1
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Smith AD, Donley GJ, Del Gado E, Zavala VM. Topological Data Analysis for Particulate Gels. ACS NANO 2024. [PMID: 39321316 DOI: 10.1021/acsnano.4c04969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/27/2024]
Abstract
Soft gels, formed via the self-assembly of particulate materials, exhibit intricate multiscale structures that provide them with flexibility and resilience when subjected to external stresses. This work combines particle simulations and topological data analysis (TDA) to characterize the complex multiscale structure of soft gels. Our TDA analysis focuses on the use of the Euler characteristic, which is an interpretable and computationally scalable topological descriptor that is combined with filtration operations to obtain information on the geometric (local) and topological (global) structure of soft gels. We reduce the topological information obtained with TDA using principal component analysis (PCA) and show that this provides an informative low-dimensional representation of the gel structure. We use the proposed computational framework to investigate the influence of gel preparation (e.g., quench rate, volume fraction) on soft gel structure and to explore dynamic deformations that emerge under oscillatory shear in various response regimes (linear, nonlinear, and flow). Our analysis provides evidence of the existence of hierarchical structures in soft gels, which are not easily identifiable otherwise. Moreover, our analysis reveals direct correlations between topological changes of the gel structure under deformation and mechanical phenomena distinctive of gel materials, such as stiffening and yielding. In summary, we show that TDA facilitates the mathematical representation, quantification, and analysis of soft gel structures, extending traditional network analysis methods to capture both local and global organization.
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Affiliation(s)
- Alexander D Smith
- Department of Chemical Engineering and Material Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Gavin J Donley
- Department of Physics, Georgetown University, Washington, DC 20057, United States
| | - Emanuela Del Gado
- Department of Physics, Georgetown University, Washington, DC 20057, United States
- Institute for Soft Matter Synthesis and Metrology, Georgetown University, Washington DC 20057, United States
| | - Victor M Zavala
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
- Mathematics and Computer Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
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2
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Le Roy H, Song J, Lundberg D, Zhukhovitskiy AV, Johnson JA, McKinley GH, Holten-Andersen N, Lenz M. Valence can control the nonexponential viscoelastic relaxation of multivalent reversible gels. SCIENCE ADVANCES 2024; 10:eadl5056. [PMID: 38748785 PMCID: PMC11095449 DOI: 10.1126/sciadv.adl5056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 04/10/2024] [Indexed: 05/19/2024]
Abstract
Gels made of telechelic polymers connected by reversible cross-linkers are a versatile design platform for biocompatible viscoelastic materials. Their linear response to a step strain displays a fast, near-exponential relaxation when using low-valence cross-linkers, while larger supramolecular cross-linkers bring about much slower dynamics involving a wide distribution of timescales whose physical origin is still debated. Here, we propose a model where the relaxation of polymer gels in the dilute regime originates from elementary events in which the bonds connecting two neighboring cross-linkers all disconnect. Larger cross-linkers allow for a greater average number of bonds connecting them but also generate more heterogeneity. We characterize the resulting distribution of relaxation timescales analytically and accurately reproduce stress relaxation measurements on metal-coordinated hydrogels with a variety of cross-linker sizes including ions, metal-organic cages, and nanoparticles. Our approach is simple enough to be extended to any cross-linker size and could thus be harnessed for the rational design of complex viscoelastic materials.
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Affiliation(s)
- Hugo Le Roy
- Université Paris-Saclay, CNRS, LPTMS, 91405, Orsay, France
- Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Jake Song
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA
| | - David Lundberg
- Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Aleksandr V. Zhukhovitskiy
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jeremiah A. Johnson
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Gareth H. McKinley
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Niels Holten-Andersen
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
- Department of Bioengineering and Materials Science and Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - Martin Lenz
- Université Paris-Saclay, CNRS, LPTMS, 91405, Orsay, France
- PMMH, CNRS, ESPCI Paris, PSL University, Sorbonne Université, Université de Paris, F-75005 Paris, France
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3
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Sun ZG, Yadav V, Amiri S, Cao W, De La Cruz EM, Murrell M. Cofilin-mediated actin filament network flexibility facilitates 2D to 3D actomyosin shape change. Eur J Cell Biol 2024; 103:151379. [PMID: 38168598 DOI: 10.1016/j.ejcb.2023.151379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 12/06/2023] [Accepted: 12/16/2023] [Indexed: 01/05/2024] Open
Abstract
The organization of actin filaments (F-actin) into crosslinked networks determines the transmission of mechanical stresses within the cytoskeleton and subsequent changes in cell and tissue shape. Principally mediated by proteins such as α-actinin, F-actin crosslinking increases both network connectivity and rigidity, thereby facilitating stress transmission at low crosslinking yet attenuating transmission at high crosslinker concentration. Here, we engineer a two-dimensional model of the actomyosin cytoskeleton, in which myosin-induced mechanical stresses are controlled by light. We alter the extent of F-actin crosslinking by the introduction of oligomerized cofilin. At pH 6.5, F-actin severing by cofilin is weak, but cofilin bundles and crosslinks filaments. Given its effect of lowering the F-actin bending stiffness, cofilin- crosslinked networks are significantly more flexible and softer in bending than networks crosslinked by α-actinin. Thus, upon local activation of myosin-induced contractile stress, the network bends out-of-plane in contrast to the in-plane compression as observed with networks crosslinked by α-actinin. Here, we demonstrate that local effects on filament mechanics by cofilin introduces novel large-scale network material properties that enable the sculpting of complex shapes in the cell cytoskeleton.
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Affiliation(s)
- Zachary Gao Sun
- Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Physics, Yale University, 217 Prospect Street, New Haven, CT 06511, USA; Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, CT 06520, USA
| | - Vikrant Yadav
- Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Biomedical Engineering, Yale University, New Haven, CT 06511, USA
| | - Sorosh Amiri
- Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Mechanical Engineering and Material Science, Yale University, New Haven, CT 06511, USA
| | - Wenxiang Cao
- Department of Molecular Biology & Biophysics, Yale University, New Haven, CT 06511, USA
| | - Enrique M De La Cruz
- Department of Molecular Biology & Biophysics, Yale University, New Haven, CT 06511, USA
| | - Michael Murrell
- Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Biomedical Engineering, Yale University, New Haven, CT 06511, USA; Department of Physics, Yale University, 217 Prospect Street, New Haven, CT 06511, USA; Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, CT 06520, USA.
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4
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Moghimi E, Chubak I, Ntetsikas K, Polymeropoulos G, Wang X, Carillo C, Statt A, Cipelletti L, Mortensen K, Hadjichristidis N, Panagiotopoulos AZ, Likos CN, Vlassopoulos D. Interpenetrated and Bridged Nanocylinders from Self-Assembled Star Block Copolymers. Macromolecules 2024; 57:926-939. [PMID: 38911231 PMCID: PMC11190992 DOI: 10.1021/acs.macromol.3c02088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 01/05/2024] [Accepted: 01/10/2024] [Indexed: 06/25/2024]
Abstract
The design of functional polymeric materials with tunable response requires a synergetic use of macromolecular architecture and interactions. Here, we combine experiments with computer simulations to demonstrate how physical properties of gels can be tailored at the molecular level, using star block copolymers with alternating block sequences as a paradigm. Telechelic star polymers containing attractive outer blocks self-assemble into soft patchy nanoparticles, whereas their mirror-image inverted architecture with inner attractive blocks yields micelles. In concentrated solutions, bridged and interpenetrated hexagonally packed nanocylinders are formed, respectively, with distinct structural and rheological properties. The phase diagrams exhibit a peculiar re-entrance where the hexagonal phase melts upon both heating and cooling because of solvent-block and block-block interactions. The bridged nanostructure is characterized by similar deformability, extended structural coherence, enhanced elasticity, and yield stress compared to micelles or typical colloidal gels, which make them promising and versatile materials for diverse applications.
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Affiliation(s)
- Esmaeel Moghimi
- Institute
of Electronic Structure and Laser, FORTH, Heraklion 71110, Crete, Greece
- Department
of Materials Science and Technology, University
of Crete, Heraklion 71003, Crete, Greece
| | - Iurii Chubak
- Faculty
of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria
- Physico-Chimie
des électrolytes et Nanosystèmes Interfaciaux, Sorbonne Université CNRS, F-75005 Paris, France
| | - Konstantinos Ntetsikas
- Polymer
Synthesis Laboratory, Chemistry Program, KAUST Catalysis Center, Physical
Sciences and Engineering Division, King
Abdullah University of Science and Technology (KAUST), Thuwal 23955, Kingdom of Saudi Arabia
| | - Georgios Polymeropoulos
- Polymer
Synthesis Laboratory, Chemistry Program, KAUST Catalysis Center, Physical
Sciences and Engineering Division, King
Abdullah University of Science and Technology (KAUST), Thuwal 23955, Kingdom of Saudi Arabia
| | - Xin Wang
- Polymer
Synthesis Laboratory, Chemistry Program, KAUST Catalysis Center, Physical
Sciences and Engineering Division, King
Abdullah University of Science and Technology (KAUST), Thuwal 23955, Kingdom of Saudi Arabia
| | - Consiglia Carillo
- Institute
of Electronic Structure and Laser, FORTH, Heraklion 71110, Crete, Greece
- Department
of Materials Science and Technology, University
of Crete, Heraklion 71003, Crete, Greece
| | - Antonia Statt
- Materials
Science and Engineering, Grainger College of Engineering, University of Illinois, Urbana−Champaign, Illinois 61801, United States
| | - Luca Cipelletti
- Laboratoire
Charles Coulomb (L2C), University of Montpellier, 34090 Montpellier, France
- Institut
Universitaire de France, IUF, 75231 Paris, Cedex 05, France
| | - Kell Mortensen
- Niels
Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
| | - Nikos Hadjichristidis
- Polymer
Synthesis Laboratory, Chemistry Program, KAUST Catalysis Center, Physical
Sciences and Engineering Division, King
Abdullah University of Science and Technology (KAUST), Thuwal 23955, Kingdom of Saudi Arabia
| | | | - Christos N. Likos
- Faculty
of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria
| | - Dimitris Vlassopoulos
- Institute
of Electronic Structure and Laser, FORTH, Heraklion 71110, Crete, Greece
- Department
of Materials Science and Technology, University
of Crete, Heraklion 71003, Crete, Greece
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5
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Saporta-Katz O, Moriel A. Self-driven configurational dynamics in frustrated spring-mass systems. Phys Rev E 2024; 109:024219. [PMID: 38491674 DOI: 10.1103/physreve.109.024219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 01/29/2024] [Indexed: 03/18/2024]
Abstract
Various physical systems relax mechanical frustration through configurational rearrangements. We examine such rearrangements via Hamiltonian dynamics of simple internally stressed harmonic four-mass systems. We demonstrate theoretically and numerically how mechanical frustration controls the underlying potential energy landscape. Then, we examine the harmonic four-mass systems' Hamiltonian dynamics and relate the onset of chaotic motion to self-driven rearrangements. We show such configurational dynamics may occur without strong precursors, rendering such dynamics seemingly spontaneous.
