Diese Arbeit wurde mit den Einrichtungen des Biomedical Engineering Department an der Florida International University durchgeführt.

1. Elektrospinning Collector Setup- <ol><li> Schneiden die Aluminiumfolie in einem rechteckigen Stück. </li><li> Falten Sie das rechteckige Stück in einen rechteckigen Streifen, und befestigen Sie es senkrecht zu einer flachen Metallplatte mit Klebeband (Abbildung 1). Hinweis: Die Größe der Fasermatte hängt von der Länge und Breite des Streifens. Somit kann die Bandabmessungen nach Bedarf eingestellt werden. </li></ol> 2. Polymere Herstellung der Lösung <ol><li> Mischen Glycerin und Dodecandisäure (DDA) in einem Molverhältnis von 1:1 in einem Becherglas bei 120 ° C für 100 h PGD-Polymer zu erhalten. </li><li> Auflösen Poly (ethylenoxid) (PEO) und Gelatine in 65% Ethanol mit einem Gewichtsverhältnis von 1.5:3:95.5 in einem 15 ml-Röhrchen, den Verschluss und die Mischung in einem Ofen bei 60 ° C für 1 h unter Rühren bis es eine homogene Lösung (Grundlösung). </li><li> Für Elektro, mischen Sie die PID-Polymer und die Grundlösung in 4.06 Gewichts-Verhältnis. Hinweis: PID-Konzentration hat eine big Wirkung auf Faserdurchmesser. 30% -50% Prozent PID akzeptabel Fasern mehr als 5 cm mit einer erhöhten Faserdurchmessern zu erzeugen. </li><li> In 0,1% Riboflavin der Polymerlösung und gut mischen. </li></ol> 3. Elektrospinning <ol><li> Feed der Polymerlösung in eine 5 ml Standardspritze mit einer 18 G abgestumpft Nadel aus Edelstahl. </li><li> Legen Sie die Spritze in eine Spritzenpumpe. </li><li> Befestigen des geerdeten Anschluß eines Hochspannungsleistungsquelle mit der Metallplatte und dem positiv geladenen führen zu der Nadel. </li><li> Den Abstand zwischen der Nadel und der Aluminiumfolienband 15 cm. </li><li> Zeigen die Spritzenpumpe in einem Winkel von etwa 15 ° mit der Horizontalen, um die Aggregation der Fasern an der Vorderseite des Streifens zu verhindern. </li><li> Schalten Sie die Spritzenpumpe und die Durchflussrate der Pumpe bis 0,6 ml / Std. </li><li> Schalten Sie die Hochspannungsquelle und stellen Sie die Betriebsspannung von 14,6 kV. </li></ol> 4.Faserverarbeitung <ol><li> Nach Abschluss der Sammlung ist, setzen die Fasermatte mit UV-Licht für 60 min für die Vernetzung. </li><li> Übertragen der Fasermatte aus der Aluminiumfolienstreifen auf eine 100 mm Petrischale, und setzen diese mit UV-Licht für weitere 20 min zur Sterilisation. </li><li> In einer biologischen Sicherheitsschrank, schneiden Sie die Fasermatte in runde Stücke der gleichen Größe mit einem Skalpell und legen Sie die Stücke in eine 24-Well-Platte. </li><li> Für Zellvorge Impfbehandlung tauchen Faserproben in 1 ml phosphatgepufferter Salzlösung (PBS) und bei 37 ° C über Nacht. </li><li> Am folgenden Tag, sorgfältig absaugen PBS, 1 ml Differenzierungsmedium (DMEM/F12, N2 und FGF2) (siehe Rezept in der Materialtabelle) in jede Vertiefung und Inkubation bei 37 ° C für 3 Stunden. </li><li> Saugen Differenzierungsmedium vorsichtig, fügen 0,2 ml Matrigel jedem Faserprobe und bei 37 ° C für 30 min. Hinweis: Laminin kann auch für Faserbeschichtung verwendet werden. 