Name: designing microfluidic devices for studying cellular responses under single or coexisting chemical/electrical/shear stress stimuli
Uploaded: 2016-08-13T15:00:00
Description: Watch this Scientific Journal Video about Designing Microfluidic Devices for Studying Cellular Responses Under Single or Coexisting Chemical/Electrical/Shear Stress Stimuli at JoVE.com

This work was financially supported by the Ministry of Science and Technology of Taiwan under Contract No. MOST 104-2311-B-002-026 (K. Y. Lo), No. MOST 104-2112-M-030-002 (Y. S. Sun), and National Taiwan University Career Development Project (103R7888) (K. Y. Lo). The authors also thank the Center for Emerging Material and Advanced Devices, National Taiwan University, for the use of the cell culture room.

1. Chip Design and Fabrication
<ol>
	<li>Draw patterns to be ablated on PMMA substrates and double-side tapes using commercial software 24.
	<ol>
		<li>To study the effects of chemical concentrations and shear stresses, draw a &#34;Christmas tree&#34; pattern with a varying width at its end in each of the five culture areas (Figure 1A and 1B).</li>
		<li>To study the effects of chemical concentrations and electric fields, draw a &#34;Christmas tree&#34; pattern with two more...

<ol>
	<li>Cheng, J. Y., Yen, M. H., Kuo, C. T., Young, T. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+transparent+cell-culture+microchamber+with+a+variably+controlled+concentration+gradient+generator+and+flow+field+rectifier.">A transparent cell-culture microchamber with a variably controlled concentration gradient generator and flow field rectifier.</a> Biomicrofluidics. 2, (2008).</li><li>Terry, S. C., Jerman, J. H., Angell, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gas-Chromatographic+Air+Analyzer+Fabricated+on+a+Silicon-Wafer.">Gas-Chromatographic Air Analyzer Fabricated on a Silicon-Wafer.</a> Ieee T Electron Dev. 26, 1880-1886 (1979).</li><li>Whitesides, G. M., Ostuni, E., Takayama, S., Jiang, X., Ingber, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Soft+lithography+in+biology+and+biochemistry.">Soft lithography in biology and biochemistry.</a> Annu Rev Biomed Eng. 3, 335-373 (2001).</li><li>Adler, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemoreceptors+in+bacteria.">Chemoreceptors in bacteria.</a> Science. 166, 1588-1597 (1969).</li><li>Boyden, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+chemotactic+effect+of+mixtures+of+antibody+and+antigen+on+polymorphonuclear+leucocytes.">The chemotactic effect of mixtures of antibody and antigen on polymorphonuclear leucocytes.</a> J Exp Med. 115, 453-466 (1962).</li><li>Kao, Y. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modulating+chemotaxis+of+lung+cancer+cells+by+using+electric+fields+in+a+microfluidic+device.">Modulating chemotaxis of lung cancer cells by using electric fields in a microfluidic device.</a> Biomicrofluidics. 8, 024107 (2014).</li><li>Walker, G. 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=Effects+of+flow+and+diffusion+on+chemotaxis+studies+in+a+microfabricated+gradient+generator.">Effects of flow and diffusion on chemotaxis studies in a microfabricated gradient generator.</a> Lab Chip. 5, 611-618 (2005).</li><li>Al-Majed, A. A., Neumann, C. M., Brushart, T. M., Gordon, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Brief+electrical+stimulation+promotes+the+speed+and+accuracy+of+motor+axonal+regeneration.">Brief electrical stimulation promotes the speed and accuracy of motor axonal regeneration.</a> J Neurosci. 20, 2602-2608 (2000).</li><li>Nuccitelli, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endogenous+electric+fields+in+embryos+during+development,+regeneration+and+wound+healing.">Endogenous electric fields in embryos during development, regeneration and wound healing.</a> Radiat Prot Dosim. 106, 375-383 (2003).</li><li>McCaig, C. D., Rajnicek, A. M., Song, B., Zhao, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlling+cell+behavior+electrically:+Current+views+and+future+potential.">Controlling cell behavior electrically: Current views and future potential.</a> Physiol Rev. 85, 943-978 (2005).</li><li>Tai, G., Reid, B., Cao, L., Zhao, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrotaxis+and+wound+healing:+experimental+methods+to+study+electric+fields+as+a+directional+signal+for+cell+migration.">Electrotaxis and wound healing: experimental methods to study electric fields as a directional signal for cell migration.</a> Methods Mol Biol. 571, 77-97 (2009).</li><li>Huang, C. W., Cheng, J. Y., Yen, M. H., Young, T. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrotaxis+of+lung+cancer+cells+in+a+multiple-electric-field+chip.">Electrotaxis of lung cancer cells in a multiple-electric-field chip.</a> Biosens Bioelectron. 24, 3510-3516 (2009).</li><li>Yan, X. 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=Lung+Cancer+A549+Cells+Migrate+Directionally+in+DC+Electric+Fields+With+Polarized+and+Activated+EGFRs.">Lung Cancer A549 Cells Migrate Directionally in DC Electric Fields With Polarized and Activated EGFRs.</a> Bioelectromagnetics. 30, 29-35 (2009).</li><li>Li, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activated+T+lymphocytes+migrate+toward+the+cathode+of+DC+electric+fields+in+microfluidic+devices.">Activated T lymphocytes migrate toward the cathode of DC electric fields in microfluidic devices.</a> Lab Chip. 11, 1298-1304 (2011).</li><li>Lin, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lymphocyte+electrotaxis+in+vitro+and+in+vivo.">Lymphocyte electrotaxis in vitro and in vivo.</a> J Immunol. 181, 2465-2471 (2008).</li><li>Zhang, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrically+Guiding+Migration+of+Human+Induced+Pluripotent+Stem+Cells.">Electrically Guiding Migration of Human Induced Pluripotent Stem Cells.