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Affiliation(s)
- Ori Saporta-Katz
- Computer Science and Applied Mathematics Department, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Avraham Moriel
- Chemical and Biological Physics Department, Weizmann Institute of Science, Rehovot 7610001, Israel
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6
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Glaser M, Mollenkopf P, Prascevic D, Ferraz C, Käs JA, Schnauß J, Smith DM. Systematic altering of semiflexible DNA-based polymer networks via tunable crosslinking. NANOSCALE 2023; 15:7374-7383. [PMID: 37039012 PMCID: PMC10134436 DOI: 10.1039/d2nr05615a] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 04/02/2023] [Indexed: 06/19/2023]
Abstract
In order to understand and predict the mechanical behaviours of complex, soft biomaterials such as cells or stimuli-responsive hydrogels, it is important to connect how the nanoscale properties of their constituent components impact those of the bulk material. Crosslinked networks of semiflexible polymers are particularly ubiquitous, being underlying mechanical components of biological systems such as cells or ECM, as well as many synthetic or biomimetic materials. Cell-derived components such as filamentous biopolymers or protein crosslinkers are readily available and well-studied model systems. However, as evolutionarily derived materials, they are constrained to a fixed set of structural parameters such as the rigidity and size of the filaments, or the valency and strength of binding of crosslinkers forming inter-filament connections. By implementing a synthetic model system based on the self-assembly of DNA oligonucleotides into nanometer-scale tubes and simple crosslinking constructs, we used the thermodynamic programmability of DNA hybridization to explore the impact of binding affinity on bulk mechanical response. Stepwise tuning the crosslinking affinity over a range from transient to thermodynamically stable shows an according change in viscoelastic behaviour from loosely entangled to elastic, consistent with models accounting for generalized inter-filament interactions. While characteristic signatures of concentration-dependent changes in network morphology found in some other natural and synthetic filament-crosslinker systems were not apparent, the presence of a distinct elasticity increase within a narrow range of conditions points towards potential subtle alterations of crosslink-filament architecture. Here, we demonstrate a new synthetic approach for gaining a deeper understanding of both biological as well as engineered hydrogel systems.
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Affiliation(s)
- Martin Glaser
- DNA Nanodevices Group, Fraunhofer Institute for Cell Therapy and Immunology, Perlickstr. 1, 04103 Leipzig, Germany.
- Soft Matter Physics Division, Peter Debye Institute, Faculty of Physics and Earth Sciences, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany
| | - Paul Mollenkopf
- DNA Nanodevices Group, Fraunhofer Institute for Cell Therapy and Immunology, Perlickstr. 1, 04103 Leipzig, Germany.
- Soft Matter Physics Division, Peter Debye Institute, Faculty of Physics and Earth Sciences, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany
| | - Dusan Prascevic
- DNA Nanodevices Group, Fraunhofer Institute for Cell Therapy and Immunology, Perlickstr. 1, 04103 Leipzig, Germany.
| | - Catarina Ferraz
- DNA Nanodevices Group, Fraunhofer Institute for Cell Therapy and Immunology, Perlickstr. 1, 04103 Leipzig, Germany.
- Soft Matter Physics Division, Peter Debye Institute, Faculty of Physics and Earth Sciences, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany
| | - Josef A Käs
- DNA Nanodevices Group, Fraunhofer Institute for Cell Therapy and Immunology, Perlickstr. 1, 04103 Leipzig, Germany.
| | - Jörg Schnauß
- DNA Nanodevices Group, Fraunhofer Institute for Cell Therapy and Immunology, Perlickstr. 1, 04103 Leipzig, Germany.
- Soft Matter Physics Division, Peter Debye Institute, Faculty of Physics and Earth Sciences, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany
| | - David M Smith
- DNA Nanodevices Group, Fraunhofer Institute for Cell Therapy and Immunology, Perlickstr. 1, 04103 Leipzig, Germany.
- Soft Matter Physics Division, Peter Debye Institute, Faculty of Physics and Earth Sciences, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany
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7
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Akenuwa OH, Abel SM. Organization and dynamics of cross-linked actin filaments in confined environments. Biophys J 2023; 122:30-42. [PMID: 36461638 PMCID: PMC9822838 DOI: 10.1016/j.bpj.2022.11.2944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 11/02/2022] [Accepted: 11/28/2022] [Indexed: 12/03/2022] Open
Abstract
The organization of the actin cytoskeleton is impacted by the interplay between physical confinement, features of cross-linking proteins, and deformations of semiflexible actin filaments. Some cross-linking proteins preferentially bind filaments in parallel, although others bind more indiscriminately. However, a quantitative understanding of how the mode of binding influences the assembly of actin networks in confined environments is lacking. Here we employ coarse-grained computer simulations to study the dynamics and organization of semiflexible actin filaments in confined regions upon the addition of cross-linkers. We characterize how the emergent behavior is influenced by the system shape, the number and type of cross-linking proteins, and the length of filaments. Structures include isolated clusters of filaments, highly connected filament bundles, and networks of interconnected bundles and loops. Elongation of one dimension of the system promotes the formation of long bundles that align with the elongated axis. Dynamics are governed by rapid cross-linking into aggregates, followed by a slower change in their shape and connectivity. Cross-linking decreases the average bending energy of short or sparsely connected filaments by suppressing shape fluctuations. However, it increases the average bending energy in highly connected networks because filament bundles become deformed, and small numbers of filaments exhibit long-lived, highly unfavorable configurations. Indiscriminate cross-linking promotes the formation of high-energy configurations due to the increased likelihood of unfavorable, difficult-to-relax configurations at early times. Taken together, this work demonstrates physical mechanisms by which cross-linker binding and physical confinement impact the emergent behavior of actin networks, which is relevant both in cells and in synthetic environments.
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Affiliation(s)
- Oghosa H Akenuwa
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee
| | - Steven M Abel
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee.
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8
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Dwyer ME, Robertson-Anderson RM, Gurmessa BJ. Nonlinear Microscale Mechanics of Actin Networks Governed by Coupling of Filament Crosslinking and Stabilization. Polymers (Basel) 2022; 14:polym14224980. [PMID: 36433106 PMCID: PMC9696012 DOI: 10.3390/polym14224980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 11/11/2022] [Accepted: 11/14/2022] [Indexed: 11/19/2022] Open
Abstract
Actin plays a vital role in maintaining the stability and rigidity of biological cells while allowing for cell motility and shape change. The semiflexible nature of actin filaments-along with the myriad actin-binding proteins (ABPs) that serve to crosslink, bundle, and stabilize filaments-are central to this multifunctionality. The effect of ABPs on the structural and mechanical properties of actin networks has been the topic of fervent investigation over the past few decades. Yet, the combined impact of filament stabilization, stiffening and crosslinking via ABPs on the mechanical response of actin networks has yet to be explored. Here, we perform optical tweezers microrheology measurements to characterize the nonlinear force response and relaxation dynamics of actin networks in the presence of varying concentrations of α-actinin, which transiently crosslinks actin filaments, and phalloidin, which stabilizes filamentous actin and increases its persistence length. We show that crosslinking and stabilization can act both synergistically and antagonistically to tune the network resistance to nonlinear straining. For example, phalloidin stabilization leads to enhanced elastic response and reduced dissipation at large strains and timescales, while the initial microscale force response is reduced compared to networks without phalloidin. Moreover, we find that stabilization switches this initial response from that of stress stiffening to softening despite the increased filament stiffness that phalloidin confers. Finally, we show that both crosslinking and stabilization are necessary to elicit these emergent features, while the effect of stabilization on networks without crosslinkers is much more subdued. We suggest that these intriguing mechanical properties arise from the competition and cooperation between filament connectivity, bundling, and rigidification, shedding light on how ABPs with distinct roles can act in concert to mediate diverse mechanical properties of the cytoskeleton and bio-inspired polymeric materials.
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Affiliation(s)
- Mike E. Dwyer
- Department of Physics and Astronomy, Bucknell University, Lewisburg, PA 17837, USA
| | | | - Bekele J. Gurmessa
- Department of Physics and Astronomy, Bucknell University, Lewisburg, PA 17837, USA
- Correspondence:
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9
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Chandrasekaran A, Giniger E, Papoian GA. Nucleation causes an actin network to fragment into multiple high-density domains. Biophys J 2022; 121:3200-3212. [PMID: 35927959 PMCID: PMC9463697 DOI: 10.1016/j.bpj.2022.07.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 12/20/2021] [Accepted: 07/28/2022] [Indexed: 11/02/2022] Open
Abstract
Actin networks rely on nucleation mechanisms to generate new filaments because spontaneous nucleation is kinetically disfavored. Branching nucleation of actin filaments by actin-related protein (Arp2/3), in particular, is critical for actin self-organization. In this study, we use the simulation platform for active matter MEDYAN to generate 2000 s long stochastic trajectories of actin networks, under varying Arp2/3 concentrations, in reaction volumes of biologically meaningful size (>20 μm3). We find that the dynamics of Arp2/3 increase the abundance of short filaments and increases network treadmilling rate. By analyzing the density fields of F-actin, we find that at low Arp2/3 concentrations, F-actin is organized into a single connected and contractile domain, while at elevated Arp2/3 levels (10 nM and above), such high-density actin domains fragment into smaller domains spanning a wide range of volumes. These fragmented domains are extremely dynamic, continuously merging and splitting, owing to the high treadmilling rate of the underlying actin network. Treating the domain dynamics as a drift-diffusion process, we find that the fragmented state is stochastically favored, and the network state slowly drifts toward the fragmented state with considerable diffusion (variability) in the number of domains. We suggest that tuning the Arp2/3 concentration enables cells to transition from a globally coherent cytoskeleton, whose response involves the entire cytoplasmic network, to a fragmented cytoskeleton, where domains can respond independently to locally varying signals.
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Affiliation(s)
- Aravind Chandrasekaran
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland; National Institutes of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Edward Giniger
- National Institutes of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Garegin A Papoian
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland; Institute for Physical Science and Technology, University of Maryland, College Park, Maryland.
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10
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Usuelli M, Ruzzi V, Buzzaccaro S, Nyström G, Piazza R, Mezzenga R. Unraveling gelation kinetics, arrested dynamics and relaxation phenomena in filamentous colloids by photon correlation imaging. SOFT MATTER 2022; 18:5632-5644. [PMID: 35861104 DOI: 10.1039/d1sm01578h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The fundamental understanding of the gelation kinetics, stress relaxation and temporal evolution in colloidal filamentous gels is central to many aspects of soft and biological matter, yet a complete description of the inherent complex dynamics of these systems is still missing. By means of photon correlation imaging (PCI), we studied the gelation of amyloid fibril solutions, chosen as a model filamentous colloid with immediate significance to biology and nanotechnology, upon passage of ions through a semi-permeable membrane. We observed a linear-in-time evolution of the gelation front and rich rearrangement dynamics of the gels, the magnitude and the spatial propagation of which depend on how effectively electrostatic interactions are screened by different ionic strengths. Our analysis confirms the pivotal role of salt concentration in tuning the properties of amyloid gels, and suggests potential routes for explaining the physical mechanisms behind the linear advance of the salt ions.