0,2 ml von 20 ug / ml Lamininan die Faser und Inkubieren bei Raumtemperatur für 3 Stunden. </li><li> Über Matrigel vorsichtig aus jedem Well. Spülen mit 2 ml Differenzierungsmedium einmal. Anmerkung: Die Faserproben sind bereit für die Zellkultur. </li></ol> 5. Zellaussaat auf Fibers <ol><li> 1 ml der Accutase auf der MES-Zellkulturschale und Inkubation für 10 min bei 37 ° C </li><li> Nach 10 min werden die MES-Zellen von der Kulturschale abgelöst. 4 ml Differenzierungsmedium mit der Platte. Sammeln Sie die schwimmenden MES-Zellen in ein 15-ml-Tube und Pipetten Zellen nach oben und unten, um Kolonien (ca. 15x) zu brechen. </li><li> Zentrifuge bei 400 × g für 5 min und resuspendieren Zellen in 4 ml Differenzierungsmedium. </li><li> Zählen Sie die Zellen mit einer Zählkammer. Transfer von 200 &amp;mgr; l der Zellsuspension in ein 15 ml-Röhrchen und verdünnte es 10x mit Differenzierungsmedium. Übertragen 15 &amp;mgr; l der verdünnten Zellsuspension in eine Kammer auf der Zählkammer mit einem Deckglas vorhanden. Zählendie Zellen in der Mitte Platz 1 mm und die vier Ecken Quadrate der Zählkammer unter dem Mikroskop. Hinweis: Zelle pro ml = die Durchschnittszahl pro Quadrat x Verdünnungsfaktor x 10 4 </li><li> Legen Sie ca. 5 x 10 4 MES-Zellen auf jede gut. Langsam fallen die Zellsuspension auf die Mitte der Faserproben, statt ein Abrutschen auf die Seite des Brunnens, die Lösung aus dem Ablassen der Fasermatte zu verhindern. </li><li> 1 ml Differenzierungsmedium in jede Vertiefung, und halten Sie die Platte in einem Brutschrank bei 37 ° C und 5% CO 2, um Zellen Befestigung, Wachstum und Differenzierung zu ermöglichen. </li><li> Saugen Sie das alte Medium aus jeder Vertiefung und ersetzen jeden zweiten Tag mit 1 ml frischem Differenzierungsmedium. </li></ol> 6. Zellviabilitätsmessungen <ol><li> Saugen Sie das alte Medium aus jedem Well. </li><li> Mischen 1/10 Volumen von Resazurin Fluoreszenz-Reagenz mit Kulturmedium und Zugabe von 1 ml in jede Vertiefung. </li><li> Incubaß bei 37 ° C und 5% CO 2 für 4 Stunden, vor Licht geschützt. </li><li> Nach 4 Stunden, dann 100 ul 3x des Reagenz aus jeder Vertiefung in eine 96-Well-Platte und dann die Proben sind bereit, auf einem Fluoreszenz-Spektralphotometer mit 560EX nm/590EM Filtereinstellungen gemessen werden. </li></ol> 7. Real Time PCR <ol><li> Nach 14 Tagen Kultur hinzufügen Lyse-Puffer zu den Proben zu isolieren, und die Gesamt-RNA aus den Zellen an der Faserproben. </li><li> Verwenden Sie 4 ul von Gesamt-RNA in cDNA in 20 ul Reaktions Skalen Synthese durch reverse Transkription. </li><li> Die PCR-Reaktionsgemisch in jedem optischen Röhre: 10 ul Master Mix (2x), 0,2 &amp;mgr; l Farbstoff, 8 &amp;mgr; l Nuklease-freiem Wasser, 1 &amp;mgr; l cDNA und 1 ul Primer (Primer in dieser Studie sind in Tabelle 1 aufgeführt). </li><li> Stellen Sie das PCR-Programm: ein. 95 ° C 2.20 min, 1 Zyklus b. 95 ° C 3 sec → 60 ° C 1 min, 40 Zyklus c. 95 ° C 15 s, 1 d-Zyklus. 60 ° C 1min, 1 Zyklus e. 95 ° C 15 sec, 1 Zyklus. Wählen Vergleichs C T-Methode, um die relative Genexpression zu bestimmen. </li><li> Nach der PCR beendet ist, analysieren die Echtzeit-PCR-Ergebnisse mit StepOne-Software und exportieren Sie die Ergebnisse in 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>

