Name: synthesis of biocompatible liquid crystal elastomer foams as cell scaffolds for 3d spatial cell cultures
Uploaded: 2017-04-11T15:00:00
Description: Watch this Scientific Journal Video about Synthesis of Biocompatible Liquid Crystal Elastomer Foams as Cell Scaffolds for 3D Spatial Cell Cultures at JoVE.com

The authors would like to thank Kent State University (collaborative research grant and support for the Regenerative Medicine Initiative at Kent State &#8722; ReMedIKS) for the financial support of this project.

NOTE: The following steps for the 3D LCE foam-like preparation using the 3-arm star block copolymer are shown in Figure 1. For nuclear magnetic resonance (NMR) characterization, the spectra are recorded in deuterated chloroform (CDCl3) at room temperature on a Bruker DMX 400-MHz instrument and internally referenced residual peaks at 7.26. Fourier transform infrared (FT-IR) spectra are recorded using a Bruker Vector 33 FT-IR spectrometer using attenuated total reflectance mode. ...

<ol>
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Liquid crystalline elastomers have recently been studied as biocompatible cell scaffolds due to their stimuli responsiveness. They have been proven to be ideal platforms as cell scaffolds. However, an important factor to keep in mind when preparing and designing a new LCE scaffold is porosity. The incorporation of leachable solids23 or gases does not always result in homogeneous porosity or fully interconnected pores. The use of a metal template that can be etched out not only offers the opportuni...

There are several examples of biological and biocompatible synthetic materials designed for application in cell studies and for tissue regeneration aiming at cell attachment and proliferation1,2,3,4,5. There have been a few examples of biocompatible materials, known as liquid crystal elastomers (LCEs), that could respond to external stimuli with anisotropic molecular ordering6,7. LCEs are stimuli-responsive materials that combine the mechanical and elastic properties of elastomers with the optical functionality and molecular ordering of liquid crystals8,9. LCEs can experience changes in shape, mechanical deformation, elastic behavior, and optical properties in response to external stimuli (i.e., heat, stress, light, etc.)10,11,12,13,14,15,16. Earlier studies have shown that liquid crystals (LCs) can sense the growth and orientation of cells4,17. It is possible then to assume that LCEs may be suitable for biologically and medically relevant applications, including cell scaffolding and alignment. We have previously reported the preparation of smectic biocompatible, biodegradable, cast-molded, and thin LCEs films featuring a &#34;Swiss-cheese type&#34; porous morphology6,18. We also prepared nematic biocompatible LCEs with globular morphology as scaffolds for cell growth19,20. Our work was aimed at tuning the mechanical properties of the materials to match those of the tissue of interest21. Also, these studies focus on understanding elastomer-cell interactions, as well as cellular response when the elastomers are subject to external stimuli.
The main challenges were in part to tailor the porosity of the LCEs to allow for cell attachment and permeation through the elastomer matrix and for better mass transport. The porosity of these thin films6 allowed for cell permeation through the bulk of the matrix, but not all pores were fully interconnected or had a more regular (homogeneous) pore size. We then reported on biocompatible nematic LCE elastomers with globular morphologies. These nematic elastomers allowed for the attachment and proliferation of cells, but the pore size ranged only from 10-30 &#181;m, which prevented or limited the use of these elastomers with a wider variety of cell lines19,20.
Previous work by Kung et al. relating to the formation of graphene foams using a &#34;sacrificial&#34; metal template showed that the obtained graphene foam had a very regular porous morphology dictated by the chosen metal template22. This methodology offers full control of porosity and pore size. At the same time, the malleability and flexibility of the metal template allow for the formation of different template shapes prior to foam preparation. Other techniques, such as material leaching23, gas templating24, or electro-spun fibers25,26 also offer the potential for the preparation of porous materials, but they are more time consuming and, in some cases, the pore size is limited to only a few micrometers. Foam-like 3D LCEs prepared using metal templates allow for a higher cell load; an improved proliferation rate; co-culturing; and, last but not least, better mass transport management (i.e., nutrients, gases, and waste) to ensure full tissue development27. Foam-like 3D LCEs also appear to improve cell alignment; this is most likely in relation to the LC pendants sensing cell growth and cell orientation. The presence of LC moieties within the LCE appears to enhance cell alignment with respect to cell location within the LCE scaffold. Cells align within the struts of the LCE, while no clear orientation is observed where the struts join together (junctions)27.
Overall, our LCE cell scaffold platform as a cell support medium offers opportunities to tune the elastomer morphology and elastic properties and to specifically direct the alignment of (individual) cell types to create an ordered, spatial arrangements of cells similar to living systems. Apart from providing a scaffold capable of sustaining and directing long-term cellular growth and proliferation, LCEs also allow for dynamic experiments, where cell orientation and interactions may be modified on the fly.