</a> Stem Cell Rev. , (2011).</li><li>Song, B., 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=Application+of+direct+current+electric+fields+to+cells+and+tissues+in+vitro+and+modulation+of+wound+electric+field+in+vivo.">Application of direct current electric fields to cells and tissues in vitro and modulation of wound electric field in vivo.</a> Nat Protoc. 2, 1479-1489 (2007).</li><li>Sun, Y. S., Peng, S. W., Cheng, J. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+electrical-stimulated+wound-healing+chip+for+studying+electric+field-assisted+wound-healing+process.">In vitro electrical-stimulated wound-healing chip for studying electric field-assisted wound-healing process.</a> Biomicrofluidics. 6, 34117 (2012).</li><li>Sun, Y. S., Peng, S. W., Lin, K. H., Cheng, J. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrotaxis+of+lung+cancer+cells+in+ordered+three-dimensional+scaffolds.">Electrotaxis of lung cancer cells in ordered three-dimensional scaffolds.</a> Biomicrofluidics. 6, (2012).</li><li>Li, J., Zhu, L., Zhang, M., Lin, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+device+for+studying+cell+migration+in+single+or+co-existing+chemical+gradients+and+electric+fields.">Microfluidic device for studying cell migration in single or co-existing chemical gradients and electric fields.</a> Biomicrofluidics. 6, 24121-2412113 (2012).</li><li>Hou, H. S., Tsai, H. F., Chiu, H. T., Cheng, J. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+chemical+and+electrical+stimulation+on+lung+cancer+cells+using+a+multichannel-dual-electric-field+chip.">Simultaneous chemical and electrical stimulation on lung cancer cells using a multichannel-dual-electric-field chip.</a> Biomicrofluidics. 8, 052007 (2014).</li><li>Lo, K. Y., Wu, S. Y., Sun, Y. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+microfluidic+device+for+studying+the+production+of+reactive+oxygen+species+and+the+migration+in+lung+cancer+cells+under+single+or+coexisting+chemical/electrical+stimulation.">A microfluidic device for studying the production of reactive oxygen species and the migration in lung cancer cells under single or coexisting chemical/electrical stimulation.</a> Microfluid Nanofluidics. 20, 15 (2016).</li><li>Lo, K. Y., Zhu, Y., Tsai, H. F., Sun, Y. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+shear+stresses+and+antioxidant+concentrations+on+the+production+of+reactive+oxygen+species+in+lung+cancer+cells.">Effects of shear stresses and antioxidant concentrations on the production of reactive oxygen species in lung cancer cells.</a> Biomicrofluidics. 7, 64108 (2013).</li><li>Cheng, J. Y., Wei, C. W., Hsu, K. H., Young, T. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct-write+laser+micromachining+and+universal+surface+modification+of+PMMA+for+device+development.">Direct-write laser micromachining and universal surface modification of PMMA for device development.</a> Sensor Actuat B-Chem. 99, 186-196 (2004).</li><li>Chen, J. J. W., 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=Global+analysis+of+gene+expression+in+invasion+by+a+lung+cancer+model.">Global analysis of gene expression in invasion by a lung cancer model.</a> Cancer Res. 61, 5223-5230 (2001).</li><li>Shih, J. Y., 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=Collapsin+response+mediator+protein-1+and+the+invasion+and+metastasis+of+cancer+cells.">Collapsin response mediator protein-1 and the invasion and metastasis of cancer cells.</a> J Natl Cancer I. 93, 1392-1400 (2001).</li><li>Lu, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+shear+devices+for+quantitative+analysis+of+cell+adhesion.">Microfluidic shear devices for quantitative analysis of cell adhesion.</a> Anal Chem. 76, 5257-5264 (2004).</li><li>Fried, L. E., Arbiser, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Honokiol,+a+Multifunctional+Antiangiogenic+and+Antitumor+Agent.">Honokiol, a Multifunctional Antiangiogenic and Antitumor Agent.</a> Antioxid Redox Sign. 11, 1139-1148 (2009).</li><li>Chisti, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrodynamic+damage+to+animal+cells.">Hydrodynamic damage to animal cells.</a> Crit Rev Biotechnol. 21, 67-110 (2001).</li><li>Davies, P. F., Remuzzi, A., Gordon, E. J., Dewey, C. F., Gimbrone, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Turbulent+fluid+shear+stress+induces+vascular+endothelial+cell+turnover+in+vitro.">Turbulent fluid shear stress induces vascular endothelial cell turnover in vitro.</a> Proc Natl Acad Sci U S A. 83, 2114-2117 (1986).</li><li>Zoro, B. J., Owen, S., Drake, R. A., Hoare, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+impact+of+process+stress+on+suspended+anchorage-dependent+mammalian+cells+as+an+indicator+of+likely+challenges+for+regenerative+medicines.">The impact of process stress on suspended anchorage-dependent mammalian cells as an indicator of likely challenges for regenerative medicines.</a> Biotechnol Bioeng. 99, 468-474 (2008).</li><li>Chin, L. 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=Production+of+reactive+oxygen+species+in+endothelial+cells+under+different+pulsatile+shear+stresses+and+glucose+concentrations.">Production of reactive oxygen species in endothelial cells under different pulsatile shear stresses and glucose concentrations.</a> Lab Chip. 11, 1856-1863 (2011).</li><li>Tsai, H. F., Peng, S. W., Wu, C. Y., Chang, H. F., Cheng, J. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrotaxis+of+oral+squamous+cell+carcinoma+cells+in+a+multiple-electric-field+chip+with+uniform+flow+field.">Electrotaxis of oral squamous cell carcinoma cells in a multiple-electric-field chip with uniform flow field.</a> Biomicrofluidics. 6, 34116 (2012).</li></ol>