Keine Interessenskonflikte erklärt.

Die Grenzen der einfachen Kollektoren oder die Komplexität der Drehkollektoren, die derzeit zum Elektro erhöhen die Beschränkung der Erhalt der gewünschten Länge und Größe der Fasermatte für einige Anwendungen verwendet werden. Zusätzlich Übertragen Fasern aus dem Erdkollektor in die Kulturschale oder anderen Substraten 5 ist eine Herausforderung. In diesem Bericht wird ein neu gestalteten Sammler, durch das Hinzufügen einer Aluminiumfolienstreifen mit der geerdeten Kollektor hergestellt, konnte di...

Elektrospinnen ist eine der wirksamsten Methoden, um die Verarbeitung der Mikro-zur Nanometer-Größe Fasergerüste herzustellen. Das Grundprinzip der Elektro beinhaltet eine Taylor-Konus der Lösung, die an der Öffnung der Nadel durch Anlegen einer Hochspannung zwischen der Nadelspitze und einem geerdeten Kollektor gehalten wird. Wenn die elektrostatische Abstoßung in der Lösung überwindet die Oberflächenspannung, wird eine geladene Flüssigkeitsstrahl von der Nadelspitze ausgestoßen wird, durch die Luft mit Lösungsmittelverdampfung, und wird schließlich auf der geerdeten Kollektor abgeschieden. Die Spritzenpumpe stellt einen kontinuierlichen Fluss von Lösung aus der Spinndüse austretende und damit mehrere Kopien der elektrogesponnenen Fasern in kurzer Zeit hergestellt werden. Im Verlauf Verlassen der Spinndüse zu dem Kollektor zu gelangen, wird der geladene Strahl durchlaufen Dehnung und Schlag nach einer Anzahl von Parametern, die die Viskosität und die Oberflächenspannung der Polymerlösung enthalten, die elektrostac Kraft in der Lösung, und die Wechselwirkung des externen elektrischen Feldes, usw. 2. In der Elektrospinnverfahren dient ein Sammler als ein leitfähiges Substrat, wo die Mikro-bis Nanometer-Fasern abgelagert werden könnte. In dieser Studie wurde eine neue Art von Fasersammler wurde entwickelt, um Fasermatten mit der gewünschten Größe (Länge x Breite) zu erhalten. Traditionell wird die Aluminiumfolie als Kollektor verwendet, aber es ist schwierig, die Fasern von der flachen Oberfläche an ein anderes Substrat zu übertragen. Die Schwierigkeiten bei der Ernte eine intakte Fasermatte von einem traditionellen Sammler war vor allem aufgrund der Tatsache, dass die elektrogesponnenen Fasern legen stark an die Sammler-Oberfläche. Daher modifizierten wir die Sammler durch Falten ein Stück Aluminiumfolie zu einem rechteckigen Streifen und Befestigung senkrecht zu einer flachen Metallplatte. Die elektrogesponnenen Fasern in dem Bereich zwischen der Spitze des Streifens und der Metallplatte, die leicht auf einen anderen übertragen werden können substrat gestrecktE. Das Interesse an thermisch vernetzten elastomeren Polymeren wächst schnell, weil der Pionierarbeit von Robert Langer-Gruppe, die Poly (Glycerin Sebacat) (PGS), ein Polyester, der analog zu vulkanisierten Kautschuks in 2002 3. Ähnlich PGS eingeführt wurde, haben wir erfolgreich entwickelt Poly (Glycerin-Dodecanoat) (PID) durch thermische Kondensation von Glycerin und Dodecandisäure und demonstriert seine einzigartige Formgedächtniseigenschaft ein. Im Gegensatz zu steiferen synthetischen Materialien Poly (Hydroxybutyrat) oder Poly (L-lactid) (Young-Modul von 250 MPa und 660 MPa) aufweist PGD elastomere Eigenschaft wie Gummi, mit einem Young-Modul von 1,08 MPa, wenn die Temperatur über 37 ° ist C, die eine enge Übereinstimmung mit der in-situ peripheren Nerven (0,45 MPa) ist. Darüber hinaus ist die PID biologisch abbaubar und die Abbauzeit kann durch Variation des Verhältnisses von Glycerin und Dodecandisäure fein abgestimmt werden. Dodecandisäure ist ein Zwölf-Kohlenstoff-UnterPosition mit zwei endständigen Carboxygruppen, HOOC (CH 2) 10 COOH. Auch nummeriert Dicarbonsäuren wie Sebacinsäure und Dodecandisäure kann metabolisiert werden zu Acetyl-CoA und geben Sie den Tricarbonsäurezyklus (TCA) / (Zitronensäure-Zyklus). Das Stoffwechselprodukt von Dicarbonsäuren, Succinyl-CoA, ein gluconeogenetischen Vorläufer und Zwischen der TCA-Zyklus 4. So schlugen einige Studien, dass sie als alternativer Kraftstoff Substrat für die enterale und parenterale Ernährung, insbesondere bei der pathologischen Bedingungen verwendet werden. Außerdem weist eindeutige PID Formgedächtnis weil ihre Glasübergangstemperatur 31 ° C, so zeigt es verschiedene mechanische Eigenschaften bei Raumtemperatur und Körpertemperatur. In der Summe ist die PID biologisch abbaubare, biokompatible, Ausstellen einzigartigen elastischen Eigenschaften mit ähnlichen Nervengewebe mechanische Eigenschaften; Daher ist es ein geeignetes Material für Nervengewebe Technik. In diesem Protokoll wird die elektrolange Fasern überspannt eine große Ablagefläche wurden über die neu gestalteten Sammler aus PGD hergestellt. Die Fasergerüste können mit der Maus pluripotente Stammzellen Wachstum und die Differenzierung zu unterstützen.

