The authors acknowledge the use of the surface analysis laboratory at Johns Hopkins, funded as part of the Materials Research Science and Engineering Center through the National Science Foundation. LED is an IGERT trainee and a National Science Foundation Graduate Fellow. This research was partially supported by NIH grant U54CA143868.

1. Standard Photolithography for Micropatterned Stamp Fabrication
<ol>
<li>Rinse a new silicon wafer with ethanol and dry with stream of air. Use forceps to handle wafer and prevent surface defects during the entire process.</li>
<li>Transfer wafer to spin coater and cover wafer surface with SU-2025 negative photoresist. Cover at least 80% of wafer with photoresist. Spin coat for 10 seconds at 600rpm, followed by 30 seconds at 3000rpm. Due to the photosensitivity of the photoresist, turn off room lights from this point forward.</li>
<li>Transfer photoresist coated silicon wafer to hot plate for "soft-bake" at 95&deg;C for 3 minutes. Remove from hot plate and allow 1 minute to cool.</li>
<li>Place a pre-fabricated mask with the desired pattern on top of the photoresist-covered silicon wafer and expose to ultraviolet (UV) irradiation (350-450 nm) for 20 seconds.</li>
<li>Transfer silicon wafer to hot plate for "hard-bake" at 110&deg;C for 6 minutes.</li>
<li>Turn on lights and remove wafer from hot plate. Distinct patterns should be visible at this point.</li>
<li>Carefully rinse silicon wafer with SU-8 photoresist developer. After 3 rinses with developer solution, rinse with ethanol. If any white residue is present, repeat rinse with photoresist developer solution, or simply submerge the wafer in developer solution for 2 minutes and proceed again with ethanol rinse. Wash with water and air dry.</li>
<li>Mix polydimethylsiloxane (PDMS) elastomer solution and curing agent in a 10:1 weight ratio. Centrifuge at 900rpm for 5 minutes to remove air bubbles.</li>
<li>Place patterned wafer in Petri dish and pour PDMS onto silicon wafer. If there are bubbles present, place in desicator and vacuum for a couple minutes until bubbles disappear.</li>
<li>Cure overnight at room temperature (RT) to form a complementary elastomeric stamp. If PDMS is not completely cured after 12 hours, place in oven at 60&deg;C for 30 minutes.</li>
<li>Carefully remove PDMS from silicon wafer. Use a razor edge to cut stamp to desired size. Sonicate in ethanol for 15 minutes. Wafers can be utilized multiple times to create new elastomeric stamps.</li>
</ol>
2. HA Micropatterning
<ol>
<li>Plasma clean glass slides for 5 minutes. Place all slides into chamber and vacuum for 5 minutes. Then allow low flow of oxygen to enter chamber. Turn plasma cleaner on for 5 minutes. Remove from plasma cleaner and place in a Petri dish using forceps.</li>
<li>During plasma cleaning, sonicate PDMS stamps in ethanol for 15 minutes.</li>
<li>Prepare a fresh 3% v/v solution of 3-aminopropyltrimethoxysilane (APTMS) in 95% v/v ethanol in a 15 mL centrifuge tube. Allow to react for 5 minutes at RT to form a silanol.</li>
<li>Place PDMS stamp pattern-up on spin coater chuck and cover patterned surface with APTMS solution. Spincoat at 3500rpm for 30 seconds. Do not touch the stamp surface, only the sides of PDMS stamp.</li>
<li>Transfer APTMS solution to the plasma cleaned glass surfaces: set stamp facing down on one end of patterned side and gently glide pressing PDMS so it is completely in contact with glass surface for 1 minute.</li>
<li>Remove PDMS stamp gently, and allow patterned glass slide to incubate in RT for 30 minutes. Rinse patterned surfaces with ethanol and air dry. Sonicate PDMS stamp for 15 minutes to remove excess APTMS.</li>
<li>Heat surfaces in oven or on hot plate for 1 hour at 115&deg;C. Rinse with ethanol and dry with air.</li>
<li>Prepare fresh polyethylene glycol (PEG)-silane solution of 20% v/v 2-[methoxy(polyethyleneoxy)propyl] trimethoxysilane in toluene. This will serve as a non-adhesive region surrounding patterns.</li>
<li>Transfer patterned glass slide to a glass Petri dish and incubate in PEG-silane solution for 45 minutes at 75&deg;C on a hot plate. Rinse with toluene, water, and dry with air.</li>
<li>Sterilize for 1 hour using UV germicidal irradiation in a biological safety cabinet. Proceed in biological safety cabinet from this point forward to maintain sterility.</li>
<li>Prepare aqueous sterile HA solution. 
10mM of 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) 
5mM of N-hydroxysuccinimide 
50&mu;g/ mL fluorescein-labeled HA</li>
<li>Apply HA solution to the patterned glass substrates in sterile conditions and protected from light. Patterned substrates should be undisturbed for 16-24 hours.</li>
<li>Aspirate off HA solution, wash with phosphate-buffered saline (PBS), and cover surface with 1% bovine serum albumin (BSA) in PBS for 1 hour. The surface is now ready for cell culture.</li>
</ol>
3. Cell Culture on HA Micropatterned Surfaces
<ol>
<li>Expand MDA-MB-231 human breast cancer cells and LS174T colorectal carcinoma cells, according to the manufacturer's instructions.</li>
<li>Seed single cell suspensions of cancer cells with densities between 0.4 and 1x106 cancer cells per 18.75 cm2 glass surface area and onto HA immobilized surfaces. Incubate in humidified incubator (37 &deg;C) in atmospheres maintained with 5% CO2. Cell adhesion should occur within 24 hours and can be observed using inverted light microscope</li>
<li>Cell culture surfaces can be maintained up to 5 days in standard incubator conditions. Change media every other day. Cell morphology and growth can be observed using inverted light microscope. Additional cellular assays can be applied to analyze responses to the HA surface.</li>
</ol>
4. Representative Results:


The carbodiimide chemistry used to covalently immobilize HA to APTMS patterned glass slides is shown in Figure 1A. EDC is a zero-length crosslinking agent that reacts with HA carboxyl groups to form amine-reactive intermediates. As this intermediate is susceptible to hydrolysis, NHS is added to increase carbodiimide reaction efficiency. As HA solution interacts with APTMS micropatterns, a stable amide bond forms between HA intermediate and primary amine of ATPMS. An example of HA patterned surface visualized using a fluorescent microscope and an ImageJ fluorescence intensity analysis demonstrate the patterned immobilization of HA are shown (Figure 1B-C).
The HA micropatterned surfaces enable the study of cancer cell interactions with expgenous HA. Both MDA-MB-231 human breast and LS174t human colon cancer cell lines preferentially adhere to HA micropatterned regions (Figure 2). High resolution imaging using scanning electron microscopy can be used to analyze interactions of cultured cells with HA immobilized surfaces (Figure 3).
 <img src="/files/ftp_upload/2413/2413fig1.jpg" alt="Figure 1" /> 
Figure 1 HA micropatterned surfaces (A) Schematic describing the development of HA functional surfaces, (B) fluorescence image of fluorescein (green)-labeled HA micropatterned surface. (C) 3D pixel distribution map using ImageJ software demonstrating the discrete HA patterns. Scale bar = 100&mu;m. Modified from 9 with permission from Elsevier.
 <img src="/files/ftp_upload/2413/2413fig2.jpg" alt="Figure 2" /> 
Figure 2. Cancer cell adhesion on HA micropatterned surfaces. Both colon (A) and breast (B) carcinoma preferentially adhered onto HA patches with 24 hours of culture. Modified from 9 with permission from Elsevier.
 <img src="/files/ftp_upload/2413/2413fig3.jpg" alt="Figure 3" /> 
Figure 3. Cancer cell interaction with HA. (A) Scanning electron microscopy images of colon cancer cells (A) cultured on HA surfaces shown at low magnification (left) and high magnification (right; of squares on left) and of breast cancer cells (B) cultured on HA surfaces shown at low magnification (left) and high magnification (right; of squares on left).

