scholarly journals The effect of cortical elasticity and active tension on cell adhesion mechanics

2018 ◽  
Author(s):  
B. Smeets ◽  
M. Cuvelier ◽  
J. Pešek ◽  
H. Ramon
Keyword(s):  
Surface Tension ◽  
Elastic Shell ◽  
Active Surface ◽  
Contact Radius ◽  
Active Tension ◽  
Variation Of Parameters ◽  
Biophysical Journal ◽  
A Cell ◽  
Adhesion Mechanics ◽  
Separation Force

AbstractWe consider a cell as a filled, elastic shell with an active surface tension and non-specific adhesion. We perform numerical simulations of this model in order to study the mechanics of cell-cell separation. By variation of parameters, we are able to recover well-known limits of JKR, DMT, adhesive vesicles with surface tension (BWdG) and thin elastic shells. We further locate biological cells on this parameter space by comparing to existing experiments on S180 cells. Using this model, we show that mechanical parameters can be obtained that are consistent with both Dual Pipette Aspiration (DPA) and Micropipette Aspiration (MA), a problem not successfully tackled so far. We estimate a cortex elastic modulus of Ec ≈ 15 kPa, an effective cortex thickness of tc ≈ 0.3 µm and an active tension of γ ≈ 0.4 nN/µm. With these parameters, a JKR-like scaling of the separation force is recovered. Finally, the change of contact radius with applied force in a pull-off experiment was investigated. For small forces, a scaling similar to both BWdG and DMT is found.Manuscript submitted to Biophysical Journal.

Intermolecular Study of Adansonia Digitata (AnD) Binary Liquid Mixture

2014 ◽  
Vol 348 ◽  
pp. 226-231
Author(s):  
Sushil Phadke ◽  
Suneel Kumar Ujle ◽  
Bhaktdarshan Shrivastava ◽  
Ashutosh Mishra ◽  
Nagesh Dagaonkar
Keyword(s):  
Surface Tension ◽  
Free Energy ◽  
Atp Hydrolysis ◽  
Intermolecular Forces ◽  
Direct Measure ◽  
Adansonia Digitata ◽  
A Cell ◽  
Dynamic Quantity ◽  
Enthalpy And Entropy ◽  
The Universe

The resistance of a liquid to flow and the molecules of a liquid exhibit intermolecular attraction for each another and are called its viscosity and surface tension. Surface tension is measured as the energy required to increase the surface area of a liquid by a unit of area. Viscosity is governed by the strength of intermolecular forces and especially by the shapes of the molecules of a liquid. The surface tension of a liquid results from an imbalance of intermolecular attractive forces, the cohesive forces between molecules. The change in free energy during a reaction, it is a direct measure of the amount disorder that is created in the universe when the reaction occurs. A thermo-dynamic quantity combining enthalpy and entropy into a single value is called the Gibbs free energy ΔG. The value of ΔG for a reaction is a direct measure of how far the reaction is from equilibrium. The large negative value for ATP hydrolysis in a cell merely reflects the fact that cells keep the ATP hydrolysis reaction as much as 10 orders of magnitude away from the equilibrium. The change of free energy is equal to the sum of its enthalpy plus the product of the temperature and entropy of the system. The characteristic time for a system to reach an equilibrium condition after a disturbance is called relaxation time.Adansonia Digitata(AnD) fruit collected from Mandav District Dhar (M.P.). The entire chemical used in this study analytical grade.

On the Law of Spontaneous Spreading of Liquid Droplets on Solid Substrates

2002 ◽  
Author(s):  
Abdullatif M. Alteraifi ◽  
Dalia Sherif ◽  
Abdelsamie Moet
Keyword(s):  
Surface Tension ◽  
Spherical Shape ◽  
Soda Lime ◽  
Solid Substrate ◽  
Contact Radius ◽  
Soda Lime Glass ◽  
Image Analysis System ◽  
Liquid Droplets ◽  
Viscous Forces ◽  
Wide Range

Several theories deal with the spreading kinetics of liquids on solid substrate, notable amongst which is de Gennes’ law, which relates the contact radius, R, to the droplet volume, V, the surface tension, σ, and the viscosity, µ, by the equation R3m+1 = (σ/µ) t Vm and ascertains that m = 3 is “indeed expected theoretically for all cases of dry spreading”. Validity of the proposed models is examined by measurements of the spreading of a number of liquids exhibiting a wide range of surface tension and viscosity on dry soda-lime glass. The measurements used a small droplet of constant volume to minimize gravitational effects. The droplet was released near the glass surface from automatic micro syring, supported on micromanipulator. The contact radius was acquired as a function of time by an image analysis system. Analyzed in terms of de Gennes law, it was noted that the m values for silicone oils fall within the suggested variance i.e., m = 3.0±0.5. However, significant disagreements were noted in the case of other liquids, where m ranged from 5.2 to 15.0 with no correlation with the parameters included. Mechanistic considerations suggest that whereas the surface tension acts to retain the spherical shape of the droplet, interfacial tension acts to maximize the contact area whereas the viscous forces determine the kinetics. The magnitude of the difference between the interfacial and surface energies likely determines whether spreading is complete or incomplete.