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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane</td>
			<td style="width:148px;">Alfa Aesar</td>
			<td style="width:132px;">L16606</td>
			<td style="width:153px;">Silanizing agent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2-bis(4-hydroxy-cyclohexyl)propane</td>
			<td>TCI</td>
			<td><a href="http://www.tcichemicals.com/eshop/en/us/commodity/B0928/">B0928</a></td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2-chlorohexanone&#160;</td>
			<td>Alfa Aesar</td>
			<td>A18613</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2-heptanone&#160;</td>
			<td>Sigma Aldrich</td>
			<td>W254401</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2-propanol&#160;</td>
			<td>Sigma Aldrich</td>
			<td>278475</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3-chloroperbenzoic acid, m-CPBA</td>
			<td>Sigma Aldrich</td>
			<td>273031</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4-dimethylaminopyridine</td>
			<td>Alfa Aesar</td>
			<td>A13016</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4&#39;,6-diamidino-2-phenylindole, DAPI&#160;</td>
			<td>Invitrogen</td>
			<td>D1306</td>
			<td>Nuclear Stain</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">5-hexynoic acid&#160;</td>
			<td>Alfa Aesar</td>
			<td>B25132-06</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Acetic acid</td>
			<td>VWR</td>
			<td>36289</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Acetone</td>
			<td>Sigma Aldrich</td>
			<td>34850</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Alcohol 200 proof ACS Grade&#160;</td>
			<td>VWR</td>
			<td>71001-866</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Benzene</td>
			<td>Alfa Aesar</td>
			<td>AA33290</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">&#949;-caprolactone&#160;</td>
			<td>Alfa Aesar</td>
			<td>A10299-0E</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Chloroform</td>
			<td>VWR</td>
			<td>BDH1109</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cholesterol</td>
			<td>Sigma Aldrich</td>
			<td>C8503</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Chromium(VI) oxide</td>
			<td>Sigma Aldrich</td>
			<td>232653</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Copper (I) iodide</td>
			<td>Strem Chemicals</td>
			<td>100211-060</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">D,L-Lactide&#160;</td>
			<td>Alfa Aesar</td>
			<td>L09026</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dichloromethane</td>
			<td>Sigma Aldrich</td>
			<td>320269</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Diethyl ether&#160;</td>
			<td>Emd Millipore</td>
			<td>EX0190</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">N,N-Dimethylformamide</td>
			<td>Sigma Aldrich</td>
			<td>270547</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dulbecco&#8217;s modified Eagle medium, DEME&#160;</td>
			<td>CORNING Cellgo</td>
			<td>10-013</td>
			<td>Cell Media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethanol</td>
			<td>Alfa Aesar</td>
			<td>33361</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Formaldehyde&#160;</td>
			<td>SIGMA Life Science</td>
			<td>F8775</td>
			<td>Fixative</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fetal bovine serum, FBS&#160;</td>
			<td>HyClone</td>
			<td>SH30071.01</td>
			<td>Media Component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Filter paper, Grade 415, qualitative, crepe</td>
			<td>VWR</td>
			<td>28320</td>
			<td>Filtration</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glycerol</td>
			<td>Sigma Aldrich</td>
			<td>G5516</td>
			<td>Central node (3-arm)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hexamethylene diisocyanate, HDI</td>
			<td>Sigma Aldrich</td>
			<td>52649</td>
			<td>Crosslinker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Iron(III) chloride&#160;</td>
			<td>Alfa Aesar</td>
			<td>12357</td>
			<td>Etching agent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Isopropyl alcohol</td>
			<td>VWR</td>
			<td>BDH1133</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Methanol</td>
			<td>Alfa Aesar</td>
			<td>L13255</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">N,N&#39;-dicyclohexylcarbodiimide</td>
			<td>Aldrich</td>
			<td>D80002</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">N,N-Dimethylformamide</td>
			<td>Sigma Aldrich</td>
			<td>270547</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nickel metal template</td>
			<td>American Elements</td>
			<td>Ni-860</td>
			<td>Foam template</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Neuroblastomas cells (SH-SY5Y)</td>
			<td>ATCC</td>
			<td>CRL-2266</td>
			<td>Cell line</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Penicillin streptomycin&#160;</td>
			<td>Thermo SCIENTIFIC</td>
			<td>15140122</td>
			<td>Antibiotics</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Polyethylene glycol 2000, PEG</td>
			<td>Alfa Aesar</td>
			<td>B22181</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium azide&#160;</td>
			<td>VWR</td>
			<td>97064-646</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium bicarbonate</td>
			<td>AMRESCO</td>
			<td>865</td>
			<td>Drying salt</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium chloride</td>
			<td>BDH</td>
			<td>BDH9286</td>
			<td>Drying salt</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium phosphate dibasic heptahydrate</td>
			<td>Fisher Scientific</td>
			<td>S-374</td>
			<td>Drying salt</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium phosphate monobasic monohydrate</td>
			<td>Sigma Aldrich</td>
			<td>S9638</td>
			<td>Drying salt</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium sulfate</td>
			<td>Sigma Aldrich</td>
			<td>239313</td>
			<td>Drying salt</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tetrahydrofuran</td>
			<td>Alfa Aesar</td>
			<td>41819</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Thiosulfate de sodium</td>
			<td>AMRESCO</td>
			<td>393</td>
			<td>Drying salt</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tin(II) 2-ethylhexanoate</td>
			<td>Aldrich</td>
			<td>S3252</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Toluene&#160;</td>
			<td>Alfa Aesar</td>
			<td>22903</td>
			<td>Solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triethylamine</td>
			<td>Sigma Aldrich</td>
			<td>471283</td>
			<td>Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Trypsin&#160;</td>
			<td>HyClone</td>
			<td>SH30042.01</td>
			<td>Cell Detachment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Olympus FV1000</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

synthesis of biocompatible liquid crystal elastomer foams as cell scaffolds for 3d spatial cell cultures

