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Ioannou IA, Brooks NJ, Kuimova MK, Elani Y. Visualizing Actin Packing and the Effects of Actin Attachment on Lipid Membrane Viscosity Using Molecular Rotors. JACS AU 2024; 4:2041-2049. [PMID: 38818078 PMCID: PMC11134356 DOI: 10.1021/jacsau.4c00237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 04/10/2024] [Accepted: 04/11/2024] [Indexed: 06/01/2024]
Abstract
The actin cytoskeleton and its elaborate interplay with the plasma membrane participate in and control numerous biological processes in eukaryotic cells. Malfunction of actin networks and changes in their dynamics are related to various diseases, from actin myopathies to uncontrolled cell growth and tumorigenesis. Importantly, the biophysical and mechanical properties of actin and its assemblies are deeply intertwined with the biological functions of the cytoskeleton. Novel tools to study actin and its associated biophysical features are, therefore, of prime importance. Here we develop a new approach which exploits fluorescence lifetime imaging microscopy (FLIM) and environmentally sensitive fluorophores termed molecular rotors, acting as quantitative microviscosity sensors, to monitor dynamic viscoelastic properties of both actin structures and lipid membranes. In order to reproduce a minimal actin cortex in synthetic cell models, we encapsulated and attached actin networks to the lipid bilayer of giant unilamellar vesicles (GUVs). Using a cyanine-based molecular rotor, DiSC2(3), we show that different types of actin bundles are characterized by distinct packing, which can be spatially resolved using FLIM. Similarly, we show that a lipid bilayer-localized molecular rotor can monitor the effects of attaching cross-linked actin networks to the lipid membrane, revealing an increase in membrane viscosity upon actin attachment. Our approach bypasses constraints associated with existing methods for actin imaging, many of which lack the capability for direct visualization of biophysical properties. It can therefore contribute to a deeper understanding of the role that actin plays in fundamental biological processes and help elucidate the underlying biophysics of actin-related diseases.
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Affiliation(s)
- Ion A. Ioannou
- Department
of Chemistry, Imperial College London, Molecular
Sciences Research Hub, London W12 0BZ, U.K.
- Department
of Chemical Engineering, Imperial College
London, South Kensington, London SW7 2AZ, U.K.
| | - Nickolas J. Brooks
- Department
of Chemistry, Imperial College London, Molecular
Sciences Research Hub, London W12 0BZ, U.K.
| | - Marina K. Kuimova
- Department
of Chemistry, Imperial College London, Molecular
Sciences Research Hub, London W12 0BZ, U.K.
| | - Yuval Elani
- Department
of Chemical Engineering, Imperial College
London, South Kensington, London SW7 2AZ, U.K.
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2
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Cantero M, Cvirkaite-Krupovic V, Krupovic M, de Pablo PJ. Mechanical tomography of an archaeal lemon-shaped virus reveals membrane-like fluidity of the capsid and liquid nucleoprotein cargo. Proc Natl Acad Sci U S A 2023; 120:e2307717120. [PMID: 37824526 PMCID: PMC10589707 DOI: 10.1073/pnas.2307717120] [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: 05/08/2023] [Accepted: 09/08/2023] [Indexed: 10/14/2023] Open
Abstract
Archaeal lemon-shaped viruses have unique helical capsids composed of highly hydrophobic protein strands which can slide past each other resulting in remarkable morphological reorganization. Here, using atomic force microscopy, we explore the biomechanical properties of the lemon-shaped virions of Sulfolobus monocaudavirus 1 (SMV1), a double-stranded DNA virus which infects hyperthermophilic (~80 °C) and acidophilic (pH ~ 2) archaea. Our results reveal that SMV1 virions are extremely soft and withstand repeated extensive deformations, reaching remarkable strains of 80% during multiple cycles of consecutive mechanical assaults, yet showing scarce traces of disruption. SMV1 virions can reversibly collapse wall-to-wall, reducing their volume by ~90%. Beyond revealing the exceptional malleability of the SMV1 protein shell, our data also suggest a fluid-like nucleoprotein cargo which can flow inside the capsid, resisting and accommodating mechanical deformations without further alteration. Our experiments suggest a packing fraction of the virus core to be as low as 11%, with the amount of the accessory proteins almost four times exceeding that of the viral genome. Our findings indicate that SMV1 protein capsid displays biomechanical properties of lipid membranes, which is not found among protein capsids of other viruses. The remarkable malleability and fluidity of the SMV1 virions are likely necessary for the structural transformations during the infection and adaptation to extreme environmental conditions.
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Affiliation(s)
- Miguel Cantero
- Departamento de Física de la Materia Condensada C03, Universidad Autónoma de Madrid, Madrid28049, Spain
| | | | - Mart Krupovic
- Institut Pasteur, Université Paris Cité, Archaeal Virology Unit, Paris75015, France
| | - Pedro J. de Pablo
- Departamento de Física de la Materia Condensada C03, Universidad Autónoma de Madrid, Madrid28049, Spain
- Instituto de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid28049, Spain
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3
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Hein JI, Scholz J, Körber S, Kaufmann T, Faix J. Unleashed Actin Assembly in Capping Protein-Deficient B16-F1 Cells Enables Identification of Multiple Factors Contributing to Filopodium Formation. Cells 2023; 12:cells12060890. [PMID: 36980231 PMCID: PMC10047565 DOI: 10.3390/cells12060890] [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: 12/02/2022] [Revised: 03/08/2023] [Accepted: 03/10/2023] [Indexed: 03/16/2023] Open
Abstract
Background: Filopodia are dynamic, finger-like actin-filament bundles that overcome membrane tension by forces generated through actin polymerization at their tips to allow extension of these structures a few microns beyond the cell periphery. Actin assembly of these protrusions is regulated by accessory proteins including heterodimeric capping protein (CP) or Ena/VASP actin polymerases to either terminate or promote filament growth. Accordingly, the depletion of CP in B16-F1 melanoma cells was previously shown to cause an explosive formation of filopodia. In Ena/VASP-deficient cells, CP depletion appeared to result in ruffling instead of inducing filopodia, implying that Ena/VASP proteins are absolutely essential for filopodia formation. However, this hypothesis was not yet experimentally confirmed. Methods: Here, we used B16-F1 cells and CRISPR/Cas9 technology to eliminate CP either alone or in combination with Ena/VASP or other factors residing at filopodia tips, followed by quantifications of filopodia length and number. Results: Unexpectedly, we find massive formations of filopodia even in the absence of CP and Ena/VASP proteins. Notably, combined inactivation of Ena/VASP, unconventional myosin-X and the formin FMNL3 was required to markedly impair filopodia formation in CP-deficient cells. Conclusions: Taken together, our results reveal that, besides Ena/VASP proteins, numerous other factors contribute to filopodia formation.
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Affiliation(s)
| | | | | | | | - Jan Faix
- Correspondence: ; Tel.: +49-511-532-2928
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4
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Yang N, Zhang Y, Su C, Zhu C, Jia J, Nishinari K. The effect of sodium alginate on the nanomechanical properties and interaction between oil body droplets studied using atomic force microscopy. Food Hydrocoll 2023. [DOI: 10.1016/j.foodhyd.2023.108587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
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5
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Li DY, Zhou ZH, Yu YL, Deng NN. Microfluidic construction of cytoskeleton-like hydrogel matrix for stabilizing artificial cells. Chem Eng Sci 2022. [DOI: 10.1016/j.ces.2022.118186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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6
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Schmitt LM, Dreissen G, Kolasinac R, Csiszár A, Merkel R. Membrane tension controls the phase equilibrium in fusogenic liposomes. RSC Adv 2022; 12:24114-24129. [PMID: 36093247 PMCID: PMC9400399 DOI: 10.1039/d2ra04019k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 08/15/2022] [Indexed: 11/21/2022] Open
Abstract
Fusogenic liposomes have been widely used for molecule delivery to cell membranes and cell interior. However, their physicochemical state is still little understood. We tested mechanical material behavior by micropipette aspiration of giant vesicles from fusogenic lipid mixtures and found that the membranes of these vesicles are fluid and under high mechanical tension even before aspiration. Based on this result, we developed a theoretical framework to determine the area expansion modulus and membrane tension of such pre-tensed vesicles from aspiration experiments. Surprisingly high membrane tension of 2.1 mN m-1 and very low area expansion modulus of 63 mN m-1 were found. We interpret these peculiar material properties as the result of a mechanically driven phase transition between the usual lamellar phase and an, as of now, not finally determined three dimensional phase of the lipid mixture. The free enthalpy of transition between these phases is very low, i.e. on the order of the thermal energy.