Cellular Activity and Biomaterial's Surface Topography

2007 ◽  
Vol 539-543 ◽  
pp. 517-522 ◽  
Author(s):  
Barbara Nebe ◽  
Frank Luethen ◽  
Regina Lange ◽  
Ulrich Beck
Keyword(s):  
Protein Adsorption ◽  
Titanium Surface ◽  
Bone Cells ◽  
Pure Titanium ◽  
Active Surface ◽  
Complete Medium ◽  
Adapter Proteins ◽  
Cellular Activity ◽  
A Cell ◽  
Titanium Surfaces

The contact of a cell on the biomaterial’s surface is mediated by its adhesion components. The topography of titanium surfaces influences these adhesion components of osteoblasts, e.g. the integrins, the adapter proteins and the actin cytoskeleton. In our current experiments we were interested in why osteoblasts were strongly aligned to the grooves of a structured pure titanium surface (grade 2). The titanium was characterized by EIS to get insights in the electro-chemically active surface. We used MG-63 human bone cells, cultured in DMEM with 10% FCS at 37°C. For protein adsorption the titanium discs were incubated for 24h with complete medium containing soluble fibronectin at 37°C. Interestingly, only in the grooves cells adhered and were aligned and this is not dependent on the gravitation. The cell adhesion seems to depend on the protein adsorption of fibronectin which we could find to be adsorbed exclusively in the valleys. We speculate that there are local differences in electro-chemical characteristics of this structured titanium surface.

scholarly journals Scaling up Photoelectrocatalytic Reactors: A TiO2 Nanotube-Coated Disc Compound Reactor Effectively Degrades Acetaminophen

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2522 ◽  
Author(s):  
Renato Montenegro-Ayo ◽  
Juan Carlos Morales-Gomero ◽  
Hugo Alarcon ◽  
Salvador Cotillas ◽  
Paul Westerhoff ◽  
...  
Keyword(s):  
Electric Energy ◽  
Active Surface ◽  
Order Rate Constant ◽  
Active Surface Area ◽  
Current Response ◽  
Proof Of Concept ◽  
Cell Potential ◽  
Tio2 Anatase ◽  
Coated Disc ◽  
A Cell

Multiple discs coated with hierarchically-organized TiO2 anatase nanotubes served as photoelectrodes in a novel annular photoelectrocatalytic reactor. Electrochemical characterization showed light irradiation enhanced the current response due to photogeneration of charge carriers. The pharmaceutical acetaminophen was used as a representative water micropollutant. The photoelectrocatalysis pseudo-first-order rate constant for acetaminophen was seven orders of magnitude greater than electrocatalytic treatment. Compared against photocatalysis alone, our photoelectrocatalytic reactor at <8 V reduced by two fold, the electric energy per order (EEO; kWh m−3 order−1 for 90% pollutant degradation). Applying a cell potential higher than 8 V detrimentally increased EEO. Acetaminophen was degraded across a range of initial concentrations, but absorbance at higher concentration diminished photon transport, resulting in higher EEO. Extended photoelectrocatalytic reactor operation degraded acetaminophen, which was accompanied by 53% mineralization based upon total organic carbon measurements. This proof of concept for our photoelectrocatalytic reactor demonstrated a strategy to increase photo-active surface area in annular reactors.

Airway Closure: Occluding Liquid Bridges in Strongly Buckled Elastic Tubes

1999 ◽  
Vol 121 (5) ◽  
pp. 487-493 ◽  
Author(s):  
M. Heil
Keyword(s):  
Surface Tension ◽  
High Surface ◽  
Elastic Shell ◽  
External Pressure ◽  
Physiological Parameter ◽  
Liquid Bridges ◽  
Deformation Characteristics ◽  
Airway Closure ◽  
Elastic Tubes ◽  
Parameter Values

