This work was conducted using the facilities of the Biomedical Engineering Department at Florida International University.

1. Electrospinning Collector Setup
<ol>
	<li>Cut the aluminum foil into a rectangular piece.</li>
	<li>Fold the rectangular piece into a rectangular strip, and attach it perpendicular to a flat metal plate with tape (Figure 1). Note: The size of the fiber mat depends on the length and width of the strip. Thus, the strip dimensions can be adjusted as needed.</li>
</ol>
2. Polymeric Solution Preparation
<ol>
	<li>Mix glycerol and dodecanedioic acid (DDA) in 1:1 molar ratio in a beaker at 120 &#176;C for 100 hr to obtain PGD polymer.</li>
	<li>Dissolve poly(ethylene oxide) (PEO) and gelatin in 65% ethanol with a weight ratio of 1.5:3:95.5 in a 15 ml tube, tighten the cap and heat the mixture in an oven at 60 &#176;C for 1 hr with stirring until it becomes a homogeneous solution (Basal solution).</li>
	<li>For electrospinning, mix the PGD polymer and the basal solution in 4:6 weight ratio. Note: PGD concentration has a big effect on fiber diameter. 30%-50% percent PGD is acceptable to produce fibers longer than 5 cm with increased fiber diameters.</li>
	<li>Add 0.1% riboflavin to the polymeric solution and mix well.</li>
</ol>
3. Electrospinning
<ol>
	<li>Feed the polymeric solution into a 5 ml standard syringe with an 18 G blunted stainless steel needle.</li>
	<li>Insert the syringe into a syringe pump.</li>
	<li>Attach the grounded lead of a high voltage power source to the metal plate and the positively charged lead to the needle.</li>
	<li>Adjust the distance between the needle and the aluminum foil strip to 15 cm.</li>
	<li>Place the syringe pump in an angle of about 15&#176;&#160;with the horizontal to prevent aggregation of the fibers at the front of the strip.</li>
	<li>Turn on the syringe pump and adjust the flow rate of the pump to 0.6 ml/hr.</li>
	<li>Turn on the high voltage power source and set the operating voltage to 14.6 kV.</li>
</ol>
4. Fiber Processing
<ol>
	<li>After the collection is complete, expose the fiber mat to UV light for 60 min for cross-linking.</li>
	<li>Transfer the fiber mat from the aluminum foil strip to a 100&#160;mm Petri dish, and expose it to UV light for another 20 min for sterilization.</li>
	<li>In a biosafety cabinet, cut the fiber mat into round pieces of the same size with a surgical blade and place the pieces into a 24-well plate.</li>
	<li>For cell pre-seeding treatment, immerse fiber samples in 1 ml of phosphate buffered saline (PBS) and incubate at 37 &#176;C overnight.</li>
	<li>On the following day, aspirate PBS carefully, add 1 ml of differentiation medium (DMEM/F12, N2, and FGF2) (see recipe in Materials table) to each well and incubate at 37 &#176;C for 3 hr.</li>
	<li>Aspirate differentiation medium carefully, add 0.2 ml of matrigel to each fiber sample and incubate at 37 &#176;C for 30 min. Note: Laminin can also be used for fiber coating. Add 0.2 ml of 20 &#181;g/ml laminin to the fiber and incubate at room temperature for 3 hr.</li>
	<li>Carefully remove excess matrigel from each well. Rinse with 2 ml of differentiation medium once. Note: The fiber samples are ready for cell culture.</li>
</ol>
5. Cell Seeding on Fibers
<ol>
	<li>Add 1 ml of Accutase to the mES cell culture dish and incubate for 10 min at 37 &#176;C.</li>
	<li>After 10 min, the mES cells are detached from the culture dish. Add 4 ml of differentiation medium to the plate. Collect the floating mES cells into a 15&#160;ml tube and pipette cells up and down to break colonies (about 15x).</li>
	<li>Centrifuge at 400 x&#160;g for 5 min and re-suspend cells in 4 ml of differentiation medium.</li>
	<li>Count the cells using a hemocytometer. Transfer 200 &#181;l of the cell suspension into a 15 ml tube and dilute it 10x&#160;with differentiation medium. Transfer 15 &#181;l of the diluted cell suspension to a chamber on the hemocytometer with a cover-slip in place. Count the cells in the 1 mm center square and the four corner squares of the hemocytometer under the microscope. Note: Cell per ml = the average count per square x&#160;the dilution factor x&#160;104</li>
	<li>Place approximately 5 x 104 mES cells onto each well. Slowly drop the cell suspension onto the middle of the fiber samples, instead of sliding off to the side of the well, to prevent the solution from draining off the fiber mat.</li>
	<li>Add 1 ml of differentiation medium to each well, and keep the plate in an incubator at 37 &#176;C and 5% CO2 to allow cells attachment, growth and differentiation.</li>
	<li>Aspirate the old medium from each well and replace with 1 ml of fresh differentiation medium every other day.</li>
</ol>
6. Cell Viability
<ol>
	<li>Aspirate the old medium from each well.</li>
	<li>Mix 1/10th volume of Resazurin fluorescence reagent with culture medium and add 1 ml to each well.</li>
	<li>Incubate at 37 &#176;C and 5% CO2 for 4 hr, protected from direct light.</li>
	<li>After 4 hr, transfer 100 &#181;l 3x of the reagent from each well to a 96-well plate, and then the samples are ready to be measured on a fluorescence spectrophotometer using 560EX nm/590EM filter settings.</li>
</ol>
7. Real Time PCR
<ol>
	<li>After 14 days of culture, add lysis buffer to the samples and isolate total RNA from the cells on the fiber samples.</li>
	<li>Use 4 &#181;l of total RNA to synthesize cDNA in 20 &#181;l reaction scales by reverse transcription.</li>
	<li>Prepare the PCR reaction mixture in each optical tube: 10 &#181;l Master Mix (2x), 0.2 &#181;l dye, 8 &#181;l Nuclease-Free water, 1 &#181;l cDNA, and 1 &#181;l primer (Primers used in this study are listed in Table 1).</li>
	<li>Set up the PCR program: a. 95 &#176;C 2:20 min, 1 cycle b. 95 &#176;C 3 sec&#8594;60&#176; C 1 min, 40 cycle c. 95&#176; C 15 sec, 1 cycle d. 60&#176; C 1 min, 1 cycle e. 95&#176; C 15 sec, 1 cycle. Choose comparative CT method to determine relative gene expression levels.</li>
	<li>After PCR is finished, analyze the real-time PCR results with StepOne software and export the results to Excel.</li>
</ol>