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Affiliation(s)
- Laura Maria Schmitt
- Forschungszentrum Julich, Institute of Biological Information Processing 2: MechanobiologyJulichGermany
| | - Georg Dreissen
- Forschungszentrum Julich, Institute of Biological Information Processing 2: MechanobiologyJulichGermany
| | - Rejhana Kolasinac
- Forschungszentrum Julich, Institute of Biological Information Processing 2: MechanobiologyJulichGermany
| | - Agnes Csiszár
- Forschungszentrum Julich, Institute of Biological Information Processing 2: MechanobiologyJulichGermany
| | - Rudolf Merkel
- Forschungszentrum Julich, Institute of Biological Information Processing 2: MechanobiologyJulichGermany+49 2461 613907+49 2461 613080
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7
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Litschel T, Kelley CF, Holz D, Adeli Koudehi M, Vogel SK, Burbaum L, Mizuno N, Vavylonis D, Schwille P. Reconstitution of contractile actomyosin rings in vesicles. Nat Commun 2021; 12:2254. [PMID: 33859190 PMCID: PMC8050101 DOI: 10.1038/s41467-021-22422-7] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 03/04/2021] [Indexed: 12/31/2022] Open
Abstract
One of the grand challenges of bottom-up synthetic biology is the development of minimal machineries for cell division. The mechanical transformation of large-scale compartments, such as Giant Unilamellar Vesicles (GUVs), requires the geometry-specific coordination of active elements, several orders of magnitude larger than the molecular scale. Of all cytoskeletal structures, large-scale actomyosin rings appear to be the most promising cellular elements to accomplish this task. Here, we have adopted advanced encapsulation methods to study bundled actin filaments in GUVs and compare our results with theoretical modeling. By changing few key parameters, actin polymerization can be differentiated to resemble various types of networks in living cells. Importantly, we find membrane binding to be crucial for the robust condensation into a single actin ring in spherical vesicles, as predicted by theoretical considerations. Upon force generation by ATP-driven myosin motors, these ring-like actin structures contract and locally constrict the vesicle, forming furrow-like deformations. On the other hand, cortex-like actin networks are shown to induce and stabilize deformations from spherical shapes. Cytoskeletal networks support and direct cell shape and guide intercellular transport, but relatively little is understood about the self-organization of cytoskeletal components on the scale of an entire cell. Here, authors use an in vitro system and observe the assembly of different types of actin networks and the condensation of membrane-bound actin into single rings.
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Affiliation(s)
- Thomas Litschel
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Charlotte F Kelley
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany.,Department of Structural Cell Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Danielle Holz
- Department of Physics, Lehigh University, Bethlehem, PA, USA
| | | | - Sven K Vogel
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Laura Burbaum
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Naoko Mizuno
- Department of Structural Cell Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | | | - Petra Schwille
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany.
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8
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Affiliation(s)
- Chandra Has
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
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9
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Redondo-Morata L, Losada-Pérez P, Giannotti MI. Lipid bilayers: Phase behavior and nanomechanics. CURRENT TOPICS IN MEMBRANES 2020; 86:1-55. [PMID: 33837691 DOI: 10.1016/bs.ctm.2020.08.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Lipid membranes are involved in many physiological processes like recognition, signaling, fusion or remodeling of the cell membrane or some of its internal compartments. Within the cell, they are the ultimate barrier, while maintaining the fluidity or flexibility required for a myriad of processes, including membrane protein assembly. The physical properties of in vitro model membranes as model cell membranes have been extensively studied with a variety of techniques, from classical thermodynamics to advanced modern microscopies. Here we review the nanomechanics of solid-supported lipid membranes with a focus in their phase behavior. Relevant information obtained by quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM) as complementary techniques in the nano/mesoscale interface is presented. Membrane morphological and mechanical characterization will be discussed in the framework of its phase behavior, phase transitions and coexistence, in simple and complex models, and upon the presence of cholesterol.
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Affiliation(s)
- Lorena Redondo-Morata
- Center for Infection and Immunity of Lille, INSERM U1019, CNRS UMR 8204, Lille, France
| | - Patricia Losada-Pérez
- Experimental Soft Matter and Thermal Physics (EST) Group, Department of Physics, Université Libre de Bruxelles, Brussels, Belgium
| | - Marina Inés Giannotti
- Biomedical Research Networking Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Madrid, Spain; Institut de Bioenginyeria de Catalunya (IBEC), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain; Departament de Ciència de Materials i Química Física, Universitat de Barcelona, Barcelona, Spain.
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10
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Majewska M, Mrdenovic D, Pieta I, Nowakowski R, Pieta P. Nanomechanical characterization of single phospholipid bilayer in ripple phase with PF-QNM AFM. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183347. [DOI: 10.1016/j.bbamem.2020.183347] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 04/16/2020] [Accepted: 05/07/2020] [Indexed: 12/31/2022]
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11
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Yang N, Su C, Zhang Y, Jia J, Leheny RL, Nishinari K, Fang Y, Phillips GO. In situ nanomechanical properties of natural oil bodies studied using atomic force microscopy. J Colloid Interface Sci 2020; 570:362-374. [PMID: 32182477 DOI: 10.1016/j.jcis.2020.03.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 01/15/2020] [Accepted: 03/04/2020] [Indexed: 12/21/2022]
Abstract
Natural oil bodies (OBs) from plant organs represent an important category of functional ingredients and materials in a variety of industrial sectors. Their applications are closely related to the membrane mechanical properties on a single droplet level, which remain difficult to determine. In this research, the mechanical properties of the membranes of OBs from soybean, sesame, and peanut were investigated in-situ by atomic force microscopy (AFM). Different regions of the force-deformation curves obtained during compression were analyzed to extract the stiffness Kb or Young's modulus of the OB membranes using Hooke's law, Reissner theory, and the elastic membrane theory. At higher strains (ε = 0.15-0.20), the elastic membrane theory breaks down. We propose an extension of the theory that includes a contribution to the force from interfacial tension based on the Gibbs energy, allowing effective determination of Young's modulus and interfacial tension of the OB membranes in the water environment simultaneously. The mechanical properties of the OBs of different sizes and species, as well as a comparison with other phospholipid membrane materials, are discussed and related to their membrane compositions and structures. It was found that the natural OBs are soft droplets but do not rupture and can fully recover following compressive strains as large as 0.3. The OBs with higher protein/oil ratio, have smaller size and stronger mechanical properties, and thus are more stable. The low interfacial tension due to the existence of phospholipid-protein membrane also contributes to the stability of the OBs. This is the first report measuring the mechanical properties of OB membranes in-situ directly.