PMMA-based chips are fabricated using laser ablation and writing which are cheaper and easier methods when compared to PDMS-based chips which require more complicated soft lithography. After designing a microfluidic chip, the fabrication and assembly can be done within just 5 min. There are some critical steps that attention should be paid to in performing the experiment. The first is the &#34;assembling&#34; issue. The adaptors should be glued properly to the top-most layer of the chip. Glue could leak into the fluidic ...

In vivo cells are surrounded by a variety of biomolecules including extracellular matrix (ECM), carbohydrates, lipids, and other cells. They functionalize by responding to micro-environmental stimuli such as interactions with ECM and responses to chemical gradients of various growth factors. Traditionally, in vitro cell studies are conducted in cell culture dishes where the consumption of cells and reagents is large and cells grow in a static (non-circulating) environment. Recently, micro-fabricated devices integrated with fluidic components have provided an alternative platform for cell studies in a more controllable way. Such devices are capable of creating a precise micro-environment of chemical and physical stimuli while minimizing the consumption of cells and reagents. These microfluidic chips can be made of glass substrates, silicon wafers, polydimethylsiloxane (PDMS) polymers, polymethylmethacrylate (PMMA) substrates, or polyethyleneterephthalate (PET) substrates 1-3. PDMS-based devices are transparent, biocompatible, and permeable to gases, making them suitable for long-term cell culture and studies. PMMA and PET substrates are cheap and easy to be processed using laser ablation and writing.
Microfluidic devices should provide cells with a stable and controllable micro-environment where cells are subject to different chemical and physical stimuli. For example, microfluidic chips are used to study chemotaxis of cells. Instead of traditional methods that employ Boyden chamber and capillary 4,5 these miniaturized fluidic devices can generate precise chemical gradients for studying cells&#39; behaviors 1,6,7. Another example is to study cells&#39; directional migration under electric fields (EFs), a phenomenon named electrotaxis. Electrotactic behaviors of cells were reported to be related to nerve regeneration 8, embryonic development 9, and wound healing 10,11. And many studies have been performed to investigate the electrotaxis of various cell types including cancer cells 12,13, lymphocytes 14,15, leukemia cells 11, and stem cells 16. Conventionally, Petri dishes and cover glasses are used to construct electrotactic chambers for generating EFs 17. Such simple setups pose problems of medium evaporation and imprecise EFs, but they can be overcome by microfluidic devices of enclosed, well-defined fluidic channels 12,18,19.
To systematically study cellular responses under precise, controllable chemical and electrical stimuli, it would be of great use to develop microfluidic devices capable of providing cells with multiple stimuli at the same time. For example, Li et al. reported a PDMS-based microfluidic device for creating single or coexisting chemical gradients and EFs 20. Kao et al. developed a similar microfluidic chip to modulate the chemotaxis of lung cancer cells by EFs 6. Moreover, to increase the throughput, Hou et al. designed and fabricated a PMMA-based multichannel-dual-electric-field chip to provide cells with 8 different combined stimuli, being (2 EF strengths x 4 chemical concentrations)21. To further increase the throughout and add the shear stress stimulus, we developed two PMMA-based microfluidic devices for studying cellular responses under single or coexisting chemical/electrical/shear stress stimuli.
Reported by Lo et al. 22,23, these devices contain five independent cell culture channels subject to continuous fluidic flowing, mimicking the in vivo circulatory system. In the first chip (the chemical-shear stress chip or the CSS chip), five relative concentrations of 0, 1/8, 1/2, 7/8, and 1 are generated in the culture regions, and a shear stress gradient is produced inside each of the five culture areas. In the second chip (the chemical-electric field chip or the CEF chip), by using one single set of electrodes and 2 syringe pumps, five EF strengths are generated in addition to five different chemical concentrations within these culture areas. Numerical calculations and simulations are performed to better design and operate these chips, and lung cancer cells cultured inside these devices are subject to single or coexisting stimuli for observing their responses with respect to the production of reactive oxygen species (ROS), the migration rate, and the migration direction. These chips are demonstrated to be time-saving, high-throughput and reliable devices for investigating how cells respond to various micro-environmental stimuli.