<ol>
	<li>Migneco, F., Huang, Y. -. C., Birla, R. K., Hollister, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Poly+(glycerol-dodecanoate),+a+biodegradable+polyester+for+medical+devices+and+tissue+engineering+scaffolds.">Poly (glycerol-dodecanoate), a biodegradable polyester for medical devices and tissue engineering scaffolds.</a> Biomaterials. 30, 6479-6484 (2009).</li><li>Reneker, D. H., Yarin, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospinning+jets+and+polymer+nanofibers.">Electrospinning jets and polymer nanofibers.</a> Polymer. 49, 2387-2425 (2008).</li><li>Wang, Y., Ameer, G. A., Sheppard, B. J., Langer, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+tough+biodegradable+elastomer.">A tough biodegradable elastomer.</a> Nature biotechnology. 20, 602-606 (2002).</li><li>Panunzi, S., De Gaetano, A., Mingrone, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Approximate+linear+confidence+and+curvature+of+a+kinetic+model+of+dodecanedioic+acid+in+humans.">Approximate linear confidence and curvature of a kinetic model of dodecanedioic acid in humans.</a> American Journal of Physiology-Endocrinology And Metabolism. 289, (2005).</li><li>Park, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Apparatus+for+preparing+electrospun+nanofibers:+designing+an+electrospinning+process+for+nanofiber+fabrication.">Apparatus for preparing electrospun nanofibers: designing an electrospinning process for nanofiber fabrication.</a> Polymer Internationa l. 56, 1361-1366 (2007).</li><li>Barnes, C. P., Sell, S. A., Boland, E. D., Simpson, D. G., Bowlin, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanofiber+technology:+designing+the+next+generation+of+tissue+engineering+scaffolds.">Nanofiber technology: designing the next generation of tissue engineering scaffolds.</a> Advanced drug delivery reviews. 59, 1413-1433 (2007).</li><li>Li, W. -. J., Mauck, R. L., Tuan, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+nanofibrous+scaffolds:+production,+characterization,+and+applications+for+tissue+engineering+and+drug+delivery.">Electrospun nanofibrous scaffolds: production, characterization, and applications for tissue engineering and drug delivery.</a> Journal of Biomedical Nanotechnology. 1, 259-275 (2005).</li><li>Pham, Q. P., Sharma, U., Mikos, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospinning+of+polymeric+nanofibers+for+tissue+engineering+applications:+a+review.">Electrospinning of polymeric nanofibers for tissue engineering applications: a review.</a> Tissue engineering. 12, 1197-1211 (2006).</li><li>Lim, S. H., Mao, H. -. Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+scaffolds+for+stem+cell+engineering.">Electrospun scaffolds for stem cell engineering.</a> Advanced drug delivery reviews. 61, 1084-1096 (2009).</li><li>Lowery, J. L., Datta, N., Rutledge, G. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+fiber+diameter,+pore+size+and+seeding+method+on+growth+of+human+dermal+fibroblasts+in+electrospun+poly+(epsilon-caprolactone)+fibrous+mats.">Effect of fiber diameter, pore size and seeding method on growth of human dermal fibroblasts in electrospun poly (epsilon-caprolactone) fibrous mats.</a> Biomaterials. 31, 491-504 (2010).</li><li>Tillman, B. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+in+vivo+stability+of+electrospun+polycaprolactone-collagen+scaffolds+in+vascular+reconstruction.">The in vivo stability of electrospun polycaprolactone-collagen scaffolds in vascular reconstruction.</a> Biomaterials. 30, 583-588 (2009).</li><li>Ju, Y. M., Choi, J. S., Atala, A., Yoo, J. J., Lee, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bilayered+scaffold+for+engineering+cellularized+blood+vessels.">Bilayered scaffold for engineering cellularized blood vessels.</a> Biomaterials. 31, 4313-4321 (2010).</li><li>McCullen, S. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+collagen+polymerization+of+layered+cell-seeded+electrospun+scaffolds+for+bone+tissue+engineering+applications.">In situ collagen polymerization of layered cell-seeded electrospun scaffolds for bone tissue engineering applications.</a> Tissue Engineering Part C: Methods. 16, 1095-1105 (2010).</li></ol>

