Nanoscale sensing and imaging of mechanical properties of live cells (Conference Presentation)

During recent years the atomic force microscopy (AFM) has evolved into an extremely useful instrument in life sciences. Particularly the option of this novel technique to operate under quasi physiological conditions and in real time has initiated a broad spectrum of new experiments. As a result, structural and micro-mechanical properties of supramolecular arrangements like molecular films and protein complexes were elucidated. Dynamic processes in live cells were recorded at unparalleled resolution and molecular interactions were investigated. Selected examples of such aspects will be the topic of this lecture.The AFM has improved drastically the understanding of the molecular structure of Langmuir-Blodgett films. LB films have in turn evolved into standards for the improvement of the understanding of the fundamental imaging mechanisms because of several reasons: they may be formed from a broad variety of substances and their molecular packing can be varied and controlled to a large degree at the air water interface prior to transfer, allowing the intelligent design of certain surface properties like roughness and charge density or micro-mechanical properties.

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Phase imaging of mechanical properties of live cells (Conference Presentation)

Quantitative Phase Imaging III ◽

10.1117/12.2255903 ◽

2017 ◽

Author(s):

Adam Wax

Keyword(s):

Mechanical Properties ◽

Live Cells ◽

Phase Imaging

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COMBINED ATOMIC FORCE AND FLUORESCENCE MICROSCOPIES TO MEASURE SUBCELLULAR MECHANICAL PROPERTIES OF LIVE CELLS

Journal of Mechanics in Medicine and Biology ◽

10.1142/s0219519413500577 ◽

2013 ◽

Vol 13 (04) ◽

pp. 1350057 ◽

Cited By ~ 3

Author(s):

CHENG-TAO CHANG ◽

CHOU-CHING K. LIN ◽

MING-SHAUNG JU

Keyword(s):

Mechanical Properties ◽

Elastic Modulus ◽

Elastic Properties ◽

Previous Method ◽

Live Cell ◽

Live Cells ◽

Cellular Functions ◽

Atomic Force ◽

Force Volume ◽

The Relationship

Atomic force microscopy (AFM) has been widely applied to study cellular functions;however, the relationship between cellular elasticity and ultrastructure density of a live cell remains to be discovered. The objective of this study was thus to extend our previous method of integrating AFM and immunofluorescence imaging to measure the ultrastructure distribution-related local mechanical properties of live cells. First, the morphology of a live cell was obtained by AFM. Second, the indentation sites were selected and flexible force volume indentation was performed. Third, the immunofluorescence image of the cell was obtained. The last was the mapping of the indentation site to the immunofluorescence image and obtaining the relationship between the local elastic properties and cytoskeleton density. The results on differentiated rat Schwann cells (RSCs) showed that the elastic modulus of stress fibers is higher than those of the nucleus and cytosol. The local elastic modulus of the live RSCs is correlated to the actin density, and the stress fiber that behaves like a pretension beam can give RSCs enough strength to envelop axons during myelination. In particular, the elastic properties of the live RSCs were twofold lower than those of the fixed. The results demonstrated the integrated method's applicability for a live cell.

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Phase separation enables heterochromatin domains to do mechanical work

10.1101/2020.07.02.184127 ◽

2020 ◽

Author(s):

Jessica F. Williams ◽

Ivan V. Surovtsev ◽

Sarah M. Schreiner ◽

Hang Nguyen ◽

Yan Hu ◽

...

Keyword(s):

Mechanical Properties ◽

Phase Separation ◽

Mechanical Work ◽

Live Cells ◽

Fluctuation Analysis ◽

Cellular Organization ◽

Heterochromatin Protein ◽

Liquid Liquid Phase Separation

SummaryLiquid-liquid phase separation (LLPS) has emerged as a major driver of cellular organization. However, it remains unexplored whether the mechanical properties of LLPS domains are functionally important. The heterochromatin protein HP1-α (and the orthologous Swi6 in S. pombe) is capable of LLPS in vitro and promotes formation of LLPS heterochromatin domains in vivo. Here, we demonstrate that LLPS of Swi6 contributes to the emergent mechanical properties of nuclei. Using nuclear fluctuation analysis in live cells and force spectroscopy of isolated nuclei, we find that disrupting histone H3K9 methylation or depleting Swi6 compromises nuclear stiffness, while heterochromatin spreading through loss of the H3K9 demethylase, Epe1, increases nuclear stiffness. Leveraging a separation-of-function allele, we demonstrate that phase separation of Swi6—but not its histone binding or dimerization—is essential for Swi6’s mechanical role. These findings demonstrate that altering chromatin state has mechanical consequences and highlights that phase-separated domains can do mechanical work.

