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Rehfeldt F, Weiss M. The random walker's toolbox for analyzing single-particle tracking data. Soft Matter 2023. [PMID: 37403841 DOI: 10.1039/d3sm00557g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/06/2023]
Abstract
Technological advances and a burst of new microscopy methods have boosted the use of quantitative tracking experiments, in Soft Matter and Biological Physics but also in the Life Sciences. However, in contrast to highly advanced measurement techniques and tracking tools, subsequent analyses of trajectories frequently do not exploit the data's full potential. Aiming especially at experimental laboratories and early-career scientists, we introduce, discuss, and apply in this Tutorial Review a large set of versatile measures that have proven to be useful for analyzing trajectories from single-particle tracking experiments, beyond a simple extraction of diffusion constants from mean squared displacements. To support a direct test and application of these measures, we supplement the text with a download package that comprises a low-threshold toolbox of ready-to-use routines and training data sets, hence relaxing the need to develop home-brewed solutions and/or to create suitable benchmark data.
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Affiliation(s)
- Florian Rehfeldt
- Experimental Physics I, University of Bayreuth, Universitätsstr. 30, D-95447 Bayreuth, Germany.
| | - Matthias Weiss
- Experimental Physics I, University of Bayreuth, Universitätsstr. 30, D-95447 Bayreuth, Germany.
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Hauke L, Isbaner S, Ghosh A, Guido I, Turco L, Chizhik AI, Gregor I, Karedla N, Rehfeldt F, Enderlein J. Metal-Induced Energy Transfer (MIET) for Live-Cell Imaging with Fluorescent Proteins. ACS Nano 2023; 17:8242-8251. [PMID: 36995274 PMCID: PMC10173696 DOI: 10.1021/acsnano.2c12372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Metal-induced energy transfer (MIET) imaging is an easy-to-implement super-resolution modality that achieves nanometer resolution along the optical axis of a microscope. Although its capability in numerous biological and biophysical studies has been demonstrated, its implementation for live-cell imaging with fluorescent proteins is still lacking. Here, we present its applicability and capabilities for live-cell imaging with fluorescent proteins in diverse cell types (adult human stem cells, human osteo-sarcoma cells, and Dictyostelium discoideum cells), and with various fluorescent proteins (GFP, mScarlet, RFP, YPet). We show that MIET imaging achieves nanometer axial mapping of living cellular and subcellular components across multiple time scales, from a few milliseconds to hours, with negligible phototoxic effects.
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Affiliation(s)
- Lara Hauke
- Third Institute of Physics - Biophysics, Georg August University, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Sebastian Isbaner
- Third Institute of Physics - Biophysics, Georg August University, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Arindam Ghosh
- Third Institute of Physics - Biophysics, Georg August University, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Isabella Guido
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
| | - Laura Turco
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
| | - Alexey I Chizhik
- Third Institute of Physics - Biophysics, Georg August University, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Ingo Gregor
- Third Institute of Physics - Biophysics, Georg August University, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Narain Karedla
- Third Institute of Physics - Biophysics, Georg August University, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Florian Rehfeldt
- Third Institute of Physics - Biophysics, Georg August University, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Jörg Enderlein
- Third Institute of Physics - Biophysics, Georg August University, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), Universitätsmedizin Göttingen, Robert-Koch-Strasse 40, 37075 Göttingen, Germany
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3
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Hauke L, Primeßnig A, Eltzner B, Radwitz J, Huckemann SF, Rehfeldt F. FilamentSensor 2.0: An open-source modular toolbox for 2D/3D cytoskeletal filament tracking. PLoS One 2023; 18:e0279336. [PMID: 36745610 PMCID: PMC9901806 DOI: 10.1371/journal.pone.0279336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 12/05/2022] [Indexed: 02/07/2023] Open
Abstract
Cytoskeletal pattern formation and structural dynamics are key to a variety of biological functions and a detailed and quantitative analysis yields insight into finely tuned and well-balanced homeostasis and potential pathological alterations. High content life cell imaging of fluorescently labeled cytoskeletal elements under physiological conditions is nowadays state-of-the-art and can record time lapse data for detailed experimental studies. However, systematic quantification of structures and in particular the dynamics (i.e. frame-to-frame tracking) are essential. Here, an unbiased, quantitative, and robust analysis workflow that can be highly automatized is needed. For this purpose we upgraded and expanded our fiber detection algorithm FilamentSensor (FS) to the FilamentSensor 2.0 (FS2.0) toolbox, allowing for automatic detection and segmentation of fibrous structures and the extraction of relevant data (center of mass, length, width, orientation, curvature) in real-time as well as tracking of these objects over time and cell event monitoring.
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Affiliation(s)
- Lara Hauke
- Third Institute of Physics—Biophysics, Georg-August-University Göttingen, Göttingen, Germany
- Institute of Pharmacology and Toxicology, University Medical Center, Göttingen, Germany
- CIDAS (Campus Institute Data Science), University of Göttingen, Göttingen, Germany
- * E-mail: (LH); (FR)
| | - Andreas Primeßnig
- Third Institute of Physics—Biophysics, Georg-August-University Göttingen, Göttingen, Germany
- Institute of Pharmacology and Toxicology, University Medical Center, Göttingen, Germany
| | - Benjamin Eltzner
- Research Group Computational Biomolecular Dynamics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
- Felix-Bernstein-Institute for Mathematical Statistics in the Biosciences, Georg-August-University Göttingen, Göttingen, Germany
| | - Jennifer Radwitz
- Third Institute of Physics—Biophysics, Georg-August-University Göttingen, Göttingen, Germany
- Department of Molecular Neurogenetics, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Stefan F. Huckemann
- Felix-Bernstein-Institute for Mathematical Statistics in the Biosciences, Georg-August-University Göttingen, Göttingen, Germany
| | - Florian Rehfeldt
- Third Institute of Physics—Biophysics, Georg-August-University Göttingen, Göttingen, Germany
- Experimental Physics I, University of Bayreuth, Bayreuth, Germany
- * E-mail: (LH); (FR)
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4
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Hauke L, Narasimhan S, Primeßnig A, Kaverina I, Rehfeldt F. A Focal Adhesion Filament Cross-correlation Kit for fast, automated segmentation and correlation of focal adhesions and actin stress fibers in cells. PLoS One 2021; 16:e0250749. [PMID: 34506490 PMCID: PMC8432882 DOI: 10.1371/journal.pone.0250749] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 08/23/2021] [Indexed: 11/18/2022] Open
Abstract
Focal adhesions (FAs) and associated actin stress fibers (SFs) form a complex mechanical system that mediates bidirectional interactions between cells and their environment. This linked network is essential for mechanosensing, force production and force transduction, thus directly governing cellular processes like polarization, migration and extracellular matrix remodeling. We introduce a tool for fast and robust coupled analysis of both FAs and SFs named the Focal Adhesion Filament Cross-correlation Kit (FAFCK). Our software can detect and record location, axes lengths, area, orientation, and aspect ratio of focal adhesion structures as well as the location, length, width and orientation of actin stress fibers. This enables users to automate analysis of the correlation of FAs and SFs and study the stress fiber system in a higher degree, pivotal to accurately evaluate transmission of mechanocellular forces between a cell and its surroundings. The FAFCK is particularly suited for unbiased and systematic quantitative analysis of FAs and SFs necessary for novel approaches of traction force microscopy that uses the additional data from the cellular side to calculate the stress distribution in the substrate. For validation and comparison with other tools, we provide datasets of cells of varying quality that are labelled by a human expert. Datasets and FAFCK are freely available as open source under the GNU General Public License.
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Affiliation(s)
- Lara Hauke
- Third Institute of Physics—Biophysics, Georg-August-University Göttingen, Göttingen, Germany
| | - Shwetha Narasimhan
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, United States of America
| | - Andreas Primeßnig
- Third Institute of Physics—Biophysics, Georg-August-University Göttingen, Göttingen, Germany
| | - Irina Kaverina
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, United States of America
- * E-mail: (IK); (FR)
| | - Florian Rehfeldt
- Third Institute of Physics—Biophysics, Georg-August-University Göttingen, Göttingen, Germany
- Experimental Physics I, University of Bayreuth, Bayreuth, Germany
- * E-mail: (IK); (FR)
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Pang B, Liu H, Rehfeldt F, Zhang K. High internal phase Pickering emulsions stabilized by dialdehyde amylopectin/chitosan complex nanoparticles. Carbohydr Polym 2021; 258:117655. [PMID: 33593543 DOI: 10.1016/j.carbpol.2021.117655] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 01/06/2021] [Accepted: 01/11/2021] [Indexed: 10/22/2022]
Abstract
High internal phase Pickering emulsions (HIPPEs) have attracted intensive interest for their great potential in foods, cosmetics, and biomedical applications. However, the relatively poor biodegradability and biocompatibility of inorganic and synthetic particulate emulsifiers greatly limit their practical applications. Here, a kind of biobased nanoparticles, namely dialdehyde amylopectin/chitosan complex nanoparticles (DAPCNPs), were fabricated by Schiff base reaction between dialdehyde amylopectin and chitosan with the assistance of ultrasonication treatment. The resultant DAPCNPs were employed to stabilize O/W HIPPEs with various oils, such as toluene, cyclohexane, styrene and edible rapeseed oil. Moreover, the resultant DAPCNPs-stabilized HIPPEs showed high stability under various environmental stresses (80 °C; 20 mM and 100 mM aqueous NaCl solutions). Furthermore, porous scaffolds were also fabricated by freeze-drying cyclohexane-in-water HIPPEs stabilized by DAPCNPs after the introduction of polyvinyl alcohol (PVA) into the continuous phase. These findings would give inspiration for designing polysaccharides-based nanoparticles to stabilize HIPPEs and improve their practical applications.
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Affiliation(s)
- Bo Pang
- Dept. Wood Technology and Wood-based Composites, Georg-August-University of Göttingen, Büsgenweg 4, Göttingen, D-37077, Germany
| | - Huan Liu
- Dept. Wood Technology and Wood-based Composites, Georg-August-University of Göttingen, Büsgenweg 4, Göttingen, D-37077, Germany
| | - Florian Rehfeldt
- Third Institute of Physics - Biophysics, University of Göttingen, Friedrich-Hund-Platz 1, D-37077Göttingen, Germany; Experimental Physics I, University of Bayreuth, Universitätsstrasse 30, Bayreuth, D-95440, Germany
| | - Kai Zhang
- Dept. Wood Technology and Wood-based Composites, Georg-August-University of Göttingen, Büsgenweg 4, Göttingen, D-37077, Germany.
