This work was supported by the Belgian National Foundation for Scientific Research (F.R.S.-FNRS) through &#8220;MIS Confocal Microscopy&#8221;, &#8220;Cr&#233;dit aux Chercheurs&#8221; grants and the &#8220;Nanomotility FRFC project&#8221; (no. 2.4622.11). T.G. doctoral fellowship is supported by the Foundation for Training in Industrial and Agricultural Research (FRIA). The authors gratefully acknowledge Sylvain Desprez for mechanical characterization and G&#233;raldine Circelli for confocal imaging.

1. activar la superficie del cubreobjetos de vidrio <ol><li> Lugar cubreobjetos de vidrio circulares (25 mm de diámetro) en una placa de Petri y frotis solución 0,1 M de NaOH en él durante 5 min (campana química recomendada). </li><li> Eliminar la solución de NaOH y sumergirse plenamente cubreobjetos con ddH 2 O estéril durante 20 minutos mientras se balancea suavemente sobre una placa oscilante en una campana de cultivo estéril. </li><li> Escurrir estéril ddH2O y repita el paso 1.2. </li><li> Quitar los cubreobjetos con unas pinzas estériles y colocarlos en una nueva placa de Petri con la cara activado para arriba. </li><li> Cubreobjetos seco bajo un flujo constante de gas nitrógeno de alta pureza. </li><li> En una campana de cultivo estéril, frotis de una capa fina de acrilato de 3 (trimetoxisilil) propil (92%) en el lado activada del cubreobjetos durante 1 h. </li><li> Lavar extensivamente cubreobjetos de vidrio con 3 lavados de ddH 2 O estéril y sumergirlos en ddH 2 O estéril en una nueva placa de Petri. </li><li> Toque en la placa de Petricon Parafilm y colocarlo en una placa del balancín con agitación suave durante 10 minutos. </li><li> Quitar los cubreobjetos de ddH2O con pinzas estériles con puntas finas y colocarlas en una nueva placa de Petri con la cara activado para arriba. </li><li> Almacenar a temperatura ambiente en un lugar seco con papel de aluminio para evitar que el polvo se pegue a los cubreobjetos. </li></ol> 2 Preparación de hidrogeles hidroxi-Paam <ol><li> Preparar un peso de 65 mg de acrilamida N-hidroxietilo (HEA) en un tubo Eppendorf de 1,5 ml. Es importante para preparar una solución HEA fresco. </li><li> Añadir 1 ml de 50 mM de tampón HEPES a HEA y mezclar usando un agitador de vórtice hasta la disolución completa de la HEA. </li><li> Añadir 400 l de 40% w / w en HEPES solución de acrilamida y el volumen requerido de 2% w / w en HEPES solución de bis-acrilamida (véase la Tabla 1) para llegar a la rigidez de hidrogel deseada. Ajuste con HEPES 50 mM a un volumen final de 5 ml. </li><li> Mezclar la solución con un vórtice y desgasificar iten una cámara de vacío durante 20 min con el fin de reducir la concentración de oxígeno dentro de la solución, lo que impide la polimerización hidroxi-PAAM. </li><li> Bajo una campana estéril, filtrar la solución desgasificada con un filtro de tamaño de poro 0,2 micras con el fin de esterilizarlo. </li><li> Activar cubreobjetos de vidrio circulares (22 mm de diámetro) en un limpiador UV / ozono durante 7 min. </li><li> Preparar 100 l de solución de persulfato de amonio al 10% (APS), es decir 10 mg de APS en 100 l ddH 2 O. Es importante preparar una solución de APS fresco. </li><li> Añadir 2,5 l de tetrametilendiamina (TEMED) y 25 l de solución de APS a la solución esterilizada hidroxi-Paam (paso 2.5) para iniciar la polimerización. Mezclar la solución por 3 pipeteados sucesivos sin la introducción de burbujas, en condiciones estériles. </li><li> Bajo una campana estéril, coloque una gota de 25 l de la solución de hidroxi-Paam sobre un cubreobjetos de 25 mm (disponible desde el paso 1.9) e inmediatamente colocar un gl 22 mmcubreobjetos culo (preparado en el paso 2.5) en la parte superior de la gotita para exprimir la solución hidroxi-PAAM. Centre el cubreobjetos de vidrio de 22 mm con pinzas estériles y suavizar las burbujas. </li><li> Permitir hidrogeles-hidroxi Paam para polimerizar a temperatura ambiente durante 15 min. Invertir manualmente la solución hidroxi-Paam restante en el tubo de Eppendorf a seguir la finalización del proceso de polimerización. </li><li> Sumerja totalmente con cubreobjetos estéril ddH 2 O y separar cuidadosamente los cubreobjetos de 22 mm de vidrio mediante la introducción del borde de una hoja de afeitar entre los 22 mm cubreobjetos de vidrio y la capa de hidrogel hidroxi-PAAM. </li><li> Lave hidrogeles Paam hidroxi con PBS estéril (3 intercambios de PBS) y dejar que los geles totalmente inmersos en PBS estéril para mantener la hidratación. </li><li> Guarde hidrogeles Paam hidroxi en PBS estéril a 4 ° C hasta por 3 días. </li></ol> 3. polidimetilsiloxano (PDMS) Microstamp Fabrication NOTA: La fabricación de un maestro de silicio se requiere antes de stata los PDMS fabricación microstamp. Esta microfabricación de un maestro de silicio se puede hacer mediante técnicas litográficas, lo que requiere equipo especializado y la formación. Se anima Colaboraciones con una instalación de nanofabricación para fabricar el maestro de silicio. Como alternativa, póngase en contacto con una empresa que fabrica maestros silicio microestructurada