Name: protrusion force microscopy: a method to quantify forces developed by cell protrusions
Uploaded: 2018-06-16T14:00:00
Description: Watch this Scientific Journal Video about Protrusion Force Microscopy: A Method to Quantify Forces Developed by Cell Protrusions at JoVE.com

The authors are grateful to Anna Labernadie, Guillaume Charri&#232;re and Patrick Delobelle for their initial contribution to this work and to Matthieu Sanchez and Fran&#231;oise Viala for their help with video filming and editing. This work has been supported by l'Agence Nationale de la Recherche (ANR14-CE11-0020-02), la Fondation pour la Recherche M&#233;dicale (FRM DEQ2016 0334894), INSERM Plan Cancer, Fondation Toulouse Cancer and Human Frontier Science Program (RGP0035/2016).

1. Preparation of Formvar-Coated Grids
<ol>
	<li>Clean electron microscopy grids with pure acetone and dry them on filter paper. Then clean a microscope slide with pure ethanol, wipe with a lens paper and remove dust with a blower.</li>
	<li>Place an ethanol-cleaned glass slide vertically in the funnel of a film casting device containing a solution of Formvar in the lower part. Cover the top of the funnel.</li>
	<li>Pump 100 mL of Formvar solution (0.5% in ethylene dichloride) with the atomizer bulb until the level rea...