<table border="0" cellpadding="0" cellspacing="0" width="1070">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:279px;">Dulbecco&#39;s Modified Eagle Medium (DMEM)</td>
			<td style="width:213px;">Gibco</td>
			<td style="width:119px;">11965-092</td>
			<td style="width:460px;">Cell culture medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Trypsin</td>
			<td style="width:213px;">Gibco</td>
			<td style="width:119px;">25300-054</td>
			<td>detach cell from the dish</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Fetal bovine serum (FBS)</td>
			<td style="width:213px;">Gibco</td>
			<td style="width:119px;">10082147</td>
			<td>Cell culture medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">10-cm cell culture Petri dish</td>
			<td style="width:213px;">Nunc</td>
			<td style="width:119px;">150350</td>
			<td>Cell culture</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Bright-Line&#160;Hemacytometer</td>
			<td style="width:213px;">Sigma</td>
			<td>Z359629</td>
			<td>Cell Counting Equipment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">PMMA</td>
			<td style="width:213px;">Customized</td>
			<td style="width:119px;">Customized</td>
			<td>Microfluidic chip</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Adaptor</td>
			<td style="width:213px;">Customized</td>
			<td style="width:119px;">Customized</td>
			<td>Microfluidic chip</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">0.07/0.22 mm double-sided tape&#160;</td>
			<td>3M</td>
			<td>8018/9088</td>
			<td>Microfluidic chip</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Low melting point agarose</td>
			<td style="width:213px;">Sigma</td>
			<td style="width:119px;">A9414</td>
			<td>Salt bridge</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2&#39;-7&#39;-dichlorodihydrofluoresce diacetate</td>
			<td>Sigma</td>
			<td style="width:119px;">D6883</td>
			<td>Intracellular ROS measurement</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Indium tin oxide (ITO) glass</td>
			<td style="width:213px;">Merck</td>
			<td>300739</td>
			<td>Heater</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Proportional-integral-derivative controller&#160;</td>
			<td>JETEC Electronics Co.</td>
			<td>TTM-J4-R-AB</td>
			<td>Temperature controller</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Thermal coupler</td>
			<td>TECPEL</td>
			<td style="width:119px;">TPK-02A</td>
			<td>Temperature controller</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">CO2 laser scriber</td>
			<td>Laser Tools &#38; Technics Corp.</td>
			<td style="width:119px;">ILS2</td>
			<td>Microfluidic chip fabrication</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Syringe pumps</td>
			<td>New Era</td>
			<td style="width:119px;">NE-300</td>
			<td>Pumping medium and chemicals into the chip</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Power supply</td>
			<td>Major Science&#160;</td>
			<td style="width:119px;">MP-300V</td>
			<td>Supplying direct currents</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Inverted microscope</td>
			<td>Olympus</td>
			<td>CKX41</td>
			<td>Monitoring cell migration</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Inverted fluorescent microscope</td>
			<td style="width:213px;">Nikon</td>
			<td style="width:119px;">TS-100</td>
			<td>Monitoring cell migartion and fluorescencent signals</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DSLR camera</td>
			<td>Canon</td>
			<td>60D</td>
			<td>Recording bright-field images&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CCD camera</td>
			<td>Nikon</td>
			<td style="width:119px;">DS-Qi1</td>
			<td>Recording fluorescent images&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">super glue</td>
			<td style="width:213px;">3M Scotch</td>
			<td style="width:119px;">7004</td>
			<td>Attaching adaptors to PMMA substrates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">AutoCAD</td>
			<td style="width:213px;">Autodesk Inc.</td>
			<td style="width:119px;"></td>
			<td>Designing microfluidic chips</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">DMSO</td>
			<td style="width:213px;">Sigma</td>
			<td style="width:119px;">D8418</td>
			<td>Dissolving DCFDA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">ImgeJ</td>
			<td style="width:213px;">National Institutes of Health</td>
			<td style="width:119px;"></td>
			<td>Quantifying fluorescent intensities and cell migration</td>
		</tr>
	</tbody>
</table>

designing microfluidic devices for studying cellular responses under single or coexisting chemical/electrical/shear stress stimuli

Microfluidic devices are capable of creating a precise and controllable cellular micro-environment of pH, temperature, salt concentration, and other physical or chemical stimuli. They have been commonly used for in vitro cell studies by providing in vivo like surroundings. Especially, how cells response to chemical gradients, electrical fields, and shear stresses has drawn many interests since these phenomena are important in understanding cellular properties and functions. These microfluidic chips can be made of glass substrates, silicon wafers, polydimethylsiloxane (PDMS) polymers, polymethylmethacrylate (PMMA) substrates, or polyethyleneterephthalate (PET) substrates. Out of these materials, PMMA substrates are cheap and can be easily processed using laser ablation and writing. Although a few microfluidic devices have been designed and fabricated for generating multiple, coexisting chemical and electrical stimuli, none of them was considered efficient enough in reducing experimental repeats, particular for screening purposes. In this report, we describe our design and fabrication of two PMMA-based microfluidic chips for investigating cellular responses, in the production of reactive oxygen species and the migration, under single or coexisting chemical/electrical/shear stress stimuli. The first chip generates five relative concentrations of 0, 1/8, 1/2, 7/8, and 1 in the culture regions, together with a shear stress gradient produced inside each of these areas. The second chip generates the same relative concentrations, but with five different electric field strengths created within each culture area. These devices not only provide cells with a precise, controllable micro-environment but also greatly increase the experimental throughput.

The Chemical-shear Stress (CSS) Chip
The CSS chip is made of three PMMA sheets, each of thickness 1 mm, attached together via two double-sided tapes, each of thickness 0.07 mm (Figure 1A and 1B). The &#34;Christmas tree&#34; structure generates five relative concentrations of 0, 1/8, 1/2, 7/8, and 1 in the five culture areas. By designing the culture area as a triangle, a shear stress gradient, ...