Here, we present a step-by-step preparation of a 3D, biodegradable, foam-like cell scaffold. These scaffolds were prepared by cross-linking star block co-polymers featuring cholesterol units as side-chain pendant groups, resulting in smectic-A (SmA) liquid crystal elastomers (LCEs). Foam-like scaffolds, prepared using metal templates, feature interconnected microchannels, making them suitable as 3D cell culture scaffolds. The combined properties of the regular structure of the metal foam and of the elastomer result in a 3D cell scaffold that promotes not only higher cell proliferation compared to conventional porous templated films, but also better management of mass transport (i.e., nutrients, gases, waste, etc.). The nature of the metal template allows for the easy manipulation of foam shapes (i.e., rolls or films) and for the preparation of scaffolds of different pore sizes for different cell studies while preserving the interconnected porous nature of the template. The etching process does not affect the chemistry of the elastomers, preserving their biocompatible and biodegradable nature. We show that these smectic LCEs, when grown for extensive time periods, enable the study of clinically relevant and complex tissue constructs while promoting the growth and proliferation of cells.

This report shows the preparation method of a porous 3D LCE as a scaffold for cell culture using a nickel metal template. The obtained 3D LCE demonstrates a complex interconnected channel network that allows for easy cell infiltration, as well as more suitable mass transport27. It was found that cells are able to fully penetrate the interconnected channel network and are also able to align within the LCE. Here, a metal nickel foam (99% Ni, density of 860 g/cm2...

Watch this Scientific Journal Video about Synthesis of Biocompatible Liquid Crystal Elastomer Foams as Cell Scaffolds for 3D Spatial Cell Cultures at JoVE.com

Synthesis of Biocompatible Liquid Crystal Elastomer Foams as Cell Scaffolds for 3D Spatial Cell Cultures

This study presents a methodology to prepare 3D, biodegradable, foam-like cell scaffolds based on biocompatible side-chain liquid crystal elastomers (LCEs). Confocal microscopy experiments show that foam-like LCEs allow for cell attachment, proliferation, and the spontaneous alignment of C2C12s myoblasts.

Here, we present a step-by-step preparation of a 3D, biodegradable, foam-like cell scaffold. These scaffolds were prepared by cross-linking star block ...