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Affiliation(s)
- Nan Yang
- Glyn O. Phillips Hydrocolloid Research Centre, 111 Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Food Hydrocolloid International Science and Technology Cooperation Base of Hubei Province, Department of Bioengineering and Food Science, Hubei University of Technology, Wuhan 430068, China
| | - Chunxia Su
- Glyn O. Phillips Hydrocolloid Research Centre, 111 Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Food Hydrocolloid International Science and Technology Cooperation Base of Hubei Province, Department of Bioengineering and Food Science, Hubei University of Technology, Wuhan 430068, China
| | - Yuemei Zhang
- Glyn O. Phillips Hydrocolloid Research Centre, 111 Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Food Hydrocolloid International Science and Technology Cooperation Base of Hubei Province, Department of Bioengineering and Food Science, Hubei University of Technology, Wuhan 430068, China
| | - Junji Jia
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Robert L Leheny
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Katsuyoshi Nishinari
- Glyn O. Phillips Hydrocolloid Research Centre, 111 Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Food Hydrocolloid International Science and Technology Cooperation Base of Hubei Province, Department of Bioengineering and Food Science, Hubei University of Technology, Wuhan 430068, China
| | - Yapeng Fang
- Glyn O. Phillips Hydrocolloid Research Centre, 111 Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Food Hydrocolloid International Science and Technology Cooperation Base of Hubei Province, Department of Bioengineering and Food Science, Hubei University of Technology, Wuhan 430068, China; Department of Food Science and Technology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China.
| | - Glyn O Phillips
- Glyn O. Phillips Hydrocolloid Research Centre, 111 Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Food Hydrocolloid International Science and Technology Cooperation Base of Hubei Province, Department of Bioengineering and Food Science, Hubei University of Technology, Wuhan 430068, China
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12
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Rodriguez-Quijada C, Dahl JB. Non-contact microfluidic mechanical property measurements of single apoptotic bodies. Biochim Biophys Acta Gen Subj 2020; 1865:129657. [PMID: 32512171 DOI: 10.1016/j.bbagen.2020.129657] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 03/18/2020] [Accepted: 06/02/2020] [Indexed: 01/29/2023]
Abstract
BACKGROUND Cells exchange information by secreting micro- and nanosized extracellular vesicles (EVs), ranging from exosomes (30-100 nm) to apoptotic bodies (ABs, 1-5 μm). There is still much to understand about fundamental EV biological, physical, and chemical properties before clinical applications can be developed. EV mechanical properties have only been measured with atomic force microscopy (AFM) with its problematic adhesion and hard substrate effects. To understand EV mechanical behavior in less extreme mechanical conditions relevant to blood flow and many soft tissue environments, a non-contact measurement technique is needed. METHODS We measured the mechanical properties of single microscale ABs derived from human blood plasma using non-contact microfluidics. EVs were gently stretched in extensional flow, similar to a traditional tensile test, and a linear mechanical model was applied to estimate mechanical stiffnesses from the observed stretching. RESULTS The effective shear elastic modulus of ABs in non-contact flow conditions is approximately 5.6 ± 0.5 Pa, 7 orders of magnitude lower than previously reported AFM-measured biological exosome stiffnesses and 200 times smaller than suspended cells. CONCLUSIONS Apoptotic bodies are very soft in fluid environments and exhibit lower effective stiffnesses than suspended cells. By measuring ABs in a natural fluid environment and low-force regime without hard probes and surfaces, we achieved closer agreement with linear mechanical theory and therefore more accurate stiffness measurements. GENERAL SIGNIFICANCE AFM manufacturers and users should consider implementing new mechanical models to interpret AFM force indentation curves so that accurate extracellular vesicle mechanical properties can be extracted.
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Affiliation(s)
| | - Joanna B Dahl
- Engineering Department, University of Massachusetts Boston, Boston, MA 02125, United States of America.
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13
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Saavedra V O, Fernandes TFD, Milhiet PE, Costa L. Compression, Rupture, and Puncture of Model Membranes at the Molecular Scale. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:5709-5716. [PMID: 32427478 DOI: 10.1021/acs.langmuir.0c00247] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Elastic properties of biological membranes are involved in a large number of membrane functionalities and activities. Conventionally characterized in terms of Young's modulus, bending stiffness and stretching modulus, membrane mechanics can be assessed at high lateral resolution by means of atomic force microscopy (AFM). Here we show that the mechanical response of biomimetic model systems such as supported lipid bilayers (SLBs) is highly affected by the size of the AFM tip employed as a membrane indenter. Our study is focused on phase-separated fluid-gel lipid membranes at room temperature. In a small tip radius regime (≈ 2 nm) and in the case of fluid phase membranes, we show that the tip can penetrate through the membrane minimizing molecular vertical compression and in absence of molecular membrane rupture. In this case, AFM indentation experiments cannot assess the vertical membrane Young's modulus. In agreement with the data reported in the literature, in the case of larger indenters (>2 nm) SLBs can be compressed leading to an evaluation of Young's modulus and membrane maximal withstanding force before rupture. We show that such force increases with the indenter in agreement with the existing theoretical frame. Finally, we demonstrate that the latter has no influence on the number of molecules involved in the rupture process that is observed to be constant and rather dependent on the indenter chemical composition.
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Affiliation(s)
- Oscar Saavedra V
- Centre de Biochimie Structurale (CBS), CNRS, INSERM, Univ. Montpellier, 34090 Montpellier, France
| | - Thales F D Fernandes
- Centre de Biochimie Structurale (CBS), CNRS, INSERM, Univ. Montpellier, 34090 Montpellier, France
| | - Pierre-Emmanuel Milhiet
- Centre de Biochimie Structurale (CBS), CNRS, INSERM, Univ. Montpellier, 34090 Montpellier, France
| | - Luca Costa
- Centre de Biochimie Structurale (CBS), CNRS, INSERM, Univ. Montpellier, 34090 Montpellier, France
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14
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Piontek MC, Lira RB, Roos WH. Active probing of the mechanical properties of biological and synthetic vesicles. Biochim Biophys Acta Gen Subj 2019; 1865:129486. [PMID: 31734458 DOI: 10.1016/j.bbagen.2019.129486] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2019] [Revised: 11/05/2019] [Accepted: 11/09/2019] [Indexed: 02/07/2023]
Abstract
BACKGROUND The interest in mechanics of synthetic and biological vesicles has been continuously growing during the last decades. Liposomes serve as model systems for investigating fundamental membrane processes and properties. More recently, extracellular vesicles (EVs) have been investigated mechanically as well. EVs are widely studied in fundamental and applied sciences, but their material properties remained elusive until recently. Elucidating the mechanical properties of vesicles is essential to unveil the mechanisms behind a variety of biological processes, e.g. budding, vesiculation and cellular uptake mechanisms. SCOPE OF REVIEW The importance of mechanobiology for studies of vesicles and membranes is discussed, as well as the different available techniques to probe their mechanical properties. In particular, the mechanics of vesicles and membranes as obtained by nanoindentation, micropipette aspiration, optical tweezers, electrodeformation and electroporation experiments is addressed. MAJOR CONCLUSIONS EVs and liposomes possess an astonishing rich, diverse behavior. To better understand their properties, and for optimization of their applications in nanotechnology, an improved understanding of their mechanical properties is needed. Depending on the size of the vesicles and the specific scientific question, different techniques can be chosen for their mechanical characterization. GENERAL SIGNIFICANCE Understanding the mechanical properties of vesicles is necessary to gain deeper insight in the fundamental biological mechanisms involved in vesicle generation and cellular uptake. This furthermore facilitates technological applications such as using vesicles as targeted drug delivery vehicles. Liposome studies provide insight into fundamental membrane processes and properties, whereas the role and functioning of EVs in biology and medicine are increasingly elucidated.
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Affiliation(s)
- Melissa C Piontek
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands.
| | - Rafael B Lira
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands.
| | - Wouter H Roos
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands.