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dos Santos Á, Cook AW, Gough RE, Schilling M, Olszok N, Brown I, Wang L, Aaron J, Martin-Fernandez ML, Rehfeldt F, Toseland CP. DNA damage alters nuclear mechanics through chromatin reorganization. Nucleic Acids Res 2020; 49:340-353. [PMID: 33330932 PMCID: PMC7797048 DOI: 10.1093/nar/gkaa1202] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 11/13/2020] [Accepted: 11/25/2020] [Indexed: 12/30/2022] Open
Abstract
DNA double-strand breaks drive genomic instability. However, it remains unknown how these processes may affect the biomechanical properties of the nucleus and what role nuclear mechanics play in DNA damage and repair efficiency. Here, we have used Atomic Force Microscopy to investigate nuclear mechanical changes, arising from externally induced DNA damage. We found that nuclear stiffness is significantly reduced after cisplatin treatment, as a consequence of DNA damage signalling. This softening was linked to global chromatin decondensation, which improves molecular diffusion within the organelle. We propose that this can increase recruitment for repair factors. Interestingly, we also found that reduction of nuclear tension, through cytoskeletal relaxation, has a protective role to the cell and reduces accumulation of DNA damage. Overall, these changes protect against further genomic instability and promote DNA repair. We propose that these processes may underpin the development of drug resistance.
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Affiliation(s)
- Ália dos Santos
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, UK
| | - Alexander W Cook
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, UK
| | - Rosemarie E Gough
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, UK
| | - Martin Schilling
- University of Göttingen, 3rd Institute of Physics—Biophysics, Göttingen 37077, Germany
| | - Nora A Olszok
- University of Göttingen, 3rd Institute of Physics—Biophysics, Göttingen 37077, Germany
| | - Ian Brown
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, UK
| | - Lin Wang
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell, Didcot, Oxford OX11 0QX, UK
| | - Jesse Aaron
- Advanced Imaging Center, HHMI Janelia Research Campus, Ashburn, VA 20147, USA
| | - Marisa L Martin-Fernandez
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell, Didcot, Oxford OX11 0QX, UK
| | - Florian Rehfeldt
- Correspondence may also be addressed to Florian Rehfeldt. Tel: +49 921 55 2504;
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Gortari AN, Bouchoule S, Cambril E, Cattoni A, Hauke L, Enderlein J, Rehfeldt F, Yacomotti A. Metasurface-based total internal reflection microscopy. Biomed Opt Express 2020; 11:1967-1976. [PMID: 32341860 PMCID: PMC7173909 DOI: 10.1364/boe.385276] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 02/21/2020] [Accepted: 03/06/2020] [Indexed: 06/01/2023]
Abstract
Recent years have seen a tremendous progress in the development of dielectric metasurfaces for visible light applications. Such metasurfaces are ultra-thin optical devices that can manipulate optical wavefronts in an arbitrary manner. Here, we present a newly developed metasurface which allows for coupling light into a microscopy coverslip to achieve total internal reflection (TIR) excitation. TIR fluorescence microscopy (TIRFM) is an important bioimaging technique used specifically to image cellular membranes or surface-localized molecules with high contrast and low background. Its most commonly used modality is objective-type TIRFM where one couples a focused excitation laser beam at the edge of the back focal aperture of an oil-immersion objective with high numerical aperture (N.A.) to realize a high incident-angle plane wave excitation above the critical TIR angle in sample space. However, this requires bulky and expensive objectives with a limited field-of-view (FOV). The metasurface which we describe here represents a low cost and easy-to-use alternative for TIRFM. It consists of periodic 2D arrays of asymmetric structures fabricated in TiO2 on borosilicate glass. It couples up to 70% of the incident non-reflected light into the first diffraction order at an angle of 65° in glass, which is above the critical TIR angle for a glass-water interface. Only ∼7% of the light leaks into propagating modes traversing the glass surface, thus minimizing any spurious background fluorescence originating far outside the glass substrate. We describe in detail design and fabrication of the metasurface, and validate is applicability for TIRFM by imaging immunostained human mesenchymal stem cells over a FOV of 200 µm x 200 µm. We envision that these kinds of metasurfaces can become a valuable tool for low-cost and TIRFM, offering high contrast, low photodamage, and high surface selectivity in fluorescence excitation and detection.
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Affiliation(s)
- Antu Nehuen Gortari
- Ctr. de Nanosciences et de Nanotechnologies, Univ. Paris-Sud, Univ. Paris-Saclay, France
| | - Sophie Bouchoule
- Ctr. de Nanosciences et de Nanotechnologies, Univ. Paris-Sud, Univ. Paris-Saclay, France
| | - Edmond Cambril
- Ctr. de Nanosciences et de Nanotechnologies, Univ. Paris-Sud, Univ. Paris-Saclay, France
| | - Andrea Cattoni
- Ctr. de Nanosciences et de Nanotechnologies, Univ. Paris-Sud, Univ. Paris-Saclay, France
| | - Lara Hauke
- Third Institute of Physics-Biophysics, Georg August University, Göttingen, Germany
| | - Jörg Enderlein
- Third Institute of Physics-Biophysics, Georg August University, Göttingen, Germany
| | - Florian Rehfeldt
- Third Institute of Physics-Biophysics, Georg August University, Göttingen, Germany
| | - Alejandro Yacomotti
- Ctr. de Nanosciences et de Nanotechnologies, Univ. Paris-Sud, Univ. Paris-Saclay, France
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Erpenbeck L, Gruhn AL, Kudryasheva G, Günay G, Meyer D, Busse J, Neubert E, Schön MP, Rehfeldt F, Kruss S. Effect of Adhesion and Substrate Elasticity on Neutrophil Extracellular Trap Formation. Front Immunol 2019; 10:2320. [PMID: 31632402 PMCID: PMC6781793 DOI: 10.3389/fimmu.2019.02320] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 09/13/2019] [Indexed: 12/29/2022] Open
Abstract
Neutrophils are the most abundant type of white blood cells. Upon stimulation, they are able to decondense and release their chromatin as neutrophil extracellular traps (NETs). This process (NETosis) is part of immune defense mechanisms but also plays an important role in many chronic and inflammatory diseases such as atherosclerosis, rheumatoid arthritis, diabetes, and cancer. For this reason, much effort has been invested into understanding biochemical signaling pathways in NETosis. However, the impact of the mechanical micro-environment and adhesion on NETosis is not well-understood. Here, we studied how adhesion and especially substrate elasticity affect NETosis. We employed polyacrylamide (PAA) gels with distinctly defined elasticities (Young's modulus E) within the physiologically relevant range from 1 to 128 kPa and coated the gels with integrin ligands (collagen I, fibrinogen). Neutrophils were cultured on these substrates and stimulated with potent inducers of NETosis: phorbol 12-myristate 13-acetate (PMA) and lipopolysaccharide (LPS). Interestingly, PMA-induced NETosis was neither affected by substrate elasticity nor by different integrin ligands. In contrast, for LPS stimulation, NETosis rates increased with increasing substrate elasticity (E > 20 kPa). LPS-induced NETosis increased with increasing cell contact area, while PMA-induced NETosis did not require adhesion at all. Furthermore, inhibition of phosphatidylinositide 3 kinase (PI3K), which is involved in adhesion signaling, completely abolished LPS-induced NETosis but only slightly decreased PMA-induced NETosis. In summary, we show that LPS-induced NETosis depends on adhesion and substrate elasticity while PMA-induced NETosis is completely independent of adhesion.
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Affiliation(s)
- Luise Erpenbeck
- Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen University, Göttingen, Germany
| | - Antonia Luise Gruhn
- Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen University, Göttingen, Germany
| | - Galina Kudryasheva
- Third Institute of Physics–Biophysics, Göttingen University, Göttingen, Germany
| | - Gökhan Günay
- Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen University, Göttingen, Germany
- Department of Chemistry, Institute of Physical Chemistry, Göttingen University, Göttingen, Germany
| | - Daniel Meyer
- Department of Chemistry, Institute of Physical Chemistry, Göttingen University, Göttingen, Germany
| | - Julia Busse
- Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen University, Göttingen, Germany
| | - Elsa Neubert
- Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen University, Göttingen, Germany
- Department of Chemistry, Institute of Physical Chemistry, Göttingen University, Göttingen, Germany
| | - Michael P. Schön
- Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen University, Göttingen, Germany
- Lower Saxony Institute of Occupational Dermatology, Göttingen, Germany
| | - Florian Rehfeldt
- Third Institute of Physics–Biophysics, Göttingen University, Göttingen, Germany
| | - Sebastian Kruss
- Department of Chemistry, Institute of Physical Chemistry, Göttingen University, Göttingen, Germany
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Huang H, Yang Y, Wang X, Rehfeldt F, Zhang K. Thermoresponsive Water Transportation in Dually Electrostatically Crosslinked Nanocomposite Hydrogels. Macromol Rapid Commun 2019; 40:e1900317. [PMID: 31433104 DOI: 10.1002/marc.201900317] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 08/09/2019] [Indexed: 12/24/2022]
Abstract
Controlling water transportation within hydrogels makes hydrogels attractive for diverse applications, but it is still a very challenging task. Herein, a novel type of dually electrostatically crosslinked nanocomposite hydrogel showing thermoresponsive water absorption, distribution, and dehydration processes are developed. The nanocomposite hydrogels are stabilized via electrostatic interactions between negatively charged poly(acrylic acid) and positively charged layered double hydroxide (LDH) nanosheets as well as poly(3-acrylamidopropyltrimethylammonium chloride). Both LDH nanosheets as crosslinkers and the surrounding temperatures played pivotal roles in tuning the water transportation within these nanocomposite hydrogels. By changing the surrounding temperature from 60 to 4 °C, these hydrogels showed widely adjustable swelling times between 2 and 45 days, while the dehydration process lasted between 7 and 27 days. A swift temperature decrease, for example, from 60 to 25 °C, generated supersaturation within these nanocomposite hydrogels, which further retarded the water transportation and distribution in hydrogel networks. Benefiting from modified water transportation and rapidly alternating water uptake capability during temperature change, pre-loaded compounds can be used to track and visualize these processes within nanocomposite hydrogels. At the same time, the discharge of water and loaded compounds from the interior of hydrogels demonstrates a thermoresponsive sustained release process.