This paper is concerned with the airway closure problem and investigates the quasi-steady deformation characteristics of strongly collapsed (buckled) airways occluded by liquid bridges of high surface tension. The airway wall is modeled as a thin-walled elastic shell, which deforms in response to an external pressure and to the compression due to the surface tension of the liquid bridge. The governing equations are solved numerically using physiological parameter values. It is shown that axisymmetric configurations are statically unstable, as are buckled tubes whose opposite walls are not in contact. The quasi-steady deformation characteristics of strongly collapsed airways whose walls are in opposite wall contact show a pronounced hysteresis during the collapse/reopening cycle. Buckling is shown to occur over a short axial length with moderate circumferential wavenumbers. Finally, further implications of the results for the airway collapse/reopening problem are discussed.

scholarly journals Indentation of a rigid sphere into an elastic substrate with surface tension and adhesion

2015 ◽  
Vol 471 (2175) ◽  
pp. 20140727 ◽  
Author(s):  
Chung-Yuen Hui ◽  
Tianshu Liu ◽  
Thomas Salez ◽  
Elie Raphael ◽  
Anand Jagota
Keyword(s):  
Surface Tension ◽  
Small Strain ◽  
Work Of Adhesion ◽  
Contact Radius ◽  
Rigid Sphere ◽  
Elastic Substrate ◽  
Indentation Force ◽  
Resistance To Deformation ◽  
Sphere Radius ◽  
Force Displacement

The surface tension of compliant materials such as gels provides resistance to deformation in addition to and sometimes surpassing that owing to elasticity. This paper studies how surface tension changes the contact mechanics of a small hard sphere indenting a soft elastic substrate. Previous studies have examined the special case where the external load is zero, so contact is driven by adhesion alone. Here, we tackle the much more complicated problem where, in addition to adhesion, deformation is driven by an indentation force. We present an exact solution based on small strain theory. The relation between indentation force (displacement) and contact radius is found to depend on a single dimensionless parameter: ω = σ ( μR ) −2/3 ((9 π /4) W ad ) −1/3 , where σ and μ are the surface tension and shear modulus of the substrate, R is the sphere radius and W ad is the interfacial work of adhesion. Our theory reduces to the Johnson–Kendall–Roberts (JKR) theory and Young–Dupre equation in the limits of small and large ω , respectively, and compares well with existing experimental data. Our results show that, although surface tension can significantly affect the indentation force, the magnitude of the pull-off load in the partial wetting liquid-like limit is reduced only by one-third compared with the JKR limit and the pull-off behaviour is completely determined by ω .

General Relations of Indentations on Solids With Surface Tension

2017 ◽  
Vol 84 (5) ◽  
Author(s):  
Jianmin Long ◽  
Yue Ding ◽  
Weike Yuan ◽  
Wen Chen ◽  
Gangfeng Wang
Keyword(s):  
Surface Tension ◽  
Contact Mechanics ◽  
Integral Equations ◽  
Analytical Solutions ◽  
Integral Kernel ◽  
Singular Integral Equations ◽  
Elastic Half Space ◽  
Contact Radius ◽  
Rigid Sphere ◽  
General Relations

The conventional contact mechanics does not account for surface tension; however, it is important for micro- or nanosized contacts. In the present paper, the influences of surface tension on the indentations of an elastic half-space by a rigid sphere, cone, and flat-ended cylinder are investigated, and the corresponding singular integral equations are formulated. Due to the complicated structure of the integral kernel, it is difficult to obtain their analytical solutions. By using the Gauss–Chebyshev quadrature formula, the integral equations are solved numerically first. Then, for each indenter, the analytical solutions of two limit cases considering only the bulk elasticity or surface tension are presented. It is interesting to find that, through a simple combination of the solutions of two limit cases and fitting the direct numerical results, the dependence of load on contact radius or indent depth for general case can be given explicitly. The results incorporate the contribution of surface tension in contact mechanics and are helpful to understand contact phenomena at micro- and nanoscale.

Are elastic moduli of biological cells depth dependent or not? Another explanation using a contact mechanics model with surface tension

Soft Matter ◽  
2018 ◽  
Vol 14 (36) ◽  
pp. 7534-7541 ◽  
Author(s):  
Yue Ding ◽  
Jian Wang ◽  
Guang-Kui Xu ◽  
Gang-Feng Wang
Keyword(s):  
Surface Tension ◽  
Elastic Modulus ◽  
Contact Mechanics ◽  
Elastic Moduli ◽  
Contact Model ◽  
Biological Cells ◽  
Mechanics Model ◽  
Afm Indentation ◽  
A Cell ◽  
Indent Depth

Contrary to the existing reports that the apparent elastic modulus of a cell depends strongly on the indent depth in many AFM indentation experiments, we present a contact model with surface effects, and show that the actual elastic modulus of cell materials could be independent of the indent depth if surface tension is taken into account.

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