The goal of this procedure is to prepare biodegradable, three dimensional foam-like cell scaffolds based on biocompatible side chain liquid crystal elastomers. This method can help answer key questions in the liquid crystal and biomedical fields, such as the effects of liquid crystal elastomer properties on cell proliferation and alignment. The main advantage of this method of two dimensional cell scaffolds is it permits the study of spatial cell-cell interactions which is rarely possible in 2D macro environments.Generally, those new to this method will struggle with the tactile compression tests. We first had the idea for this method after having to change the media in hundreds of Petri dishes. We wondered if liquid crystal elastomers could support muscle cells on a 3D network, to eliminate the use of so many Petri dishes.Visual demonstration of this method is critical, as some steps require careful manipulation of chemicals. Further, shaping the metal foam template may be challenging. First, fill a 20 milliliter ampoule with a 2%by volume solution of PFOTES in toluene.Stir the solution in the ampoule for 24 hours to silanize the ampoule interior. Rinse the silanized ampoule with isopropyl alcohol and dry it at 140 degrees celsius for 30 minutes. Place 3.64 grams of distilled epsilon-caprolactone, 0.5 grams of alpha-chloro-epsilon-caprolactone, and 0.25 milliliters of glycerol in the dry ampoule.Vortex the mixture for one minute. Then, add 4.90 grams of DL-lactide to the mixture, and purge the ampoule atmosphere with nitrogen gas for one minute. Cover the ampoule opening with aluminum foil, and heat the mixture at 120 degrees Celsius for about two hours to melt the DL-lactide.Vortex the mixture to disrupt any unmelted solids, and then, add 66 microliters of 10-2-ethylhexanoate to the ampoule, and vortex again. Close the ampoule with aluminum foil and heat the mixture at 120 degrees Celsius for 10 minutes to remelt the DL-lactide. Once the DL-lactide has melted again, vigorously vortex the mixture, and purge the ampoule atmosphere with nitrogen gas.Seal the ampoule with a rubber septum. Insert a needle connected to a vacuum line through the septum, and start the vacuum. Flame-seal the neck of the ampoule, being careful not to melt the rubber stopper.Once the neck is sealed, heat the reaction mixture at 140 degrees Celsius for 48 hours. Then, allow the mixture to cool to room temperature. Break open the ampoule and dissolve the viscous reaction mixture in 10 milliliters of dichloromethane.Transfer the mixture to a separatory funnel. Place a flask containing 100 milliliters of methanol in a dry ice and acetone bath to cool down the methanol to approximately minus 78 degrees Celsius. Once the methanol has cooled down, secure the separatory funnel over the flask.Add the reaction mixture to the cold methanol at a rate of two drops every second. Collect the resulting white precipitate on filter paper. Dry the precipitate in a vacuum oven between 50 and 60 degrees Celsius to obtain the three-arm alpha-chloro SBC product.To prepare the alpha cholesteryl three-arm SBC, the pendant chlorine atom is replaced by an azide. A click reaction with cholesteryl 5-hexynoate results in a pendant cholesteryl as the liquid crystal moiety. To begin preparing the liquid crystal elastomer scaffold, combine 0.75 grams of alpha-cholesteryl three-arm SBC with 0.25 milliliters of HDI and 0.24 milliliters of distilled epsilon-caprolactone.Add to this 60 microliters of 10-2-ethylhexanoate and vortex the mixture. Then, cut out a one centimeter by four centimeter piece of nickel metal foam. Roll the nickel foam into a cylinder one centimeter in diameter and one centimeter tall to form a template for the liquid crystal elastomer foam scaffold.Place the template in a glass vial or aluminum foil enclosure, and pour the liquid crystal elastomer mixture over the template until it is completely covered. Allow the template to sit in the liquid crystal elastomer mixture for two minutes, and then, remove the excess with a pipette. Heat the mixture and template at 80 degrees Celsius overnight.Then, peel away the aluminum foil, or break the glass. Use a razor blade to remove excess liquid crystal elastomer to expose the nickel metal template. Place the foam in a flask and add 70 milliliters of a saturated aqueous solution of iron three chloride.Stir the foam in the solution for three days at room temperature to dissolve the nickel template. Every 24 hours, stir the foam in deionized water for 30 minutes, and then, resume stirring in a fresh iron three chloride solution. After the second day of stirring, perform a tactile compression test on the liquid crystal elastomer foam.Resistance to tactile compression indicates that the nickel template is still present in the foam. After the third day, all nickel template has been eliminated, and the resulting foam appears very soft and easy to fully compress. The nickel template must be completely eliminated.It is important to thoroughly rinse the liquid crystal elastomer foam in iron chloride until it's soft to the touch when a tactile compression test is performed. The liquid crystal elastomer foam scaffold is now ready to be characterized and used. Once the liquid crystal elastomer foam is soft, rinse it with 70%ethanol to sterilize it.To begin the seeding procedure, wash again the liquid crystal elastomer foam scaffolds twice in one milliliter of 70%ethanol to sterilize the elastomer surfaces. Then, irradiate the scaffolds with UV light for 10 minutes. Wash the scaffolds with another one milliliter portion of 70%ethanol.Rinse the scaffolds with one milliliter each of sterile water and phosphate-buffered saline. Load the sterilized liquid crystal elastomer scaffolds into 24-well culture plates. Prepare and count a suspension of the cells of interest in the appropriate cell growth medium with penicillin and streptomycin.Dilute the cell suspension to 1.5 times 10 to the fifth cells per 100 microliters using growth medium. Deposit a drop of diluted cell suspension on top of each liquid crystal elastomer scaffold. Incubate the seeded liquid crystal elastomer scaffolds at 37 degrees Celsius in a 5%CO2 atmosphere for two hours.Add another 0.5 milliliters of growth medium to each scaffold, and continue incubation. Every 48 hours, wash the seeded scaffolds with one milliliter of PBS, and add fresh growth medium. Continue incubating the scaffolds until the cells are ready for microscopy.These smetic LCs enable the study of complex tissue constructs while promoting cell growth and proliferation. In order to maintain cell viability, foams must be sterilized and cleanliness of cultures maintained at all times. To prepare for microscopy, fix the cells on the scaffolds with a solution of 4%paraformaldehyde in PBS for 15 minutes.Soak the samples three times in three milliliters of PBS for five minutes. Place one scaffold sample in an Eppendorf tube. Stain the sample with a solution of 0.1%DAPI in 500 microliters of PBS for 10 minutes.Soak the sample twice in one milliliter of PBS for five minutes. And then, immediately image the sample with confocal microscopy. Acquire image stacks spanning the sample and analyze the data in an image processing program.A three-arm SBC with liquid crystal moieties was cast on a nickel foam template with HDI as the cross-linker. The nickel template was removed by etching to obtain the liquid crystal elastomer foam. Compression deformation testing was periodically performed to monitor the etching process.Once the nickel had been completely dissolved, the compression deformation testing showed a 70%reduction in size when compressed. Upon releasing compression, the liquid crystal elastomer foam consistently recovered its original size and shape. This behavior is attributed to the liquid crystal moieties, as similar elastomer foams lacking the cholesterol epsilon-caprolactone moiety did not recover from compression.SCM of the internal foam morphology showed an interconnected network of hollow foam struts. The regular morphology was attributed to the structure of the nickel foam, indicating that pore size and overall shape can be controlled by selection of an appropriate metal template. The foam was seeded with neuroblastoma cells, which attached to the walls of the network within two days.30 days after seeding, confocal microscopy revealed that the cells extended over the liquid crystal elastomer network, and had formed multiple layers dispersed throughout the elastomer foam. Elongation of cell nuclei was observed, and was correlated to cell alignment. Once mastered, this technique can be done within three to four weeks if performed properly.After watching this video, you should have a good understanding of how to design and prepare liquid crystal elastomer cell scaffolds with specific pore sizes and morphologies. While attempting this procedure, it's important to fully characterize each product and to monitor cell viability and expansion. Further, proper staining technique is important to easily acquire confocal microscopy images.Following this procedure, liquid crystal elastomers can also be exposed to external stimuli, such as stress, or magnetic and electric fields, to answer additional questions about how the anisotropic molecular ordering of the liquid crystal elastomers affects cell response. The implications of this technique apply to the study of disease processes, as it provides a platform to dynamically study the effects of external agents on simulated disease activity, and subsequent repair processes. Though this smectic liquid crystal elastomer foam can provide insight into cell-cell interactions, they can also be used with other materials, such as semiconductor or metal nanostructures.After its development, this technique paved the way for researchers in biomedical fields to design long-term experimental platforms mirroring living systems.