a medida bajo demanda. Es importante señalar que la fabricación del maestro de silicio sólo necesita hacerse una vez. De hecho, los maestros de silicio microestructuradas pueden utilizarse indefinidamente para producir sellos elastoméricos. <ol><li> Mezcla de PDMS y el agente de curado en una proporción de 10: 1 en un vaso de precipitados de plástico y mezclar bien con una pipeta durante 10 min. </li><li> Desgasificar la mezcla de PDMS al vacío para eliminar las burbujas de aire que se formaron durante la etapa 3.1. </li><li> Coloque el maestro de silicio microestructurada en una placa de Petri y emitir una capa gruesa de 10 mm de mezcla desgasificada PDMS en él sin que se formen burbujas. </li><li> Dejar curar el PDMS durante 2 horas a 60 ° C en unhorno. </li><li> En un entorno libre de polvo, de despegar de la capa de PDMS y los impuestos especiales 1 cm 2 microstamps con un bisturí. </li><li> El uso de pinzas, lugar PDMS microstamps patrón-en una placa de Petri. </li></ol> 4. micropatterning hidroxi-Paam hidrogeles <ol><li> Coloque PDMS microstamps en una mezcla de etanol / agua (50/50) solución y se somete a ultrasonidos durante 15 min. </li><li> Secar los sellos con una corriente de flujo de nitrógeno y colocarlos patrón-en un limpiador UV / Ozono (λ &lt;200 nm) durante 7 min. </li><li> Bajo una campana estéril, colocar una gota de 150 l de una solución de proteína deseada (por ejemplo, 100 mg / ml de laminina en PBS o 25 mg / ml de fibronectina en PBS) sobre la superficie microestructurada de un 1 cm-2 PDMS sello. </li><li> Opcional: Modificar la concentración de la solución de proteína para modular la densidad de células ligando. </li><li> Corre la solución de proteína a través de la superficie del sello moviéndolo con una punta estéril de una pipeta de una hacia la esquina deel sello. </li><li> Deje la solución de proteína para adsorber en el sello PDMS durante 60 minutos bajo una campana estéril. Apague las lámparas para evitar daño a las proteínas. </li><li> Bajo una campana estéril, transferir hidroxi-Paam cubreobjetos recubiertos (disponibles desde el paso 2,13) ​​en una placa de Petri. </li><li> Eliminar el exceso de PBS de la superficie de sustratos hidroxi-Paam con una corriente de nitrógeno bajo en condiciones estériles. Detener el procedimiento tan pronto como se observó ninguna evidencia de agua estancada en la superficie del gel. El gel no debe ser secado a fondo en esta etapa. </li><li> Seca cuidadosamente la superficie estructurada de los PDMS sello con un flujo constante de gas nitrógeno de alta pureza. </li><li> Sujete el sello recubierto de proteína con pinzas de tejidos vestidores y coloque la superficie estructurada en contacto con la superficie del hidrogel seco. Aplicar puntos de presión breves con la punta de las pinzas en la parte superior del sello PDMS para asegurar un buen contacto entre microfeatures sello y de la superficie del hidrogel. </li><li> Deje el sello PDMS en el thsuperficie del hidrogel e durante 1 hora a RT. </li><li> Retire con cuidado PDMS sellos de hidrogeles hidroxi-Paam con pinzas de tejidos vestidores y seguir el paso 4.1 para limpiar el sello. </li><li> Lavar ampliamente los hidrogeles-hidroxi Paam sellados por 3 intercambios de PBS (pH = 7,4) en condiciones estériles durante 10 min por intercambio. </li><li> Opcionales: micropatrones adicionales de otras proteínas ECM se pueden añadir a la superficie hidroxi-Paam siguiendo los pasos 4.5 a 4.11. </li><li> Zonas no impresas pasivar con una solución estéril de BSA a 5 mg / ml en PBS durante una noche a 4 ° C bajo una agitación suave en un plato oscilante. </li><li> Lavar ampliamente por 3 intercambios de PBS (pH = 7,4) en condiciones estériles durante 10 min por intercambio. En esta etapa, los hidrogeles-hidroxi Paam estampadas se pueden almacenar a 4 ° C durante hasta una semana. </li></ol> 5. deposición de células en micropatterned hidroxi-Paam hidrogeles <ol><li> Incubar cubreobjetos en medio celular durante 30-45 minutos antes de chapado cells. </li><li> Lavar las células adherentes cultivadas en un 75 cm 2 frasco de cultivo con PBS estéril a 37 ° C y separarlo con 3 ml de tripsina-EDTA o accutase de 10 min. </li><li> Transferir la cantidad deseada de pre-calentado completa medio de crecimiento apropiado para su línea de células en el matraz que contiene las células desprendidas y centrifugar la suspensión celular durante 3 minutos a 650 x g. </li><li> Eliminar el sobrenadante con una micropipeta y resuspender las células en medio de cultivo completo en 15-20.000 células / ml. </li><li> Añadir 4 ml de la solución de células a un cubreobjetos microestructurada (obtenido del Paso 5.1) y colocar el cubreobjetos de células-cubierto en un incubador de cultivo a 37 ° C y 5% de humedad durante 1-2 horas. </li><li> Aspirar suavemente las células no unidas y reemplazar el medio de cultivo. Devolver las células unidas a la incubadora y dejar que se extienden completamente (3-6 horas, dependiendo del tipo de célula). </li></ol>

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No conflicts of interest declared.