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Affiliation(s)
- Mattia Usuelli
- ETH Zürich, Department of Health Sciences and Technology, Schmelzbergstrasse 9, 8092 Zürich, Switzerland.
| | - Vincenzo Ruzzi
- Department of Chemistry, Materials Science, and Chemical Engineering (CMIC), Politecnico di Milano, Edificio 6, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
| | - Stefano Buzzaccaro
- Department of Chemistry, Materials Science, and Chemical Engineering (CMIC), Politecnico di Milano, Edificio 6, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
| | - Gustav Nyström
- ETH Zürich, Department of Health Sciences and Technology, Schmelzbergstrasse 9, 8092 Zürich, Switzerland.
- EMPA, Laboratory for Cellulose & Wood Materials, Überlandstrasse 129, 8600 Dübendorf, Switzerland
| | - Roberto Piazza
- Department of Chemistry, Materials Science, and Chemical Engineering (CMIC), Politecnico di Milano, Edificio 6, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
| | - Raffaele Mezzenga
- ETH Zürich, Department of Health Sciences and Technology, Schmelzbergstrasse 9, 8092 Zürich, Switzerland.
- ETH Zürich, Department of Materials, Wolfgang-Pauli-Strasse 10, 8093 Zürich, Switzerland
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11
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Abstract
Arrested soft materials such as gels and glasses exhibit a slow stress relaxation with a broad distribution of relaxation times in response to linear mechanical perturbations. Although this macroscopic stress relaxation is an essential feature in the application of arrested systems as structural materials, consumer products, foods, and biological materials, the microscopic origins of this relaxation remain poorly understood. Here, we elucidate the microscopic dynamics underlying the stress relaxation of such arrested soft materials under both quiescent and mechanically perturbed conditions through X-ray photon correlation spectroscopy. By studying the dynamics of a model associative gel system that undergoes dynamical arrest in the absence of aging effects, we show that the mean stress relaxation time measured from linear rheometry is directly correlated to the quiescent superdiffusive dynamics of the microscopic clusters, which are governed by a buildup of internal stresses during arrest. We also show that perturbing the system via small mechanical deformations can result in large intermittent fluctuations in the form of avalanches, which give rise to a broad non-Gaussian spectrum of relaxation modes at short times that is observed in stress relaxation measurements. These findings suggest that the linear viscoelastic stress relaxation in arrested soft materials may be governed by nonlinear phenomena involving an interplay of internal stress relaxations and perturbation-induced intermittent avalanches.
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12
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Santos-Sacchi J, Tan W. On the frequency response of prestin charge movement in membrane patches. Biophys J 2022; 121:2371-2379. [PMID: 35598044 PMCID: PMC9279172 DOI: 10.1016/j.bpj.2022.05.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 04/14/2022] [Accepted: 05/17/2022] [Indexed: 11/18/2022] Open
Abstract
Outer hair cell (OHC) nonlinear membrane capacitance derives from voltage-dependent sensor charge movements within the membrane protein prestin (SLC26a5) that drive OHC electromotility. The ability of the protein to influence hearing depends on its reaction to membrane receptor potentials across auditory frequency. Estimates of prestin's frequency response have been evaluated by several groups out to tens of kHz in voltage-clamped macro-patches of OHC membrane. The response is a power function of frequency that is down 40 dB at 77 kHz. Despite these observations, concerns remain that the macro-patch approach is flawed due to mechanical constraints of pipette solution column load or patch size itself. In the absence of these influences, prestin's frequency response is posited by some to be ultrasonic in nature. Here we evaluate the influence of these putative confounding factors on prestin's frequency response. We show that neither pipette column height nor negative or positive pipette pressure substantially influence total sensor charge frequency response. Additionally, patch surface area has negligible influence. We conclude that the speed of voltage-driven conformational changes in prestin within the plasma membrane is accurately assessed with the macro-patch technique, permitting investigations of membrane characteristics that can substantially alter prestin's performance bandwidth. We illustrate significant alterations in bandwidth by perturbation of membrane fluidity and chloride anion concentration. Finally, we speculate that OHC membrane characteristics may differ along the tonotopic axis of the cochlea to tune nonlinear membrane capacitance frequency cutoffs.
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Affiliation(s)
- Joseph Santos-Sacchi
- Surgery (Otolaryngology), Neuroscience, and Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut.
| | - Winston Tan
- Surgery (Otolaryngology), Neuroscience, and Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut
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13
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Araki T, Gomez-Solano JR, Maciołek A. Relaxation to steady states of a binary liquid mixture around an optically heated colloid. Phys Rev E 2022; 105:014123. [PMID: 35193287 DOI: 10.1103/physreve.105.014123] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 01/06/2022] [Indexed: 06/14/2023]
Abstract
We study the relaxation dynamics of a binary liquid mixture near a light-absorbing Janus particle after switching on and off illumination using experiments and theoretical models. The dynamics is controlled by the temperature gradient formed around the heated particle. Our results show that the relaxation is asymmetric: The approach to a nonequilibrium steady state is much slower than the return to thermal equilibrium. Approaching a nonequilibrium steady state after a sudden temperature change is a two-step process that overshoots the response of spatial variance of the concentration field. The initial growth of concentration fluctuations after switching on illumination follows a power law in agreement with the hydrodynamic and purely diffusive model. The energy outflow from the system after switching off illumination is well described by a stretched exponential function of time with characteristic time proportional to the ratio of the energy stored in the steady state to the total energy flux in this state.
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Affiliation(s)
- Takeaki Araki
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Juan Ruben Gomez-Solano
- Instituto de Física, Universidad Nacional Autónoma de Mexico, Ciudad de Mexico, Código Postal 04510, Mexico
| | - Anna Maciołek
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, PL-01-224 Warsaw, Poland
- Max-Planck-Institut für Intelligente Systeme Stuttgart, Heisenbergstraße 3, D-70569 Stuttgart, Germany
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14
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Wei X, Fang C, Gong B, Yao J, Qian J, Lin Y. Viscoelasticity of 3D actin networks dictated by the mechanochemical characteristics of cross-linkers. SOFT MATTER 2021; 17:10177-10185. [PMID: 33646227 DOI: 10.1039/d0sm01558j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
In this study, we report a computational investigation on how the mechanochemical characteristics of crosslinking molecules influence the viscoelasticity of three dimensional F-actin networks, an issue of key interest in analyzing the behavior of living cells and biological gels. In particular, it was found that the continuous breakage and rebinding of cross-linkers result in a locally peaked loss modulus in the rheology spectrum of the network, reflecting the fact that maximum energy dissipation is achieved when the driving frequency of the applied oscillating shear becomes comparable to the dissociation/association rate of crosslinking molecules. In addition, we showed that when subjected to constant rate of shear, an actin network can exhibit either strain hardening or softening depending on the ratio between the loading rate and unbinding speed of cross-linkers. A criterion for predicting the transition from softening to hardening was also obtained, in agreement with recent experiments. Finally, significant structural evolution was found to occur in random networks undergoing mechanical "training" (i.e. under a constant applied shear stress over a period of time), eventually leading to a pronounced anisotropic response of the network afterward which again is consistent with experimental observations.
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Affiliation(s)
- X Wei
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China.
- HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Guangdong, China
| | - C Fang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China.
- HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Guangdong, China
| | - B Gong
- Department of Engineering Mechanics, Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Hangzhou, Zhejiang, China.
| | - J Yao
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China.
- HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Guangdong, China
| | - J Qian
- Department of Engineering Mechanics, Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Hangzhou, Zhejiang, China.
| | - Y Lin
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China.
- HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Guangdong, China
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15
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Enhanced microscopic dynamics in mucus gels under a mechanical load in the linear viscoelastic regime. Proc Natl Acad Sci U S A 2021; 118:2103995118. [PMID: 34728565 DOI: 10.1073/pnas.2103995118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/19/2021] [Indexed: 12/24/2022] Open
Abstract
Mucus is a biological gel covering the surface of several tissues and ensuring key biological functions, including as a protective barrier against dehydration, pathogen penetration, or gastric acids. Mucus biological functioning requires a finely tuned balance between solid-like and fluid-like mechanical response, ensured by reversible bonds between mucins, the glycoproteins that form the gel. In living organisms, mucus is subject to various kinds of mechanical stresses, e.g., due to osmosis, bacterial penetration, coughing, and gastric peristalsis. However, our knowledge of the effects of stress on mucus is still rudimentary and mostly limited to macroscopic rheological measurements, with no insight into the relevant microscopic mechanisms. Here, we run mechanical tests simultaneously to measurements of the microscopic dynamics of pig gastric mucus. Strikingly, we find that a modest shear stress, within the macroscopic rheological linear regime, dramatically enhances mucus reorganization at the microscopic level, as signaled by a transient acceleration of the microscopic dynamics, by up to 2 orders of magnitude. We rationalize these findings by proposing a simple, yet general, model for the dynamics of physical gels under strain and validate its assumptions through numerical simulations of spring networks. These results shed light on the rearrangement dynamics of mucus at the microscopic scale, with potential implications in phenomena ranging from mucus clearance to bacterial and drug penetration.
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16
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A strong nonequilibrium bound for sorting of cross-linkers on growing biopolymers. Proc Natl Acad Sci U S A 2021; 118:2102881118. [PMID: 34518221 DOI: 10.1073/pnas.2102881118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/22/2021] [Indexed: 12/18/2022] Open
Abstract
Understanding the role of nonequilibrium driving in self-organization is crucial for developing a predictive description of biological systems, yet it is impeded by their complexity. The actin cytoskeleton serves as a paradigm for how equilibrium and nonequilibrium forces combine to give rise to self-organization. Motivated by recent experiments that show that actin filament growth rates can tune the morphology of a growing actin bundle cross-linked by two competing types of actin-binding proteins [S. L. Freedman et al., Proc. Natl. Acad. Sci. U.S.A. 116, 16192-16197 (2019)], we construct a minimal model for such a system and show that the dynamics of a growing actin bundle are subject to a set of thermodynamic constraints that relate its nonequilibrium driving, morphology, and molecular fluxes. The thermodynamic constraints reveal the importance of correlations between these molecular fluxes and offer a route to estimating microscopic driving forces from microscopy experiments.