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15
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Shafi AS, McClements J, Albaijan I, Abou-Saleh RH, Moran C, Koutsos V. Probing phospholipid microbubbles by atomic force microscopy to quantify bubble mechanics and nanostructural shell properties. Colloids Surf B Biointerfaces 2019; 181:506-515. [DOI: 10.1016/j.colsurfb.2019.04.062] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 04/05/2019] [Accepted: 04/29/2019] [Indexed: 12/17/2022]
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16
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Omidvar R, Römer W. Glycan-decorated protocells: novel features for rebuilding cellular processes. Interface Focus 2019; 9:20180084. [PMID: 30842879 PMCID: PMC6388021 DOI: 10.1098/rsfs.2018.0084] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/14/2019] [Indexed: 02/06/2023] Open
Abstract
In synthetic biology approaches, lipid vesicles are widely used as protocell models. While many compounds have been encapsulated in vesicles (e.g. DNA, cytoskeleton and enzymes), the incorporation of glycocalyx components in the lipid bilayer has attracted much less attention so far. In recent years, glycoconjugates have been integrated in the membrane of giant unilamellar vesicles (GUVs). These minimal membrane systems have largely contributed to shed light on the molecular mechanisms of cellular processes. In this review, we first introduce several preparation and biophysical characterization methods of GUVs. Then, we highlight specific applications of protocells investigating glycolipid-mediated endocytosis of toxins, viruses and bacteria. In addition, we delineate how prototissues have been assembled from glycan-decorated protocells by using lectin-mediated cross-linking of opposed glycoreceptors (e.g. glycolipids and glycopeptides). In future applications, glycan-decorated protocells might be useful for investigating cell-cell interactions (e.g. adhesion and communication). We also speculate about the implication of lectin-glycoreceptor interactions in membrane fusion processes.
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Affiliation(s)
- Ramin Omidvar
- Faculty of Biology, Albert-Ludwigs-University Freiburg, Schänzlestraße 1, 79104 Freiburg, Germany
- Signalling Research Centres BIOSS and CIBSS, Albert-Ludwigs-University Freiburg, Schänzlestraße 18, 79104 Freiburg, Germany
- Freiburg Center for Interactive Materials and Bioinspired Technology (FIT), Albert-Ludwigs-University Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany
| | - Winfried Römer
- Faculty of Biology, Albert-Ludwigs-University Freiburg, Schänzlestraße 1, 79104 Freiburg, Germany
- Signalling Research Centres BIOSS and CIBSS, Albert-Ludwigs-University Freiburg, Schänzlestraße 18, 79104 Freiburg, Germany
- Freiburg Center for Interactive Materials and Bioinspired Technology (FIT), Albert-Ludwigs-University Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany
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Gao L, Zhao H, Li T, Huo P, Chen D, Liu B. Atomic Force Microscopy Based Tip-Enhanced Raman Spectroscopy in Biology. Int J Mol Sci 2018; 19:E1193. [PMID: 29652860 PMCID: PMC5979470 DOI: 10.3390/ijms19041193] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 04/09/2018] [Accepted: 04/10/2018] [Indexed: 12/15/2022] Open
Abstract
Most biological phenomena occur at the nanometer scale, which is not accessible by the conventional optical techniques because of the optical diffraction limitation. Tip-enhanced Raman spectroscopy (TERS), one of the burgeoning probing techniques, not only can provide the topography characterization with high resolution, but also can deliver the chemical or molecular information of a sample beyond the optical diffraction limitation. Therefore, it has been widely used in various structural analyses pertaining to materials science, tissue engineering, biological processes and so on. Based on the different feedback mechanisms, TERS can be classified into three types: atomic force microscopy based TERS system (AFM-TERS), scanning tunneling microscopy based TERS system (STM-TERS) and shear force microscopy based TERS system (SFM-TERS). Among them, AFM-TERS is the most widely adopted feedback system by live biosamples because it can work in liquid and this allows the investigation of biological molecules under native conditions. In this review, we mainly focus on the applications of AFM-TERS in three biological systems: nucleic acids, proteins and pathogens. From the TERS characterization to the data analysis, this review demonstrates that AFM-TERS has great potential applications to visually characterizing the biomolecular structure and crucially detecting more nano-chemical information of biological systems.
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Affiliation(s)
- Lizhen Gao
- Institute of Photo-biophysics, School of Physics and Electronics, Henan University, Kaifeng 475004, China.
| | - Huiling Zhao
- Institute of Photo-biophysics, School of Physics and Electronics, Henan University, Kaifeng 475004, China.
| | - Tianfeng Li
- Institute of Photo-biophysics, School of Physics and Electronics, Henan University, Kaifeng 475004, China.
| | - Peipei Huo
- Laboratory of Functional Molecules and Materials, School of Physics and Optoelectronic Engineering, Shandong University of Technology, Xincun West Road 266, Zibo 255000, China.
| | - Dong Chen
- Institute of Photo-biophysics, School of Physics and Electronics, Henan University, Kaifeng 475004, China.
| | - Bo Liu
- Institute of Photo-biophysics, School of Physics and Electronics, Henan University, Kaifeng 475004, China.
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18
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Effect of Statins on the Nanomechanical Properties of Supported Lipid Bilayers. Biophys J 2017; 111:363-372. [PMID: 27463138 DOI: 10.1016/j.bpj.2016.06.016] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 05/25/2016] [Accepted: 06/15/2016] [Indexed: 11/23/2022] Open
Abstract
Many drugs and other xenobiotics may reach systemic concentrations where they interact not only with the proteins that are their therapeutic targets but also modify the physicochemical properties of the cell membrane, which may lead to altered function of many transmembrane proteins beyond the intended targets. These changes in bilayer properties may contribute to nonspecific, promiscuous changes in membrane protein and cell function because membrane proteins are energetically coupled to their host lipid bilayer. It is thus important, for both pharmaceutical and biophysical reasons, to understand the bilayer-modifying effect of amphiphiles (including therapeutic agents). Here we use atomic force microscopy topography imaging and nanomechanical mapping to monitor the effect of statins, a family of hypolipidemic drugs, on synthetic lipid membranes. Our results reveal that statins alter the nanomechanical stability of the bilayers and increase their elastic moduli depending on the lipid bilayer order. Our results also suggest that statins increase bilayer heterogeneity, which may indicate that statins form nanometer-sized aggregates in the membrane. This is further evidence that changes in bilayer nanoscale mechanical properties may be a signature of lipid bilayer-mediated effects of amphiphilic drugs.
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Et-Thakafy O, Delorme N, Gaillard C, Mériadec C, Artzner F, Lopez C, Guyomarc'h F. Mechanical Properties of Membranes Composed of Gel-Phase or Fluid-Phase Phospholipids Probed on Liposomes by Atomic Force Spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:5117-5126. [PMID: 28475345 DOI: 10.1021/acs.langmuir.7b00363] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
In many liposome applications, the nanomechanical properties of the membrane envelope are essential to ensure, e.g., physical stability, protection, or penetration into tissues. Of all factors, the lipid composition and its phase behavior are susceptible to tune the mechanical properties of membranes. To investigate this, small unilamellar vesicles (SUV; diameter < 200 nm), referred to as liposomes, were produced using either unsaturated 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) or saturated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in aqueous buffer at pH 6.7. The respective melting temperatures of these phospholipids were -20 and 41 °C. X-ray diffraction analysis confirmed that at 20 °C DOPC was in the fluid phase and DPPC was in the gel phase. After adsorption of the liposomes onto flat silicon substrates, atomic force microscopy (AFM) was used to image and probe the mechanical properties of the liposome membrane. The resulting force-distance curves were treated using an analytical model based on the shell theory to yield the Young's modulus (E) and the bending rigidity (kC) of the curved membranes. The mechanical investigation showed that DPPC membranes were much stiffer (E = 116 ± 45 MPa) than those of DOPC (E = 13 ± 9 MPa) at 20 °C. The study demonstrates that the employed methodology allows discrimination of the respective properties of gel- or fluid-phase membranes when in the shape of liposomes. It opens perspectives to map the mechanical properties of liposomes containing both fluid and gel phases or of biological systems.