<table border="0" cellpadding="0" cellspacing="0" width="729">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Glycerol</td>
			<td style="width:175px;">Sigma-Aldrich</td>
			<td style="width:119px;">G7757</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Dodecanedioic acid</td>
			<td style="width:175px;">Sigma-Aldrich</td>
			<td style="width:119px;">D1009</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Gelatin</td>
			<td style="width:175px;">Sigma-Aldrich</td>
			<td style="width:119px;">D1890</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Poly (ehtylene oxide) (PEO)</td>
			<td style="width:175px;">Sigma-Aldrich</td>
			<td style="width:119px;">182028</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Riboflavin</td>
			<td style="width:175px;">Sigma-Aldrich</td>
			<td style="width:119px;">132350250</td>
			<td style="width:167px;">0.10%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Mouse embryonic stem cells</td>
			<td style="width:175px;">GlobalStem</td>
			<td style="width:119px;">GSC-5002</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Matrigel</td>
			<td style="width:175px;">Becton Dickinson</td>
			<td style="width:119px;">356234</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">DMEM/F12</td>
			<td style="width:175px;">Thermo Scientific</td>
			<td style="width:119px;">SH30272.02</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">N2 supplement&#160;</td>
			<td style="width:175px;">Invitrogen</td>
			<td style="width:119px;">17502048</td>
			<td style="width:167px;">1%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">FGF2</td>
			<td style="width:175px;">Stemgent</td>
			<td style="width:119px;">03-0002</td>
			<td style="width:167px;">10ng/ml</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Accutase</td>
			<td style="width:175px;">Invitrogen</td>
			<td style="width:119px;">A11105-01</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Phosphate buffered saline (PBS)</td>
			<td style="width:175px;">Invitrogen</td>
			<td style="width:119px;">10010-031&#160;</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Resazurin fluorescence dye&#160;</td>
			<td style="width:175px;">Sigma-Aldrich</td>
			<td style="width:119px;">62758-13-8&#160;</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">SV Total RNA Isolation System</td>
			<td style="width:175px;">Promega</td>
			<td style="width:119px;">Z3100</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">GoScript Reverse Transcription System</td>
			<td style="width:175px;">Promega</td>
			<td style="width:119px;">A5000</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">GoTaq&#129; qPCR Master Mix</td>
			<td style="width:175px;">Promega</td>
			<td style="width:119px;">A6001</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Syringe pump&#160;</td>
			<td style="width:175px;">Fisher scientific</td>
			<td style="width:119px;">14-831-200</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:268px;">High voltage power source&#160;</td>
			<td style="width:175px;">Spellman High Voltage Electronics Corporation</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">SL30</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">UV light</td>
			<td style="width:175px;">Philips</td>
			<td style="width:119px;">308643</td>
			<td style="width:167px;">15W/G15T8</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Synergy HT Multi-Mode Microplate Reader</td>
			<td style="width:175px;">BioTek</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Perkin Elmer GeneAmp PCR System 9600</td>
			<td style="width:175px;">Perkin Elmer</td>
			<td style="width:119px;">8488</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">StepOne Real-time PCR System</td>
			<td style="width:175px;">Applied Biosystems</td>
			<td style="width:119px;">4376357</td>
			<td style="width:167px;"></td>
		</tr>
	</tbody>
</table>

