Name: fabrication of a multiplexed artificial cellular microenvironment array
Uploaded: 2018-09-07T13:00:00
Description: Watch this Scientific Journal Video about Fabrication of a Multiplexed Artificial Cellular MicroEnvironment Array at JoVE.com

We thank Prof. N. Nakatsuji at iCeMS, Kyoto University, for providing human ES cells. We also thank Prof. A. Maruyama at Tokyo Institute of Technology for his support in the use of the atomic force microscope. Funding was generously provided by the Japan Society for the Promotion of Science (JSPS; 22350104, 23681028, 25886006, and 24656502); funding was also provided by the New Energy and Industrial Technology Development Organization (NEDO) and the Terumo Life Science Foundation. The WPI-iCeMS is supported by the World Premier International Research Centre Initiative (WPI), the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. A part of this work was supported by Kyoto University Nanotechnology Hub and the AIST Nano-Processing Facility in "Nanotechnology Platform Project" sponsored by MEXT, Japan.

1. Fabrication of MACME Array
Note: All materials and equipment are listed in the Materials Table.
<ol>
	<li>Preparation of masks for a nanofiber array and a mold for a microfluidic structure
	<ol>
		<li>Create three-dimensional (3D) images of masks used for the nanofiber arrays and molds for microfluidic structures using 3D-computer graphics software packages (Table 1). 
		Note: The 3D images are read and printed by a 3D printer. The p...

This protocol demonstrates the first screening method to establish a robust culture system for the maintenance of qualified hPSCs. First, we described how to prepare a platform featuring diverse artificial ECMs and cell seeding densities by using a microfluidic device integrated with a nanofiber array, the MACME array. Second, quantitative image-based single-cell phenotyping was performed50 to evaluate individual cellular outcomes and behaviors altered by distinct biochemical and biophysical featu...

Human pluripotent stem cells (hPSCs)1,2 self-renew unlimitedly and differentiate into various tissue lineages, which could revolutionize drug development, cell-based therapies, tissue engineering, and regenerative medicine3,4,5,6. General culture dishes and microtiter plates, however, are not designed to enable precise physical and chemical cell manipulation at the cellular level with the range of nano- to micro-meters, which is a critical factor for cellular expansion, self-renewal, and differentiation. To address this drawback, studies have investigated the roles of cellular microenvironments in regulating cell-fate decisions and cell functions4. In recent years, an increasing number of studies have been conducted to reconstruct cellular microenvironments in vitro7,8. Nano- and micro-fabrication processes have established these microenvironments through the manipulation of chemical9,10,11,12,13,14,15,16,17 and physical18,19,20 environmental cues. Until now, there were no reports to systematically investigate the underlying mechanisms of chemical and physical environmental cues on cell-fate decisions and functions within a single platform.
Here, we introduce a strategy based on simple design principles to establish a robust screening platform (Figure 1). First, we describe the development procedure of an integrated platform for creating versatile, artificial cellular microenvironments by using a nanofiber array and a microfluidic structure: The Multiplexed Artificial Cellular MicroEnvironment (MACME) array (Figure 1A and 2A). The nanofiber array has 12 different microenvironments in varying combinations of nanofiber materials and densities. Electrospinning was used to fabricate nanofibers. The nanofiber materials, such as polystyrene (PS)21, polymethylglutarimide (PMGI)22, and gelatin (GT)23, were designed to test their chemical properties, which might affect cell adhesion and maintenance of pluripotency (Figure 2B). Nanofiber densities were varied by changing electrospinning time and the generated nanofibers were defined according to their densities (DNF, with D = XLow/Low/Mid/High). The microfluidic structure is composed of polydimethylsiloxane (PDMS) harboring 48 cell-culture chambers, which can be positioned along the standard dimensions of the 96-well microplate. PDMS is a biocompatible and gas-exchangeable polymer generally used to fabricate microfluidic devices24. Each microfluidic channel was designed to be 700-&#181;m wide and 8.4-mm long and had two inlets at its edges (Table 1). The chambers had different heights (250, 500, and 1000 &#181;m) to manipulate the initial cell-seeding densities (0.3, 0.6, and 1.2 &#215; 105 cells/cm2), which might correlate with survival, proliferation, and differentiation of hPSCs25 (Figure 2C). The number of cells seeded into a chamber is proportional to the column density above the chamber floor, and thus initial cell seeding density was controlled by introducing the same cell suspension into culture chambers with different heights. All channels were designed to be &#8805; 250-&#181;m-high26 to minimize the effects of low-oxygen tension27 and shear stress28 on the cells. Channel heights of 250, 500, and 1000 &#181;m are abbreviated here as XCD with X = Low, Mid, and High, respectively. The environments with distinct nanofiber densities and initial cell-seeding densities were shortened as &#34;Material_NF density_Cell density&#34; (e.g., GT_HighNF_HighCD: an environment characterized by high-density GT nanofibers and high initial cell-seeding density).
Subsequently, we describe how to perform single-cell analyses to systematically investigate cell behavior in response to environmental factors (Figure 1B). As a proof-of-concept, we identified the optimal cellular environment for hPSC self-renewal, which is a key function for hPSC maintenance (Figure 1B)29. Image-based cytometry, followed by statistical analyses, allows for quantitative interpretation of individual cellular phenotypic responses to cellular environments. Among a variety of cellular functions, this paper provides a detailed procedure to identify the optimal conditions for maintaining hPSC self-renewal.