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Affiliation(s)
- Heqin Huang
- Wood Technology and Wood Chemistry, University of Goettingen, Büsgenweg 4, D-37077, Göttingen, Germany
| | - Yang Yang
- Wood Technology and Wood Chemistry, University of Goettingen, Büsgenweg 4, D-37077, Göttingen, Germany
| | - Xiaojie Wang
- Wood Technology and Wood Chemistry, University of Goettingen, Büsgenweg 4, D-37077, Göttingen, Germany
| | - Florian Rehfeldt
- Third Institute of Physics-Biophysics, Faculty of Physics, University of Goettingen, Friedrich-Hund-Platz 1, D-37077, Göttingen, Germany
| | - Kai Zhang
- Wood Technology and Wood Chemistry, University of Goettingen, Büsgenweg 4, D-37077, Göttingen, Germany
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Gottschalk HM, Wecker T, Khattab MH, Fischer CV, Callizo J, Rehfeldt F, Lubjuhn R, Russmann C, Hoerauf H, van Oterendorp C. Lipid Emulsion-Based OCT Angiography for Ex Vivo Imaging of the Aqueous Outflow Tract. Invest Ophthalmol Vis Sci 2019; 60:397-406. [PMID: 30682210 DOI: 10.1167/iovs.18-25223] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Contrast agents applicable for optical coherence tomography (OCT) imaging are rare. The intrascleral aqueous drainage system would be a potential application for a contrast agent, because the aqueous veins are of small diameter and located deep inside the highly scattering sclera. We tested lipid emulsions (LEs) as candidate OCT contrast agents in vitro and ex vivo, including milk and the anesthetic substance Propofol. Methods Commercial OCT and OCT angiography (OCTA) devices were used. Maximum reflectivity and signal transmission of LE were determined in tube phantoms. Absorption spectra and light scattering was analyzed. The anterior chamber of enucleated porcine eyes was perfused with LEs, and OCTA imaging of the LEs drained via the aqueous outflow tract was performed. Results All LEs showed a significantly higher reflectivity than water (P < 0.001). Higher milk lipid content was positively correlated with maximum reflectivity and negatively with signal transmission. Propofol exhibited the best overall performance. Due to a high degree of signal fluctuation, OCTA could be applied for detection of LE. Compared with blood, the OCTA signal of Propofol was significantly stronger (P = 0.001). As a proof of concept, time-resolved aqueous angiography of porcine eyes was performed. The three-dimensional (3D) structure and dynamics of the aqueous outflow were significantly different from humans. Conclusions LEs induced a strong signal in OCT and OCTA. LE-based OCTA allowed the ability to obtain time-resolved 3D datasets of aqueous outflow. Possible interactions of LE with inner eye's structures need to be further investigated before in vivo application.
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Affiliation(s)
- Hanna M Gottschalk
- Department of Ophthalmology, University Medical Center, Göttingen, Germany
| | | | - Mohammed H Khattab
- Department of Ophthalmology, University Medical Center, Göttingen, Germany
| | | | - Josep Callizo
- Department of Ophthalmology, University Medical Center, Göttingen, Germany
| | - Florian Rehfeldt
- Third Institute of Physics, Biophysics, Georg-August-University, Göttingen, Germany
| | - Roswitha Lubjuhn
- Department of Anaesthesiology, University Medical Center, Göttingen, Germany
| | - Christoph Russmann
- Faculty of Natural Science and Technology, University of Applied Sciences and Arts, Göttingen, Germany.,Molecular Biomarkers Nano-Imaging Laboratory, Brigham and Women's Hospital, and Department of Radiology, Harvard Medical School, Boston, Massachusetts, United States
| | - Hans Hoerauf
- Department of Ophthalmology, University Medical Center, Göttingen, Germany
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Huang H, Wang X, Yu J, Chen Y, Ji H, Zhang Y, Rehfeldt F, Wang Y, Zhang K. Liquid-Behaviors-Assisted Fabrication of Multidimensional Birefringent Materials from Dynamic Hybrid Hydrogels. ACS Nano 2019; 13:3867-3874. [PMID: 30811180 DOI: 10.1021/acsnano.9b00551] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Liquid-solid transition is a widely used strategy to shape polymeric materials and encode their microstructures. However, it is still challenging to fully exploit liquid behaviors of material precursors. In particular, the dynamic and static liquid behaviors naturally conflict with each other, which makes it difficult to integrate their advantages in the same materials. Here, by utilizing a shear-thinning phenomenon in the dynamic hybrid hydrogels, we achieve a hydrodynamic alignment of cellulose nanocrystals (CNC) and preserve it in the relaxed hydrogel networks due to the much faster relaxation of polymer networks (within 500 s) than CNC after the unloading of external force. During the following drying process, the surface tension of hydrogels further enhances the orientation index of CNC up to 0.872 in confined geometry, and these anisotropic microstructures demonstrate highly tunable birefringence (up to 0.004 14). Due to the presence of the boundaries of dynamic hydrogels, diverse xerogels including fibers, films, and even complex three-dimensional structures with variable anisotropic microstructures can be fabricated without any external molds.
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Affiliation(s)
- Heqin Huang
- Wood Technology and Wood Chemistry , University of Goettingen , Büsgenweg 4 , D-37077 Göttingen , Germany
| | - Xiaojie Wang
- Wood Technology and Wood Chemistry , University of Goettingen , Büsgenweg 4 , D-37077 Göttingen , Germany
| | - Jinchao Yu
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering , Donghua University , Shanghai 201620 , People's Republic of China
- College of Textile and Clothing Engineering , Soochow University , Suzhou 215123 , People's Republic of China
| | - Ye Chen
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering , Donghua University , Shanghai 201620 , People's Republic of China
| | - Hong Ji
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering , Donghua University , Shanghai 201620 , People's Republic of China
| | - Yumei Zhang
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering , Donghua University , Shanghai 201620 , People's Republic of China
| | - Florian Rehfeldt
- Third Institute of Physics - Biophysics, Faculty of Physics , University of Goettingen , Friedrich-Hund-Platz 1 , D-37077 Göttingen , Germany
| | - Yong Wang
- Laboratory for Fluid Physics, Pattern Formation and Biocomplexity , Max Planck Institute for Dynamics and Self-Organization , Am Fassberg 17 , D-37077 Göttingen , Germany
| | - Kai Zhang
- Wood Technology and Wood Chemistry , University of Goettingen , Büsgenweg 4 , D-37077 Göttingen , Germany
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12
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Wang X, Huang H, Liu H, Rehfeldt F, Wang X, Zhang K. Multi‐Responsive Bilayer Hydrogel Actuators with Programmable and Precisely Tunable Motions. MACROMOL CHEM PHYS 2019. [DOI: 10.1002/macp.201970011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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13
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Wang X, Huang H, Liu H, Rehfeldt F, Wang X, Zhang K. Multi‐Responsive Bilayer Hydrogel Actuators with Programmable and Precisely Tunable Motions. MACROMOL CHEM PHYS 2019. [DOI: 10.1002/macp.201800562] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Xiaojie Wang
- Wood Technology and Wood ChemistryGeorg‐August‐University of Göttingen Büsgenweg 4 D‐37077 Göttingen Germany
| | - Heqin Huang
- Wood Technology and Wood ChemistryGeorg‐August‐University of Göttingen Büsgenweg 4 D‐37077 Göttingen Germany
| | - Huan Liu
- Wood Technology and Wood ChemistryGeorg‐August‐University of Göttingen Büsgenweg 4 D‐37077 Göttingen Germany
| | - Florian Rehfeldt
- Third Institute of Physics‐BiophysicsFaculty of PhysicsGeorg‐August‐University of Göttingen Friedrich‐Hund‐Platz 1 D‐37077 Göttingen Germany
| | - Xiaohui Wang
- State Key Laboratory of Pulp and Paper EngineeringSouth China University of Technology Guangzhou 510640 China
| | - Kai Zhang
- Wood Technology and Wood ChemistryGeorg‐August‐University of Göttingen Büsgenweg 4 D‐37077 Göttingen Germany
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14
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Ando T, Bhamidimarri SP, Brending N, Colin-York H, Collinson L, De Jonge N, de Pablo PJ, Debroye E, Eggeling C, Franck C, Fritzsche M, Gerritsen H, Giepmans BNG, Grunewald K, Hofkens J, Hoogenboom JP, Janssen KPF, Kaufman R, Klumpermann J, Kurniawan N, Kusch J, Liv N, Parekh V, Peckys DB, Rehfeldt F, Reutens DC, Roeffaers MBJ, Salditt T, Schaap IAT, Schwarz US, Verkade P, Vogel MW, Wagner R, Winterhalter M, Yuan H, Zifarelli G. The 2018 correlative microscopy techniques roadmap. J Phys D Appl Phys 2018; 51:443001. [PMID: 30799880 PMCID: PMC6372154 DOI: 10.1088/1361-6463/aad055] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 06/14/2018] [Accepted: 07/01/2018] [Indexed: 05/19/2023]
Abstract
Developments in microscopy have been instrumental to progress in the life sciences, and many new techniques have been introduced and led to new discoveries throughout the last century. A wide and diverse range of methodologies is now available, including electron microscopy, atomic force microscopy, magnetic resonance imaging, small-angle x-ray scattering and multiple super-resolution fluorescence techniques, and each of these methods provides valuable read-outs to meet the demands set by the samples under study. Yet, the investigation of cell development requires a multi-parametric approach to address both the structure and spatio-temporal organization of organelles, and also the transduction of chemical signals and forces involved in cell-cell interactions. Although the microscopy technologies for observing each of these characteristics are well developed, none of them can offer read-out of all characteristics simultaneously, which limits the information content of a measurement. For example, while electron microscopy is able to disclose the structural layout of cells and the macromolecular arrangement of proteins, it cannot directly follow dynamics in living cells. The latter can be achieved with fluorescence microscopy which, however, requires labelling and lacks spatial resolution. A remedy is to combine and correlate different readouts from the same specimen, which opens new avenues to understand structure-function relations in biomedical research. At the same time, such correlative approaches pose new challenges concerning sample preparation, instrument stability, region of interest retrieval, and data analysis. Because the field of correlative microscopy is relatively young, the capabilities of the various approaches have yet to be fully explored, and uncertainties remain when considering the best choice of strategy and workflow for the correlative experiment. With this in mind, the Journal of Physics D: Applied Physics presents a special roadmap on the correlative microscopy techniques, giving a comprehensive overview from various leading scientists in this field, via a collection of multiple short viewpoints.