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Affiliation(s)
| | - Nicolas Delorme
- UMR CNRS 6283 Institut des Molécules et Matériaux du Mans, Université du Maine, Université Bretagne-Loire, 72000 Le Mans, France
| | - Cédric Gaillard
- UR BIA 1268 Biopolymères Interactions Assemblages, INRA, 44316 Nantes, France
| | - Cristelle Mériadec
- Institut de Physique de Rennes, UMR 6251, CNRS, Université de Rennes 1, 263 Av. Général Leclerc, 35042 Rennes, France
| | - Franck Artzner
- Institut de Physique de Rennes, UMR 6251, CNRS, Université de Rennes 1, 263 Av. Général Leclerc, 35042 Rennes, France
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20
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Jørgensen IL, Kemmer GC, Pomorski TG. Membrane protein reconstitution into giant unilamellar vesicles: a review on current techniques. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2016; 46:103-119. [DOI: 10.1007/s00249-016-1155-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 06/18/2016] [Accepted: 07/03/2016] [Indexed: 12/11/2022]
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21
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Tsai FC, Koenderink GH. Shape control of lipid bilayer membranes by confined actin bundles. SOFT MATTER 2015; 11:8834-8847. [PMID: 26395896 DOI: 10.1039/c5sm01583a] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In living cells, lipid membranes and biopolymers determine each other's conformation in a delicate force balance. Cellular polymers such as actin filaments are strongly confined by the plasma membrane in cell protrusions such as lamellipodia and filopodia. Conversely, protrusion formation is facilitated by actin-driven membrane deformation and these protrusions are maintained by dense actin networks or bundles of actin filaments. Here we investigate the mechanical interplay between actin bundles and lipid bilayer membranes by reconstituting a minimal model system based on cell-sized liposomes with encapsulated actin filaments bundled by fascin. To address the competition between the deformability of the membrane and the enclosed actin bundles, we tune the bundle stiffness (through the fascin-to-actin molar ratio) and the membrane rigidity (through protein decoration). Using confocal microscopy and quantitative image analysis, we show that actin bundles deform the liposomes into a rich set of morphologies. For liposomes having a small membrane bending rigidity, the actin bundles tend to generate finger-like membrane protrusions that resemble cellular filopodia. Stiffer bundles formed at high crosslink density stay straight in the liposome body, whereas softer bundles formed at low crosslink density are bent and kinked. When the membrane has a large bending rigidity, membrane protrusions are suppressed. In this case, membrane enclosure forces the actin bundles to organize into cortical rings, to minimize the energy cost associated with filament bending. Our results highlight the importance of taking into account mechanical interactions between the actin cytoskeleton and the membrane to understand cell shape control.
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Affiliation(s)
- Feng-Ching Tsai
- FOM Institute AMOLF, Systems Biophysics Department, Science Park 104, 1098 XG Amsterdam, The Netherlands.
| | - Gijsje Hendrika Koenderink
- FOM Institute AMOLF, Systems Biophysics Department, Science Park 104, 1098 XG Amsterdam, The Netherlands.
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22
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Jahnel O, Hoffmann B, Merkel R, Bossinger O, Leube RE. Mechanical Probing of the Intermediate Filament-Rich Caenorhabditis Elegans Intestine. Methods Enzymol 2015; 568:681-706. [PMID: 26795489 DOI: 10.1016/bs.mie.2015.08.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
It is commonly accepted that intermediate filaments have an important mechanical function. This function relies not only on intrinsic material properties but is also determined by dynamic interactions with other cytoskeletal filament systems, distinct cell adhesion sites, and cellular organelles which are fine-tuned by multiple signaling pathways. While aspects of these properties and processes can be studied in vitro, their full complexity can only be understood in a viable tissue context. Yet, suitable and easily accessible model systems for monitoring tissue mechanics at high precision are rare. We show that the dissected intestine of the genetic model organism Caenorhabditis elegans fulfills this requirement. The 20 intestinal cells, which are arranged in an invariant fashion, are characterized by a dense subapical mesh of intermediate filaments that are attached to the C. elegans apical junction. We present procedures to visualize details of the characteristic intermediate filament-junctional complex arrangement in living animals. We then report on methods to prepare intestines with a fully intact intermediate filament cytoskeleton and detail procedures to assess their viability. A dual micropipette assay is described to measure mechanical properties of the dissected intestine while monitoring the spatial arrangement of the intermediate filament system. Advantages of this approach are (i) the high reproducibility of measurements because of the uniform architecture of the intestine and (ii) the high degree of accessibility allowing not only mechanical manipulation of an intact tissue but also control of culture medium composition and addition of drugs as well as visualization of cell structures. With this method, examination of worms carrying mutations in the intermediate filament system, its interacting partners and its regulators will become feasible.
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Affiliation(s)
- Oliver Jahnel
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Aachen, Germany
| | - Bernd Hoffmann
- Institute of Complex Systems, ICS-7: Biomechanics, Jülich, Germany
| | - Rudolf Merkel
- Institute of Complex Systems, ICS-7: Biomechanics, Jülich, Germany
| | - Olaf Bossinger
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Aachen, Germany
| | - Rudolf E Leube
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Aachen, Germany.
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23
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Schäfer E, Vache M, Kliesch TT, Janshoff A. Mechanical response of adherent giant liposomes to indentation with a conical AFM-tip. SOFT MATTER 2015; 11:4487-95. [PMID: 25946988 DOI: 10.1039/c5sm00191a] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Indentation of giant liposomes with a conical indenter is described by means of a tension-based membrane model. We found that nonlinear membrane theory neglecting the impact of bending sufficiently describes the mechanical response of liposomes to indentation as measured by atomic force microscopy. Giant vesicles are gently adsorbed on glassy surfaces via avidin-biotin linkages and indented centrally using an atomic force microscope equipped with conventional sharp tips mounted on top of an inverted microscope. Force indentation curves display a nonlinear response that allows to extract pre-stress of the bilayer T0 and the area compressibility modulus KA by computing the contour of the vesicle at a given force. The values for KA of fluid membranes correspond well to what is known from micropipet suction experiments and inferred from membrane undulation monitoring. Assembly of actin shells inside the liposome considerably stiffens the vesicles resulting in significantly larger area compressibility modules. The analysis can be easily extended to different indenter geometries with rotational symmetry.
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Affiliation(s)
- Edith Schäfer
- Department of Chemistry, University of Goettingen, Goettingen, Germany.
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24
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Janshoff A, Steinem C. Mechanics of lipid bilayers: What do we learn from pore-spanning membranes? BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:2977-83. [PMID: 26025679 DOI: 10.1016/j.bbamcr.2015.05.029] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 05/21/2015] [Accepted: 05/22/2015] [Indexed: 11/18/2022]
Abstract
The mechanical properties of biological membranes have become increasingly important not only from a biophysical viewpoint but also as they play a substantial role in the information transfer in cells and tissues. This minireview summarizes some of our recent understanding of the mechanical properties of artificial model membranes with particular emphasis on membranes suspending an array of pores, so called pore-spanning membranes. A theoretical description of the mechanical properties of these membranes might pave the way to biophysically describe and understand the complex behavior of native biological membranes. This article is part of a Special Issue entitled: Mechanobiology.
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Affiliation(s)
- Andreas Janshoff
- Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, 37077 Göttingen, Germany; Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany
| | - Claudia Steinem
- Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, 37077 Göttingen, Germany; Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany.
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25
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Takeda S, Subagyo A, Hui SP, Fuda H, Shrestha R, Sueoka K, Chiba H. Elastic modulus of low-density lipoprotein as potential indicator of its oxidation. Ann Clin Biochem 2015; 52:647-53. [PMID: 25887969 DOI: 10.1177/0004563215584958] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/08/2015] [Indexed: 11/15/2022]
Abstract
BACKGROUND Evaluation of low-density lipoprotein oxidation is important in the risk assessment of cardiovascular disease. Atomic force microscope is widely used to evaluate the physical properties including stiffness on a single-particle scale. In this study, the effect of low-density lipoprotein oxidation on the low-density lipoprotein stiffness was investigated using an atomic force microscope. METHODS Isolated low-density lipoprotein particles with or without oxidation were densely bound to an Au substrate on mica, and then pressed and deformed by the atomic force microscope tip. The stiffness of each low-density lipoprotein particle was estimated as the elastic modulus obtained by the force curve analysis. Biochemical change of low-density lipoprotein due to oxidation was studied by electrophoresis. RESULTS AND CONCLUSION The elastic modulus of low-density lipoprotein particles ranged between 0.1 and 2 MPa. The oxidation of low-density lipoprotein increased the number of low-density lipoprotein particles with smaller elastic moduli, indicating the decrease in low-density lipoprotein stiffness. The elastic modulus of low-density lipoprotein might be potentially useful to evaluate low-density lipoprotein oxidation.