<ol>
	<li>Toole, B. P., Wight, T. N., Tammi, M. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyaluronan-cell+interactions+in+cancer+and+vascular+disease.">Hyaluronan-cell interactions in cancer and vascular disease.</a> Journal of Biological Chemistry. 277, 4593-4596 (2002).</li><li>Hamilton, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Hyaluronan+Receptors+CD44+and+Rhamm+(CD168)+Form+Complexes+with+ERK1,2+That+Sustain+High+Basal+Motility+in+Breast+Cancer+Cells.">The Hyaluronan Receptors CD44 and Rhamm (CD168) Form Complexes with ERK1,2 That Sustain High Basal Motility in Breast Cancer Cells.</a> Journal of Biological Chemistry. 282, 16667-16680 (2007).</li><li>G&#246;tte, M., Yip, G. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heparanase,+Hyaluronan,+and+CD44+in+Cancers:+A+Breast+Carcinoma+Perspective.">Heparanase, Hyaluronan, and CD44 in Cancers: A Breast Carcinoma Perspective.</a> Cancer Research. 66, 10233-10237 (2006).</li><li>Lord, M. S., Pasqui, D., Barbucci, R., Milthorpe, B. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+adsorption+on+derivatives+of+hyaluronic+acid+and+subsequent+cellular+response.">Protein adsorption on derivatives of hyaluronic acid and subsequent cellular response.</a> Journal of Biomedical Materials Research. Part A 91, 635-646 (2009).</li><li>Barbucci, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modification+of+hyaluronic+acid+by+sulphate+groups+insertion+to+obtain+a+heparin-like+molecule.">Modification of hyaluronic acid by sulphate groups insertion to obtain a heparin-like molecule.</a> Gazz. Chim. Ital. 125, 169-180 (1995).</li><li>Morra, M., Cassinelli, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-fouling+properties+of+polysaccharide-coated+surfaces.">Non-fouling properties of polysaccharide-coated surfaces.</a> Journal of Biomaterials Science, Polymer Edition. 10, 1107-1124 (1999).</li><li>Khademhosseini, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Layer-by-layer+deposition+of+hyaluronic+acid+and+poly-L-lysine+for+patterned+cell+co-cultures.">Layer-by-layer deposition of hyaluronic acid and poly-L-lysine for patterned cell co-cultures.</a> Biomaterials. 25, 3583-3592 (2004).</li><li>Ibrahim, S., Joddar, B., Craps, M., Ramamurthi, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+surface-tethered+model+to+assess+size-specific+effects+of+hyaluronan+(HA)+on+endothelial+cells.">A surface-tethered model to assess size-specific effects of hyaluronan (HA) on endothelial cells.</a> Biomaterials. 28, 825-835 (2007).</li><li>Dickinson, L. E., Ho, C. C., Wang, G. M., Stebe, K. J., Gerecht, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+surfaces+for+high-resolution+analysis+of+cancer+cell+interactions+on+exogenous+hyaluronic+acid.">Functional surfaces for high-resolution analysis of cancer cell interactions on exogenous hyaluronic acid.</a> Biomaterials. 31, 5472-5478 (2010).</li><li>Gao, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyaluronan+oligosaccharides+promote+excisional+wound+healing+through+enhanced+angiogenesis.">Hyaluronan oligosaccharides promote excisional wound healing through enhanced angiogenesis.</a> Matrix Biology. 29, 107-116 (2010).</li><li>Slevin, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyaluronan-mediated+angiogenesis+in+vascular+disease:+Uncovering+RHAMM+and+CD44+receptor+signaling+pathways.">Hyaluronan-mediated angiogenesis in vascular disease: Uncovering RHAMM and CD44 receptor signaling pathways.</a> Matrix Biology. 26, 58-68 (2007).</li></ol>

Video schematic figure reproduced with permission; Copyright Wiley-VCH Verlag GmbH &amp; Co. KGaA. Dickinson LE, Kusuma S, Gerecht S. Reconstructing the differentiation niche of embryonic stem cells using biomaterials. Macromol. Biosci. 2010; Oct 21. [Epub ahead of print].

The HA micropatterning method presented allows the study of cell interactions with exogenous HA. HA is known to play a key role in cancer progression 1 however there have been limited studies investigating the interaction of cancer cells on two dimensional HA patterned surfaces. A controllable study on exogenous HA micropatterns allows high-resolution visualization of cancer cell adhesion, growth, and migration and may elucidate further fundamentals of cancer.
By combining carbod...

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		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>SU-2025 photoresist</td>
<td>&nbsp;</td>
<td>MicroChem Corp.</td>
<td>Y111069</td>
<td>&nbsp;</td>
<tr>
<td>SU-8 developer</td>
<td>&nbsp;</td>
<td>MicroChem Corp.</td>
<td>Y020100</td>
<td>&nbsp;</td>
<tr>
<td>Sylgard 184</td>
<td>&nbsp;</td>
<td>Dow Corning</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>3-aminopropyltrimethoxysilane (APTMS)</td>
<td>&nbsp;</td>
<td>Sigma-Aldrich</td>
<td>281778</td>
<td>&nbsp;</td>
<tr>
<td>2- [methoxy(polyethyleneoxy) propyl] trimethoxysilane (Peg-silane)</td>
<td>&nbsp;</td>
<td>Gelest Inc</td>
<td>SIM6492.7</td>
<td>&nbsp;</td>
<tr>
<td>1-Ethyl-3- (3-dimethylaminopropyl) carbodiimide</td>
<td>&nbsp;</td>
<td>Thermo Scientific</td>
<td>22980</td>
<td>&nbsp;</td>
<tr>
<td>N-hydroxysuccinimide (NHS)</td>
<td>&nbsp;</td>
<td>Thermo Scientific</td>
<td>24500</td>
<td>&nbsp;</td>
<tr>
<td>Fluorescein labeled hyaluronic acid (FL-HA)</td>
<td>&nbsp;</td>
<td>Sigma-Aldrick</td>
<td>F1177</td>
<td>Reconstitute with 10ml of DI water </td>
</tr>
<tr>
<td>MDA-MB-231 breast carcinoma cells</td>
<td>&nbsp;</td>
<td>ATCC</td>
<td>HTB-26</td>
<td>&nbsp;</td>
<tr>
<td>LS174t colon carcinoma cells</td>
<td>&nbsp;</td>
<td>ATCC</td>
<td>Cl-188</td>
<td>&nbsp;</td>		</tbody>
		</table>
		</div>

