The authors thank Professor Tang K. Tang, Institute of Biomedical Sciences, Academia Sinica, for his assistance in providing mouse neural stem and progenitor cells (mNPCs). The authors also thank Professor Tang K. Tang and Ms. Ying-Shan Lee, for their valuable discussion on the differentiation of mNPCs.

1. Design and fabrication of the MOE chip
<ol>
	<li>Draw patterns for individual polymethyl methacrylate (PMMA) layers and the double-sided tape using appropriate software (Figure 1A, Table of Materials). Cut both the PMMA sheets and the double-sided tape with a CO2 laser machine scriber (Figure 1B).
	<ol>
		<li>Switch on the CO2 laser scriber and connect it to a personal computer. Open the designed pattern file using the software.</li>
		<li>Place the PMMA sheets (275 mm x 400 mm) or double-sided tape (210 mm x 297 mm) on the platform of the laser scriber (Figure 2A). Focus the laser onto the surface of the PMMA sheets or the double-sided tape using the auto-focus tool.</li>
		<li>Select the laser scriber as the printer, and then &#34;print&#34; the pattern using the laser scriber to start the direct ablation on the PMMA sheet or double-sided tape and obtain individual patterns on the PMMA sheet or tape (Figure 2B).</li>
	</ol>
	</li>
	<li>Remove the protective film from the PMMA sheets, and clean the surface using nitrogen gas. 
	NOTE: The drawing of the PMMA pattern and direct machining of the PMMA sheet were performed according to a previous report17.</li>
	<li>For bonding together multiple layers of PMMA sheets, stack three pieces of 1 mm PMMA sheets (Layers 1, 2, and 3), and bond them under a pressure of 5 kg/cm2 in a thermal bonder for 30 min at 110 &#176;C to form the flow/electrical stimulation channel assembly (Figure 2C). 
	NOTE: Different batches of commercially obtained PMMA sheet have slightly different glass transition temperature (Tg). The optimal bonding temperature needs to be tested at 5 &#176;C increments close to the Tg.</li>
	<li>Adhere 12 pieces of adaptors to the individual openings in Layer 1 of the MOE chip assembly with fast-acting cyanoacrylate glue. 
	NOTE: The adaptors are made of PMMA by injection molding. The flat surfaces at the bottom are for connecting to the MOE chip. The adaptors bearing 1/4W-28 female screw thread are for connecting white finger-tight plugs, flat bottom connectors, or Luer adaptors. Be careful when using fast-acting cyanoacrylate glue. Avoid splashing into the eyes.</li>
	<li>Disinfect the 1 mm PMMA substrates (Layers 1-3), the double-sided tape (Layer 4), and the 3 mm optical grade PMMA (Layer 5) using ultraviolet (UV) irradiation for 30 min before assembling the chip (Figure 1A).</li>
	<li>Adhere the 1 mm PMMA substrates (Layers 1-3) on the 3 mm optical grade PMMA (Layer 5) with the double-sided tape (Layer 4) to complete the PMMA assembly (Layers 1-5) (Figure 1A).</li>
	<li>Prepare the clean cover glass for the assembly on the chip.
	<ol>
		<li>Fill a ten-fold dilution of the detergent in a staining jar (see the Table of Materials), and clean the cover glass in this detergent using an ultrasonic cleaner for 15 min.</li>
		<li>Thoroughly rinse the staining jar under running tap water to remove all traces of the detergent.</li>
		<li>Continue rinsing with distilled water to remove all traces of tap water, and repeat step 1.7.2 two times.</li>
		<li>Dry the cleaned cover glass by blowing it with nitrogen gas.</li>
	</ol>
	</li>
	<li>Disinfect the PMMA assembly (Layers 1-5), the double-sided tape (Layer 6), and the cover glass (Layer 7) using UV irradiation inside a biosafety cabinet for 30 min before assembling the chip (Figure 1A).</li>
	<li>Adhere the cleaned cover glass (Layer 7) to the PMMA assembly (Layers 1-5) with the double-sided tape (Layer 6) (Figure 1A).</li>
	<li>Incubate the MOE chip in a vacuum chamber overnight; use the MOE chip assembly for subsequent procedures (Figure 3).</li>
</ol>
2. Coating poly-L-lysine (PLL) on the substrate in the cell culture regions
<ol>
	<li>Prepare the polytetrafluoroethylene tube, flat-bottom connector, cone connector, cone-Luer adaptor, white finger-tight plug (also called stopper), Luer adaptor, Luer lock syringe, and black rubber bung (Figure 4A, Table of Materials). Sterilize all the above components in an autoclave at 121 &#176;C for 30 min.</li>
	<li>Seal the openings of the agar bridge adaptors (Figure 1A) with the white finger-tight plugs. Connect the flat-bottom connector to the MOE chip assembly via the medium inlet and outlet adaptors (Figure 4B). Connect the cone-Luer adaptor to the 3-way stopcocks.</li>
	<li>Add 2 mL of 0.01% PLL solution using a 3 mL syringe that connects to the 3-way stopcock of the medium inlet (Figure 4B-<img alt="Equation 1" src="/files/ftp_upload/61917/1.png" style="vertical-align: middle;" />).</li>
	<li>Connect an empty 3 mL syringe to the 3-way stopcock of the medium outlet (Figure 4B-<img alt="Equation 2" src="/files/ftp_upload/61917/2.png" style="vertical-align: middle;" />).</li>
	<li>Fill the cell culture regions with the PLL solution. Manually pump the coating solution back and forth slowly. Close the two 3-way stopcocks to seal the solution inside the culture regions.</li>
	<li>Incubate the MOE chip at 37 &#176;C overnight in an incubator filled with 5% CO2 atmosphere.</li>
</ol>
3. Preparation of the salt bridge network
<ol>
	<li>Following step 2.6, open the two 3-way stopcocks and flush away the bubbles in the channels by manually pumping the coating solution back and forth in the channel using the two syringes.</li>
	<li>Draw 3 mL of complete medium (stem cell maintenance medium consisting of Dulbecco&#39;s modified Eagle&#39;s medium/Ham&#39;s nutrient mixture F-12 (DMEM/F12), 2% B-27 supplement, 20 ng/mL EGF, and 20 ng/mL bFGF) into a 3 mL syringe that connects to the 3-way stopcock of the medium inlet (Figure 4B-<img alt="Equation 1" src="/files/ftp_upload/61917/1.png" style="vertical-align: middle;" />&#160;and Figure 4B-<img alt="Equation 3" src="/files/ftp_upload/61917/3.png" style="vertical-align: middle;" />).</li>
	<li>Add 3 mL of complete medium to replace the coating solution in the cell culture regions. Connect an empty 5 mL syringe to the 3-way stopcock of the medium outlet (Figure 4B-<img alt="Equation 4" src="/files/ftp_upload/61917/4.png" style="vertical-align: middle;" />).</li>
	<li>Prepare the salt bridge network (Figure 5).
	<ol>
		<li>Cut the black rubber bung to produce a gap, and insert the silver (Ag)/silver chloride (AgCl) electrodes through the black rubber bung and into the Luer lock syringe (Figure 4A).</li>
		<li>Replace the white fingertight plug with the Luer adaptor, and inject 3% hot agarose to fill the Luer adaptor. 
		NOTE: For the preparation of the hot agarose, dissolve 3 g of agarose powder in 100 mL of phosphate-buffered saline (PBS) and sterilize in an autoclave at 121 &#176;C for 30 min.</li>
		<li>Connect the Luer lock syringe to the Luer adaptor. Inject 3% hot agarose through the black rubber bung to fill the Luer lock syringe using the syringe with needle. Allow 10 to 20 mins for the agarose to cool down and solidify. 
