This work was partially funded through the Richard Barber Foundation and a Thomas Rumble Fellowship (TJW).

1. agua / aceite / agua Doble Emulsión Microsphere Producción <ol><li> En primer lugar preparar 2% y 0,5% w / v de las soluciones de alcohol polivinílico (PVA) en agua desionizada. Revuelva las soluciones a 50 ° C hasta que se aclare, esto puede tardar varias horas. Preparar una solución de 2% v / v de alcohol isopropílico en agua desionizada. </li><li> Preparar una solución acuosa de proteína hidrófila deseada. La siguiente tabla proporciona ejemplos de formulaciones. </li></ol><img alt="Tabla 1" src="/files/ftp_upload/51517/51517table1highres.jpg" /> Tabla 1:. Ejemplo Proteína soluciones Las siguientes soluciones de proteínas se han encapsulado con éxito y electrospun usando este protocolo. Otras soluciones de proteínas hidrófilas se pueden usar según sea necesario. <ol start="3"><li> Coloque 40 ml de la solución de PVA al 0,5% en un tubo de centrífuga de 50 ml y reservar. </li><li> En un tubo de centrífuga de 15 ml disolver 300 mg de 65:35poli (ácido láctico-co-glicólico) (PLGA) en 3 ml de diclorometano. Un mezclador de vórtice puede ser utilizado para acelerar la disolución de PLGA. </li><li> Combinar 200 l de solución de proteína y 4 l de solución de PVA al 2%. Verter la mezcla de proteína en la solución de PLGA (paso 1.4). Las soluciones se mantendrán básicamente individualista. </li><li> Se coloca el tubo en un vaso de agua helada. Uso de un aparato de ultrasonidos varita a ~ 10 vatios (RMS), agitar la solución durante unos pocos segundos (5-10) hasta que se crea una emulsión blanca cremosa uniforme. </li><li> Se vierte la emulsión en el tubo de 50 ml que contiene 0,5% de PVA (paso 1.3). Mezcle la solución a alta velocidad en un vórtex durante ~ 20 seg. La solución desarrollará un aspecto turbio. </li><li> Se transfiere la emulsión a un vaso de 200 ml y colocar en una placa de agitación a 350 rpm durante 2 min. Añadir 50 ml de 2% de alcohol isopropílico al vaso de precipitados en la placa de agitación. Deje que la mezcla se continúa agitando durante un mínimo de 1 hora para permitir que el DCM se evapore y el PLGA a endurecerse. </li><li> Transferencia tél microesfera solución en tubos de centrífuga. </li><li> Se centrifuga a 425 g durante 3 min. Las microesferas se concentren en la parte inferior del tubo y aparecerá blanco. Retire con cuidado el sobrenadante del tubo, por encima de las microesferas, y almacenar en una botella de 500 ml. </li><li> Enjuague las microesferas con agua desionizada, llenando el tubo de tres cuartos llena y agitarlo para redistribuir las microesferas en el líquido. </li><li> Repita los pasos 1.10 y 1.11 cuatro veces. </li><li> Tras el enjuague final, separar el sobrenadante de nuevo y colocar en la botella de 500 ml con las otras muestras. Congelar las microesferas recogidos en el tubo de centrífuga, a continuación, se liofiliza durante al menos 24 h. </li><li> Visualizar las microesferas con un microscopio de luz o con un microscopio electrónico de barrido. Las microesferas no mayores de 60 micras son para electrospinning efectiva. Si las microesferas son demasiado grandes, sonicación o de vórtice tiempos más largos pueden ser requeridos en el paso 1.6 o 1.7. </li> &lt;li&gt; Guarde las microesferas secas en un -20 ° C congelador. </li><li> Opcional: Utilice un ensayo de proteínas, por las instrucciones del fabricante, para medir la cantidad de proteína en la botella de 500 ml desde el paso 30 1.10. Esto se utiliza para calcular el porcentaje de proteína encapsulada en las microesferas, restando la cantidad en la solución de lo que fue utilizado en el proceso de producción. </li></ol> NOTA: Para visualizar la ubicación de proteína en la microesfera añadir Rodamina 2 mg / ml a la solución de PLGA 31 y encapsular una proteína conjugada con FITC Figura 1 muestra un ejemplo.. 2. electrospinning con microesferas <ol><li> Antes de preparar la solución de electrospinning, crear un 0,5% w / v solución de fotoiniciador, en agua desionizada mediante la disolución a 37 ° C. Este proceso puede tardar varias horas. </li><li> Crear un 2% w / v ácido hialurónico metacrilatado (MEHA) (ver Burdick et al. Para la síntesis) 29, 3%w / v 900 kD poli (óxido de etileno) (PEO) y 0,05% w / v solución de fotoiniciador en agua desionizada. <ol><li> Calcular la cantidad correcta de MEHA y PEO para el volumen deseado. Por ejemplo, 10 ml de electrospinning solución requiere 200 mg de MEHA y 300 mg de PEO. </li><li> Disolver el PEO en agua desionizada a 90% del volumen final deseado (9 ml para este ejemplo). Esto puede tomar varias horas, una placa de agitación caliente o baño de agua a 37 ° C pueden ser utilizados para acelerar el proceso. </li><li> A continuación añadimos la MEHA y utilizar un mezclador de vórtice para agitar la solución hasta que se aclare. Esto sólo tomará unos minutos. </li><li> Finalmente añadir la solución de fotoiniciador 0,5% para llenar el