synthesis-biocompatible-liquid-crystal-elastomer-foams-as-cell

Research

JoVE Journal

Bioengineering

Alginate Microcapsule as a 3D Platform for Propagation and Differentiation of Human Embryonic Stem Cells (hESC) to Different Lineages

Human embryonic stem cells (hESC) are emerging as an attractive alternative source for cell replacement therapy since they can be expanded in culture indefinitely and differentiated to any cell types in the body. Various types of biomaterials have also been used in stem cell cultures to provide a microenvironment mimicking the stem cell niche1-3. The latter is important for promoting cell-to-cell interaction, cell proliferation, and differentiation into specific lineages as well as tissue organization by providing a three-dimensional (3D) environment4 such as encapsulation. The principle of cell encapsulation involves entrapment of living cells within the confines of semi-permeable membranes in 3D cultures2. These membranes allow for the exchange of nutrients, oxygen and stimuli across the membranes, whereas antibodies and immune cells from the host that are larger than the capsule pore size are excluded5. Here, we present an approach to culture and differentiate hESC DA neurons in a 3D microenvironment using alginate microcapsules. We have modified the culture conditions2 to enhance the viability of encapsulated hESC. We have previously shown that the addition of p160-Rho-associated coiled-coil kinase (ROCK) inhibitor, Y-27632 and human fetal fibroblast-conditioned serum replacement medium (hFF-CM) to the 3D platform significantly enhanced the viability of encapsulated hESC in which the cells expressed definitive endoderm marker genes1. We have now used this 3D platform for the propagation of hESC and efficient differentiation to DA neurons. Protein and gene expression analyses after the final stage of DA neuronal differentiation showed an increased expression of tyrosine hydroxylase (TH), a marker for DA neurons, &gt;100 folds after 2 weeks. We hypothesized that our 3D platform using alginate microcapsules may be useful to study the proliferation and directed differentiation of hESC to various lineages. This 3D system also allows the separation of feeder cells from hESC during the process of differentiation and also has potential for immune-isolation during transplantation in the future.

Alginate Microcapsule as a 3D Platform for Propagation and Differentiation of Human Embryonic Stem Cells hESC to Different Lineages

We have optimized a microencapsulation technique as an effective 3D platform for propagation and differentiation of embryonic stem cells to endoderm and dopaminergic (DA) neurons. It also provides an opportunity for immune-isolation of cells from the host during transplantation. This platform can be adapted for other cell types.

Human embryonic stem cells (hESC) are emerging as an attractive alternative source for cell replacement therapy since they can be expanded in culture ...