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

Für Tissue-Engineering-Anwendungen ist die Herstellung von biologisch abbaubaren und biokompatiblen Stützgerüste der wünschenswerteste aber schwierige Aufgabe. Von den verschiedenen Herstellungsverfahren, ist die Elektro attraktiv wegen ihrer Einfachheit und Vielseitigkeit. Zusätzlich elektrogesponnene Nano imitieren die Größe der natürlichen extrazellulären Matrix gewährleistet zusätzliche Unterstützung für das Überleben der Zelle und Wachstum. Diese Studie zeigte, die Lebensfähigkeit der Herstellung von Langfasern sich über eine größere Ablagefläche für eine neuartige biologisch abbaubare und biokompatible Polymer namens Poly (Glycerin-Dodecanoat) (PGD) 1 unter Verwendung einer neu entwickelten Kollektor für Elektro. PID zeigt einzigartige elastischen Eigenschaften mit ähnlichen mechanischen Eigenschaften von Nervengewebe, somit geeignet für neuronale Gewebe-Engineering-Anwendungen ist es. Die Synthese und Herstellung Set-up für die Herstellung von Fasergerüstmaterial war einfach, sehr gut reproduzierbar und kostengünstig. BiokompatibilitätTests könnten Zellen aus embryonalen Stammzellen der Maus abgeleitet zu haften und wachsen an den elektro PGD Fasern. Zusammenfassend dieses Protokoll ein vielseitiger Herstellungsverfahren für die Herstellung von PGD elektrogesponnenen Fasern um das Wachstum von embryonalen Maus-Stammzellen abgeleitete neuronale Linie Zellen unterstützen.

Die Hauptkomponenten der Elektro sind in Abbildung 1 dargestellt. Ein großer Größe Fasermatte wurde in der Regel durch die senkrecht befestigt Aluminiumfolienstreifen und einer flachen Metallplatte erhalten. Abbildung 2 zeigt die Kollektordesign und die Elektrofasermatte. Die Breite und Länge kann für unterschiedliche Anwendungen angepasst werden. Die Länge der Faser mit PID-Grundlösung und Polymermischung hergestellt ist, bis zu 10 cm. Die Morphologie der elektrogesponnenen Fase...

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

Synthese und Herstellung von elektro langen Fasern sich über eine größere Ablagefläche über einen neu gestalteten Sammler aus einem neuartigen biologisch abbaubaren Polymer namens Poly (Glycerin-Dodecanoat) (PGD) wurde berichtet. Die Fasern waren in der Lage, das Wachstum von pluripotenten Zellen aus Maus-Stammzellen zu unterstützen.

Elektro Faser-Gerüste von Poly (Glycerin-dodecandioat) für Ingenieurnervengewebe aus embryonalen Stammzellen der Maus

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

electrospun-fibrous-scaffolds-polyglycerol-dodecanedioate-for

Research

JoVE Journal

Bioengineering

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

10.8K Aufrufe.  Florida International University.  Synthese und Herstellung von elektro langen Fasern sich über eine größere Ablagefläche über einen neu gestalteten Sammler aus einem neuartigen biologisch abbaubaren Polymer namens Poly (Glycerin-Dodecanoat) (PGD) wurde berichtet. Die Fasern waren in der Lage, das Wachstum von pluripotenten Zellen aus Maus-Stammzellen zu unterstützen. 

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

Elastomeric PGS Scaffolds in Arterial Tissue Engineering

Cardiovascular disease is one of the leading cause of mortality in the US and especially, coronary artery disease increases with an aging population and increasing obesity1. Currently, bypass surgery using autologous vessels, allografts, and synthetic grafts are known as a commonly used for arterial substitutes2. However, these grafts have limited applications when an inner diameter of arteries is less than 6 mm due to low availability, thrombotic complications, compliance mismatch, and late intimal hyperplasia3,4. To overcome these limitations, tissue engineering has been successfully applied as a promising alternative to develop small-diameter arterial constructs that are nonthrombogenic, robust, and compliant. Several previous studies have developed small-diameter arterial constructs with tri-lamellar structure, excellent mechanical properties and burst pressure comparable to native arteries5,6. While high tensile strength and burst pressure by increasing collagen production from a rigid material or cell sheet scaffold, these constructs still had low elastin production and compliance, which is a major problem to cause graft failure after implantation. Considering these issues, we hypothesized that an elastometric biomaterial combined with mechanical conditioning would provide elasticity and conduct mechanical signals more efficiently to vascular cells, which increase extracellular matrix production and support cellular orientation.
The objective of this report is to introduce a fabrication technique of porous tubular scaffolds and a dynamic mechanical conditioning for applying them to arterial tissue engineering. We used a biodegradable elastomer, poly (glycerol sebacate) (PGS)7 for fabricating porous tubular scaffolds from the salt fusion method. Adult primary baboon smooth muscle cells (SMCs) were seeded on the lumen of scaffolds, which cultured in our designed pulsatile flow bioreactor for 3 weeks. PGS scaffolds had consistent thickness and randomly distributed macro- and micro-pores. Mechanical conditioning from pulsatile flow bioreactor supported SMC orientation and enhanced ECM production in scaffolds. These results suggest that elastomeric scaffolds and mechanical conditioning of bioreactor culture may be a promising method for arterial tissue engineering.