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17
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Dey K, Roca E, Ramorino G, Sartore L. Progress in the mechanical modulation of cell functions in tissue engineering. Biomater Sci 2021; 8:7033-7081. [PMID: 33150878 DOI: 10.1039/d0bm01255f] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In mammals, mechanics at multiple stages-nucleus to cell to ECM-underlie multiple physiological and pathological functions from its development to reproduction to death. Under this inspiration, substantial research has established the role of multiple aspects of mechanics in regulating fundamental cellular processes, including spreading, migration, growth, proliferation, and differentiation. However, our understanding of how these mechanical mechanisms are orchestrated or tuned at different stages to maintain or restore the healthy environment at the tissue or organ level remains largely a mystery. Over the past few decades, research in the mechanical manipulation of the surrounding environment-known as substrate or matrix or scaffold on which, or within which, cells are seeded-has been exceptionally enriched in the field of tissue engineering and regenerative medicine. To do so, traditional tissue engineering aims at recapitulating key mechanical milestones of native ECM into a substrate for guiding the cell fate and functions towards specific tissue regeneration. Despite tremendous progress, a big puzzle that remains is how the cells compute a host of mechanical cues, such as stiffness (elasticity), viscoelasticity, plasticity, non-linear elasticity, anisotropy, mechanical forces, and mechanical memory, into many biological functions in a cooperative, controlled, and safe manner. High throughput understanding of key cellular decisions as well as associated mechanosensitive downstream signaling pathway(s) for executing these decisions in response to mechanical cues, solo or combined, is essential to address this issue. While many reports have been made towards the progress and understanding of mechanical cues-particularly, substrate bulk stiffness and viscoelasticity-in regulating the cellular responses, a complete picture of mechanical cues is lacking. This review highlights a comprehensive view on the mechanical cues that are linked to modulate many cellular functions and consequent tissue functionality. For a very basic understanding, a brief discussion of the key mechanical players of ECM and the principle of mechanotransduction process is outlined. In addition, this review gathers together the most important data on the stiffness of various cells and ECM components as well as various tissues/organs and proposes an associated link from the mechanical perspective that is not yet reported. Finally, beyond addressing the challenges involved in tuning the interplaying mechanical cues in an independent manner, emerging advances in designing biomaterials for tissue engineering are also explored.
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Affiliation(s)
- Kamol Dey
- Department of Applied Chemistry and Chemical Engineering, Faculty of Science, University of Chittagong, Bangladesh
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18
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Moazzeni S, Demiryurek Y, Yu M, Shreiber DI, Zahn JD, Shan JW, Foty RA, Liu L, Lin H. Single-cell mechanical analysis and tension quantification via electrodeformation relaxation. Phys Rev E 2021; 103:032409. [PMID: 33862816 PMCID: PMC10625872 DOI: 10.1103/physreve.103.032409] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 02/24/2021] [Indexed: 02/03/2023]
Abstract
The mechanical behavior and cortical tension of single cells are analyzed using electrodeformation relaxation. Four types of cells, namely, MCF-10A, MCF-7, MDA-MB-231, and GBM, are studied, with pulse durations ranging from 0.01 to 10 s. Mechanical response in the long-pulse regime is characterized by a power-law behavior, consistent with soft glassy rheology resulting from unbinding events within the cortex network. In the subsecond short-pulse regime, a single timescale well describes the process and indicates the naive tensioned (prestressed) state of the cortex with minimal force-induced alteration. A mathematical model is employed and the simple ellipsoidal geometry allows for use of an analytical solution to extract the cortical tension. At the shortest pulse of 0.01 s, tensions for all four cell types are on the order of 10^{-2} N/m.
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Affiliation(s)
- Seyedsajad Moazzeni
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854, USA
| | - Yasir Demiryurek
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854, USA
| | - Miao Yu
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854, USA
| | - David I. Shreiber
- Department of Biomedical Engineering, Rutgers, The State University of New Jersey, 599 Taylor Road, Piscataway, New Jersey 08854, USA
| | - Jeffrey D. Zahn
- Department of Biomedical Engineering, Rutgers, The State University of New Jersey, 599 Taylor Road, Piscataway, New Jersey 08854, USA
| | - Jerry W. Shan
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854, USA
| | - Ramsey A. Foty
- Department of Surgery, Rutgers, The State University of New Jersey, 125 Patterson Street, New Brunswick, New Jersey 08901, USA
| | - Liping Liu
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854, USA
- Department of Mathematics, Rutgers, The State University of New Jersey, 110 Frelinghuysen Road, Piscataway, New Jersey 08901, USA
| | - Hao Lin
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854, USA
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19
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Ono-Dit-Biot JC, Lorand T, Dalnoki-Veress K. Continuum Model Applied to Granular Analogs of Droplets and Puddles. PHYSICAL REVIEW LETTERS 2020; 125:228001. [PMID: 33315448 DOI: 10.1103/physrevlett.125.228001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 09/28/2020] [Accepted: 10/16/2020] [Indexed: 06/12/2023]
Abstract
We investigate the growth of aggregates made of adhesive frictionless oil droplets, piling up against a solid interface. Monodisperse droplets are produced one by one in an aqueous solution and float upward to the top of a liquid cell where they accumulate and form an aggregate at a flat horizontal interface. Initially, the aggregate grows in 3D until its height reaches a critical value. Beyond a critical height, adding more droplets results in the aggregate spreading in 2D along the interface with a constant height. We find that the shape of such aggregates, despite being granular in nature, is well described by a continuum model. The geometry of the aggregates is determined by a balance between droplet buoyancy and adhesion as given by a single parameter, a "granular" capillary length, analogous to the capillary length of a liquid.
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Affiliation(s)
- Jean-Christophe Ono-Dit-Biot
- Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4M1, Canada
| | - Tanel Lorand
- Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4M1, Canada
| | - Kari Dalnoki-Veress
- Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4M1, Canada
- UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 75005 Paris, France
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20
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Jung W, Li J, Chaudhuri O, Kim T. Nonlinear Elastic and Inelastic Properties of Cells. J Biomech Eng 2020; 142:100806. [PMID: 32253428 PMCID: PMC7477719 DOI: 10.1115/1.4046863] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Revised: 03/27/2020] [Indexed: 12/15/2022]
Abstract
Mechanical forces play an important role in various physiological processes, such as morphogenesis, cytokinesis, and migration. Thus, in order to illuminate mechanisms underlying these physiological processes, it is crucial to understand how cells deform and respond to external mechanical stimuli. During recent decades, the mechanical properties of cells have been studied extensively using diverse measurement techniques. A number of experimental studies have shown that cells are far from linear elastic materials. Cells exhibit a wide variety of nonlinear elastic and inelastic properties. Such complicated properties of cells are known to emerge from unique mechanical characteristics of cellular components. In this review, we introduce major cellular components that largely govern cell mechanical properties and provide brief explanations of several experimental techniques used for rheological measurements of cell mechanics. Then, we discuss the representative nonlinear elastic and inelastic properties of cells. Finally, continuum and discrete computational models of cell mechanics, which model both nonlinear elastic and inelastic properties of cells, will be described.
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Affiliation(s)
- Wonyeong Jung
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, West Lafayette, IN 47907
| | - Jing Li
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, West Lafayette, IN 47907
| | - Ovijit Chaudhuri
- Department of Mechanical Engineering, Stanford University, 440 Escondido Mall, Stanford, CA 94305
| | - Taeyoon Kim
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, West Lafayette, IN 47907
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21
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Bailey M, Alunni-Cardinali M, Correa N, Caponi S, Holsgrove T, Barr H, Stone N, Winlove CP, Fioretto D, Palombo F. Viscoelastic properties of biopolymer hydrogels determined by Brillouin spectroscopy: A probe of tissue micromechanics. SCIENCE ADVANCES 2020; 6:eabc1937. [PMID: 33127678 PMCID: PMC7608813 DOI: 10.1126/sciadv.abc1937] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 09/16/2020] [Indexed: 05/09/2023]
Abstract
Many problems in mechanobiology urgently require characterization of the micromechanical properties of cells and tissues. Brillouin light scattering has been proposed as an emerging optical elastography technique to meet this need. However, the information contained in the Brillouin spectrum is still a matter of debate because of fundamental problems in understanding the role of water in biomechanics and in relating the Brillouin data to low-frequency macroscopic mechanical parameters. Here, we investigate this question using gelatin as a model system in which the macroscopic physical properties can be manipulated to mimic all the relevant biological states of matter, ranging from the liquid to the gel and the glassy phase. We demonstrate that Brillouin spectroscopy is able to reveal both the elastic and viscous properties of biopolymers that are central to the structure and function of biological tissues.
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Affiliation(s)
- Michelle Bailey
- University of Exeter, School of Physics and Astronomy, Exeter EX4 4QL, UK
| | | | - Noemi Correa
- University of Exeter, School of Physics and Astronomy, Exeter EX4 4QL, UK
| | - Silvia Caponi
- CNR-IOM-Istituto Officina dei Materiali-Research Unit in Perugia, Department of Physics and Geology, University of Perugia, Perugia I-06123, Italy
| | | | - Hugh Barr
- Gloucestershire Royal Hospital, Gloucester GL1 3NN, UK
| | - Nick Stone
- University of Exeter, School of Physics and Astronomy, Exeter EX4 4QL, UK
| | - C Peter Winlove
- University of Exeter, School of Physics and Astronomy, Exeter EX4 4QL, UK
| | - Daniele Fioretto
- University of Perugia, Department of Physics and Geology, Perugia I-06123, Italy.
| | - Francesca Palombo
- University of Exeter, School of Physics and Astronomy, Exeter EX4 4QL, UK.
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22
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Chaubet L, Chaudhary AR, Heris HK, Ehrlicher AJ, Hendricks AG. Dynamic actin cross-linking governs the cytoplasm's transition to fluid-like behavior. Mol Biol Cell 2020; 31:1744-1752. [PMID: 32579489 PMCID: PMC7521843 DOI: 10.1091/mbc.e19-09-0504] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 06/05/2020] [Accepted: 06/16/2020] [Indexed: 12/21/2022] Open
Abstract
Cells precisely control their mechanical properties to organize and differentiate into tissues. The architecture and connectivity of cytoskeletal filaments change in response to mechanical and biochemical cues, allowing the cell to rapidly tune its mechanics from highly cross-linked, elastic networks to weakly cross-linked viscous networks. While the role of actin cross-linking in controlling actin network mechanics is well-characterized in purified actin networks, its mechanical role in the cytoplasm of living cells remains unknown. Here, we probe the frequency-dependent intracellular viscoelastic properties of living cells using multifrequency excitation and in situ optical trap calibration. At long timescales in the intracellular environment, we observe that the cytoskeleton becomes fluid-like. The mechanics are well-captured by a model in which actin filaments are dynamically connected by a single dominant cross-linker. A disease-causing point mutation (K255E) of the actin cross-linker α-actinin 4 (ACTN4) causes its binding kinetics to be insensitive to tension. Under normal conditions, the viscoelastic properties of wild-type (WT) and K255E+/- cells are similar. However, when tension is reduced through myosin II inhibition, WT cells relax 3× faster to the fluid-like regime while K255E+/- cells are not affected. These results indicate that dynamic actin cross-linking enables the cytoplasm to flow at long timescales.