<table border="0" cellpadding="0" cellspacing="0" style="width:700px;" width="699">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Polystyrene (PS)</td>
			<td style="width:135px;">Sigma</td>
			<td style="width:119px;">#182435</td>
			<td style="width:231px;">Average Mw: 290,000, average Mn: 130,000</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Polymethylglutarimide (PMGI)</td>
			<td style="width:135px;">MicroChem</td>
			<td style="width:119px;">G113113</td>
			<td style="width:231px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Gelatin (GT)</td>
			<td style="width:135px;">Sigma</td>
			<td style="width:119px;">G2625</td>
			<td style="width:231px;">From porcine skin, type A</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Sylgard 184 silicone elastomer kit</td>
			<td style="width:135px;">Doe Corning Toray</td>
			<td style="width:119px;">#1064291</td>
			<td style="width:231px;">PDMS curing agent and silicone elastomer base are components of this kit.</td>
		</tr>
		<tr height="100">
			<td height="100" style="height:100px;width:216px;">OpenSCAD</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:231px;">This is a free 3D computer graphics software (http://www.openscad.org/) used for designing the mold of the microfluidic device.</td>
		</tr>
		<tr height="126">
			<td height="126" style="height:126px;width:216px;">AutoCAD 2014</td>
			<td style="width:135px;">Autodesk</td>
			<td style="width:119px;"></td>
			<td style="width:231px;">This is a 3D computer graphics software (https://www.autodesk.com/products/autocad/overview) used for design of the mask used on nanofiber-array preparation.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">3D printer, AGILISTA-3000</td>
			<td style="width:135px;">Keyence</td>
			<td style="width:119px;"></td>
			<td style="width:231px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">UV-curable resin, AR-M2</td>
			<td style="width:135px;">Keyence</td>
			<td style="width:119px;"></td>
			<td style="width:231px;">This is used for 3D printing by Agilista.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Acetic acid</td>
			<td style="width:135px;">Sigma</td>
			<td style="width:119px;">#338826</td>
			<td style="width:231px;">&#8805;99.99%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ethyl acetate</td>
			<td style="width:135px;">Sigma</td>
			<td style="width:119px;">#270989</td>
			<td style="width:231px;">Anhydrous, 99.8%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tetrahydrofuran (THF)</td>
			<td style="width:135px;">Sigma</td>
			<td style="width:119px;">#401757</td>
			<td style="width:231px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">MSP-30T</td>
			<td style="width:135px;">Vacuum Device</td>
			<td style="width:119px;"></td>
			<td style="width:231px;">Magnetron sputtering machine</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Nunc OmniTray</td>
			<td style="width:135px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">#242811</td>
			<td style="width:231px;">This is a polystyrene baseplate on which the nanofiber array is created. This plate size is typically 127.7 x 85.5 mm.&#160;</td>
		</tr>
		<tr height="126">
			<td height="126" style="height:126px;width:216px;">Gun-type corona discharge machine</td>
			<td style="width:135px;">Shinko Electric &#38; Instrumentation</td>
			<td style="width:119px;">CFG-500</td>
			<td style="width:231px;">This handy device is used to generate corona for activation of the bottom surface of the PDMS layer at step 1.5 &#34;Assembly of the MACME arrays&#34; in the protocol.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">5 mL syringe</td>
			<td style="width:135px;">Terumo</td>
			<td style="width:119px;">SS-05SZ</td>
			<td style="width:231px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Stainless-steel blunt needle (23-gauge)</td>
			<td style="width:135px;">Nipro</td>
			<td style="width:119px;">#2166</td>
			<td style="width:231px;">Outside diameter and length are 0.6 and 32 mm, respectively.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">High-voltage power supply</td>
			<td style="width:135px;">TechDempaz</td>
			<td style="width:119px;"></td>
			<td style="width:231px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide, hydrochloride</td>
			<td style="width:135px;">Dojindo</td>
			<td style="width:119px;">W001</td>
			<td style="width:231px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">N-Hydroxysuccinimide</td>
			<td style="width:135px;">Sigma</td>
			<td style="width:119px;">#56480</td>
			<td style="width:231px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Matrigel hESC-Qualified Matrix</td>