		NOTE: In order to increase the volume capacity of the agarose, the Luer lock syringe is mounted on the Luer adaptor (Figure 4 and Figure 5). Then, the large electrodes are inserted into the Luer lock syringe. The electrode is capable of providing a stable electrical stimulation for the long-term experiment.</li>
	</ol>
	</li>
</ol>
4. Preparation of mNPCs
<ol>
	<li>Culture the mNPCs1 in the complete medium in a 25T cell culture flask at 37 &#176;C in an incubator filled with 5% CO2 atmosphere. Subculture the cells every 3-4 days, and perform all experiments with cells that have undergone 3-8 passages from the original source.</li>
	<li>Transfer the cell suspension to a 15 mL conical tube, and spin-down the neurospheres at 100 &#215; g for 5 min. Aspirate the supernatant, and wash the neurospheres with 1x Dulbecco&#39;s PBS (DPBS). Spin-down the neurospheres at 100 &#215; g for 5 min.</li>
	<li>Aspirate the 1x DPBS and then resuspend the neurospheres in the complete medium. Mix thoroughly and gently.</li>
	<li>Add 1 mL of the neurosphere suspension using a 1 mL syringe that connects to the 3-way stopcock of the outlet (Figure 4B-<img alt="Equation 2" src="/files/ftp_upload/61917/2.png" style="vertical-align: middle;" />).</li>
</ol>
5. Setup of the microfluidic system for DC pulse stimulation (Figure 6)
<ol>
	<li>Install the cell-seeded MOE chip onto the transparent ITO heater that is fastened on a programmable X-Y-Z motorized stage. 
	NOTE: The ITO surface temperature is controlled by a proportional-integral-derivative controller and maintained at 37 &#176;C. A K-type thermocouple is clamped between the chip and the ITO heater to monitor the temperature of the cell culture regions within the chip. The MOE chip is installed on a programmable X-Y-Z motorized stage and is suitable for automatic time-lapse image acquisition at individual channel sections. The fabrication of the ITO heater and the setup of the cell culture heating system have been described previously18,19.</li>
	<li>Infuse the mNPCs by manual pumping into the MOE chip via the medium outlet. Incubate the cell-seeded MOE chip on the 37 &#176;C ITO heater for 4 h.</li>
	<li>After 4 h, pump the complete medium through the MOE chip via the medium inlet at a flow rate of 20 &#181;L/h using a syringe pump. 
	NOTE: The mNPCs are grown and maintained in the chip for an additional 24 h before EF stimulation to allow cell attachment and growth. The waste liquid is collected in an empty 5 mL syringe connected to the 3-way stopcock of the outlet, shown as &#34;waste&#34; in Figure 6A. The MOE microfluidic system configuration is shown in Figure 6. This microfluidic system provides a continuous supply of nutrition to the cells. The complete fresh medium is continuously pumped into the MOE chip to maintain a constant pH value. Therefore, the cells can be cultured outside a CO2 incubator.</li>
	<li>Use electrical wires to connect an EF multiplexer to the MOE chip via the Ag/AgCl electrodes on the chip. Connect an EF multiplexer and a function generator to an amplifier to output square-wave DC pulses with a magnitude of 300 mV/mm at a frequency of 100 Hz at 50% duty cycles (50% time-on and 50% time-off) (Figure 6B).
	<ol>
		<li>Connect the electrical wires to the EF multiplexer. Connect the electrical wires to the MOE chip via the Ag/AgCl electrodes.</li>
		<li>Connect the EF multiplexer to the amplifier using electrical wires. Connect the function generator to the amplifier and the digital oscilloscope. 
		NOTE: The EF multiplexer is a circuit that includes the impedance of the culture chamber in the circuit and connects all individual chambers in a parallel electronic network. Each of the three culture chambers is electrically connected in serial to a variable resistor (Vr) and an ammeter (shown as &#181;A in Figure 6A) in the multiplexer. The electric current through each culture chamber is varied by controlling the Vr, and the current is shown on the corresponding ammeter. The electric field strength in each cell culture region was calculated by Ohm&#39;s Law, I= &#963;EA, where I is the electric current, &#963; (set as 1.38 S&#183;m-1 for DMEM/F1220) is the electrical conductivity of the culture medium, E is the electric field, and A is the cross-sectional area of the electrotactic chamber. For the cell culture region dimension shown in Figure 1, the electric current is ~87 mA and ~44 mA for DC and DC pulse at 50% duty cycle, respectively.</li>
	</ol>
	</li>
	<li>Subject the mNPCs to square DC pulses with a magnitude of 300 mV/mm at the frequency of 100 Hz for 48h. Continuously pump the complete medium at a rate of 10 &#181;L/h to supply adequate nutrition to the cells and to maintain a constant pH value in the medium.</li>
</ol>
6. Immunofluorescence assays of mNPCs after pulsed DC stimulation
NOTE: In this step, all reagent is pumped via the medium inlet using a syringe pump.
<ol>
	<li>After 3, 7, or 14 days in vitro (DIV) culturing after seeding1, wash the cells with 1x PBS at a flow rate of 25 &#181;L/min for 20 min.</li>
	<li>Fix the cells with 4% paraformaldehyde (PFA). Pump 4% PFA into the chip at a flow rate of 25 &#181;L/min for 20 min to replace the 1x PBS. To replace the 4% PFA, wash the cells with 1x PBS at a flow rate of 25 &#181;L/min for 20 min.</li>
	<li>Pump 0.1% Triton X-100 into the chip at a flow rate of 50 &#181;L/min for 6 min to permeabilize the cells. Reduce the flow rate to 50 &#181;L/h for an additional 30 min to react with the cells. To replace the 0.1% Triton X-100, wash the cells with 1x PBS at a flow rate of 50 &#181;L/min for 6 min.</li>
	<li>Block the cells with PBS containing 1% bovine serum albumin (BSA) to reduce nonspecific antibody binding. Pump 1% BSA into the chip at a flow rate of 50 &#181;L/min for 6 min. Reduce the flow rate to 100 &#181;L/h and pump for 1 h.</li>
	<li>Pump the antibodies for double immunostaining into the chip at a flow rate of 50 &#181;L/min for 6 min, and incubate the chip for 18 h at 4 &#176;C. Wash the cells with 1x PBS at a flow rate of 50 &#181;L/min for 15 min.</li>
	<li>Pump the Alexa Fluor-conjugated secondary antibodies into the chip at a flow rate of 50 &#181;L/min for 6 min. Reduce the flow rate to 50 &#181;L/h, and pump the antibodies for 1 h at room temperature in the dark. Wash the cells with 1x PBS at a flow rate of 50 &#181;L/min for 15 min.</li>
	<li>For nuclear staining, pump Hoechst 33342 into the chip at a flow rate of 20 &#181;L/min for 10 min at room temperature in the dark. Wash the cells with 1x PBS at a flow rate of 50 &#181;L/min for 15 min.</li>
	<li>After immunostaining, observe the cells using a confocal fluorescence microscope.</li>
</ol>
7. Image analysis and data processing
<ol>
	<li>Analyze the fluorescent images using software with built-in measurement tools (see the Table of Materials).</li>
	<li>Compare the Hoechst-counterstained nuclei (total number of cells) in the control and treatment groups, and calculate the percentage of cells expressing each phenotypic marker.</li>
</ol>

