Name: microscale vortex-assisted electroporator for sequential molecular delivery
Uploaded: 2014-08-07T20:15:00
Description: Watch this Scientific Journal Video about Microscale Vortex-assisted Electroporator for Sequential Molecular Delivery at JoVE.com

This work is supported by the Rowland Junior Fellow program. The authors would like to express gratitude to the scientists and staff at the Rowland Institute at Harvard: Chris Stokes for his help in the development of the custom-built, computer-assisted pressure control setup, Diane Schaak, Ph.D. for her input for biological sample handling, Winfield Hill for developing the electrical setup, Alavaro Sanchez, Ph.D. for granting access to the flow cytometer, Scott Bevis, Kenny Spencer and Don Rogers for machining mechanical plumbing components required for the pressure setup. Microfluidic masters were fabricated at the Center for Nanoscale Systems (CNS) at Harvard University.

1. Cell Preparation
<ol>
	<li>Plate 1&#215;105 cells/ml of metastatic breast cancer cell line MDA-MB-231 in a volume of 10 ml per tissue culture T75 flask in Leibovitz&#8217;s L-15 Medium supplemented with 10% (v/v) fetal bovine serum and 1% penicillin-streptomycin.</li>
	<li>Incubate MDA-MB-231 cells in a humidified incubator at 37 &#176;C with 0% CO2 environment.</li>
	<li>Harvest cells for experiments 2 days after seeding by treating cells with 0.25% trypsin-EDTA for 2 min and inactivate trypsi...

<ol>
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With the new parallelized electroporation platform, 10-fold enhancement in throughput and efficiency of multi-molecule delivery was achieved in addition to all the merits that the previously developed single-chamber system provides.18 Previously available merits include (i) pre-purification of target cells with uniform size distribution for viability enhancement, (ii) precise and individual molecular dosage control, and (iii) low operational electrical current. Fluorescently labeled dextrans were chosen as mol...

In recent years, the use of electric pulses to facilitate cytosolic delivery of extracellular molecules has become an attractive means of manipulating mammalian cells.1 This process, also known as electroporation, reversibly permeabilizes the cellular membrane, allowing for inherently membrane impermeable molecules to gain access to the cells&#8217; intracellular milieu. Because virtually any molecule can be introduced into the cytosol via temporary created pores in the membrane of any type of cells using electroporation, the technique has been reported as being more reproducible, universally applicable, and more efficient than other methods including virus-mediated, chemical and optical approaches.2-3 This technique has been utilized to introduce fluorescent molecules,4 drugs5 and nucleic acids6-7 while keeping cells viable and intact. Given these benefits, electroporation has been adopted as a common laboratory technique for DNA transfection, in vivo gene therapy8 and cell vaccination studies. It is, however, still difficult for conventional electroporation systems to simultaneously achieve practical efficiency and viability for samples with large heterogeneity in size because the electric field strength required for successful electroporation closely correlates with the cell&#8217;s diameter. Moreover, those systems do not allow precise control of the multiple molecular amounts being delivered due to reliance on bulk stochastic molecular delivery process.9 In order to address these issues, many groups have developed microfluidic electroporation platforms, offering the advantage of lower poration voltages, better transfection efficiency, a large reduction in cell mortality, and ability to deliver multiple molecules.10-13 These advantages were made possible owing to the small footprints of microscale electroporation systems whose electrode pitch lengths are sub-millimeters, dramatically decreasing voltages required for successful delivery. Moreover, these microscale electroporation systems can achieve uniform electric field distribution and rapidly dissipate generated heat, yielding reduced cell mortality while enhancing delivery efficiency. The utilization of transparent materials for these microchips further allows in situ observation of the electroporation process for prompt parameter modifications.2,12 However, precise dosage control and molecular- and cellular-dependent parameter control, required for emerging research and therapeutic applications,6,14-16 still remain unresolved.
This work presents a microfluidic vortex-assisted electroporation system, capable of delivering multiple molecules sequentially into a pre-selected identical population of target cells. Cells with uniform size distribution are isolated prior to electroporation using previously reported size-selective trapping mechanism.17-18 By having a uniform size distribution, less variation in electroporation efficiency and enhanced viability per given electric field strength were achieved.19 Furthermore, continuously agitating trapped cells using microscale vortices allowed for uniform delivery of molecules across the entire cytosol, in agreement with the results previously reported using another vortex-assisted electroporation platform.20 To demonstrate that this system would be applicable to a broad range of molecules commonly utilized in biological applications, macromolecules with a wide range of molecular weights were delivered to metastatic breast cancer cells. In addition, with the aid of real-time process monitoring, this work provides more evidence to put an end to the long standing debate regarding the mechanism of molecular delivery during electrporation, being predominantly electrophoresis-mediated versus diffusion-mediated.14 Unlike other electroporation systems, this platform uniquely provides the combined advantages of precise multi-molecule delivery, high molecular delivery efficiency, minimal cell mortality, a wide span of size and charges of delivered molecules, as well as real-time visualization of the electroporation process. Given these capabilities, the developed electroporation system has practical potential as a versatile tool for cellular reprogramming studies,6,14,21-22 drug delivery applications10,19 and applications requiring for in-depth understanding of electroporation molecular delivery mechanisms.

