Support from the National Institutes of Health (grants GM092804, DE019938) and Shriners Burns Hospital.

1. Microfluidic Device Fabrication
<ol>
	<li>Using standard photolithographic techniques, fabricate the master mold wafer in a class 1,000 clean room. Pattern the first 3-&#181;m-thin epoxy-based negative photoresist layer to define the migration channels according to the instructions from the manufacturer. Pattern the second 50-&#181;m-thick layer to define the cell-loading and chemokine chambers.</li>
	<li>Use the patterned wafer to cast polydimethylsiloxane (PDMS) devices. Vigorously mix PDMS (20 g) with initiator (2 g) for 5 min&#160;using plastic fork in large plastic weighing tray.</li>
	<li>Carefully pour PDMS onto mold.</li>
	<li>Degas the PDMS by placing mold with poured PDMS in a vacuum desiccator for 1 hr.</li>
	<li>Bake and cure PDMS microfluidic devices for at least 3 hr&#160;in an oven set to 65 &#176;C.</li>
	<li>Punch out the central WBLCs using a puncher with a tip diameter of 1.5 mm.</li>
	<li>Punch out whole donut-shaped devices using a puncher with a tip diameter of 5.0 mm.</li>
	<li>Remove particles from donut devices using adhesive tape.</li>
	<li>Rinse a 12-well plate with deionized water and then dry with nitrogen. Place plate in 60 &#176;C oven for 5 min.</li>
	<li>Oxygen plasma treat the 12-well plate twice; once alone for 35 sec&#160;and then again with the donut devices for another 35 sec.</li>
	<li>Carefully place devices in the wells of the plate using tweezers.</li>
	<li>Bake plate with bonded devices on a hot plate set to 80 &#176;C for 10 min.</li>
</ol>
2. Microfluidic Assay Preparation
<ol>
	<li>Prime microfluidic devices immediately after oxygen plasma treatment, when the device is hydrophilic and capillary effects can promote the priming of the small channels in the device.</li>
	<li>Create chemoattractant solution by mixing 5 &#181;l&#160;fMLP [stock solution 10 &#181;M] with 5 &#181;l&#160;fibronectin [stock solution 1 mg/ml] and 490 &#181;l&#160;HBSS.</li>
	<li>Slowly pipet&#160;chemoattractant solution into WBLC, using a gel loading tip (Figure 1A). Pipet&#160;an additional 20 &#181;l&#160;of the chemoattractant around the outside of the device.</li>
	<li>Place plate in a desiccator for 15 min. By applying a vacuum to the device, the solution is instilled into the side-channels of the device and the displaced air diffused out through the PDMS.</li>
	<li>Remove plate from desiccator and confirm wetting of device channel under microscope. Watch as bubble becomes smaller as chemoattractant solution enters the chamber. No bubble should be present within the device after vacuum treatment.</li>
	<li>Wash the WBLC and outside of the device thoroughly to remove excess chemoattractant solution. This step generates a gradient of chemoattractant from each of the focal chemotactic chambers (FCCs) to the device center.
	<ol>
		<li>Fill a 1-ml&#160;syringe with PBS, add a 30 G blunt needle tip to syringe. Gently, insert the needle tip of the syringe into the center of the donut hole. Gently push 100 &#181;l&#160;of PBS into the hole so that a droplet of PBS forms on top of the device.</li>
		<li>Tilt plate and pipette 1 ml&#160;of PBS around device so that the liquid collects at the bottom of the well. Aspirate the liquid and repeat process for total of 3x&#160;using fresh buffer solution (use media instead of buffer if the separated neutrophils will be loaded in media)9.</li>
	</ol>
	</li>
	<li>Fill each well with media until the tops of the devices are submerged under liquid. Let the devices sit for 15 min&#160;to allow gradient to stabilize. Experimental results and theoretical data from finite element simulations show that the gradients in these devices are stable up to 24 hr&#160;for small molecules (e.g., fMLP) and up to a several days for larger molecular weight (e.g., IL8).</li>
	<li>Using gel loading tips, slowly pipette 2 &#181;l&#160;of blood (or isolated neutrophils) into each whole blood loading chamber (WBLC) (Figure&#160;1A).</li>
</ol>
3. Sample Preparation
Human Neutrophils From Capillary Blood
<ol>
	<li>Collect capillary blood from finger prick of healthy volunteer, who is on no immunosuppressants. All patient samples were obtained with written informed consent, and through procedures approved by the MGH and Shriners Institutional Review Boards.
	<ol>
		<li>For finger prick blood collection, wash hands with water and soap and dry the skin. Prepare anti-coagulant/stain stock solution by adding 1 ml&#160;HBSS + 0.2% HSA and 10 &#181;l&#160;Hoechst stain (32.4 &#956;M) to heparin blood collection tube (1.65 USP/50 &#181;l&#160;blood). Prick the finger using a SurgiLance safety lancet (2.2-mm depth, 22 G), wipe away first drop of blood and collect 50 &#181;l of blood in Eppendorf tube containing the stock anti-coagulant and Hoechst fluorescent stain solution (10 &#181;l) and gently mix.</li>
	</ol>
	</li>
	<li>Incubate the blood and Hoechst stain for 10 min&#160;to allow for nucleus fluorescent staining. Run sample within 1 hr of blood collection.</li>
</ol>
Human Neutrophils From Venous Blood
<ol start="3">
	<li>Draw 10 ml&#160;of peripheral, venous blood into tubes containing 33 USP heparin.</li>
	<li>Add 50 &#181;l&#160;of venous blood to media and Hoechst stain as previously described. Incubate the blood and Hoechst stain for 10 min&#160;to allow for nucleus fluorescent staining. Run sample within 1 hr of blood collection.</li>
</ol>
Neutrophil Separation From Whole Blood - Positive Control
<ol start="5">
	<li>To separate neutrophils, use sterile techniques to isolate neutrophils from the 10 ml&#160;venous whole blood sample using Hetastarch (6% w/v) density gradient followed by a negative selection magnetic bead isolation kit following the manufacturers protocol.</li>
	<li>Resuspended the final aliquot of neutrophils at a concentration of 4,000 cells/&#181;l&#160;in 1X HBSS + 0.2% human serum albumin. Keep cells at 37 &#176;C until ready to run the experiment.</li>
</ol>
4. Microscopy and Image Analysis for Neutrophil Chemotaxis Measurements
<ol>
	<li>Set up biochamber temperature to 37 &#176;C, humidity at 80%, and CO2 at 5%.</li>
	<li>Start imaging immediately using time-lapse imaging on a microscope (10X or higher magnification).</li>
</ol>
5. Statistical Analysis
<ol>
	<li>Manually track at least 50 neutrophils in each sample.</li>
	<li>Count the cells entering the FCC over time (Figure&#160;2).</li>
	<li>Calculate neutrophil velocities in the channel between WBLC and FCC using ImageJ (NIH) (Figure&#160;2).</li>
	<li>Quantify directionality of neutrophils by counting the number of cells that pass the bifurcation and calculating the ratio between the number of cells that turn toward the FCC and cells that exit the device. Cells that are not directional do not follow the chemotactic gradient and therefore migrate in equal numbers toward the FCC and the exit channel (Figure 2).</li>
</ol>