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Affiliation(s)
- Seiji Takeda
- Faculty of Health Sciences, Hokkaido University, Sapporo, Japan
| | - Agus Subagyo
- Graduate School of Information Science and Technology, Hokkaido University, Sapporo, Japan
| | - Shu-Ping Hui
- Faculty of Health Sciences, Hokkaido University, Sapporo, Japan
| | - Hirotoshi Fuda
- Faculty of Health Sciences, Hokkaido University, Sapporo, Japan
| | - Rojeet Shrestha
- Faculty of Health Sciences, Hokkaido University, Sapporo, Japan
| | - Kazuhisa Sueoka
- Graduate School of Information Science and Technology, Hokkaido University, Sapporo, Japan
| | - Hitoshi Chiba
- Faculty of Health Sciences, Hokkaido University, Sapporo, Japan
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26
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van Rooij T, Daeichin V, Skachkov I, de Jong N, Kooiman K. Targeted ultrasound contrast agents for ultrasound molecular imaging and therapy. Int J Hyperthermia 2015; 31:90-106. [PMID: 25707815 DOI: 10.3109/02656736.2014.997809] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Ultrasound contrast agents (UCAs) are used routinely in the clinic to enhance contrast in ultrasonography. More recently, UCAs have been functionalised by conjugating ligands to their surface to target specific biomarkers of a disease or a disease process. These targeted UCAs (tUCAs) are used for a wide range of pre-clinical applications including diagnosis, monitoring of drug treatment, and therapy. In this review, recent achievements with tUCAs in the field of molecular imaging, evaluation of therapy, drug delivery, and therapeutic applications are discussed. We present the different coating materials and aspects that have to be considered when manufacturing tUCAs. Next to tUCA design and the choice of ligands for specific biomarkers, additional techniques are discussed that are applied to improve binding of the tUCAs to their target and to quantify the strength of this bond. As imaging techniques rely on the specific behaviour of tUCAs in an ultrasound field, it is crucial to understand the characteristics of both free and adhered tUCAs. To image and quantify the adhered tUCAs, the state-of-the-art techniques used for ultrasound molecular imaging and quantification are presented. This review concludes with the potential of tUCAs for drug delivery and therapeutic applications.
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Affiliation(s)
- Tom van Rooij
- Department of Biomedical Engineering, Thoraxcenter , Erasmus MC, Rotterdam , the Netherlands
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27
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Habel J, Ogbonna A, Larsen N, Cherré S, Kynde S, Midtgaard SR, Kinoshita K, Krabbe S, Jensen GV, Hansen JS, Almdal K, Hèlix-Nielsen C. Selecting analytical tools for characterization of polymersomes in aqueous solution. RSC Adv 2015. [DOI: 10.1039/c5ra16403f] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
We present 17 techniques to analyze polymersomes, in terms of their size, bilayer properties, elastic properties or surface charge.
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Affiliation(s)
- Joachim Habel
- Technical University of Denmark
- Department of Environmental Engineering
- 2800 Kgs. Lyngby
- Denmark
- Aquaporin A/S
| | | | - Nanna Larsen
- University of Copenhagen
- Copenhagen Biocenter
- 2200 Copenhagen
- Denmark
| | - Solène Cherré
- Technical University of Denmark
- Department of Micro- and Nanotechnology
- 2800 Kgs. Lyngby
- Denmark
| | - Søren Kynde
- University of Copenhagen
- Niels Bohr Institute
- 2100 Copenhagen
- Denmark
| | | | - Koji Kinoshita
- University of Southern Denmark
- Department of Physics
- Chemistry and Pharmacy
- 5230 Odense
- Denmark
| | - Simon Krabbe
- University of Copenhagen
- Department of Biology
- 2100 Copenhagen
- Denmark
| | | | | | - Kristoffer Almdal
- Technical University of Denmark
- Department of Micro- and Nanotechnology
- 2800 Kgs. Lyngby
- Denmark
| | - Claus Hèlix-Nielsen
- Technical University of Denmark
- Department of Environmental Engineering
- 2800 Kgs. Lyngby
- Denmark
- Aquaporin A/S
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28
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Li Y, Zhu C, Zhu J, Liang H, Chen D, Zhao H, Liu B. Nanomechanics of phospholipid LB film studied layer by layer with AFM. Chem Cent J 2014; 8:71. [PMID: 25614761 PMCID: PMC4279057 DOI: 10.1186/s13065-014-0071-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 11/11/2014] [Indexed: 11/21/2022] Open
Abstract
Background Phospholipid, a main component of cell membrane, has been explored as a model system of the cell membrane and temporary scaffold materials in recent studies. The mechanical properties of phospholipid layers are essentially interesting since it is involved in several biological processes. Results Here, the nanomechanical properties such as indentation force, adhesion force and DMT (Derjaguin-Müller-Toporov) modulus of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) Langmuir-Blodgett (LB) films were analyzed layer by layer with Atomic Force Microscope (AFM) under deionized water condition. Conclusions The penetration distances in the indentation force curves are equal to the thicknesses of phospholipid films, and the yield forces of DSPC LB films in deionized water are smaller than that of similar lipid films in buffered solutions due to the influence of ions. Moreover, the DMT modulus of upper layer DSPC LB film is different from that of monolayer DSPC LB film due to the influence of their different substrates. Our results suggest that environment such as surrounding ions and substrate will strongly influence the measured nano-mechanical properties of the lipid bilayer, especially that of the down layer. A process about the exploration of nanomechanics of DSPC LB film. ![]()
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Affiliation(s)
- Yinli Li
- Institute of Photo-biophysics, School of Physics and Electronic, Henan University, Kaifeng, 475004 Henan PR China
| | - Changjiang Zhu
- College of Software, Henan University, Kaifeng, 475004 Henan PR China
| | - Jichun Zhu
- Institute of Photo-biophysics, School of Physics and Electronic, Henan University, Kaifeng, 475004 Henan PR China
| | - Hao Liang
- Institute of Photo-biophysics, School of Physics and Electronic, Henan University, Kaifeng, 475004 Henan PR China
| | - Dong Chen
- Institute of Photo-biophysics, School of Physics and Electronic, Henan University, Kaifeng, 475004 Henan PR China
| | - Huiling Zhao
- Institute of Photo-biophysics, School of Physics and Electronic, Henan University, Kaifeng, 475004 Henan PR China
| | - Bo Liu
- Institute of Photo-biophysics, School of Physics and Electronic, Henan University, Kaifeng, 475004 Henan PR China
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29
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Boye K, Ligezowska A, Eble JA, Hoffmann B, Klösgen B, Merkel R. Two barriers or not? Dynamic force spectroscopy on the integrin α7β1 invasin complex. Biophys J 2014; 105:2771-80. [PMID: 24359749 DOI: 10.1016/j.bpj.2013.10.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 09/19/2013] [Accepted: 10/28/2013] [Indexed: 11/18/2022] Open
Abstract
Dynamic force spectroscopy was used to test force-induced dissociation of the complex between the integrin α7β1 and the bacterial protein invasin. Both proteins were used in truncated forms comprising the respective binding sites. Using the biomembrane force-probe, the bond system was exposed to 14 different loading rates ranging from 18 pN/s to 5.3 nN/s. At each rate, bond rupture spectra were collected. Median forces ranged from 8 to 72 pN. These showed two linear regimes when plotted against the logarithm of the force-loading rate. However, a statistical analysis of the full rupture force spectra including the detection limits of the setup showed that all measured data are well described by dissociation over a single barrier.