<ol>
	<li>Discher, D. E., Janmey, P., Wang, Y. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tissue+Cells+Feel+and+Respond+to+the+Stiffness+of+Their+Substrate.">Tissue Cells Feel and Respond to the Stiffness of Their Substrate.</a> Science. 310, 1139-1143 (2005).</li><li>Paszek, M. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tensional+Homeostasis+and+the+Malignant+Phenotype.">Tensional Homeostasis and the Malignant Phenotype.</a> Cancer Cell. 8, 241-254 (2005).</li><li>Engler, A. J., Sen, S., Sweeney, H. L., Discher, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Matrix+Elasticity+Directs+Stem+Cell+Lineage+Specification.">Matrix Elasticity Directs Stem Cell Lineage Specification.</a> Cell. 126, 677-689 (2006).</li><li>Gilbert, P. M., Weaver, V. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+Adaptation+to+Biomechanical+Stress+across+Length+Scales+in+Tissue+Homeostasis+and+Disease.">Cellular Adaptation to Biomechanical Stress across Length Scales in Tissue Homeostasis and Disease.</a> Seminars in Cell &amp; Developmental Biology. 67, 141-152 (2017).</li><li>Vining, K. H., Mooney, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+Forces+Direct+Stem+Cell+Behaviour+in+Development+and+Regeneration.">Mechanical Forces Direct Stem Cell Behaviour in Development and Regeneration.</a> Nature Reviews Molecular Cell Biology. , (2017).</li><li>Roca-Cusachs, P., Conte, V., Trepat, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantifying+Forces+in+Cell+Biology.">Quantifying Forces in Cell Biology.</a> Nature Cell Biology. 19, 742-751 (2017).</li><li>Labernadie, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protrusion+Force+Microscopy+Reveals+Oscillatory+Force+Generation+and+Mechanosensing+Activity+of+Human+Macrophage+Podosomes.">Protrusion Force Microscopy Reveals Oscillatory Force Generation and Mechanosensing Activity of Human Macrophage Podosomes.</a> Nature Communications. 5, 5343 (2014).</li><li>Proag, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Working+Together:+Spatial+Synchrony+in+the+Force+and+Actin+Dynamics+of+Podosome+First+Neighbors.">Working Together: Spatial Synchrony in the Force and Actin Dynamics of Podosome First Neighbors.</a> ACS Nano. 9, 3800-3813 (2015).</li><li>Proag, A., Bouissou, A., Vieu, C., Maridonneau-Parini, I., Poincloux, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+the+Force+and+Spatial+Dynamics+of+Macrophage+Podosomes+by+Multi-Particle+Tracking.">Evaluation of the Force and Spatial Dynamics of Macrophage Podosomes by Multi-Particle Tracking.</a> Methods. 94, 75-84 (2016).</li><li>Cougoule, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-Dimensional+Migration+of+Macrophages+Requires+Hck+for+Podosome+Organization+and+Extracellular+Matrix+Proteolysis.">Three-Dimensional Migration of Macrophages Requires Hck for Podosome Organization and Extracellular Matrix Proteolysis.</a> Blood. 115, 1444-1452 (2010).</li><li>Cougoule, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blood+Leukocytes+and+Macrophages+of+Various+Phenotypes+Have+Distinct+Abilities+to+Form+Podosomes+and+to+Migrate+in+3d+Environments.">Blood Leukocytes and Macrophages of Various Phenotypes Have Distinct Abilities to Form Podosomes and to Migrate in 3d Environments.</a> European Journal of Cell Biology. 91, 938-949 (2012).</li><li>Guiet, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macrophage+Mesenchymal+Migration+Requires+Podosome+Stabilization+by+Filamin+A.">Macrophage Mesenchymal Migration Requires Podosome Stabilization by Filamin A.</a> Journal of Biological Chemistry. 287, 13051-13062 (2012).</li><li>Maridonneau-Parini, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+of+Macrophage+3d+Migration:+A+Therapeutic+Challenge+to+Limit+Tissue+Infiltration.">Control of Macrophage 3d Migration: A Therapeutic Challenge to Limit Tissue Infiltration.</a> Immunology Review. 262, 216-231 (2014).</li><li>Park, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tyrosine+Phosphorylation+of+Wiskott-Aldrich+Syndrome+Protein+(Wasp)+by+Hck+Regulates+Macrophage+Function.">Tyrosine Phosphorylation of Wiskott-Aldrich Syndrome Protein (Wasp) by Hck Regulates Macrophage Function.</a> Journal of Biological Chemistry. 289, 7897-7906 (2014).</li><li>Van Goethem, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macrophage+Podosomes+Go+3d.">Macrophage Podosomes Go 3d.</a> European Journal of Cell Biology. 90, 224-236 (2011).</li><li>Van Goethem, E., Poincloux, R., Gauffre, F., Maridonneau-Parini, I., Le Cabec, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Matrix+Architecture+Dictates+Three-Dimensional+Migration+Modes+of+Human+Macrophages:+Differential+Involvement+of+Proteases+and+Podosome-Like+Structures.">Matrix Architecture Dictates Three-Dimensional Migration Modes of Human Macrophages: Differential Involvement of Proteases and Podosome-Like Structures.</a> Journal of Immunology. 184, 1049-1061 (2010).</li><li>Verollet, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hiv-1+Reprograms+the+Migration+of+Macrophages.">Hiv-1 Reprograms the Migration of Macrophages.</a> Blood. 125, 1611-1622 (2015).</li><li>Bouissou, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Podosome+Force+Generation+Machinery:+A+Local+Balance+between+Protrusion+at+the+Core+and+Traction+at+the+Ring.">Podosome Force Generation Machinery: A Local Balance between Protrusion at the Core and Traction at the Ring.</a> ACS Nano. 11, 4028-4040 (2017).</li><li>Lizarraga, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diaphanous-Related+Formins+Are+Required+for+Invadopodia+Formation+and+Invasion+of+Breast+Tumor+Cells.">Diaphanous-Related Formins Are Required for Invadopodia Formation and Invasion of Breast Tumor Cells.</a> Cancer Research. 69, 2792-2800 (2009).</li><li>Carman, C. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcellular+Diapedesis+Is+Initiated+by+Invasive+Podosomes.">Transcellular Diapedesis Is Initiated by Invasive Podosomes.</a> Immunity. 26, 784-797 (2007).</li><li>Sage, P. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antigen+Recognition+Is+Facilitated+by+Invadosome-Like+Protrusions+Formed+by+Memory/Effector+T+Cells.">Antigen Recognition Is Facilitated by Invadosome-Like Protrusions Formed by Memory/Effector T Cells.</a> Journal of Immunology. 188, 3686-3699 (2012).</li><li>Sens, K. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+Invasive+Podosome-Like+Structure+Promotes+Fusion+Pore+Formation+During+Myoblast+Fusion.">An Invasive Podosome-Like Structure Promotes Fusion Pore Formation During Myoblast Fusion.</a> Journal of Cell Biology. 191, 1013-1027 (2010).</li><li>Takito, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Transient+Appearance+of+Zipper-Like+Actin+Superstructures+During+the+Fusion+of+Osteoclasts.">The Transient Appearance of Zipper-Like Actin Superstructures During the Fusion of Osteoclasts.</a> Journal of Cell Science. 125, 662-672 (2012).</li><li>Shilagardi, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Actin-Propelled+Invasive+Membrane+Protrusions+Promote+Fusogenic+Protein+Engagement+During+Cell-Cell+Fusion.">Actin-Propelled Invasive Membrane Protrusions Promote Fusogenic Protein Engagement During Cell-Cell Fusion.</a> Science. 340, 359-363 (2013).</li><li>Freeman, S. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integrins+Form+an+Expanding+Diffusional+Barrier+That+Coordinates+Phagocytosis.">Integrins Form an Expanding Diffusional Barrier That Coordinates Phagocytosis.</a> Cell. 164, 128-140 (2016).</li></ol>