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Affiliation(s)
- Loïc Chaubet
- Department of Bioengineering, McGill University, Montreal, QC H3A 0C3, Canada
| | | | - Hossein K. Heris
- Department of Bioengineering, McGill University, Montreal, QC H3A 0C3, Canada
| | - Allen J. Ehrlicher
- Department of Bioengineering, McGill University, Montreal, QC H3A 0C3, Canada
| | - Adam G. Hendricks
- Department of Bioengineering, McGill University, Montreal, QC H3A 0C3, Canada
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23
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Grad EM, Tunn I, Voerman D, de Léon AS, Hammink R, Blank KG. Influence of Network Topology on the Viscoelastic Properties of Dynamically Crosslinked Hydrogels. Front Chem 2020; 8:536. [PMID: 32719773 PMCID: PMC7349520 DOI: 10.3389/fchem.2020.00536] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 05/26/2020] [Indexed: 01/15/2023] Open
Abstract
Biological materials combine stress relaxation and self-healing with non-linear stress-strain responses. These characteristic features are a direct result of hierarchical self-assembly, which often results in fiber-like architectures. Even though structural knowledge is rapidly increasing, it has remained a challenge to establish relationships between microscopic and macroscopic structure and function. Here, we focus on understanding how network topology determines the viscoelastic properties, i.e., stress relaxation, of biomimetic hydrogels. We have dynamically crosslinked two different synthetic polymers with one and the same crosslink. The first polymer, a polyisocyanopeptide (PIC), self-assembles into semi-flexible, fiber-like bundles, and thus displays stress-stiffening, similar to many biopolymer networks. The second polymer, 4-arm poly(ethylene glycol) (starPEG), serves as a reference network with well-characterized structural and viscoelastic properties. Using one and the same coiled coil crosslink allows us to decouple the effects of crosslink kinetics and network topology on the stress relaxation behavior of the resulting hydrogel networks. We show that the fiber-containing PIC network displays a relaxation time approximately two orders of magnitude slower than the starPEG network. This reveals that crosslink kinetics is not the only determinant for stress relaxation. Instead, we propose that the different network topologies determine the ability of elastically active network chains to relax stress. In the starPEG network, each elastically active chain contains exactly one crosslink. In the absence of entanglements, crosslink dissociation thus relaxes the entire chain. In contrast, each polymer is crosslinked to the fiber bundle in multiple positions in the PIC hydrogel. The dissociation of a single crosslink is thus not sufficient for chain relaxation. This suggests that tuning the number of crosslinks per elastically active chain in combination with crosslink kinetics is a powerful design principle for tuning stress relaxation in polymeric materials. The presence of a higher number of crosslinks per elastically active chain thus yields materials with a slow macroscopic relaxation time but fast dynamics at the microscopic level. Using this principle for the design of synthetic cell culture matrices will yield materials with excellent long-term stability combined with the ability to locally reorganize, thus facilitating cell motility, spreading, and growth.
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Affiliation(s)
- Emilia M. Grad
- Mechano(bio) Chemistry, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
- Department of Molecular Materials, Institute for Molecules and Materials, Radboud University, Nijmegen, Netherlands
| | - Isabell Tunn
- Mechano(bio) Chemistry, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
| | - Dion Voerman
- Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
- Division of Immunotherapy, Oncode Institute, Radboud University Medical Center, Nijmegen, Netherlands
| | - Alberto S. de Léon
- Mechano(bio) Chemistry, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
| | - Roel Hammink
- Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
- Division of Immunotherapy, Oncode Institute, Radboud University Medical Center, Nijmegen, Netherlands
| | - Kerstin G. Blank
- Mechano(bio) Chemistry, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
- Department of Molecular Materials, Institute for Molecules and Materials, Radboud University, Nijmegen, Netherlands
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24
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Dallari F, Martinelli A, Caporaletti F, Sprung M, Grübel G, Monaco G. Microscopic pathways for stress relaxation in repulsive colloidal glasses. SCIENCE ADVANCES 2020; 6:eaaz2982. [PMID: 32219168 PMCID: PMC7083620 DOI: 10.1126/sciadv.aaz2982] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 12/12/2019] [Indexed: 05/27/2023]
Abstract
Residual stresses are well-known companions of all glassy materials. They affect and, in many cases, even strongly modify important material properties like the mechanical response and the optical transparency. The mechanisms through which stresses affect such properties are, in many cases, still under study, and their full understanding can pave the way to a full exploitation of stress as a primary control parameter. It is, for example, known that stresses promote particle mobility at small length scales, e.g., in colloidal glasses, gels, and metallic glasses, but this connection still remains essentially qualitative. Exploiting a preparation protocol that leads to colloidal glasses with an exceptionally directional built-in stress field, we characterize the stress-induced dynamics and show that it can be visualized as a collection of "flickering," mobile regions with linear sizes of the order of ≈20 particle diameters (≈2 μm here) that move cooperatively, displaying an overall stationary but locally ballistic dynamics.
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Affiliation(s)
- F. Dallari
- Dipartimento di Fisica, Università di Trento, I-38123 Povo (Trento), Italy
| | - A. Martinelli
- Dipartimento di Fisica, Università di Trento, I-38123 Povo (Trento), Italy
| | - F. Caporaletti
- Dipartimento di Fisica, Università di Trento, I-38123 Povo (Trento), Italy
| | - M. Sprung
- Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany
| | - G. Grübel
- Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany
| | - G. Monaco
- Dipartimento di Fisica, Università di Trento, I-38123 Povo (Trento), Italy
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25
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Wang L, Cheng L, Li G, Liu K, Zhang Z, Li P, Dong S, Yu W, Huang F, Yan X. A Self-Cross-Linking Supramolecular Polymer Network Enabled by Crown-Ether-Based Molecular Recognition. J Am Chem Soc 2020; 142:2051-2058. [PMID: 31905287 DOI: 10.1021/jacs.9b12164] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Supramolecular polymers based on host-guest molecular recognition have emerged as promising platforms for the development of smart materials. However, the studies on them are primarily conducted in solution and/or in the gel state. In contrast, little is known about dynamic properties and applications of supramolecular polymers in bulk. Herein, we present a self-cross-linking supramolecular polymer network (SPN) as a model system to understand the bulk properties controlled by noncovalent interactions. Specifically, the SPN monomer is composed of two benzo-21-crown-7 (B21C7) host units and two dialkylammonium salt guest moieties on a four-arm core, wherein complementary host-guest complexation drives the formation of the SPN with [2]pseudorotaxane linkages between B21C7 and ammonium motifs. The dynamic and reversible behaviors of the linkages are evaluated by measurement of viscoelasticity. The results indicate that the host-guest molecular recognition becomes highly dynamic at elevated temperature. Moreover, the relatively high activation energy of the SPN manifests itself as a new type of thermoplastic material with network topology freezing glass transition. Finally, we demonstrate how these findings provide insights into the malleability and processability of the SPN by simple demos. The fundamental understanding gained from the research on this SPN in bulk will facilitate the advancement and application of supramolecular materials.
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Affiliation(s)
- Lei Wang
- School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules , Shanghai Jiao Tong University , Shanghai 200240 , People's Republic of China
| | - Lin Cheng
- School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules , Shanghai Jiao Tong University , Shanghai 200240 , People's Republic of China
| | - Guangfeng Li
- School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules , Shanghai Jiao Tong University , Shanghai 200240 , People's Republic of China
| | - Kai Liu
- School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules , Shanghai Jiao Tong University , Shanghai 200240 , People's Republic of China
| | - Zhaoming Zhang
- School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules , Shanghai Jiao Tong University , Shanghai 200240 , People's Republic of China
| | - Peitong Li
- School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules , Shanghai Jiao Tong University , Shanghai 200240 , People's Republic of China
| | - Shengyi Dong
- College of Chemistry and Chemical Engineering , Hunan University , Changsha 410082 , People's Republic of China
| | - Wei Yu
- School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules , Shanghai Jiao Tong University , Shanghai 200240 , People's Republic of China
| | - Feihe Huang
- State Key Laboratory of Chemical Engineering, Center for Chemistry of High-Performance & Novel Materials, Department of Chemistry , Zhejiang University , Hangzhou 310027 , People's Republic of China
| | - Xuzhou Yan
- School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules , Shanghai Jiao Tong University , Shanghai 200240 , People's Republic of China
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26
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Elizondo-Aguilera LF, Voigtmann T. Glass-transition asymptotics in two theories of glassy dynamics: Self-consistent generalized Langevin equation and mode-coupling theory. Phys Rev E 2019; 100:042601. [PMID: 31770981 DOI: 10.1103/physreve.100.042601] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Indexed: 11/07/2022]
Abstract
We contrast the generic features of structural relaxation close to the idealized glass transition that are predicted by the self-consistent generalized Langevin equation theory (SCGLE) against those that are predicted by the mode-coupling theory of the glass transition (MCT). We present an asymptotic solution close to conditions of kinetic arrest that is valid for both theories, despite the different starting points that are adopted in deriving them. This in particular provides the same level of understanding of the asymptotic dynamics in the SCGLE as was previously done only for MCT. We discuss similarities and different predictions of the two theories for kinetic arrest in standard glass-forming models, as exemplified through the hard-sphere system. Qualitative differences are found for models where a decoupling of relaxation modes is predicted, such as the generalized Gaussian core model, or binary hard-sphere mixtures of particles with very disparate sizes. These differences, which arise in the distinct treatment of the memory kernels associated to self- and collective motion of particles, lead to distinct scenarios that are predicted by each theory for partially arrested states and in the vicinity of higher-order glass-transition singularities.
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Affiliation(s)
- L F Elizondo-Aguilera
- Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln, Germany
| | - Th Voigtmann
- Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln, Germany.,Department of Physics, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany
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27
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Bai JP, Navaratnam D, Santos-Sacchi J. Prestin kinetics and corresponding frequency dependence augment during early development of the outer hair cell within the mouse organ of Corti. Sci Rep 2019; 9:16460. [PMID: 31712635 PMCID: PMC6848539 DOI: 10.1038/s41598-019-52965-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 10/25/2019] [Indexed: 12/23/2022] Open
Abstract
Several studies have documented the early development of OHC electromechanical behavior. The mechanical response (electromotility, eM) and its electrical correlate (nonlinear capacitance, NLC), resulting from prestin's voltage-sensor charge movement, increase over the course of several postnatal days in altricial animals. They increase until about p18, near the time of peripheral auditory maturity. The correspondence of auditory capabilities and prestin function indicates that mature activity of prestin occurs at this time. One of the major requirements of eM is its responsiveness across auditory frequencies. Here we evaluate the frequency response of prestin charge movement in mice over the course of development up to 8 months. We find that in apical turn OHCs prestin's frequency response increases during postnatal development and stabilizes when mature hearing is established. The low frequency component of NLC, within in situ explants, agrees with previously reported results on isolated cells. If prestin activity is independent of cochlear place, as might be expected, then these observations suggest that prestin activity somehow influences cochlear amplification at high frequencies in spite of its low pass behavior.
