechanics and dynamics of reconstituted cytoskeletal systems. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:3038-42. [PMID: 26130089 DOI: 10.1016/j.bbamcr.2015.06.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 06/22/2015] [Accepted: 06/23/2015] [Indexed: 01/21/2023]
Abstract
The intracellular cytoskeleton is an active dynamic network of filaments and associated binding proteins that control key cellular properties, such as cell shape and mechanics. Due to the inherent complexity of the cell, reconstituted model systems have been successfully employed to gain an understanding of the fundamental physics governing cytoskeletal processes. Here, we review recent advances and key aspects of these reconstituted systems. We focus on the importance of assembly kinetics and dynamic arrest in determining network mechanics, and highlight novel emergent behavior occurring through interactions between cytoskeletal components in more complex networks incorporating multiple biopolymers and molecular motors.
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27
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Ahmed WW, Fodor É, Betz T. Active cell mechanics: Measurement and theory. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:3083-94. [PMID: 26025677 DOI: 10.1016/j.bbamcr.2015.05.022] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 05/16/2015] [Accepted: 05/21/2015] [Indexed: 10/25/2022]
Abstract
Living cells are active mechanical systems that are able to generate forces. Their structure and shape are primarily determined by biopolymer filaments and molecular motors that form the cytoskeleton. Active force generation requires constant consumption of energy to maintain the nonequilibrium activity to drive organization and transport processes necessary for their function. To understand this activity it is necessary to develop new approaches to probe the underlying physical processes. Active cell mechanics incorporates active molecular-scale force generation into the traditional framework of mechanics of materials. This review highlights recent experimental and theoretical developments towards understanding active cell mechanics. We focus primarily on intracellular mechanical measurements and theoretical advances utilizing the Langevin framework. These developing approaches allow a quantitative understanding of nonequilibrium mechanical activity in living cells. This article is part of a Special Issue entitled: Mechanobiology.
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Affiliation(s)
- Wylie W Ahmed
- Institut Curie, Centre de recherche, 11, rue Pierre et Marie Curie, 75005 Paris, France; Sorbonne Universités, Université Pierre et Marie Curie, Paris, France; Centre National de la Recherche Scientifique, UMR168, Paris, France.
| | - Étienne Fodor
- Laboratoire Matière et Systèmes Complexes, UMR7057, Université Paris Diderot, 75013 Paris, France
| | - Timo Betz
- Institut Curie, Centre de recherche, 11, rue Pierre et Marie Curie, 75005 Paris, France; Sorbonne Universités, Université Pierre et Marie Curie, Paris, France; Centre National de la Recherche Scientifique, UMR168, Paris, France
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28
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Zacchia NA, Valentine MT. Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2015; 86:053704. [PMID: 26026529 DOI: 10.1063/1.4921553] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present the design methodology for arrays of neodymium iron boron (NdFeB)-based magnets for use in magnetic tweezers devices. Using finite element analysis (FEA), we optimized the geometry of the NdFeB magnet as well as the geometry of iron yokes designed to focus the magnetic fields toward the sample plane. Together, the magnets and yokes form a magnetic array which is the basis of the magnetic tweezers device. By systematically varying 15 distinct shape parameters, we determined those features that maximize the magnitude of the magnetic field gradient as well as the length scale over which the magnetic force operates. Additionally, we demonstrated that magnetic saturation of the yoke material leads to intrinsic limitations in any geometric design. Using this approach, we generated a compact and light-weight magnetic tweezers device that produces a high field gradient at the image plane in order to apply large forces to magnetic beads. We then fabricated the optimized yoke and validated the FEA by experimentally mapping the magnetic field of the device. The optimization data and iterative FEA approach outlined here will enable the streamlined design and construction of specialized instrumentation for force-sensitive microscopy.
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Affiliation(s)
- Nicholas A Zacchia
- Department of Mechanical Engineering and Materials Research Laboratory, University of California, Santa Barbara, California 93106, USA
| | - Megan T Valentine
- Department of Mechanical Engineering and Materials Research Laboratory, University of California, Santa Barbara, California 93106, USA
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29
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Sagiri S, Singh VK, Pal K, Banerjee I, Basak P. Stearic acid based oleogels: A study on the molecular, thermal and mechanical properties. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2015; 48:688-99. [DOI: 10.1016/j.msec.2014.12.018] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 11/01/2014] [Accepted: 12/05/2014] [Indexed: 11/17/2022]
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30
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González de Torre I, Quintanilla L, Pinedo-Martín G, Alonso M, Rodríguez-Cabello JC. Nanogel formation from dilute solutions of clickable elastin-like recombinamers and its dependence on temperature: two fractal gelation modes. ACS APPLIED MATERIALS & INTERFACES 2014; 6:14509-14515. [PMID: 25068707 DOI: 10.1021/am503651y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Diluted, complementary, click-reactive elastin-like recombinamer (ELR) solutions have been prepared and mixed at two different temperatures, one below and one above the characteristic transition temperature (Tt) of these chemically modified ELRs. FTIR measurements, size, aspect ratio, zeta potential, and microrheological measurements have been carried out on the nanostructures formed under these dilute conditions as a way to better understand the relationship between the final macroscopic properties of ELR-based hydrogels and the molecular conditions governing the initial stages of the chemical cross-linking process that occurs, especially its dependence on the preparation temperature relative to Tt. As a result, two different fractal modes of gel formation have been found at the two temperatures studied (above and below Tt). Thus, when the reaction mixture is prepared below Tt, essentially one-dimensional linear nanogels with a high aspect ratio are obtained. In contrast, 3D nanogels are formed above Tt, with spherical shapes predominating. These different structures seem to reflect the two molecular organizations of the single components of the mixture under these conditions, namely extended chains below Tt and a spherical arrangement above Tt. In addition to the interest in these nanogels as models for understanding the formation of microscopic structures and differential macroscopic properties under more conventional hydrogel-formation conditions, these nanogels are of interest because of their thermoresponsiveness and biocompatibility, which provide them with potential uses for drug delivery and other biomedical applications in living systems.