volumen restante 10% (1 ml para este ejemplo). </li></ol></li><li> Añadir las microesferas a la concentración deseada de hasta 400 mg / ml. Mezclar la solución en un mezclador de vórtice hasta que las microesferas se distribuyeron uniformemente en la solución. </li><li> Transferir la solución a una jeringa y fijar un 6 pulgadas bl calibre 18aguja punta unt. </li><li> Coloque la jeringa en una bomba de jeringa y la puso para dispensar a 1,2 ml / hr. </li><li> Pegue una capa de papel de aluminio en el plato de la colecta o mandril. Esto permite una fácil limpieza y almacenamiento del andamio terminado. Un mandril giratorio se utiliza para crear fibras alineadas. Una placa plana o mandril estacionario se traducirá en fibras dispuestas al azar. </li><li> Conectar el cable de tierra de una fuente de alimentación de alto voltaje para el aparato de recogida. Conecte el cable positivo a la aguja. </li><li> Ajuste la superficie de la bomba de jeringa y la recolección de modo que haya 15 cm entre la punta de la aguja y la superficie de recogida. </li><li> Iniciar el bombeo de polímero, cuando la solución es visible en el extremo de la jeringa, encender la fuente de tensión y ajustar la tensión de 24 kV PRECAUCIÓN:. Una vez que la tensión se enciende no toque ninguna parte metálica del sistema. Carga también puede saltar distancias cortas a partir de piezas electrificadas a la piel. </li><li> Ejecute la solución hasta que dse consigue espesor andamio esired. Cuando completa apagar la fuente de tensión y la bomba de jeringa. </li><li> Retire el papel aluminio con el andamio colocado. Completadas andamios que contienen proteínas se almacenan en un congelador de -20 ° C. </li></ol> 3. Proteína Testing bioactividad <ol><li> Preparar medios de cultivo celular. Añadir 10% v / v de suero fetal bovino, 1% v / v L-glutamina, y 1% v / v penicilina-estreptomicina al medio de Eagle modificado de Dulbecco. </li><li> Seleccione cubreobjetos de vidrio que cabe totalmente en un plato bien. </li><li> Utilice 3 (trimetoxisilil) propil metacrilato para tratar los cubreobjetos tal como se describe por el fabricante. Metacrilación mejora la adherencia andamio para los cubreobjetos. </li><li> Adjuntar cubreobjetos metacrilados a la zona de recogida de la electrospinner con cinta adhesiva de doble cara antes de electrospinning. Spinning sobre los cubreobjetos facilita la manipulación y visualización. </li><li> Electrospin al espesor deseado como se describe anteriormente. </li><li> Aespués de electrospinning retire con cuidado cubreobjetos de mandril. Coloque el andamio cubreobjetos recubiertos en una cámara de nitrógeno clara y asegúrese de que todo el oxígeno se purga. </li><li> Coloque la cámara y bajo un andamio 10 mW / cm 2 365 nm de luz durante 15 min. Después de la reticulación lugar en placa de tamaño apropiado. Asegúrese de que el lado del andamio esté hacia arriba. </li><li> Coloque los andamios bajo una lámpara germicida durante 30 min para esterilizar. Si la fibronectina u otra proteína deseada se utiliza como un recubrimiento para mejorar la adhesión celular. Siga las instrucciones del fabricante de andamios abrigo. </li><li> Harvest ganglios de raíz dorsal (DRG), como se describe anteriormente por Hollenbeck 32. Se necesitará un DRG para cada andamio cubierto cubreobjetos probado. </li><li> Coloque 100-200 l de los medios de comunicación en cada andamio en la placa también. Con cuidado, coloque uno en cada DRG andamio en la gota de los medios de comunicación. Para andamios de espesor pueden ser necesarios más medios de comunicación; DRG necesita estar totalmente sumergido y no Floating. </li><li> Incubar el andamio y DRG a 37 ° C durante 4 horas para permitir que la célula se adhiera a la andamio. </li><li> Rellene los medios de comunicación para el nivel apropiado para el bien y colocar de nuevo en la incubadora. Continuar la incubación durante 4-6 días. </li><li> Tras el período de incubación retire con cuidado los medios de cada pocillo y lavar suavemente una vez con PBS. Fijar las células durante 30 min utilizando 4% w / v de paraformaldehído. </li><li> Las células de la mancha utilizando una mancha de anticuerpos para neurofilamentos. Esto permitirá la visualización del crecimiento de neuritas para la cuantificación. DAPI también se puede utilizar para ver núcleos de las células. Un ejemplo de protocolo de tinción fue descrito por Sundararaghavan y sus colegas 14. </li><li> Visualice las células utilizando un microscopio de fluorescencia. <ol><li> Colocar la placa de bien en la platina del microscopio. </li><li> Busque la masa celular utilizando los filtros de excitación y ajustes para DAPI. </li><li> Una vez que la célula es cambiar el filtro para FITC para visualizar las neuritas extendidas. Ucantar la función de puntada en el microscopio recoger y combinar tantas imágenes como sea necesario para ver toda la estructura. Repita el procedimiento para DAPI, FITC y campo claro. </li></ol></li></ol>

