This work was supported by the Committee Technology and Innovation (CTI) Switzerland grant 14796-PFLS-LSCTI. MicroPost arrays were generously provided by MicroDuits GmbH.

1. Culturing Cells on Micropost Arrays
Note: All steps must be performed in a biosafety cabinet to ensure sterility. The volumes given here are for T25 cell culture flasks. The cell culture medium recipe and cell seeding density are optimized for bone cancer cell lines HuO9 and M132.
<ol>
	<li>Prepare a cell culture for seeding onto a micropost array.
	<ol>
		<li>Inspect the cell culture quality by placing the culture flask on a standard light microscope. Ensure that the cells show a typical growth and morphology by estimating how much of the culture flask bottom is covered. A coverage of 70%-80% reflects a healthy growth rate. Pay attention to the amount of floating cells as they represent dead cells and/or an overgrown culture.</li>
		<li>Trypsinize cells by removing medium and washing with 4 ml 1x Phosphate buffered saline (PBS) buffer. Add 0.8 ml 1x Trypsin/Ethylenediaminetetraacetic acid (EDTA) and incubate at RT until the cells dislodge, which takes about 2-4 min. Check the process with the microscope and occasionally tap the flask gently to support the dislodging.</li>
		<li>Add 5 ml cell culture medium (Dulbecco&#8217;s modified Eagle medium (DMEM)/F12 with 10% fetal bovine serum (FBS), 1% penicillin/streptavidin (Pen/Strep)) to stop the reaction and to wash off residual cells that still sit on the flask&#8217;s bottom. Subsequently pipette this suspension up and down several times to gain a homogenous mixture. Make sure to pipette all solutions across the original growth area of the flask to gain an effective dislodging.</li>
		<li>Transfer the cell suspension in to a 15 ml tube and centrifuge it using a table top centrifuge at 0.5 x g for 3 min.</li>
		<li>Remove the supernatant and re-suspend the cell pellet in 5 ml medium by pipetting up and down 5 times. Make sure to avoid the generation of bubbles while doing so.</li>
		<li>Determine cell density by using a cell counting chamber and a light microscope. Check the cell suspension in cell counting chamber for cell aggregates and ensure to have only single cells for the subsequent experiment. Pipette again up and down several times if the cells tend to form aggregates to separate them.</li>
		<li>Dilute the cell suspension with sufficient medium to gain a cell solution of 25,000 cells/ml. Mix it well by inverting the closed tube several times.&#160;</li>
	</ol>
	</li>
	<li>Prepare a micropost array for cell seeding. 
	Critical Note: Do not pipette onto the micropost array directly as this could potentially harm the microposts, especially when unwanted bubbles are introduced. Furthermore, make sure that the micropost array never dries out as occurring capillary forces lead to collapsing of the microposts.
	<ol>
		<li>Place the glass substrate with the micropost array face up in a well of a 12-well plate by using a pair of tweezers and wet it by adding 1 ml ethanol (99%). Incubate at RT for 20-30 sec.</li>
		<li>Dilute the ethanol stepwise by adding approximately 1 ml sterile de-ionized water (DI water) on the well side and aspirating roughly 1 ml using a transfer pipette or aspiration device. Repeat this step at least 3 times.</li>
		<li>Replace the DI-water with PBS-buffer in the same manner by adding and aspirating approximately 1 ml. Repeat this step 3 times.</li>
		<li>Replace the PBS-buffer with medium by adding and aspirating approximately 1 ml of medium. Repeat this step 3 times.</li>
	</ol>
	</li>
	<li>Pipette 1 ml cell solution (25,000 cells) on top of each prepared micropost array. Close multi-well plate and transfer it to an incubator (CO2 5%, 37 &#176;C). Let the cells adhere and grow on top of microposts for 6&#160;-7 hr.</li>
	<li>Inspect the adhesion process occasionally by using a light a microscope. Check that most of the cells appear spread out across multiple microposts.</li>
</ol>
2. Fixing &#38; Staining Cells
Note: All steps and volumes given here are for a single well of a 12-well plate. It is recommended to process not more than four of the twelve wells at a time to avoid a drying out of the wells after aspiration of any liquid, which will result in a collapse of the microposts.
<ol>
	<li>Aspirate medium from the well and wash cells 2x with 1 ml PBS-buffer. Make sure to apply a gentle force while washing with PBS to remove cell debris that accumulated on the micropost array during incubation and to detach dead cells.</li>
	<li>Fix the cells with 0.5 ml 3.7% buffered formaldehyde solution for 5 min.</li>
	<li>Replace the formaldehyde solution by washing the micropost array 2x with 1 ml sterile DI water.</li>
	<li>Stain the cells with dye (0.05% Coomassie Brilliant Blue in 50% water, 40% ethanol and 10% acetic acid) for about 90 sec. Wash excess staining solution off 2x with 1&#160;ml sterile DI water. Add 1 ml DI water to micropost array.</li>
	<li>Check staining result using a light microscope. Repeat the staining step, if cell body is too faint to be visualized.</li>
	<li>Store micropost arrays with the stained cells on top in a refrigerator at 4 &#176;C. Ensure to keep them under water at all times.</li>
</ol>
3. Cell Imaging
Note: Step 4 only applies to microscopes without infinity corrected optics.
<ol>
	<li>Add 2 ml DI-water to a Petri dish with a thin glass bottom for high resolution imaging.</li>
	<li>Transfer micropost array using a pair of tweezers into the imaging dish with the microposts facing up.</li>