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Affiliation(s)
- Jun-Ping Bai
- Department of Neurology, Yale University School of Medicine, 333 Cedar St, New Haven CT, USA
| | - Dhasakumar Navaratnam
- Department of Surgery (Otolaryngology), Yale University School of Medicine, 333 Cedar St, New Haven CT, USA.,Department of Neuroscience, Yale University School of Medicine, 333 Cedar St, New Haven CT, USA.,Department of Neurology, Yale University School of Medicine, 333 Cedar St, New Haven CT, USA
| | - Joseph Santos-Sacchi
- Department of Surgery (Otolaryngology), Yale University School of Medicine, 333 Cedar St, New Haven CT, USA. .,Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar St, New Haven CT, USA. .,Department of Neuroscience, Yale University School of Medicine, 333 Cedar St, New Haven CT, USA.
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28
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Alvarado J, Cipelletti L, Koenderink GH. Uncovering the dynamic precursors to motor-driven contraction of active gels. SOFT MATTER 2019; 15:8552-8565. [PMID: 31637398 DOI: 10.1039/c9sm01172b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Cells and tissues have the remarkable ability to actively generate the forces required to change their shape. This active mechanical behavior is largely mediated by the actin cytoskeleton, a crosslinked network of actin filaments that is contracted by myosin motors. Experiments and active gel theories have established that the length scale over which gel contraction occurs is governed by a balance between molecular motor activity and crosslink density. By contrast, the dynamics that govern the contractile activity of the cytoskeleton remain poorly understood. Here we investigate the microscopic dynamics of reconstituted actin-myosin networks using simultaneous real-space video microscopy and Fourier-space dynamic light scattering. Light scattering reveals different regimes of microscopic dynamics as a function of sample age. We uncover two dynamical precursors that precede macroscopic gel contraction. One is characterized by a progressive acceleration of stress-induced rearrangements, while the other consists of sudden, heterogeneous rearrangements. Intriguingly, our findings suggest a qualitative analogy between self-driven rupture and collapse of active gels and the delayed rupture of passive gels observed in earlier studies of colloidal gels under external loads.
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Affiliation(s)
- José Alvarado
- AMOLF, Living Matter Department, 1098 XG Amsterdam, The Netherlands.
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29
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Filiberti Z, Piazza R, Buzzaccaro S. Multiscale relaxation in aging colloidal gels: From localized plastic events to system-spanning quakes. Phys Rev E 2019; 100:042607. [PMID: 31770945 DOI: 10.1103/physreve.100.042607] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Indexed: 06/10/2023]
Abstract
Relaxation of internal stresses through a cascade of microscopic restructuring events is the hallmark of many materials, ranging from amorphous solids like glasses and gels to geological structures subjected to a persistent external load. By means of photon correlation imaging, a recently developed technique that blends the powers of scattering and imaging, we provide a spatially and temporally resolved survey of the restructuring and aging processes that spontaneously occur in physical gels originating from an arrested phase separation. We show that the temporal dynamics is characterized by an intermittent sequence of spatially localized "microquakes" that eventually lead to global rearrangements occurring at a rate that scales with the gel age. Notably, these dramatic upheavals of the gel structure are heralded by a progressive acceleration of the microscopic gel dynamics that originates from recognizable active spots and then spreads at a large but finite speed through the gel. Within the "slack" phase between two of these "macroquakes," the fluctuations of the degree of temporal correlation obey a non-Gaussian statistics described by a generalized logistic distribution. The evidence we obtained bear consistent analogies with the stress relaxation processes taking place in earthquake sequences and with the intermittent restructuring of plastic crystals at the microscale.
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Affiliation(s)
- Zeno Filiberti
- Department of Chemistry, Materials Science, and Chemical Engineering (CMIC), Politecnico di Milano, Edificio 6, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Roberto Piazza
- Department of Chemistry, Materials Science, and Chemical Engineering (CMIC), Politecnico di Milano, Edificio 6, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Stefano Buzzaccaro
- Department of Chemistry, Materials Science, and Chemical Engineering (CMIC), Politecnico di Milano, Edificio 6, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
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30
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Single-crosslink microscopy in a biopolymer network dissects local elasticity from molecular fluctuations. Nat Commun 2019; 10:3314. [PMID: 31346168 PMCID: PMC6658493 DOI: 10.1038/s41467-019-11313-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 07/04/2019] [Indexed: 11/08/2022] Open
Abstract
Polymer networks are fundamental from cellular biology to plastics technology but their intrinsic inhomogeneity is masked by the usual ensemble-averaged measurements. Here, we construct direct maps of crosslinks—symbolic depiction of spatially-distributed elements highlighting their physical features and the relationships between them—in an actin network. We selectively label crosslinks with fluorescent markers, track their thermal fluctuations, and characterize the local elasticity and cross-correlations between crosslinks. Such maps display massive heterogeneity, reveal abundant anticorrelations, and may contribute to address how local responses scale up to produce macroscopic elasticity. Single-crosslink microscopy offers a general, microscopic framework to better understand crosslinked molecular networks in undeformed or strained states. The intrinsic inhomogeneity of polymer networks is masked by the usual ensemble-averaged measurements. Here the authors construct direct maps of crosslinks in an actin network by selective labeling the crosslinks with fluorescent markers and characterize the local elasticity and cross-correlation between crosslinks.
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31
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Mulla Y, MacKintosh FC, Koenderink GH. Origin of Slow Stress Relaxation in the Cytoskeleton. PHYSICAL REVIEW LETTERS 2019; 122:218102. [PMID: 31283330 DOI: 10.1103/physrevlett.122.218102] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 04/26/2019] [Indexed: 06/09/2023]
Abstract
Dynamically cross-linked semiflexible biopolymers such as the actin cytoskeleton govern the mechanical behavior of living cells. Semiflexible biopolymers nonlinearly stiffen in response to mechanical loads, whereas the cross-linker dynamics allow for stress relaxation over time. Here we show, through rheology and theoretical modeling, that the combined nonlinearity in time and stress leads to an unexpectedly slow stress relaxation, similar to the dynamics of disordered systems close to the glass transition. Our work suggests that transient cross-linking combined with internal stress can explain prior reports of soft glassy rheology of cells, in which the shear modulus increases weakly with frequency.
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Affiliation(s)
- Yuval Mulla
- Living Matter Department, AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - F C MacKintosh
- Departments of Chemical & Biomolecular Engineering, Chemistry, and Physics & Astronomy, Rice University, Houston, Texas 77005, USA
- Center for Theoretical Biological Physics, Rice University, Houston, Texas 77030, USA
- Department of Physics and Astronomy, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
| | - Gijsje H Koenderink
- Living Matter Department, AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
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32
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Miwa Y, Taira K, Kurachi J, Udagawa T, Kutsumizu S. A gas-plastic elastomer that quickly self-heals damage with the aid of CO 2 gas. Nat Commun 2019; 10:1828. [PMID: 31015450 PMCID: PMC6478687 DOI: 10.1038/s41467-019-09826-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 04/02/2019] [Indexed: 12/12/2022] Open
Abstract
Self-healing materials are highly desirable because they allow products to maintain their performance. Typical stimuli used for self-healing are heat and light, despite being unsuitable for materials used in certain products as heat can damage other components, and light cannot reach materials located within a product or device. To address these issues, here we show a gas-plastic elastomer with an ionically crosslinked silicone network that quickly self-heals damage in the presence of CO2 gas at normal pressures and room temperature. While a strong elastomer generally exhibits slow self-healing properties, CO2 effectively softened ionic crosslinks in the proposed elastomer, and network rearrangement was promoted. Consequently, self-healing was dramatically accelerated by ~10-fold. Moreover, self-healing was achieved even at -20 °C in the presence of CO2 and the original mechanical strength was quickly re-established during the exchange of CO2 with air.
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Affiliation(s)
- Yohei Miwa
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu, 501-1193, Japan.
| | - Kenjiro Taira
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu, 501-1193, Japan
| | - Junosuke Kurachi
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu, 501-1193, Japan
| | - Taro Udagawa
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu, 501-1193, Japan
| | - Shoichi Kutsumizu
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu, 501-1193, Japan
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33
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Impact of Nanoparticle Uptake on the Biophysical Properties of Cell for Biomedical Engineering Applications. Sci Rep 2019; 9:5859. [PMID: 30971727 PMCID: PMC6458124 DOI: 10.1038/s41598-019-42225-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 12/21/2018] [Indexed: 12/25/2022] Open
Abstract
Nanomaterials are currently the state-of-the-art in the development of advanced biomedical devices and applications where classical approaches have failed. To date, majority of the literature on nanomaterial interaction with cells have largely focused on the biological responses of cells obtained via assays, with little interest on their biophysical responses. However, recent studies have shown that the biophysical responses of cells, such as stiffness and adhesive properties, play a significant role in their physiological function. In this paper, we investigate cell biophysical responses after uptake of nanoparticles. Atomic force microscopy was used to study changes in cell stiffness and adhesion upon boron nitride (BN) and hydroxyapatite (HAP) nanoparticle uptake. Results show increase in cell stiffness with varying nanoparticle (BN and HAP) concentration, while a decrease in cell adhesion trigger by uptake of HAP. In addition, changes in the biochemical response of the cell membrane were observed via Raman spectroscopy of nanoparticle treated cells. These findings have significant implications in biomedical applications of nanoparticles, e.g. in drug delivery, advanced prosthesis and surgical implants.
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34
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Ma S, Scaraggi M, Yan C, Wang X, Gorb SN, Dini D, Zhou F. Bioinspired 3D Printed Locomotion Devices Based on Anisotropic Friction. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1802931. [PMID: 30444553 DOI: 10.1002/smll.201802931] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 10/10/2018] [Indexed: 06/09/2023]
Abstract
Anisotropic friction plays a key role in natural systems, particularly for realizing the purpose of locomotion and strong attachment for the survival of organisms. Of particular interest, here, is the observation that friction anisotropy is promoted numerous times by nature, for example, by wild wheat awn for its targeted and successful seed anchorage and dispersal. Such feature is, however, not fully exploited in man-made systems, such as microbots, due to technical limitations and lack of full understanding of the mechanisms. To unravel the complex dynamics occurring in the sliding interaction between anisotropic microstructured surfaces, the friction induced by asymmetric plant microstructures is first systematically investigated. Inspired by this, anisotropic polymer microactuators with three-dimensional (3D) printed microrelieves are then prepared. By varying geometric parameters, the capability of microactuators to generate strong friction anisotropy and controllable motion in remotely stretched cylindrical tubes is investigated. Advanced theoretical models are proposed to understand and predict the dynamic behavior of these synthetic systems and to shed light on the parameters and mechanisms governing their behavior. Finally, a microbot prototype is developed and cargo transportation functions are successfully realized. This research provides both in-depth understanding of anisotropic friction in nature and new avenues for developing intelligent actuators and microbots.