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	<li>Hansson, G. K., Robertson, A. K., Soderberg-Naucler, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inflammation+and+atherosclerosis.">Inflammation and atherosclerosis.</a> Annual review of pathology. 1, 297-329 (2006).</li><li>Phillipson, M., Kubes, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+neutrophil+in+vascular+inflammation.">The neutrophil in vascular inflammation.</a> Nature medicine. 17, 1381-1390 (2011).</li><li>Butler, K. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Burn+injury+reduces+neutrophil+directional+migration+speed+in+microfluidic+devices.">Burn injury reduces neutrophil directional migration speed in microfluidic devices.</a> PloS one. 5, (2010).</li><li>Lavrentieva, 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=Inflammatory+markers+in+patients+with+severe+burn+injury.+What+is+the+best+indicator+of+sepsis.">Inflammatory markers in patients with severe burn injury. What is the best indicator of sepsis.</a> Burns : journal of the International Society for Burn Injuries. 33, 189-194 (2007).</li><li>De Filippo, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mast+cell+and+macrophage+chemokines+CXCL1/CXCL2+control+the+early+stage+of+neutrophil+recruitment+during+tissue+inflammation.">Mast cell and macrophage chemokines CXCL1/CXCL2 control the early stage of neutrophil recruitment during tissue inflammation.</a> Blood. 121, 4930-4937 (2013).</li><li>Mankovich, A. R., Lee, C. Y., Heinrich, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+effects+of+serum+heat+treatment+on+chemotaxis+and+phagocytosis+by+human+neutrophils.">Differential effects of serum heat treatment on chemotaxis and phagocytosis by human neutrophils.</a> PloS one. 8, (2013).</li><li>Palabrica, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leukocyte+accumulation+promoting+fibrin+deposition+is+mediated+in+vivo+by+P-selectin+on+adherent+platelets.">Leukocyte accumulation promoting fibrin deposition is mediated in vivo by P-selectin on adherent platelets.</a> Nature. 359, 848-851 (1992).</li><li>Sackmann, E. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+kit-on-a-lid:+a+versatile+platform+for+neutrophil+chemotaxis+assays.">Microfluidic kit-on-a-lid: a versatile platform for neutrophil chemotaxis assays.</a> Blood. 120, (2012).</li><li>Jones, C. N., 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=Microfluidic+chambers+for+monitoring+leukocyte+trafficking+and+humanized+nano-proresolving+medicines+interactions.">Microfluidic chambers for monitoring leukocyte trafficking and humanized nano-proresolving medicines interactions.</a> Proceedings of the National Academy of Sciences of the United States of America. 109, 20560-20565 (2012).</li><li>Nauseef, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+human+neutrophils+from+venous+blood.">Isolation of human neutrophils from venous blood.</a> Methods Mol Biol. 412, 15-20 (2007).</li><li>Lyons, P. 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=Microarray+analysis+of+human+leucocyte+subsets:+the+advantages+of+positive+selection+and+rapid+purification.">Microarray analysis of human leucocyte subsets: the advantages of positive selection and rapid purification.</a> BMC genomics. 8, (2007).</li><li>Hasenberg, M., 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=Rapid+immunomagnetic+negative+enrichment+of+neutrophil+granulocytes+from+murine+bone+marrow+for+functional+studies+in+vitro+and+in+vivo.">Rapid immunomagnetic negative enrichment of neutrophil granulocytes from murine bone marrow for functional studies in vitro and in vivo.</a> PloS one. 6, (2011).</li><li>Agrawal, N., Toner, M., Irimia, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+migration+assay+from+a+drop+of+blood.">Neutrophil migration assay from a drop of blood.</a> Lab on a chip. 8, 2054-2061 (2008).</li><li>Hoang, A. 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There are no conflicts of interest to disclose.