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Affiliation(s)
- Israel González de Torre
- BIOFORGE, CIBER-BBN, Campus "Miguel Delibes" Centro I+D, Universidad de Valladolid , Paseo Belén 11, 47011 Valladolid, Spain
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31
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Müller KW, Bruinsma RF, Lieleg O, Bausch AR, Wall WA, Levine AJ. Rheology of semiflexible bundle networks with transient linkers. PHYSICAL REVIEW LETTERS 2014; 112:238102. [PMID: 24972229 DOI: 10.1103/physrevlett.112.238102] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Indexed: 06/03/2023]
Abstract
We present a theoretical and computational analysis of the rheology of networks made up of bundles of semiflexible filaments bound by transient cross-linkers. Such systems are ubiquitous in the cytoskeleton and can be formed in vitro using filamentous actin and various cross-linkers. We find that their high-frequency rheology is characterized by a scaling behavior that is quite distinct from that of networks of the well-studied single semiflexible filaments. This regime can be understood theoretically in terms of a length-scale-dependent bending modulus for bundles. Next, we observe new dissipative dynamics associated with the shear-induced disruption of the network at intermediate frequencies. Finally, at low frequencies, we encounter a region of non-Newtonian rheology characterized by power-law scaling. This regime is dominated by bundle dissolution and large-scale rearrangements of the network driven by equilibrium thermal fluctuations.
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Affiliation(s)
- Kei W Müller
- Institute for Computational Mechanics, Technische Universität München, 85748 Garching, Germany
| | - Robijn F Bruinsma
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1596, USA and Department of Physics and Astronomy, UCLA, Los Angeles, California 90095-1596, USA
| | - Oliver Lieleg
- Institute for Medical Engineering IMETUM, Technische Universität München, 85748 Garching, Germany
| | - Andreas R Bausch
- Lehrstuhl für Zellbiophysik E27, Physik Department, Technische Universität München, 85748 Garching, Germany
| | - Wolfgang A Wall
- Institute for Computational Mechanics, Technische Universität München, 85748 Garching, Germany
| | - Alex J Levine
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1596, USA and Department of Physics and Astronomy, UCLA, Los Angeles, California 90095-1596, USA and Department of Biomathematics, UCLA, Los Angeles, California 90095-1596, USA
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Yang Y, Valentine MT. Determining the structure-mechanics relationships of dense microtubule networks with confocal microscopy and magnetic tweezers-based microrheology. Methods Cell Biol 2013; 115:75-96. [PMID: 23973067 DOI: 10.1016/b978-0-12-407757-7.00006-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The microtubule (MT) cytoskeleton is essential in maintaining the shape, strength, and organization of cells. Its spatiotemporal organization is fundamental for numerous dynamic biological processes, and mechanical stress within the MT cytoskeleton provides an important signaling mechanism in mitosis and neural development. This raises important questions about the relationships between structure and mechanics in complex MT structures. In vitro, reconstituted cytoskeletal networks provide a minimal model of cell mechanics while also providing a testing ground for the fundamental polymer physics of stiff polymer gels. Here, we describe our development and implementation of a broad tool kit to study structure-mechanics relationships in reconstituted MT networks, including protocols for the assembly of entangled and cross-linked MT networks, fluorescence imaging, microstructure characterization, construction and calibration of magnetic tweezers devices, and mechanical data collection and analysis. In particular, we present the design and assembly of three neodymium iron boron (NdFeB)-based magnetic tweezers devices optimized for use with MT networks: (1) high-force magnetic tweezers devices that enable the application of nano-Newton forces and possible meso- to macroscale materials characterization; (2) ring-shaped NdFeB-based magnetic tweezers devices that enable oscillatory microrheology measurements; and (3) portable magnetic tweezers devices that enable direct visualization of microscale deformation in soft materials under applied force.
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Affiliation(s)
- Yali Yang
- Department of Mechanical Engineering, University of California, Santa Barbara, California, USA
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