Material properties
The choice of the material for the deformable membrane, in our case Formvar, needs to fulfill a few requirements. The material must be transparent to visible light and exhibit limited auto fluorescence to allow observations in bright field and fluorescence microscopy. The roughness of the thin film must be well below 10 nm to avoid any topographical effect on cell adhesion and to allow clear observation of the cell-induced protrusions by AFM imaging. Finall...

Animal cells interact physically with the matrix and the other cells that constitute their environment1. This is required for them to migrate, internalize bodies, acquire external information, or differentiate. In such processes, the cell must generate mechanical forces and, as numerous studies have shown over the recent years, the ability of a cell to generate forces and probe its environment influences its biological behavior, directing for instance proliferation or differentiation2,3. In turn, the measurement of cellular forces is a major aid to study the regulation of force generation and understand its implication in cell behavior and tissue fate4,5.
Recent years have witnessed the development of numerous techniques to measure the forces that a cell can exert on its environment6. The majority of these have been instrumental in revealing the traction forces that cells exert as they pull on mobile probes or a deformable substrate. However, the mechanical forces involved in protrusion into the extracellular environment suffer from a lack of measurement techniques and are to date not well characterized.
To overcome this limitation, we present a method to measure forces exerted orthogonally to the substrate. It consists in plating living cells on a thin elastic sheet that can deform in the orthogonal direction, making it possible to measure substrate deformation by the cells and deduce the forces involved. Substrate topography is measured with nanoscale resolution using atomic force microscopy and the evaluation of forces from deformation relies on the knowledge of the geometry of the protrusive cellular structures7,8,9.
Here, we describe the setup and its application to measure the forces generated by podosomes, protrusive adhesion structures formed by macrophages for their mesenchymal migration in three-dimensional environments10,11,12,13,14,15,16,17. We believe that this technique will advance the understanding of force generation and its regulation in the many cellular processes involving protrusion.