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Construction of Three-Dimensional Scaffold for Tissue Engineered Heart Valves

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.873.627 ◽

2013 ◽

Vol 873 ◽

pp. 627-634 ◽

Cited By ~ 1

Author(s):

Bin En Nie ◽

Shi Dong Hu ◽

Jian Liang Zhou

Keyword(s):

Mechanical Properties ◽

Heart Valve ◽

Heart Valves ◽

Three Dimensional ◽

Biological Properties ◽

Live Cells ◽

Tissue Compatibility ◽

Scaffold Materials ◽

Nanocomposite Scaffold ◽

Tissue Engineered Heart Valves

Tissue engineered heart valve (TEHV) is a valve replacement of scaffold materials on which live cells grow. Theoretically, TEHV has good tissue compatibility, self-repair potential and life-long durability, which serves as the optimal replacement for a heart valve. As a result of the specific position and function of a specific heart valve, significantly high requirements of mechanical and biological properties are necessary for optimal function. A substantial number of studies suggested that the TEHV available at present has insufficient mechanical properties and lacks relevant anti-calcification function, both of which prevent the successful application of TEHV into clinical practice. A desirable valvular scaffold, which mimics the three-dimensional ultrastructures of extracellular matrix (ECM) in the heart valve, should possess the ECM bioactivity, favorable tissue compatibility and suitable mechanical properties. However, no such valve scaffold is currently available. Hence, clinical efforts should be made to remodel the scaffold materials, allowing for utilizing its functionalization. Here, we reviewed the scaffold materials previously used in TEHV, e.g. decellularized scaffold, polymer-based scaffold, nanoscaffold and nanocomposite scaffold and scaffold material modification.

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Phase Transformations in Ti-7w/oMo-3w/oMe Alloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052584 ◽

1974 ◽

Vol 32 ◽

pp. 514-515

Author(s):

S. Fujishiro

Keyword(s):

Electron Microscopy ◽

Mechanical Properties ◽

Transmission Electron Microscopy ◽

Tensile Strength ◽

Mechanical Processing ◽

Ray Method ◽

X Ray ◽

Transmission Electron ◽

Water Quench ◽

Alpha Beta

The mechanical properties of three titanium alloys (Ti-7Mo-3Al, Ti-7Mo- 3Cu and Ti-7Mo-3Ta) were evaluated as function of: 1) Solutionizing in the beta field and aging, 2) Thermal Mechanical Processing in the beta field and aging, 3) Solutionizing in the alpha + beta field and aging. The samples were isothermally aged in the temperature range 300° to 700*C for 4 to 24 hours, followed by a water quench. Transmission electron microscopy and X-ray method were used to identify the phase formed. All three alloys solutionized at 1050°C (beta field) transformed to martensitic alpha (alpha prime) upon being water quenched. Despite this heavily strained alpha prime, which is characterized by microtwins the tensile strength of the as-quenched alloys is relatively low and the elongation is as high as 30%.

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Effects of cooling rate on the mechanical properties of dual phase treated vanadium steels

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100074896 ◽

1983 ◽

Vol 41 ◽

pp. 220-221

Author(s):

L.J. Chen ◽

H.C. Cheng ◽

J.R. Gong ◽

J.G. Yang

Keyword(s):

Mechanical Properties ◽

Cooling Rate ◽

Automobile Industry ◽

High Strength ◽

Weight Percent ◽

Low Alloy Steels ◽

Dual Phase ◽

Resource Requirement ◽

Alloy Steels ◽

Potential Weight

For fuel savings as well as energy and resource requirement, high strength low alloy steels (HSLA) are of particular interest to automobile industry because of the potential weight reduction which can be achieved by using thinner section of these steels to carry the same load and thus to improve the fuel mileage. Dual phase treatment has been utilized to obtain superior strength and ductility combinations compared to the HSLA of identical composition. Recently, cooling rate following heat treatment was found to be important to the tensile properties of the dual phase steels. In this paper, we report the results of the investigation of cooling rate on the microstructures and mechanical properties of several vanadium HSLA steels.The steels with composition (in weight percent) listed below were supplied by China Steel Corporation: 1. low V steel (0.11C, 0.65Si, 1.63Mn, 0.015P, 0.008S, 0.084Aℓ, 0.004V), 2. 0.059V steel (0.13C, 0.62S1, 1.59Mn, 0.012P, 0.008S, 0.065Aℓ, 0.059V), 3. 0.10V steel (0.11C, 0.58Si, 1.58Mn, 0.017P, 0.008S, 0.068Aℓ, 0.10V).

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Lattice Imaging of Grain Boundaries in Ceramics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078171 ◽

1977 ◽

Vol 35 ◽

pp. 114-115

Author(s):

D. R. Clarke ◽

G. Thomas

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

Silicon Nitride ◽

Grain Boundaries ◽

High Temperature Strength ◽

Current Interest ◽

Lattice Imaging ◽

Special Significance ◽

Structural Applications ◽

Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

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