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The authors have nothing to disclose.

During the fabrication of the MOE chip, the adaptors are attached to the Layer 1 of the MOE chip with fast-acting cyanoacrylate glue. The glue is applied to 4 corners of the adaptors, and then pressure is applied evenly over the adaptors. Excess amount of glue must be avoided to ensure complete polymerization of the glue. Moreover, the completed MOE chip assembly is incubated in a vacuum chamber. This step helps to remove the bubbles between the PMMA layer, the double-sided tape, and the cover glass.
<p class="jove_c...

Neural precursor cells (NPCs, also known as neural stem and progenitor cells) can be as a promising candidate for neurodegenerative therapeutic strategy1. The undifferentiated NPCs have self-renewal capacity, multi-potency, and proliferative ability2,3. A previous study has reported that the extracellular matrix and molecular mediators regulate differentiation of NPC. The epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) promote NPC proliferation, thus maintaining the undifferentiated state4.
Previous studies have reported that electrical stimulation can regulate cell physiologic activities such as division5, migration6,7,8, differentiation1,9,10, and cell death11. Electric fields (EFs) play vital roles in the development and regeneration of the central nervous system development12,13,14. From 2009 to 2019, this laboratory has investigated cellular responses to the application of EF in the microfluidic system1,6,7,8,15,16,17. A multichannel, optically transparent, electrotactic (MOE) chip was designed to be suitable for immunofluorescence staining for confocal microscopy. The chip had high optical transparency and good durability and allowed the simultaneous conduct of three independent stimulation experiments and several immunostained conditions in a single study. The microfluidic system is beneficial in simplifying the overall experimental setup and, in turn, the reagent and sample consumption. This paper describes the development of a microfluidic cell culture system that was used for a long-term cell differentiation study.