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Affiliation(s)
- Toshio Ando
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa, Japan
| | | | | | - H Colin-York
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, OX3 9DS Oxford, United Kingdom
| | | | - Niels De Jonge
- INM-Leibniz Institute for New Materials, 66123 Saarbrücken, Germany
- Saarland University, 66123 Saarbrücken, Germany
| | - P J de Pablo
- Dpto. Física de la Materia Condensada Universidad Autónoma de Madrid 28049, Madrid, Spain
- Instituto de Física de la Materia Condensada IFIMAC, Universidad Autónoma de Madrid 28049, Madrid, Spain
| | - Elke Debroye
- KU Leuven, Department of Chemistry, B-3001 Heverlee, Belgium
| | - Christian Eggeling
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, OX3 9DS Oxford, United Kingdom
- Institute of Applied Optics, Friedrich-Schiller University, Jena, Germany
- Leibniz Institute of Photonic Technology (IPHT), Jena, Germany
| | - Christian Franck
- Department of Mechanical Engineering, University of Wisconsin-Madison, 1513 University Ave, Madison, WI 53706, United States of America
| | - Marco Fritzsche
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, OX3 9DS Oxford, United Kingdom
- Kennedy Institute for Rheumatology, University of Oxford, Oxford, United Kingdom
| | - Hans Gerritsen
- Debye Institute, Utrecht University, Utrecht, Netherlands
| | - Ben N G Giepmans
- Department of Cell Biology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | - Kay Grunewald
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
- Centre of Structural Systems Biology Hamburg and University of Hamburg, Hamburg, Germany
- Heinrich-Pette-Institute, Leibniz Institute of Virology, Hamburg, Germany
| | - Johan Hofkens
- KU Leuven, Department of Chemistry, B-3001 Heverlee, Belgium
| | | | | | - Rainer Kaufman
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
- Centre of Structural Systems Biology Hamburg and University of Hamburg, Hamburg, Germany
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Judith Klumpermann
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Heidelberglaan 100, 3584CX Utrecht, Netherlands
| | - Nyoman Kurniawan
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
| | | | - Nalan Liv
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Heidelberglaan 100, 3584CX Utrecht, Netherlands
| | - Viha Parekh
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Diana B Peckys
- Faculty of Medicine, Saarland University, 66421 Homburg, Germany
| | - Florian Rehfeldt
- University of Göttingen, Third Institute of Physics-Biophysics, 37077 Göttingen, Germany
| | - David C Reutens
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
| | | | - Tim Salditt
- University of Göttingen, Institute for X-Ray Physics, 37077 Göttingen, Germany
| | - Iwan A T Schaap
- SmarAct GmbH, Schütte-Lanz-Str. 9, D-26135 Oldenburg, Germany
| | - Ulrich S Schwarz
- Institute for Theoretical Physics and BioQuant, Heidelberg University, Heidelberg, Germany
| | - Paul Verkade
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Michael W Vogel
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Richard Wagner
- Department of Life Sciences & Chemistry, Jacobs University, Bremen, Germany
| | | | - Haifeng Yuan
- KU Leuven, Department of Chemistry, B-3001 Heverlee, Belgium
| | - Giovanni Zifarelli
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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15
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Chizhik AM, Wollnik C, Ruhlandt D, Karedla N, Chizhik AI, Hauke L, Hähnel D, Gregor I, Enderlein J, Rehfeldt F. Dual-color metal-induced and Förster resonance energy transfer for cell nanoscopy. Mol Biol Cell 2018; 29:846-851. [PMID: 29444956 PMCID: PMC5905297 DOI: 10.1091/mbc.e17-05-0314] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
We report a novel method, dual-color axial nanometric localization by metal--induced energy transfer, and combine it with Förster resonance energy transfer (FRET) for resolving structural details in cells on the molecular level. We demonstrate the capability of this method on cytoskeletal elements and adhesions in human mesenchymal stem cells. Our approach is based on fluorescence-lifetime-imaging microscopy and allows for precise determination of the three-dimensional architecture of stress fibers anchoring at focal adhesions, thus yielding crucial information to understand cell-matrix mechanics. In addition to resolving nanometric structural details along the z-axis, we use FRET to gain precise information on the distance between actin and vinculin at focal adhesions.
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Affiliation(s)
- Anna M Chizhik
- Third Institute of Physics-Biophysics, University of Göttingen, 37077 Göttingen, Germany
| | - Carina Wollnik
- Third Institute of Physics-Biophysics, University of Göttingen, 37077 Göttingen, Germany
| | - Daja Ruhlandt
- Third Institute of Physics-Biophysics, University of Göttingen, 37077 Göttingen, Germany
| | - Narain Karedla
- Third Institute of Physics-Biophysics, University of Göttingen, 37077 Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37077 Göttingen, Germany
| | - Alexey I Chizhik
- Third Institute of Physics-Biophysics, University of Göttingen, 37077 Göttingen, Germany
| | - Lara Hauke
- Third Institute of Physics-Biophysics, University of Göttingen, 37077 Göttingen, Germany
| | - Dirk Hähnel
- Third Institute of Physics-Biophysics, University of Göttingen, 37077 Göttingen, Germany
| | - Ingo Gregor
- Third Institute of Physics-Biophysics, University of Göttingen, 37077 Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37077 Göttingen, Germany
| | - Jörg Enderlein
- Third Institute of Physics-Biophysics, University of Göttingen, 37077 Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37077 Göttingen, Germany
| | - Florian Rehfeldt
- Third Institute of Physics-Biophysics, University of Göttingen, 37077 Göttingen, Germany
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16
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Heidemann KM, Sageman-Furnas AO, Sharma A, Rehfeldt F, Schmidt CF, Wardetzky M. Topology determines force distributions in one-dimensional random spring networks. Phys Rev E 2018; 97:022306. [PMID: 29548075 DOI: 10.1103/physreve.97.022306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Indexed: 11/07/2022]
Abstract
Networks of elastic fibers are ubiquitous in biological systems and often provide mechanical stability to cells and tissues. Fiber-reinforced materials are also common in technology. An important characteristic of such materials is their resistance to failure under load. Rupture occurs when fibers break under excessive force and when that failure propagates. Therefore, it is crucial to understand force distributions. Force distributions within such networks are typically highly inhomogeneous and are not well understood. Here we construct a simple one-dimensional model system with periodic boundary conditions by randomly placing linear springs on a circle. We consider ensembles of such networks that consist of N nodes and have an average degree of connectivity z but vary in topology. Using a graph-theoretical approach that accounts for the full topology of each network in the ensemble, we show that, surprisingly, the force distributions can be fully characterized in terms of the parameters (N,z). Despite the universal properties of such (N,z) ensembles, our analysis further reveals that a classical mean-field approach fails to capture force distributions correctly. We demonstrate that network topology is a crucial determinant of force distributions in elastic spring networks.
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Affiliation(s)
- Knut M Heidemann
- Institute for Numerical and Applied Mathematics, University of Goettingen, 37083 Goettingen, Germany
| | - Andrew O Sageman-Furnas
- Institute for Numerical and Applied Mathematics, University of Goettingen, 37083 Goettingen, Germany
| | - Abhinav Sharma
- Third Institute of Physics - Biophysics, University of Goettingen, 37077 Goettingen, Germany.,Leibniz Institute of Polymer Research Dresden, 01069 Dresden, Germany
| | - Florian Rehfeldt
- Third Institute of Physics - Biophysics, University of Goettingen, 37077 Goettingen, Germany
| | - Christoph F Schmidt
- Third Institute of Physics - Biophysics, University of Goettingen, 37077 Goettingen, Germany
| | - Max Wardetzky
- Institute for Numerical and Applied Mathematics, University of Goettingen, 37083 Goettingen, Germany
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17
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Narayanan P, Hütte M, Kudryasheva G, Taberner FJ, Lechner SG, Rehfeldt F, Gomez-Varela D, Schmidt M. Myotubularin related protein-2 and its phospholipid substrate PIP 2 control Piezo2-mediated mechanotransduction in peripheral sensory neurons. eLife 2018. [PMID: 29521261 PMCID: PMC5898911 DOI: 10.7554/elife.32346] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Piezo2 ion channels are critical determinants of the sense of light touch in vertebrates. Yet, their regulation is only incompletely understood. We recently identified myotubularin related protein-2 (Mtmr2), a phosphoinositide (PI) phosphatase, in the native Piezo2 interactome of murine dorsal root ganglia (DRG). Here, we demonstrate that Mtmr2 attenuates Piezo2-mediated rapidly adapting mechanically activated (RA-MA) currents. Interestingly, heterologous Piezo1 and other known MA current subtypes in DRG appeared largely unaffected by Mtmr2. Experiments with catalytically inactive Mtmr2, pharmacological blockers of PI(3,5)P2 synthesis, and osmotic stress suggest that Mtmr2-dependent Piezo2 inhibition involves depletion of PI(3,5)P2. Further, we identified a PI(3,5)P2 binding region in Piezo2, but not Piezo1, that confers sensitivity to Mtmr2 as indicated by functional analysis of a domain-swapped Piezo2 mutant. Altogether, our results propose local PI(3,5)P2 modulation via Mtmr2 in the vicinity of Piezo2 as a novel mechanism to dynamically control Piezo2-dependent mechanotransduction in peripheral sensory neurons. We often take our sense of touch for granted. Yet, our every-day life greatly depends on the ability to perceive our environment to alert us of danger or to further social interactions, such as mother-child bonding. Our sense of touch relies on the conversion of mechanical stimuli to electrical signals (this is known as mechanotransduction), which then travel to brain to be processed. This task is fulfilled by specific ion channels called Piezo2, which are activated when cells are exposed to pressure and other mechanical forces. These channels can be found in sensory nerves and specialized structures in the skin, where they help to detect physical contact, roughness of surfaces and the position of our body parts. It is still not clear how Piezo2 channels are regulated but previous research by several laboratories suggests that they work in conjunction with other proteins. One of these proteins is the myotubularin related protein-2, or Mtmr2 for short. Now, Narayanan et al. – including some of the researchers involved in the previous research – set out to advance our understanding of the molecular basis of touch and looked more closely at Mtmr2. To test if Mtmr2 played a role in mechanotransduction, Narayanan et al. both increased and reduced the levels of this protein in sensory neurons of mice grown in the laboratory. When Mtmr2 levels were low, the activity of Piezo2 channels increased. However, when the protein levels were high, Piezo2 channels were inhibited. These results suggest that Mtmr2 can control the activity of Piezo2. Further experiments, in which Mtmr2 was genetically modified or sensory neurons were treated with chemicals, revealed that Mtmr2 reduces a specific fatty acid in the membrane of nerve cells, which in turn attenuates the activity of Piezo2. This study identified Mtmr2 and distinct fatty acids in the cell membrane as new components of the complex setup required for the sense of touch. A next step will be to test if these molecules also influence the activity of Piezo2 when the skin has become injured or upon inflammation.