No conflicts of interest declared.

The limitations of simple collectors or the complexities of rotating collectors that are currently used for electrospinning increase the restriction of obtaining the desired length and size of fiber mat for some applications. Additionally, transferring fibers from the ground collector to the culture dish or other substrates is a challenge5. In this report, a newly designed collector, made simply by attaching an aluminum foil strip to the grounded collector, was able to obtain large size fiber mats up to 10 cm ...

Electrospinning is one of the effective processing methods to produce micro-to-nanometer size fiber scaffolds. The basic principle of electrospinning involves a Taylor cone of solution that is held at the orifice of a needle by applying high voltage between the tip of the needle and a grounded collector. When the electrostatic repulsion in the solution overcomes the surface tension, a charged fluid jet is ejected out of the needle tip, travels through the air with solvent evaporation, and is finally deposited on the grounded collector. The syringe pump provides a continuous flow of solution emerging from the spinneret and thus multiple copies of the electrospun fibers can be fabricated within a short period of time. During the course of leaving the spinneret to arrive at the collector, the charged jet will undergo stretching and whipping according to a number of parameters that include the viscosity and surface tension of the polymeric solution, the electrostatic force in the solution, and the interaction of the external electric field, etc2.
In the electrospinning process, a collector serves as a conductive substrate where the micro-to-nanometer fibers could be deposited. In this study, a new type of fiber collector was designed to obtain fiber mats with the desired size (length x width). Traditionally, aluminum foil is used as a collector but it is difficult to transfer the fibers from the flat surface to another substrate. The difficulty of harvesting an intact fiber mat from a traditional collector was mainly due to the fact that the electrospun fibers attach strongly to the collector&#39;s surface. Therefore, we modified the collector by folding a piece of aluminum foil into a rectangular strip and attaching it perpendicular to a flat metal plate. The electrospun fibers are stretched across the area between the tip of the strip and the metal plate, which can be easily transferred to another substrate.
Interest in thermally crosslinked elastomeric polymers is rapidly growing because of the pioneering work of Robert Langer&#39;s group, who introduced poly(glycerol sebacate) (PGS), a polyester which is analogous to vulcanized rubber in 2002&#160;3. Similar to PGS, we have successfully developed poly(glycerol-dodecanoate) (PGD) by thermal condensation of glycerol and dodecanedioic acid and demonstrated its unique shape memory property1. Unlike stiffer synthetic materials poly(hydroxyl butyrate) or poly(L-lactide) (Young&#39;s moduli of 250 MPa and 660 MPa, respectively), PGD exhibits elastomeric property like rubber, with a Young&#39;s modulus of 1.08 MPa when the temperature is above 37 &#176;C, which is a close match to the in-situ peripheral nerve (0.45 MPa). In addition, PGD is biodegradable and the degradation time can be fine-tuned by varying the ratio of glycerol and dodecanedioic acid. Dodecanedioic acid is a twelve-carbon substance with two terminal carboxylic groups, HOOC(CH2)10COOH. Even numbered dicarboxylic acids like sebacic acid and dodecanedioic acid can be metabolized to acetyl-CoA and enter the tricarboxylic acid (TCA)/(citric acid) cycle. The metabolic product of dicarboxylic acids, succinyl-CoA, is a gluconeogenetic precursor and intermediate of TCA cycle4. Thus, some studies suggested that they could be utilized as an alternative fuel substrate for enteral and parenteral nutrition, especially in the pathological conditions. In addition, PGD exhibits unique shape memory because its glass transition temperature is 31 &#176;C, thus it shows distinct mechanical properties at room temperature and at body temperature.&#160;In sum, PGD is biodegradable, biocompatible, exhibiting unique elastic properties with mechanical properties similar to nerve tissues; therefore, it is a suitable material for nerve tissue engineering applications. In this protocol, the electrospun long fibers spanning a large deposit area were fabricated via the newly-designed collector from PGD. The fiber scaffolds can support the mouse pluripotent stem cells growth and differentiation.