micropatterned surfaces to study hyaluronic acid interactions with cancer cells

Cancer invasion and progression involves a motile cell phenotype, which is under complex regulation by growth factors/cytokines and extracellular matrix (ECM) components within the tumor microenvironment. Hyaluronic acid (HA) is one stromal ECM component that is known to facilitate tumor progression by enhancing invasion, growth, and angiogenesis1. Interaction of HA with its cell surface receptor CD44 induces signaling events that promote tumor cell growth, survival, and migration, thereby increasing metastatic spread2-3. HA is an anionic, nonsulfated glycosaminoglycan composed of repeating units of D-glucuronic acid and D-N-acetylglucosamine. Due to the presence of carboxyl and hydroxyl groups on repeating disaccharide units, native HA is largely hydrophilic and amenable to chemical modifications that introduce sulfate groups for photoreative immobilization 4-5. Previous studies involving the immobilizations of HA onto surfaces utilize the bioresistant behavior of HA and its sulfated derivative to control cell adhesion onto surfaces6-7. In these studies cell adhesion preferentially occurs on non-HA patterned regions.
To analyze cellular interactions with exogenous HA, we have developed patterned functionalized surfaces that enable a controllable study and high-resolution visualization of cancer cell interactions with HA. We utilized microcontact printing (uCP) to define discrete patterned regions of HA on glass surfaces. A "tethering" approach that applies carbodiimide linking chemistry to immobilize HA was used 8. Glass surfaces were microcontact printed with an aminosilane and reacted with a HA solution of optimized ratios of EDC and NHS to enable HA immobilization in patterned arrays. Incorporating carbodiimide chemistry with mCP enabled the immobilization of HA to defined regions, creating surfaces suitable for in vitro applications. Both colon cancer cells and breast cancer cells implicitly interacted with the HA micropatterned surfaces. Cancer cell adhesion occurred within 24 hours with proliferation by 48 hours. Using HA micropatterned surfaces, we demonstrated that cancer cell adhesion occurs through the HA receptor CD44. Furthermore, HA patterned surfaces were compatible with scanning electron microscopy (SEM) and allowed high resolution imaging of cancer cell adhesive protrusions and spreading on HA patterns to analyze cancer cell motility on exogenous HA.

Watch this Scientific Journal Video about Micropatterned Surfaces to Study Hyaluronic Acid Interactions with Cancer Cells at JoVE.com

Micropatterned Surfaces to Study Hyaluronic Acid Interactions with Cancer Cells

A novel approach that allows the high-resolution analysis of cancer cell interactions with exogenous hyaluronic acid (HA) is described. Patterned surfaces are fabricated by combining carbodiimide chemistry and microcontact printing.

Cancer invasion and progression involves a motile cell phenotype, which is under complex regulation by growth factors/cytokines and extracellular matrix ...

micropatterned-surfaces-to-study-hyaluronic-acid-interactions-with

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15.0K Views.  Johns Hopkins University. A novel approach that allows the high-resolution analysis of cancer cell interactions with exogenous hyaluronic acid (HA) is described. Patterned surfaces are fabricated by combining carbodiimide chemistry and microcontact printing.