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Affiliation(s)
- Pratibha Narayanan
- Emmy Noether-Group Somatosensory Signaling and Systems Biology, Max Planck Institute for Experimental Medicine, Goettingen, Germany
| | - Meike Hütte
- Emmy Noether-Group Somatosensory Signaling and Systems Biology, Max Planck Institute for Experimental Medicine, Goettingen, Germany
| | - Galina Kudryasheva
- Third Institute of Physics - Biophysics, University of Goettingen, Goettingen, Germany
| | | | | | - Florian Rehfeldt
- Third Institute of Physics - Biophysics, University of Goettingen, Goettingen, Germany
| | - David Gomez-Varela
- Emmy Noether-Group Somatosensory Signaling and Systems Biology, Max Planck Institute for Experimental Medicine, Goettingen, Germany
| | - Manuela Schmidt
- Emmy Noether-Group Somatosensory Signaling and Systems Biology, Max Planck Institute for Experimental Medicine, Goettingen, Germany
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18
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Heidemann KM, Sageman-Furnas AO, Sharma A, Rehfeldt F, Schmidt CF, Wardetzky M. Topology Counts: Force Distributions in Circular Spring Networks. Phys Rev Lett 2018; 120:068001. [PMID: 29481239 DOI: 10.1103/physrevlett.120.068001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Indexed: 06/08/2023]
Abstract
Filamentous polymer networks govern the mechanical properties of many biological materials. Force distributions within these networks are typically highly inhomogeneous, and, although the importance of force distributions for structural properties is well recognized, they are far from being understood quantitatively. Using a combination of probabilistic and graph-theoretical techniques, we derive force distributions in a model system consisting of ensembles of random linear spring networks on a circle. We show that characteristic quantities, such as the mean and variance of the force supported by individual springs, can be derived explicitly in terms of only two parameters: (i) average connectivity and (ii) number of nodes. Our analysis shows that a classical mean-field approach fails to capture these characteristic quantities correctly. In contrast, we demonstrate that network topology is a crucial determinant of force distributions in an elastic spring network. Our results for 1D linear spring networks readily generalize to arbitrary dimensions.
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Affiliation(s)
- Knut M Heidemann
- Institute for Numerical and Applied Mathematics, University of Goettingen, 37083 Goettingen, Germany
| | - Andrew O Sageman-Furnas
- Institute for Numerical and Applied Mathematics, University of Goettingen, 37083 Goettingen, Germany
| | - Abhinav Sharma
- Third Institute of Physics - Biophysics, University of Goettingen, 37077 Goettingen, Germany
- Leibniz Institute of Polymer Research Dresden, 01069 Dresden, Germany
| | - Florian Rehfeldt
- Third Institute of Physics - Biophysics, University of Goettingen, 37077 Goettingen, Germany
| | - Christoph F Schmidt
- Third Institute of Physics - Biophysics, University of Goettingen, 37077 Goettingen, Germany
| | - Max Wardetzky
- Institute for Numerical and Applied Mathematics, University of Goettingen, 37083 Goettingen, Germany
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19
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Franz J, Grünebaum J, Schäfer M, Mulac D, Rehfeldt F, Langer K, Kramer A, Riethmüller C. Rhombic organization of microvilli domains found in a cell model of the human intestine. PLoS One 2018; 13:e0189970. [PMID: 29320535 PMCID: PMC5761853 DOI: 10.1371/journal.pone.0189970] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 12/05/2017] [Indexed: 01/22/2023] Open
Abstract
Symmetry is rarely found on cellular surfaces. An exception is the brush border of microvilli, which are essential for the proper function of transport epithelia. In a healthy intestine, they appear densely packed as a 2D-hexagonal lattice. For in vitro testing of intestinal transport the cell line Caco-2 has been established. As reported by electron microscopy, their microvilli arrange primarily in clusters developing secondly into a 2D-hexagonal lattice. Here, atomic force microscopy (AFM) was employed under aqueous buffer conditions on Caco-2 cells, which were cultivated on permeable filter membranes for optimum differentiation. For analysis, the exact position of each microvillus was detected by computer vision; subsequent Fourier transformation yielded the type of 2D-lattice. It was confirmed, that Caco-2 cells can build a hexagonal lattice of microvilli and form clusters. Moreover, a second type of arrangement was discovered, namely a rhombic lattice, which appeared at sub-maximal densities of microvilli with (29 ± 4) microvilli / μm2. Altogether, the findings indicate the existence of a yet undescribed pattern in cellular organization.
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Affiliation(s)
- Jonas Franz
- Faculty of Physics, Georg-August-Universität, Göttingen, Germany
- Max Planck Institute for Dynamics and Self-Organization, Theoretical Neurophysics, Göttingen, Germany
| | - Jonas Grünebaum
- Institute for Pharmaceutical Technology and Biopharmacy, University of Münster, Münster, Germany
| | - Marcus Schäfer
- nanoAnalytics GmbH, Centre for Nanotechnology, Münster, Germany
| | - Dennis Mulac
- Institute for Pharmaceutical Technology and Biopharmacy, University of Münster, Münster, Germany
| | - Florian Rehfeldt
- Third Institute of Physics—Biophysics, Georg-August-Universität, Göttingen, Germany
| | - Klaus Langer
- Institute for Pharmaceutical Technology and Biopharmacy, University of Münster, Münster, Germany
| | - Armin Kramer
- Serend-ip GmbH, Centre for Nanotechnology, Münster, Germany
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20
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Buxboim A, Irianto J, Swift J, Athirasala A, Shin JW, Rehfeldt F, Discher DE. Coordinated increase of nuclear tension and lamin-A with matrix stiffness outcompetes lamin-B receptor that favors soft tissue phenotypes. Mol Biol Cell 2017; 28:3333-3348. [PMID: 28931598 PMCID: PMC5687034 DOI: 10.1091/mbc.e17-06-0393] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 09/06/2017] [Accepted: 09/13/2017] [Indexed: 12/31/2022] Open
Abstract
Matrix stiffness that is sensed by a cell or measured by a purely physical probe reflects the intrinsic elasticity of the matrix and also how thick or thin the matrix is. Here, mesenchymal stem cells (MSCs) and their nuclei spread in response to thickness-corrected matrix microelasticity, with increases in nuclear tension and nuclear stiffness resulting from increases in myosin-II and lamin-A,C. Linearity between the widely varying projected area of a cell and its nucleus across many matrices, timescales, and myosin-II activity levels indicates a constant ratio of nucleus-to-cell volume, despite MSCs' lineage plasticity. Nuclear envelope fluctuations are suppressed on the stiffest matrices, and fluctuation spectra reveal a high nuclear tension that matches trends from traction force microscopy and from increased lamin-A,C. Transcriptomes of many diverse tissues and MSCs further show that lamin-A,C's increase with tissue or matrix stiffness anti-correlates with lamin-B receptor (LBR), which contributes to lipid/sterol biosynthesis. Adipogenesis (a soft lineage) indeed increases LBR:lamin-A,C protein stoichiometry in MSCs versus osteogenesis (stiff). The two factors compete for lamin-B in response to matrix elasticity, knockdown, myosin-II inhibition, and even constricted migration that disrupts and segregates lamins in situ. Matrix stiffness-driven contractility thus tenses the nucleus to favor lamin-A,C accumulation and suppress soft tissue phenotypes.
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Affiliation(s)
- Amnon Buxboim
- Molecular and Cell Biophysics Laboratory, University of Pennsylvania, Philadelphia, PA 19104
- Department/Graduate Group of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104
| | - Jerome Irianto
- Molecular and Cell Biophysics Laboratory, University of Pennsylvania, Philadelphia, PA 19104
| | - Joe Swift
- Molecular and Cell Biophysics Laboratory, University of Pennsylvania, Philadelphia, PA 19104
| | - Avathamsa Athirasala
- Molecular and Cell Biophysics Laboratory, University of Pennsylvania, Philadelphia, PA 19104
| | - Jae-Won Shin
- Molecular and Cell Biophysics Laboratory, University of Pennsylvania, Philadelphia, PA 19104
| | - Florian Rehfeldt
- Molecular and Cell Biophysics Laboratory, University of Pennsylvania, Philadelphia, PA 19104
| | - Dennis E Discher
- Molecular and Cell Biophysics Laboratory, University of Pennsylvania, Philadelphia, PA 19104
- Department/Graduate Group of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104
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21
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Huang H, Wang Y, Wang X, Rehfeldt F, Zhang K. Robust Heterogeneous Hydrogels with Dynamic Nanocrystal-Polymer Interface. Macromol Rapid Commun 2017; 38. [DOI: 10.1002/marc.201600810] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Revised: 02/17/2017] [Indexed: 01/02/2023]
Affiliation(s)
- Heqin Huang
- Wood Technology and Wood Chemistry; Georg-August-University of Göttingen; Büsgenweg 4 D-37077 Göttingen Germany
| | - Yonggui Wang
- Wood Technology and Wood Chemistry; Georg-August-University of Göttingen; Büsgenweg 4 D-37077 Göttingen Germany
| | - Xiaojie Wang
- Wood Technology and Wood Chemistry; Georg-August-University of Göttingen; Büsgenweg 4 D-37077 Göttingen Germany
| | - Florian Rehfeldt
- Third Institute of Physics - Biophysics; Faculty of Physics; Georg-August-University of Göttingen; Friedrich-Hund-Platz 1 D-37077 Göttingen Germany
| | - Kai Zhang
- Wood Technology and Wood Chemistry; Georg-August-University of Göttingen; Büsgenweg 4 D-37077 Göttingen Germany
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22
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Kaliman S, Jayachandran C, Rehfeldt F, Smith AS. Limits of Applicability of the Voronoi Tessellation Determined by Centers of Cell Nuclei to Epithelium Morphology. Front Physiol 2016; 7:551. [PMID: 27932987 PMCID: PMC5122581 DOI: 10.3389/fphys.2016.00551] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 11/03/2016] [Indexed: 01/13/2023] Open
Abstract
It is well accepted that cells in the tissue can be regarded as tiles tessellating space. A number of approaches were developed to find an appropriate mathematical description of such cell tiling. A particularly useful approach is the so called Voronoi tessellation, built from centers of mass of the cell nuclei (CMVT), which is commonly used for estimating the morphology of cells in epithelial tissues. However, a study providing a statistically sound analysis of this method's accuracy is not available in the literature. We addressed this issue here by comparing a number of morphological measures of the cells, including area, perimeter, and elongation obtained from such a tessellation with identical measures extracted from direct imaging acquired by staining the cell membranes. After analyzing the shapes of 15,000 MDCK II epithelial cells under several conditions, we find that CMVT reasonably well reproduces many of the morphological properties of the tissue with an error that is between 10 and 15%. Moreover, cross-correlations between different morphological measures are reproduced qualitatively correctly by this method. However, all of the properties including the cell perimeters, number of neighbors, and anisotropy measures often suffer from systematic or size dependent errors. These discrepancies originate from the polygonal nature of the tessellation which sets the limits of the applicability of CMVT.