Elastomeric PGS scaffolds with vascular smooth muscle cells cultured in a pulsatile flow bioreactor may lead to promising small-diameter arterial constructs with native ECM production in a relatively short culture period.

Elastomer-PGS Scaffolds in Arterial Tissue Engineering

Cardiovascular disease is one of the leading cause of mortality in the US and especially, coronary artery disease increases with an aging population and ...

Forschung

Biotechnik

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.

Erstellung von 3D-Fibrin-Gerüste für Stem Cell Culture Anwendungen

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 ...

Postproduction Processing of Electrospun Fibres for Tissue Engineering

Electrospinning is a commonly used and versatile method to produce scaffolds (often biodegradable) for 3D tissue engineering.1, 2, 3 Many tissues in vivo undergo biaxial distension to varying extents such as skin, bladder, pelvic floor and even the hard palate as children grow. In producing scaffolds for these purposes there is a need to develop scaffolds of appropriate biomechanical properties (whether achieved without or with cells) and which are sterile for clinical use. The focus of this paper is not how to establish basic electrospinning parameters (as there is extensive literature on electrospinning) but on how to modify spun scaffolds post production to make them fit for tissue engineering purposes - here thickness, mechanical properties and sterilisation (required for clinical use) are considered and we also describe how cells can be cultured on scaffolds and subjected to biaxial strain to condition them for specific applications.
Electrospinning tends to produce thin sheets; as the electrospinning collector becomes coated with insulating fibres it becomes a poor conductor such that fibres no longer deposit on it. Hence we describe approaches to produce thicker structures by heat or vapour annealing increasing the strength of scaffolds but not necessarily the elasticity. Sequential spinning of scaffolds of different polymers to achieve complex scaffolds is also described. Sterilisation methodologies can adversely affect strength and elasticity of scaffolds. We compare three methods for their effects on the biomechanical properties on electrospun scaffolds of poly lactic-co-glycolic acid (PLGA).
Imaging of cells on scaffolds and assessment of production of extracellular matrix (ECM) proteins by cells on scaffolds is described. Culturing cells on scaffolds in vitro can improve scaffold strength and elasticity but the tissue engineering literature shows that cells often fail to produce appropriate ECM when cultured under static conditions. There are few commercial systems available that allow one to culture cells on scaffolds under dynamic conditioning regimes - one example is the Bose Electroforce 3100 which can be used to exert a conditioning programme on cells in scaffolds held using mechanical grips within a media filled chamber.4 An approach to a budget cell culture bioreactor for controlled distortion in 2 dimensions is described. We show that cells can be induced to produce elastin under these conditions. Finally assessment of the biomechanical properties of processed scaffolds cultured with or without cells is described.

Electrospun scaffolds can be processed post production for tissue engineering applications. Here we describe methods for spinning complex scaffolds (by consecutive spinning), for making thicker scaffolds (by multi-layering using heat or vapour annealing), for achieving sterility (aseptic production or sterilisation post production) and for achieving appropriate biomechanical properties.

Postproduction Verarbeitung von Elektrogesponnene Fasern für Tissue Engineering

Electrospinning is a commonly used and versatile method to produce  scaffolds (often biodegradable) for 3D tissue engineering.1, 2, 3 Many tissues in vivo ...