			<td style="width:135px;">Corning</td>
			<td style="width:119px;">#354277</td>
			<td style="width:231px;">This protein is refered as basement membrane gel matrix in the protocol.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">CellAdhere Vitronectin, Human, Solution</td>
			<td style="width:135px;">STEMCELL Technologies</td>
			<td style="width:119px;">#07004</td>
			<td style="width:231px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">TeSR-E8</td>
			<td style="width:135px;">STEMCELL Technologies</td>
			<td style="width:119px;">#05940</td>
			<td style="width:231px;">Feeder-free, xeno-free culture medium for maintenance of human ES and iPS cells</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Y-27632</td>
			<td style="width:135px;">Wako Pure Chemical Industries</td>
			<td style="width:119px;">#253-00513</td>
			<td style="width:231px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">TrypLE Express Enzyme (1X), phenol red</td>
			<td style="width:135px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">#12605028</td>
			<td style="width:231px;">This ia a recombinant trypsin-like protease for dissociation of adherant mammalian cells.</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:216px;">Click-iT EdU Imaging Kit with Alexa Fluor 647 Azides</td>
			<td style="width:135px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">C10086</td>
			<td style="width:231px;">The fluorescent labeling of proliferating cells in on-plate fluorescent staining was performed along the product manual of this kit.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Annexin V, Alexa Fluor 594 conjugate</td>
			<td style="width:135px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">A13203</td>
			<td style="width:231px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">4&#39;,6-diamidino-2-phenylindole (DAPI)</td>
			<td style="width:135px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">D1306</td>
			<td style="width:231px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Oct-3/4 Antibody (C-10)</td>
			<td style="width:135px;">Santa Cruz Biotechnology</td>
			<td style="width:119px;">sc-5279</td>
			<td style="width:231px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Donkey Anti-Mouse IgG H&#38;L (DyLight 488)</td>
			<td style="width:135px;">abcam</td>
			<td style="width:119px;">ab96875</td>
			<td style="width:231px;">This is a secondary antibody used in on-plate fluorescent cell staining.</td>
		</tr>
		<tr height="231">
			<td height="231" style="height:231px;width:216px;">ECLIPSE Ti-E</td>
			<td style="width:135px;">Nikon</td>
			<td style="width:119px;"></td>
			<td style="width:231px;">This is an inverted fluorescence microscope equipped with a CFI Plan Fluor 4&#215;/0.13 N.A. objective lens (Nikon), CCD camera (ORCA-R2, Hamamatsu), mercury lamp (Intensilight, Nikon), XYZ automated stage (Ti-S-ER motorized stage with encoders, Nikon), and filter cubes for four fluorescence channels (DAPI, GFP HYQ, TRITC, Cy5; Nikon)</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">NIS-Elements Advanced Research</td>
			<td style="width:135px;">Nikon</td>
			<td style="width:119px;"></td>
			<td style="width:231px;">This is a microscope imaging software used for automatic image acquisition.</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">CellProfiler, Version 2.1.0</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:231px;">This is a free open software for cell image analysis (http://cellprofiler.org/).</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">R</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:231px;">SOM analysis is performed by kohonen package of this software. This is freely available (https://www.r-project.org/).</td>
		</tr>
		<tr height="147">
			<td height="147" style="height:147px;width:216px;">Cluster 3.0</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:231px;">This is the open source clustering software (http://bonsai.hgc.jp/~mdehoon/software/cluster/software.htm). Unsupervised hierarchical clustering is performed with this software.</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:216px;">Java TreeView</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:231px;">This open source software (http://jtreeview.sourceforge.net/) is used to visualize clustering data as a heatmap and a dendrogram.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">H9 human embryonic stem cell</td>
			<td style="width:135px;">WiCell Stem Cell Bank</td>
			<td style="width:119px;">WA09</td>
			<td style="width:231px;"></td>
		</tr>
	</tbody>
</table>