Watch this Scientific Journal Video about Designing Microfluidic Devices for Studying Cellular Responses Under Single or Coexisting Chemical/Electrical/Shear Stress Stimuli at JoVE.com

Designing Microfluidic Devices for Studying Cellular Responses Under Single or Coexisting Chemical/Electrical/Shear Stress Stimuli

Micro-fabricated devices integrated with fluidic components provide an in vitro platform for cell studies mimicking the in vivo micro-environment. We developed polymethylmethacrylate-based microfluidic chips for studying cellular responses under single or coexisting chemical/electrical/shear stress stimuli.

Microfluidic devices are capable of creating a precise and controllable cellular micro-environment of pH, temperature, salt concentration, and other ...

The overall goal of this procedure is to design and fabricate microfluidic devices for observing how cells respond to environmental stimuli.This method can help answer key questions in the cell biology and biomedical engineering.Such as how cells responses under different environmental stimuli including chemicals, shear stresses, and electric field.The main advantage of this technique is that tubes are easily to be fabricated and assembled.And this these microfludic devices may make the in-vivo condition with high superb capabilities.Demonstrating the procedure will be Tzu-Yuan Chou, an undergraduate student from my lab, and Hsien-San Hou, a post-staff from Dr.Julian Chung's lab.To begin, turn on the carbon dioxide laser scriber and check it's connection to the computer.Then load up a pre-drawn Christmas tree pattern, like one of the patterns shown here into the scriber.Next, place a PMMA sheet or piece of double-sided tape on top of the stage of the scriber.Adjust the focus of the carbon dioxide laser using the calibration bar and the visible helium neon laser.Then scribe the pattern onto the substrate.When finished, pick up the pattern substrate, remove the unwanted pieces, and use a stream of nitrogen to clean the surface of any remaining debris.Repeat this process for each component of the chip.Assemble the chemical shear stress microfluidic chip.To accomplish this, attach three sheets of the chemical shear stress patterned PMMA sheets using two pieces of scribed double-sided tape.Use super glue to attach a acrylic adapters with screw threads in the middle to the top-most PMMA layer of the chip by aligning the screw threads and the holes.These adapters will serve as medium inlets outlets and salt bridge connectors.Then add one more piece of the 07 mm thick double-sided tape to the bottom of the chip, and attach the chip to a 10 cm diameter Petri dish.Once assembled, put the chip in a vacuum chamber for overnight.Now assemble the chemical-electric field chip.Attach the scribed PMMA sheet for the chemical-electric field chip with double-sided tape to a 10 cm diameter Petri dish.Prior to using the chips, expose them to UV for 30 minutes to sterilize them.Next, connect the inlets of the chips to 3 ml PBS-filled syringes via plastic tubes and finger-tight nuts.In the same manner, connect the outlets to a waste tube.Slowly depress the plunger on the syringe to prime the fluidic channels with PBS.Push the syringe back and forth to remove bubbles, then put the chips inside an incubator overnight.To setup the chemical-electric field chips, fill 3%agarous in in the tubular nuts to setup the salt bridges.Then place the silver silver chloride electrodes into the tubular nuts.Grow lung cancer CL1-5 cells in D-MEM supplemented with 10%FBS until they reach 90%confluence.Then aspirate the medium.Wash the cells once with pre-warmed PBS.And add 2 ml of a 05%tripsin buffer solution to a 10 cm diameter plate.Place the cells back at 37

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Research

JoVE Journal

Bioengineering

A Microfluidic-based Hydrodynamic Trap for Single Particles

The ability to confine and manipulate single particles in free solution is a key enabling technology for fundamental and applied science. Methods for particle trapping based on optical, magnetic, electrokinetic, and acoustic techniques have led to major advancements in physics and biology ranging from the molecular to cellular level. In this article, we introduce a new microfluidic-based technique for particle trapping and manipulation based solely on hydrodynamic fluid flow. Using this method, we demonstrate trapping of micro- and nano-scale particles in aqueous solutions for long time scales. The hydrodynamic trap consists of an integrated microfluidic device with a cross-slot channel geometry where two opposing laminar streams converge, thereby generating a planar extensional flow with a fluid stagnation point (zero-velocity point). In this device, particles are confined at the trap center by active control of the flow field to maintain particle position at the fluid stagnation point. In this manner, particles are effectively trapped in free solution using a feedback control algorithm implemented with a custom-built LabVIEW code. The control algorithm consists of image acquisition for a particle in the microfluidic device, followed by particle tracking, determination of particle centroid position, and active adjustment of fluid flow by regulating the pressure applied to an on-chip pneumatic valve using a pressure regulator. In this way, the on-chip dynamic metering valve functions to regulate the relative flow rates in the outlet channels, thereby enabling fine-scale control of stagnation point position and particle trapping. The microfluidic-based hydrodynamic trap exhibits several advantages as a method for particle trapping. Hydrodynamic trapping is possible for any arbitrary particle without specific requirements on the physical or chemical properties of the trapped object. In addition, hydrodynamic trapping enables confinement of a "single" target object in concentrated or crowded particle suspensions, which is difficult using alternative force field-based trapping methods. The hydrodynamic trap is user-friendly, straightforward to implement and may be added to existing microfluidic devices to facilitate trapping and long-time analysis of particles. Overall, the hydrodynamic trap is a new platform for confinement, micromanipulation, and observation of particles without surface immobilization and eliminates the need for potentially perturbative optical, magnetic, and electric fields in the free-solution trapping of small particles.

In this article, we present a microfluidic-based method for particle confinement based on hydrodynamic flow. We demonstrate stable particle trapping at a fluid stagnation point using a feedback control mechanism, thereby enabling confinement and micromanipulation of arbitrary particles in an integrated microdevice.