Engineering Skeletal Muscle Tissues from Murine Myoblast Progenitor Cells and Application of Electrical Stimulation

Engineered muscle tissues can be used for several different purposes, which include the production of tissues for use as a disease model in vitro, e.g. to study pressure ulcers, for regenerative medicine and as a meat alternative 1. The first reported 3D muscle constructs have been made many years ago and pioneers in the field are Vandenburgh and colleagues 2,3. Advances made in muscle tissue engineering are not only the result from the vast gain in knowledge of biochemical factors, stem cells and progenitor cells, but are in particular based on insights gained by researchers that physical factors play essential roles in the control of cell behavior and tissue development. State-of-the-art engineered muscle constructs currently consist of cell-populated hydrogel constructs. In our lab these generally consist of murine myoblast progenitor cells, isolated from murine hind limb muscles or a murine myoblast cell line C2C12, mixed with a mixture of collagen/Matrigel and plated between two anchoring points, mimicking the muscle ligaments. Other cells may be considered as well, e.g. alternative cell lines such as L6 rat myoblasts 4, neonatal muscle derived progenitor cells 5, cells derived from adult muscle tissues from other species such as human 6 or even induced pluripotent stem cells (iPS cells) 7. Cell contractility causes alignment of the cells along the long axis of the construct 8,9 and differentiation of the muscle progenitor cells after approximately one week of culture. Moreover, the application of electrical stimulation can enhance the process of differentiation to some extent 8. Because of its limited size (8 x 2 x 0.5 mm) the complete tissue can be analyzed using confocal microscopy to monitor e.g. viability, differentiation and cell alignment. Depending on the specific application the requirements for the engineered muscle tissue will vary; e.g. use for regenerative medicine requires the up scaling of tissue size and vascularization, while to serve as a meat alternative translation to other species is necessary.

Engineered muscle tissue has great potential in regenerative medicine, as disease model and also as an alternative source for meat. Here we describe the engineering of a muscle construct, in this case from mouse myoblast progenitor cells, and the stimulation by electrical pulses.

Engineering Skeletal Muscle Gewebe von Murine Myoblast Progenitor Cells und Anwendung von Elektrostimulation

Engineered muscle tissues can be used for several different purposes, which include the production of tissues for use as a disease model in vitro, e.g. to ...

Development, Expansion, and In vivo Monitoring of Human NK Cells from Human Embryonic Stem Cells (hESCs) and Induced Pluripotent Stem Cells (iPSCs)

We present a method for deriving natural killer (NK) cells from undifferentiated hESCs and iPSCs using a feeder-free approach. This method gives rise to high levels of NK cells after 4 weeks culture and can undergo further 2-log expansion with artificial antigen presenting cells. hESC- and iPSC-derived NK cells developed in this system have a mature phenotype and function. The production of large numbers of genetically modifiable NK cells is applicable for both basic mechanistic as well as anti-tumor studies. Expression of firefly luciferase in hESC-derived NK cells allows a non-invasive approach to follow NK cell engraftment, distribution, and function. We also describe a dual-imaging scheme that allows separate monitoring of two different cell populations to more distinctly characterize their interactions in vivo. This method of derivation, expansion, and dual in vivo imaging provides a reliable approach for producing NK cells and their evaluation which is necessary to improve current NK cell adoptive therapies.

Development, Expansion, and In vivo Monitoring of Human NK Cells from Human Embryonic Stem Cells hESCs and Induced Pluripotent Stem Cells iPSCs

This protocol describes the development, expansion, and in vivo imaging of NK cells derived from hESCs and iPSCs.

Entwicklung, Erweiterung und<em&gt; In vivo</em&gt; Monitoring von humanen NK Zellen aus humanen embryonalen Stammzellen (hES-Zellen) und und induzierten pluripotenten Stammzellen (iPS-Zellen)

We present a method for deriving natural killer (NK) cells from undifferentiated hESCs and iPSCs using a feeder-free approach. This method gives rise to ...

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.

Elektro Growth Factor Releasing Mikrosphären in Fasergerüste

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

Optimizing Attachment of Human Mesenchymal Stem Cells on Poly(&#949;-caprolactone) Electrospun Yarns

Research into biomaterials and tissue engineering often includes cell-based in vitro investigations, which require initial knowledge of the starting cell number. While researchers commonly reference their seeding density this does not necessarily indicate the actual number of cells that have adhered to the material in question. This is particularly the case for materials, or scaffolds, that do not cover the base of standard cell culture well plates. This study investigates the initial attachment of human mesenchymal stem cells seeded at a known number onto electrospun poly(&#949;-caprolactone) yarn after 4 hr in culture. Electrospun yarns were held within several different set-ups, including bioreactor vessels rotating at 9 rpm, cell culture inserts positioned in low binding well plates and polytetrafluoroethylene (PTFE) troughs placed within petri dishes. The latter two were subjected to either static conditions or positioned on a shaker plate (30 rpm). After 4 hr incubation at 37&#160;oC, 5% CO2, the location of seeded cells was determined by cell DNA assay. Scaffolds were removed from their containers and placed in lysis buffer. The media fraction was similarly removed and centrifuged &#8211; the supernatant discarded and pellet broken up with lysis buffer. Lysis buffer was added to each receptacle, or well, and scraped to free any cells that may be present. The cell DNA assay determined the percentage of cells present within the scaffold, media and well fractions. Cell attachment was low for all experimental set-ups, with greatest attachment (30%) for yarns held within cell culture inserts and subjected to shaking motion. This study raises awareness to the actual number of cells attaching to scaffolds irrespective of the stated cell seeding density.