<table><tbody><tr><td>1 mm PMMA substrates (Layers 1-3)</td><td>BHT</td><td>K2R20</td><td>Polymethyl methacrylate (PMMA), http://www.bothharvest.com/zh-tw/product-421076/Optical-PMMA-Non-Coated-BHT-K2Rxx-xx=-thickness-choices.html</td></tr><tr><td>15 mL plastic tube</td><td>Protech Technology Enterprise Co., Ltd</td><td>CT-15-PL-TW</td><td>Conical bottomed tube with cap, assembled, presterilized</td></tr><tr><td>3 mL syringe</td><td>TERUMO</td><td>DVR-3413</td><td>3 mL oral syringes, without needle</td></tr><tr><td>3 mm optical grade PMMA (Layer 5)</td><td>CHI MEI Corporation</td><td>ACRYPOLY PMMA Sheet</td><td>Optical grade PMMA</td></tr><tr><td>3-way stopcock</td><td>NIPRO</td><td>NCN-3L</td><td>Sterile disposable 3-way stopcock</td></tr><tr><td>5 mL syringe</td><td>TERUMO</td><td>DVR-3410</td><td>5 mL oral syringes, without needle</td></tr><tr><td>Adaptor</td><td>Dong Zhong Co., Ltd.</td><td>Customized</td><td>PMMA adaptor</td></tr><tr><td>Agarose</td><td>Sigma-Aldrich</td><td>A9414</td><td>Agarose, low gelling temperature</td></tr><tr><td>Amplifier</td><td>A.A. Lab Systems Ltd</td><td>A-304</td><td>High voltage amplifier</td></tr><tr><td>AutoCAD software</td><td>Autodesk</td><td>Educational Version</td><td>Drafting</td></tr><tr><td>B-27 supplement</td><td>Gibco</td><td>12587-010</td><td>B-27 supplement (50x), minus vitamin A</td></tr><tr><td>Basic fibroblast growth factor (bFGF)&amp;nbsp;</td><td>Peprotech</td><td>AF-100-18B</td><td>Also called recombinant human FGF-basic</td></tr><tr><td>Black rubber bung</td><td>TERUMO</td><td>DVR-3413</td><td>From 3 mL oral syringes, without needle</td></tr><tr><td>Bovine serum albumin (BSA)</td><td>Sigma-Aldrich</td><td>B4287</td><td>Blocking reagent&amp;nbsp;</td></tr><tr><td>Centrifuge</td><td>HSIANGTAI</td><td>CV2060</td><td>Centrifuge</td></tr><tr><td>CO&lt;sub&gt;2&lt;/sub&gt; laser scriber</td><td>Laser Tools and Technics Corp.&amp;nbsp;</td><td>ILS-II</td><td>Purchased from http://www.lttcorp.com/index.htm</td></tr><tr><td>Cone connector</td><td>IDEX Health &amp;amp; Science</td><td>F-120X</td><td>One-piece fingertight 10-32 coned, for 1/16&quot; OD natural</td></tr><tr><td>Cone-Luer adaptor</td><td>IDEX Health &amp;amp; Science</td><td>P-659</td><td>Luer Adapter 10-32 Female to Female Luer, PEEK</td></tr><tr><td>Confocal fluorescence microscope</td><td>Leica Microsystems</td><td>TCS SP5</td><td>Leica TCS SP5 user manual, http://www3.unifr.ch/bioimage/wp-content/uploads/2013/10/User-Manual_TCS_SP5_V02_EN.pdf</td></tr><tr><td>Digital camera</td><td>OLYMPUS</td><td>E-330</td><td>Automatic time-lapse image acquisition</td></tr><tr><td>Digital oscilloscope</td><td>Tektronix</td><td>TDS2024</td><td>Measure voltage or current signals over time in an electronic circuit or component to display amplitude and frequency.</td></tr><tr><td>Double-sided tape</td><td>3M&amp;nbsp;</td><td>PET 8018</td><td>Purchased from http://en.thd.com.tw/</td></tr><tr><td>Dulbecco&amp;rsquo;s modified Eagle&amp;rsquo;s medium/Ham&#039;s nutrient mixture F-12 (DMEM/F12)</td><td>Gibco</td><td>12400024</td><td>DMEM/F-12, powder, HEPES</td></tr><tr><td>Dulbecco&#039;s phosphate-buffered saline (DPBS)</td><td>Gibco</td><td>21600010</td><td>DPBS, powder, no calcium, no magnesium</td></tr><tr><td>EF multiplexer</td><td>Asiatic Sky Co., Ltd.</td><td>Customized</td><td>Monitor and control the electric current in individual channels</td></tr><tr><td>Epidermal growth factor (EGF)</td><td>Peprotech</td><td>AF-100-15</td><td>Also called recombinant human EGF</td></tr><tr><td>Fast-acting cyanoacrylate glue</td><td>3M&amp;nbsp;</td><td>7004T</td><td>Strength instant adhesive (liquid)</td></tr><tr><td>Flat bottom connector</td><td>IDEX Health &amp;amp; Science</td><td>P-206</td><td>Flangeless male nut Delrin, 1/4-28 flat-bottom, for 1/16&quot; OD blue</td></tr><tr><td>Function generator</td><td>Agilent Technologies</td><td>33120A</td><td>High-performance 15 MHz synthesized&amp;nbsp;function generator&amp;nbsp;with built-in arbitrary waveform capability</td></tr><tr><td>Goat anti-mouse IgG H&amp;amp;L (Alexa Fluor 488)</td><td>Abcam</td><td>ab150117</td><td>Goat anti-mouse IgG H&amp;amp;L (Alexa Fluor 488) preadsorbed</td></tr><tr><td>Goat anti-rabbit IgG H&amp;amp;L (Alexa Fluor 555)</td><td>Abcam</td><td>ab150086</td><td>Goat polyclonal secondary antibody to rabbit IgG - H&amp;amp;L (Alexa Fluor 555), preadsorbed</td></tr><tr><td>Hoechst 33342</td><td>Invitrogen</td><td>H3570</td><td>Nuclear staining</td></tr><tr><td>ImageJ software</td><td>National Institutes of Health</td><td>1.48v</td><td>Analyze the fluorescent images&amp;nbsp;</td></tr><tr><td>Indium&amp;ndash;tin&amp;ndash;oxide (ITO) glass</td><td>Merck</td><td>300739</td><td>For ITO heater</td></tr><tr><td>Inverted phase contrast microscope</td><td>OLYMPUS</td><td>CKX41</td><td>For cell morphology observation</td></tr><tr><td>K-type thermocouple</td><td>Tecpel</td><td>TPK-02A</td><td>Temperature&amp;nbsp;thermocouples</td></tr><tr><td>Luer adapter</td><td>IDEX Health &amp;amp; Science</td><td>P618-01</td><td>Luer adapter female Luer to 1/4-28 male polypropylene</td></tr><tr><td>Luer lock syringe</td><td>TERUMO</td><td>DVR-3413</td><td>For agar salt bridges</td></tr><tr><td>Mouse anti-GFAP</td><td>eBioscience</td><td>14-9892</td><td>Astrocytes marker</td></tr><tr><td>Oligodendrocyte &amp;nbsp;marker&amp;nbsp; O4&amp;nbsp; antibody</td><td>R&amp;amp;D Systems</td><td>MAB1326</td><td>Oligodendrocytes marker</td></tr><tr><td>Paraformaldehyde (PFA)</td><td>Sigma-Aldrich</td><td>P6148</td><td>Fixing&amp;nbsp;agent</td></tr><tr><td>Phosphate buffered saline (PBS)</td><td>Basic Life</td><td>BL2651</td><td>Washing solution</td></tr><tr><td>Poly-L-Lysine (PLL)</td><td>SIGMA</td><td>P4707</td><td>Coating solution</td></tr><tr><td>Precision cover glasses thickness No. 1.5H</td><td>MARIENFELD</td><td>107242</td><td>https://www.marienfeld-superior.com/precision-cover-glasses-thickness-no-1-5h-tol-5-m.html</td></tr><tr><td>Programmable X-Y-Z motorised stage</td><td>Tanlian Inc</td><td>Customized</td><td>Purchased from http://www.tanlian.tw/ndex.files/motort.htm</td></tr><tr><td>Proportional&amp;ndash;integral&amp;ndash;derivative (PID) controller</td><td>Toho Electronics</td><td>TTM-J4-R-AB</td><td>Temperature controller&amp;nbsp;</td></tr><tr><td>PTFE tube</td><td>Professional Plastics Inc. Taiwan Branch</td><td>Outer diameter 1/16 Inches</td><td>White translucent PTFE tubing</td></tr><tr><td>Rabbit anti-Tuj1</td><td>Abcam</td><td>ab18207</td><td>Neuron marker</td></tr><tr><td>Syringe pump</td><td>New Era Systems Inc</td><td>NE-1000</td><td>NE-1000 programmable single syringe pump</td></tr><tr><td>TFD4 detergent</td><td>FRANKLAB</td><td>TFD4</td><td>Cover glass cleaner</td></tr><tr><td>Thermal bonder</td><td>Kuan-MIN Tech Co.</td><td>Customized</td><td>Purchased from http://kmtco.com.tw/</td></tr><tr><td>Triton X-100</td><td>Sigma-Aldrich</td><td>T8787</td><td>Permeabilized solution</td></tr><tr><td>Ultrasonic cleaner</td><td>LEO</td><td>LEO-300S</td><td>Ultrasonic steri-cleaner</td></tr><tr><td>Vacuum chamber</td><td>DENG YNG INSTRUMENTS CO., Ltd.</td><td>DOV-30</td><td>Vacuum drying oven</td></tr><tr><td>White fingertight plug</td><td>IDEX Health &amp;amp; Science</td><td>P-316</td><td>1/4-28 Flat-Bottom, https://www.idex-hs.com/store/fluidics/fluidic-connections/plug-teflonr-pfa-1-4-28-flat-bottom.html</td></tr></tbody></table>