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	<tbody>
		<tr height="51">
			<td height="51" style="height:51px;width:216px;">200 mesh nickel grids</td>
			<td style="width:71px;">Electron Microscopy Sciences</td>
			<td style="width:119px;">G200-Ni</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:216px;">Filter paper</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">1001-055</td>
			<td></td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:216px;">Microscope slides</td>
			<td style="width:71px;">Fisher Scientific</td>
			<td style="width:119px;">10235612</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">White stickers 26 x 70 mm</td>
			<td style="width:71px;">Avery</td>
			<td style="width:119px;">DP033-100</td>
			<td></td>
		</tr>
		<tr height="51">
			<td height="51" style="height:51px;width:216px;">Film casting device with valve in its outlet</td>
			<td style="width:71px;">Electron Microscopy Sciences</td>
			<td style="width:119px;">71305-01</td>
			<td></td>
		</tr>
		<tr height="51">
			<td height="51" style="height:51px;width:216px;">Razorblades</td>
			<td style="width:71px;">Electron Microscopy Sciences</td>
			<td style="width:119px;">72000</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ethanol</td>
			<td style="width:71px;">VWR</td>
			<td style="width:119px;">1.08543.0250</td>
			<td></td>
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			<td height="21" style="height:21px;width:216px;">Acetone</td>
			<td style="width:71px;">VWR</td>
			<td style="width:119px;">20066.321</td>
			<td></td>
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		<tr height="51">
			<td height="51" style="height:51px;width:216px;">Formvar 0.5% solution in ethylene dichloride</td>
			<td style="width:71px;">Electron Microscopy Sciences</td>
			<td style="width:119px;">15820</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">12 mm coverslips</td>
			<td style="width:71px;">VWR</td>
			<td style="width:119px;">631-0666</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Inverted microscope</td>
			<td style="width:71px;">Carl Zeiss</td>
			<td style="width:119px;">Axiovert 200</td>
			<td></td>
		</tr>
		<tr height="51">
			<td height="51" style="height:51px;width:216px;">Atomic Force Microscope</td>
			<td style="width:71px;">JPK Instruments</td>
			<td style="width:119px;">NanoWizard III</td>
			<td></td>
		</tr>
		<tr height="51">
			<td height="51" style="height:51px;width:216px;">Temperature-controlled sample holder&#160;</td>
			<td style="width:71px;">JPK Instruments</td>
			<td style="width:119px;">BioCell</td>
			<td></td>
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		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Silicon nitride cantilever with a nominal spring constant of 0.01 N/m</td>
			<td style="width:71px;">Veeco Instruments</td>
			<td style="width:119px;">MLCT-AUHW</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">PBS</td>
			<td style="width:71px;">Gibco</td>
			<td style="width:119px;">14190-094</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Double-sided adhesive tape</td>
			<td style="width:71px;">APLI AGIPA</td>
			<td style="width:119px;">118100</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">RPMI 1640</td>
			<td style="width:71px;">Gibco</td>
			<td style="width:119px;">31870-025</td>
			<td></td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:216px;">FCS</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">F7524</td>
			<td></td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:216px;">HEPES&#160;</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">H0887</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">35 mm glass-bottom Petri dishes</td>
			<td style="width:71px;">WPI</td>
			<td style="width:119px;">FD35-100</td>
			<td></td>
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protrusion force microscopy: a method to quantify forces developed by cell protrusions

In numerous biological contexts, animal cells need to interact physically with their environment by developing mechanical forces. Among these, traction forces have been well-characterized, but there is a lack of techniques allowing the measurement of the protrusion forces exerted by cells orthogonally to their substrate. We designed an experimental setup to measure the protrusion forces exerted by adherent cells on their substrate. Cells plated on a compliant Formvar sheet deform this substrate and the resulting topography is mapped by atomic force microscopy (AFM) at the nanometer scale. Force values are then extracted from an analysis of the deformation profile based on the geometry of the protrusive cellular structures. Hence, the forces exerted by the individual protruding units of a living cell can be measured over time. This technique will enable the study of force generation and its regulation in the many cellular processes involving protrusion. Here, we describe its application to measure the protrusive forces generated by podosomes formed by human macrophages.

The above protocol describes how to prepare the experimental setup to quantify protrusion forces applied by macrophage podosomes on a Formvar substrate. This is achieved using AFM and is illustrated in Figure 1.
When analyzing a topographical image of bulges beneath podosomes using the JPK data processing software, a third-degree polynomial fit should be subtracted from each scan line independently....

Watch this Scientific Journal Video about Protrusion Force Microscopy: A Method to Quantify Forces Developed by Cell Protrusions at JoVE.com

Protrusion Force Microscopy: A Method to Quantify Forces Developed by Cell Protrusions

Here, we detail the experimental techniques used to evaluate the protrusion forces that podosomes apply on a compliant film, from the preparation of the film to the automated analysis of topographical images.

In numerous biological contexts, animal cells need to interact physically with their environment by developing mechanical forces. Among these, traction ...