Preparation of 3D Fibrin Scaffolds for Stem Cell Culture Applications

Stem cells are found in naturally occurring 3D microenvironments in vivo, which are often referred to as the stem cell niche 1. Culturing stem cells inside of 3D biomaterial scaffolds provides a way to accurately mimic these microenvironments, providing an advantage over traditional 2D culture methods using polystyrene as well as a method for engineering replacement tissues 2. While 2D tissue culture polystrene has been used for the majority of cell culture experiments, 3D biomaterial scaffolds can more closely replicate the microenvironments found in vivo by enabling more accurate establishment of cell polarity in the environment and possessing biochemical and mechanical properties similar to soft tissue.3 A variety of naturally derived and synthetic biomaterial scaffolds have been investigated as 3D environments for supporting stem cell growth. While synthetic scaffolds can be synthesized to have a greater range of mechanical and chemical properties and often have greater reproducibility, natural biomaterials are often composed of proteins and polysaccharides found in the extracelluar matrix and as a result contain binding sites for cell adhesion and readily support cell culture. Fibrin scaffolds, produced by polymerizing the protein fibrinogen obtained from plasma, have been widely investigated for a variety of tissue engineering applications both in vitro and in vivo 4. Such scaffolds can be modified using a variety of methods to incorporate controlled release systems for delivering therapeutic factors 5. Previous work has shown that such scaffolds can be used to successfully culture embryonic stem cells and this scaffold-based culture system can be used to screen the effects of various growth factors on the differentiation of the stem cells seeded inside 6,7.
 This protocol details the process of polymerizing fibrin scaffolds from fibrinogen solutions using the enzymatic activity of thrombin. The process takes 2 days to complete, including an overnight dialysis step for the fibrinogen solution to remove citrates that inhibit polymerization. These detailed methods rely on fibrinogen concentrations determined to be optimal for embryonic and induced pluripotent stem cell culture. Other groups have further investigated fibrin scaffolds for a wide range of cell types and applications - demonstrating the versatility of this approach 8-12.

This work details the preparation of 3D fibrin scaffolds for culturing and differentiating plutipotent stem cells. Such scaffolds can be used to screen the effects of various biological compounds on stem cell behavior as well as modified to contain drug delivery systems.

Stem cells are found in naturally occurring 3D microenvironments in vivo, which are often referred to as the stem cell niche 1. Culturing stem cells ...

Self-reporting Scaffolds for 3-Dimensional Cell Culture

Culturing cells in 3D on appropriate scaffolds is thought to better mimic the in vivo microenvironment and increase cell-cell interactions. The resulting 3D cellular construct can often be more relevant to studying the molecular events and cell-cell interactions than similar experiments studied in 2D. To create effective 3D cultures with high cell viability throughout the scaffold the culture conditions such as oxygen and pH need to be carefully controlled as gradients in analyte concentration can exist throughout the 3D construct. Here we describe the methods of preparing biocompatible pH responsive sol-gel nanosensors and their incorporation into poly(lactic-co-glycolic acid) (PLGA) electrospun scaffolds along with their subsequent preparation for the culture of mammalian cells. The pH responsive scaffolds can be used as tools to determine microenvironmental pH within a 3D cellular construct. Furthermore, we detail the delivery of pH responsive nanosensors to the intracellular environment of mammalian cells whose growth was supported by electrospun PLGA scaffolds. The cytoplasmic location of the pH responsive nanosensors can be utilized to monitor intracellular pH (pHi) during ongoing experimentation.

Biocompatible pH responsive sol-gel nanosensors can be incorporated into poly(lactic-co-glycolic acid) (PLGA) electrospun scaffolds. The produced self-reporting scaffolds can be used for in&#160;situ monitoring of microenvironmental conditions whilst culturing cells upon the scaffold. This is beneficial as the 3D cellular construct can be monitored in real-time without disturbing the experiment.

Culturing cells in 3D on appropriate scaffolds is thought to better mimic the in vivo microenvironment and increase cell-cell interactions. The resulting ...

Fabrication of Mechanically Tunable and Bioactive Metal Scaffolds for Biomedical Applications

Biometal systems have been widely used for biomedical applications, in particular, as load-bearing materials. However, major challenges are high stiffness and low bioactivity of metals. In this study, we have developed a new method towards fabricating a new type of bioactive and mechanically reliable porous metal scaffolds-densified porous Ti scaffolds. The method consists of two fabrication processes, 1) the fabrication of porous Ti scaffolds by dynamic freeze casting, and 2) coating and densification of the porous scaffolds. The dynamic freeze casting method to fabricate porous Ti scaffolds allowed the densification of porous scaffolds by minimizing the chemical contamination and structural defects. The densification process is distinctive for three reasons. First, the densification process is simple, because it requires a control of only one parameter (degree of densification). Second, it is effective, as it achieves mechanical enhancement and sustainable release of biomolecules from porous scaffolds. Third, it has broad applications, as it is also applicable to the fabrication of functionally graded porous scaffolds by spatially varied strain during densification.

Bioactive and mechanically reliable metal scaffolds have been fabricated through a method which consists of two processes, dynamic freeze casting for the fabrication of porous Ti, and coating and densification of the Ti scaffolds. The densification process is simple, effective and applicable to the fabrication of functionally graded scaffolds.

Biometal systems have been widely used for biomedical applications, in particular, as load-bearing materials. However, major challenges are high stiffness ...