Muchos en observaciones in vitro de la biología celular moderna se han realizado en cubreobjetos de vidrio rígidas, a menudo recubiertos con una fina capa de proteínas ECM o péptidos sintéticos que contienen la secuencia RGD. Sin embargo, dichos sustratos de cultivo básicas no recapitulan toda la complejidad fisicoquímica del ECM y por lo tanto no proporcionan un modelo preciso para estudiar procesos celulares mechanotransduction. Para hacer frente a este problema, proponemos una alternativa sim...

Muchos aspectos de la microambiente celular local (por ejemplo, rigidez, tamaño de poro, la naturaleza de las proteínas, o la densidad de células ligando) proporcionan un conjunto de coordenadas de las señales reguladoras que controlan los procesos celulares, tales como la motilidad, la proliferación celular, la diferenciación y la expresión génica. Las modificaciones de las propiedades fisicoquímicas del medio ambiente extracelular pueden ser percibidos por las células y causan diferentes consecuencias fisiológicas, incluyendo la deformación de la polarización celular, la migración, y diferenciación. No queda claro, sin embargo, cómo las células se traducen modificaciones ECM en señales bioquímicas celulares. Por lo tanto, de gran importancia para diseñar controlada en microambientes in vitro que pueden reproducir las interacciones entre las células y su microambiente para el estudio de las vías de mechanotransduction es. Para abordar este problema, hemos introducido recientemente un nuevo método 1, llamado hidrogeles-Paam hidroxi, para generar fácilmente de dos moneda de diez centavosmatrices nsional suaves que permiten controlar de forma independiente importantes señales mechanotransduction: matriz de rigidez, geometría celular y de confinamiento, la naturaleza de la proteína y la densidad de células ligando. ECM dirige los procesos celulares a través de gradientes en morfógenos (quimiotaxis), proteínas adhesivas (Haptotaxis) y rigidez (durotaxis). En los últimos decenios, avanzada en plataformas in vitro han sido desarrollados para aislar estas señales extracelulares con el fin de desentrañar cómo las células son capaces de traducir las características bioquímicas y biofísicas en los procesos fisiológicos 2-5. Se han desarrollado por haz de electrones 6, 7 fotolitografía, la inmovilización fotoquímica 8, o técnicas de plasma asistida 9 para dirigir el crecimiento de las células vivas sobre sustratos micropatterned. Aunque estas técnicas han dado resultados importantes, la mayoría de ellos no permiten la discriminación entre la influencia individual de diferentes señales en el comportamiento celulary requieren instalaciones técnicas que pocos laboratorios pueden permitirse. Entre estas técnicas, la impresión por microcontacto (μCP), ha surgido como un método robusto y accesible para crear micro-islas de células adhesivo 10. Más recientemente, grandes esfuerzos 11-14 se han hecho para desarrollar μCP en hidrogeles con rigideces sintonizables con el fin de reproducir la amplia gama de rigideces observadas en los tejidos vivos. Entre estas obras, la poliacrilamida (PAAM) se ha hecho popular el 15 y ya es una de las matrices a base de polímeros más utilizados para los ensayos de biomecánica celulares. Superficies Paam son comúnmente funcionalizado con el agente de reticulación heterobifuncional sulfosuccinimidil proteínas-N-6-[4 &#39;-azido-2&#39;-nitrophenylamido] (sulfo-SANPAH) y ECM están unidos a la superficie por la activación de UV de la sulfo-nitrofenil SANPAH grupos azida 16. Otra técnica consiste en hidrazina de acoplamiento a las proteínas que han sido severamente oxidadascon peryodato 17. Hynd y colaboradores introdujeron una técnica para modelando superficies de hidrogel biomiméticos con proteínas y péptidos que requiere fotopolimerización en presencia de un monómero de acriloílo estreptavidina 18. Más recientemente, Tseng et al. Han informado de un nuevo método micropatterning 19 basado en la exposición UV profunda de PAAM a través de una máscara de cuarzo óptico que requiere incubar PA geles activados con 1-etil-3-[3-dimetilaminopropil] carbodiimida (EDC) y N-hidroxisuccinimida (NHS) soluciones de agua antes de añadir la proteína. A pesar de la capacidad de estas técnicas para crear homogéneos y reproducibles micropatrones proteínas, la mayoría de ellos sufren limitaciones importantes: los procesos de síntesis larga (por ejemplo, diálisis, liofilización, etc), compuestos químicos caros (por ejemplo, ácido hialurónico, sulfo-SANPAH) de profundidad o UV irradiación. Además, estas técnicas no permiten la modulación independiente de la rigidez del sustrato, micropatróngeometría, ECM proteína naturaleza, y la densidad de células ligando. Teniendo en cuenta estas limitaciones, hemos desarrollado un enfoque basado en acrilamida novedoso y simple que permite la inmovilización de una variedad de proteínas y biomoléculas en hidrogeles blandos y permite la sintonización independiente de señales mechanotransduction el fin de descifrar su papel en las funciones celulares. En lugar de tratar hidrogeles Paam con compuestos químicos agresivos, se introduce un monómero de acrilamida comercial con grupos hidroxilo durante la polimerización Paam. Esta sencilla operación supera la propiedad anti-adhesivo intrínseca de hidrogeles Paam sin otros requisitos técnicos. La presencia de grupos hidroxilo conduce a una alta afinidad de los hidrogeles-hidroxi Paam para las proteínas y biomoléculas que forman interacciones de enlaces de hidrógeno. En combinación con μCP, hidrogeles-hidroxi Paam permiten una rápida generación de plataforma de la cultura de dos dimensiones con un control independienteen la rigidez de la matriz, el tipo de proteínas ECM, la densidad de células ligando y adhesividad confinado, que se imaginó ser una plataforma poderosa para el estudio mecanotransducción. El objetivo de este protocolo es proporcionar la información necesaria para hacer fácilmente hidrogeles Paam hidroxi sin ninguna experiencia en la ciencia de materiales. El objetivo final es proporcionar un medio para que los investigadores hacen preguntas fisiológicamente relevantes a nivel celular y de tejidos que pueden conducir a una mejor comprensión de las vías mechanotransduction involucradas en mecanismos fisiopatológicos.