	<li>Place the imaging Petri dish on a moveable stage of a light microscope.</li>
	<li>Turn the compensation ring of the lens used for imaging until the number on the scale represents the total thickness of all materials along the optical path to compensate for the mismatch in refractive indices of the glass substrate, the silicone elastomer and the liquid on top. This should lead to a bright appearance of the microposts cores.</li>
	<li>Close the iris on the illumination side down to 50% and remove any phase contrast rings from the optical path enabling an ordinary bright-field mode.</li>
	<li>Align the micropost array that the microposts form a horizontal line across the observation field. Define a start point (e.g., top left) and move the Petri dish stepwise across the stage scanning the micropost array while taking numerous images.</li>
	<li>Take all images with the highest resolution setting for the camera using a 20X or 40X objective. Aim to have a single cell in the center of the image.</li>
	<li>Sweep along the z-axis through the substrate until the micropost tips are in focus. Use the fine tuning focus wheel of the microscope and turn it towards focusing on the micropost bottom for about 2-3 &#181;m.</li>
	<li>Establish a standard imaging procedure by taking series of test images of one array section sweeping through the imaging parameters one at a time (e.g., exposure time, iris setting, lamp settings etc.). Analyze images with MechProfiler and determine a suitable parameter set for a fast and reliable analysis.</li>
</ol>
4. Image Analysis with Open Source Software &#8220;MechProfiler&#8221;
Note: All software functions can be activated with a pointing device using the left mouse button. However, a trained operator will use the documented shortcut keys designed to be on the left half of the keyboard to enable an efficient two-handed image processing.
<ol>
	<li>Start image analysis software MechProfiler and open a range of images that need to be analyzed by clicking &#8220;Open&#8221;.</li>
	<li>Insert all parameters into the &#8220;Settings&#8221; section given by the software developer. Determine the parameters that must be custom configured (i.e., contour threshold and minimal distance) according to the procedures described in detail by the software manual.</li>
	<li>Analyze images one-by-one by cropping them to the area of interest by using &#8220;Crop&#8221; (click and drag with the mouse button pressed down). Double click inside the drawn rectangle to finish this action.</li>
	<li>Marking each visible cell outline one-by-one by clicking on &#8220;Draw cell outlines&#8221; and use the cross hair cursor for drawing including all microposts the cell is attached to.</li>
	<li>Discard any unwanted microposts by clicking &#8220;Discard Posts&#8221; and use the cross hair cursor for drawing. Enclose all microposts that belong to a cell outside of the image section or that are deflected for any other reason but not by the cell of interest.</li>
	<li>Start the software subroutine &#8220;Find Centroids&#8221; by mouse click. Adjust the filter setting right next to the &#8220;Find Centroids&#8221; button until all microposts are registered, which is visible by a red cross in their center. If the filter setting is too low microposts will be ignored, if it is too high multiple positions will be marked for a single micropost. Keep the filter setting constant during an analysis session.</li>
	<li>Use the manual editing function &#8220;Manual Edit&#8221; for centroids with multiple or missed micropost positions. Use the mouse cross hair to select the micropost in question by clicking and dragging it across. Double click inside the rectangle and place the missing red marker in the enlarged image section, which automatically closes. Discard such a micropost if it is outside the drawn cell outline (see step 4.5) before proceeding.</li>
	<li>Find the ideal micropost grid by activating the &#8220;Generate Grid&#8221; function with a mouse click. Ensure the position corresponds with the true micropost head, shown by a blue ring, inside the drawn cell outline.</li>
	<li>Correct any misplaced grid maker inside the cell area where needed using the corresponding &#8220;Manuel Edit&#8221; function with a mouse click. Use the cross hair to select the micropost in question by clicking and dragging it across. Double click inside the appearing rectangle and place the missing blue marker in the enlarged image section, which automatically closes.</li>
	<li>Use the button &#8220;Calculate Deflections&#8221; by mouse click to get a histogram of the calculated deflection values based on the difference between a micropost&#8217;s position inside the image section and the generated ideal grid.</li>
	<li>Save the complete analysis including the tables of values by a mouse click on &#8220;Save&#8221;.</li>
	<li>Continue the image analysis either by clicking on &#8220;Reset View&#8221; and analyze another image section or mouse click on &#8220;Next Image&#8221;, which conveniently can be done using the right keyboard curser key.</li>
</ol>
5. Data Analysis &#8212; Mechanoprofiling
<ol>
	<li>Open the file &#8220;results.xls&#8221; with an office spreadsheet program from the folder with the analyzed images. It contains the data with all calculated values including all micropost deflections and standard derivative measures such as work (i.e., substrate deformation energy) by the analyzed cell.</li>
</ol>