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Affiliation(s)
- Shuanhong Ma
- State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Michele Scaraggi
- Department of Engineering for Innovation, Universitá del Salento, 73100 Monteroni-Lecce, Italy
- Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, UK
| | - Changyou Yan
- State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
- University of the Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaolong Wang
- State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Stanislav N Gorb
- Department of Functional Morphology and Biomechanics, Zoological Institute, Kiel University, 24118, Kiel, Germany
| | - Daniele Dini
- Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, UK
| | - Feng Zhou
- State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
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35
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Cheng LC, Godfrin PD, Swan JW, Doyle PS. Thermal processing of thermogelling nanoemulsions as a route to tune material properties. SOFT MATTER 2018; 14:5604-5614. [PMID: 29923590 DOI: 10.1039/c8sm00814k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Many soft matter systems have properties which depend on their processing history. It is generally accepted that material properties can be finely tuned by carefully directing self-assembly. However, for gelling colloidal systems, it is difficult to characterize such path-dependent effects since the colloidal attraction is often provided by adding another component to the system such as salts or depletants. Therefore, studies of and an understanding of the role of processing on the material properties of attractive colloidal systems are largely lacking. In this work, we systematically studied how processing greatly influences the properties and the microstructures of model attractive colloidal systems. We perform experiments using a thermogelling nanoemulsion as a model system where the isotropic attraction can be precisely tuned via the temperature. The effects of processing conditions on gel formation and properties is tested by performing well-designed sequential temperature jumps. By properly controlling the thermal history, we demonstrate that properties of colloidal gels can be beyond the limit set by direct quenching, which has been a major focus in literature, and that otherwise slow aging of the system associated with a decrease in elasticity can be prevented. Our results provide new experimental evidence of path-dependent rheology and associated microstructures in attractive colloidal systems and provide guidance to future applications in manufacturing complex colloid-based materials.
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Affiliation(s)
- Li-Chiun Cheng
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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36
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Philippe AM, Truzzolillo D, Galvan-Myoshi J, Dieudonné-George P, Trappe V, Berthier L, Cipelletti L. Glass transition of soft colloids. Phys Rev E 2018; 97:040601. [PMID: 29758608 DOI: 10.1103/physreve.97.040601] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Indexed: 11/07/2022]
Abstract
We explore the glassy dynamics of soft colloids using microgels and charged particles interacting by steric and screened Coulomb interactions, respectively. In the supercooled regime, the structural relaxation time τ_{α} of both systems grows steeply with volume fraction, reminiscent of the behavior of colloidal hard spheres. Computer simulations confirm that the growth of τ_{α} on approaching the glass transition is independent of particle softness. By contrast, softness becomes relevant at very large packing fractions when the system falls out of equilibrium. In this nonequilibrium regime, τ_{α} depends surprisingly weakly on packing fraction, and time correlation functions exhibit a compressed exponential decay consistent with stress-driven relaxation. The transition to this novel regime coincides with the onset of an anomalous decrease in local order with increasing density typical of ultrasoft systems. We propose that these peculiar dynamics results from the combination of the nonequilibrium aging dynamics expected in the glassy state and the tendency of colloids interacting through soft potentials to refluidize at high packing fractions.
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Affiliation(s)
- Adrian-Marie Philippe
- Laboratoire Charles Coulomb (L2C), University of Montpellier, CNRS, Montpellier, France
| | - Domenico Truzzolillo
- Laboratoire Charles Coulomb (L2C), University of Montpellier, CNRS, Montpellier, France
| | | | | | - Véronique Trappe
- Department of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland
| | - Ludovic Berthier
- Laboratoire Charles Coulomb (L2C), University of Montpellier, CNRS, Montpellier, France
| | - Luca Cipelletti
- Laboratoire Charles Coulomb (L2C), University of Montpellier, CNRS, Montpellier, France
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37
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Affiliation(s)
- Fanlong Meng
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP, U.K
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Eugene M. Terentjev
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K
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38
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Lorenz JS, Schnauß J, Glaser M, Sajfutdinow M, Schuldt C, Käs JA, Smith DM. Synthetic Transient Crosslinks Program the Mechanics of Soft, Biopolymer-Based Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1706092. [PMID: 29446165 PMCID: PMC5878933 DOI: 10.1002/adma.201706092] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 12/20/2017] [Indexed: 05/21/2023]
Abstract
Actin networks are adaptive materials enabling dynamic and static functions of living cells. A central element for tuning their underlying structural and mechanical properties is the ability to reversibly connect, i.e., transiently crosslink, filaments within the networks. Natural crosslinkers, however, vary across many parameters. Therefore, systematically studying the impact of their fundamental properties like size and binding strength is unfeasible since their structural parameters cannot be independently tuned. Herein, this problem is circumvented by employing a modular strategy to construct purely synthetic actin crosslinkers from DNA and peptides. These crosslinkers mimic both intuitive and noncanonical mechanical properties of their natural counterparts. By isolating binding affinity as the primary control parameter, effects on structural and dynamic behaviors of actin networks are characterized. A concentration-dependent triphasic behavior arises from both strong and weak crosslinkers due to emergent structural polymorphism. Beyond a certain threshold, strong binding leads to a nonmonotonic elastic pulse, which is a consequence of self-destruction of the mechanical structure of the underlying network. The modular design also facilitates an orthogonal regulatory mechanism based on enzymatic cleaving. This approach can be used to guide the rational design of further biomimetic components for programmable modulation of the properties of biomaterials and cells.
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Affiliation(s)
- Jessica S Lorenz
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), 04103, Leipzig, Germany
| | - Jörg Schnauß
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), 04103, Leipzig, Germany
- Peter Debye Institute for Soft Matter Physics, Leipzig University, 04103, Leipzig, Germany
| | - Martin Glaser
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), 04103, Leipzig, Germany
- Peter Debye Institute for Soft Matter Physics, Leipzig University, 04103, Leipzig, Germany
| | - Martin Sajfutdinow
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), 04103, Leipzig, Germany
| | - Carsten Schuldt
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), 04103, Leipzig, Germany
- Peter Debye Institute for Soft Matter Physics, Leipzig University, 04103, Leipzig, Germany
| | - Josef A Käs
- Peter Debye Institute for Soft Matter Physics, Leipzig University, 04103, Leipzig, Germany
| | - David M Smith
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), 04103, Leipzig, Germany
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39
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Bouzid M, Del Gado E. Network Topology in Soft Gels: Hardening and Softening Materials. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:773-781. [PMID: 28977748 DOI: 10.1021/acs.langmuir.7b02944] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The structural complexity of soft gels is at the origin of a versatile mechanical response that allows for large deformation, controlled elastic recovery, and toughness in the same material. A limit to exploiting the potential of such materials is the insufficient fundamental understanding of the microstructural origin of the bulk mechanical properties. Here we investigate the role of the network topology in a model gel through 3D numerical simulations. Our study links the topology of the network organization in space to its nonlinear rheological response preceding yielding and damage: our analysis elucidates how the network connectivity alone could be used to modify the gel mechanics at large strains, from strain-softening to hardening and even to a brittle response. These findings provide new insight for smart material design and for understanding the nontrivial mechanical response of a potentially wide range of technologically relevant materials.
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Affiliation(s)
- Mehdi Bouzid
- Department of Physics and Institute for Soft Matter Synthesis and Metrology, Georgetown University , Washington, DC 20057, United States
| | - Emanuela Del Gado
- Department of Physics and Institute for Soft Matter Synthesis and Metrology, Georgetown University , Washington, DC 20057, United States
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40
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Moghimi E, Jacob AR, Petekidis G. Residual stresses in colloidal gels. SOFT MATTER 2017; 13:7824-7833. [PMID: 29028062 DOI: 10.1039/c7sm01655g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A combination of experiments and Brownian Dynamics (BD) simulations is utilized to examine internal stresses in colloidal gels brought to rest from steady shear at different shear rates. A model colloidal gel with intermediate volume fraction is chosen where attractions between particles are introduced by adding non-adsorbing linear polymer chains. After flow cessation, the gel releases the stress in two distinct patterns: at high shear rates, where shear forces dominate over attractive forces, the shear-melted gel behaves as a liquid and releases stresses to zero after flow cessation. After low shear rates, though, stresses relax only partially, similar to the response of hard sphere glasses and jammed soft particles. The balance between shear and attractive forces which determines the intensity of structural distortion controls the amplitude of the residual stresses through a universal scaling. Stress decomposition to repulsive and attractive contributions in BD simulations reveals that internal stresses mainly originate from attractive forces. Moreover, analysis of particle dynamics indicates that internal stresses are associated with sub-diffusive particle displacements on average smaller than the attraction range as such short-range displacements are not sufficient to completely erase structural anisotropy caused during the course of shear.
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Affiliation(s)
- Esmaeel Moghimi
- FORTH/IESL and Department of Materials Science and Technology, University of Crete, 71110 Heraklion, Greece.
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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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Affiliation(s)
- Adrian-Marie Philippe
- Laboratoire
Charles Coulomb, UMR 5221, Université de Montpellier and CNRS, 34095 Montpellier, France
| | - Luca Cipelletti
- Laboratoire
Charles Coulomb, UMR 5221, Université de Montpellier and CNRS, 34095 Montpellier, France
| | - Domenico Larobina
- Institute
for Polymers, Composites and Biomaterials, National Research Council of Italy, P.le E. Fermi 1, Naples, 80055 Portici, Italy
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Alvarado J, Sheinman M, Sharma A, MacKintosh FC, Koenderink GH. Force percolation of contractile active gels. SOFT MATTER 2017; 13:5624-5644. [PMID: 28812094 DOI: 10.1039/c7sm00834a] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Living systems provide a paradigmatic example of active soft matter. Cells and tissues comprise viscoelastic materials that exert forces and can actively change shape. This strikingly autonomous behavior is powered by the cytoskeleton, an active gel of semiflexible filaments, crosslinks, and molecular motors inside cells. Although individual motors are only a few nm in size and exert minute forces of a few pN, cells spatially integrate the activity of an ensemble of motors to produce larger contractile forces (∼nN and greater) on cellular, tissue, and organismal length scales. Here we review experimental and theoretical studies on contractile active gels composed of actin filaments and myosin motors. Unlike other active soft matter systems, which tend to form ordered patterns, actin-myosin systems exhibit a generic tendency to contract. Experimental studies of reconstituted actin-myosin model systems have long suggested that a mechanical interplay between motor activity and the network's connectivity governs this contractile behavior. Recent theoretical models indicate that this interplay can be understood in terms of percolation models, extended to include effects of motor activity on the network connectivity. Based on concepts from percolation theory, we propose a state diagram that unites a large body of experimental observations. This framework provides valuable insights into the mechanisms that drive cellular shape changes and also provides design principles for synthetic active materials.