electric-field-induced neural precursor cell differentiation in microfluidic devices

Physiological electric fields (EF) play vital roles in cell migration, differentiation, division, and death. This paper describes a microfluidic cell culture system that was used for a long-term cell differentiation study using microscopy. The microfluidic system consists of the following major components: an optically transparent electrotactic chip, a transparent indium-tin-oxide (ITO) heater, a culture media-filling pump, an electrical power supply, a high-frequency power amplifier, an EF multiplexer, a programmable X-Y-Z motorized stage, and an inverted phase-contrast microscope equipped with a digital camera. The microfluidic system is beneficial in simplifying the overall experimental setup and, in turn, the reagent and sample consumption. This work involves the differentiation of neural stem and progenitor cells (NPCs) induced by direct current (DC) pulse stimulation. In the stem cell maintenance medium, the mouse NPCs (mNPCs) differentiated into neurons, astrocytes, and oligodendrocytes after the DC pulse stimulation. The results suggest that simple DC pulse treatment could control the fate of mNPCs and could be used to develop therapeutic strategies for nervous system disorders. The system can be used for cell culture in multiple channels, for long-term EF stimulation, for cell morphological observation, and for automatic time-lapse image acquisition. This microfluidic system not only shortens the required experimental time, but also increases the accuracy of control on the microenvironment.