<table><tbody><tr><td>Glycerol</td><td>Sigma-Aldrich</td><td>G7757</td><td></td></tr><tr><td>Dodecanedioic acid</td><td>Sigma-Aldrich</td><td>D1009</td><td></td></tr><tr><td>Gelatin</td><td>Sigma-Aldrich</td><td>D1890</td><td></td></tr><tr><td>Poly(ethylene oxide) (PEO)</td><td>Sigma-Aldrich</td><td>182028</td><td></td></tr><tr><td>Riboflavin</td><td>Sigma-Aldrich</td><td>132350250</td><td>0.10%</td></tr><tr><td>Mouse embryonic stem cells</td><td>GlobalStem</td><td>GSC-5002</td><td></td></tr><tr><td>Matrigel</td><td>Becton Dickinson</td><td>356234</td><td></td></tr><tr><td>DMEM/F12</td><td>Thermo Scientific</td><td>SH30272.02</td><td></td></tr><tr><td>N2 supplement</td><td>Invitrogen</td><td>17502048</td><td>1%</td></tr><tr><td>FGF2</td><td>Stemgent</td><td>03-0002</td><td>10 ng/ml</td></tr><tr><td>Accutase</td><td>Invitrogen</td><td>A11105-01</td><td></td></tr><tr><td>Phosphate buffered saline (PBS)</td><td>Invitrogen</td><td>10010-031</td><td></td></tr><tr><td>Resazurin fluorescence dye</td><td>Sigma-Aldrich</td><td>62758-13-8</td><td></td></tr><tr><td>SV Total RNA Isolation System</td><td>Promega</td><td>Z3100</td><td></td></tr><tr><td>GoScript Reverse Transcription System</td><td>Promega</td><td>A5000</td><td></td></tr><tr><td>GoTaq qPCR Master Mix</td><td>Promega</td><td>A6001</td><td></td></tr><tr><td>Syringe pump&amp;nbsp;</td><td>Fisher scientific</td><td>14-831-200</td><td></td></tr><tr><td>High voltage power source&amp;nbsp;</td><td>Spellman High Voltage Electronics Corporation</td><td></td><td>SL30</td></tr><tr><td>UV light</td><td>Philips</td><td>308643</td><td>15W/G15T8</td></tr><tr><td>Synergy HT Multi-Mode Microplate Reader</td><td>BioTek</td><td></td><td></td></tr><tr><td>Perkin Elmer GeneAmp PCR System 9600</td><td>Perkin Elmer</td><td>8488</td><td></td></tr><tr><td>StepOne Real-time PCR System</td><td>Applied Biosystems</td><td>4376357</td><td></td></tr></tbody></table>

electrospun fibrous scaffolds of poly(glycerol-dodecanedioate) for engineering neural tissues from mouse embryonic stem cells

For tissue engineering applications, the preparation of biodegradable and biocompatible scaffolds is the most desirable but challenging task. &#160;Among the various fabrication methods, electrospinning is the most attractive one due to its simplicity and versatility. Additionally, electrospun nanofibers mimic the size of natural extracellular matrix ensuring additional support for cell survival and growth. This study showed the viability of the fabrication of long fibers spanning a larger deposit area for a novel biodegradable and biocompatible polymer named&#160;poly(glycerol-dodecanoate) (PGD)1 by using a newly designed collector for electrospinning. PGD exhibits unique elastic properties with similar mechanical properties to nerve tissues, thus it is suitable for neural tissue engineering applications. The synthesis and fabrication set-up for making fibrous scaffolding materials was simple, highly reproducible, and inexpensive. In biocompatibility testing, cells derived from mouse embryonic stem cells could adhere to and grow on the electrospun PGD fibers. In summary, this protocol provided a versatile fabrication method for making PGD electrospun fibers to support the growth of mouse embryonic stem cell derived neural lineage cells.

