Tag Archives: force curves

Elastic shell theory for plant cell wall stiffness reveals contributions of cell wall elasticity and turgor pressure in AFM measurement

The stiffness of a plant cell in response to an applied force is determined not only by the elasticity of the cell wall but also by turgor pressure and cell geometry, which affect the tension of the cell wall. Although stiffness has been investigated using atomic force microscopy (AFM) and Young’s modulus of the cell wall has occasionally been estimated using the contact-stress theory (Hertz theory), the existence of tension has made the study of stiffness more complex. *

An alternative model is a contact model based on elastic shell theory, in which the cell wall is assumed to be a thin, curved surface pushed by turgor pressure. This theory enables one to infer turgor pressure from the apparent stiffness in some cases. In the unified formula from the elastic shell theory, AFM indentation is described as the contributions of cell wall elasticity and turgor pressure, while the estimation of elasticity and pressure remains ambiguous. *

In the article “Elastic shell theory for plant cell wall stiffness reveals contributions of cell wall elasticity and turgor pressure in AFM measurement” Satoru Tsugawa, Yuki Yamasaki, Shota Horiguchi, Tianhao Zhang, Takara Muto, Yosuke Nakaso, Kenshiro Ito, Ryu Takebayashi, Kazunori Okano, Eri Akita, Ryohei Yasukuni, Taku Demura, Tetsuro Mimura, Ken’ichi Kawaguchi and Yoichiroh Hosokawa describe how they used finite element method simulations to verify the formula of the elastic shell theory for onion (Allium cepa) cells and further optimized the formula to analyze the apparent stiffness observed from the AFM measurement based on the elastic shell theory.*

The authors applied the formula and simulations to successfully quantify the turgor pressure and elasticity of a cell in the plane direction using the cell curvature and apparent stiffness measured by atomic force microscopy. They conclude that tension resulting from turgor pressure regulates cell stiffness, which can be modified by a slight adjustment of turgor pressure in the order of 0.1 MPa. This theoretical analysis reveals a path for understanding forces inherent in plant cells. *

NANOSENSORS™ sphere AFM probes SD-Sphere-NCH-S from the NANOSENSORS™ Special Developments List were used for the force-indentation curve measurements described in the article. NANOSENSORS™ tipless AFM cantilevers of the TL-NCH type were used to evaluate the tip radius dependence. *

Fig-3-S-Tsugawa-et-al-2022-Elastic-shell-theory-for-plant-cell-wall-stiffness-reveals-contributions-of-cell-wall-elasticity-and-turgor-pressure-in-AFM-measurement NANOSENSORS Sphere-AFM probes SD-Sphere-NCH-S from the NANOSENSORS™ Special Developments List were used for the force-indentation curve measurements with atomic force microscopy
Figure 3 from “Elastic shell theory for plant cell wall stiffness reveals contributions of cell wall elasticity and turgor pressure in AFM measurement” by Satoru Tsugawa et al.:
AFM measurement of an onion epidermal cell with laser perforation. (A) Photographs of the cell measured before (left) and after (right) perforation. Yellow arrow indicates the perforation point. Cell lengths along long- and short- axes are denoted by La and Lb, respectively. Bars, 50 µm. (B) Topographic images before (left) and after (right) perforation. Measurement area corresponds to the dashed box area in (A). Lower images are three-dimensional images of upper images. (C) Enlarged image of the perforation point. (D) Cross-sectional graph of the cell wall surface before (red line) and after (blue line) perforation, corresponding to the height of dashed lines in upper-left and -right images in (B), respectively. Bulge height of the cell surface is denoted by w. Dashed lines are curves for curvature calculated from Lb and w. (E) Quantities determined from AFM measurement. Mean curvature of the cell wall surface κM is calculated from La, Lb, and w. (F) Force–indentation curves of the cell wall before (red dots) and after (blue dots) perforation. Dashed lines are fitting curves by the Hertz model and solid lines are fitting lines by the shell model. (G) Apparent stiffness kas as a function of force F applied to the cell wall before (red dots) and after (blue dots) perforation. kas is estimated by linear least squares fitting of the force-indentation curve in the vicinity of the F, as shown in (F). Bars on dots represent root mean squared error. Solid lines are exponential plateau curves: kas = 35 × {1 − exp(− F/7)} (red line); kas = 10 × {1 − exp(− F/1.28)} (blue line).
Abstract
The stiffness of a plant cell in response to an applied force is determined not only by the elasticity of the cell wall but also by turgor pressure and cell geometry, which affect the tension of the cell wall. Although stiffness has been investigated using atomic force microscopy (AFM) and Young’s modulus of the cell wall has occasionally been estimated using the contact-stress theory (Hertz theory), the existence of tension has made the study of stiffness more complex. Elastic shell theory has been proposed as an alternative method; however, the estimation of elasticity remains ambiguous. Here, we used finite element method simulations to verify the formula of the elastic shell theory for onion (Allium cepa) cells. We applied the formula and simulations to successfully quantify the turgor pressure and elasticity of a cell in the plane direction using the cell curvature and apparent stiffness measured by AFM. We conclude that tension resulting from turgor pressure regulates cell stiffness, which can be modified by a slight adjustment of turgor pressure in the order of 0.1 MPa. This theoretical analysis reveals a path for understanding forces inherent in plant cells.