<ol>
	<li>Sharma, R. I., Snedeker, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biochemical+and+biomechanical+gradients+for+directed+bone+marrow+stromal+cell+differentiation+toward+tendon+and+bone.">Biochemical and biomechanical gradients for directed bone marrow stromal cell differentiation toward tendon and bone.</a> Biomaterials. 31 (30), 7695-7704 (2010).</li><li>Suresh, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomechanics+and+biophysics+of+cancer+cells.">Biomechanics and biophysics of cancer cells.</a> Acta Biomater. 3 (4), 413-438 (2007).</li><li>Bartalena, G., 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=A+novel+method+for+assessing+adherent+single-cell+stiffness+in+tension:+design+and+testing+of+a+substrate-based+live+cell+functional+imaging+device.">A novel method for assessing adherent single-cell stiffness in tension: design and testing of a substrate-based live cell functional imaging device.</a> Biomed Microdevices. 13 (2), 291-301 (2011).</li><li>Tan, J. 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=Cells+lying+on+a+bed+of+microneedles:+An+approach+to+isolate+mechanical+force.">Cells lying on a bed of microneedles: An approach to isolate mechanical force.</a> PNAS. 100 (4), 1484-1489 (2003).</li><li>Akiyama, Y., Hoshino, T., Iwabuchi, K., Morishima, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Room+Temperature+Operable+Autonomously+Moving+Bio-Microrobot+Powered+by+Insect+Dorsal+Vessel+Tissue.">Room Temperature Operable Autonomously Moving Bio-Microrobot Powered by Insect Dorsal Vessel Tissue.</a> PloS ONE. 7 (7), (2012).</li><li>Biais, N., Ladoux, B., Higashi, D., So, M., Sheetz, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cooperative+retraction+of+bundled+type+IV+pili+enables+nanonewton+force+generation.">Cooperative retraction of bundled type IV pili enables nanonewton force generation.</a> Plos Biology. 6 (4), 907-913 (2008).</li><li>Wuang, S. C., Ladoux, B., Lim, C. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+the+Chemo-Mechanical+Effects+of+an+Anti-Cancer+Drug+Emodin+on+Breast+Cancer+Cells.">Probing the Chemo-Mechanical Effects of an Anti-Cancer Drug Emodin on Breast Cancer Cells.</a> Cell Mol Bioeng. 4 (3), 466-475 (2011).</li><li>Schoen, I., Hu, W., Klotzsch, E., Vogel, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+Cellular+Traction+Forces+by+Micropillar+Arrays:+Contribution+of+Substrate+Warping+to+Pillar+Deflection.">Probing Cellular Traction Forces by Micropillar Arrays: Contribution of Substrate Warping to Pillar Deflection.</a> Nano Lett. 10 (5), 1823-1830 (2010).</li><li>Lemmon, C. 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=Shear+Force+at+the+Cell-Matrix+Interface:+Enhanced+Analysis+for+Microfabricated+Post+Array+Detectors.">Shear Force at the Cell-Matrix Interface: Enhanced Analysis for Microfabricated Post Array Detectors.</a> Mech Chem Biosyst. 2 (1), 1-16 (2005).</li><li>Lam, R. H. W., Weng, S. N., Lu, W., Fu, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Live-cell+subcellular+measurement+of+cell+stiffness+using+a+microengineered+stretchable+micropost+array+membrane.">Live-cell subcellular measurement of cell stiffness using a microengineered stretchable micropost array membrane.</a> Integr Biol-UK. 4 (10), 1289-1298 (2012).</li><li>Roure, O., 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=Force+mapping+in+epithelial+cell+migration.">Force mapping in epithelial cell migration.</a> PNAS. 102 (39), 14122-14122 (2005).</li><li>Papenburg, B. J., Rodrigues, E. D., Wessling, M., Stamatialis, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insights+into+the+role+of+material+surface+topography+and+wettability+on+cell-material+interactions.">Insights into the role of material surface topography and wettability on cell-material interactions.</a> Soft Matter. 6 (18), 4377-4388 (2010).</li><li>Badique, 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=Directing+nuclear+deformation+on+micropillared+surfaces+by+substrate+geometry+and+cytoskeleton+organization.">Directing nuclear deformation on micropillared surfaces by substrate geometry and cytoskeleton organization.</a> Biomaterials. 34 (12), 2991-3001 (2013).</li><li>Sniadecki, N. 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=Magnetic+microposts+as+an+approach+to+apply+forces+to+living+cells.">Magnetic microposts as an approach to apply forces to living cells.</a> PNAS. 104 (37), 14553-14558 (2007).</li><li>Weng, R. H. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+silicone-based+stretchable+micropost+array+membrane+for+monitoring+live-cell+subcellular+cytoskeletal+response.">A silicone-based stretchable micropost array membrane for monitoring live-cell subcellular cytoskeletal response.</a> Lab Chip. 12, 731-740 (2012).</li><li>Desai, R. A., Yang, M. T., Sniadecki, N. J., Legant, W. R., Chen, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfabricated+Post-Array-Detectors+(mPADs):+an+Approach+to+Isolate+Mechanical+Forces.">Microfabricated Post-Array-Detectors (mPADs): an Approach to Isolate Mechanical Forces.</a> J Vis Exp. (8), e311 (2007).</li><li>Yang, M. T., Fu, J. P., Wang, Y. K., Desai, R. A., Chen, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assaying+stem+cell+mechanobiology+on+microfabricated+elastomeric+substrates+with+geometrically+modulated+rigidity.">Assaying stem cell mechanobiology on microfabricated elastomeric substrates with geometrically modulated rigidity.</a> Nat Protoc. 6 (2), 187-213 (2011).</li><li>Sniadecki, N. J., Han, S. J., Ting, L. H., Feghhi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micropatterning+in+Cell+Biology.">Micropatterning in Cell Biology.</a> Methods in Cell Biol. 121, 61-73 (2014).</li></ol>