The major components of the electrospinning are shown in Figure 1. A large size fiber mat was typically obtained through the perpendicularly attached aluminum foil strip and a flat metal plate. Figure 2 shows the collector design and the electrospinning fiber mat. The width and length can be adjusted for different applications. The length of the fiber made with PGD polymer and basal solution mixture is up to 10 cm. The morphology of electrospun fibers is shown in Figure 3</strong...

Watch this Scientific Journal Video about Electrospun Fibrous Scaffolds of Polyglycerol-dodecanedioate for Engineering Neural Tissues From Mouse Embryonic Stem Cells at JoVE.com

Electrospun Fibrous Scaffolds of Polyglycerol-dodecanedioate for Engineering Neural Tissues From Mouse Embryonic Stem Cells

Synthesis and fabrication of electrospun long fibers spanning a larger deposit area via a newly designed collector from a novel biodegradable polymer named poly(glycerol-dodecanoate) (PGD) was reported. The fibers were able to support the growth of cells derived from mouse pluripotent stem cells.

Electrospun Fibrous Scaffolds of Poly(glycerol-dodecanedioate) for Engineering Neural Tissues From Mouse Embryonic Stem Cells

For tissue engineering applications, the preparation of biodegradable and biocompatible scaffolds is the most desirable but challenging task. &#160;Among ...

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Research

JoVE Journal

Bioengineering

10.8K Views.  Florida International University. Synthesis and fabrication of electrospun long fibers spanning a larger deposit area via a newly designed collector from a novel biodegradable polymer named poly(glycerol-dodecanoate) (PGD) was reported. The fibers were able to support the growth of cells derived from mouse pluripotent stem cells.

Video: Electrospun Fibrous Scaffolds of Polyglycerol-dodecanedioate for Engineering Neural Tissues From Mouse Embryonic Stem Cells

The Culture of Primary Motor and Sensory Neurons in Defined Media on Electrospun Poly-L-lactide Nanofiber Scaffolds

Electrospinning is a technique for producing micro- to nano-scale fibers. Fibers can be electrospun with varying degrees of alignment, from highly aligned to completely random. In addition, fibers can be spun from a variety of materials, including biodegradable polymers such as poly-L-lactic acid (PLLA). These characteristics make electrospun fibers suitable for a variety of scaffolding applications in tissue engineering. Our focus is on the use of aligned electrospun fibers for nerve regeneration. We have previously shown that aligned electrospun PLLA fibers direct the outgrowth of both primary sensory and motor neurons in vitro. We maintain that the use of a primary cell culture system is essential when evaluating biomaterials to model real neurons found in vivo as closely as possible. Here, we describe techniques used in our laboratory to electrospin fibrous scaffolds and culture dorsal root ganglia explants, as well as dissociated sensory and motor neurons, on electrospun scaffolds. However, the electrospinning and/or culture techniques presented here are easily adapted for use in other applications.

Aligned electrospun fibers direct the growth of neurons in vitro and are a potential component of nerve regeneration scaffolds. We describe a procedure for preparing electrospun fiber substrates and the serum-free culture of primary rat E15 sensory (DRG) and motor neurons. Visualization of neurons by immunocytochemistry is also included.

Electrospinning is a technique for producing micro- to nano-scale fibers. Fibers can be electrospun with varying degrees of alignment, from highly aligned ...

Neuroscience

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 ...

Cultivation of Human Neural Progenitor Cells in a 3-dimensional Self-assembling Peptide Hydrogel