*Satoru Tsugawa, Yuki Yamasaki, Shota Horiguchi, Tianhao Zhang, Takara Muto, Yosuke Nakaso, Kenshiro Ito, Ryu Takebayashi, Kazunori Okano, Eri Akita, Ryohei Yasukuni, Taku Demura, Tetsuro Mimura, Ken’ichi Kawaguchi and Yoichiroh Hosokawa
Elastic shell theory for plant cell wall stiffness reveals contributions of cell wall elasticity and turgor pressure in AFM measurement
Nature Scientific Reports volume 12, Article number: 13044 (2022)
DOI: https://doi.org/10.1038/s41598-022-16880-2

Please follow this external link to read the full article: https://rdcu.be/cSWFR

Open Access: The article “Elastic shell theory for plant cell wall stiffness reveals contributions of cell wall elasticity and turgor pressure in AFM measurement” by Satoru Tsugawa, Yuki Yamasaki, Shota Horiguchi, Tianhao Zhang, Takara Muto, Yosuke Nakaso, Kenshiro Ito, Ryu Takebayashi, Kazunori Okano, Eri Akita, Ryohei Yasukuni, Taku Demura, Tetsuro Mimura, Ken’ichi Kawaguchi and Yoichiroh Hosokawa is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Supercritical carbon dioxide decellularization of plant material to generate 3D biocompatible scaffolds

Biocompatible scaffolds that can be repopulated with human cells have many uses such serving as replacement organs and tissues. Therefore there is an increasing interest in plant-based biomaterials for tissue engineering.*

As the above mentioned scaffolds should mimic the in vivo tissue environment closely they need to provide a fitting structural and biomechanical support to the cells while at the same time promoting cell behaviour and tissue development. *

Currently the standard method to prepare plant tissue to serve as a biocompatible scaffold is to decellularize it with serial chemical treatment.*

In their article “Supercritical carbon dioxide decellularization of plant material to generate 3D biocompatible scaffolds” Ashlee F. Harris, Jerome Lacombe, Sumedha Liyanage, Margaret Y. Han, Emily Wallace, Sophia Karsunky, Noureddine Abidi and Frederic Zenhausern explore another method to produce biocompatible scaffolds.*

They use supercritical carbon dioxide (scCO2) together with 2% peracetic acid to decellularize plant material.*

Their subsequent investigations show that the process of decellularization, scaffold structure preservation and recellularization with human cells is less time consuming than with the standard chemical method.

In a further step the authors of the article describe how they use various scientific methods to evaluate the scaffolds they decellularized by the described scCO2 method.*

Ashlee F. Harris et al. use Atomic Force Microscopy (AFM) in order to find out if the scCO2 treatment had an impact on the mechanical properties of the scaffolds produced with this method.*

With AFM topography measurements they are able to establish that structures such as plant vasculature were preserved.*

The following determination of the Young’s Modulus calculated from multiple force curves of a homogeneous surface section of the produced scaffold shows it to be slightly lower than the one from a chemically decellularized scaffold.*

NANOSENSORS™ uniqprobe qp-BioAC AFM probes ( CB3 nominal values: 80 μm length, 30 μm mean width, 400 nm thickness, force constant 0.06 N/m, resonance frequency 30 kHz) were used for the scaffold measurements with Atomic Force Microscopy.