fabrication of a multiplexed artificial cellular microenvironment array

Cellular microenvironments consist of a variety of cues, such as growth factors, extracellular matrices, and intercellular interactions. These cues are well orchestrated and are crucial in regulating cell functions in a living system. Although a number of researchers have attempted to investigate the correlation between environmental factors and desired cellular functions, much remains unknown. This is largely due to the lack of a proper methodology to mimic such environmental cues in vitro, and simultaneously test different environmental cues on cells. Here, we report an integrated platform of microfluidic channels and a nanofiber array, followed by high-content single-cell analysis, to examine stem cell phenotypes altered by distinct environmental factors. To demonstrate the application of this platform, this study focuses on the phenotypes of self-renewing human pluripotent stem cells (hPSCs). Here, we present the preparation procedures for a nanofiber array and the microfluidic structure in the fabrication of a Multiplexed Artificial Cellular MicroEnvironment (MACME) array. Moreover, overall steps of the single-cell profiling, cell staining with multiple fluorescent markers, multiple fluorescence imaging, and statistical analyses, are described.

MACME arrays: Design and fabrication: In combination with nanofiber technology, we used microfluidic cell culture and screening techniques employed previously to identify optimal conditions for hPSC self-renewal or differentiation35,36 (Figure 1). This is well suited for establishing robust high-throughput cell-based assays because the cell culture chambers and conditions are precisel...

Watch this Scientific Journal Video about Fabrication of a Multiplexed Artificial Cellular MicroEnvironment Array at JoVE.com

Fabrication of a Multiplexed Artificial Cellular MicroEnvironment Array

This article describes the detailed methodology to prepare a Multiplexed Artificial Cellular MicroEnvironment (MACME) array for high-throughput manipulation of physical and chemical cues mimicking in vivo cellular microenvironments and to identify the optimal cellular environment for human pluripotent stem cells (hPSCs) with single-cell profiling.

Cellular microenvironments consist of a variety of cues, such as growth factors, extracellular matrices, and intercellular interactions. These cues are ...

This method can help with a key question in the stem cell engineering field such as, how cellular microenvironment alter the cellular phenotypes and function. The main advantage of this technique is it provides the multiple artificially created environment for the cells in a single plate which you could not perform with a conventional method in micro-contact plate demonstrating this procedure will be Koki Yoshimoto and Risako Sakai technicians from our laboratory. After creating 3D images of masks for nano fiber arrays and molds from microfluidic structures according to the text protocol.Use a 3D printer to print the masks and mold. To prepare polymer solutions for electro spinning, dilute 13 percent PMGI liquid with tetrahydrofuran to nine percent. Dissolve 0.08 grams of PS in a one to one volume ratio of THF to dimethylformamide and use a liquid regent to bring the volume up to the final one milliliter of eight percent weight per volume PS solution.Dissolve 0.1 gram of GT in water, acidic acid and ethyl acetate and use the mixed solvent solution to bring the volume up to the final one milliliter of 10 percent weight by volume GT solution. Next, using a magnetron sputtering machine, deposit a five nanometer thick platinum layer on a polystyrene base plate which serves as a cathode in the electro spinning setup. Load each polymer solution into a five milliliter syringe equipped with a 23 gauge stainless steel blunt needle.Then anchor the syringes on a syringe pump 12 centimeters apart from the collector of the electro spinning device. Connect the syringe needle to a high voltage power supply and set it to 11 kilovolts. Then set the pumping rate to 20 milliliters per hour and keep the temperature and humidity at 30 degrees Celsius and less than 30 percent by volume, respectively.Now put the mask on the base plate. Then through the holes of the mask, fabricate nano fibers on the base plate with distinct densities by changing the electro spinning time. Remove the mask from the base plate and repeat the nano fiber fabrication.When the array is complete, place it in a desiccator at 25 degrees Celsius for 16 hours to evaporate the remaining solvent. To cross link the GT nano fibers, treat them with 0.2 molar EDC and 0.2 molar NHS in ethanol. And incubate the samples at 25 degrees Celsius for four hours.To rinse the GT nano fibers, use 99.5 percent ethanol twice and vacuum dry the plates at 25 degrees Celsius for 16 hours. To fabricate microfluidic structures, mix 2 grams of PDMS curing agent and 20 grams of PDMS base. Then pour the pre-PDMS mixture on to the fabricated mold.In a desiccator degas the pre PDMS mixture for 30 minutes. Then cure the pre PDMS mixture in an oven at 65 degrees Celsius for 16 hours. To assemble Macme arrays, peel off the cured PDMS structure from the mold and use 70 percent ethanol to clean it.Then discharge atmospheric corona on the bottom side of the PDMS structure. Quickly assemble the PDMS structure with the nano fiber array. Then oven bake the assembly at 65 degrees Celsius for two days.Using DPBS wash H9HESCs cultured on a 35 millimeter dish. Then add 0.5 milliliters of recombinant trypsin light protease to the dish and incubate it at 37 degrees Celsius for one minute. Carefully aspirate on the supernatant protease mixture.Immediately add HPSC medium and gently dispense the medium against the dish surface repeatedly to dissociate cells. Then transfer the detached cells to a 15 milliliter conical tube. Centrifuge the tube a 200 times gravity for three minutes.Aspirate the supernatant and suspend the cells in pre warmed HPSC medium. Then pipette 12 microliters of the cell suspension into each microfluidic chamber. After fluorescently labeling the cells according to the text protocol, peel off the PDMS microfluidic structure from the Macme array.Then remove the residual PBMS from the Macme array add 90 percent glycerol in PBS to the stained cells and apply a cover slip. Finally, set the plate upside down on the stage of an inverted fluorescence microscope. And use the microscope imaging software to acquire 12 bit color images.Shown here are immunofluorescence images of H9HPSCs cultured at high initial seeding density on gelatin nano fibers and stained with 3 cellular phenotypic markers. SOM analysis was used to convert high dimensional multi parametric data sets into low dimensional 2D maps for comparing homogeneity and heterogeneity of expression levels for the four phenotypic markers in each data set and unsupervised hierarchical clustering was performed for the SOM nodes. As indicated here, all groups exhibited higher expression of OCT4 than was observed on basement membrane gel matrix, or MG.Group one showed high EdU signals, indicating that most cells were actively proliferating.Thus, microenvironments in group one were suitable for HPSC maintenance because undifferentiated HPSCs proliferate rapidly when cell cycle gap phases were shortened. Group two included cells seeded at an insufficient initial density and cells grown on 2D GT scaffolds that did not support HPSC self renewal. For example, this sample's EdU signal was lost and annexin V levels were slightly increased indicating that the cells had lost their stemness and had gradually become apoptotic.PMGI MidNF HighCD from group three which represents the microenvironments comprising PMGI nano fiber matrices showed the larger variations in OCT4 and EdU signals compared with the other conditions. After it's development, this technique paved the way for the researcher in the field of STEM cell to explore the tissue engineering and advanced screening.