The lead author (NG) is co-founder of MicroDuits GmbH, the commercial supplier of the micropost arrays used in this study. No other authors have any potential conflicts of interest with this work.

This work seeks to advance the field of traction force microscopy by substantially lowering technical and practical barriers to entry. These barriers come from two sides. First and foremost are the numerous non-trivial technical challenges that must be overcome to reproducibly manufacture and experimentally commission a micropost array. Second, is the similarly non-trivial need for a reliable semi-automated analysis of single cell forces &#8211; keeping in mind that a typical experiment may require the analysis of hundre...

Mechano-sensitive cell-based assays allow for investigating adherent cells, with a broad range of applications that reflect the central role that mechanics can play in cell biology. These applications often focus on the underlying mechanisms that drive subcellular processes or whole-cell behavior. On the one hand, external environmental factors such as extra cellular matrix composition or matrix stiffness can dramatically affect the mechanical and biological response of a cell.1 The same can be observed after use of many classes of pharmaceutically active compounds, the effects of which are often characterized using cell culture models.2 On the other hand genotypic properties, such as those caused by spontaneous or experimentally induced genetic mutations, can induce marked changes in cell phenotype that are associated with alterations in the cytoskeleton structure and function.3 These examples are just a few of the many possible topics for which mechanical phenotyping of cells is relevant, and all of these have been usefully investigated with micropost arrays.
At time of this writing, approximately 200 articles have been published describing cell-micropost interaction. These works discuss theoretical aspects of micropost deflection principles as well as practical instructions on their manufacture. The first article describing the interaction of cells and flexible micropost arrays was published by Tan and colleagues in 2003.4 In contrast to classic traction force microscopy (TFM) where continuous soft substrates are used to estimate nanonewton-scale cell contractility, Tan et al. described a method using multiple closely spaced vertical beams made of silicone elastomer. The main advantages of this technique emerge from two major features. First in order to change the cell-apparent substrate stiffness one only needs to change the micropost dimensions while keeping the substrate composition otherwise constant and thus avoiding differences in surface topology and chemistry. Second microposts act like individual springs that can be discretely analyzed with force and spatial resolutions on the order of individual focal adhesions and can reduce the analytical challenges that are inherent to analogous analysis by standard TFM.
Today the range of applications for micropost arrays greatly exceeds just the mapping of forces for a few single cells. For example, Akiyama reports the use of an isolated dorsal vessel tissue from a moth caterpillar as an actuator for a micropost array, in order to develop an insect muscle-powered autonomous micro-robot.5
However, most published applications of microposts have focused on studies of medical conditions like infection or cancer. For instance, micropost arrays have been used to study the force generation of bundled type IV pili of Neisseria gonorrhoea colonies that is associated with signal cascades enhancing infection.6 Others have used microposts to study breast cancer cells treated with pharmaceutical compounds targeting the cytoskeleton.7
Deflection of a micropost is often described using classical beam theory for a cantilever with an end load assuming the cell attaches only to the very tip of the micropost. Here the applied force F that causes a deflection &#948; depends on the micropost&#8217;s &#8220;bending stiffness&#8221; k and is calculated by:
<img alt="Equation 1" src="/files/ftp_upload/53350/53350eq1.jpg" /> (1)
with E, I, and L being the Young&#8217;s modulus, area moment of inertia and beam length respectively. However, results from this equation only give a general approximation of the forces at work since beam shearing and bending as well as substrate warping are not taken into account. Considering that microposts are typically made from soft materials like polydimethylsiloxane (PDMS)-based silicone rubber these factors need to be included. Schoen et al. demonstrated that there is such a correction factor based on the aspect ratio of the micropost (L/D) and the corresponding polymer&#8217;s Poisson ratio v.8 It is given by:
<img alt="Equation 2" src="/files/ftp_upload/53350/53350eq2.jpg" /> (2)
With Ttilt(v) being a tilting coefficient that includes fitting parameter a = 1.3 as can be found in the same article:
<img alt="Equation 3" src="/files/ftp_upload/53350/53350eq3.jpg" /> (3)
That means a micropost&#8217;s corrected stiffness kcorr is the product of the pure bending stiffness k=kbend and the correction factor corr given by:
<img alt="Equation 4" src="/files/ftp_upload/53350/53350eq4.jpg" /> (4)
Therefore, cell force calculations should be performed using the more refined variation of equation (1) now reading:
<img alt="Equation 5" src="/files/ftp_upload/53350/53350eq5.jpg" /> (5)
The impact of the correction becomes more obvious as soon as typical values for micropost dimensions are used. For example, a 15-micron long micropost with a circular cross section and a diameter of 5 &#181;m made of PDMS-based silicone rubber leads to a correction factor of 0.77 and therefore an uncorrected calculation would overestimate the exerted cell forces by 23%. This becomes even more severe for microposts with smaller aspect ratios.
Traditionally, micropost image analysis has also been based on idealized beam bending theory. In 2005 the group that pioneered the use of micropost arrays published an image analysis software suited for micropost analysis.9 The software requires a software license and the user must take three images for each position; one each from the micropost&#8217;s top and bottom planes in transmission mode and another one in fluorescence mode with the stained cell. After comparing the top and bottom positions for each micropost the software determines a force vector field and calculates related parameters like force per post. Other software packages exist and their analysis principles are briefly mentioned in the corresponding articles that describe them, but these analytical software packages are generally not publicly available.10,11
The micropost arrays designed for mapping cell forces can be classified as either being in an orthogonal micropost layout or a hexagonal one, the latter of which have the advantage of equidistant gaps between all neighbor microposts. Typical microposts have a circular cross section and their dimensions range from 1.0 &#181;m to 10&#160;&#181;m in diameter and 2 to 50 &#181;m in length. 4 However, microposts with elliptic or square cross section have also been reported.12,13
The use of PDMS-based silicone mixtures as micropost material allows for adding nanoparticles into the mixture. For example adding cobalt nano-rods enables a magnetic activation of the micropost and thus gives another degree of freedom to potential experimental designs.14 Most groups produce their micropost arrays on flat rigid substrates like cover glass or inside a Petri dish. However, Mann and co-workers recently reported a micropost array formed on a stretchable membrane.15 This allows the application of cell stretching forces to adherent cells while studying live-cell subcellular dynamic responses in terms of cell contractility.
The widely employed and most established process for making micropost arrays is based on soft lithography as described in the insightful protocols of Sniadecki and colleagues.16-18 In short standard cleanroom processes are used to generate the microstructures on top of a silicon wafer using SU8 photoresist. This is followed by a copying process wherein the silicone rubber is cast over the structures transferring them into molds. In a second step these molds are used to replicate the initial microstructure using silicone rubber on top of a chosen substrate. However despite the large and growing number of publications related to their application, establishing a manufacturing process for microposts takes considerable amount of time even for micro-engineering experts; there are many process steps that require optimization and adaptation to the specific lab environment and micropost layout to yield an acceptable quality level.
Commercial micropost arrays are now available in a ready-to-use (&#8220;off-the-shelf&#8221;) format with a consistently high quality. As such they are an alternative to the complex and lengthy manufacturing process required for on-site production. In this paper a commercially available micropost array was used for mapping cellular forces using a single bright-field microscopy image. More importantly this article describes and documents a fully-functional open-source software named MechProfiler, which is available for download as supplementary material to this manuscript. An actively maintained version of the software can also be found at http://www.orthobiomech.ethz.ch.
The combination of an &#8220;off-the-shelf&#8221; assay and a compatible open-source analysis software markedly lowers the entry hurdle to achieve accurate TFM experiments. Researchers without access to either clean room facilities or software development expertise can analyze cellular forces successfully. It enables a user to focus on the mechanosensitivity assay output rather than the technology itself, and makes traction force measurements available to a broader community. Furthermore, this is an important step to pave the way towards fully automatic screening of micropost arrays.
The MechProfiler analysis software processes images in file format tiff, png, bmp and jpg. The images can be taken using fluorescence, phase contrast or bright-field light microscopy. The standalone program runs together with the free Matlab Compiler Runtime (available at: Figure 12) and underlying algorithms allow for streamlined image processing, which enables the user to process images with single or multiple cells in about 1 min. Further, these cells may either be living or &#8220;fixed&#8221;.
The MechProfiler software is able to greatly increase data analysis throughput by relying on reproducibility of quality commercial micropost arrays, more specifically, the default &#8220;non-deflected&#8221; position of each post in the array can be presumed against an ideal grid (manufacturing deviations for the grid in the arrays used for this study were less than 100 nm).
In short one opens a selection of image files for analysis, crops them to the region of interest, defines the posts covered by cells or which need to be discarded, determines the post positions, calculates the deflections/forces against the ideal grid, and finally saves all cell-specific data with a possibility for export, including to a standard office spreadsheet.