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Affiliation(s)
- Sara Kaliman
- Physics Underlying Life Sciences Group, Institute for Theoretical Physics and Cluster of Excellence: Engineering of Advanced Materials, Friedrich Alexander University Erlangen-Nürnberg Erlangen, Germany
| | | | - Florian Rehfeldt
- Third Institute of Physics-Biophysics, Georg-August-University Göttingen, Germany
| | - Ana-Sunčana Smith
- Physics Underlying Life Sciences Group, Institute for Theoretical Physics and Cluster of Excellence: Engineering of Advanced Materials, Friedrich Alexander University Erlangen-NürnbergErlangen, Germany; Group for Computational Life Sciences, Division of Physical Chemistry, Institute Ruđer BoškovićZagreb, Croatia
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23
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Huckemann S, Kim KR, Munk A, Rehfeldt F, Sommerfeld M, Weickert J, Wollnik C. The circular SiZer, inferred persistence of shape parameters and application to early stem cell differentiation. BERNOULLI 2016. [DOI: 10.3150/15-bej722] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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24
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Abstract
Cells are sensitive to mechanical cues from their environment and at the same time generate and transmit forces to their surroundings. To test quantitatively forces generated by cells not attached to a substrate, we used a dual optical trap to suspend 3T3 fibroblasts between two fibronectin-coated beads. In this simple geometry, we measured both the cells' elastic properties and the force fluctuations they generate with high bandwidth. Cell stiffness decreased substantially with both myosin inhibition by blebbistatin and serum-starvation, but not with microtubule depolymerization by nocodazole. We show that cortical forces generated by non-muscle myosin II deform the cell from its rounded shape in the frequency regime from 0.1 to 10 Hz. The amplitudes of these forces were strongly reduced by blebbistatin and serum starvation, but were unaffected by depolymerization of microtubules. Force fluctuations show a spectrum that is characteristic for an elastic network activated by random sustained stresses with abrupt transitions.
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Affiliation(s)
- Florian Schlosser
- Third Institute of Physics-Biophysics, Georg August University, 37077 Göttingen, Germany
| | - Florian Rehfeldt
- Third Institute of Physics-Biophysics, Georg August University, 37077 Göttingen, Germany
| | - Christoph F Schmidt
- Third Institute of Physics-Biophysics, Georg August University, 37077 Göttingen, Germany
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25
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Abstract
Mechanotransduction - how cells sense physical forces and translate them into biochemical and biological responses - is a vibrant and rapidly-progressing field, and is important for a broad range of biological phenomena. This forum explores the role of mechanotransduction in a variety of cellular activities and highlights intriguing questions that deserve further attention.
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Affiliation(s)
- Ewa K Paluch
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, UK.
| | - Celeste M Nelson
- Chemical & Biological Engineering, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ, 08544, USA
| | - Nicolas Biais
- Biology Department, Brooklyn College and the Graduate Center of the City University of New York, 2900 Bedford avenue, Brooklyn, NY, 11210, USA
| | - Ben Fabry
- Department of Physics, University of Erlangen-Nuremberg, Henkestrasse 91, 91052, Erlangen, Germany
| | - Jens Moeller
- Department of Mechanical Engineering, Microsystems Laboratory, Stanford University, 496 Lomita Mall, Durand Building Rm 102, Stanford, CA, 94305, USA
| | - Beth L Pruitt
- Department of Mechanical Engineering and Molecular and Cellular Physiology, Microsystems Laboratory, Stanford University, by courtesy, 496 Lomita Mall, Durand Building Rm 213, Stanford, CA, 94305, USA
| | - Carina Wollnik
- Georg-August-University, 3rd Institute of Physics - Biophysics, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Galina Kudryasheva
- Georg-August-University, 3rd Institute of Physics - Biophysics, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Florian Rehfeldt
- Georg-August-University, 3rd Institute of Physics - Biophysics, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Walter Federle
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
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26
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Eltzner B, Wollnik C, Gottschlich C, Huckemann S, Rehfeldt F. The filament sensor for near real-time detection of cytoskeletal fiber structures. PLoS One 2015; 10:e0126346. [PMID: 25996921 PMCID: PMC4440737 DOI: 10.1371/journal.pone.0126346] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 04/01/2015] [Indexed: 12/18/2022] Open
Abstract
A reliable extraction of filament data from microscopic images is of high interest in the analysis of acto-myosin structures as early morphological markers in mechanically guided differentiation of human mesenchymal stem cells and the understanding of the underlying fiber arrangement processes. In this paper, we propose the filament sensor (FS), a fast and robust processing sequence which detects and records location, orientation, length, and width for each single filament of an image, and thus allows for the above described analysis. The extraction of these features has previously not been possible with existing methods. We evaluate the performance of the proposed FS in terms of accuracy and speed in comparison to three existing methods with respect to their limited output. Further, we provide a benchmark dataset of real cell images along with filaments manually marked by a human expert as well as simulated benchmark images. The FS clearly outperforms existing methods in terms of computational runtime and filament extraction accuracy. The implementation of the FS and the benchmark database are available as open source.
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Affiliation(s)
- Benjamin Eltzner
- Institute for Mathematical Stochastics, Georg-August-University, 37077 Göttingen, Germany
| | - Carina Wollnik
- Third Institute of Physics-Biophysics, Georg-August-University, 37077 Göttingen, Germany
| | - Carsten Gottschlich
- Institute for Mathematical Stochastics, Georg-August-University, 37077 Göttingen, Germany
| | - Stephan Huckemann
- Institute for Mathematical Stochastics, Georg-August-University, 37077 Göttingen, Germany
| | - Florian Rehfeldt
- Third Institute of Physics-Biophysics, Georg-August-University, 37077 Göttingen, Germany
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27
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Heidemann KM, Sharma A, Rehfeldt F, Schmidt CF, Wardetzky M. Elasticity of 3D networks with rigid filaments and compliant crosslinks. Soft Matter 2015; 11:343-354. [PMID: 25408437 DOI: 10.1039/c4sm01789g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Disordered filamentous networks with compliant crosslinks exhibit a low linear elastic shear modulus at small strains, but stiffen dramatically at high strains. Experiments have shown that the elastic modulus can increase by up to three orders of magnitude while the networks withstand relatively large stresses without rupturing. Here, we perform an analytical and numerical study on model networks in three dimensions. Our model consists of a collection of randomly oriented rigid filaments connected by flexible crosslinks that are modeled as wormlike chains. Due to zero probability of filament intersection in three dimensions, our model networks are by construction prestressed in terms of initial tension in the crosslinks. We demonstrate how the linear elastic modulus can be related to the prestress in these networks. Under the assumption of affine deformations in the limit of infinite crosslink density, we show analytically that the nonlinear elastic regime in 1- and 2-dimensional networks is characterized by power-law scaling of the elastic modulus with the stress. In contrast, 3-dimensional networks show an exponential dependence of the modulus on stress. Independent of dimensionality, if the crosslink density is finite, we show that the only persistent scaling exponent is that of the single wormlike chain. We further show that there is no qualitative change in the stiffening behavior of filamentous networks even if the filaments are bending-compliant. Consequently, unlike suggested in prior work, the model system studied here cannot provide an explanation for the experimentally observed linear scaling of the modulus with the stress in filamentous networks.
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Affiliation(s)
- Knut M Heidemann
- Institute for Numerical and Applied Mathematics, Georg-August-Universität, Göttingen, Germany.
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28
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Abstract
Injuries in blood vessels are accompanied by disrupted endothelial cell layers. Missing or destroyed endothelial cells lead to rough, structured surfaces on the micrometer scale. The first cells to arrive at the site of injury and to cover the wound are platelets, which subsequently drive blood clot formation. Therefore, investigating the interactions of platelets with structured surfaces is essential for the understanding of blood clotting. Here, we study the effects of underlying topography on platelet spreading using microstructured model substrates with varying area fractions of protein coating. We thereby distinguish the effects of (physical) topography and of (biochemical) protein availability. By analyzing the cell area and morphology, we find that the extent of protrusion formation - but not the total spread area - is determined by the area fractions of coating. The extent of filopodia formation is influenced by the availability of binding sites and the reaction of cells to the substrate's topography. The cells react to the structured substrate by avoiding topographic holes at the cell periphery and thus adapting their outer shape. This finding leads us to the conclusion that both chemically blocked and fibrinogen-coated holes represent "energetic obstacles" to the cells. Thus, the shape of the cell is governed by the interplay between spreading to an optimized area and adaption to the substrate topography.