<ol>
	<li>Wrobel, M. R., Sundararaghavan, H. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Directed+migration+in+neural+tissue+engineering.">Directed migration in neural tissue engineering.</a> Tissue Eng Part B Rev. , (2013).</li><li>Schmidt, C. E., Leach, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+tissue+engineering:+strategies+for+repair+and+regeneration.">Neural tissue engineering: strategies for repair and regeneration.</a> Annual Review of Biomedical Engineering. 5, 293-347 (2003).</li><li>Madduri, S., di Summa, P., Papaloizos, M., Kalbermatten, D., Gander, B. <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+controlled+co-delivery+of+synergistic+neurotrophic+factors+on+early+nerve+regeneration+in+rats.">Effect of controlled co-delivery of synergistic neurotrophic factors on early nerve regeneration in rats.</a> Biomaterials. 31, 8402-8409 (2010).</li><li>Madduri, S., Gander, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+factor+delivery+systems+and+repair+strategies+for+damaged+peripheral+nerves.">Growth factor delivery systems and repair strategies for damaged peripheral nerves.</a> J Control Release. 161, 274-282 (2012).</li><li>Madigan, N. N., McMahon, S., O'Brien, T., Yaszemski, M. J., Windebank, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Current+tissue+engineering+and+novel+therapeutic+approaches+to+axonal+regeneration+following+spinal+cord+injury+using+polymer+scaffolds.">Current tissue engineering and novel therapeutic approaches to axonal regeneration following spinal cord injury using polymer scaffolds.</a> Respir Physiol Neurobiol. 169, 183-199 (2009).</li><li>Sundararaghavan, H. G., Monteiro, G. A., Firestein, B. L., Shreiber, D. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurite+growth+in+3D+collagen+gels+with+gradients+of+mechanical+properties.">Neurite growth in 3D collagen gels with gradients of mechanical properties.</a> Biotechnol. Bioeng. 102, 632-643 (2009).</li><li>Hudson, T. W., Evans, G. R., Schmidt, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+strategies+for+peripheral+nerve+repair.">Engineering strategies for peripheral nerve repair.</a> Clin Plast Surg. 26, 617-628 (1999).</li><li>Kokai, L. E., Bourbeau, D., Weber, D., McAtee, J., Marra, K. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sustained+growth+factor+delivery+promotes+axonal+regeneration+in+long+gap+peripheral+nerve+repair.">Sustained growth factor delivery promotes axonal regeneration in long gap peripheral nerve repair.</a> Tissue Eng Part A. 17, 1263-1275 (2011).</li><li>Bronzino, J. D., Peterson, D. 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> The Biomedical Engineering Handbook, Third Edition - 3 Volume Set: Tissue Engineering and Artificial Organs. , (2006).</li><li>Bell, J. H. A., Haycock, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Next+generation+nerve+guides:+materials,+fabrication,+growth+factors,+and+cell+delivery.">Next generation nerve guides: materials, fabrication, growth factors, and cell delivery.</a> Tissue Eng Part B Rev. 18, 116-128 (2012).</li><li>Ruiter, G. C. W., Malessy, M. J. A., Yaszemski, M. J., Windebank, A. J., Spinner, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Designing+ideal+conduits+for+peripheral+nerve+repair.">Designing ideal conduits for peripheral nerve repair.</a> Neurosurgical focus. 26, (2009).</li><li>Olakowska, E., Woszczycka-Korczy&#324;ska, I., J&#281;drzejowska-Szypu&#322;ka, H., Lewin-Kowalik, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+nanotubes+and+nanofibres+in+nerve+repair.+A+review.">Application of nanotubes and nanofibres in nerve repair. A review.</a> Folia Neuropathol. 48, 231-237 (2010).</li><li>Gunn, J., Zhang, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polyblend+nanofibers+for+biomedical+applications:+perspectives+and+challenges.">Polyblend nanofibers for biomedical applications: perspectives and challenges.</a> Trends Biotechnol. 28, 189-197 (2010).</li><li>Sundararaghavan, H. G., Masand, S. N., Shreiber, D. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+generation+of+haptotactic+gradients+through+3D+collagen+gels+for+enhanced+neurite+growth.">Microfluidic generation of haptotactic gradients through 3D collagen gels for enhanced neurite growth.</a> Journal of Neurotrauma. 28, 2377-2387 (2011).</li><li>Sundararaghavan, H. G., Metter, R. B., Burdick, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+fibrous+scaffolds+with+multiscale+and+photopatterned+porosity.">Electrospun fibrous scaffolds with multiscale and photopatterned porosity.</a> Macromol Biosci. 10, 265-270 (2010).</li><li>Edalat, F., Sheu, I., Manoucheri, S., Khademhosseini, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Material+strategies+for+creating+artificial+cell-instructive+niches.">Material strategies for creating artificial cell-instructive niches.</a> Current Opinion in Biotechnology. 23, 820-825 (2012).</li><li>Annabi, N., 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=Synthesis+of+highly+porous+crosslinked+elastin+hydrogels+and+their+interaction+with+fibroblasts+in+vitro.">Synthesis of highly porous crosslinked elastin hydrogels and their interaction with fibroblasts in vitro.</a> Biomaterials. 30, 4550-4557 (2009).</li><li>Casta&#241;o, O., Eltohamy, M., Kim, H. -. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospinning+technology+in+tissue+regeneration.">Electrospinning technology in tissue regeneration.</a> Methods Mol. Biol. 811, 127-140 (2012).</li><li>Chew, S. Y., Wen, J., Yim, E. K. F., Leong, K. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sustained+release+of+proteins+from+electrospun+biodegradable+fibers.">Sustained release of proteins from electrospun biodegradable fibers.</a> Biomacromolecules. 6, 2017-2024 (2005).</li><li>Han, D., Gouma, P. -. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+bioscaffolds+that+mimic+the+topology+of+extracellular+matrix.">Electrospun bioscaffolds that mimic the topology of extracellular matrix.</a> Nanomedicine. 2, 37-41 (2006).</li><li>Prabhakaran, M. P., 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=Electrospun+biocomposite+nanofibrous+scaffolds+for+neural+tissue+engineering.">Electrospun biocomposite nanofibrous scaffolds for neural tissue engineering.</a> Tissue Eng Part A. 14, 1787-1797 (2008).