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 (...

<ol>
	<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. 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=Measuring+neutrophil+speed+and+directionality+during+chemotaxis,+directly+from+a+droplet+of+whole+blood.">Measuring neutrophil speed and directionality during chemotaxis, directly from a droplet of whole blood.</a> Technology. , 1-9 (2013).</li><li>Kurihara, 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=Resolvin+D2+restores+neutrophil+directionality+and+improves+survival+after+burns.">Resolvin D2 restores neutrophil directionality and improves survival after burns.</a> FASEB journal : official publication of the Federation of American Societies for Experimental Biology. , (2013).</li><li>Buffone, V., Meakins, J. L., Christou, N. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+function+in+surgical+patients.+Relationship+to+adequate+bacterial+defenses.">Neutrophil function in surgical patients. Relationship to adequate bacterial defenses.</a> Arch Surg. 119, 39-43 (1984).</li><li>Malawista, S. E., de Boisfleury Chevance, A., van Damme, J., Serhan, C. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tonic+inhibition+of+chemotaxis+in+human+plasma.">Tonic inhibition of chemotaxis in human plasma.</a> Proceedings of the National Academy of Sciences of the United States of America. 105, 17949-17954 (2008).</li></ol>

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 />
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		<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

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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.