<table border="0" cellpadding="0" cellspacing="0" width="1056">
	<tbody>
		<tr height="20">
			<td height="20" style="height:21px;width:475px;">MDA-MB-231 cancer cell line</td>
			<td style="width:297px;">American Type Culture Collection (ATCC)</td>
			<td style="width:119px;">HTB-26</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">Leibovitz&#8217;s L-15 Medium</td>
			<td style="width:297px;">Cellgro, Mediatech, Inc.</td>
			<td style="width:119px;">10-045-CV</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">fetal bovine serum (FBS)</td>
			<td style="width:297px;">Gibco, Life Technologies</td>
			<td style="width:119px;">16000-044</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">penicillin-streptomycin</td>
			<td style="width:297px;">Sigma-Aldrich</td>
			<td style="width:119px;">P4333</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:475px;">Dulbecco&#39;s phosphate buffered saline (DPBS)</td>
			<td style="width:297px;">Cellgro, Mediatech, Inc.</td>
			<td style="width:119px;">21-030</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">Trypsin</td>
			<td style="width:297px;">Gibco, Life Technologies</td>
			<td style="width:119px;">25200-056</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">Flow Cytometer easyCyte HT</td>
			<td style="width:297px;">Millipore</td>
			<td style="width:119px;">0500-4008</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">Oxygen Plasma Cleaner</td>
			<td style="width:297px;">Technics Micro-RIE</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">Dektak 6M surface profiler</td>
			<td style="width:297px;">Veeco</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">KMPR 1050</td>
			<td style="width:297px;">Microchem</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">SYLGARD 184 SILICONE ELASTOMER KIT</td>
			<td style="width:297px;">Dow Corning</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">Compressed Nitrogen gas</td>
			<td style="width:297px;">Airgas</td>
			<td style="width:119px;">NI 300</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:475px;">High Pressure Regulator</td>
			<td style="width:297px;">McMaster-Carr</td>
			<td>6162K22</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">Downstream regulator</td>
			<td style="width:297px;">McMaster-Carr</td>
			<td style="width:119px;">4000K563</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">high-speed 3/2way-8 valve manifold</td>
			<td style="width:297px;">Festo</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">Inline Check Valve</td>
			<td style="width:297px;">Idex Health and Science</td>
			<td style="width:119px;">CV3320</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:475px;">5/32&#34; OD x 3/32&#34;ID Polyurethan tubes</td>
			<td style="width:297px;">Pneumadyne</td>
			<td>PU-156F-0</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">1/4&#34; OD X 0.17&#34; ID Polyurethan tubes</td>
			<td style="width:297px;">Pneumadyne</td>
			<td style="width:119px;">PU-250PB-4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">1/16&#34; PEEK tubings</td>
			<td style="width:297px;">Festo</td>
			<td style="width:119px;">P1533</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">1/32&#34; PEEK tubings</td>
			<td style="width:297px;">Idex Health and Science</td>
			<td style="width:119px;">P1569</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">PEEK tubing unions</td>
			<td style="width:297px;">Idex Health and Science</td>
			<td style="width:119px;">P881</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">Pulse Generator</td>
			<td style="width:297px;">HP</td>
			<td style="width:119px;">8110A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">Aluiminum Wire</td>
			<td style="width:297px;">Bob Martin Company</td>
			<td style="width:119px;">6061 ALUM</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">oscilloscope</td>
			<td style="width:297px;">Agilent</td>
			<td style="width:119px;">DSO3062A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">50 mL centrifuge tubes</td>
			<td style="width:297px;">VWR</td>
			<td style="width:119px;">21008-178</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">15 mL centrifuge tube</td>
			<td style="width:297px;">VWR</td>
			<td style="width:119px;">21008-216</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">T75 culture flask</td>
			<td style="width:297px;">VWR</td>
			<td style="width:119px;">82050-862</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">Dextran, Tetramethylrhodamine, 3000 MW, Anionic</td>
			<td style="width:297px;">Gibco, Life Technologies</td>
			<td style="width:119px;">D3307</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">Dextran, Tetramethylrhodamine, 70,000 MW, Neutral&#160;</td>
			<td style="width:297px;">Gibco, Life Technologies</td>
			<td style="width:119px;">D1819</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:475px;">Dextran, Texas Red, 3000 MW, Neutral</td>
			<td style="width:297px;">Gibco, Life Technologies</td>
			<td style="width:119px;">D3329</td>
			<td></td>
		</tr>
	</tbody>
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microscale vortex-assisted electroporator for sequential molecular delivery