In this work, we developed a microfluidic platform to measure neutrophil chemotaxis from a droplet of blood (2 &#181;l). The on-chip mechanical filtration of RBCs from actively migrating neutrophils circumvents the need for cumbersome cell separation methods such as density gradients10, positive selection11, or negative selection12, which are prone to introduce artifacts by activating neutrophils. The mechanical filtration of RBCs distinguishes our technology from other microfluidic chips...

Neutrophil trafficking plays a critical role in determining the progress and resolution of many inflammatory conditions, including atherosclerosis1, bacterial infection or sepsis2, and burn injury3. For their major contribution to health and disease conditions, neutrophil count is part of the standard blood analysis often considered in clinical and research laboratories. However, despite being one of the most ubiquitous tests, the value of neutrophil count in the diagnosis of infection and sepsis has been frequently questioned4. For example, one study of neutrophils in burn patients revealed that neutrophil count and neutrophil migration function do not correlate; signifying that neutrophil count alone is not an accurate indicator of immune status3. Although more difficult to measure, neutrophil functional competence has been proposed as more valuable in a broad range of conditions.
Importantly, many of the neutrophil defects are transient and are not triggered by permanent genetic defects, a distinction that has been largely overlooked in the clinic until recently. In the context of burn injuries, neutrophil migration could be monitored during the course of a patient&#39;s treatment as an indicator of inflammatory status or infection3. Traditional migration assays currently used in the laboratory (Boyden chamber, Dunn chamber, micropipette assay) cannot be translated into a clinical setting because they require large volumes of blood and cumbersome time-consuming neutrophil isolation techniques (Table 1). These assays also cannot be used to monitor transient changes in neutrophil chemotaxis in small laboratory animals, such as mice, because the volume of blood needed for neutrophil isolation allows for only one sample and often even requires pooling of blood from multiple animals for a single assay. For instance, a study involving multiple conditions and treatments over multiple time-points could potentially require thousands of mice using current chemotaxis assays. This restricts the basic biological research that can be done to understand the complex dynamics of immune function in the context of injury, infection or burn often studied in the murine models5.
To address the need for a neutrophil functional assay that is rapid, robust, while requiring minimal blood volume, we have developed a microfluidic device that measures neutrophil chemotaxis directly from a small droplet of whole blood. It is known that many factors in whole blood, including serum6 and platelets7, affect neutrophil function. It is therefore beneficial that the whole blood microfluidic assay minimizes sample processing to maintain the in vivo microenvironment of the neutrophil when measuring variations in chemotaxis with an in vitro assay8. This approach reduces the time from blood collection to neutrophil migration assays from hours using traditional techniques, to just minutes (Table 1). The whole blood microfluidic platform produces a stable linear chemoattractant gradient for the length of the experiment, has no moving parts, and does not require an external pressure source (i.e. syringe pump). The key feature in the design of the whole blood microfluidic device is the incorporation of a red blood cell (RBC) filtration comb that mechanically filters RBCs from entering the migration channel of the device. The right turns of this filtration comb prevent the need for size exclusion filtration, which would likely be clogged by RBCs and therefore block the chemoattractant gradient from reaching the actively migrating neutrophils in the WB. The incorporation of the whole blood microfluidic device in a 12 or 24-well plate facilitates the screening of multiple mediators of human or murine neutrophil chemotaxis simultaneously.