fabrication-multiplexed-artificial-cellular-microenvironment

Research

JoVE Journal

Bioengineering

Microfluidic Device for Recreating a Tumor Microenvironment in Vitro

We have developed a microfluidic device that mimics the delivery and systemic clearance of drugs to heterogeneous three-dimensional tumor tissues in vitro. Nutrients delivered by vasculature fail to reach all parts of tumors, giving rise to heterogeneous microenvironments consisting of viable, quiescent and necrotic cell types. Many cancer drugs fail to effectively penetrate and treat all types of cells because of this heterogeneity. Monolayers of cancer cells do not mimic this heterogeneity, making it difficult to test cancer drugs with a suitable in vitro model. Our microfluidic devices were fabricated out of PDMS using soft lithography. Multicellular tumor spheroids, formed by the hanging drop method, were inserted and constrained into rectangular chambers on the device and maintained with continuous medium perfusion on one side. The rectangular shape of chambers on the device created linear gradients within tissue. Fluorescent stains were used to quantify the variability in apoptosis within tissue. Tumors on the device were treated with the fluorescent chemotherapeutic drug doxorubicin, time-lapse microscopy was used to monitor its diffusion into tissue, and the effective diffusion coefficient was estimated. The hanging drop method allowed quick formation of uniform spheroids from several cancer cell lines. The device enabled growth of spheroids for up to 3 days. Cells in proximity of flowing medium were minimally apoptotic and those far from the channel were more apoptotic, thereby accurately mimicking regions in tumors adjacent to blood vessels. The estimated value of the doxorubicin diffusion coefficient agreed with a previously reported value in human breast cancer. Because the penetration and retention of drugs in solid tumors affects their efficacy, we believe that this device is an important tool in understanding the behavior of drugs, and developing new cancer therapeutics.

Microfluidic Device for Recreating a Tumor Microenvironment in Vitro

We present the procedure for fabrication and operation of a microfluidic device that recreates heterogeneous tumor microenvironments in vitro. The variability in apoptosis within tumor tissue was quantified using fluorescent stains and the effective diffusion coefficient of the chemotherapeutic drug doxorubicin into tumor tissue was evaluated.

We have developed a microfluidic device that mimics the delivery and systemic clearance of drugs to heterogeneous three-dimensional tumor tissues in ...

Low-Cost Cryo-Light Microscopy Stage Fabrication for Correlated Light/Electron Microscopy

The coupling of cryo-light microscopy (cryo-LM) and cryo-electron microscopy (cryo-EM) poses a number of advantages for understanding cellular 
dynamics and ultrastructure. First, cells can be imaged in a near native environment for both techniques. Second, due to the vitrification process, samples are
 preserved by rapid physical immobilization rather than slow chemical fixation. Third, imaging the same sample with both cryo-LM and cryo-EM provides correlation of
 data from a single cell, rather than a comparison of "representative samples". While these benefits are well known from prior studies, the widespread use of correlative 
 cryo-LM and cryo-EM remains limited due to the expense and complexity of buying or building a suitable cryogenic light microscopy stage. Here we demonstrate the 
 assembly, and use of an inexpensive cryogenic stage that can be fabricated in any lab for less than $40 with parts found at local hardware and grocery stores. This 
 cryo-LM stage is designed for use with reflected light microscopes that are fitted with long working distance air objectives. For correlative cryo-LM and cryo-EM 
 studies, we adapt the use of carbon coated standard 3-mm cryo-EM grids as specimen supports. After adsorbing the sample to the grid, previously established protocols 
 for vitrifying the sample and transferring/handling the grid are followed to permit multi-technique imaging. As a result, this setup allows any laboratory with a 
 reflected light microscope to have access to direct correlative imaging of frozen hydrated samples.