The influence of 3-dimensional (3D) scaffolds on growth, proliferation and finally neuronal differentiation is of great interest in order to find new methods for cell-based and standardised therapies in neurological disorders or neurodegenerative diseases. 3D structures are expected to provide an environment much closer to the in vivo situation than 2D cultures. In the context of regenerative medicine, the combination of biomaterial scaffolds with neural stem and progenitor cells holds great promise as a therapeutic tool.1-5 Culture systems emulating a three dimensional environment have been shown to influence proliferation and differentiation in different types of stem and progenitor cells. Herein, the formation and functionalisation of the 3D-microenviroment is important to determine the survival and fate of the embedded cells.6-8 Here we used PuraMatrix9,10 (RADA16, PM), a peptide based hydrogel scaffold, which is well described and used to study the influence of a 3D-environment on different cell types.7,11-14 PuraMatrix can be customised easily and the synthetic fabrication of the nano-fibers provides a 3D-culture system of high reliability, which is in addition xeno-free.
Recently we have studied the influence of the PM-concentration on the formation of the scaffold.13 In this study the used concentrations of PM had a direct impact on the formation of the 3D-structure, which was demonstrated by atomic force microscopy. A subsequent analysis of the survival and differentiation of the hNPCs revealed an influence of the used concentrations of PM on the fate of the embedded cells. However, the analysis of survival or neuronal differentiation by means of immunofluorescence techniques posses some hurdles. To gain reliable data, one has to determine the total number of cells within a matrix to obtain the relative number of e.g. neuronal cells marked by &beta;III-tubulin. This prerequisites a technique to analyse the scaffolds in all 3-dimensions by a confocal microscope or a comparable technique like fluorescence microscopes able to take z-stacks of the specimen. Furthermore this kind of analysis is extremely time consuming. 
Here we demonstrate a method to release cells from the 3D-scaffolds for the later analysis e.g. by flow cytometry. In this protocol human neural progenitor cells (hNPCs) of the ReNcell VM cell line (Millipore USA) were cultured and differentiated in 3D-scaffolds consisting of PuraMatrix (PM) or PuraMatrix supplemented with laminin (PML). In our hands a PM-concentration of 0.25% was optimal for the cultivation of the cells13, however the concentration might be adapted to other cell types.12 The released cells can be used for e.g. immunocytochemical studies and subsequently analysed by flow cytometry. This speeds up the analysis and more over, the obtained data rest upon a wider base, improving the reliability of the data.

Here we describe the use of a self-assembling 3-dimensional scaffold to culture human neural progenitor cells. We present a protocol to release the cells from the scaffolds to be analysed subsequently e.g. by flow cytometry. This protocol might be adapted to other cell types to perform detailed mechanistically studies.

The  influence of 3-dimensional (3D) scaffolds on growth, proliferation and finally  neuronal differentiation is of great interest in order to find new ...

Electrospinning Growth Factor Releasing Microspheres into Fibrous Scaffolds

This procedure describes a method to fabricate a multifaceted substrate to direct nerve cell growth. This system incorporates mechanical, topographical, adhesive and chemical signals. Mechanical properties are controlled by the type of material used to fabricate the electrospun fibers. In this protocol we use 30% methacrylated Hyaluronic Acid (HA), which has a tensile modulus of ~500 Pa, to produce a soft fibrous scaffold. Electrospinning on to a rotating mandrel produces aligned fibers to create a topographical cue. Adhesion is achieved by coating the scaffold with fibronectin. The primary challenge addressed herein is providing a chemical signal throughout the depth of the scaffold for extended periods. This procedure describes fabricating&#160;poly(lactic-co-glycolic acid) (PLGA) microspheres that contain Nerve Growth Factor (NGF) and directly impregnating the scaffold with these microspheres during the electrospinning process. Due to the harsh production environment, including high sheer forces and electrical charges, protein viability is measured after production. The system provides protein release for over 60 days and has been shown to promote primary nerve cell growth.

This protocol combines electrospinning and microspheres to develop tissue engineered scaffolds to direct neurons. Nerve growth factor was encapsulated within PLGA microspheres and electrospun into Hyaluronic Acid (HA) fibrous scaffolds. The protein bioactivity was tested by seeding the scaffolds with primary chick Dorsal Root Ganglia and culturing for 4-6 days.

This procedure describes a method to fabricate a multifaceted substrate to direct nerve cell growth.  This system incorporates mechanical, topographical, ...

Electrospun Nanofiber Scaffolds with Gradations in Fiber Organization

The goal of this protocol is to report a simple method for generating nanofiber scaffolds with gradations in fiber organization and test their possible applications in controlling cell morphology/orientation. Nanofiber organization is controlled with a new fabrication apparatus that enables the gradual decrease of fiber organization in a scaffold. Changing the alignment of fibers is achieved through decreasing deposition time of random electrospun fibers on a uniaxially aligned fiber mat. By covering the collector with a moving barrier/mask, along the same axis as fiber deposition, the organizational structure is easily controlled. For tissue engineering purposes, adipose-derived stem cells can be seeded to these scaffolds. Stem cells undergo morphological changes as a result of their position on the varied organizational structure, and can potentially differentiate into different cell types depending on their locations. Additionally, the graded organization of fibers enhances the biomimicry of nanofiber scaffolds so they more closely resemble the natural orientations of collagen nanofibers at tendon-to-bone insertion site compared to traditional scaffolds. Through nanoencapsulation, the gradated fibers also afford the possibility to construct chemical gradients in fiber scaffolds, and thereby further strengthen their potential applications in fast screening of cell-materials interaction and interfacial tissue regeneration. This technique enables the production of continuous gradient scaffolds, but it also can potentially produce fibers in discrete steps by controlling the movement of the moving barrier/mask in a discrete fashion.