<table border="0" cellpadding="0" cellspacing="0" style="width:771px;" width="771">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">Name of Material/ Equipment</td>
			<td style="width:191px;">Company</td>
			<td style="width:179px;">Catalog Number</td>
			<td style="width:191px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Device Fabrication</td>
			<td style="width:191px;"></td>
			<td style="width:179px;"></td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">SU8&#160;</td>
			<td style="width:191px;">Microchem</td>
			<td style="width:179px;">Y131273</td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Polydimethylsiloxane (PDMS)</td>
			<td style="width:191px;">Ellsworth Adhesives</td>
			<td style="width:179px;">Sylgard 184 1.1 lb. Kit</td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Standard glass slides</td>
			<td style="width:191px;">Fisher Scientific</td>
			<td style="width:179px;">125495</td>
			<td style="width:191px;">1 X 3 inches</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Glass-bottom plate</td>
			<td style="width:191px;">MatTek</td>
			<td style="width:179px;">P12G-1.5-14-F</td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">Harris Uni-Core, Tip Diameter 5.0mm</td>
			<td style="width:191px;">Ted Pella, Inc.</td>
			<td style="width:179px;">15081</td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">Harris Uni-Core, Tip Diameter 1.5 mm</td>
			<td style="width:191px;">Ted Pella, Inc.</td>
			<td style="width:179px;">15072</td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">Microfluidic Assay Preparation and Analysis</td>
			<td style="width:191px;"></td>
			<td style="width:179px;"></td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Gel-loading pipet tip</td>
			<td style="width:191px;">Fisher Scientific</td>
			<td style="width:179px;">02-707-139</td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Syringe</td>
			<td style="width:191px;">Fisher Scientfic</td>
			<td style="width:179px;">309602</td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Blunt tip needle, 30g &#189; in.</td>
			<td style="width:191px;">Brico Medical Supply</td>
			<td style="width:179px;">BN3005</td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Vacutainer, Heparin</td>
			<td style="width:191px;">Becton Dickinson</td>
			<td style="width:179px;"></td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;"></td>
			<td style="width:191px;"></td>
			<td style="width:179px;"></td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">HBSS&#160;</td>
			<td style="width:191px;">Sigma-Aldrich</td>
			<td style="width:179px;"></td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">Human serum albumin</td>
			<td style="width:191px;">Sigma-Aldrich</td>
			<td style="width:179px;">A5843-5G</td>
			<td style="width:191px;">0.2% final concentration in HBSS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Fibronectin</td>
			<td style="width:191px;">Sigma-Aldrich</td>
			<td style="width:179px;">F0895-1MG</td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">fMLP</td>
			<td style="width:191px;">Sigma-Aldrich</td>
			<td style="width:179px;">F3506-10MG</td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">SurgiLance safety lancet, 2.2mm depth, 22 gauge</td>
			<td style="width:191px;"></td>
			<td style="width:179px;">SLN240</td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Hoescht stain</td>
			<td style="width:191px;">Life Technologies</td>
			<td style="width:179px;">H3570</td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Positive Control&#160;</td>
			<td style="width:191px;"></td>
			<td style="width:179px;"></td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">HetaSep</td>
			<td style="width:191px;">STEMCELL Technologies Inc.</td>
			<td style="width:179px;">7906</td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">EasySep Human Neutrophil Enrichment Kit</td>
			<td style="width:191px;">STEMCELL Technologies Inc.</td>
			<td style="width:179px;">19257</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;"></td>
			<td style="width:191px;"></td>
			<td style="width:179px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Equipment</td>
			<td style="width:191px;"></td>
			<td style="width:179px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Plasma Asher</td>
			<td style="width:191px;">March Instruments</td>
			<td style="width:179px;">P-250</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Lindberg/Blue M Oven</td>
			<td style="width:191px;">Thermo Scientific</td>
			<td style="width:179px;">13-258-30C</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">Stainless Steel Precision Tweezers</td>
			<td style="width:191px;">Techni Tool</td>
			<td style="width:179px;">758TW458</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">Bel-Art Scienceware Chemical-Resistant Vacuum Desiccator</td>
			<td style="width:191px;">Fisher Scientific</td>
			<td style="width:179px;">08-594-15A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Dataplate Digital Hot Plate</td>
			<td style="width:191px;">Alpha Multiservices</td>
			<td style="width:179px;">PMC 720&#160;</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">Nikon TiE inverted microscope</td>
			<td style="width:191px;">Nikon - Micro Video Instruments Inc.</td>
			<td style="width:179px;">MEA53100</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">CFI Plan Fluor DL 10x na 15.2wd Objective</td>
			<td style="width:191px;">Nikon - Micro Video Instruments Inc.</td>
			<td style="width:179px;">MRH20101</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">Lumen 200 with 2 Meter Light Guide for Nikon</td>
			<td style="width:191px;">Nikon - Micro Video Instruments Inc.</td>
			<td style="width:179px;">500-L200NI2</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:211px;">DAPI/Hoechst/AMCA Narrow Band 32mm Exciters - 25mm Emitters</td>
			<td style="width:191px;">Chroma - Micro Video Instruments Inc.</td>
			<td style="width:179px;">31013v2</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:211px;">Retiga R 2000 cooled CCD Camera 1600x1200 pixels</td>
			<td style="width:191px;">Qimaging - Micro Video Instruments Inc.</td>
			<td>RET-2000R-F-M-12-C</td>
			<td></td>
		</tr>
	</tbody>
</table>