The detailed configuration of the MOE chip is shown in Figure 1. The microfluidic chip provides a beneficial approach for reducing the experimental setup size, sample volume, and reagent volume. The MOE chip was designed to perform three independent EF stimulation experiments and several immunostaining conditions simultaneously in a single study (Figure 3). In addition, the MOE chip, which has a high optical transparency is suita...

Watch this Scientific Journal Video about Electric-Field-Induced Neural Precursor Cell Differentiation in Microfluidic Devices at JoVE.com

Electric-Field-Induced Neural Precursor Cell Differentiation in Microfluidic Devices

In this study, we present a protocol for the differentiation of neural stem and progenitor cells (NPCs) solely induced by direct current (DC) pulse stimulation in a microfluidic system.

Physiological electric fields (EF) play vital roles in cell migration, differentiation, division, and death. This paper describes a microfluidic cell ...

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Bioengineering

3.6K Views.  Academia Sinica. In this study, we present a protocol for the differentiation of neural stem and progenitor cells (NPCs) solely induced by direct current (DC) pulse stimulation in a microfluidic system.

Video: Electric-Field-Induced Neural Precursor Cell Differentiation in Microfluidic Devices

Electric Field-controlled Directed Migration of Neural Progenitor Cells in 2D and 3D Environments

Endogenous electric fields (EFs) occur naturally in vivo and play a critical role during tissue/organ development and regeneration, including that of the central nervous system1,2. These endogenous EFs are generated by cellular regulation of ionic transport combined with the electrical resistance of cells and tissues. It has been reported that applied EF treatment can promote functional repair of spinal cord injuries in animals and humans3,4. In particular, EF-directed cell migration has been demonstrated in a wide variety of cell types5,6, including neural progenitor cells (NPCs)7,8. Application of direct current (DC) EFs is not a commonly available technique in most laboratories. We have described detailed protocols for the application of DC EFs to cell and tissue cultures previously5,11. Here we present a video demonstration of standard methods based on a calculated field strength to set up 2D and 3D environments for NPCs, and to investigate cellular responses to EF stimulation in both single cell growth conditions in 2D, and the organotypic spinal cord slice in 3D. The spinal cordslice is an ideal recipient tissue for studying NPC ex vivo behaviours, post-transplantation, because the cytoarchitectonic tissue organization is well preserved within these cultures9,10. Additionally, this ex vivo model also allows procedures that are not technically feasible to track cells in vivo using time-lapse recording at the single cell level. It is critically essential to evaluate cell behaviours in not only a 2D environment, but also in a 3D organotypic condition which mimicks the in vivo environment. This system will allow high-resolution imaging using cover glass-based dishes in tissue or organ culture with 3D tracking of single cell migration in vitro and ex vivo and can be an intermediate step before moving onto in vivo paradigms.

This protocol demonstrates methods used to establish 2D and 3D environments in custom-designed electrotactic chambers, which can track cells in vivo/ex vivo using time-lapse recording at the single cell level, in order to investigate galvanotaxis/electrotaxis and other cellular responses to direct current (DC) electric fields (EFs).

Endogenous electric fields (EFs) occur naturally in vivo and play a critical role during tissue/organ development and regeneration, including that of the ...

Assessing Neural Stem Cell Motility Using an Agarose Gel-based Microfluidic Device

While microfluidic technology is reaching a new level of maturity for macromolecular assays, cell-based assays are still at an infant stage1. This is largely due to the difficulty with which one can create a cell-compatible and steady microenvironment using conventional microfabrication techniques and materials. We address this problem via the introduction of a novel microfabrication material, agarose gel, as the base material for the microfluidic device. Agarose gel is highly malleable, and permeable to gas and nutrients necessary for cell survival, and thus an ideal material for cell-based assays. We have shown previously that agarose gel based devices have been successful in studying bacterial and neutrophil cell migration2. In this report, three parallel microfluidic channels are patterned in an agarose gel membrane of about 1mm thickness. Constant flows with media/buffer are maintained in the two side channels using a peristaltic pump. Cells are maintained in the center channel for observation. Since the nutrients and chemicals in the side channels are constantly diffusing from the side to center channel, the chemical environment of the center channel is easily controlled via the flow along the side channels. Using this device, we demonstrate that the movement of neural stem cells can be monitored optically with ease under various chemical conditions, and the experimental results show that the over expression of epidermal growth factor receptors (EGFR) enhances the motility of neural stem cells. Motility of neural stem cells is an important biomarker for assessing cells aggressiveness, thus tumorigenic factor3. Deciphering the mechanism underlying NSC motility will yield insight into both disorders of neural development and into brain cancer stem cell invasion.

We demonstrate that the over expression of epidermal growth factor receptors (EGFR) enhances the motility of neural stem cells(NSCs) using a novel agarose gel based microfluidic device. This technology can be readily adaptable to other mammalian cell systems where cell sources are scarce, such as human neural stem cells, and the turn around time is critical.

While microfluidic technology is reaching a new level of maturity for macromolecular assays, cell-based assays are still at an infant stage1. This is ...