We demonstrate the fabrication of a low-cost cryogenic stage designed to fit most reflected light microscopes. This lab-built cryogenic stage enables efficient and reliable correlative imaging between cryo-light and cryo-electron microscopy.

The coupling of cryo-light microscopy (cryo-LM) and cryo-electron microscopy (cryo-EM) poses a number of advantages for understanding cellular 
dynamics ...

In vitro Assembly of Semi-artificial Molecular Machine and its Use for Detection of DNA Damage

Naturally occurring bio-molecular machines work in every living cell and display a variety of designs 1-6. Yet the development of artificial molecular machines centers on devices capable of directional motion, i.e. molecular motors, and on their scaled-down mechanical parts (wheels, axels, pendants etc) 7-9. This imitates the macro-machines, even though the physical properties essential for these devices, such as inertia and momentum conservation, are not usable in the nanoworld environments 10. Alternative designs, which do not follow the mechanical macromachines schemes and use mechanisms developed in the evolution of biological molecules, can take advantage of the specific conditions of the nanoworld. Besides, adapting actual biological molecules for the purposes of nano-design reduces potential dangers the nanotechnology products may pose. Here we demonstrate the assembly and application of one such bio-enabled construct, a semi-artificial molecular device which combines a naturally-occurring molecular machine with artificial components. From the enzymology point of view, our construct is a designer fluorescent enzyme-substrate complex put together to perform a specific useful function. This assembly is by definition a molecular machine, as it contains one 12. Yet, its integration with the engineered part - fluorescent dual hairpin - re-directs it to a new task of labeling DNA damage12.
Our construct assembles out of a 32-mer DNA and an enzyme vaccinia topoisomerase I (VACC TOPO). The machine then uses its own material to fabricate two fluorescently labeled detector units (Figure 1). One of the units (green fluorescence) carries VACC TOPO covalently attached to its 3'end and another unit (red fluorescence) is a free hairpin with a terminal 3'OH. The units are short-lived and quickly reassemble back into the original construct, which subsequently recleaves. In the absence of DNA breaks these two units continuously separate and religate in a cyclic manner. In tissue sections with DNA damage, the topoisomerase-carrying detector unit selectively attaches to blunt-ended DNA breaks with 5'OH (DNase II-type breaks)11,12, fluorescently labeling them. The second, enzyme-free hairpin formed after oligonucleotide cleavage, will ligate to a 5'PO4 blunt-ended break (DNase I-type breaks)11,12, if T4 DNA ligase is present in the solution 13,14 . When T4 DNA ligase is added to a tissue section or a solution containing DNA with 5'PO4 blunt-ended breaks, the ligase reacts with 5'PO4 DNA ends, forming semi-stable enzyme-DNA complexes. The blunt ended hairpins will interact with these complexes releasing ligase and covalently linking hairpins to DNA, thus labeling 5'PO4 blunt-ended DNA breaks.
This development exemplifies a new practical approach to the design of molecular machines and provides a useful sensor for detection of apoptosis and DNA damage in fixed cells and tissues.

In vitro Assembly of Semi-artificial Molecular Machine and its Use for Detection of DNA Damage

We demonstrate the assembly and application of a molecular-scale device powered by a topoisomerase protein. The construct is a bio-molecular sensor which labels two major types of DNA breaks in tissue sections by attaching two different fluorophores to their ends.

Naturally occurring bio-molecular machines work in every living cell and display a variety of designs 1-6. Yet the development of artificial molecular ...