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Affiliation(s)
- Kristian Boye
- MEMPHYS-Center for Biomembrane Physics, Institute of Physics and Chemistry, University of Southern Denmark, Odense, Denmark
| | - Agnieszka Ligezowska
- MEMPHYS-Center for Biomembrane Physics, Institute of Physics and Chemistry, University of Southern Denmark, Odense, Denmark; Department of Physics, Jagiellonian University, Cracow, Poland; Institute of Complex Systems 7: Biomechanics, Forschungszentrum Jülich, Jülich, Germany
| | - Johannes A Eble
- Institute for Physiological Chemistry and Pathobiochemistry, University of Münster, Münster, Germany
| | - Bernd Hoffmann
- Institute of Complex Systems 7: Biomechanics, Forschungszentrum Jülich, Jülich, Germany
| | - Beate Klösgen
- MEMPHYS-Center for Biomembrane Physics, Institute of Physics and Chemistry, University of Southern Denmark, Odense, Denmark
| | - Rudolf Merkel
- Institute of Complex Systems 7: Biomechanics, Forschungszentrum Jülich, Jülich, Germany.
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30
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Neubauer MP, Poehlmann M, Fery A. Microcapsule mechanics: from stability to function. Adv Colloid Interface Sci 2014; 207:65-80. [PMID: 24345731 DOI: 10.1016/j.cis.2013.11.016] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 11/18/2013] [Accepted: 11/21/2013] [Indexed: 01/22/2023]
Abstract
Microcapsules are reviewed with special emphasis on the relevance of controlled mechanical properties for functional aspects. At first, assembly strategies are presented that allow control over the decisive geometrical parameters, diameter and wall thickness, which both influence the capsule's mechanical performance. As one of the most powerful approaches the layer-by-layer technique is identified. Subsequently, ensemble and, in particular, single-capsule deformation techniques are discussed. The latter generally provide more in-depth information and cover the complete range of applicable forces from smaller than pN to N. In a theory chapter, we illustrate the physics of capsule deformation. The main focus is on thin shell theory, which provides a useful approximation for many deformation scenarios. Finally, we give an overview of applications and future perspectives where the specific design of mechanical properties turns microcapsules into (multi-)functional devices, enriching especially life sciences and material sciences.
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31
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Trillo JV, Meijide F, Tato JV, Jover A, Soto VH, de Frutos S, Galantini L. Design of dialkyl surfactants from nitrilotriacetic acid as head group. RSC Adv 2014. [DOI: 10.1039/c3ra45543b] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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32
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Schäfer E, Kliesch TT, Janshoff A. Mechanical properties of giant liposomes compressed between two parallel plates: impact of artificial actin shells. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:10463-10474. [PMID: 23869855 DOI: 10.1021/la401969t] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The mechanical response of giant liposomes to compression between two parallel plates is investigated in the context of an artificial actin cortex adjacent to the inner leaflet of the bilayer. We found that nonlinear membrane theory neglecting the impact of bending sufficiently describes the mechanical response of liposomes consisting of fluid lipids to compression whereas the formation of an actin cortex or the use of gel-phase lipids generally leads to substantial stiffening of the shell. Giant vesicles are gently adsorbed on glassy surfaces and are compressed with tipless cantilevers using an atomic force microscope. Force-compression curves display a nonlinear response that allows us to determine the membrane tension σ0 and the area compressibility modulus K(A) by computing the contour of the vesicle as a function of the compression depth. The values for KA of fluid membranes correspond well to what is known from micropipet-suction experiments and computed from monitoring membrane undulations. The presence of a thick actin shell adjacent to the inner leaflet of the liposome membrane stiffens the system considerably, as mirrored in a significantly higher apparent area compressibility modulus.
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Affiliation(s)
- Edith Schäfer
- Institute of Physical Chemistry, Georg-August-University of Goettingen, Tammannstr. 6, 37077 Goettingen
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33
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Abstract
Liposome structures have a wide range of applications in biology, biochemistry, and biophysics. As a result, several methods for forming liposomes have been developed. This review provides a critical comparison of existing microfluidic technologies for forming liposomes and, when applicable, a comparison with their analogous macroscale counterparts. The properties of the generated liposomes, including size, size distribution, lamellarity, membrane composition, and encapsulation efficiency, form the basis for comparison. We hope that this critique will allow the reader to make an informed decision as to which method should be used for a given biological application.
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Affiliation(s)
- Dirk van Swaay
- Institute for Chemical and Bioengineering, ETH Zurich, Zurich, Switzerland
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Ozu M, Dorr RA, Gutiérrez F, Politi MT, Toriano R. Human AQP1 is a constitutively open channel that closes by a membrane-tension-mediated mechanism. Biophys J 2013; 104:85-95. [PMID: 23332061 DOI: 10.1016/j.bpj.2012.11.3818] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 11/16/2012] [Accepted: 11/27/2012] [Indexed: 12/17/2022] Open
Abstract
This work presents experimental results combined with model-dependent predictions regarding the osmotic-permeability regulation of human aquaporin 1 (hAQP1) expressed in Xenopus oocyte membranes. Membrane elastic properties were studied under fully controlled conditions to obtain a function that relates internal volume and pressure. This function was used to design a model in which osmotic permeability could be studied as a pressure-dependent variable. The model states that hAQP1 closes with membrane-tension increments. It is important to emphasize that the only parameter of the model is the initial osmotic permeability coefficient, which was obtained by model-dependent fitting. The model was contrasted with experimental records from emptied-out Xenopus laevis oocytes expressing hAQP1. Simulated results reproduce and predict volume changes in high-water-permeability membranes under hypoosmotic gradients of different magnitude, as well as under consecutive hypo- and hyperosmotic conditions. In all cases, the simulated permeability coefficients are similar to experimental values. Predicted pressure, volume, and permeability changes indicate that hAQP1 water channels can transit from a high-water-permeability state to a closed state. This behavior is reversible and occurs in a cooperative manner among monomers. We conclude that hAQP1 is a constitutively open channel that closes mediated by membrane-tension increments.
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Affiliation(s)
- Marcelo Ozu
- Laboratorio de Biomembranas, Departamento de Ciencias Fisiológicas, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
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35
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Nanoscale mechanical properties of lipid bilayers and their relevance in biomembrane organization and function. Micron 2012; 43:1212-23. [DOI: 10.1016/j.micron.2012.03.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Revised: 03/19/2012] [Accepted: 03/20/2012] [Indexed: 12/27/2022]
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Abstract
Tremendous progress has been made in recent years in understanding the working of the living cell, including its micro-anatomy, signalling networks, and regulation of genes. However, an understanding of cellular phenomena using fundamental laws starting from first principles is still very far away. Part of the reason is that a cell is an active and exquisitely complex system where every part is linked to the other. Thus, it is difficult or even impossible to design experiments that selectively and exclusively probe a chosen aspect of the cell. Various kinds of idealised systems and cell models have been used to circumvent this problem. An important example is a giant unilamellar vesicle (GUV, also called giant liposome), which provides a cell-sized confined volume to study biochemical reactions as well as self-assembly processes that occur on the membrane. The GUV membrane can be designed suitably to present selected, correctly-oriented cell-membrane proteins, whose mobility is confined to two dimensions. Here, we present recent advances in GUV design and the use of GUVs as cell models that enable quantitative testing leading to insight into the working of real cells. We briefly recapitulate important classical concepts in membrane biophysics emphasising the advantages and limitations of GUVs. We then present results obtained over the last decades using GUVs, choosing the formation of membrane domains and cell adhesion as examples for in-depth treatment. Insight into cell adhesion obtained using micro-interferometry is treated in detail. We conclude by summarising the open questions and possible future directions.