Electroporation has received increasing attention in the past years, because it is a very powerful technique for physically introducing non-permeant exogenous molecular probes into cells. This work reports a microfluidic electroporation platform capable of performing multiple molecule delivery to mammalian cells with precise and molecular-dependent parameter control. The system&#8217;s ability to isolate cells with uniform size distribution allows for less variation in electroporation efficiency per given electric field strength; hence enhanced sample viability. Moreover, its process visualization feature allows for observation of the fluorescent molecular uptake process in real-time, which permits prompt molecular delivery parameter adjustments in situ for efficiency enhancement. To show the vast capabilities of the reported platform, macromolecules with different sizes and electrical charges (e.g., Dextran with MW of 3,000 and 70,000 Da) were delivered to metastatic breast cancer cells with high delivery efficiencies (&#62;70%) for all tested molecules. The developed platform has proven its potential for use in the expansion of research fields where on-chip electroporation techniques can be beneficial.

The developed parallel microfluidic electroporator delivered macromolecules with varied sizes and electrical charges into living metastatic breast cancer cells. Successful molecular delivery was qualitatively determined by monitoring changes in fluorescent intensity of electroporated orbiting cells in situ and confirmed by quantitative measurements via flow cytometry analysis. Figure 4A&#160;shows that 90% of treated cells uptake the 70,000 Da neutral dextran. For the statistical analysis, an in...

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Microscale Vortex-assisted Electroporator for Sequential Molecular Delivery

A microfluidic vortex assisted electroporation platform was developed for sequential delivery of multiple molecules into identical cell populations with precise and independent dosage control. The system&#8217;s size based target cell purification step preceding electroporation aided to enhance molecular delivery efficiency and processed cell viability.

Electroporation has received increasing attention in the past years, because it is a very powerful technique for physically introducing non-permeant ...

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