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Affiliation(s)
- José Alvarado
- Systems Biophysics Department, AMOLF, 1098 XG Amsterdam, The Netherlands.
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Bouzid M, Colombo J, Barbosa LV, Del Gado E. Elastically driven intermittent microscopic dynamics in soft solids. Nat Commun 2017. [PMID: 28635964 PMCID: PMC5482056 DOI: 10.1038/ncomms15846] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Soft solids with tunable mechanical response are at the core of new material technologies, but a crucial limit for applications is their progressive aging over time, which dramatically affects their functionalities. The generally accepted paradigm is that such aging is gradual and its origin is in slower than exponential microscopic dynamics, akin to the ones in supercooled liquids or glasses. Nevertheless, time- and space-resolved measurements have provided contrasting evidence: dynamics faster than exponential, intermittency and abrupt structural changes. Here we use 3D computer simulations of a microscopic model to reveal that the timescales governing stress relaxation, respectively, through thermal fluctuations and elastic recovery are key for the aging dynamics. When thermal fluctuations are too weak, stress heterogeneities frozen-in upon solidification can still partially relax through elastically driven fluctuations. Such fluctuations are intermittent, because of strong correlations that persist over the timescale of experiments or simulations, leading to faster than exponential dynamics.
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Affiliation(s)
- Mehdi Bouzid
- Department of Physics, Institute for Soft Matter Synthesis and Metrology, Georgetown University, 37th and O Streets, N.W., Washington District Of Columbia 20057, USA
| | - Jader Colombo
- Department of Physics, Institute for Soft Matter Synthesis and Metrology, Georgetown University, 37th and O Streets, N.W., Washington District Of Columbia 20057, USA
| | - Lucas Vieira Barbosa
- Department of Physics, Institute for Soft Matter Synthesis and Metrology, Georgetown University, 37th and O Streets, N.W., Washington District Of Columbia 20057, USA.,CAPES Foundation, Ministry of Education of Brazil, Brasilia - DF 70.040-020, Brazil
| | - Emanuela Del Gado
- Department of Physics, Institute for Soft Matter Synthesis and Metrology, Georgetown University, 37th and O Streets, N.W., Washington District Of Columbia 20057, USA
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Chremos A, Douglas JF. Particle localization and hyperuniformity of polymer-grafted nanoparticle materials. ANNALEN DER PHYSIK 2017; 529:1600342. [PMID: 28690334 PMCID: PMC5497478 DOI: 10.1002/andp.201600342] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2016] [Accepted: 01/16/2017] [Indexed: 05/28/2023]
Abstract
The properties of materials largely reflect the degree and character of the localization of the molecules comprising them so that the study and characterization of particle localization has central significance in both fundamental science and material design. Soft materials are often comprised of deformable molecules and many of their unique properties derive from the distinct nature of particle localization. We study localization in a model material composed of soft particles, hard nanoparticles with grafted layers of polymers, where the molecular characteristics of the grafted layers allow us to "tune" the softness of their interactions. Soft particles are particular interesting because spatial localization can occur such that density fluctuations on large length scales are suppressed, while the material is disordered at intermediate length scales; such materials are called "disordered hyperuniform". We use molecular dynamics simulation to study a liquid composed of polymer-grafted nanoparticles (GNP), which exhibit a reversible self-assembly into dynamic polymeric GNP structures below a temperature threshold, suggesting a liquid-gel transition. We calculate a number of spatial and temporal correlations and we find a significant suppression of density fluctuations upon cooling at large length scales, making these materials promising for the practical fabrication of "hyperuniform" materials.
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Affiliation(s)
- Alexandros Chremos
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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Pastore R, Pesce G, Sasso A, Pica Ciamarra M. Cage Size and Jump Precursors in Glass-Forming Liquids: Experiment and Simulations. J Phys Chem Lett 2017; 8:1562-1568. [PMID: 28301929 DOI: 10.1021/acs.jpclett.7b00187] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Glassy dynamics is intermittent, as particles suddenly jump out of the cage formed by their neighbors, and heterogeneous, as these jumps are not uniformly distributed across the system. Relating these features of the dynamics to the diverse local environments explored by the particles is essential to rationalize the relaxation process. Here we investigate this issue characterizing the local environment of a particle with the amplitude of its short time vibrational motion, as determined by segmenting in cages and jumps the particle trajectories. Both simulations of supercooled liquids and experiments on colloidal suspensions show that particles in large cages are likely to jump after a small time-lag, and that, on average, the cage enlarges shortly before the particle jumps. At large time-lags, the cage has essentially a constant size, which is smaller for longer-lasting cages. Finally, we clarify how this coupling between cage size and duration controls the average behavior and opens the way to a better understanding of the relaxation process in glass-forming liquids.
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Affiliation(s)
- Raffaele Pastore
- CNR-SPIN, sezione di Napoli, Dipartimento di Fisica, Campus universitario di Monte S. Angelo, Via Cintia, 80126 Napoli, Italy
| | - Giuseppe Pesce
- Dipartimento di Fisica, Universitá di Napoli Federico II, Campus universitario di Monte S. Angelo, Via Cintia, 80126 Napoli, Italy
| | - Antonio Sasso
- Dipartimento di Fisica, Universitá di Napoli Federico II, Campus universitario di Monte S. Angelo, Via Cintia, 80126 Napoli, Italy
| | - Massimo Pica Ciamarra
- CNR-SPIN, sezione di Napoli, Dipartimento di Fisica, Campus universitario di Monte S. Angelo, Via Cintia, 80126 Napoli, Italy
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore , 639798
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Pennanen P, Alanne MH, Fazeli E, Deguchi T, Näreoja T, Peltonen S, Peltonen J. Diversity of actin architecture in human osteoclasts: network of curved and branched actin supporting cell shape and intercellular micrometer-level tubes. Mol Cell Biochem 2017; 432:131-139. [PMID: 28293874 PMCID: PMC5532409 DOI: 10.1007/s11010-017-3004-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 03/04/2017] [Indexed: 12/17/2022]
Abstract
Osteoclasts are multinucleated bone-resorbing cells with a dynamic actin cytoskeleton. Osteoclasts are derived from circulating mononuclear precursors. Confocal and stimulated emission depletion (STED) super-resolution microscopy was used to investigate peripheral blood-derived human osteoclasts cultured on glass surfaces. STED and confocal microscopy demonstrated that the actin was curved and branched, for instance, in the vicinity of membrane ruffles. The overall architecture of the curved actin network extended from the podosomes to the top of the cell. The other novel finding was that a micrometer-level tube containing actin bridged the osteoclasts well above the level of the culture glass. The actin filaments of the tubes originated from the network of curved actin often surrounding a group of nuclei. Furthermore, nuclei were occasionally located inside the tubes. Our findings demonstrated the accumulation of c-Src, cortactin, cofilin, and actin around nuclei suggesting their role in nuclear processes such as the locomotion of nuclei. ARP2/3 labeling was abundant at the substratum level of osteoclasts and in the branched actin network, where it localized to the branching points. We speculate that the actin-containing tubes of osteoclasts may provide a means of transportation of nuclei, e.g., during the fusion of osteoclasts. These novel findings can pave the way for future studies aiming at the elucidation of the differentiation of multinucleated osteoclasts.
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Affiliation(s)
- Paula Pennanen
- Department of Cell Biology and Anatomy, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | - Maria Helena Alanne
- Department of Cell Biology and Anatomy, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | - Elnaz Fazeli
- Laboratory of Biophysics, Department of Cell Biology and Anatomy and Medicity Research Laboratories, University of Turku, P.O. Box 123, 20521, Turku, Finland
| | - Takahiro Deguchi
- Laboratory of Biophysics, Department of Cell Biology and Anatomy and Medicity Research Laboratories, University of Turku, P.O. Box 123, 20521, Turku, Finland
| | - Tuomas Näreoja
- Laboratory of Biophysics, Department of Cell Biology and Anatomy and Medicity Research Laboratories, University of Turku, P.O. Box 123, 20521, Turku, Finland
- Division of Pathology, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Sirkku Peltonen
- Department of Dermatology, University of Turku and Turku University Hospital, PO BOX 52, 20521, Turku, Finland
| | - Juha Peltonen
- Department of Cell Biology and Anatomy, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland.
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Abstract
The actin cytoskeleton is a critical regulator of cytoplasmic architecture and mechanics, essential in a myriad of physiological processes. Here we demonstrate a liquid phase of actin filaments in the presence of the physiological cross-linker, filamin. Filamin condenses short actin filaments into spindle-shaped droplets, or tactoids, with shape dynamics consistent with a continuum model of anisotropic liquids. We find that cross-linker density controls the droplet shape and deformation timescales, consistent with a variable interfacial tension and viscosity. Near the liquid-solid transition, cross-linked actin bundles show behaviors reminiscent of fluid threads, including capillary instabilities and contraction. These data reveal a liquid droplet phase of actin, demixed from the surrounding solution and dominated by interfacial tension. These results suggest a mechanism to control organization, morphology, and dynamics of the actin cytoskeleton.
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49
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Towards the understanding of cytoskeleton fluidisation-solidification regulation. Biomech Model Mechanobiol 2017; 16:1159-1169. [PMID: 28132108 DOI: 10.1007/s10237-017-0878-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 01/13/2017] [Indexed: 10/24/2022]
Abstract
The understanding of the self-regulation of the mechanical properties in non-sarcomeric cells, such as lung cells or cells during tissue development, remains an open research problem with many unresolved issues. Their behaviour is far from the image of the traditionally studied sarcomeric cells, since the crosstalk between the signalling pathways and the complexity of the mechanical properties creates an intriguing mechano-chemical coupling. In these situations, the inelastic effects dominate the cytoskeletal structure showing phenomena like fluidisation and subsequent solidification. Here, we proposes the inelastic contractile unit framework as an attempt to reconciles these effects. The model comprises a mechanical description of the nonlinear elasticity of the cytoskeleton incorporated into a continuum-mechanics framework using the eighth-chains model. In order to address the inelastic effect, we incorporate the dynamic of crosslinks, considering the [Formula: see text]-actinin and the active stress induced by the myosin molecular motors. Finally, we introduce a hypothesis that links the ability to fluidise and re-solidify as a consequence of the interaction between the active stress and the gelation state defined by the crosslinks. We validate the model with data obtained from experiments of drug-induced relaxation reported in the literature.
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50
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Ovaska M, Bertalan Z, Miksic A, Sugni M, Di Benedetto C, Ferrario C, Leggio L, Guidetti L, Alava MJ, La Porta CA, Zapperi S. Deformation and fracture of echinoderm collagen networks. J Mech Behav Biomed Mater 2017; 65:42-52. [DOI: 10.1016/j.jmbbm.2016.07.035] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 07/07/2016] [Accepted: 07/31/2016] [Indexed: 11/26/2022]
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