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Affiliation(s)
- Rabea Sandmann
- University of Göttingen, Institute for X-Ray Physics, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
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29
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Kaliman S, Jayachandran C, Rehfeldt F, Smith AS. Novel growth regime of MDCK II model tissues on soft substrates. Biophys J 2014; 106:L25-8. [PMID: 24703316 PMCID: PMC3976519 DOI: 10.1016/j.bpj.2013.12.056] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 11/25/2013] [Accepted: 12/11/2013] [Indexed: 12/13/2022] Open
Abstract
It is well established that MDCK II cells grow in circular colonies that densify until contact inhibition takes place. Here, we show that this behavior is only typical for colonies developing on hard substrates and report a new growth phase of MDCK II cells on soft gels. At the onset, the new phase is characterized by small, three-dimensional droplets of cells attached to the substrate. When the contact area between the agglomerate and the substrate becomes sufficiently large, a very dense monolayer nucleates in the center of the colony. This monolayer, surrounded by a belt of three-dimensionally packed cells, has a well-defined structure, independent of time and cluster size, as well as a density that is twice the steady-state density found on hard substrates. To release stress in such dense packing, extrusions of viable cells take place several days after seeding. The extruded cells create second-generation clusters, as evidenced by an archipelago of aggregates found in a vicinity of mother colonies, which points to a mechanically regulated migratory behavior.
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Affiliation(s)
- Sara Kaliman
- Institute for Theoretical Physics and Cluster of Excellence: Engineering of Advanced Materials, University Erlangen-Nürnberg, Germany
| | | | - Florian Rehfeldt
- 3rd Institute of Physics - Biophysics, Georg-August-University, Göttingen, Germany.
| | - Ana-Sunčana Smith
- Institute for Theoretical Physics and Cluster of Excellence: Engineering of Advanced Materials, University Erlangen-Nürnberg, Germany.
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30
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Swift J, Ivanovska IL, Buxboim A, Harada T, Dingal PCDP, Pinter J, Pajerowski JD, Spinler KR, Shin JW, Tewari M, Rehfeldt F, Speicher DW, Discher DE. Nuclear lamin-A scales with tissue stiffness and enhances matrix-directed differentiation. Science 2013; 341:1240104. [PMID: 23990565 DOI: 10.1126/science.1240104] [Citation(s) in RCA: 1276] [Impact Index Per Article: 116.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Tissues can be soft like fat, which bears little stress, or stiff like bone, which sustains high stress, but whether there is a systematic relationship between tissue mechanics and differentiation is unknown. Here, proteomics analyses revealed that levels of the nucleoskeletal protein lamin-A scaled with tissue elasticity, E, as did levels of collagens in the extracellular matrix that determine E. Stem cell differentiation into fat on soft matrix was enhanced by low lamin-A levels, whereas differentiation into bone on stiff matrix was enhanced by high lamin-A levels. Matrix stiffness directly influenced lamin-A protein levels, and, although lamin-A transcription was regulated by the vitamin A/retinoic acid (RA) pathway with broad roles in development, nuclear entry of RA receptors was modulated by lamin-A protein. Tissue stiffness and stress thus increase lamin-A levels, which stabilize the nucleus while also contributing to lineage determination.
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Affiliation(s)
- Joe Swift
- Molecular and Cell Biophysics Laboratory, University of Pennsylvania, Philadelphia, PA 19104, USA
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31
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Rehfeldt F, Potyrala M, Brown AE, Zemel A, Discher DE. Stem Cell Nucleus Morphology is Modulated by Matrix Mechanics via the Cytoskeleton. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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32
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Rehfeldt F, Brown AEX, Raab M, Cai S, Zajac AL, Zemel A, Discher DE. Hyaluronic acid matrices show matrix stiffness in 2D and 3D dictates cytoskeletal order and myosin-II phosphorylation within stem cells. Integr Biol (Camb) 2012; 4:422-30. [PMID: 22344328 DOI: 10.1039/c2ib00150k] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Physical features of microenvironments such as matrix elasticity E can clearly influence cell morphology and cell phenotype, but many differences between model matrices raise questions as to whether a standard biological scale for E exists, especially in 3D as well as in 2D. An E-series of two distinct types of hydrogels are ligand-functionalized here with non-fibrous collagen and used to elucidate wide-ranging cell and cytoskeletal responses to E in both 2D and 3D matrix geometries. Cross-linked hyaluronic acid (HA) based matrices as well as standard polyacrylamide (PA) hydrogels show that, within hours of initial plating, the adhesion, asymmetric shape, and cytoskeletal order within mesenchymal stem cells generally depend on E nonmonotonically over a broad range of physiologically relevant E. In particular, with overlays of a second matrix the stiffer of the upper or lower matrix dominates key cell responses to 3D: the cell invariably takes an elongated shape that couples to E in driving cytoplasmic stress fiber assembly. In contrast, embedding cells in homogeneous HA matrices constrains cells to spherically symmetric shapes in which E drives the assembly of a predominantly cortical cytoskeleton. Non-muscle myosin II generates the forces required for key cell responses and is a target of a phospho-Tyrosine signaling pathway that likely regulates contractile assemblies and also depends nonmonotonically on E. The results can be understood in part from a theory for stress fiber polarization that couples to matrix elasticity as well as cell shape and accurately predicts cytoskeletal order in 2D and 3D, regardless of polymer system.
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Affiliation(s)
- Florian Rehfeldt
- Biophysical Eng'g. Lab, University of Pennsylvania, Philadelphia, PA 19104, USA.
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33
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Abstract
The shape and differentiation of human mesenchymal stem cells is especially sensitive to the rigidity of their environment; the physical mechanisms involved are unknown. A theoretical model and experiments demonstrate here that the polarization/alignment of stress-fibers within stem cells is a non-monotonic function of matrix rigidity. We treat the cell as an active elastic inclusion in a surrounding matrix whose polarizability, unlike dead matter, depends on the feedback of cellular forces that develop in response to matrix stresses. The theory correctly predicts the monotonic increase of the cellular forces with the matrix rigidity and the alignment of stress-fibers parallel to the long axis of cells. We show that the anisotropy of this alignment depends non-monotonically on matrix rigidity and demonstrate it experimentally by quantifying the orientational distribution of stress-fibers in stem cells. These findings offer a first physical insight for the dependence of stem cell differentiation on tissue elasticity.
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Affiliation(s)
- A Zemel
- Institute of Dental Sciences, Faculty of Dental Medicine, and the Fritz Haber Center for Molecular Dynamics, the Hebrew University-Hadassah Medical Center, Jerusalem, 91120, Israel
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34
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Abstract
The active regulation of cellular forces during cell adhesion plays an important role in the determination of cell size, shape and internal structure. While on flat, homogeneous and isotropic substrates some cells spread isotropically, others spread anisotropically and assume elongated structures. In addition, in their native environment as well as in vitro experiments, the cell shape and spreading asymmetry can be modulated by the local distribution of adhesive molecules and topography of the environment. We present a simple elastic model, and experiments on stem cells to explain the variation of cell size with the matrix rigidity. In addition, we predict the experimental consequences of two mechanisms of acto-myosin polarization and focus here on the effect of the cell spreading asymmetry on the regulation of the stress-fiber alignment in the cytoskeleton. We show that when cell spreading is sufficiently asymmetric the alignment of acto-myosin forces in the cell increases monotonically with the matrix rigidity; however, in general this alignment is non-monotonic as shown previously. These results highlight the importance of the symmetry characteristics of cell spreading in the regulation of cytoskeleton structure and suggest a mechanism by which different cell types may acquire different morphologies and internal structures in different mechanical environments.
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Affiliation(s)
- A Zemel
- Institute of Dental Sciences, Faculty of Dental Medicine, Hebrew University-Hadassah Medical Center, Jerusalem, Israel
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35
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Rehfeldt F, Zajac A, Brown A, Buxboim A, Discher DE. Matrix Elasticity and Nuclear Physics. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.2316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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36
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Schneck E, Oliveira RG, Rehfeldt F, Demé B, Brandenburg K, Seydel U, Tanaka M. Mechanical properties of interacting lipopolysaccharide membranes from bacteria mutants studied by specular and off-specular neutron scattering. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 80:041929. [PMID: 19905364 DOI: 10.1103/physreve.80.041929] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Revised: 09/03/2009] [Indexed: 05/28/2023]
Abstract
Specular and off-specular neutron scattering are used to study the influence of molecular chemistry (mutation) on the intermembrane interactions and mechanical properties of the outer membrane of Gram-negative bacteria consisting of lipopolysaccharides (LPSs). For this purpose, solid-supported multilayers of mutant LPS membranes are deposited on silicon wafers and hydrated either at defined humidity or in bulk buffers. The planar sample geometry allows to identify out-of-plane and in-plane scattering vector components. The measured two-dimensional reciprocal space maps are simulated with membrane displacement correlation functions determined by two mechanical parameters (vertical compression modulus and bending rigidity) and an effective cutoff radius for the membrane fluctuation wavelength. Experiments at controlled humidity enable one to examine the influence of the disjoining pressure on the saccharide-mediated intermembrane interactions, while experiments in bulk buffers (i.e., in the absence of an external osmotic stress) reveal the effect of divalent cations on LPS membranes, highlighting the role of divalent cations in the survival mechanism of bacteria in the presence of antimicrobial molecules.
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Affiliation(s)
- Emanuel Schneck
- Biophysical Chemistry II, Institute of Physical Chemistry and BIOQUANT, University of Heidelberg, D69120 Heidelberg, Germany
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37
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Schneck E, Rehfeldt F, Oliveira RG, Gege C, Demé B, Tanaka M. Modulation of intermembrane interaction and bending rigidity of biomembrane models via carbohydrates investigated by specular and off-specular neutron scattering. Phys Rev E Stat Nonlin Soft Matter Phys 2008; 78:061924. [PMID: 19256885 DOI: 10.1103/physreve.78.061924] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2008] [Revised: 09/24/2008] [Indexed: 05/27/2023]
Abstract
We designed artificial models of biological membranes by deposition of synthetic glycolipid membrane multilayers on planar silicon substrates. In contrast to commonly used phospholipid membranes, this offers the unique possibility to study the influence of membrane-bound saccharide chains (cell glycocalix) on the membrane mechanics. Taking advantage of the planar sample geometry, we carried out specular and off-specular neutron scattering experiments to identify out-of-plane and in-plane scattering vector components. By considering the effects of finite sample sizes, we were able to simulate the measured two-dimensional reciprocal space maps within the framework of smectic liquid-crystal theory. The results obtained both at controlled humidity and in bulk water clearly indicate that a subtle change in the molecular chemistry of the saccharides strongly influences intermembrane interactions and membrane bending rigidities.