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		<tr height="64">
			<td height="64" style="height:64px;width:216px;">UV/Ozone Photoreactor</td>
			<td style="width:71px;">Ultra-Violet Products</td>
			<td style="width:119px;">Model PR-100</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Rocking plate</td>
			<td style="width:71px;">IKAcWerke</td>
			<td style="width:119px;">Model KS 130 Basic</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Vortexer</td>
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			<td style="width:167px;"></td>
		</tr>
		<tr height="85">
			<td height="85" style="height:85px;width:216px;">Vacuum degassing chamber</td>
			<td style="width:71px;">Applied Vacuum Engineering</td>
			<td style="width:119px;">DP- 8-KIT</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Parafilm</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">P7793-1EA</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Stainless steel forceps with fine tip</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">Z225304-1EA</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Dressing tissue forceps</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">F4392-1EA</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Petri dishes in polystyrene</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">P5731-500EA</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Aluminium foil, thickness 0.5&#160;mm</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">266574-3.4G</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Isopore membrane filter (0,2 &#181;m pore size)</td>
			<td style="width:71px;">Millipore</td>
			<td style="width:119px;">GTTP Filter code</td>
			<td style="width:167px;"></td>
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			<td height="43" style="height:43px;width:216px;">Round glass coverslip (22 mm diameter)</td>
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		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Round glass coverslip (25 mm diameter)</td>
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			<td style="width:119px;">GG-25</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Variable volume micropipette</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">Z114820</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Protein microcentrifuge tubes</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">Z666505-100EA</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Scalpel handles</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">S2896-1EA</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Scalpel blades</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">S2771-100EA</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Cell culture flasks (75 cm2)</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">CLS430641</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Ultrasonic bath tray, solid (stainless steel)</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">Z613983-1EA</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;"></td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Name of the Reagent</td>
			<td style="width:71px;">Company</td>
			<td style="width:119px;">Catalogue Number</td>
			<td style="width:167px;">Comments</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Polydimethylsiloxane&#160;</td>
			<td style="width:71px;">Dow Corning</td>
			<td style="width:119px;">Sylgard 184 silicone elastomer kit</td>
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		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Acrylamide (powder)</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">A3553</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">N,N&#8217;-Methylenebis(acrylamide)</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">146072</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">N-Hydroxyethylacrylamide</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">697931</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">N,N,N&#8217;,N&#8217;-Tetramethylethylenediamine</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">T9281</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Amonium PerSulfate (APS)</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">A3678</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">3-(Trimetoxysilyl)propyle acrylate</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">1805</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">Human Plasma Fibronectin</td>
			<td style="width:71px;">Millipore</td>
			<td style="width:119px;">FC010</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Laminin from EHS</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">L2020</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Sodium hydroxyde</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">221465-25G</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;width:216px;">Double-distilled water (ddH2O)</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Endothelial cell growth medium</td>
			<td style="width:71px;">Cells Applications</td>
			<td style="width:119px;">211K-500</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Human Umbilical Vein Endothelial Cells (HUVEC)</td>
			<td style="width:71px;">Invitrogen</td>
			<td style="width:119px;">C-003-5C</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Accutase</td>
			<td style="width:71px;">PAA laboratories</td>
			<td style="width:119px;">L11-007</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="47">
			<td height="47" style="height:47px;width:216px;">HEPES buffer solution 1M in H20</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">83264-500ML-F</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Antibiotics-antimycotics</td>
			<td style="width:71px;">PAA laboratories</td>
			<td style="width:119px;">P11-002</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Phosphate Buffer Saline solution</td>
			<td style="width:71px;">PAA laboratories</td>
			<td style="width:119px;">H15-002</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Alexa Fluor 488 Phaloidin</td>
			<td style="width:71px;">Molecular Probes</td>
			<td style="width:119px;">A12379</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Anti-vinculin antibody produced in mouse</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">V9131</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Goat anti-mouse antibody-tetramethylrhodamine</td>
			<td style="width:71px;">Molecular Probes</td>
			<td style="width:119px;">T-2762</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Anti-Fibronectin</td>
			<td rowspan="2" style="width:71px;">Sigma-Aldrich</td>
			<td rowspan="2" style="width:119px;">F3648</td>
			<td rowspan="2" style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">(rabbit)</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Streptavidin&#160;</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">41469</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Anti-Laminin antibody</td>
			<td rowspan="2" style="width:71px;">Sigma-Aldrich</td>
			<td rowspan="2" style="width:119px;">L9393</td>
			<td rowspan="2" style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">(rabbit)</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Anti-rabbit IgG-FITC</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">F7512</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Trypsin-EDTA solution</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">T3924-100ML</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Absolute ethanol</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">459844-2.5L</td>
			<td style="width:167px;"></td>
		</tr>
	</tbody>
</table>

preparation of hydroxy-paam hydrogels for decoupling the effects of mechanotransduction cues