Video: Micropatterned Surfaces to Study Hyaluronic Acid Interactions with Cancer Cells

Improved Visualization and Quantitative Analysis of Drug Effects Using Micropatterned Cells

To date, most HCA (High Content Analysis) studies are carried out with adherent cell lines grown on a homogenous substrate in tissue-culture treated micro-plates. Under these conditions, cells spread and divide in all directions resulting in an inherent variability in cell shape, morphology and behavior. The high cell-to-cell variance of the overall population impedes the success of HCA, especially for drug development. The ability of micropatterns to normalize the shape and internal polarity of every individual cell provides a tremendous opportunity for solving this critical bottleneck 1-2.
To facilitate access and use of the micropatterning technology, CYTOO has developed a range of ready to use micropatterns, available in coverslip and microwell formats. In this video article, we provide detailed protocols of all the procedures from cell seeding on CYTOOchip micropatterns, drug treatment, fixation and staining to automated acquisition, automated image processing and final data analysis. With this example, we illustrate how micropatterns can facilitate cell-based assays. Alterations of the cell cytoskeleton are difficult to quantify in cells cultured on homogenous substrates, but culturing cells on micropatterns results in a reproducible organization of the actin meshwork due to systematic positioning of the cell adhesion contacts in every cell. Such normalization of the intracellular architecture allows quantification of even small effects on the actin cytoskeleton as demonstrated in these set of protocols using blebbistatin, an inhibitor of the actin-myosin interaction.

Adhesive micropatterns that normalize cellular architecture can be used to increase sensitivity in the detection of drug effects, improve reproducibility and simplify automated image acquisition and analysis. Such technology will benefit drug/siRNA screening assays, performed on conventional cell culture supports and consequently suffering from excessive cell-to-cell variability.

To date, most HCA (High Content Analysis) studies are carried out with adherent cell lines grown on a homogenous substrate in tissue-culture treated ...

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic valve leaflets are composed of interstitial cells suspended within an extracellular matrix (ECM) and are lined with an endothelial cell monolayer. The valve withstands a harsh, dynamic environment and is constantly exposed to shear, flexion, tension, and compression. Research has shown calcific lesions in diseased valves occur in areas of high mechanical stress as a result of endothelial disruption or interstitial matrix damage1-3. Hence, it is not surprising that epidemiological studies have shown high blood pressure to be a leading risk factor in the onset of aortic valve disease4. 
The only treatment option currently available for valve disease is surgical replacement of the diseased valve with a bioprosthetic or mechanical valve5. Improved understanding of valve biology in response to physical stresses would help elucidate the mechanisms of valve pathogenesis. In turn, this could help in the development of non-invasive therapies such as pharmaceutical intervention or prevention. Several bioreactors have been previously developed to study the mechanobiology of native or engineered heart valves6-9. Pulsatile bioreactors have also been developed to study a range of tissues including cartilage10, bone11 and bladder12. The aim of this work was to develop a cyclic pressure system that could be used to elucidate the biological response of aortic valve leaflets to increased pressure loads. 
The system consisted of an acrylic chamber in which to place samples and produce cyclic pressure, viton diaphragm solenoid valves to control the timing of the pressure cycle, and a computer to control electrical devices. The pressure was monitored using a pressure transducer, and the signal was conditioned using a load cell conditioner. A LabVIEW program regulated the pressure using an analog device to pump compressed air into the system at the appropriate rate. The system mimicked the dynamic transvalvular pressure levels associated with the aortic valve; a saw tooth wave produced a gradual increase in pressure, typical of the transvalvular pressure gradient that is present across the valve during diastole, followed by a sharp pressure drop depicting valve opening in systole. The LabVIEW program allowed users to control the magnitude and frequency of cyclic pressure. The system was able to subject tissue samples to physiological and pathological pressure conditions. This device can be used to increase our understanding of how heart valves respond to changes in the local mechanical environment.

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

A cyclic pressure bioreactor capable of subjecting heart valve tissue to physiological and pathological pressure conditions has been designed. A LabVIEW program allows users to control pressure magnitude, amplitude and frequency. This device can be used to study the mechanobiology of heart valve tissue or isolated cells.

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic ...

Endothelialized Microfluidics for Studying Microvascular Interactions in Hematologic Diseases