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Affiliation(s)
- Susanne F Fenz
- Leiden Institute of Physics: Physics of Life Processes, Leiden University, The Netherlands
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37
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Buchner Santos E, Morris JK, Glynos E, Sboros V, Koutsos V. Nanomechanical properties of phospholipid microbubbles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:5753-60. [PMID: 22313122 DOI: 10.1021/la204801u] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
This study uses atomic force microscopy (AFM) force-deformation (F-Δ) curves to investigate for the first time the Young's modulus of a phospholipid microbubble (MB) ultrasound contrast agent. The stiffness of the MBs was calculated from the gradient of the F-Δ curves, and the Young's modulus of the MB shell was calculated by employing two different mechanical models based on the Reissner and elastic membrane theories. We found that the relatively soft phospholipid-based MBs behave inherently differently to stiffer, polymer-based MBs [Glynos, E.; Koutsos, V.; McDicken, W. N.; Moran, C. M.; Pye, S. D.; Ross, J. A.; Sboros, V. Langmuir2009, 25 (13), 7514-7522] and that elastic membrane theory is the most appropriate of the models tested for evaluating the Young's modulus of the phospholipid shell, agreeing with values available for living cell membranes, supported lipid bilayers, and synthetic phospholipid vesicles. Furthermore, we show that AFM F-Δ curves in combination with a suitable mechanical model can assess the shell properties of phospholipid MBs. The "effective" Young's modulus of the whole bubble was also calculated by analysis using Hertz theory. This analysis yielded values which are in agreement with results from studies which used Hertz theory to analyze similar systems such as cells.
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Affiliation(s)
- Evelyn Buchner Santos
- Institute for Materials and Processes, School of Engineering, The University of Edinburgh, Edinburgh, United Kingdom
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38
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A finite element study of micropipette aspiration of single cells: effect of compressibility. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2012; 2012:192618. [PMID: 22400045 PMCID: PMC3287019 DOI: 10.1155/2012/192618] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Accepted: 10/31/2011] [Indexed: 11/17/2022]
Abstract
Micropipette aspiration (MA) technique has been widely used to measure the viscoelastic properties of different cell types. Cells experience nonlinear large deformations during the aspiration procedure. Neo-Hookean viscohyperelastic (NHVH) incompressible and compressible models were used to simulate the creep behavior of cells in MA, particularly accounting for the effect of compressibility, bulk relaxation, and hardening phenomena under large strain. In order to find optimal material parameters, the models were fitted to the experimental data available for mesenchymal stem cells. Finally, through Neo-Hookean porohyperelastic (NHPH) material model for the cell, the influence of fluid flow on the aspiration length of the cell was studied. Based on the results, we suggest that the compressibility and bulk relaxation/fluid flow play a significant role in the deformation behavior of single cells and should be taken into account in the analysis of the mechanics of cells.
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39
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Direct measurement of the mechanical properties of lipid phases in supported bilayers. Biophys J 2012; 102:L01-3. [PMID: 22225813 DOI: 10.1016/j.bpj.2011.11.4001] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 11/08/2011] [Accepted: 11/21/2011] [Indexed: 11/23/2022] Open
Abstract
Biological membranes define not only the cell boundaries but any compartment within the cell. To some extent, the functionality of membranes is related to the elastic properties of the lipid bilayer and the mechanical and hydrophobic matching with functional membrane proteins. Supported lipid bilayers (SLBs) are valid biomimetic systems for the study of membrane biophysical properties. Here, we acquired high-resolution topographic and quantitative mechanics data of phase-separated SLBs using a recent atomic force microscopy (AFM) imaging mode based on force measurements. This technique allows us to quantitatively map at high resolution the mechanical differences of lipid phases at different loading forces. We have applied this approach to evaluate the contribution of the underlying hard support in the determination of the elastic properties of SLBs and to determine the adequate indentation range for obtaining reliable elastic moduli values. At ~200 pN, elastic forces dominated the force-indentation response and the sample deformation was <20% of the bilayer thickness, at which the contribution of the support was found to be negligible. The obtained Young's modulus (E) of 19.3 MPa and 28.1 MPa allowed us to estimate the area stretch modulus (k(A)) as 106 pN/nm and 199 pN/nm and the bending stiffness (k(c)) as 18 k(B)T and 57 k(B)T for the liquid and gel phases, respectively.
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40
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Yi X, Shi X, Gao H. Cellular uptake of elastic nanoparticles. PHYSICAL REVIEW LETTERS 2011; 107:098101. [PMID: 21929271 DOI: 10.1103/physrevlett.107.098101] [Citation(s) in RCA: 293] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Indexed: 05/18/2023]
Abstract
A fundamental understanding of cell-nanomaterial interaction is of essential importance to nanomedicine and safe applications of nanotechnology. Here we investigate the adhesive wrapping of a soft elastic vesicle by a lipid membrane. We show that there exist a maximum of five distinct wrapping phases based on the stability of full wrapping, partial wrapping, and no wrapping states. The wrapping phases depend on the vesicle size, adhesion energy, surface tension of membrane, and bending rigidity ratio between vesicle and membrane. These results are of immediate interest to the study of vesicular transport and endocytosis or phagocytosis of elastic particles into cells.
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Affiliation(s)
- Xin Yi
- School of Engineering, Brown University, Providence, Rhode Island 02912, USA
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Ligezowska A, Boye K, Eble JA, Hoffmann B, Klösgen B, Merkel R. Mechanically enforced bond dissociation reports synergistic influence of Mn2+ and Mg2+ on the interaction between integrin α7β1 and invasin. J Mol Recognit 2011; 24:715-23. [DOI: 10.1002/jmr.1108] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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42
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Ovalle-García E, Torres-Heredia JJ, Antillón A, Ortega-Blake I. Simultaneous Determination of the Elastic Properties of the Lipid Bilayer by Atomic Force Microscopy: Bending, Tension, and Adhesion. J Phys Chem B 2011; 115:4826-33. [DOI: 10.1021/jp111985z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Erasmo Ovalle-García
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Apartado Postal 48-3, 62251, Cuernavaca, Morelos, México
| | - José J. Torres-Heredia
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Apartado Postal 48-3, 62251, Cuernavaca, Morelos, México
| | - Armando Antillón
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Apartado Postal 48-3, 62251, Cuernavaca, Morelos, México
| | - Iván Ortega-Blake
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Apartado Postal 48-3, 62251, Cuernavaca, Morelos, México
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Loritz HM, Kirchgessner N, Born S, Hoffmann B, Merkel R. Mechanical strength of specific bonds acting isolated or in pairs: a case study on engineered proteins. J Phys Chem B 2011; 115:2582-92. [PMID: 21355605 DOI: 10.1021/jp108280q] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The dynamic strength of multiple specific bonds exposed to external mechanical force is of significant interest for the understanding of biological adhesion. Exploiting the well-established FLAG tag technology, we engineered model proteins exhibiting no, one, or two identical binding sites for a monoclonal antibody. Bonds between these engineered proteins and the antibody were studied with dynamic force spectroscopy. On single bonds between a FLAG-tag and the antibody, we observed two regimes corresponding to two different activated complexes, that is, two intermediate states along the reaction path for bond breakage. Dynamic force spectroscopy on double bonds showed the same two regimes. The actual yield forces of double bonds slightly exceeded those of single bonds. A simplified kinetic model with analytical solutions was developed and used to interpret the measured spectra.
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Affiliation(s)
- H-M Loritz
- Institute of Bio- and Nanosystems 4: Biomechanics, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
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44
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McKendry JE, Grant CA, Johnson BRG, Coletta PL, Evans JA, Evans SD. Force spectroscopy of streptavidin conjugated lipid coated microbubbles. ACTA ACUST UNITED AC 2010. [DOI: 10.1179/175889610x12865266108541] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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