The ability to confine and manipulate single particles in free solution is a key enabling technology for fundamental and applied science.  Methods for ...

Simple Microfluidic Devices for in vivo Imaging of C. elegans, Drosophila and Zebrafish

Micro fabricated fluidic devices provide an accessible micro-environment for in vivo studies on small organisms. Simple fabrication processes are available for microfluidic devices using soft lithography techniques 1-3. Microfluidic devices have been used for sub-cellular imaging 4,5, in vivo laser microsurgery 2,6 and cellular imaging 4,7. In vivo imaging requires immobilization of organisms. This has been achieved using suction 5,8, tapered channels 6,7,9, deformable membranes 2-4,10, suction with additional cooling 5, anesthetic gas 11, temperature sensitive gels 12, cyanoacrylate glue 13 and anesthetics such as levamisole 14,15. Commonly used anesthetics influence synaptic transmission 16,17 and are known to have detrimental effects on sub-cellular neuronal transport 4. In this study we demonstrate a membrane based poly-dimethyl-siloxane (PDMS) device that allows anesthetic free immobilization of intact genetic model organisms such as Caenorhabditis elegans (C. elegans), Drosophila larvae and zebrafish larvae. These model organisms are suitable for in vivo studies in microfluidic devices because of their small diameters and optically transparent or translucent bodies. Body diameters range from ~10 &mu;m to ~800 &mu;m for early larval stages of C. elegans and zebrafish larvae and require microfluidic devices of different sizes to achieve complete immobilization for high resolution time-lapse imaging. These organisms are immobilized using pressure applied by compressed nitrogen gas through a liquid column and imaged using an inverted microscope. Animals released from the trap return to normal locomotion within 10 min.
We demonstrate four applications of time-lapse imaging in C. elegans namely, imaging mitochondrial transport in neurons, pre-synaptic vesicle transport in a transport-defective mutant, glutamate receptor transport and Q neuroblast cell division. Data obtained from such movies show that microfluidic immobilization is a useful and accurate means of acquiring in vivo data of cellular and sub-cellular events when compared to anesthetized animals (Figure 1J and 3C-F 4).
Device dimensions were altered to allow time-lapse imaging of different stages of C. elegans, first instar Drosophila larvae and zebrafish larvae. Transport of vesicles marked with synaptotagmin tagged with GFP (syt.eGFP) in sensory neurons shows directed motion of synaptic vesicle markers expressed in cholinergic sensory neurons in intact first instar Drosophila larvae. A similar device has been used to carry out time-lapse imaging of heartbeat in ~30 hr post fertilization (hpf) zebrafish larvae. These data show that the simple devices we have developed can be applied to a variety of model systems to study several cell biological and developmental phenomena in vivo.

Simple Microfluidic Devices for in vivo Imaging of C. elegans, Drosophila and Zebrafish

A simple microfluidic device has been developed to perform anesthetic free in vivo imaging of C. elegans, intact Drosophila larvae and zebrafish larvae. The device utilizes a deformable PDMS membrane to immobilize these model organisms in order to perform time lapse imaging of numerous processes such as heart beat, cell division and sub-cellular neuronal transport. We demonstrate the use of this device and show examples of different types of data collected from different model systems.

Micro fabricated fluidic devices provide an accessible micro-environment for in vivo studies on small organisms. Simple fabrication processes are ...

Microfluidic Mixers for Studying Protein Folding

The process by which a protein folds into its native conformation is highly relevant to biology and human health yet still poorly understood. One reason for this is that folding takes place over a wide range of timescales, from nanoseconds to seconds or longer, depending on the protein1. Conventional stopped-flow mixers have allowed measurement of folding kinetics starting at about 1 ms. We have recently developed a microfluidic mixer that dilutes denaturant ~100-fold in ~8 &mu;s2. Unlike a stopped-flow mixer, this mixer operates in the laminar flow regime in which turbulence does not occur. The absence of turbulence allows precise numeric simulation of all flows within the mixer with excellent agreement to experiment3-4.
Laminar flow is achieved for Reynolds numbers Re &le;100. For aqueous solutions, this requires micron scale geometries. We use a hard substrate, such as silicon or fused silica, to make channels 5-10 &mu;m wide and 10 &mu;m deep (See Figure 1). The smallest dimensions, at the entrance to the mixing region, are on the order of 1 &mu;m in size. The chip is sealed with a thin glass or fused silica coverslip for optical access. Typical total linear flow rates are ~1 m/s, yielding Re~10, but the protein consumption is only ~0.5 nL/s or 1.8 &mu;L/hr. Protein concentration depends on the detection method: For tryptophan fluorescence the typical concentration is 100 &mu;M (for 1 Trp/protein) and for FRET the typical concentration is ~100 nM.
The folding process is initiated by rapid dilution of denaturant from 6 M to 0.06 M guanidine hydrochloride. The protein in high denaturant flows down a central channel and is met on either side at the mixing region by buffer without denaturant moving ~100 times faster (see Figure 2). This geometry causes rapid constriction of the protein flow into a narrow jet ~100 nm wide. Diffusion of the light denaturant molecules is very rapid, while diffusion of the heavy protein molecules is much slower, diffusing less than 1 &mu;m in 1 ms. The difference in diffusion constant of the denaturant and the protein results in rapid dilution of the denaturant from the protein stream, reducing the effective concentration of the denaturant around the protein. The protein jet flows at a constant rate down the observation channel and fluorescence of the protein during folding can be observed using a scanning confocal microscope5.