<table><tbody><tr><td>T25 cell culture flasks</td><td>Nunc</td><td>156367</td><td></td></tr><tr><td>1x PBS-buffer</td><td>Sigma</td><td>D8537</td><td></td></tr><tr><td>0.5% Trypsin-EDTA</td><td>Life Technologies</td><td>15400054</td><td></td></tr><tr><td>Medium DMEM/F12</td><td>Sigma</td><td>D8437</td><td></td></tr><tr><td>FBS South America</td><td>Life Technologies</td><td>10270106</td><td></td></tr><tr><td>Penicillin-Streptomycin 100x</td><td>Sigma</td><td>P4333</td><td></td></tr><tr><td>15 ml centrifuge vials</td><td>Sarstedt</td><td>62.554.502&amp;nbsp;</td><td></td></tr><tr><td>Micropost array pre-coated with Collagen I/Fibronectin</td><td>MicroDuits</td><td>MPA-col1/FN</td><td>Micropost dimensions: &amp;Oslash;=6.4&amp;#160;&amp;micro;m, l=18.2 &amp;micro;m; grid=13 &amp;micro;m, k&lt;sub&gt;corr&lt;/sub&gt;=2.87&amp;#160;nN/&amp;micro;m</td></tr><tr><td>Ethanol abs p.A.</td><td>Merck</td><td>100.983</td><td></td></tr><tr><td>12-well plate</td><td>Nunc</td><td>150628</td><td></td></tr><tr><td>Formalin solution, neutral buffered 10%</td><td>Sigma</td><td>HT5011</td><td></td></tr><tr><td>Brilliant Blue G-250</td><td>Sigma</td><td>27815</td><td>Coomassie blue</td></tr><tr><td>Methanol ACS p.A.</td><td>Merck</td><td>1.06009</td><td></td></tr><tr><td>Acetic acid</td><td>Sigma</td><td>695092</td><td></td></tr><tr><td>Glass bottom dish</td><td>WillCo Wells BV</td><td>GWSb-3522</td><td>35 mm diameter, aperture 22&amp;nbsp;mm</td></tr><tr><td>T-100 Eclipse</td><td>Nikon</td><td>n/a</td><td>Inverted microscope</td></tr><tr><td>D3-L3</td><td>Nikon</td><td>n/a</td><td>Camera controler</td></tr><tr><td>DS Fi2</td><td>Nikon</td><td></td><td>Camera</td></tr></tbody></table>

easy and accurate mechano-profiling on micropost arrays

Cell culture substrates with integrated flexible microposts enable a user to study the mechanical interactions between cells and their immediate surroundings. Particularly, cell-substrate interactions are the main interest. Today micropost arrays are a well-characterized and established method with a broad range of applications that have been published over the last decade. However, there seems to be a reservation among biologists to adapt the technique due to the lengthy and challenging process of micropost manufacture along with the lack of easily approachable software for analyzing images of cells interacting with microposts. 
The force read-out from microposts is surprisingly easy. A micropost acts like a spring with the cell ideally attached at its tip. Depending on size a cell applies force from its cytoskeleton through one or multiple focal adhesion points to the micropost, thus deflecting the micropost. The amount of deflection correlates directly to the applied force in direction and in magnitude. The number of microposts covered by a cell and the post deflection patterns are characteristic and allow determination of values like force per post and many biologically relevant parameters that allow &#8220;mechano-profiling&#8221; of cell phenotypes.
A convenient method for mechano-profiling is described here combining the first generation of ready-to-use commercially available microposts with an in-house developed software package that is now accessible to all researchers. As a demonstration of typical application, single images of bone cancer cells were taken in bright-field microscopy for mechano-profiling of cell line models of metastasis. This combination of commercial traction force sensors and open source software for analysis allows for the first time a rapid implementation of the micropost array technique into routine lab work done by non-expert users. Furthermore, a robust and streamlined analysis process enables a user to analyze a large number of micropost images in a highly time-efficient manner.

The main advantage of the described technique lies in its simplicity and potential for rapid and effective integration into routine lab work. The combination of high quality commercial sensor arrays paired with open-source software provides information about mechano-sensitivity that would otherwise requires access to cleanroom facilities and in-depth knowledge of image analysis and software development. Figure 1 illustrates the workflow of the presented method. It starts with preparing and seeding cells ...

Watch this Scientific Journal Video about Easy and Accurate Mechano-profiling on Micropost Arrays at JoVE.com

Easy and Accurate Mechano-profiling on Micropost Arrays

Described are protocols for quantifying mechanical interactions between adherent cells and microstructured substrates. These interactions are closely linked to essential cell behaviors including migration, proliferation, differentiation, and apoptosis. The protocols present an open-source image analysis software called MechProfiler, which enables determination of involved forces for each micropost.