Advances in microfabrication techniques have enabled the production of inexpensive and reproducible microfluidic systems for conducting biological and biochemical experiments at the micro- and nanoscales 1,2. In addition, microfluidics have also been specifically used to quantitatively analyze hematologic and microvascular processes, because of their ability to easily control the dynamic fluidic environment and biological conditions3-6. As such, researchers have more recently used microfluidic systems to study blood cell deformability, blood cell aggregation, microvascular blood flow, and blood cell-endothelial cell interactions6-13.However, these microfluidic systems either did not include cultured endothelial cells or were larger than the sizescale relevant to microvascular pathologic processes. A microfluidic platform with cultured endothelial cells that accurately recapitulates the cellular, physical, and hemodynamic environment of the microcirculation is needed to further our understanding of the underlying biophysical pathophysiology of hematologic diseases that involve the microvasculature.
Here, we report a method to create an "endothelialized" in vitro model of the microvasculature, using a simple, single mask microfabrication process in conjunction with standard endothelial cell culture techniques, to study pathologic biophysical microvascular interactions that occur in hematologic disease. This "microvasculature-on-a-chip" provides the researcher with a robust assay that tightly controls biological as well as biophysical conditions and is operated using a standard syringe pump and brightfield/fluorescence microscopy. Parameters such as microcirculatory hemodynamic conditions, endothelial cell type, blood cell type(s) and concentration(s), drug/inhibitory concentration etc., can all be easily controlled. As such, our microsystem provides a method to quantitatively investigate disease processes in which microvascular flow is impaired due to alterations in cell adhesion, aggregation, and deformability, a capability unavailable with existing assays.

A method to culture an endothelial cell monolayer throughout the entire inner 3D surface of a microfluidic device with microvascular-sized channels (&lt;30 &mu;m) is described. This in vitro microvasculature model enables the study of biophysical interactions between blood cells, endothelial cells, and soluble factors in hematologic diseases.

Advances in  microfabrication techniques have enabled the production of inexpensive and  reproducible microfluidic systems for conducting biological and ...

Stretching Micropatterned Cells on a PDMS Membrane

Mechanical forces exerted on cells and/or tissues play a major role in numerous processes. We have developed a device to stretch cells plated on a PolyDiMethylSiloxane (PDMS) membrane, compatible with imaging. This technique is reproducible and versatile. The PDMS membrane can be micropatterned in order to confine cells or tissues to a specific geometry. The first step is to print micropatterns onto the PDMS membrane with a deep UV technique. The PDMS membrane is then mounted on a mechanical stretcher. A chamber is bound on top of the membrane with biocompatible grease to allow gliding during the stretch. The cells are seeded and allowed to spread for several hours on the micropatterns. The sample can be stretched and unstretched multiple times with the use of a micrometric screw. It takes less than a minute to apply the stretch to its full extent (around 30%). The technique presented here does not include a motorized device, which is necessary for applying repeated stretch cycles quickly and/or computer controlled stretching, but this can be implemented. Stretching of cells or tissue can be of interest for questions related to cell forces, cell response to mechanical stress or tissue morphogenesis. This video presentation will show how to avoid typical problems that might arise when doing this type of seemingly simple experiment.

This manuscript presents a technique to apply or release forces on adherent cells or tissues using unidirectional stretching.

Mechanical forces exerted on cells and/or tissues  play a major role in numerous processes. We have developed a device to stretch  cells plated on a ...

Tissue Engineering of Tumor Stromal Microenvironment with Application to Cancer Cell Invasion

3D organotypic cultures of epithelial cells on a matrix embedded with mesenchymal cells are widely used to study epithelial cell differentiation and invasion. Rat tail type I collagen and/or matrix derived from Engelbreth-Holm-Swarm mouse sarcoma cells have been traditionally employed as the substrates to model the matrix or stromal microenvironment into which mesenchymal cells (usually fibroblasts) are populated. Although experiments using such matrices are very informative, it can be argued that due to an overriding presence of a single protein (such as in type I Collagen) or a high content of basement membrane components and growth factors (such as in matrix derived from mouse sarcoma cells), these substrates do not best reflect the contribution to matrix composition made by the stromal cells themselves. To study native matrices produced by primary dermal fibroblasts isolated from patients with a tumor prone, genetic blistering disorder (recessive dystrophic epidermolysis bullosa), we have adapted an existing native matrix protocol to study tumor cell invasion. Fibroblasts are induced to produce their own matrix over a prolonged period in culture. This native matrix is then detached from the culture dish and epithelial cells are seeded onto it before the entire coculture is raised to the air-liquid interface. Cellular differentiation and/or invasion can then be assessed over time. This technique provides the ability to assess epithelial-mesenchymal cell interactions in a 3D setting without the need for a synthetic or foreign matrix with the only disadvantage being the prolonged period of time required to produce the native matrix. Here we describe the application of this technique to assess the ability of a single molecule expressed by fibroblasts, type VII collagen, to inhibit tumor cell invasion.

Tissue engineered fibroblast-derived native matrix is an emerging tool to generate a stromal substrate which supports epithelial cell proliferation and differentiation. Here a protocol applying this methodology to assess the impact of different stromal cell types on tumor cell biology is presented.

3D organotypic cultures of epithelial cells on a matrix embedded with mesenchymal cells are widely used to study epithelial cell differentiation and ...