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Affiliation(s)
- Emanuel Schneck
- Biophysical Chemistry II, Institute of Physical Chemistry and BIOQUANT, University of Heidelberg, D69120 Heidelberg, Germany
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38
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Rehfeldt F, Engler AJ, Eckhardt A, Ahmed F, Discher DE. Cell responses to the mechanochemical microenvironment--implications for regenerative medicine and drug delivery. Adv Drug Deliv Rev 2007; 59:1329-39. [PMID: 17900747 PMCID: PMC4124491 DOI: 10.1016/j.addr.2007.08.007] [Citation(s) in RCA: 259] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2007] [Accepted: 08/01/2007] [Indexed: 02/05/2023]
Abstract
Soft-tissue cells are surprisingly sensitive to the elasticity of their microenvironment, suggesting that traditional culture plastic and glass are less relevant to tissue regeneration and chemotherapeutics than might be achieved. Cells grown on gels that mimic the elasticity of tissue reveal a significant influence of matrix elasticity on adhesion, cytoskeletal organization, and even the differentiation of human adult derived stem cells. Cellular forces and feedback are keys to how cells feel their mechanical microenvironment, but detailed molecular mechanisms are still being elucidated. This review summarizes our initial findings for multipotent stem cells and also the elasticity-coupled effects of drugs on cancer cells and smooth muscle cells. The drugs include the contractility inhibitor blebbistatin, the proliferation inhibitor mitomycin C, an apoptotis-inducing antibody against CD47, and the translation inhibitor cycloheximide. The differential effects not only lend insight into mechano-sensing of the substrate by cells, but also have important implications for regeneration and molecular therapies.
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Affiliation(s)
- Florian Rehfeldt
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia PA 19104, USA
| | - Adam J. Engler
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia PA 19104, USA
| | - Adam Eckhardt
- Institute of Physiology, Czech Academy of Science, Prague, Czech Republic
| | - Fariyal Ahmed
- Department of Bioengineering, University of Pennsylvania, Philadelphia PA 19104, USA
| | - Dennis E. Discher
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia PA 19104, USA
- Department of Bioengineering, University of Pennsylvania, Philadelphia PA 19104, USA
- Graduate Group of Physics & Astronomy, University of Pennsylvania, Philadelphia PA 19104, USA
- Corresponding author. Molecular & Cell Biophysics and NanoBio-Polymers Lab, University of Pennsylvania, Philadelphia PA 19104, USA. Tel.: +1 215 898 4809
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39
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Abstract
It is increasingly appreciated that the mechanical properties of the microenvironment around cells exerts a significant influence on cell behavior, but careful consideration of what is the physiologically relevant elasticity for specific cell types is required to produce results that meaningfully recapitulate in vivo development. Here we outline methodologies for excising and characterizing the effective microelasticity of tissues; but first we describe and validate an atomic force microscopy (AFM) method as applied to two comparatively simple hydrogel systems. With tissues and gels sufficiently understood, the latter can be appropriately tuned to mimic the desired tissue microenvironment for a given cell type. The approach is briefly illustrated with lineage commitment of stem cells due to matrix elasticity.
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Affiliation(s)
- Adam J Engler
- Biophysical Engineering and Polymers Laboratory, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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40
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Rehfeldt F, Steitz R, Armes SP, von Klitzing R, Gast AP, Tanaka M. Reversible Activation of Diblock Copolymer Monolayers at the Interface by pH Modulation, 1: Lateral Chain Density and Conformation. J Phys Chem B 2006; 110:9171-6. [PMID: 16671730 DOI: 10.1021/jp054532j] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This study focuses on the design of chemically regulated surfaces that allow for reversible control of the interactions between biological matter (cells and proteins) and planar substrates. As a tunable interlayer, we use a monolayer of a near-monodisperse poly[2-(dimethylamino)ethyl methacrylate-block-methyl methacrylate] (PDMAEMA-PMMA) diblock copolymer. Owing to the relatively large fraction (50%) of the hydrophobic PMMA block, this copolymer forms a stable Langmuir monolayer at the air/water interface. Both in situ and ex situ film balance experiments suggest that the hydrophilic PDMAEMA block adsorbs to the air/water interface in its uncharged state (pH 8.5), but stretches into the subphase in its charged state (pH 5.5). Optimization of the preparation protocols enables us to fabricate stable, homogeneous diblock copolymer films on hydrophobized substrates via Langmuir-Schaefer transfer at well-defined lateral chain densities. Ellipsometry and X-ray reflectivity studies of the transferred films confirm that the film thickness can be systematically regulated by the lateral chain densities. The transferred copolymer films remain stable in water for about a week, suggesting that they are promising materials for the creation of pH-controlled solid substrates for the support of biological matter such as proteins and cells.
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Affiliation(s)
- Florian Rehfeldt
- Physik Department E22, Technische Universität München, James-Franck-Str., D-85748 Garching, Germany.
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Rehfeldt F, Steitz R, Armes SP, von Klitzing R, Gast AP, Tanaka M. Reversible Activation of Diblock Copolymer Monolayers at the Interface by pH Modulation, 2: Membrane Interactions at the Solid/Liquid Interface. J Phys Chem B 2006; 110:9177-82. [PMID: 16671731 DOI: 10.1021/jp054533b] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A monolayer of the pH-responsive poly[2-(dimethylamino)ethyl methacrylate-block-methyl methacrylate] diblock copolymer [PDMAEMA-PMMA] was transferred from the air/water interface to a silicon substrate for evaluation as a tunable interlayer between biological material and solid substrates. Specular neutron reflectivity experiments revealed that the weak polyelectrolyte PDMAEMA chains at the solid/liquid interface can be reversibly activated by pH modulation. The thickness, scattering length density, and surface roughness of the polymer film can be systematically controlled by pH titration. As a simple model of plasma membranes, a lipid bilayer was deposited onto the polymer film. The membrane-substrate interaction was characterized by neutron reflectivity experiments, demonstrating that the membrane-substrate distance could be reversibly regulated by pH titration. These results confirm the potential of stimuli-responsive polymers for precise control of cell-surface interactions.
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Affiliation(s)
- Florian Rehfeldt
- Physik Department E22, Technische Universität München, James-Franck-Str., D-85748 Garching, Germany.
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Tanaka M, Rehfeldt F, Schneider MF, Gege C, Schmidt RR, Funari SS. Oligomer-to-polymer transition in short ethylene glycol chains connected to mobile hydrophobic anchors. Chemphyschem 2005; 6:101-9. [PMID: 15688653 DOI: 10.1002/cphc.200400336] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We studied the structure of short ethylene glycol (EG) chains with N repeating units (EGN, N = 3, 6, 9, 12, and 15) connected to hydrophobic dihexadecyl chains by means of a combination of differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SAXS/WAXS). These synthetic amphiphiles dispersed in water form planar lamellar stacks and hexagonal cylinders confining the EG chains to restricted geometries. Owing to the self-assembly of the anchoring points, the lateral density of EG chains in planar lamella can be quantitatively controlled. Furthermore, the chain-melting phase transition of the anchors enables us to "switch" the intermolecular distance reversibly. SAXS/WAXS results suggest that the shorter EG chains (N = 3, 6, and 9) assume a helical conformation in stacks of planar lamella. When the EG chains are further elongated (N = 12 and 15), the lamellar periodicities cannot be explained by a linear extrapolation of shorter oligomers, but can be interpreted well as polymer brushes following the scaling theorem. Such rich phase behaviors of EGN molecules can be used as a simple model of oligo/poly-saccharide chains on cell surfaces, which act not only as flexible repellers between neighboring cells but also as stable spacers for functional ligands.
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Affiliation(s)
- Motomu Tanaka
- Lehrstuhl für Biophysik, Technische Universität München, 85748 Garching, Germany.
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Affiliation(s)
- John E. Wong
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Strasse des 17. Juni 112, D-10623 Berlin, Lehrstuhl für Biophysik, Technische Universität München, James-Franck-Strasse, D-85748 Garching, and Max-Planck Institut für Kolloid- und Grenzflächenforschung, Am Mühlenberg 1, D-14424 Potsdam
| | - Florian Rehfeldt
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Strasse des 17. Juni 112, D-10623 Berlin, Lehrstuhl für Biophysik, Technische Universität München, James-Franck-Strasse, D-85748 Garching, and Max-Planck Institut für Kolloid- und Grenzflächenforschung, Am Mühlenberg 1, D-14424 Potsdam
| | - Peter Hänni
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Strasse des 17. Juni 112, D-10623 Berlin, Lehrstuhl für Biophysik, Technische Universität München, James-Franck-Strasse, D-85748 Garching, and Max-Planck Institut für Kolloid- und Grenzflächenforschung, Am Mühlenberg 1, D-14424 Potsdam
| | - Motomu Tanaka
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Strasse des 17. Juni 112, D-10623 Berlin, Lehrstuhl für Biophysik, Technische Universität München, James-Franck-Strasse, D-85748 Garching, and Max-Planck Institut für Kolloid- und Grenzflächenforschung, Am Mühlenberg 1, D-14424 Potsdam
| | - Regine v. Klitzing
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Strasse des 17. Juni 112, D-10623 Berlin, Lehrstuhl für Biophysik, Technische Universität München, James-Franck-Strasse, D-85748 Garching, and Max-Planck Institut für Kolloid- und Grenzflächenforschung, Am Mühlenberg 1, D-14424 Potsdam
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Abstract
We establish two methods to deposit native biomembranes (human erythrocyte membranes and sarcoplasmic reticulum membranes) selectively onto biocompatible microtemplates. The first method utilizes UV photolithography to micropattern the regenerated cellulose, while the second uses the "stamping" of protein barriers onto homogeneous cellulose supports. The relatively simple methods established here allow for the position selective spreading of three-dimensional native cells into two-dimensional films, retaining the orientation and lateral density of transmembrane proteins in their native state.
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Affiliation(s)
- Motomu Tanaka
- Lehrstuhl für Biophysik E22, Technische Universität München, James-Franck-Strasse 1, D-85748 Garching, Germany.
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Niederfellner J, Lenoir D, Matuschek G, Rehfeldt F, Utschick H, Brüggemann R. Description of Vapour Pressures of Polycyclic Aromatic Compounds by Graph Theoretical Indices. ACTA ACUST UNITED AC 1997. [DOI: 10.1002/qsar.19970160107] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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