Alternating Magnetic Field-Responsive Hybrid Gelatin Microgels for Controlled Drug Release

Magnetically-responsive nano/micro-engineered biomaterials that enable a tightly controlled, on-demand drug delivery have been developed as new types of smart soft devices for biomedical applications. Although a number of magnetically-responsive drug delivery systems have demonstrated efficacies through either in vitro proof of concept studies or in vivo preclinical applications, their use in clinical settings is still limited by their insufficient biocompatibility or biodegradability. Additionally, many of the existing platforms rely on sophisticated techniques for their fabrications. We recently demonstrated the fabrication of biodegradable, gelatin-based thermo-responsive microgel by physically entrapping poly(N-isopropylacrylamide-co-acrylamide) chains as a minor component within a three-dimensional gelatin network. In this study, we present a facile method to fabricate a biodegradable drug release platform that enables a magneto-thermally triggered drug release. This was achieved by incorporating superparamagnetic iron oxide nanoparticles and thermo-responsive polymers within gelatin-based colloidal microgels, in conjunction with an alternating magnetic field application system.

We present a facile method to fabricate a biodegradable gelatin-based drug release platform that is magneto-thermally responsive. This was achieved by incorporating superparamagnetic iron oxide nanoparticles and poly(N-isopropylacrylamide-co-acrylamide) within a spherical gelatin micro-network crosslinked by genipin, in conjunction with an alternating magnetic field application system.

Magnetically-responsive nano/micro-engineered biomaterials that enable a tightly controlled, on-demand drug delivery have been developed as new types of ...

Preparation of Monodomain Liquid Crystal Elastomers and Liquid Crystal Elastomer Nanocomposites

LCEs are shape-responsive materials with fully reversible shape change and potential applications in medicine, tissue engineering, artificial muscles, and as soft robots. Here, we demonstrate the preparation of shape-responsive liquid crystal elastomers (LCEs) and LCE nanocomposites along with characterization of their shape-responsiveness, mechanical properties, and microstructure. Two types of LCEs &#8212; polysiloxane-based and epoxy-based &#8212; are synthesized, aligned, and characterized. Polysiloxane-based LCEs are prepared through two crosslinking steps, the second under an applied load, resulting in monodomain LCEs. Polysiloxane LCE nanocomposites are prepared through the addition of conductive carbon black nanoparticles, both throughout the bulk of the LCE and to the LCE surface. Epoxy-based LCEs are prepared through a reversible esterification reaction. Epoxy-based LCEs are aligned through the application of a uniaxial load at elevated (160 &#176;C) temperatures. Aligned LCEs and LCE nanocomposites are characterized with respect to reversible strain, mechanical stiffness, and liquid crystal ordering using a combination of imaging, two-dimensional X-ray diffraction measurements, differential scanning calorimetry, and dynamic mechanical analysis. LCEs and LCE nanocomposites can be stimulated with heat and/or electrical potential to controllably generate strains in cell culture media, and we demonstrate the application of LCEs as shape-responsive substrates for cell culture using a custom-made apparatus.

We demonstrate the preparation of siloxane-based and epoxy-based liquid crystal elastomers (LCEs) and LCE nanocomposites. The LCEs are characterized with respect to reversible strain, liquid crystal ordering, and stiffness. As a potential application, we demonstrate their use as shape-responsive substrates in a custom device for active cell culture.

LCEs are shape-responsive materials with fully reversible shape change and potential applications in medicine, tissue engineering, artificial muscles, and ...

Micropatterning and Assembly of 3D Microvessels

In vitro platforms to study endothelial cells and vascular biology are largely limited to 2D endothelial cell culture, flow chambers with polymer or glass based substrates, and hydrogel-based tube formation assays. These assays, while informative, do not recapitulate lumen geometry, proper extracellular matrix, and multi-cellular proximity, which play key roles in modulating vascular function. This manuscript describes an injection molding method to generate engineered vessels with diameters on the order of 100 &#181;m. Microvessels are fabricated by seeding endothelial cells in a microfluidic channel embedded within a native type I collagen hydrogel. By incorporating parenchymal cells within the collagen matrix prior to channel formation, specific tissue microenvironments can be modeled and studied. Additional modulations of hydrodynamic properties and media composition allow for control of complex vascular function within the desired microenvironment. This platform allows for the study of perivascular cell recruitment, blood-endothelium interactions, flow response, and tissue-microvascular interactions. Engineered microvessels offer the ability to isolate the influence from individual components of a vascular niche and precisely control its chemical, mechanical, and biological properties to study vascular biology in both health and disease.

This manuscript presents an injection molding method to engineer microvessels that recapitulate physiological properties of endothelium. The microfluidic-based process creates patent 3D vascular networks with tailorable conditions, such as flow, cellular composition, geometry, and biochemical gradients. The fabrication process and examples of potential applications are described.

In vitro platforms to study endothelial cells and vascular biology are largely limited to 2D endothelial cell culture, flow chambers with polymer or glass ...