Hollow Microneedle-based Sensor for Multiplexed Transdermal Electrochemical Sensing

The development of a minimally invasive multiplexed monitoring system for rapid analysis of biologically-relevant molecules could offer individuals suffering from chronic medical conditions facile assessment of their immediate physiological state. Furthermore, it could serve as a research tool for analysis of complex, multifactorial medical conditions. In order for such a multianalyte sensor to be realized, it must be minimally invasive, sampling of interstitial fluid must occur without pain or harm to the user, and analysis must be rapid as well as selective.
Initially developed for pain-free drug delivery, microneedles have been used to deliver vaccines and pharmacologic agents (e.g., insulin) through the skin.1-2 Since these devices access the interstitial space, microneedles that are integrated with microelectrodes can be used as transdermal electrochemical sensors. Selective detection of glucose, glutamate, lactate, hydrogen peroxide, and ascorbic acid has been demonstrated using integrated microneedle-electrode devices with carbon fibers, modified carbon pastes, and platinum-coated polymer microneedles serving as transducing elements.3-7,8
This microneedle sensor technology has enabled a novel and sophisticated analytical approach for in situ and simultaneous detection of multiple analytes. Multiplexing offers the possibility of monitoring complex microenvironments, which are otherwise difficult to characterize in a rapid and minimally invasive manner. For example, this technology could be utilized for simultaneous monitoring of extracellular levels of, glucose, lactate and pH,9 which are important metabolic indicators of disease states7,10-14 (e.g., cancer proliferation) and exercise-induced acidosis.15

This article details the construction of a multiplexed microneedle-based sensor. The device is being developed for in situ sampling and electrochemical analysis of multiple analytes in a rapid and selective manner. We envision clinical medicine and biomedical research uses for these microneedle-based sensors.

The development of a minimally invasive multiplexed monitoring system for rapid analysis of biologically-relevant molecules could offer individuals ...

Synthesis of an Intein-mediated Artificial Protein Hydrogel

We present the synthesis of a highly stable protein hydrogel mediated by a split-intein-catalyzed protein trans-splicing reaction. The building blocks of this hydrogel are two protein block-copolymers each containing a subunit of a trimeric protein that serves as a crosslinker and one half of a split intein. A highly hydrophilic random coil is inserted into one of the block-copolymers for water retention. Mixing of the two protein block copolymers triggers an intein trans-splicing reaction, yielding a polypeptide unit with crosslinkers at either end that rapidly self-assembles into a hydrogel. This hydrogel is very stable under both acidic and basic conditions, at temperatures up to 50 &#176;C, and in organic solvents. The hydrogel rapidly reforms after shear-induced rupture. Incorporation of a &#34;docking station peptide&#34; into the hydrogel building block enables convenient incorporation of &#34;docking protein&#34;-tagged target proteins. The hydrogel is compatible with tissue culture growth media, supports the diffusion of 20 kDa molecules, and enables the immobilization of bioactive globular proteins. The application of the intein-mediated protein hydrogel as an organic-solvent-compatible biocatalyst was demonstrated by encapsulating the horseradish peroxidase enzyme and corroborating its activity.

We present the synthesis of a split-intein-mediated protein hydrogel. The building blocks of this hydrogel are two protein copolymers each containing a subunit of a trimeric protein that serves as a crosslinker and one half of a split intein. Mixing of the two protein copolymers triggers an intein trans-splicing reaction, yielding a polypeptide unit that self-assembles into a hydrogel. This hydrogel is highly pH- and temperature-stable, compatible with organic solvents, and easily incorporates functional globular proteins.

We present the synthesis of a highly stable protein hydrogel mediated by a split-intein-catalyzed protein trans-splicing reaction. The building blocks of ...

Tissue Engineering of Tumor Stromal Microenvironment with Application to Cancer Cell Invasion

3D organotypic cultures of epithelial cells on a matrix embedded with mesenchymal cells are widely used to study epithelial cell differentiation and invasion. Rat tail type I collagen and/or matrix derived from Engelbreth-Holm-Swarm mouse sarcoma cells have been traditionally employed as the substrates to model the matrix or stromal microenvironment into which mesenchymal cells (usually fibroblasts) are populated. Although experiments using such matrices are very informative, it can be argued that due to an overriding presence of a single protein (such as in type I Collagen) or a high content of basement membrane components and growth factors (such as in matrix derived from mouse sarcoma cells), these substrates do not best reflect the contribution to matrix composition made by the stromal cells themselves. To study native matrices produced by primary dermal fibroblasts isolated from patients with a tumor prone, genetic blistering disorder (recessive dystrophic epidermolysis bullosa), we have adapted an existing native matrix protocol to study tumor cell invasion. Fibroblasts are induced to produce their own matrix over a prolonged period in culture. This native matrix is then detached from the culture dish and epithelial cells are seeded onto it before the entire coculture is raised to the air-liquid interface. Cellular differentiation and/or invasion can then be assessed over time. This technique provides the ability to assess epithelial-mesenchymal cell interactions in a 3D setting without the need for a synthetic or foreign matrix with the only disadvantage being the prolonged period of time required to produce the native matrix. Here we describe the application of this technique to assess the ability of a single molecule expressed by fibroblasts, type VII collagen, to inhibit tumor cell invasion.

Tissue engineered fibroblast-derived native matrix is an emerging tool to generate a stromal substrate which supports epithelial cell proliferation and differentiation. Here a protocol applying this methodology to assess the impact of different stromal cell types on tumor cell biology is presented.