</li><li>Xie, J., MacEwan, M. R., Schwartz, A. G., Xia, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+nanofibers+for+neural+tissue+engineering.">Electrospun nanofibers for neural tissue engineering.</a> Nanoscale. 2, 35-44 (2010).</li><li>Yao, L., O'Brien, N., Windebank, A., Pandit, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Orienting+neurite+growth+in+electrospun+fibrous+neural+conduits.">Orienting neurite growth in electrospun fibrous neural conduits.</a> J. Biomed. Mater. Res. Part B Appl. Biomater. 90, 483-491 (2009).</li><li>Sill, T. J., von Recum, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospinning:+applications+in+drug+delivery+and+tissue+engineering.">Electrospinning: applications in drug delivery and tissue engineering.</a> Biomaterials. 29, 1989-2006 (2008).</li><li>Ifkovits, J. L., Sundararaghavan, H. G., Burdick, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospinning+fibrous+polymer+scaffolds+for+tissue+engineering+and+cell+culture.">Electrospinning fibrous polymer scaffolds for tissue engineering and cell culture.</a> Journal of Visualized Experiments: JoVE. , (2009).</li><li>Sundararaghavan, H. G., Burdick, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gradients+with+depth+in+electrospun+fibrous+scaffolds+for+directed+cell+behavior.">Gradients with depth in electrospun fibrous scaffolds for directed cell behavior.</a> Biomacromolecules. 12, 2344-2350 (2011).</li><li>Meinel, A. J., Germershaus, O., Luhmann, T., Merkle, H. P., Meinel, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+matrices+for+localized+drug+delivery:+current+technologies+and+selected+biomedical+applications.">Electrospun matrices for localized drug delivery: current technologies and selected biomedical applications.</a> Eur J Pharm Biopharm. 81, 1-13 (2012).</li><li>Ji, 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=Bioactive+electrospun+scaffolds+delivering+growth+factors+and+genes+for+tissue+engineering+applications.">Bioactive electrospun scaffolds delivering growth factors and genes for tissue engineering applications.</a> Pharm. Res. 28, 1259-1272 (2011).</li><li>Burdick, J. A., Chung, C., Jia, X., Randolph, M. A., 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=Controlled+degradation+and+mechanical+behavior+of+photopolymerized+hyaluronic+acid+networks.">Controlled degradation and mechanical behavior of photopolymerized hyaluronic acid networks.</a> Biomacromolecules. 6, 386-391 (2005).</li><li>P&#233;an, J. M., 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=Optimization+of+HSA+and+NGF+encapsulation+yields+in+PLGA+microparticles.">Optimization of HSA and NGF encapsulation yields in PLGA microparticles.</a> International Journal of Pharmaceutics. 166, 105-115 (1998).</li><li>Cartiera, M. S., Johnson, K. M., Rajendran, V., Caplan, M. J., Saltzman, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Uptake+and+Intracellular+Fate+of+PLGA+Nanoparticles+in+Epithelial+Cells.">The Uptake and Intracellular Fate of PLGA Nanoparticles in Epithelial Cells.</a> Biomaterials. 30, 2790-2798 (2009).</li><li>Hollenbeck, P. J., Bamburg, J. 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> Neurons: Methods and Applications for the Cell Biologist. , (2003).</li><li>Boer, R., 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=Rat+sciatic+nerve+repair+with+a+poly-lactic-co-glycolic+acid+scaffold+and+nerve+growth+factor+releasing+microspheres.">Rat sciatic nerve repair with a poly-lactic-co-glycolic acid scaffold and nerve growth factor releasing microspheres.</a> Microsurgery. 31, 293-302 (2011).</li><li>Pujic, Z., Goodhill, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+dual+compartment+diffusion+chamber+for+studying+axonal+chemotaxis+in+3D+collagen.">A dual compartment diffusion chamber for studying axonal chemotaxis in 3D collagen.</a> Journal of Neuroscience Methods. 215, 53-59 (2013).</li><li>Madduri, S., di Summa, P., Papalo&#239;zos, M., Kalbermatten, D., Gander, B. <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+controlled+co-delivery+of+synergistic+neurotrophic+factors+on+early+nerve+regeneration+in+rats.">Effect of controlled co-delivery of synergistic neurotrophic factors on early nerve regeneration in rats.</a> Biomaterials. 31, 8402-8409 (2010).</li><li>Xu, X., 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=Polyphosphoester+microspheres+for+sustained+release+of+biologically+active+nerve+growth+factor.">Polyphosphoester microspheres for sustained release of biologically active nerve growth factor.</a> Biomaterials. 23, 3765-3772 (2002).</li><li>Yan, Q., Yin, Y., Li, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+new+PLGL-RGD-NGF+nerve+conduits+for+promoting+peripheral+nerve+regeneration.">Use new PLGL-RGD-NGF nerve conduits for promoting peripheral nerve regeneration.</a> Biomed Eng Online. 11, (2012).</li><li>Gungor-Ozkerim, P. S., Balkan, T., Kose, G. T., Sarac, A. S., Kok, F. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Incorporation+of+growth+factor+loaded+microspheres+into+polymeric+electrospun+nanofibers+for+tissue+engineering+applications.">Incorporation of growth factor loaded microspheres into polymeric electrospun nanofibers for tissue engineering applications.</a> J Biomed Mater Res A. , (2013).</li><li>Li, X., 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=Encapsulation+of+proteins+in+poly(L-lactide-co-caprolactone)+fibers+by+emulsion+electrospinning.">Encapsulation of proteins in poly(L-lactide-co-caprolactone) fibers by emulsion electrospinning.</a> Colloids Surf B Biointerfaces. 75, 418-424 (2010).</li><li>Wang, C. -. Y., 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+effect+of+aligned+core-shell+nanofibres+delivering+NGF+on+the+promotion+of+sciatic+nerve+regeneration.">The effect of aligned core-shell nanofibres delivering NGF on the promotion of sciatic nerve regeneration.</a> J Biomater Sci Polym Ed. 23, 167-184 (2012).</li><li>Liu, J. -. J., Wang, C. -. Y., Wang, J. -. G., Ruan, H. -. J., Fan, C. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Peripheral+nerve+regeneration+using+composite+poly(lactic+acid-caprolactone)/nerve+growth+factor+conduits+prepared+by+coaxial+electrospinning.">Peripheral nerve regeneration using composite poly(lactic acid-caprolactone)/nerve growth factor conduits prepared by coaxial electrospinning.</a> J Biomed Mater Res A. 96, 13-20 (2011).</li></ol>