In this work we explain the fabrication and use of a microfluidic mixer capable of mixing two solutions in ~8 &mu;s. We also demonstrate the use of these mixers with spectroscopic detection using UV fluorescence and fluorescence resonance energy transfer (FRET).

The process by which a protein folds into its native conformation is highly relevant to biology and human health yet still poorly understood. One reason ...

A Microfluidic Device for Studying Multiple Distinct Strains

The study of cell responses to environmental changes poses many experimental challenges: cells need to be imaged under changing conditions, often in a comparative manner. Multiwell plates are routinely used to compare many different strains or cell lines, but allow limited control over the environment dynamics. Microfluidic devices, on the other hand, allow exquisite dynamic control over the surrounding conditions, but it is challenging to image and distinguish more than a few strains in them. Here we describe a method to easily and rapidly manufacture a microfluidic device capable of applying dynamically changing conditions to multiple distinct yeast strains in one channel. The device is designed and manufactured by simple means without the need for soft lithography. It is composed of a Y-shaped flow channel attached to a second layer harboring microwells. The strains are placed in separate microwells, and imaged under the exact same dynamic conditions. We demonstrate the use of the device for measuring protein localization responses to pulses of nutrient changes in different yeast strains.

We present a simple method to produce microfluidic devices capable of applying similar dynamic conditions to multiple distinct strains, without the need for a clean room or soft lithography.

The study of cell responses to environmental changes poses many experimental challenges: cells need to be imaged under changing conditions, often in a ...

Layer-by-layer Collagen Deposition in Microfluidic Devices for Microtissue Stabilization

Although microfluidics provides exquisite control of the cellular microenvironment, culturing cells within microfluidic devices can be challenging. 3D culture of cells in collagen type I gels helps to stabilize cell morphology and function, which is necessary for creating microfluidic tissue models in microdevices. Translating traditional 3D culture techniques for tissue culture plates to microfluidic devices is often difficult because of the limited channel dimensions. In this method, we describe a technique for modifying native type I collagen to generate polycationic and polyanionic collagen solutions that can be used with layer-by-layer deposition to create ultrathin collagen assemblies on top of cells cultured in microfluidic devices. These thin collagen layers stabilize cell morphology and function, as shown using primary hepatocytes as an example cell, allowing for the long term culture of microtissues in microfluidic devices.

The creation of functional microtissues within microfluidic devices requires the stabilization of cell phenotypes by adapting traditional cell culture techniques to the limited spatial dimensions in microdevices. Modification of collagen allows the layer-by-layer deposition of ultrathin collagen assemblies that can stabilize primary cells, such as hepatocytes, as microfluidic tissue models.

Although microfluidics provides exquisite control of the cellular microenvironment, culturing cells within microfluidic devices can be challenging. 3D ...

Using Adhesive Patterning to Construct 3D Paper Microfluidic Devices

We demonstrate the use of patterned aerosol adhesives to construct both planar and nonplanar 3D paper microfluidic devices. By spraying an aerosol adhesive through a metal stencil, the overall amount of adhesive used in assembling paper microfluidic devices can be significantly reduced. We show on a simple 4-layer planar paper microfluidic device that the optimal adhesive application technique and device construction style depends heavily on desired performance characteristics. By moderately increasing the overall area of a device, it is possible to dramatically decrease the wicking time and increase device success rates while also reducing the amount of adhesive required to keep the device together. Such adhesive application also causes the adhesive to form semi-permanent bonds instead of permanent bonds between paper layers, enabling single-use devices to be non-destructively disassembled after use. Nonplanar 3D origami devices also benefit from the semi-permanent bonds during folding, as it reduces the likelihood that unrelated faces may accidently stick together. Like planar devices, nonplanar structures see reduced wicking times with patterned adhesive application vs uniformly applied adhesive.

We demonstrate the use of patterned aerosol adhesives to construct 3D paper microfluidic devices. This method of adhesive application forms semi-permanent bonds between layers, enabling single-use devices to be non-destructively disassembled after use and to ease folding complex nonplanar structures.

We demonstrate the use of patterned aerosol adhesives to construct both planar and nonplanar 3D paper microfluidic devices. By spraying an aerosol ...

A Method for Evaluating Timeliness and Accuracy of Volitional Motor Responses to Vibrotactile Stimuli

Artificial sensory feedback (ASF) systems can be used to compensate for lost proprioception in individuals with lower-limb impairments. Effective design of these ASF systems requires an in-depth understanding of how the parameters of specific feedback mechanism affect user perception and reaction to stimuli. This article presents a method for applying vibrotactile stimuli to human participants and measuring their response. Rotating mass vibratory motors are placed at pre-defined locations on the participant's thigh, and controlled through custom hardware and software. The speed and accuracy of participants' volitional responses to vibrotactile stimuli are measured for researcher-specified combinations of motor placement and vibration frequency. While the protocol described here uses push-buttons to collect a simple binary response to the vibrotactile stimuli, the technique can be extended to other response mechanisms using inertial measurement units or pressure sensors to measure joint angle and weight bearing ratios, respectively. Similarly, the application of vibrotactile stimuli can be explored for body segments other than the thigh.

This article describes a technique for applying vibrotactile stimuli to the thigh of a human participant, and measuring the accuracy and reaction time of the participant&#39;s volitional response for various combinations of stimulation location and frequency.

Artificial sensory feedback (ASF) systems can be used to compensate for lost proprioception in individuals with lower-limb impairments.  Effective design ...