The overall goal of this procedure is to quantify protrusion forces using atomic force microscopy. This is accomplished by first preparing the formula coated grids and measuring the thickness of this film. The third step of this process consist in seating cells on the grids and leaving them to adhere.The final step of the procedure is to image the forma film beneath the cells using atomic force microscopy. When adhering to substrate, microphages form submicrometric adhesion structures call podosomes. Ultimately, the deformation of the film in used by podosomes will be quantified and converted into forces using a homemade mechanical model.Place an ethanol clean glass light into the funnel film casting device and cover the top of the funnel. Pan the fomvar solution up into the funnel until the level reaches two third of the slide. Leave it in for one minute then drain the formvar solution in a steady stream.Note that the thickness of the film depends both on the stream rate and on the concentration of the formvar solution. Pat this light dry darkedly and cut out rectangles with a sharp razor blade. Dip the slide into your beaker filled with distilled water so that the fomvar film floats onto the water surface.Carefully place acetone clean grids onto the films, shiny face up with a 12 millimeter diameter cover slip on top of some of them. They will be used for the thickness assessment experiment. Eventually dip a sticker covered slide to recover the whole film and grids.Outline the glass covered slip with tweezers to cut the formvar and detach it from the slide. Mount the location of the grid beneath the covered slip then outline the grid with tweezers to pull it off. The hole in the fomvar film thus created will be imaged to measure its thickness.Mount a silicon nitrate cont deliver in the AFM glass block making sure the golden stripe isn't beneath the tip of the spring. Mount the glass block onto the AFM module then place the latter onto the microscope stage. Place the fomvar coated cover slip on the observation chamber with PBS on top.Scan the border between fomvar and glass in contact mode and with a 0.5 nano newton point. In the data processing software, use the glass surface as height reference, and measure fomvar thickness on the cross section. Under a sterile hood pick a 12 millimeter cover slip and stick a strip of the hole sided tape on it.Outline the fomavr coated grid with tweezers and place it shiny face up so it will only it sides attach to the adhesive. This is to prevent fomvar from being torn when removing the grid from the tape. Place the cover strip into a sterile six well plate and pipe in a 10 millimeter droplet of serum free culture medium.It should contain approximately 10 thousand cells and in this case, these are microphages differentiated from human monocytes. Make sure not to touch the grid with the piper tip in the process, so as not to damage the fomvar coating. Incubate for half an hour to let the cells adhere, then fill up the well with serum supplemented medium, and incubate again for two hours, before AFM observation.Place two parallel strips of double sided tape on a glass bottom petri dish, making sure the width between them is slightly smaller, compared to your grid diameter. Then detach the grid previously seeded with cells and place it on top of the two tape strips with cells facing down. Fix the grid by placing two other strips on top of the pervious ones.Fill the dish with preheated culture medium supplemented with hepe's. Place the dish into the dish heater previously set at 37 celsius degrees. Install the set on the AFM stage.When the system temperature is stable at 37 celsius degrees proceed to the scan of the fomvar surface, which should be performed in the contact mode, with a 0.95 nano newton set point and visual the protozoan associated deformations on the deflection data view window. Here are the representative results and processing steps to yield formations with AFM to the graphical measurements. As you can see on this image, bulges on the fomvar surface are detected.In order to convert this photographical information into force values it is necessary to first have access to the local high difference. To do so a third degree polynomial fit should be subtracted to its scan line independently. Then the use of a homemade dedicated imagery algorithm allows to evaluate protrusion force values from AFM height map an the mechanical model of protozoan mediated protrusion.Thanks to this procedure, we are able to investigate the mechanisms involved in protrusion force generation at protozoans. Thank you for watching, and good luck for your experiments.

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Applications of Spatio-temporal Mapping and Particle Analysis Techniques to Quantify Intracellular Ca2+ Signaling In Situ

Ca2+ imaging of isolated cells or specific types of cells within intact tissues often reveals complex patterns of Ca2+ signaling. This activity requires ...

Live-cell Imaging of Single-Cell Arrays (LISCA) - a Versatile Technique to Quantify Cellular Kinetics

Live-cell Imaging of Single-Cell Arrays LISCA - a Versatile Technique to Quantify Cellular Kinetics

Live-cell Imaging of Single-Cell Arrays (LISCA) is a versatile method to collect time courses of fluorescence signals from individual cells in high ...