microfluidic platform for measuring neutrophil chemotaxis from unprocessed whole blood

Neutrophils play an essential role in protection against infections and their numbers in the blood are frequently measured in the clinic. Higher neutrophil counts in the blood are usually an indicator of ongoing infections, while low neutrophil counts are a warning sign for higher risks for infections. To accomplish their functions, neutrophils also have to be able to move effectively from the blood where they spend most of their life, into tissues, where infections occur. Consequently, any defects in the ability of neutrophils to migrate can increase the risks for infections, even when neutrophils are present in appropriate numbers in the blood. However, measuring neutrophil migration ability in the clinic is a challenging task, which is time consuming, requires large volume of blood, and expert knowledge. To address these limitations, we designed a robust microfluidic assays for neutrophil migration, which requires a single droplet of unprocessed blood, circumvents the need for neutrophil separation, and is easy to quantify on a simple microscope. In this assay, neutrophils migrate directly from the blood droplet, through small channels, towards the source of chemoattractant. To prevent the granular flow of red blood cells through the same channels, we implemented mechanical filters with right angle turns that selectively block the advance of red blood cells. We validated the assay by comparing neutrophil migration from blood droplets collected from finger prick and venous blood. We also compared these whole blood (WB) sources with neutrophil migration from samples of purified neutrophils and found consistent speed and directionality between the three sources. This microfluidic platform will enable the study of human neutrophil migration in the clinic and the research setting to help advance our understanding of neutrophil functions in health and disease.

The whole blood (WB) neutrophil chemotaxis assay was validated by measuring the accumulation of neutrophils towards a fMLP gradient (Movie S1). Results confirm that RBCs are trapped by the filtration comb while neutrophils (blue) are able to actively migrate out of whole blood (Figure&#160;3A and Movie S1). The stable linear chemoattractant gradient (green) formed by the whole blood microfluidic device was confirmed using FITC-labeled dextran (Figure&#160;3A</str...

Watch this Scientific Journal Video about Microfluidic Platform for Measuring Neutrophil Chemotaxis from Unprocessed Whole Blood at JoVE.com

Microfluidic Platform for Measuring Neutrophil Chemotaxis from Unprocessed Whole Blood

This protocol details an assay designed to measure human neutrophil chemotaxis from one droplet of whole blood with robust reproducibility. This approach circumvents the need for neutrophil separation and requires only a few minutes of assay preparation time. The microfluidic chip enables the repeated measure of neutrophil chemotaxis over time in infants or small mammals, where sample volume is limited.

Neutrophils play an essential role in protection against infections and their numbers in the blood are frequently measured in the clinic. Higher ...

microfluidic-platform-for-measuring-neutrophil-chemotaxis-from

Research

JoVE Journal

Bioengineering

11.2K Views.  Massachusetts General Hospital. This protocol details an assay designed to measure human neutrophil chemotaxis from one droplet of whole blood with robust reproducibility. This approach circumvents the need for neutrophil separation and requires only a few minutes of assay preparation time. The microfluidic chip enables the repeated measure of neutrophil chemotaxis over time in infants or small mammals, where sample volume is limited.

Video: Microfluidic Platform for Measuring Neutrophil Chemotaxis from Unprocessed Whole Blood

High-throughput Protein Expression Generator Using a Microfluidic Platform

Rapidly increasing fields, such as systems biology, require the development and implementation of new technologies, enabling high-throughput and high-fidelity measurements of large systems. Microfluidics promises to fulfill many of these requirements, such as performing high-throughput screening experiments on-chip, encompassing biochemical, biophysical, and cell-based assays1. Since the early days of microfluidics devices, this field has drastically evolved, leading to the development of microfluidic large-scale integration2,3. This technology allows for the integration of thousands of micromechanical valves on a single device with a postage-sized footprint (Figure 1). We have developed a high-throughput microfluidic platform for generating in vitro expression of protein arrays (Figure 2) named PING (Protein Interaction Network Generator). These arrays can serve as a template for many experiments such as protein-protein 4, protein-RNA5 or protein-DNA6 interactions.
The device consist of thousands of reaction chambers, which are individually programmed using a microarrayer. Aligning of these printed microarrays to microfluidics devices programs each chamber with a single spot eliminating potential contamination or cross-reactivity Moreover, generating microarrays using standard microarray spotting techniques is also very modular, allowing for the arraying of proteins7, DNA8, small molecules, and even colloidal suspensions. The potential impact of microfluidics on biological sciences is significant. A number of microfluidics based assays have already provided novel insights into the structure and function of biological systems, and the field of microfluidics will continue to impact biology.