Gene Transfection toward Spheroid Cells on Micropatterned Culture Plates for Genetically-modified Cell Transplantation

To improve the therapeutic effectiveness of cell transplantation, a transplantation system of genetically modified, injectable spheroids was developed. The cell spheroids are prepared in a culture system on micropatterned plates coated with a thermosensitive polymer. A number of spheroids are formed on the plates, corresponding to the cell adhesion areas of 100 &#181;m diameter that are regularly arrayed in a two-dimensional manner, surrounded by non-adhesive areas that are coated by a polyethylene glycol (PEG) matrix. The spheroids can be easily recovered as a liquid suspension by lowering the temperature of the plates, and their structure is well maintained by passing them through injection needles with a sufficiently large caliber (over 27 G). Genetic modification is achieved by gene transfection using the original non-viral gene carrier, polyplex nanomicelle, which is capable of introducing genes into cells without disrupting the spheroid structure. For primary hepatocyte spheroids transfected with a luciferase-expressing gene, the luciferase is sustainably obtained in transplanted animals, along with preserved hepatocyte function, as indicated by albumin expression. This system can be applied to a variety of cell types including mesenchymal stem cells.

This protocol describes a cell transplantation system using genetically modified, injectable spheroids. Cell spheroids are cultured on micropatterned culture plates and recovered after gene introduction using polyplex nanomicelles. This system facilitates prolonged transgene expression from the transplanted cells in host animals while maintaining the innate function of the cells.

To improve the therapeutic effectiveness of cell transplantation, a transplantation system of genetically modified, injectable spheroids was developed. ...

Preparation of Thermoresponsive Nanostructured Surfaces for Tissue Engineering

Thermoresponsive poly(N-isopropylacrylamide) (PIPAAm)-immobilized surfaces for controlling cell adhesion and detachment were fabricated by the Langmuir-Schaefer method. Amphiphilic block copolymers composed of polystyrene and PIPAAm (St-IPAAms) were synthesized by reversible addition-fragmentation chain transfer (RAFT) radical polymerization. A chloroform solution of St-IPAAm molecules was gently dropped into a Langmuir-trough apparatus, and both barriers of the apparatus were moved horizontally to compress the film to regulate its density. Then, the St-IPAAm Langmuir film was horizontally transferred onto a hydrophobically modified glass substrate by a surface-fixed device. Atomic force microscopy images clearly revealed nanoscale sea-island structures on the surface. The strength, rate, and quality of cell adhesion and detachment on the prepared surface were modulated by changes in temperature across the lower critical solution temperature range of PIPAAm molecules. In addition, a two-dimensional cell structure (cell sheet) was successfully recovered on the optimized surfaces. These unique PIPAAm surfaces may be useful for controlling the strength of cell adhesion and detachment.

Nanoscaled sea-island surfaces composed of thermoresponsive block copolymers were fabricated by the Langmuir-Schaefer method for controlling spontaneous cell adhesion and detachment. Both the preparation of the surface and the adhesion and detachment of cells on the surface were visualized.

Thermoresponsive poly(N-isopropylacrylamide) (PIPAAm)-immobilized surfaces for controlling cell adhesion and detachment were fabricated by the ...

Preparation of 3D Collagen Gels and Microchannels for the Study of 3D Interactions In Vivo

Historically, most cellular processes have been studied in only 2 dimensions. While these studies have been informative about general cell signaling mechanisms, they neglect important cellular cues received from the structural and mechanical properties of the local microenvironment and extracellular matrix (ECM). To understand how cells interact within a physiological ECM, it is important to study them in the context of 3 dimensional assays. Cell migration, cell differentiation, and cell proliferation are only a few processes that have been shown to be impacted by local changes in the mechanical properties of a 3-dimensional ECM. Collagen I, a core fibrillar component of the ECM, is more than a simple structural element of a tissue. Under normal conditions, mechanical cues from the collagen network direct morphogenesis and maintain cellular structures. In diseased microenvironments, such as the tumor microenvironment, the collagen network is often dramatically remodeled, demonstrating altered composition, enhanced deposition and altered fiber organization. In breast cancer, the degree of fiber alignment is important, as an increase in aligned fibers perpendicular to the tumor boundary has been correlated to poorer patient prognosis1. Aligned collagen matrices result in increased dissemination of tumor cells via persistent migration2,3. The following is a simple protocol for embedding cells within a 3-dimensional, fibrillar collagen hydrogel. This protocol is readily adaptable to many platforms, and can reproducibly generate both aligned and random collagen matrices for investigation of cell migration, cell division, and other cellular processes in a tunable, 3-dimensional, physiological microenvironment.