Here, we present a protocol to fabricate electrospun nanofiber scaffolds with gradated organization of fibers and explore their applications in regulating cell morphology/orientation. Gradients with regard to physical and chemical properties of the nanofiber scaffolds offer a wide variety of applications in the biomedical field.

The goal of this protocol is to report a simple method for generating nanofiber scaffolds with gradations in fiber organization and test their possible ...

Engineered 3D Silk-collagen-based Model of Polarized Neural Tissue

Despite huge efforts to decipher the anatomy, composition and function of the brain, it remains the least understood organ of the human body. To gain a deeper comprehension of the neural system scientists aim to simplistically reconstruct the tissue by assembling it in vitro from basic building blocks using a tissue engineering approach. Our group developed a tissue-engineered silk and collagen-based 3D brain-like model resembling the white and gray matter of the cortex. The model consists of silk porous sponge, which is pre-seeded with rat brain-derived neurons, immersed in soft collagen matrix. Polarized neuronal outgrowth and network formation is observed with separate axonal and cell body localization. This compartmental architecture allows for the unique development of niches mimicking native neural tissue, thus enabling research on neuronal network assembly, axonal guidance, cell-cell and cell-matrix interactions and electrical functions.

Insight into the complex actions of the brain requires advanced research tools. Here we demonstrate a novel silk-collagen-based 3D engineered model of neural tissue resembling brain-like architecture. The model can be used to study neuronal network assembly, axonal guidance, cell-cell interactions and electrical activity.

Despite huge efforts to decipher the anatomy, composition and function of the brain, it remains the least understood organ of the human body. To gain a ...

Electrospinning Fibrous Polymer Scaffolds for Tissue Engineering and Cell Culture

As the field of tissue engineering evolves, there is a tremendous demand to produce more suitable materials and processing techniques in order to address the requirements (e.g., mechanics and vascularity) of more intricate organs and tissues. Electrospinning is a popular technique to create fibrous scaffolds that mimic the architecture and size scale of the native extracellular matrix. These fibrous scaffolds are also useful as cell culture substrates since the fibers can be used to direct cellular behavior, including stem cell differentiation (see extensive reviews by Mauck et al. and Sill et al. for more information). In this article, we describe the general process of electrospinning polymers and as an example, electrospin a reactive hyaluronic acid capable of crosslinking with light exposure (see Ifkovits et al. for a review on photocrosslinkable materials). We also introduce further processing capabilities such as photopatterning and multi-polymer scaffold formation. Photopatterning can be used to create scaffolds with channels and multi-scale porosity to increase cellular infiltration and tissue distribution. Multi-polymer scaffolds are useful to better tune the properties (mechanics and degradation) of a scaffold, including tailored porosity for cellular infiltration. Furthermore, these techniques can be extended to include a wide array of polymers and reactive macromers to create complex scaffolds that provide the cues necessary for the development of successful tissue engineered constructs.

The process of electrospinning polymers for tissue engineering and cell culture is addressed in this article. Specifically, the electrospinning of photoreactive macromers with additional processing capabilities of photopatterning and multi-polymer electrospinning is described.

As the field of tissue engineering evolves, there is a tremendous demand to produce more suitable materials and processing techniques in order to address ...

Biology

Electrically Conductive Scaffold to Modulate and Deliver Stem Cells

Stem cell therapy has emerged as an exciting stroke therapeutic, but the optimal delivery method remains unclear. While the technique of microinjection has been used for decades to deliver stem cells in stroke models, this technique is limited by the lack of ability to manipulate the stem cells prior to injection. This paper details a method of using an electrically conductive polymer scaffold for stem cell delivery. Electrical stimulation of stem cells using a conductive polymer scaffold alters the stem cell's genes involved in cell survival, inflammatory response, and synaptic remodeling. After electrical preconditioning, the stem cells on the scaffold are transplanted intracranially in a distal middle cerebral artery occlusion rat model. This protocol describes a powerful technique to manipulate stem cells via a conductive polymer scaffold and creates a new tool to further develop stem cell-based therapy.

This protocol describes fabrication of a cell culture system to allow seeding of stem cells on a conductive polymer scaffold for in vitro electrical stimulation and subsequent in vivo implantation of the stem cell-seeded scaffold using a minimally invasive technique.