Cell culture substrates with integrated flexible microposts enable a user to study the mechanical interactions between cells and their immediate ...

easy-and-accurate-mechano-profiling-on-micropost-arrays

Research

JoVE Journal

Bioengineering

11.1K Views.  Balgrist University Hospital. Described are protocols for quantifying mechanical interactions between adherent cells and microstructured substrates. These interactions are closely linked to essential cell behaviors including migration, proliferation, differentiation, and apoptosis. The protocols present an open-source image analysis software called MechProfiler, which enables determination of involved forces for each micropost. 

Video: Easy and Accurate Mechano-profiling on Micropost Arrays

Microfabricated Platforms for Mechanically Dynamic Cell Culture

The ability to systematically probe in vitro cellular response to combinations of mechanobiological stimuli for tissue engineering, drug discovery or fundamental cell biology studies is limited by current bioreactor technologies, which cannot simultaneously apply a variety of mechanical stimuli to cultured cells. In order to address this issue, we have developed a series of microfabricated platforms designed to screen for the effects of mechanical stimuli in a high-throughput format. In this protocol, we demonstrate the fabrication of a microactuator array of vertically displaced posts on which the technology is based, and further demonstrate how this base technology can be modified to conduct high-throughput mechanically dynamic cell culture in both two-dimensional and three-dimensional culture paradigms.

In this protocol, we demonstrate the fabrication of a microactuator array of vertically displaced posts on which the technology is based, and how this base technology can be modified to conduct high-throughput mechanically dynamic cell culture in both two-dimensional and three-dimensional culture paradigms.

The ability to systematically probe in vitro cellular response to combinations of mechanobiological stimuli for tissue engineering, drug discovery or ...

Polymer Microarrays for High Throughput Discovery of Biomaterials

The discovery of novel biomaterials that are optimized for a specific biological application is readily achieved using polymer microarrays, which allows a combinatorial library of materials to be screened in a parallel, high throughput format1. Herein is described the formation and characterization of a polymer microarray using an on-chip photopolymerization technique 2. This involves mixing monomers at varied ratios to produce a library of monomer solutions, transferring the solution to a glass slide format using a robotic printing device and curing with UV irradiation. This format is readily amenable to many biological assays, including stem cell attachment and proliferation, cell sorting and low bacterial adhesion, allowing the ready identification of 'hit' materials that fulfill a specific biological criterion3-5. Furthermore, the use of high throughput surface characterization (HTSC) allows the biological performance to be correlated with physio-chemical properties, hence elucidating the biological-material interaction6. HTSC makes use of water contact angle (WCA) measurements, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). In particular, ToF-SIMS provides a chemically rich analysis of the sample that can be used to correlate the cell response with a molecular moiety. In some cases, the biological performance can be predicted from the ToF-SIMS spectra, demonstrating the chemical dependence of a biological-material interaction, and informing the development of hit materials5,3.

A description of the formation of a polymer microarray using an on-chip photopolymerization technique. The high throughput surface characterization using atomic force microscopy, water contact angle measurements, X-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry and a cell attachment assay is also described.

The discovery of novel biomaterials that are optimized for a specific biological application is readily achieved using polymer microarrays, which allows a ...

Microfabricated Post-Array-Detectors (mPADs): an Approach to Isolate Mechanical Forces

In this video, we will present our approach to measure cellular traction forces using a microfabricated array of posts.  Traction forces are generated through myosin-actin interactions and play an important role in our physiology.  During development, they enable cells to move from one location to the next in order to form the early structures of tissue.  Traction forces help in the healing processes.  They are necessary for the proper closure of wounds or the migration and crawling of leukocytes through our body.  These same forces can be detrimental to our health in the case of cancer metastasis or vascular growth towards a tumor.  The most common method by which to study cells in vitro has been to use a glass or polystyrene dish.  However, the rigidity of the substrates makes it impossible to physically measure cell traction forces, and there are relatively few methods to study traction forces.  Our lab has developed a technique to overcome these limitations.  The method is based on a vertical array of flexible cantilevers, the stiffness and size scale of which are such that individual cells spread across many cantilevers and deflect them in the process.  The pillars we use are 3 &mu;m in diameter, 10 &mu;m tall, and are configured in a regular array with 9 &mu;m center-to-center spacing.  But these physical dimensions can be readily varied to accommodate a variety of studies.  We start with a silicon master, but the final posts are made out of silicone rubber called poly (dimethyl siloxane), or PDMS.  We can measure the deflections under a microscope and calculate the magnitude and direction of traction forces required to produce the observed deflections.  We call these substrates microfabricated post-array-detectors, or mPADs.  Here, we will show you how we fabricate and use the mPADs to assess modulations of cellular contractility.

Microfabricated Post-Array-Detectors mPADs: an Approach to Isolate Mechanical Forces

In this video, we demonstrate how to fabricate and utilize microfabricated post array detectors (mPADs) to assess modulations of cellular contractility.

In this video, we will present our approach to measure cellular traction forces using a microfabricated array of posts.  Traction forces are generated ...

Biology

Hollow Microneedle-based Sensor for Multiplexed Transdermal Electrochemical Sensing

The development of a minimally invasive multiplexed monitoring system for rapid analysis of biologically-relevant molecules could offer individuals suffering from chronic medical conditions facile assessment of their immediate physiological state. Furthermore, it could serve as a research tool for analysis of complex, multifactorial medical conditions. In order for such a multianalyte sensor to be realized, it must be minimally invasive, sampling of interstitial fluid must occur without pain or harm to the user, and analysis must be rapid as well as selective.
Initially developed for pain-free drug delivery, microneedles have been used to deliver vaccines and pharmacologic agents (e.g., insulin) through the skin.1-2 Since these devices access the interstitial space, microneedles that are integrated with microelectrodes can be used as transdermal electrochemical sensors. Selective detection of glucose, glutamate, lactate, hydrogen peroxide, and ascorbic acid has been demonstrated using integrated microneedle-electrode devices with carbon fibers, modified carbon pastes, and platinum-coated polymer microneedles serving as transducing elements.3-7,8
This microneedle sensor technology has enabled a novel and sophisticated analytical approach for in situ and simultaneous detection of multiple analytes. Multiplexing offers the possibility of monitoring complex microenvironments, which are otherwise difficult to characterize in a rapid and minimally invasive manner. For example, this technology could be utilized for simultaneous monitoring of extracellular levels of, glucose, lactate and pH,9 which are important metabolic indicators of disease states7,10-14 (e.g., cancer proliferation) and exercise-induced acidosis.15

This article details the construction of a multiplexed microneedle-based sensor. The device is being developed for in situ sampling and electrochemical analysis of multiple analytes in a rapid and selective manner. We envision clinical medicine and biomedical research uses for these microneedle-based sensors.