3D organotypic cultures of epithelial cells on a matrix embedded with mesenchymal cells are widely used to study epithelial cell differentiation and ...

Polymeric Microneedle Array Fabrication by Photolithography

This manuscript describes the fabrication of polymeric microneedle (MN) arrays by photolithography. It involves a simple mold-free process by using a photomask consisting of embedded micro-lenses. Embedded micro-lenses were found to influence MN geometry (sharpness). Robust MN arrays with tip diameters ranging between 41.5 &#181;m &#177; 8.4 &#181;m and 71.6 &#181;m &#177; 13.7 &#181;m, with two different lengths (1,336 &#181;m &#177; 193 &#181;m and 957 &#181;m &#177; 171 &#181;m) were fabricated. These MN arrays may provide potential applications in delivery of low molecular and macromolecular therapeutic agents through skin.

Here, we present a protocol describing a mold-free fabrication process of the polymeric microneedles by photolithography.

This manuscript describes the fabrication of polymeric microneedle (MN) arrays by photolithography. It involves a simple mold-free process by using a ...

Fabrication of a Bioactive, PCL-based "Self-fitting" Shape Memory Polymer Scaffold

Tissue engineering has been explored as an alternative strategy for the treatment of critical-sized cranio-maxillofacial (CMF) bone defects. Essential to the success of this approach is a scaffold that is able to conformally fit within an irregular defect while also having the requisite biodegradability, pore interconnectivity and bioactivity. By nature of their shape recovery and fixity properties, shape memory polymer (SMP) scaffolds could achieve defect &#8220;self-fitting.&#8221; In this way, following exposure to warm saline (~60 &#186;C), the SMP scaffold would become malleable, permitting it to be hand-pressed into an irregular defect. Subsequent cooling (~37 &#186;C) would return the scaffold to its relatively rigid state within the defect. To meet these requirements, this protocol describes the preparation of SMP scaffolds prepared via the photochemical cure of biodegradable polycaprolactone diacrylate (PCL-DA) using a solvent-casting particulate-leaching (SCPL) method. A fused salt template is utilized to achieve pore interconnectivity. To realize bioactivity, a polydopamine coating is applied to the surface of the scaffold pore walls. Characterization of self-fitting and shape memory behaviors, pore interconnectivity and in vitro bioactivity are also described.

Fabrication of a Bioactive, PCL-based &quot;Self-fitting&quot; Shape Memory Polymer Scaffold

Scaffolds capable of fitting within cranio-maxillofacial (CMF) bone defects while exhibiting osteoconductivity and bioactivity are of interest. This protocol describes the preparation of a shape memory scaffold based on polycaprolactone diacrylate (PCL-DA) using a solvent-casting particulate-leaching (SCPL) method employing a fused salt template and application of a bioactive polydopamine coating.

Tissue engineering has been explored as an alternative strategy for the treatment of critical-sized cranio-maxillofacial (CMF) bone defects. Essential to ...

Microfluidic Platform with Multiplexed Electronic Detection for Spatial Tracking of Particles

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

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

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

Fabrication and Characterization of Optical Tissue Phantoms Containing Macrostructure

The rapid development of new optical imaging techniques is dependent on the availability of low-cost, customizable, and easily reproducible standards. By replicating the imaging environment, costly animal experiments to validate a technique may be circumvented. Predicting and optimizing the performance of in vivo and ex vivo imaging techniques requires testing on samples that are optically similar to tissues of interest. Tissue-mimicking optical phantoms provide a standard for evaluation, characterization, or calibration of an optical system. Homogenous polymer optical tissue phantoms are widely used to mimic the optical properties of a specific tissue type within a narrow spectral range. Layered tissues, such as the epidermis and dermis, can be mimicked by simply stacking these homogenous slab phantoms. However, many in vivo imaging techniques are applied to more spatially complex tissue where three dimensional structures, such as blood vessels, airways, or tissue defects, can affect the performance of the imaging system. 
This protocol describes the fabrication of a tissue-mimicking phantom that incorporates three-dimensional structural complexity using material with optical properties of tissue. Look-up tables provide India ink and titanium dioxide recipes for optical absorption and scattering targets. Methods to characterize and tune the material optical properties are described. The phantom fabrication detailed in this article has an internal branching mock airway void; however, the technique can be broadly applied to other tissue or organ structures.

Optical tissue phantoms are essential tools for calibration and characterization of optical imaging systems and validation of theoretical models. This article details a method for phantom fabrication that includes replication of tissue optical properties and three-dimensional tissue structure.

The rapid development of new optical imaging techniques is dependent on the availability of low-cost, customizable, and easily reproducible standards. By ...