We present a microfluidic approach for the expression of protein arrays. The device consists of thousands of reaction chambers controlled by micro-mechanical valves. The microfluidic device is mated to a microarray-printed gene library. These genes are then transcribed and translated on-chip, resulting in a protein array ready for experimental use.

Rapidly increasing fields, such as systems biology, require the development and implementation of new technologies, enabling high-throughput and ...

Cell Squeezing as a Robust, Microfluidic Intracellular Delivery Platform

Rapid mechanical deformation of cells has emerged as a promising, vector-free method for intracellular delivery of macromolecules and nanomaterials. This technology has shown potential in addressing previously challenging applications; including, delivery to primary immune cells, cell reprogramming, carbon nanotube, and quantum dot delivery. This vector-free microfluidic platform relies on mechanical disruption of the cell membrane to facilitate cytosolic delivery of the target material. Herein, we describe the detailed method of use for these microfluidic devices including, device assembly, cell preparation, and system operation. This delivery approach requires a brief optimization of device type and operating conditions for previously unreported applications. The provided instructions are generalizable to most cell types and delivery materials as this system does not require specialized buffers or chemical modification/conjugation steps. This work also provides recommendations on how to improve device performance and trouble-shoot potential issues related to clogging, low delivery efficiencies, and cell viability.

Rapid mechanical deformation of cells has emerged as a promising, vector-free method for intracellular delivery of macromolecules and nanomaterials. This protocol provides detailed steps on how to use the system for a broad range of applications.

Rapid mechanical deformation of cells has emerged as a promising, vector-free method for intracellular delivery of macromolecules and nanomaterials. This ...

The Multi-organ Chip - A Microfluidic Platform for Long-term Multi-tissue Coculture

The ever growing amount of new substances released onto the market and the limited predictability of current in vitro test systems has led to a high need for new solutions for substance testing. Many drugs that have been removed from the market due to drug-induced liver injury released their toxic potential only after several doses of chronic testing in humans. However, a controlled microenvironment is pivotal for long-term multiple dosing experiments,&#160;as even minor alterations in extracellular conditions may greatly influence the cell physiology. We focused within our research program on the generation of a microengineered bioreactor, which can be dynamically perfused by an on-chip pump and combines at least two culture spaces for multi-organ applications. This circulatory system mimics the in vivo conditions of primary cell cultures better and assures a steadier,&#160;more quantifiable extracellular relay of signals to the cells. 
For demonstration purposes, human liver equivalents, generated by aggregating differentiated HepaRG cells with human hepatic stellate cells in hanging drop plates, were cocultured with human skin punch biopsies for up to 28 days inside the microbioreactor. The use of cell culture inserts enables the skin to be cultured at an air-liquid interface, allowing topical substance exposure. The microbioreactor system is capable of supporting these cocultures at near physiologic fluid flow and volume-to-liquid ratios, ensuring stable and organotypic culture conditions. The possibility of long-term cultures enables the repeated exposure to substances. Furthermore, a vascularization of the microfluidic channel circuit using human dermal microvascular endothelial cells yields a physiologically more relevant vascular model.

Here, we present a protocol to coculture primary cells, tissue models and punch biopsies in a microfluidic multi-organ chip for up to 28 days. Human dermal microvascular endothelial cells, liver aggregates and skin biopsies were successfully combined in a common media circulation.

The ever growing amount of new substances released onto the market and the limited predictability of current in vitro test systems has led to a high need ...