Multi-step Variable Height Photolithography for Valved Multilayer Microfluidic Devices

Microfluidic systems have enabled powerful new approaches to high-throughput biochemical and biological analysis. However, there remains a barrier to entry for non-specialists who would benefit greatly from the ability to develop their own microfluidic devices to address research questions. Particularly lacking has been the open dissemination of protocols related to photolithography, a key step in the development of a replica mold for the manufacture of polydimethylsiloxane (PDMS) devices. While the fabrication of single height silicon masters has been explored extensively in literature, fabrication steps for more complicated photolithography features necessary for many interesting device functionalities (such as feature rounding to make valve structures, multi-height single-mold patterning, or high aspect ratio definition) are often not explicitly outlined. 
Here, we provide a complete protocol for making multilayer microfluidic devices with valves and complex multi-height geometries, tunable for any application. These fabrication procedures are presented in the context of a microfluidic hydrogel bead synthesizer and demonstrate the production of droplets containing polyethylene glycol (PEG diacrylate) and a photoinitiator that can be polymerized into solid beads. This protocol and accompanying discussion provide a foundation of design principles and fabrication methods that enables development of a wide variety of microfluidic devices. The details included here should allow non-specialists to design and fabricate novel devices, thereby bringing a host of recently developed technologies to their most exciting applications in biological laboratories.

Multilayer microfluidic devices often involve the fabrication of master molds with complex geometries for functionality. This article presents a complete protocol for multi-step photolithography with valves and variable height features tunable to any application. As a demonstration, we fabricate a microfluidic droplet generator capable of producing hydrogel beads.

Microfluidic systems have enabled powerful new approaches to high-throughput biochemical and biological analysis. However, there remains a barrier to ...

Fabrication of Three-dimensional Paper-based Microfluidic Devices for Immunoassays

Paper wicks fluids autonomously due to capillary action. By patterning paper with hydrophobic barriers, the transport of fluids can be controlled and directed within a layer of paper. Moreover, stacking multiple layers of patterned paper creates sophisticated three-dimensional microfluidic networks that can support the development of analytical and bioanalytical assays. Paper-based microfluidic devices are inexpensive, portable, easy to use, and require no external equipment to operate. As a result, they hold great promise as a platform for point-of-care diagnostics. In order to properly evaluate the utility and analytical performance of paper-based devices, suitable methods must be developed to ensure their manufacture is reproducible and at a scale that is appropriate for laboratory settings. In this manuscript, a method to fabricate a general device architecture that can be used for paper-based immunoassays is described. We use a form of additive manufacturing (multi-layer lamination) to prepare devices that comprise multiple layers of patterned paper and patterned adhesive. In addition to demonstrating the proper use of these three-dimensional paper-based microfluidic devices with an immunoassay for human chorionic gonadotropin (hCG), errors in the manufacturing process that may result in device failures are discussed. We expect this approach to manufacturing paper-based devices will find broad utility in the development of analytical applications designed specifically for limited-resource settings.

We detail a method to fabricate three-dimensional paper-based microfluidic devices for use in the development of immunoassays. Our approach to device assembly is a type of multilayer, additive manufacturing. We demonstrate a sandwich immunoassay to provide representative results for these types of paper-based devices.

Paper wicks fluids autonomously due to capillary action. By patterning paper with hydrophobic barriers, the transport of fluids can be controlled and ...

Polydimethylsiloxane-polycarbonate Microfluidic Devices for Cell Migration Studies Under Perpendicular Chemical and Oxygen Gradients

This paper reports a microfluidic device made of polydimethylsiloxane (PDMS) with an embedded polycarbonate (PC) thin film to study cell migration under combinations of chemical and oxygen gradients. Both chemical and oxygen gradients can greatly affect cell migration in vivo; however, due to technical limitations, very little research has been performed to investigate their effects in vitro. The device developed in this research takes advantage of a series of serpentine-shaped channels to generate the desired chemical gradients and exploits a spatially confined chemical reaction method for oxygen gradient generation. The directions of the chemical and oxygen gradients are perpendicular to each other to enable straightforward migration result interpretation. In order to efficiently generate the oxygen gradients with minimal chemical consumption, the embedded PC thin film is utilized as a gas diffusion barrier. The developed microfluidic device can be actuated by syringe pumps and placed into a conventional cell incubator during cell migration experiments to allow for setup simplification and optimized cell culture conditions. In cell experiments, we used the device to study migrations of adenocarcinomic human alveolar basal epithelial cells, A549, under combinations of chemokine (stromal cell-derived factor, SDF-1&#945;) and oxygen gradients. The experimental results show that the device can stably generate perpendicular chemokine and oxygen gradients and is compatible with cells. The migration study results indicate that oxygen gradients may play an essential role in guiding cell migration, and cellular behavior under combinations of gradients cannot be predicted from those under single gradients. The device provides a powerful and practical tool for researchers to study interactions between chemical and oxygen gradients in cell culture, which can promote better cell migration studies in more in vivo-like microenvironments.

The control of chemical and oxygen gradients is essential for cell cultures. This paper reports a polydimethylsiloxane-polycarbonate (PDMS-PC) microfluidic device capable of reliably generating combinations of chemical and oxygen gradients for cell migration studies, which can be practically utilized in biological labs without sophisticated instrumentation.

This paper reports a microfluidic device made of polydimethylsiloxane (PDMS) with an embedded polycarbonate (PC) thin film to study cell migration under ...