Biology

A Galvanotaxis Assay for Analysis of Neural Precursor Cell Migration Kinetics in an Externally Applied Direct Current Electric Field

The discovery of neural stem and progenitor cells (collectively termed neural precursor cells) (NPCs) in the adult mammalian brain has led to a body of research aimed at utilizing the multipotent and proliferative properties of these cells for the development of neuroregenerative strategies. A critical step for the success of such strategies is the mobilization of NPCs toward a lesion site following exogenous transplantation or to enhance the response of the endogenous precursors that are found in the periventricular region of the CNS. Accordingly, it is essential to understand the mechanisms that promote, guide, and enhance NPC migration. Our work focuses on the utilization of direct current electric fields (dcEFs) to promote and direct NPC migration - a phenomenon known as galvanotaxis. Endogenous physiological electric fields function as critical cues for cell migration during normal development and wound repair. Pharmacological disruption of the trans-neural tube potential in axolotl embryos causes severe developmental malformations1. In the context of wound healing, the rate of repair of wounded cornea is directly correlated with the magnitude of the epithelial wound potential that arises after injury, as shown by pharmacological enhancement or disruption of this dcEF2-3. We have demonstrated that adult subependymal NPCs undergo rapid and directed cathodal migration in vitro when exposed to an externally applied dcEF. In this protocol we describe our lab's techniques for creating a simple and effective galvanotaxis assay for high-resolution, long-term observation of directed cell body translocation (migration) on a single-cell level. This assay would be suitable for investigating the mechanisms that regulate dcEF transduction into cellular motility through the use of transgenic or knockout mice, short interfering RNA, or specific receptor agonists/antagonists.

In this protocol we demonstrate how to construct custom chambers that permit the application of a direct current electric field to enable time-lapse imaging of adult brain derived neural precursor cell translocation during galvanotaxis.

The discovery of neural stem and progenitor  cells (collectively termed neural precursor cells) (NPCs) in the adult  mammalian brain has led to a body of ...

Neuroscience

Preparation of Neuronal Co-cultures with Single Cell Precision

Microfluidic embodiments of the Campenot chamber have attracted great interest from the neuroscience community. These interconnected co-culture platforms can be used to investigate a variety of questions, spanning developmental and functional neurobiology to infection and disease propagation. However, conventional systems require significant cellular inputs (many thousands per compartment), inadequate for studying low abundance cells, such as primary dopaminergic substantia nigra, spiral ganglia, and Drosophilia melanogaster neurons, and impractical for high throughput experimentation. The dense cultures are also highly locally entangled, with few outgrowths (&#60;10%) interconnecting the two cultures. In this paper straightforward microfluidic and patterning protocols are described which address these challenges: (i) a microfluidic single neuron arraying method, and (ii) a water masking method for plasma patterning biomaterial coatings to register neurons and promote outgrowth between compartments. Minimalistic neuronal co-cultures were prepared with high-level (&#62;85%) intercompartment connectivity and can be used for high throughput neurobiology experiments with single cell precision.

Protocols for single neuron microfluidic arraying and water masking for the in-chip plasma patterning of biomaterial coatings are described. Highly interconnected co-cultures can be prepared using minimal cell inputs.

Microfluidic embodiments of the Campenot chamber have attracted great interest from the neuroscience community. These interconnected co-culture platforms ...

Microfluidic Device for the Separation of Non-Metastatic (MCF-7) and Non-Tumor (MCF-10A) Breast Cancer Cells Using AC Dielectrophoresis

Dielectrophoretic devices are capable of the detection and manipulation of cancer cells in a label-free, cost-effective, robust, and accurate manner using the principle of the polarization of the cancer cells in the sample volume by applying an external electric field. This article demonstrates how a microfluidic platform can be utilized for high-throughput continuous sorting of non-metastatic breast cancer cells (MCF-7) and non-tumor breast epithelial cells (MCF-10A) using hydrodynamic dielectrophoresis (HDEP) from the cell mixture. By generating an electric field between two electrodes placed side-by-side with a micron-sized gap between them in an HDEP microfluidic chip, non-tumor breast epithelial cells (MCF-10A) can be pushed away, exhibiting negative DEP inside the main channel, while the non-metastatic breast cancer cells follow their course unaffected when suspended in cell medium due to having conductivity higher than the membrane conductivity. To demonstrate this concept, simulations were performed for different values of medium conductivity, and the sorting of cells was studied. A parametric study was carried out, and a suitable cell mixture conductivity was found to be 0.4 S/m. By keeping the medium conductivity fixed, an adequate AC frequency of 0.8 MHz was established, giving maximum sorting efficiency, by varying the electric field frequency. Using the demonstrated method, after choosing the appropriate cell mixture suspension medium conductivity and frequency of the applied AC, maximum sorting efficiency can be achieved.

Microfluidic Device for the Separation of Non-Metastatic MCF-7 and Non-Tumor MCF-10A Breast Cancer Cells Using AC Dielectrophoresis

Breast cancer cells exhibit different dielectric properties compared to non-tumor breast epithelial cells. It has been hypothesized that, based on this difference in dielectric properties, the two populations can be separated for immunotherapy purposes. To support this, we model a microfluidic device to sort MCF-7 and MCF-10A cells.

Dielectrophoretic devices are capable of the detection and manipulation of cancer cells in a label-free, cost-effective, robust, and accurate manner using ...

Engineering

Generation of Dynamical Environmental Conditions using a High-Throughput Microfluidic Device

Mimicking in vivo environmental conditions is crucial for in vitro studies on complex life machinery. However, current techniques targeting live cells and organs are either highly expensive, like robotics, or lack nanoliter volume and millisecond time accuracy in liquid manipulation. We herein present the design and fabrication of a microfluidic system, which consists of 1,500 culture units, an array of enhanced peristaltic pumps and an on-site mixing modulus. To demonstrate the capacities of the microfluidic device, neural stem cell (NSC) spheres are maintained in the proposed system. We observed that when the NSC sphere is exposed to CXCL in day 1 and EGF in day 2, the round-shaped conformation is well maintained. Variation in the input order of 6 drugs causes morphological changes to the NSC sphere and the expression level representative marker for NSC stemness (i.e., Hes5 and Dcx). These results indicate that dynamic and complex environmental conditions have great effects on NSC differentiation and self-renewal, and the proposed microfluidic device is a suitable platform for high throughput studies on the complex life machinery.