Controlled Microfluidic Environment for Dynamic Investigation of Red Blood Cell Aggregation

Blood, as a non-Newtonian biofluid, represents the focus of numerous studies in the hemorheology field. Blood constituents include red blood cells, white blood cells and platelets that are suspended in blood plasma. Due to the abundance of the RBCs (40% to 45% of the blood volume), their behavior dictates the rheological behavior of blood especially in the microcirculation. At very low shear rates, RBCs are seen to assemble and form entities called aggregates, which causes the non-Newtonian behavior of blood. It is important to understand the conditions of the aggregates formation to comprehend the blood rheology in microcirculation. The protocol described here details the experimental procedure to determine quantitatively the RBC aggregates in microcirculation under constant shear rate, based on image processing. For this purpose, RBC-suspensions are tested and analyzed in 120 x 60 &#181;m poly-dimethyl-siloxane (PDMS) microchannels. The RBC-suspensions are entrained using a second fluid in order to obtain a linear velocity profile within the blood layer and thus achieve a wide range of constant shear rates. The shear rate is determined using a micro Particle Image Velocimetry (&#181;PIV) system, while RBC aggregates are visualized using a high speed camera. The videos captured of the RBC aggregates are analyzed using image processing techniques in order to determine the aggregate sizes based on the images intensities.

The protocol described details an experimental procedure to quantify Red Blood Cell (RBC) aggregates under a controlled and constant shear rate, based on image processing techniques. The goal of this protocol is to relate RBC aggregate sizes to the corresponding shear rate in a controlled microfluidic environment.

Blood, as a non-Newtonian biofluid, represents the focus of numerous studies in the hemorheology field. Blood constituents include red blood cells, white ...

A Microfluidic Platform for High-throughput Single-cell Isolation and Culture

Studying the heterogeneity of single cells is crucial for many biological questions, but is technically difficult. Thus, there is a need for a simple, yet high-throughput, method to perform single-cell culture experiments. Here, we report a microfluidic chip-based strategy for high-efficiency single-cell isolation (~77%) and demonstrate its capability of performing long-term single-cell culture (up to 7 d) and cellular heterogeneity analysis using clonogenic assay. These applications were demonstrated with KT98 mouse neural stem cells, and A549 and MDA-MB-435 human cancer cells. High single-cell isolation efficiency and long-term culture capability are achieved by using different sizes of microwells on the top and bottom of the microfluidic channel. The small microwell array is designed for precisely isolating single-cells, and the large microwell array is used for single-cell clonal culture in the microfluidic chip. This microfluidic platform constitutes an attractive approach for single-cell culture applications, due to its flexibility of adjustable cell culture spaces for different culture strategies, without decreasing isolation efficiency.

Here, we present a protocol for isolating and culturing single cells with a microfluidic platform, which utilizes a new microwell design concept to allow for high-efficiency single cell isolation and long-term clonal culture.

Studying the heterogeneity of single cells is crucial for many biological questions, but is technically difficult. Thus, there is a need for a simple, yet ...

Fully Automated Centrifugal Microfluidic Device for Ultrasensitive Protein Detection from Whole Blood

Enzyme-linked immunosorbent assay (ELISA) is a promising method to detect small amount of proteins in biological samples. The devices providing a platform for reduced sample volume and assay time as well as full automation are required for potential use in point-of-care-diagnostics. Recently, we have demonstrated ultrasensitive detection of serum proteins, C-reactive protein (CRP) and cardiac troponin I (cTnI), utilizing a lab-on-a-disc composed of TiO2 nanofibrous (NF) mats. It showed a large dynamic range with femto molar (fM) detection sensitivity, from a small volume of whole blood in 30 min. The device consists of several components for blood separation, metering, mixing, and washing that are automated for improved sensitivity from low sample volumes. Here, in the video demonstration, we show the experimental protocols and know-how for the fabrication of NFs as well as the disc, their integration and the operation in the following order: processes for preparing TiO2 NF mat; transfer-printing of TiO2 NF mat onto the disc; surface modification for immune-reactions, disc assembly and operation; on-disc detection and representative results for immunoassay. Use of this device enables multiplexed analysis with minimal consumption of samples and reagents. Given the advantages, the device should find use in a wide variety of applications, and prove beneficial in facilitating the analysis of low abundant proteins.

This protocol demonstrates how to achieve femto molar detection sensitivity of proteins in 10 &#181;L of whole blood within 30 min. This can be achieved by using electrospun nanofibrous mats integrated in a lab-on-a-disc, which offers high surface area as well as effective mixing and washing for enhanced signal-to-noise ratio.

Enzyme-linked immunosorbent assay (ELISA) is a promising method to detect small amount of proteins in biological samples. The devices providing a platform ...

Microfluidic Platform with Multiplexed Electronic Detection for Spatial Tracking of Particles

Microfluidic processing of biological samples typically involves differential manipulations of suspended particles under various force fields in order to spatially fractionate the sample based on a biological property of interest. For the resultant spatial distribution to be used as the assay readout, microfluidic devices are often subjected to microscopic analysis requiring complex instrumentation with higher cost and reduced portability. To address this limitation, we have developed an integrated electronic sensing technology for multiplexed detection of particles at different locations on a microfluidic chip. Our technology, called Microfluidic CODES, combines Resistive Pulse Sensing with Code Division Multiple Access to compress 2D spatial information into a 1D electrical signal. In this paper, we present a practical demonstration of the Microfluidic CODES technology to detect and size cultured cancer cells distributed over multiple microfluidic channels. As validated by the high-speed microscopy, our technology can accurately analyze dense cell populations all electronically without the need for an external instrument. As such, the Microfluidic CODES can potentially enable low-cost integrated lab-on-a-chip devices that are well suited for the point-of-care testing of biological samples.