The authors have nothing to disclose.

Muchos estudios han demostrado que las células nerviosas pueden ser dirigidas por señales topográficas (alineación de la fibra) y señales químicas (factores de crecimiento) 1,2,10,11,35. Electrospinning es un método fácil para crear fibras alineadas. Los factores de crecimiento estimulan el crecimiento del nervio, pero con el fin de incluirlos en los conductos de los nervios (NC), se requiere un método para la liberación sostenida. Para crear un sistema más robusto con ambas señales, estas dos se?...

Uno de los retos actuales en la ingeniería de tejido neural es la creación de un conducto nervioso (NC) que imita la matriz extracelular, donde los nervios crecen naturalmente. La investigación ha demostrado que las células responden a varios factores en su entorno, incluyendo las señales químicas 1-3 mecánica, topográficos, adhesivo y. Uno de los principales desafíos en este campo consiste en determinar la combinación adecuada de señales y la fabricación de un sistema que puede mantener las señales durante un período prolongado para apoyar el crecimiento celular 4. Neuronas periféricas se sabe que prefieren un sustrato blando, ser dirigidos por fibras alineadas, y responden al factor de crecimiento nervioso (NGF) 5-7. CN que puede proporcionar señales químicas durante semanas se ha demostrado para proporcionar una mejor recuperación funcional más cercana a la de los aloinjertos, el estándar de oro actual para la reparación del nervio 8,9. Materiales y métodos de producción Varios se puede utilizar para producir mecánica y topográficoal cues 10-13. Señales mecánicas son inherentes al material elegido, haciendo la selección del material apropiado para la aplicación crítica 1,13. Los métodos de producción para el control de señales topográficas incluyen la separación de fases, auto-ensamblaje y electrospinning 1,13. Para aplicaciones a microescala, microfluídica, photopatterning, aguafuerte, sanguijuelas sal, o espumas de gas también se puede utilizar 14-17. Electrospinning se ha convertido en la manera más popular para diseñar sustratos fibrosos para el cultivo de tejidos, debido a su flexibilidad y facilidad de producción 13,18-23. Nanofibras electrohiladas se fabrican aplicando un alto voltaje a una solución de polímero haciendo que repeler a sí mismo y se extienden a través de una breve pausa para descargar 24. Un andamio alineados se puede crear mediante la recopilación de las fibras sobre un mandril giratorio a tierra y andamios no alineados se recogen en una placa estacionaria 25. Adhesión de señalización se puede lograr mediante el recubrimiento del ingenio andamio fibrosoh fibronectina o la conjugación de un péptido de adhesión, tales como RGD, al HA antes de electrospinning 26. Las señales químicas, tales como factores de crecimiento, son los más difíciles de mantener durante períodos prolongados, ya que necesitan una fuente de liberación controlada. Muchos sistemas se han intentado añadir liberación controlada a las redes fibrosas electrohiladas con diferentes niveles de éxito. Estos métodos incluyen electrospinning mezcla, emulsión electrospinning, electrospinning núcleo de carcasa y conjugación de la proteína 27. Además, electrospinning se realiza tradicionalmente en un disolvente volátil, que puede afectar a la viabilidad de la proteína de 28, por lo tanto mantener la bioactividad de la proteína debe ser considerado. Este enfoque aborda específicamente la combinación de señales mecánicas, topográficos, químicos y adhesivos para crear un andamio ajustable para el crecimiento de los nervios periféricos. La mecánica del andamio se controla con precisión mediante la síntesis deÁcido Hialurónico metacrilado (HA). Los sitios metacrilación se utilizan para unir fotos reticulantes reactivos. El material reticulado ya no es soluble en agua y se divide exclusivamente por las enzimas 29. La cantidad de reticulación cambia la velocidad de degradación, la mecánica y otras propiedades físicas del material. Uso de HA con 30% metacrilación, que tiene un módulo de tracción de ~ 500 Pa, crea un sustrato blando que está cerca de la mecánica nativos de tejido neural y típicamente se prefiere por las neuronas 26,29. Electrospinning en un mandril giratorio se utiliza para crear fibras alineadas para una señal topográfica. Usando electrospinning junto con microesferas proporciona señales químicas dentro del andamio durante períodos prolongados. Para apoyar microesferas de crecimiento de neuritas que contienen NGF se utilizan para crear la señal química. A diferencia de la mayoría de materiales electrospun HA es soluble en agua por lo que el NGF no se encuentra con solventes fuertes durante la producción. Para añadir una señal de adhesivo, la scaffold está revestida con fibronectina. El sistema completo contiene los cuatro tipos de señales descritos anteriormente: (mecánicas) alineados fibras suaves (topográficos) con la liberación de microesferas de NGF (química) recubiertas con fibronectina (adhesivo). Producción y pruebas de este sistema se describe en este protocolo. El proceso comienza con la producción de las microesferas con un agua-en-aceite-en-agua de doble emulsión. La emulsión se estabiliza con un tensioactivo, alcohol polivinílico (PVA). La fase acuosa interna contiene la proteína. Como se añade a la fase oleosa, que contiene el material de la cáscara PLGA disuelto en diclorometano (DCM), el tensioactivo crea una barrera entre las fases que protegen la proteína de la DCM. Esta emulsión es de otra fase dispersa en agua que contiene PVA para crear la superficie exterior de las microesferas. La emulsión estable se agita para permitir que el DCM se evapore. Después de enjuagar y liofilización que se quedan con la microesferas cont secoaining la proteína. Después de que las microesferas se completan están listos para ser electrospun en andamios. En primer lugar se prepara la solución electrospinning. La viscosidad de la solución es crítico para la formación de fibras adecuado. Las soluciones de HA pura no cumplen con este requisito; PEO se agrega como un polímero portador para permitir electrospinning. Las microesferas se añaden a la solución y electrospun resultando en un andamio fibroso con microesferas distribuidas a lo largo. Una vez que la producción se ha completado, la proteína debe ser probado para verificar su viabilidad. Para ello, una célula primaria que responde a NGF puede ser utilizado. Este protocolo utiliza ganglios de raíz dorsal (DRG) 8-10 días embriones de pollo de edad. Los haces de células se siembran en los andamios que contienen microesferas llenas de NGF los que están vacías o. Si el NGF es todavía viable debería ver un mayor crecimiento de axones en los andamios que contienen NGF. Si el NGF ya no es viable que lo haráno promover neuritas para ampliar y debe ser similar a la de control. El procedimiento exacto se describe en el presente documento se centra en el apoyo neural, sin embargo, con modificaciones sencillas en el material, el método de electrospinning, y proteínas que el sistema puede ser optimizado para diferentes tipos de células y tejidos.