We present a microfluidic system for high throughput studies on complex life machinery, which consists of 1500 culture units, an array of enhanced peristaltic pumps and an on-site mixing modulus. The microfluidic chip allows for the analysis of the highly complex and dynamic micro-environmental conditions in vivo.

Mimicking in vivo environmental conditions is crucial for in vitro studies on complex life machinery. However, current techniques targeting live cells and ...

Compartmentalization of Human Stem Cell-Derived Neurons within Pre-Assembled Plastic Microfluidic Chips

Use of microfluidic devices to compartmentalize cultured neurons has become a standard method in neuroscience. This protocol shows how to use a pre-assembled multi-compartment chip made in a cyclic olefin copolymer (COC) to compartmentalize neurons differentiated from human stem cells. The footprint of these COC chips are the same as a standard microscope slide and are equally compatible with high resolution microscopy. Neurons are differentiated from human neural stem cells (NSCs) into glutamatergic neurons within the chip and maintained for 5 weeks, allowing sufficient time for these neurons to develop synapses and dendritic spines. Further, we demonstrate multiple common experimental procedures using these multi-compartment chips, including viral labeling, establishing microenvironments, axotomy, and immunocytochemistry.

This protocol demonstrates the use of compartmentalized microfluidic chips, injection molded in a cyclic olefin copolymer to cultured neurons differentiated from human stem cells. These chips are preassembled and easier-to-use than traditional compartmentalized poly(dimethylsiloxane) devices. Multiple common experimental paradigms are described here, including viral labeling, fluidic isolation, axotomy, and immunostaining.

Use of microfluidic devices to compartmentalize cultured neurons has become a standard method in neuroscience. This protocol shows how to use a ...

Generation of Human Motor Units with Functional Neuromuscular Junctions in Microfluidic Devices

Neuromuscular junctions (NMJs) are specialized synapses between the axon of the lower motor neuron and the muscle facilitating the engagement of muscle contraction. In motor neuron disorders, such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA), NMJs degenerate, resulting in muscle atrophy and progressive paralysis. The underlying mechanism of NMJ degeneration is unknown, largely due to the lack of translatable research models. This study aimed to create a versatile and reproducible in vitro model of a human motor unit with functional NMJs. Therefore, human induced pluripotent stem cell (hiPSC)-derived motor neurons and human primary mesoangioblast (MAB)-derived myotubes were co-cultured in commercially available microfluidic devices. The use of fluidically isolated micro-compartments allows for the maintenance of cell-specific microenvironments while permitting cell-to-cell contact through microgrooves. By applying a chemotactic and volumetric gradient, the growth of motor neuron-neurites through the microgrooves promoting myotube interaction and the formation of NMJs were stimulated. These NMJs were identified immunocytochemically through co-localization of motor neuron presynaptic marker synaptophysin (SYP) and postsynaptic acetylcholine receptor (AChR) marker &#945;-bungarotoxin (Btx) on myotubes and characterized morphologically using scanning electron microscopy (SEM). The functionality of the NMJs was confirmed by measuring calcium responses in myotubes upon depolarization of the motor neurons. The motor unit generated using standard microfluidic devices and stem cell technology can aid future research focusing on NMJs in health and disease.

We describe a method to generate human motor units in commercially available microfluidic devices by co-culturing human induced pluripotent stem cell-derived motor neurons with human primary mesoangioblast-derived myotubes resulting in the formation of functionally active neuromuscular junctions.

Neuromuscular junctions (NMJs) are specialized synapses between the axon of the lower motor neuron and the muscle facilitating the engagement of muscle ...

Electrical Stimulation-Induced Differentiation of Neural Stem and Progenitor Cells

Source: Chang, H. et al., <a href="https://app.jove.com/v/61917">Electric-Field-Induced Neural Precursor Cell Differentiation in Microfluidic Devices.</a>&#160;J. Vis. Exp. (2021)
This video demonstrates the use of an extracellular matrix-coated microfluidic chip to differentiate neural stem and progenitor cells or NPCs through electrical stimulation. After seeding and adhering to the coated region, NPCs grow, and the application of a direct current&#160; triggers their differentiation into neurons, astrocytes, and oligodendrocytes.

1. Design and fabrication of the multichannel, optically transparent, electrotactic (MOE) chip

	Draw patterns for individual polymethyl methacrylate ...

JoVE Encyclopedia of Experiments

Neuronal Culture Techniques

Advanced Neuronal Models

Differentiation of Neural Stem Cells to Neurons Using a Compartmentalized Microfluidic Device

Source: Paranjape, S. R., et al. <a href="https://app.jove.com/v/59250">Compartmentalization of Human Stem Cell-Derived Neurons within Pre-Assembled Plastic Microfluidic Chips.</a> J. Vis. Exp. (2019)
The video demonstrates the differentiation of neural stem cells (NSCs) using a microfluidic device comprising a somatic and an axonal compartment separated by a microgroove barrier. NSCs are introduced into the somatic compartment and are allowed to adhere. The NSCs differentiate into neurons inside the somatic compartment and extend axons through the microgroove barrier to the axonal compartment.

NOTE:&#160;Figure 1A, B&#160;shows a schematic of the pre-assembled cyclic olefin copolymer (COC) chip, including the locations of the main channels or ...