We demonstrate a microfluidic platform with an integrated surface electrode network that combines resistive pulse sensing (RPS) with code division multiple access (CDMA), to multiplex detection and sizing of particles in multiple microfluidic channels.

Microfluidic processing of biological samples typically involves differential manipulations of suspended particles under various force fields in order to ...

Imaging the Root Hair Morphology of Arabidopsis Seedlings in a Two-layer Microfluidic Platform

Root hairs increase root surface area for better water uptake and nutrient absorption by the plant. Because they are small in size and often obscured by their natural environment, root hair morphology and function are difficult to study and often excluded from plant research. In recent years, microfluidic platforms have offered a way to visualize root systems at high resolution without disturbing the roots during transfer to an imaging system. The microfluidic platform presented here builds on previous plant-on-a-chip research by incorporating a two-layer device to confine the Arabidopsis thaliana main root to the same optical plane as the root hairs. This design enables the quantification of root hairs on a cellular and organelle level and also prevents z-axis drifting during the addition of experimental treatments. We describe how to store the devices in a contained and hydrated environment, without the need for fluidic pumps, while maintaining a gnotobiotic environment for the seedling. After the optical imaging experiment, the device may be disassembled and used as a substrate for atomic force or scanning electron microscopy while keeping fine root structures intact.

Imaging the Root Hair Morphology of Arabidopsis Seedlings in a Two-layer Microfluidic Platform

This article demonstrates how to culture Arabidopsis thaliana seedlings in a two-layer microfluidic platform that confines the main root and root hairs to a single optical plane. This platform can be used for real-time optical imaging of fine root morphology as well as for high-resolution imaging by other means.

Root hairs increase root surface area for better water uptake and nutrient absorption by the plant. Because they are small in size and often obscured by ...

A Microfluidic Platform for Longitudinal Imaging in Caenorhabditis elegans

In the last decade, microfluidic techniques have been applied to study small animals, including the nematode Caenorhabditis elegans, and have proved useful as a convenient live imaging platform providing capabilities for precise control of experimental conditions in real time. In this article, we demonstrate live imaging of individual worms employing WormSpa, a previously-published custom microfluidic device. In the device, multiple worms are individually confined to separate chambers, allowing multiplexed longitudinal surveillance of various biological processes. To illustrate the capability, we performed proof-of-principle experiments in which worms were infected in the device with pathogenic bacteria, and the dynamics of expression of immune response genes and egg laying were monitored continuously in individual animals. The simple design and operation of this device make it suitable for users with no previous experience with microfluidic-based experiments. We propose that this approach will be useful for many researchers interested in longitudinal observations of biological processes under well-defined conditions.

A Microfluidic Platform for Longitudinal Imaging in Caenorhabditis elegans

In this article, we demonstrate live imaging of individual worms employing a custom microfluidic device. In the device, multiple worms are individually confined to separate chambers, allowing multiplexed longitudinal surveillance of various biological processes.

In the last decade, microfluidic techniques have been applied to study small animals, including the nematode Caenorhabditis elegans, and have proved ...

An Ultrahigh-throughput Microfluidic Platform for Single-cell Genome Sequencing

Sequencing technologies have undergone a paradigm shift from bulk to single-cell resolution in response to an evolving understanding of the role of cellular heterogeneity in biological systems. However, single-cell sequencing of large populations has been hampered by limitations in processing genomes for sequencing. In this paper, we describe a method for single-cell genome sequencing (SiC-seq) which uses droplet microfluidics to isolate, amplify, and barcode the genomes of single cells. Cell encapsulation in microgels allows the compartmentalized purification and tagmentation of DNA, while a microfluidic merger efficiently pairs each genome with a unique single-cell oligonucleotide barcode, allowing &gt;50,000 single cells to be sequenced per run. The sequencing data is demultiplexed by barcode, generating groups of reads originating from single cells. As a high-throughput and low-bias method of single-cell sequencing, SiC-seq will enable a broader range of genomic studies targeted at diverse cell populations.

Single-cell sequencing reveals genotypic heterogeneity in biological systems, but current technologies lack the throughput necessary for the deep profiling of community composition and function. Here, we describe a microfluidic workflow for sequencing &gt;50,000 single-cell genomes from diverse cell populations.

Sequencing technologies have undergone a paradigm shift from bulk to single-cell resolution in response to an evolving understanding of the role of ...