Ahora está bien establecido que muchas funciones celulares están reguladas por interacciones de las células con señales fisicoquímicas y mecánicas de su matriz extracelular (ECM) medio ambiente. Las células eucariotas constantemente perciben su microambiente local a través mechanosensors superficie para transducir cambios físicos de la ECM en señales bioquímicas, e integrar estas señales para lograr cambios específicos en la expresión génica. Curiosamente, los parámetros físico-químicas y mecánicas de la pareja ECM puede uno con el otro para regular el destino celular. Por lo tanto, la clave para entender mecanotransducción es disociar la contribución relativa de las señales de ECM en las funciones celulares. Aquí se presenta un protocolo experimental detallado para generar rápida y fácilmente hidrogeles biológicamente relevantes para la puesta a punto independiente de señales mechanotransduction in vitro. Nosotros, los hidrogeles de poliacrilamida modificados químicamente (PAAM) para superar sus intrínsecamente no ADHESive propiedades mediante la incorporación de monómeros de acrilamida hidroxilo funcionalizado durante la polimerización. Obtuvimos una novela Paam hidrogel, llamado hidroxi-Paam, que permite la inmovilización de cualquier naturaleza deseada de las proteínas ECM. La combinación de hidroxi-Paam hidrogeles con impresión por microcontacto permite controlar independientemente la morfología de las células individuales, la rigidez de la matriz, la naturaleza y la densidad de las proteínas ECM. Proporcionamos un método simple y rápido que se puede establecer en cada laboratorio de biología para estudiar en los procesos mechanotransduction celular in vitro. Estamos validar esta nueva plataforma de dos dimensiones mediante la realización de experimentos en células endoteliales que demuestran un acoplamiento mecánico entre la rigidez del ECM y el núcleo.

La Figura 1A presenta la co-polimerización de acrilamida (AAM) y bisacrilamida (bis-AAM) con N-hydroxyethylacrylamide (HEA) monómeros que contienen un hidroxilo primario formado por polimerización radicalar al azar una red hidrofílica de poliacrilamida con grupos hidroxilo incorporados (hidroxi-PAAM) . En este protocolo, un peso 65 mg de HEA se debe diluir en un volumen de 1 ml de HEPES. Sabiendo que la densidad de la HEA es aproximadamente igual a uno, se supone que se obtiene un volumen de trabajo...

Watch this Scientific Journal Video about Preparation of Hydroxy-PAAm Hydrogels for Decoupling the Effects of Mechanotransduction Cues at JoVE.com

Preparation of Hydroxy-PAAm Hydrogels for Decoupling the Effects of Mechanotransduction Cues

Presentamos un nuevo hidrogel de poliacrilamida, llamado hidroxi-Paam, que permite una unión directa de las proteínas ECM con costo o experiencia mínima. La combinación de hidroxi-Paam hidrogeles con impresión por microcontacto facilita el control independiente de muchas señales del microambiente celular natural para el estudio de mechanostransduction celular.

Preparación de hidroxi-Paam hidrogeles para desacoplar los efectos de mecanotransducción Cues

It is now well established that many cellular functions are regulated by interactions of cells with physicochemical and mechanical cues of their ...

preparation-hydroxy-paam-hydrogels-for-decoupling-effects

Research

JoVE Journal

Bioengineering

13.2K vistas.  Université de Mons.  Presentamos un nuevo hidrogel de poliacrilamida, llamado hidroxi-Paam, que permite una unión directa de las proteínas ECM con costo o experiencia mínima. La combinación de hidroxi-Paam hidrogeles con impresión por microcontacto facilita el control independiente de muchas señales del microambiente celular natural para el estudio de mechanostransduction celular. 

Video: Preparation of Hydroxy-PAAm Hydrogels for Decoupling the Effects of Mechanotransduction Cues

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 ...

Investigación

Bioingeniería

Alginate Hydrogels for Three-Dimensional Organ Culture of Ovaries and Oviducts

Ovarian cancer is the fifth leading cause of cancer deaths in women and has a 63% mortality rate in the United States1. The cell type of origin for ovarian cancers is still in question and might be either the ovarian surface epithelium (OSE) or the distal epithelium of the fallopian tube fimbriae2,3. Culturing the normal cells as a primary culture in vitro will enable scientists to model specific changes that might lead to ovarian cancer in the distinct epithelium, thereby definitively determining the cell type of origin. This will allow development of more accurate biomarkers, animal models with tissue-specific gene changes, and better prevention strategies targeted to this disease.
Maintaining normal cells in alginate hydrogels promotes short term in vitro culture of cells in their three-dimensional context and permits introduction of plasmid DNA, siRNA, and small molecules. By culturing organs in pieces that are derived from strategic cuts using a scalpel, several cultures from a single organ can be generated, increasing the number of experiments from a single animal. These cuts model aspects of ovulation leading to proliferation of the OSE, which is associated with ovarian cancer formation. Cell types such as the OSE that do not grow well on plastic surfaces can be cultured using this method and facilitate investigation into normal cellular processes or the earliest events in cancer formation4.
Alginate hydrogels can be used to support the growth of many types of tissues5. Alginate is a linear polysaccharide composed of repeating units of &beta;-D-mannuronic acid and &alpha;-L-guluronic acid that can be crosslinked with calcium ions, resulting in a gentle gelling action that does not damage tissues6,7. Like other three-dimensional cell culture matrices such as Matrigel, alginate provides mechanical support for tissues; however, proteins are not reactive with the alginate matrix, and therefore alginate functions as a synthetic extracellular matrix that does not initiate cell signaling5. The alginate hydrogel floats in standard cell culture medium and supports the architecture of the tissue growth in vitro.
A method is presented for the preparation, separation, and embedding of ovarian and oviductal organ pieces into alginate hydrogels, which can be maintained in culture for up to two weeks. The enzymatic release of cells for analysis of proteins and RNA samples from the organ culture is also described. Finally, the growth of primary cell types is possible without genetic immortalization from mice and permits investigators to use knockout and transgenic mice.