Figure 3 from “Supercritical carbon dioxide decellularization of plant material to generate 3D biocompatible scaffolds AFM imaging and spectrometry measurement” by Ashlee F. Harris et al.: 
They used AFM surface topography measurements to confirm that the structures such as plant vasculature were preserved after the scSO2 process and used  AFM force curves to calculate the  Young’s Modulus (YM) of the scCO2 decellularized scaffold. NANOSENSORS uniqprobe qp-BioAC AFM probes were used for the described AFM measurments. 
(a) Representative false colored three-dimensional surface mapping images and (b) Young’s modulus of scCO2 and chemically decellularized scaffolds (data as mean ± SEM; n = 5).
Figure 3 from “Supercritical carbon dioxide decellularization of plant material to generate 3D biocompatible scaffolds AFM imaging and spectrometry measurement” by Ashlee F. Harris et al.: (a) Representative false colored three-dimensional surface mapping images and (b) Young’s modulus of scCO2 and chemically decellularized scaffolds (data as mean ± SEM; n = 5).

While the scCo2 method promises to be a faster way to decellularize plant material and produce sterile and biocompatible scaffolds further research will be necessary to determine whether the differences the authors detected between the scaffolds produced with the scCO2 approach and the scaffolds produced with the chemical approach have a major influence on how repopulated cells behave in the achieved scaffolds.*

*Ashlee F. Harris, Jerome Lacombe, Sumedha Liyanage, Margaret Y. Han, Emily Wallace, Sophia Karsunky, Noureddine Abidi and Frederic Zenhausern
Supercritical carbon dioxide decellularization of plant material to generate 3D biocompatible scaffolds
Nature Scientific Reports 11, 3643 (2021)
DOI: https://doi.org/10.1038/s41598-021-83250-9

Please follow this external link to read the full article: https://rdcu.be/cAqW3

Open Access The article “Supercritical carbon dioxide decellularization of plant material to generate 3D biocompatible scaffolds” by Ashlee F. Harris, Jerome Lacombe, Sumedha Liyanage, Margaret Y. Han, Emily Wallace, Sophia Karsunky, Noureddine Abidi and Frederic Zenhausern is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Nonlinear Biomechanical Characteristics of Deep Deformation of Native RBC Membranes in Normal State and under Modifier Action

The mechanical properties and structural organization of membranes determine the functional state of red blood cells (RBCs). Deformability is one of the key physiological and biophysical indicators of RBC. Changes of the mechanical characteristics of cell membranes can lead to a decrease in the rate of capillary blood flow and to development of stagnant phenomena in the microcirculation, and it can also reduce the amount of oxygen delivered to the tissues.*

In the article “Nonlinear Biomechanical Characteristics of Deep Deformation of Native RBC Membranes in Normal State and under Modifier Action” Elena Kozlova, Aleksandr Chernysh, Ekaterina Manchenko, Viktoria Sergunova and Viktor Moroz describe how they evaluated the ability of membranes of native human red blood cells (RBCs) to bend into the cell to a depth comparable in size with physiological deformations using the methods of atomic force microscopy ( AFM ) and atomic force spectroscopy ( AFS ).*

As a true estimation of the elastic properties of RBC membranes can be obtained only by measurement of native cell properties the aim of the experiments was to study nonlinear mechanical characteristics of deep deformation of native RBC membranes in normal state and under the action of modifiers, in vitro to make sure that the result would be the closest to the characteristics of a living biological object.*

NANOSENSORS™ rounded AFM tips of the type SD-R150-T3L450B with a typical tip radius of 150 nm from the NANOSENSORS Special Developments List were used to measure the deformation of the RBC membrane by atomic force spectroscopy ( AFS ).*


Figure 5.2. (c) from “Nonlinear Biomechanical Characteristics of Deep Deformation of Native RBC Membranes in Normal State and under Modifier Action “ by Elena Kozlova et al.:
 Bending of membranes under the action of force F for stiff (1) and soft (2) membranes; F is the force acting on the membrane from the probe, Z is the vertical displacement of the piezoscanner, h is the depth of the membrane bending into RBC, PBS is the phosphate buffer solution, and rd is the bending radius of the membrane.

*Elena Kozlova, Aleksandr Chernysh, Ekaterina Manchenko, Viktoria Sergunova, and Viktor Moroz
Nonlinear Biomechanical Characteristics of Deep Deformation of Native RBC Membranes in Normal State and under Modifier Action
Scanning, Volume 2018, Article ID 1810585, 13 pages
Doi: https://doi.org/10.1155/2018/1810585

Please follow this external link to read the full article: https://www.hindawi.com/journals/scanning/2018/1810585/

Open Access The article « Nonlinear Biomechanical Characteristics of Deep Deformation of Native RBC Membranes in Normal State and under Modifier Action ” by Elena Kozlova, Aleksandr Chernysh, Ekaterina Manchenko, Viktoria Sergunova, and Viktor Moroz is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.