<table border="0" cellpadding="0" cellspacing="0" width="906">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">DAPI</td>
			<td style="width:208px;">Invitrogen</td>
			<td style="width:139px;">D1306</td>
			<td style="width:291px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Irgacure 2959</td>
			<td style="width:208px;">BASF</td>
			<td style="width:139px;">24650-42-8</td>
			<td style="width:291px;">Protect from light</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">PEO 900 kDa</td>
			<td style="width:208px;">Sigma-Aldrich</td>
			<td align="right" style="width:139px;">189456</td>
			<td style="width:291px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:269px;">Methacryloxethyl thiocarbamoyl rhodamine B</td>
			<td style="width:208px;">Polysciences, Inc.</td>
			<td style="width:139px;">23591-100</td>
			<td style="width:291px;">Prepare stock solution in DMSO</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Syringe Pump</td>
			<td style="width:208px;">KD Scientific</td>
			<td style="width:139px;">KDS100</td>
			<td style="width:291px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Power Source</td>
			<td style="width:208px;">Gamma High Voltage</td>
			<td style="width:139px;">ES30P-5W</td>
			<td style="width:291px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Motor</td>
			<td style="width:208px;">Triem Electric Motors, Inc</td>
			<td style="width:139px;">0132022-15</td>
			<td style="width:291px;">Must attach to a custom built mandrel</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Tachometer</td>
			<td style="width:208px;">Network Tool Warehouse</td>
			<td style="width:139px;">ESI-330</td>
			<td style="width:291px;">Use to monitor mandrel speed</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:269px;">Omnicure UV Spot Cure System with collimating adapter</td>
			<td style="width:208px;">EXFO</td>
			<td style="width:139px;">S1000</td>
			<td style="width:291px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Needles</td>
			<td style="width:208px;">Fisher Scientific</td>
			<td style="width:139px;">14-825-16H</td>
			<td style="width:291px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Coverslips</td>
			<td style="width:208px;">Fisher Scientific</td>
			<td style="width:139px;">12-545-81</td>
			<td style="width:291px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Polyvinyl Alcohol</td>
			<td style="width:208px;">Sigma-Aldrich</td>
			<td style="width:139px;">P8136-250G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Isoporopyl Alcohol</td>
			<td style="width:208px;">Sigma-Aldrich</td>
			<td style="width:139px;">I9030-500mL</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Bovine Serum Albumin (BSA)</td>
			<td style="width:208px;">Fisher Scientific</td>
			<td style="width:139px;">BP9703-100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">BSA-FITC</td>
			<td style="width:208px;">Sigma-Aldrich</td>
			<td style="width:139px;">080M7400</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">&#946;-Nerve Growth Factor (NGF)</td>
			<td style="width:208px;">R&#38;D Systems</td>
			<td style="width:139px;">1156-NG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">65:35 Poly-Lactic-Glycolic-Acid (PLGA)</td>
			<td style="width:208px;">Sigma-Aldrich</td>
			<td align="right" style="width:139px;">1001554270</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Dichloromethane</td>
			<td style="width:208px;">Sigma-Aldrich</td>
			<td style="width:139px;">34856-2L</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Coomassie (Bradford) Protein Assay</td>
			<td style="width:208px;">Thermo Scientific</td>
			<td align="right" style="width:139px;">1856209</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">3-(Trimethoxysilyl)propyl methacrylate</td>
			<td style="width:208px;">Sigma-Aldrich</td>
			<td align="right" style="width:139px;">1001558456</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Fibronectin</td>
			<td style="width:208px;">Sigma-Aldrich</td>
			<td style="width:139px;">F2006</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">DMEM</td>
			<td style="width:208px;">Lonza</td>
			<td style="width:139px;">12-604F</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">FBS</td>
			<td style="width:208px;">Atlanta Biologicals</td>
			<td style="width:139px;">S11150</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">PBS</td>
			<td style="width:208px;">Hyclone</td>
			<td style="width:139px;">SH30256.01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Glutamine</td>
			<td style="width:208px;">Fisher Scientific</td>
			<td>G7513</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Pen-Strep</td>
			<td style="width:208px;">Sigma-Aldrich</td>
			<td style="width:139px;">P4333</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:269px;">Paraformaldehyde</td>
			<td style="width:208px;">Alfa Aesar</td>
			<td style="width:139px;">A11313&#160;</td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

Las microesferas 50 ± 14 micras de diámetro con una proteína de encapsulación más del 85% se han producido y electrospun en andamios consistentemente. Tamaño se determinó mediante la formación de imágenes de muestras de microesferas de tres lotes de producción separadas. Las imágenes en las que capturaron en un microscopio óptico y longitudes donde mide utilizando software laboratorio comercial. Figura 1 muestra un histograma de la distribución de tamaños. Tasa de encapsulación también s...

Watch this Scientific Journal Video about Electrospinning Growth Factor Releasing Microspheres into Fibrous Scaffolds at JoVE.com

Electrospinning Growth Factor Releasing Microspheres into Fibrous Scaffolds

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.

Factor de Crecimiento de electrospinning Liberar microesferas en Fibrosa andamios

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

electrospinning-growth-factor-releasing-microspheres-into-fibrous

Research

JoVE Journal

Bioengineering

12.2K vistas.  Wayne State University. 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.

Video: Electrospinning Growth Factor Releasing Microspheres into Fibrous Scaffolds

Electrospinning Fundamentals: Optimizing Solution and Apparatus Parameters

Electrospun nanofiber scaffolds have been shown to accelerate the maturation, improve the growth, and direct the migration of cells in vitro. Electrospinning is a process in which a charged polymer jet is collected on a grounded collector; a rapidly rotating collector results in aligned nanofibers while stationary collectors result in randomly oriented fiber mats. The polymer jet is formed when an applied electrostatic charge overcomes the surface tension of the solution. There is a minimum concentration for a given polymer, termed the critical entanglement concentration, below which a stable jet cannot be achieved and no nanofibers will form - although nanoparticles may be achieved (electrospray). A stable jet has two domains, a streaming segment and a whipping segment. While the whipping jet is usually invisible to the naked eye, the streaming segment is often visible under appropriate lighting conditions. Observing the length, thickness, consistency and movement of the stream is useful to predict the alignment and morphology of the nanofibers being formed. A short, non-uniform, inconsistent, and/or oscillating stream is indicative of a variety of problems, including poor fiber alignment, beading, splattering, and curlicue or wavy patterns. The stream can be optimized by adjusting the composition of the solution and the configuration of the electrospinning apparatus, thus optimizing the alignment and morphology of the fibers being produced. In this protocol, we present a procedure for setting up a basic electrospinning apparatus, empirically approximating the critical entanglement concentration of a polymer solution and optimizing the electrospinning process. In addition, we discuss some common problems and troubleshooting techniques.

Electrospinning techniques can create a variety of nanofibrous scaffolds for tissue engineering or other applications. We describe here a procedure to optimize the parameters of the electrospinning solution and apparatus to obtain fibers with the desired morphology and alignment. Common problems and troubleshooting techniques are also presented.

Fundamentos electrospinning: Solución de Optimización de los parámetros y aparatos

Electrospun nanofiber scaffolds have been shown to accelerate the maturation, improve the growth, and direct the migration of cells in vitro. ...

Investigación

Bioingeniería

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.