Fabrication of Extracellular Matrix-derived Foams and Microcarriers as Tissue-specific Cell Culture and Delivery Platforms

Cell function is mediated by interactions with the extracellular matrix (ECM), which has complex tissue-specific composition and architecture. The focus of this article is on the methods for fabricating ECM-derived porous foams and microcarriers for use as biologically-relevant substrates in advanced 3D in vitro cell culture models or as pro-regenerative scaffolds and cell delivery systems for tissue engineering and regenerative medicine. Using decellularized tissues or purified insoluble collagen as a starting material, the techniques can be applied to synthesize a broad array of tissue-specific bioscaffolds with customizable geometries. The approach involves mechanical processing and mild enzymatic digestion to yield an ECM suspension that is used to fabricate the three-dimensional foams or microcarriers through controlled freezing and lyophilization procedures. These pure ECM-derived scaffolds are highly porous, yet stable without the need for chemical crosslinking agents or other additives that may negatively impact cell function. The scaffold properties can be tuned to some extent by varying factors such as the ECM suspension concentration, mechanical processing methods, or synthesis conditions. In general, the scaffolds are robust and easy to handle, and can be processed as tissues for most standard biological assays, providing a versatile and user-friendly 3D cell culture platform that mimics the native ECM composition. Overall, these straightforward methods for fabricating customized ECM-derived foams and microcarriers may be of interest to both biologists and biomedical engineers as tissue-specific cell-instructive platforms for in vitro and in vivo applications.

The tissue-specific extracellular matrix (ECM) is a key mediator of cell function. This article describes methods for synthesizing pure ECM-derived foams and microcarriers that are stable in culture without the need for chemical crosslinking for applications in advanced 3D in vitro cell culture models or as pro-regenerative bioscaffolds.

Cell function is mediated by interactions with the extracellular matrix (ECM), which has complex tissue-specific composition and architecture. The focus ...

A Microcontroller Operated Device for the Generation of Liquid Extracts from Conventional Cigarette Smoke and Electronic Cigarette Aerosol

Electronic cigarettes are the most popular tobacco product among middle and high schoolers and are the most popular alternative tobacco product among adults. High quality, reproducible research on the consequences of electronic cigarette use is essential for understanding emerging public health concerns and crafting evidence based regulatory policy. While a growing number of papers discuss electronic cigarettes, there is little consistency in methods across groups and very little consensus on results. Here, we describe a programmable laboratory device that can be used to create extracts of conventional cigarette smoke and electronic cigarette aerosol. This protocol details instructions for the assembly and operation of said device, and demonstrates the use of the generated extract in two sample applications: an in vitro cell viability assay and gas-chromatography mass-spectrometry. This method provides a tool for making direct comparisons between conventional cigarettes and electronic cigarettes, and is an accessible entry point into electronic cigarette research.

Here, we describe a programmable laboratory device that can be used to create extracts of conventional cigarette smoke and electronic cigarette aerosol. This method provides a useful tool for making direct comparisons between conventional cigarettes and electronic cigarettes, and is an accessible entry point into electronic cigarette research.

Electronic cigarettes are the most popular tobacco product among middle and high schoolers and are the most popular alternative tobacco product among ...

Simultaneous Quantification of Selected Kynurenines Analyzed by Liquid Chromatography-Mass Spectrometry in Medium Collected from Cancer Cell Cultures

The kynurenine pathway and the tryptophan catabolites called kynurenines have received increased attention for their involvement in immune regulation and cancer biology. An in vitro cell culture assay is often used to learn about the contribution of different tryptophan catabolites in a disease mechanism and for testing therapeutic strategies. Cell culture medium that is rich in secreted metabolites and signaling molecules reflects the status of tryptophan metabolism and other cellular events. New protocols for the reliable quantification of multiple kynurenines in the complex cell culture medium are desired to allow for a reliable and quick analysis of multiple samples. This can be accomplished with liquid chromatography coupled with mass spectrometry. This powerful technique is employed in many clinical and research laboratories for the quantification of metabolites and can be used for measuring kynurenines.
Presented here is the use of liquid chromatography coupled with single quadrupole mass spectrometry (LC-SQ) for the simultaneous determination of four kynurenines, i.e., kynurenine, 3-hydroxykynurenine, 3-hydroxyanthranilic, and xanthurenic acid in the medium collected from in vitro cultured cancer cells. SQ detector is simple to use and less expensive compared to other mass spectrometers. In the SQ-MS analysis, multiple ions from the sample are generated and separated according to their specific mass-to-charge ratio (m/z), followed by the detection using a Single Ion Monitoring (SIM) mode.
This paper draws the attention on the advantages of the reported method and indicates some weak points. It is focused on critical elements of LC-SQ analysis including sample preparation along with chromatography and mass spectrometry analysis. The quality control, method calibration conditions and matrix effect issues are also discussed. We described a simple application of 3-nitrotyrosine as one analog standard for all target analytes. As confirmed by experiments with human ovary and breast cancer cells, the proposed LC-SQ method&#160;generates reliable results and can be further applied to other in vitro cellular models.

Described here is a protocol for the determination of four different tryptophan metabolites generated in the kynurenine pathway (kynurenine, 3-hydroxykynurenine, xanthurenic acid, 3-hydroxyanthranilic acid) in the medium collected from cancer cell cultures analyzed by liquid chromatography coupled with a single quadrupole mass spectrometry.

The kynurenine pathway and the tryptophan catabolites called kynurenines have received increased attention for their involvement in immune regulation and ...