Culture of normal cells in their three-dimensional context represents an alternative method to study early events required for cellular transformation and tumorigenesis. This method is used to grow normal ovarian and oviductal cells to study early events in ovarian cancer formation.

Los hidrogeles de alginato para la cultura del órgano en tres dimensiones de los ovarios y oviductos

Ovarian cancer is the fifth leading cause of cancer deaths in women and has a 63% mortality rate in the United States1. The cell type of origin for ...

Low Molecular Weight Protein Enrichment on Mesoporous Silica Thin Films for Biomarker Discovery

The identification of circulating biomarkers holds great potential for non invasive approaches in early diagnosis and prognosis, as well as for the monitoring of therapeutic efficiency.1-3 The circulating low molecular weight proteome (LMWP) composed of small proteins shed from tissues and cells or peptide fragments derived from the proteolytic degradation of larger proteins, has been associated with the pathological condition in patients and likely reflects the state of disease.4,5 Despite these potential clinical applications, the use of Mass Spectrometry (MS) to profile the LMWP from biological fluids has proven to be very challenging due to the large dynamic range of protein and peptide concentrations in serum.6 Without sample pre-treatment, some of the more highly abundant proteins obscure the detection of low-abundance species in serum/plasma. Current proteomic-based approaches, such as two-dimensional polyacrylamide gel-electrophoresis (2D-PAGE) and shotgun proteomics methods are labor-intensive, low throughput and offer limited suitability for clinical applications.7-9 Therefore, a more effective strategy is needed to isolate LMWP from blood and allow the high throughput screening of clinical samples. 
Here, we present a fast, efficient and reliable multi-fractionation system based on mesoporous silica chips to specifically target and enrich LMWP.10,11 Mesoporous silica (MPS) thin films with tunable features at the nanoscale were fabricated using the triblock copolymer template pathway. Using different polymer templates and polymer concentrations in the precursor solution, various pore size distributions, pore structures, connectivity and surface properties were determined and applied for selective recovery of low mass proteins. The selective parsing of the enriched peptides into different subclasses according to their physicochemical properties will enhance the efficiency of recovery and detection of low abundance species. In combination with mass spectrometry and statistic analysis, we demonstrated the correlation between the nanophase characteristics of the mesoporous silica thin films and the specificity and efficacy of low mass proteome harvesting. The results presented herein reveal the potential of the nanotechnology-based technology to provide a powerful alternative to conventional methods for LMWP harvesting from complex biological fluids. Because of the ability to tune the material properties, the capability for low-cost production, the simplicity and rapidity of sample collection, and the greatly reduced sample requirements for analysis, this novel nanotechnology will substantially impact the field of proteomic biomarker research and clinical proteomic assessment.

We developed a technology based on mesoporous silica thin film for the selective recovery of low molecular weight proteins and peptides from human serum. The physico-chemical properties of our mesoporous chips were finely tuned to provide substantial control in peptide enrichment and consequently profile the serum proteome for diagnostic purposes.

De bajo peso molecular de proteínas en el enriquecimiento de las películas delgadas de silicio mesoporosos para el descubrimiento de biomarcadores

The identification of circulating biomarkers holds great potential for non invasive approaches in early diagnosis and prognosis, as well as for the ...

The Synthesis of RGD-functionalized Hydrogels as a Tool for Therapeutic Applications

The use of polymers as biomaterials has provided significant advantages in therapeutic applications. In particular, the possibility to modify and functionalize polymer chains with compounds that are able to improve biocompatibility, mechanical properties, or cell viability allows the design of novel materials to meet new challenges in the biomedical field. With the polymer functionalization strategies, click chemistry is a powerful tool to improve cell-compatibility and drug delivery properties of polymeric devices. Similarly, the fundamental need of biomedicine to use sterile tools to avoid potential adverse-side effects, such as toxicity or contamination of the biological environment, gives rise to increasing interest in the microwave-assisted strategy.
The combination of click chemistry and the microwave-assisted method is suitable to produce biocompatible hydrogels with desired functionalities and improved performances in biomedical applications. This work aims to synthesize RGD-functionalized hydrogels. RGD (arginylglycylaspartic acid) is a tripeptide that can mimic cell adhesion proteins and bind to cell-surface receptors, creating a hospitable microenvironment for cells within the 3D polymeric network of the hydrogels. RGD functionalization occurs through Huisgen 1,3-dipolar cycloaddition. Some PAA carboxyl groups are modified with an alkyne moiety, whereas RGD is functionalized with azido acid as the terminal residue of the peptide sequence. Finally, both products are used in a copper catalyzed click reaction to permanently link the peptide to PAA. This modified polymer is used with carbomer, agarose and polyethylene glycol (PEG) to synthesize a hydrogel matrix. The 3D structure is formed due to an esterification reaction involving carboxyl groups from PAA and carbomer and hydroxyl groups from agarose and PEG through microwave-assisted polycondensation. The efficiency of the gelation mechanism ensures a high degree of RGD functionalization. In addition, the procedure to load therapeutic compounds or biological tools within this functionalized network is very simple and reproducible.

We present a protocol for the synthesis of RGD-functionalized hydrogels as devices for cell and drug delivery. The procedure involves copper catalyzed alkyne-azide cycloaddition (CuAAC) between alkyne-modified polyacrylic acid (PAA) and a RGD-azide derivative. The hydrogels are formed using microwave-assisted polycondensation and their physicochemical properties are investigated.

La síntesis de hidrogeles funcionalizado-RGD como una herramienta para aplicaciones terapéuticas

The use of polymers as biomaterials has provided significant advantages in therapeutic applications. In particular, the possibility to modify and ...