The development of a minimally invasive multiplexed monitoring system for rapid analysis of biologically-relevant molecules could offer individuals ...

High Resolution Physical Characterization of Single Metallic Nanoparticles

Individual molecules can be detected and characterized by measuring the degree by which they reduce the ionic current flowing through a single nanometer-scale pore. The signal is characteristic of the molecule&#39;s physicochemical properties and its interactions with the pore. We demonstrate that the nanopore formed by the bacterial protein exotoxin Staphylococcus aureus alpha hemolysin (&#945;HL) can detect polyoxometalates (POMs, anionic metal oxygen clusters), at the single molecule limit. Moreover, multiple degradation products of 12-phosphotungstic acid POM (PTA, H3PW12O40) in solution are simultaneously measured. The single molecule sensitivity of the nanopore method allows for POMs to be characterized at significantly lower concentrations than required for nuclear magnetic resonance (NMR) spectroscopy. This technique could serve as a new tool for chemists to study the molecular properties of polyoxometalates or other metallic clusters, to better understand POM synthetic processes, and possibly improve their yield. Hypothetically, the location of a given atom, or the rotation of a fragment in the molecule, and the metal oxidation state could be investigated with this method. In addition, this new technique has the advantage of allowing the real-time monitoring of molecules in solution.&#160;

Here, we present a protocol to detect discrete metal oxygen clusters, polyoxometalates (POMs), at the single molecule limit using a biological nanopore-based electronic platform. The method provides a complementary approach to traditional analytical chemistry tools used in the study of these molecules.

Individual molecules can be detected and characterized by measuring the degree by which they reduce the ionic current flowing through a single ...

Chemistry

Polymeric Microneedle Array Fabrication by Photolithography

This manuscript describes the fabrication of polymeric microneedle (MN) arrays by photolithography. It involves a simple mold-free process by using a photomask consisting of embedded micro-lenses. Embedded micro-lenses were found to influence MN geometry (sharpness). Robust MN arrays with tip diameters ranging between 41.5 &#181;m &#177; 8.4 &#181;m and 71.6 &#181;m &#177; 13.7 &#181;m, with two different lengths (1,336 &#181;m &#177; 193 &#181;m and 957 &#181;m &#177; 171 &#181;m) were fabricated. These MN arrays may provide potential applications in delivery of low molecular and macromolecular therapeutic agents through skin.

Here, we present a protocol describing a mold-free fabrication process of the polymeric microneedles by photolithography.

This manuscript describes the fabrication of polymeric microneedle (MN) arrays by photolithography. It involves a simple mold-free process by using a ...

A Paired Bead and Magnet Array for Molding Microwells with Variable Concave Geometries

A spheroid culture is a useful tool for understanding cellular behavior in that it provides an in vivo-like three-dimensional environment. Various spheroid production methods such as non-adhesive surfaces, spinner flasks, hanging drops, and microwells have been used in studies of cell-to-cell interaction, immune-activation, drug screening, stem cell differentiation, and organoid generation. Among these methods, microwells with a three-dimensional concave geometry have gained the attention of scientists and engineers, given their advantages of uniform-sized spheroid generation and the ease with which the responses of individual spheroids can be monitored. Even though cost-effective methods such as the use of flexible membranes and ice lithography have been proposed, these techniques incur serious drawbacks such as difficulty in controlling the pattern sizes, achievement of high aspect ratios, and production of larger areas of microwells. To overcome these problems, we propose a robust method for fabricating concave microwells without the need for complex high-cost facilities. This method utilizes a 30 x 30 through-hole array, several hundred micrometer-order steel beads, and magnetic force to fabricate 900 microwells in a 3 cm x 3 cm polydimethylsiloxane (PDMS) substrate. To demonstrate the applicability of our method to cell biological applications, we cultured adipose stem cells for 3 days and successfully produced spheroids using our microwell platform. In addition, we performed a magnetostatic simulation to investigate the mechanism, whereby magnetic force was used to trap the steel beads in the through-holes. We believe that the proposed microwell fabrication method could be applied to many spheroid-based cellular studies such as drug screening, tissue regeneration, stem cell differentiation, and cancer metastasis.

This manuscript introduces a robust method of fabricating concave microwells without the need for complex high-cost facilities. Using magnetic force, steel beads, and a through-hole array, several hundred microwells were formed in a 3 cm x 3 cm polydimethylsiloxane (PDMS) substrate.

A spheroid culture is a useful tool for understanding cellular behavior in that it provides an in vivo-like three-dimensional environment. Various ...