PGS elastomérico andamios en ingeniería de tejidos arteriales

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

Axon Stretch Growth: The Mechanotransduction of Neuronal Growth

During pre-synaptic embryonic development, neuronal processes traverse short distances to reach their targets via growth cone. Over time, neuronal somata are separated from their axon terminals due to skeletal growth of the enlarging organism (Weiss 1941; Gray, Hukkanen et al. 1992). This mechanotransduction induces a secondary mode of neuronal growth capable of accommodating continual elongation of the axon (Bray 1984; Heidemann and Buxbaum 1994; Heidemann, Lamoureux et al. 1995; Pfister, Iwata et al. 2004).
Axon Stretch Growth (ASG) is conceivably a central factor in the maturation of short embryonic processes into the long nerves and white matter tracts characteristic of the adult nervous system. To study ASG in vitro, we engineered bioreactors to apply tension to the short axonal processes of neuronal cultures (Loverde, Ozoka et al. 2011). Here, we detail the methods we use to prepare bioreactors and conduct ASG. First, within each stretching lane of the bioreactor, neurons are plated upon a micro-manipulated towing substrate. Next, neurons regenerate their axonal processes, via growth cone extension, onto a stationary substrate. Finally, stretch growth is performed by towing the plated cell bodies away from the axon terminals adhered to the stationary substrate; recapitulating skeletal growth after growth cone extension.
Previous work has shown that ASG of embryonic rat dorsal root ganglia neurons are capable of unprecedented growth rates up to 10mm/day, reaching lengths of up to 10cm; while concurrently resulting in increased axonal diameters (Smith, Wolf et al. 2001; Pfister, Iwata et al. 2004; Pfister, Bonislawski et al. 2006; Pfister, Iwata et al. 2006; Smith 2009). This is in dramatic contrast to regenerative growth cone extension (in absence of mechanical stimuli) where growth rates average 1mm/day with successful regeneration limited to lengths of less than 3cm (Fu and Gordon 1997; Pfister, Gordon et al. 2011). Accordingly, further study of ASG may help to reveal dysregulated growth mechanisms that limit regeneration in the absence of mechanical stimuli.

A unique tissue engineering method was developed to elongate numerous nerve fibers in culture by recapitulating axon stretch growth; a form of nervous system growth whereby nerves elongate in conjunction with growth of the enlarging body.

El crecimiento del axón Tramo: El Mecanotransducción de crecimiento neuronal

During pre-synaptic embryonic development, neuronal processes traverse short distances to reach their targets via growth cone. Over time, neuronal somata ...

Therapeutic Gene Delivery and Transfection in Human Pancreatic Cancer Cells using Epidermal Growth Factor Receptor-targeted Gelatin Nanoparticles

More than 32,000 patients are diagnosed with pancreatic cancer in the United States per year and the disease is associated with very high mortality 1. Urgent need exists to develop novel clinically-translatable therapeutic strategies that can improve on the dismal survival statistics of pancreatic cancer patients. Although gene therapy in cancer has shown a tremendous promise, the major challenge is in the development of safe and effective delivery system, which can lead to sustained transgene expression. 
Gelatin is one of the most versatile natural biopolymer, widely used in food and pharmaceutical products. Previous studies from our laboratory have shown that type B gelatin could physical encapsulate DNA, which preserved the supercoiled structure of the plasmid and improved transfection efficiency upon intracellular delivery. By thiolation of gelatin, the sulfhydryl groups could be introduced into the polymer and would form disulfide bond within nanoparticles, which stabilizes the whole complex and once disulfide bond is broken due to the presence of glutathione in cytosol, payload would be released 2-5. Poly(ethylene glycol) (PEG)-modified GENS, when administered into the systemic circulation, provides long-circulation times and preferentially targets to the tumor mass due to the hyper-permeability of the neovasculature by the enhanced permeability and retention effect 6. Studies have shown over-expression of the epidermal growth factor receptor (EGFR) on Panc-1 human pancreatic adenocarcinoma cells 7. In order to actively target pancreatic cancer cell line, EGFR specific peptide was conjugated on the particle surface through a PEG spacer.8
Most anti-tumor gene therapies are focused on administration of the tumor suppressor genes, such as wild-type p53 (wt-p53), to restore the pro-apoptotic function in the cells 9. The p53 mechanism functions as a critical signaling pathway in cell growth, which regulates apoptosis, cell cycle arrest, metabolism and other processes 10. In pancreatic cancer, most cells have mutations in p53 protein, causing the loss of apoptotic activity. With the introduction of wt-p53, the apoptosis could be repaired and further triggers cell death in cancer cells 11. 
Based on the above rationale, we have designed EGFR targeting peptide-modified thiolated gelatin nanoparticles for wt-p53 gene delivery and evaluated delivery efficiency and transfection in Panc-1 cells.

Type B gelatin-based engineered nanovectors system (GENS) was developed for systemic gene delivery and transfection in the treatment of pancreatic cancer. By modification with epidermal growth factor receptor (EGFR) specific peptide on the surface of nanparticles, they could target on EGFR receptor and release plasmid under reducing environment, such as high intracellular glutathione concentrations.

Entrega y transfección de genes en células humanas de cáncer de páncreas con factor de crecimiento epidérmico receptor dirigidos a base de gelatina Nanovectors Ingeniería

More than 32,000 patients are diagnosed with pancreatic cancer in the United States per year and the disease is associated with very high mortality 1. ...

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.

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 fibroso Andamios de poli (glicerol-dodecanodioato) de Ingeniería Neural Los tejidos de las células madre embrionarias de ratón

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

Studying the Stoichiometry of Epidermal Growth Factor Receptor in Intact Cells using Correlative Microscopy

This protocol describes the labeling of epidermal growth factor receptor (EGFR) on COS7 fibroblast cells, and subsequent correlative fluorescence microscopy and environmental scanning electron microscopy (ESEM) of whole cells in hydrated state. Fluorescent quantum dots (QDs) were coupled to EGFR via a two-step labeling protocol, providing an efficient and specific protein labeling, while avoiding label-induced clustering of the receptor. Fluorescence microscopy provided overview images of the cellular locations of the EGFR. The scanning transmission electron microscopy (STEM) detector was used to detect the QD labels with nanoscale resolution. The resulting correlative images provide data of the cellular EGFR distribution, and the stoichiometry at the single molecular level in the natural context of the hydrated intact cell. ESEM-STEM images revealed the receptor to be present as monomer, as homodimer, and in small clusters. Labeling with two different QDs, i.e.,&#160;one emitting at 655 nm and at 800 revealed similar characteristic results.

This protocol describes the labeling of epidermal growth factor receptor (EGFR) on COS7 fibroblast cells, and subsequent correlative light- and electron microscopy of whole cells in hydrated state. The label contained fluorescent quantum dots. The protocol can be used to study the stoichiometry of EGFR at the single molecule level.

El estudio de la estequiometría de factor de crecimiento epidérmico en células intactas utilizando microscopía correlativa

This protocol describes the labeling of epidermal growth factor receptor (EGFR) on COS7 fibroblast cells, and subsequent correlative fluorescence ...