Light-mediated Formation and Patterning of Hydrogels for Cell Culture Applications

Click chemistries have been investigated for use in numerous biomaterials applications, including drug delivery, tissue engineering, and cell culture. In particular, light-mediated click reactions, such as photoinitiated thiol&#8722;ene and thiol&#8722;yne reactions, afford spatiotemporal control over material properties and allow the design of systems with a high degree of user-directed property control. Fabrication and modification of hydrogel-based biomaterials using the precision afforded by light and the versatility offered by these thiol&#8722;X photoclick chemistries are of growing interest, particularly for the culture of cells within well-defined, biomimetic microenvironments. Here, we describe methods for the photoencapsulation of cells and subsequent photopatterning of biochemical cues within hydrogel matrices using versatile and modular building blocks polymerized by a thiol&#8722;ene photoclick reaction. Specifically, an approach is presented for constructing hydrogels from allyloxycarbonyl (Alloc)-functionalized peptide crosslinks and pendant peptide moieties and thiol-functionalized poly(ethylene glycol) (PEG) that rapidly polymerize in the presence of lithium acylphosphinate photoinitiator and cytocompatible doses of long wavelength ultraviolet (UV) light. Facile techniques to visualize photopatterning and quantify the concentration of peptides added are described. Additionally, methods are established for encapsulating cells, specifically human mesenchymal stem cells, and determining their viability and activity. While the formation and initial patterning of thiol-alloc hydrogels are shown here, these techniques broadly may be applied to a number of other light and radical-initiated material systems (e.g., thiol-norbornene, thiol-acrylate) to generate patterned substrates.

We describe a sequential process for light-mediated formation and subsequent biochemical patterning of synthetic hydrogel matrices for three-dimensional cell culture applications. The construction and modification of hydrogels with cytocompatible photoclick chemistry is demonstrated. Additionally, facile techniques to quantify and observe patterns and determine cell viability within these hydrogels are presented.

Formación luz mediada y el patrón de hidrogeles para aplicaciones de cultivo celular

Click chemistries have been investigated for use in numerous biomaterials applications, including drug delivery, tissue engineering, and cell culture. In ...

Synthesis of Hydrogels with Antifouling Properties As Membranes for Water Purification

Hydrogels have been widely utilized to enhance the surface hydrophilicity of membranes for water purification, increasing the antifouling properties and thus achieving stable water permeability through membranes over time. Here, we report a facile method to prepare hydrogels based on zwitterions for membrane applications. Freestanding films can be prepared from sulfobetaine methacrylate (SBMA) with a crosslinker of poly(ethylene glycol) diacrylate (PEGDA) via photopolymerization. The hydrogels can also be prepared by impregnation into hydrophobic porous supports to enhance the mechanical strength. These films can be characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to determine the degree of conversion of the (meth)acrylate groups, using goniometers for hydrophilicity and differential scanning calorimetry (DSC) for polymer chain dynamics. We also report protocols to determine the water permeability in dead-end filtration systems and the effect of foulants (bovine serum albumin, BSA) on membrane performance.

This paper reports practical methods to prepare hydrogels in freestanding films and impregnated membranes and to characterize their physical properties, including water transport properties.

Síntesis de hidrogeles con propiedades antiincrustantes como membranas de purificación de agua

Hydrogels have been widely utilized to enhance the surface hydrophilicity of membranes for water purification, increasing the antifouling properties and ...

Production of Elastin-like Protein Hydrogels for Encapsulation and Immunostaining of Cells in 3D

Two-dimensional (2D) tissue culture techniques have been essential for our understanding of fundamental cell biology. However, traditional 2D tissue culture systems lack a three-dimensional (3D) matrix, resulting in a significant disconnect between results collected in vitro and in vivo. To address this limitation, researchers have engineered 3D hydrogel tissue culture platforms that can mimic the biochemical and biophysical properties of the in vivo cell microenvironment. This research has motivated the need to develop material platforms that support 3D cell encapsulation and downstream biochemical assays. Recombinant protein engineering offers a unique toolset for 3D hydrogel material design and development by allowing for the specific control of protein sequence and therefore, by extension, the potential mechanical and biochemical properties of the resultant matrix. Here, we present a protocol for the expression of recombinantly-derived elastin-like protein (ELP), which can be used to form hydrogels with independently tunable mechanical properties and cell-adhesive ligand concentration. We further present a methodology for cell encapsulation within ELP hydrogels and subsequent immunofluorescent staining of embedded cells for downstream analysis and quantification.

Recombinant protein-engineered hydrogels are advantageous for 3D cell culture as they allow for complete tunability of the polymer backbone and therefore, the cell microenvironment. Here, we describe the process of recombinant elastin-like protein purification and its application in 3D hydrogel cell encapsulation.

Producción de la proteína elastina como hidrogeles para encapsulación y el Immunostaining de células en 3D

Two-dimensional (2D) tissue culture techniques have been essential for our understanding of fundamental cell biology. However, traditional 2D tissue ...