Optimizing Attachment of Human Mesenchymal Stem Cells on Poly(&amp;#949;-caprolactone) Electrospun Yarns

This article describes a range of set-ups for seeding human mesenchymal stem cells onto materials, in this case electrospun yarns, that do not cover the base of standard culture well plates in order to maximize and quantify the number of cells that initially attach compared to the known seeding density.

Optimierung der Befestigung der humanen mesenchymalen Stammzellen auf Poly (ε-caprolacton) Elektrogesponnene Garne

Research into biomaterials and tissue engineering often includes cell-based in vitro investigations, which require initial knowledge of the starting cell ...

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.

Elektronanofasergerüste mit Abstufungen in Fiber-Organisation

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

Generation of ESC-derived Mouse Airway Epithelial Cells Using Decellularized Lung Scaffolds

Lung lineage differentiation requires integration of complex environmental cues that include growth factor signaling, cell-cell interactions and cell-matrix interactions. Due to this complexity, recapitulation of lung development in vitro to promote differentiation of stem cells to lung epithelial cells has been challenging. In this protocol, decellularized lung scaffolds are used to mimic the 3-dimensional environment of the lung and generate stem cell-derived airway epithelial cells. Mouse embryonic stem cell are first differentiated to the endoderm lineage using an embryoid body (EB) culture method with activin A. Endoderm cells are then seeded onto decellularized scaffolds and cultured at air-liquid interface for up to 21 days. This technique promotes differentiation of seeded cells to functional airway epithelial cells (ciliated cells, club cells, and basal cells) without additional growth factor supplementation. This culture setup is defined, serum-free, inexpensive, and reproducible. Although there is limited contamination from non-lung endoderm lineages in culture, this protocol only generates airway epithelial populations and does not give rise to alveolar epithelial cells. Airway epithelia generated with this protocol can be used to study cell-matrix interactions during lung organogenesis and for disease modeling or drug-discovery platforms of airway-related pathologies such as cystic fibrosis.

This protocol efficiently directs mouse embryonic stem cell-derived definitive endoderm to mature airway epithelial cells. This differentiation technique uses 3-dimensional decellularized lung scaffolds to direct lung lineage specification, in a defined, serum-free culture setting.

Die Erzeugung von ESC-derived Maus Airway epithelialen Zellen unter Verwendung von Dezellularisierte Lung Scaffolds

Lung lineage differentiation requires integration of complex environmental cues that include growth factor signaling, cell-cell interactions and ...

Two Methods for Decellularization of Plant Tissues for Tissue Engineering Applications

The autologous, synthetic, and animal-derived grafts currently used as scaffolds for tissue replacement have limitations due to low availability, poor biocompatibility, and cost. Plant tissues have favorable characteristics that make them uniquely suited for use as scaffolds, such as high surface area, excellent water transport and retention, interconnected porosity, preexisting vascular networks, and a wide range of mechanical properties. Two successful methods of plant decellularization for tissue engineering applications are described here. The first method is based on detergent baths to remove cellular matter, which is similar to previously established methods used to clear mammalian tissues. The second is a detergent-free method adapted from a protocol that isolates leaf vasculature and involves the use of a heated bleach and salt bath to clear the leaves and stems. Both methods yield scaffolds with comparable mechanical properties and low cellular metabolic impact, thus allowing the user to select the protocol which better suits their intended application.

Here we present, and contrast two protocols used to decellularize plant tissues: a detergent-based approach and a detergent-free approach. Both methods leave behind the extracellular matrix of the plant tissues used, which can then be utilized as scaffolds for tissue engineering applications.

Zwei Methoden zur Decellularization von Pflanzengewebe für Tissue-Engineering-Anwendungen

The autologous, synthetic, and animal-derived grafts currently used as scaffolds for tissue replacement have limitations due to low availability, poor ...