Stem cell therapy has emerged as an exciting stroke therapeutic, but the optimal delivery method remains unclear. While the technique of microinjection ...

Anatomically Inspired Three-dimensional Micro-tissue Engineered Neural Networks for Nervous System Reconstruction, Modulation, and Modeling

Functional recovery rarely occurs&#160;following injury or disease-induced degeneration within the central nervous system (CNS)&#160;due to the inhibitory environment and the limited capacity for neurogenesis. We are developing&#160;a strategy to simultaneously address&#160;neuronal and axonal pathway loss within the damaged CNS. This manuscript presents the fabrication protocol for micro-tissue engineered neural networks (micro-TENNs), implantable constructs consisting of neurons and aligned axonal tracts spanning the extracellular matrix (ECM) lumen of a preformed hydrogel cylinder hundreds of microns in diameter that may extend centimeters in length. Neuronal aggregates are delimited to the extremes of the three-dimensional encasement and are spanned by axonal projections. Micro-TENNs are uniquely poised as a strategy for CNS reconstruction, emulating aspects of brain connectome cytoarchitecture and potentially providing means for network replacement. The neuronal aggregates may synapse with host tissue to form new functional relays to restore and/or modulate missing or damaged circuitry. These constructs may also act as pro-regenerative&#160;&#34;living scaffolds&#34; capable of exploiting developmental mechanisms for cell migration and axonal pathfinding, providing synergistic structural and soluble cues based on the state of regeneration. Micro-TENNs are fabricated by pouring liquid hydrogel into a cylindrical mold containing a longitudinally centered needle. Once the hydrogel has gelled, the needle is removed, leaving a hollow micro-column. An ECM solution is added to the lumen to provide an environment suitable for neuronal adhesion and axonal outgrowth. Dissociated neurons are mechanically aggregated for precise seeding within one or both ends of the micro-column. This methodology reliably produces self-contained miniature constructs with long-projecting axonal tracts that may recapitulate features of brain neuroanatomy. Synaptic immunolabeling and genetically encoded calcium indicators suggest that micro-TENNs possess extensive synaptic distribution and intrinsic electrical activity. Consequently, micro-TENNs represent a promising strategy for targeted neurosurgical reconstruction of brain pathways and may also be applied as biofidelic models to study neurobiological phenomena in vitro.

This manuscript details the fabrication of micro-tissue engineered neural networks: three-dimensional micron-sized constructs comprised of long aligned axonal tracts spanning aggregated neuronal population(s) encased in a tubular hydrogel. These living scaffolds can serve as functional relays to reconstruct or modulate neural circuitry or as biofidelic test-beds mimicking gray-white matter neuroanatomy.

Functional recovery rarely occurs&#160;following injury or disease-induced degeneration within the central nervous system (CNS)&#160;due to the inhibitory ...

Controlling Electrospun Polymer Morphology for Tissue Engineering Demonstrated Using hepG2 Cell Line

Electrospinning affords researchers the opportunity to fabricate reproducible micro to nanoscale polymer fibers. The 3D fibrous architecture of electrospun polymers is regarded as a structural imitation of the extracellular matrix (ECM). Hence, electrospun fibers fabricated from biocompatible polymers have been widely investigated by tissue engineering researchers for their potential role as an artificial ECM for guiding tissue growth both in vitro and in vivo. All cells are acutely sensitive to their mechanical environment. This has been demonstrated by the discovery of multiple mechanotransduction pathways intrinsically linked to the cytoskeletal actin filaments. The cytoskeleton acts as a mechanical sensor that can direct the functionality and differentiation of the host cell depending on the stiffness and morphology of its substrate. Electrospun fibers can be tuned both in terms of fiber size and morphology to easily modulate the mechanical environment within a fibrous polymer scaffold. Here, methods for electrospinning polycaprolactone (PCL) for three distinct morphologies at two different fiber diameters are described. The morphological fiber categories consist of randomly oriented fibers, aligned fibers, and porous cryogenically spun fibers, with 1 &#181;m and 5 &#181;m diameters. The methods detailed within this study are proposed as a platform for investigating the effect of electrospun fiber architecture on tissue generation. Understanding these effects will allow researchers to optimize the mechanical properties of electrospun fibers and demonstrate the potential of this technology more thoroughly.

This method provides the means to test different polycaprolactone fiber morphologies and topographies for the purpose of tissue engineering. Small and large fibers are fabricated with random orientations, aligned orientations, and also porous cryogenically electrospun structures and used as platforms for cell culture.