Measuring Global Cellular Matrix Metalloproteinase and Metabolic Activity in 3D Hydrogels

Three-dimensional (3D) cell culture systems often more closely recapitulate in vivo cellular responses and functions than traditional two-dimensional (2D) culture systems. However, measurement of cell function in 3D culture is often more challenging. Many biological assays require retrieval of cellular material which can be difficult in 3D cultures. One way to address this challenge is to develop new materials that enable measurement of cell function within the material. Here, a method is presented for measurement of cellular matrix metalloproteinase (MMP) activity in 3D hydrogels in a 96-well format. In this system, a poly(ethylene glycol) (PEG) hydrogel is functionalized with a fluorogenic MMP cleavable sensor. Cellular MMP activity is proportional to fluorescence intensity and can be measured with a standard microplate reader. Miniaturization of this assay to a 96-well format reduced the time required for experimental set up by 50% and reagent usage by 80% per condition as compared to the previous 24-well version of the assay. This assay is also compatible with other measurements of cellular function. For example, a metabolic activity assay is demonstrated here, which can be conducted simultaneously with MMP activity measurements within the same hydrogel. The assay is demonstrated with human melanoma cells encapsulated across a range of cell seeding densities to determine the appropriate encapsulation density for the working range of the assay. After 24 h of cell encapsulation, MMP and metabolic activity readouts were proportional to cell seeding density. While the assay is demonstrated here with one fluorogenic degradable substrate, the assay and methodology could be adapted for a wide variety of hydrogel systems and other fluorescent sensors. Such an assay provides a practical, efficient and easily accessible 3D culturing platform for a wide variety of applications.

Here, a protocol is presented for encapsulating and culturing cells in poly(ethylene glycol) (PEG) hydrogels functionalized with a fluorogenic matrix metalloproteinase (MMP)-degradable peptide. Cellular MMP and metabolic activity are measured directly from the hydrogel cultures using a standard microplate reader.

Medición de metaloproteinasa de la matriz celular Global y actividad metabólica en hidrogeles 3D

Three-dimensional (3D) cell culture systems often more closely recapitulate in vivo cellular responses and functions than traditional two-dimensional (2D) ...

A Lab-On-A-Chip Platform for Stimulating Osteocyte Mechanotransduction and Analyzing Functional Outcomes of Bone Remodeling

Bone remodeling is a tightly regulated process that is required for skeletal growth and repair as well as adapting to changes in the mechanical environment. During this process, mechanosensitive osteocytes regulate the opposing responses between the catabolic osteoclasts and anabolic osteoblasts. To better understand the highly intricate signaling pathways that regulate this process, our lab has developed a foundationary lab-on-a-chip (LOC) platform for analyzing functional outcomes (formation and resorption) of bone remodeling within a small scale system. As bone remodeling is a lengthy process that occurs on the order of weeks to months, we developed long-term cell culturing protocols within the system. Osteoblasts and osteoclasts were grown on functional activity substrates within the LOC and maintained for up to seven weeks. Afterward, chips were disassembled to allow for the quantification of bone formation and resorption. Additionally, we have designed a 3D printed mechanical loading device that pairs with the LOC platform and can be used to induce osteocyte mechanotransduction by deforming the cellular matrix. We have optimized cell culturing protocols for osteocytes, osteoblasts, and osteoclasts within the LOC platform and have addressed concerns of sterility and cytotoxicity. Here, we present the protocols for fabricating and sterilizing the LOC, seeding cells on functional substrates, inducing mechanical load, and disassembling the LOC to quantify endpoint results. We believe that these techniques lay the groundwork for developing a true organ-on-a-chip for bone remodeling.

Here, we present protocols for analyzing bone remodeling within a lab-on-a-chip platform. A 3D printed mechanical loading device can be paired with the platform to induce osteocyte mechanostransduction by deforming the cellular matrix. The platform can also be used to quantify bone remodeling functional outcomes from osteoclasts and osteoblasts (resorption/formation).

Una plataforma Lab-On-A-Chip para estimular la reconversión de mecanonoducción de osteocitos y analizar los resultados funcionales de la remodelación ósea

Bone remodeling is a tightly regulated process that is required for skeletal growth and repair as well as adapting to changes in the mechanical ...

Controlled Strain of 3D Hydrogels under Live Microscopy Imaging

External forces are an important factor in tissue formation, development, and maintenance. The effects of these forces are often studied using specialized in vitro stretching methods. Various available systems use 2D substrate-based stretchers, while the accessibility of 3D techniques to strain soft hydrogels, is more restricted. Here, we describe a method that allows external stretching of soft hydrogels from their circumference, using an elastic silicone strip as the sample carrier. The stretching system utilized in this protocol is constructed from 3D-printed parts and low-cost electronics, making it simple and easy to replicate in other labs. The experimental process begins with polymerizing thick (&#62;100 &#956;m) soft fibrin hydrogels (Elastic Modulus of ~100 Pa) in a cut-out at the center of a silicone strip. Silicone-gel constructs are then attached to the printed-stretching device and placed on the confocal microscope stage. Under live microscopy the stretching device is activated, and the gels are imaged at various stretch magnitudes. Image processing is then used to quantify the resulting gel deformations, demonstrating relatively homogenous strains and fiber alignment throughout the gel&#8217;s 3D thickness (Z-axis). Advantages of this method include the ability to strain extremely soft hydrogels in 3D while executing in situ microscopy, and the freedom to manipulate the geometry and size of the sample according to the user&#8217;s needs. Additionally, with proper adaptation, this method can be used to stretch other types of hydrogels (e.g., collagen, polyacrylamide or polyethylene glycol) and can allow for analysis of cells and tissue response to external forces under more biomimetic 3D conditions.

The presented method involves uniaxial stretching of 3D soft hydrogels embedded in silicone rubber while allowing live confocal microscopy. Characterization of the external and internal hydrogel strains as well as fiber alignment are demonstrated. The device and protocol developed can assess the response of cells to various strain regimes.

Cepa controlada de hidrogeles 3D bajo imágenes de microscopía en vivo

External forces are an important factor in tissue formation, development, and maintenance. The effects of these forces are often studied using specialized ...