Polyelectrolyte Complex for Heparin Binding Domain Osteogenic Growth Factor Delivery

During reconstructive bone surgeries, supraphysiological amounts of growth factors are empirically loaded onto scaffolds to promote successful bone fusion. Large doses of highly potent biological agents are required due to growth factor instability as a result of rapid enzymatic degradation as well as carrier inefficiencies in localizing sufficient amounts of growth factor at implant sites. Hence, strategies that prolong the stability of growth factors such as BMP-2/NELL-1, and control their release could actually lower their efficacious dose and thus reduce the need for larger doses during future bone regeneration surgeries. This in turn will reduce side effects and growth factor costs. Self-assembled PECs have been fabricated to provide better control of BMP-2/NELL-1 delivery via heparin binding and further potentiate growth factor bioactivity by enhancing in vivo stability. Here we illustrate the simplicity of PEC fabrication which aids in the delivery of a variety of growth factors during reconstructive bone surgeries.

Self-assembled polyelectrolyte complexes (PEC) fabricated from heparin and protamine were deposited on alginate beads to entrap and regulate the release of osteogenic growth factors. This delivery strategy enables a 20-fold reduction of BMP-2 dose in spinal fusion applications. This article illustrates the benefits and fabrication of PECs.

Complejo de polielectrolito para la unión a heparina de entrega osteogénico Factor de Crecimiento de dominio

During reconstructive bone surgeries, supraphysiological amounts of growth factors are empirically loaded onto scaffolds to promote successful bone ...

Preparation and Characterization of Novel HDL-mimicking Nanoparticles for Nerve Growth Factor Encapsulation

The objective of this article is to introduce preparation and characterization methods for nerve growth factor (NGF)-loaded, high-density, lipoprotein (HDL)-mimicking nanoparticles (NPs). HDLs are endogenous NPs and have been explored as vehicles for the delivery of therapeutic agents. Various methods have been developed to prepare HDL-mimicking NPs. However, they are generally complicated, time consuming, and difficult for industrial scale-up. In this study, one-step homogenization was used to mix the excipients and form the prototype NPs. NGF is a water-soluble protein of 26 kDa. To facilitate the encapsulation of NGF into the lipid environment of HDL-mimicking NPs, protamine USP was used to form an ion-pair complex with NGF to neutralize the charges on the NGF surface. The NGF/protamine complex was then introduced into the prototype NPs. Apolipoprotein A-I was finally coated on the surface of the NPs. NGF HDL-mimicking NPs showed preferable properties in terms of particle size, size distribution, entrapment efficiency, in vitro release, bioactivity, and biodistribution. With the careful design and exploration of homogenization in HDL-mimicking NPs, the procedure was greatly simplified, and the NPs were made scalable. Moreover, various challenges, such as separating unloaded NGF from the NPs, conducting reliable in vitro release studies, and measuring the bioactivity of the NPs, were overcome.

Simple homogenization was used to prepare novel, high-density, lipoprotein-mimicking nanoparticles to encapsulate nerve growth factor. Challenges, detailed protocols for nanoparticle preparation, in vitro characterization, and in vivo studies are described in this article.

Preparación y caracterización de nuevas nanopartículas que imitan las HDL para la encapsulación del factor de crecimiento nervioso

The objective of this article is to introduce preparation and characterization methods for nerve growth factor (NGF)-loaded, high-density, lipoprotein ...

Melt Electrospinning Writing of Three-dimensional Poly(&#949;-caprolactone) Scaffolds with Controllable Morphologies for Tissue Engineering Applications

This tutorial reflects on the fundamental principles and guidelines for electrospinning writing with polymer melts, an additive manufacturing technology with great potential for biomedical applications. The technique facilitates the direct deposition of biocompatible polymer fibers to fabricate well-ordered scaffolds in the sub-micron to micro scale range. The establishment of a stable, viscoelastic, polymer jet between a spinneret and a collector is achieved using an applied voltage and can be direct-written. A significant benefit of a typical porous scaffold is a high surface-to-volume ratio which provides increased effective adhesion sites for cell attachment and growth. Controlling the printing process by fine-tuning the system parameters enables high reproducibility in the quality of the printed scaffolds. It also provides a flexible manufacturing platform for users to tailor the morphological structures of the scaffolds to their specific requirements. For this purpose, we present a protocol to obtain different fiber diameters using melt electrospinning writing (MEW) with a guided amendment of the parameters, including flow rate, voltage and collection speed. Furthermore, we demonstrate how to optimize the jet, discuss often experienced technical challenges, explain troubleshooting techniques and showcase a wide range of printable scaffold architectures.

Melt Electrospinning Writing of Three-dimensional Poly(&amp;#949;-caprolactone) Scaffolds with Controllable Morphologies for Tissue Engineering Applications

This protocol serves as a comprehensive guideline to fabricate scaffolds via electrospinning with polymer melts in a direct writing mode. We systematically outline the process and define the appropriate parameter settings for achieving targeted scaffold architectures.

Escritura de Electrospinning de andamios Poly(ε-caprolactone) tridimensional con morfologías controlables para aplicaciones de ingeniería de tejidos del derretimiento

This tutorial reflects on the fundamental principles and guidelines for electrospinning writing with polymer melts, an additive manufacturing technology ...

Fabrication of Decellularized Cartilage-derived Matrix Scaffolds

Osteochondral defects lack sufficient intrinsic repair capacity to regenerate functionally sound bone and cartilage tissue. To this extent, cartilage research has focused on the development of regenerative scaffolds. This article describes the development of scaffolds that are completely derived from natural cartilage extracellular matrix, coming from an equine donor. Potential applications of the scaffolds include producing allografts for cartilage repair, serving as a scaffold for osteochondral tissue engineering, and providing in vitro models to study tissue formation. By decellularizing the tissue, the donor cells are removed, but many of the natural bioactive cues are thought to be retained. The main advantage of using such a natural scaffold in comparison to a synthetically produced scaffold is that no further functionalization of polymers is required to drive osteochondral tissue regeneration. The cartilage-derived matrix scaffolds can be used for bone and cartilage tissue regeneration in both in vivo and in vitro settings.

Decellularized cartilage-derived scaffolds can be used as a scaffold to guide cartilage repair and as a means to regenerate osteochondral tissue. This paper describes the decellularization process in detail and provides suggestions to use these scaffolds in in vitro settings.

Fabricación de andamios de Decellularized derivados de cartílago matriz

Osteochondral defects lack sufficient intrinsic repair capacity to regenerate functionally sound bone and cartilage tissue. To this extent, cartilage ...