Parallel Active Cantilever Arrays in AFMS to Enable High-Throughput Inspections

Active Probe Atomic Force Microscopy with Quattro-Parallel Cantilever Arrays for High-Throughput Large-Scale Sample Inspection

An Atomic Force Microscope&#160;(AFM) is&#160;a powerful and versatile tool for nanoscale surface studies to capture 3D topography images of samples. However, due to their limited imaging throughput, AFMs have not been widely adopted for large-scale inspection purposes. Researchers have developed high-speed AFM systems to record dynamic process videos in chemical and biological reactions at tens of frames per second, at the cost of a small imaging area of up to several square micrometers. In contrast, inspecting large-scale nanofabricated structures, such as semiconductor wafers, requires nanoscale spatial resolution imaging of a static sample over hundreds of square centimeters with high productivity. Conventional AFMs use a single passive cantilever probe with an optical beam deflection system, which can only collect one pixel at a time during AFM imaging, resulting in low imaging throughput. This work utilizes an array of active cantilevers with embedded piezoresistive sensors and thermomechanical actuators, which allows simultaneous multi-cantilever operation in parallel operation for increased imaging throughput. When combined with large-range nano-positioners and proper control algorithms, each cantilever can be individually controlled to capture multiple AFM images. With data-driven post-processing algorithms, the images can be stitched together, and defect detection can be performed by comparing them to the desired geometry. This paper introduces principles of the custom AFM using the active cantilever arrays, followed by a discussion on practical experiment considerations for inspection applications. Selected example images of silicon calibration grating, highly-oriented pyrolytic graphite, and extreme ultraviolet lithography masks are captured using an array of four active cantilevers (&#34;Quattro&#34;) with a 125 &#181;m tip separation distance. With more engineering integration, this high-throughput, large-scale imaging tool can provide 3D metrological data for extreme ultraviolet (EUV) masks, chemical mechanical planarization (CMP) inspection, failure analysis, displays, thin-film step measurements, roughness measurement dies, and laser-engraved dry gas seal grooves.

Author Spotlight: Introduction to Active Probe Atomic Force Microscopy with Quattro-Parallel Cantilever Arrays

Large-scale sample inspection with nanoscale resolution has a wide range of applications, especially for nanofabricated semiconductor wafers. Atomic force microscopes can be a great tool for this purpose, but are limited by their imaging speed. This work utilizes parallel active cantilever arrays in AFMs to enable high-throughput and large-scale inspections.

An Atomic Force Microscope&#160;(AFM) is&#160;a powerful and versatile tool for nanoscale surface studies to capture 3D topography images of samples. ...

Engineering

Fabrication of a Multiplexed Artificial Cellular MicroEnvironment Array

Cellular microenvironments consist of a variety of cues, such as growth factors, extracellular matrices, and intercellular interactions. These cues are well orchestrated and are crucial in regulating cell functions in a living system. Although a number of researchers have attempted to investigate the correlation between environmental factors and desired cellular functions, much remains unknown. This is largely due to the lack of a proper methodology to mimic such environmental cues in vitro, and simultaneously test different environmental cues on cells. Here, we report an integrated platform of microfluidic channels and a nanofiber array, followed by high-content single-cell analysis, to examine stem cell phenotypes altered by distinct environmental factors. To demonstrate the application of this platform, this study focuses on the phenotypes of self-renewing human pluripotent stem cells (hPSCs). Here, we present the preparation procedures for a nanofiber array and the microfluidic structure in the fabrication of a Multiplexed Artificial Cellular MicroEnvironment (MACME) array. Moreover, overall steps of the single-cell profiling, cell staining with multiple fluorescent markers, multiple fluorescence imaging, and statistical analyses, are described.

This article describes the detailed methodology to prepare a Multiplexed Artificial Cellular MicroEnvironment (MACME) array for high-throughput manipulation of physical and chemical cues mimicking in vivo cellular microenvironments and to identify the optimal cellular environment for human pluripotent stem cells (hPSCs) with single-cell profiling.

Cellular microenvironments consist of a variety of cues, such as growth factors, extracellular matrices, and intercellular interactions. These cues are ...

Fabrication and Use of MicroEnvironment microArrays (MEArrays)

The interactions between cells and their surrounding microenvironment have functional consequences for cellular behaviour. On the single cell level, distinct microenvironments can impose differentiation, migration, and proliferation phenotypes, and on the tissue level the microenvironment processes as complex as morphogenesis and tumorigenesis1. Not only do the cell and molecular contents of microenvironments impact the cells within, but so do the elasticity2 and geometry3 of the tissue. Defined as the sum total of cell-cell, -ECM, and -soluble factor interactions, in addition to physical characteristics, the microenvironment is complex. The phenotypes of cells within a tissue are partially due to their genomic content and partially due to the combinatorial interactions with the microenviroment. A major challenge is to link specific combinations of microenvironmental components with distinctive behaviours.
Here, we present the microenvironment microarray (MEArray) platform for cell-based functional screening of interactions with combinatorial microenvironments4. The method allows for simultaneous control of the molecular composition and the elastic modulus, and combines the use of widely available microarray and micropatterning technologies. MEArray screens require as few as 10,000 cells per array, which facilitates functional studies of rare cell types such as adult progenitor cells. A limitation of the technology is that entire tissue microenvironments cannot be completely recapitulated on MEArrays. However, comparison of responses in the same cell type to numerous related microenvironments, for instance pairwise combinations of ECM proteins that characterize a given tissue, will provide insights into how microenvironmental components elicit tissue-specific functional phenotypes.
MEArrays can be printed using a wide variety of recombinant growth factors, cytokines, and purified ECM proteins, and combinations thereof. The platform is limited only by the availability of specific reagents. MEArrays are amenable to time-lapsed analysis, but most often are used for end point analyses of cellular functions that are measureable with fluorescent probes. For instance, DNA synthesis, apoptosis, acquisition of differentiated states, or production of specific gene products are commonly measured. Briefly, the basic flow of an MEArray experiment is to prepare slides coated with printing substrata and to prepare the master plate of proteins that are to be printed. Then the arrays are printed with a microarray robot, cells are allowed to attach, grow in culture, and then are chemically fixed upon reaching the experimental endpoint. Fluorescent or colorimetric assays, imaged with traditional microscopes or microarray scanners, are used to reveal relevant molecular and cellular phenotypes (Figure 1).

Fabrication and Use of MicroEnvironment microArrays MEArrays

A combinatorial functional screening method for gaining insights into the impacts of the molecular composition of microenvironments on cellular functions is described. The method takes advantage of existing microarray-based technologies to generate arrays of defined combinatorial microenvironments that support cell adhesion and functional analysis.

The interactions between cells and their surrounding microenvironment have functional consequences for cellular behaviour. On the single cell level, ...