Preparation of 3D Collagen Gels and Microchannels for the Study of 3D Interactions In Vivo

Collagen is a core component of the ECM, and provides essential cues for several cellular processes ranging from migration to differentiation and proliferation. Provided here is a protocol for embedding cells within 3D collagen hydrogels, and a more advanced technique for generating randomized or aligned collagen matrices using PDMS microchannels.

Historically, most cellular processes have been studied in only 2 dimensions.  While these studies have been informative about general cell signaling ...

A Facile and Eco-friendly Route to Fabricate Poly(Lactic Acid) Scaffolds with Graded Pore Size

Over the recent years, functionally graded scaffolds (FGS) gaineda crucial role for manufacturing of devices for tissue engineering. The importance of this new field of biomaterials research is due to the necessity to develop implants capable of mimicking the complex functionality of the various tissues, including a continuous change from one structure or composition to another. In this latter context, one topic of main interest concerns the design of appropriate scaffolds for bone-cartilage interface tissue. In this study, three-layered scaffolds with graded pore size were achieved by melt mixing poly(lactic acid) (PLA), sodium chloride (NaCl) and polyethylene glycol (PEG). Pore size distributions were controlled by NaCl granulometry and PEG solvation. Scaffolds were characterized from a morphological and mechanical point of view. A correlation between the preparation method, the pore architecture and compressive mechanical behavior was found. The interface adhesion strength was quantitatively evaluated by using a custom-designed interfacial strength test. Furthermore, in order to imitate the human physiology, mechanical tests were also performed in phosphate buffered saline (PBS) solution at 37 &#176;C. The method herein presented provides a high control of porosity, pore size distribution and mechanical performance, thus offering the possibility to fabricate three-layered scaffolds with tailored properties by following a simple and eco-friendly route.

A Facile and Eco-friendly Route to Fabricate PolyLactic Acid Scaffolds with Graded Pore Size

In this work, poly(lactic acid)/polyethylene glycol (PLA/PEG) scaffolds were prepared by using a combination of melt mixing and selective leaching. The method herein discussed permitted to develop three-layer scaffolds by highly controlling both porosity and pore size. The mechanical properties were also evaluated in a physiological environment.

Over the recent years, functionally graded scaffolds (FGS) gaineda crucial role for manufacturing of devices for tissue engineering. The importance of ...

Site-Directed Immobilization of Bone Morphogenetic Protein 2 to Solid Surfaces by Click Chemistry

Different therapeutic strategies for the treatment of non-healing long bone defects have been intensively investigated. Currently used treatments present several limitations that have led to the use of biomaterials in combination with osteogenic growth factors, such as bone morphogenetic proteins (BMPs). Commonly used absorption or encapsulation methods require supra-physiological amounts of BMP2, typically resulting in a so-called initial burst release effect that provokes several severe adverse side effects. A possible strategy to overcome these problems would be to covalently couple the protein to the scaffold. Moreover, coupling should be performed in a site-specific manner in order to guarantee a reproducible product outcome. Therefore, we created a BMP2 variant, in which an artificial amino acid (propargyl-L-lysine) was introduced into the mature part of the BMP2 protein by codon usage expansion (BMP2-K3Plk). BMP2-K3Plk was coupled to functionalized beads through copper catalyzed azide-alkyne cycloaddition (CuAAC). The biological activity of the coupled BMP2-K3Plk was proven in vitro and the osteogenic activity of the BMP2-K3Plk-functionalized beads was proven in cell based assays. The functionalized beads in contact with C2C12 cells were able to induce alkaline phosphatase (ALP) expression in locally restricted proximity of the bead. Thus, by this technique, functionalized scaffolds can be produced that can trigger cell differentiation towards an osteogenic lineage. Additionally, lower BMP2 doses are sufficient due to the controlled orientation of site-directed coupled BMP2. With this method, BMPs are always exposed to their receptors on the cell surface in the appropriate orientation, which is not the case if the factors are coupled via non-site-directed coupling techniques. The product outcome is highly controllable and, thus, results in materials with homogeneous properties, improving their applicability for the repair of critical size bone defects.

Biomaterials doped with Bone Morphogenetic Protein 2 (BMP2) have been used as a new therapeutic strategy to heal non-union bone fractures. To overcome side effects resulting from an uncontrollable release of the factor, we propose a new strategy to site-directly immobilize the factor, thus creating materials with improved osteogenic capabilities.

Different therapeutic strategies for the treatment of non-healing long bone defects have been intensively investigated. Currently used treatments present ...