Este proyecto fue apoyado por el graduado estudiante de estudio al exterior programa (NSC-101-2917-I-007-010); el programa de Ingeniería Biomédica (NSC-101-2221-E-007-032-MY3); y el programa nacional de nanotecnología (NSC-101-2120-M-007-001-), Consejo Nacional de ciencia de R.O.C., Taiwán. Los autores desean agradecer a Prof. Ali Khademhosseini, Gulden Camci-Unal, Arghya Paul y Ronglih Liao en Harvard Medical School para compartir la tecnología de encapsulación de hidrogel y de la célula.

1. GelMA Synthesis
<ol>
	<li>Weigh 10 g of gelatin powder and add it to a glass flask with 100 mL ofDulbecco&#39;s phosphate-buffered saline (DPBS). Put a magnetic stir bar into the flask and place the flask on a stirring hot plate.</li>
	<li>Cover the flask with aluminum foil to avoid water evaporation. Set the hot plate temperature to 50-60 &#176;C and the stirrer at 100 rpm for 1 h to dissolve the gelatin powder well.</li>
	<li>After the gelatin has dissolved, add 8 mL of methacrylic anhydride very slowly (one drop per second) using a pipette. Let it react at 60 &#176;C for 3 h.</li>
	<li>Add pre-warmed DPBS (40 &#176;C) to the flask to a final volume of 500 mL and allow this mix well for 15 min to stop the reaction.</li>
	<li>Meanwhile, cut a dialysis membrane (14 kDa cut-off molecular weight) into several 25 cm-long tubes. Immerse them in deionized (DI) water for 15 min and make a knot to close one end of the dialysis tubes.</li>
	<li>Load the appropriate amount (30 - 60 mL) of the polymer solution into the dialysis tubes and close the other end. Place them in a 5-L plastic beaker with DI water for a week. Renew the DI water twice a day and maintain the solution at 40 - 50 &#176;C during the dialysis process.</li>
	<li>Collect the solution from the tube in a 500-mL glass bottle. Pour ~450 - 500 mL of solution in a 500-mL filter cup (pore size of 0.22 &#181;m) and apply a vacuum to the filter cup to force the solution to pass through the filter membrane for sterilization.</li>
	<li>Transfer the sterilized polymer into several 50-mL sterilized tubes and store them in a -80 &#176;C freezer for 3 - 5 days.</li>
	<li>Freeze-dry the -80 &#176;C polymer for 1 week using a freeze dryer to form GelMA. Store the GelMA in a -80 &#176;C freezer.</li>
</ol>
2. 3-(Trimethoxysilyl)propyl Methacrylate (TMSPMA) Modification
<ol>
	<li>&#160;Cut commercial glass slides into two small pieces (25 mm x 37.5 mm) and immerse them in 0.5 M NaOH solution for 4 h. Wash the slides with a large amount of DI water.</li>
	<li>Place the slide on a rack inside a glass container with 95% ethanol and clean using an ultrasonicator at 43 kHz for 15 min. Air dry the glass slide.</li>
	<li>Immerse the glass slides in 5% TMSPMA in 99.5% ethanol for 1 h.</li>
	<li>Wash the slides in 95% ethanol, air dry the slides, and anneal the TMSPMA coating in an oven at 80 &#176;C for 2 h.</li>
</ol>
3. Chip Fabrication
<ol>
	<li>Take one 2 mm- and one 0.3 mm-thick polymethylmethacrylate (PMMA) plate, apply double-sided tape to one side of the PMMA surface, and release the liner on one side. Leave two 2 mm-thick PMMA plates and one 1 mm-thick plate without double-sided tape.</li>
	<li>Laser-cut a 2 mm-thick PMMA plate without double-sided tape to 42 mm x 30 mm to make the bottom plate. Cut a 2 mm-thick PMMA plate with double-sided tape to make the boundary frame, with outer dimensions of 42 mm x 30 mm and inner dimensions of 37.5 mm x 25 mm.</li>
	<li>Laser-cut the 0.3 mm-thick PMMA plate with double-sided tape into a 12-mm center circle with two 2 mm-wide and 8 mm-long flow channels on opposite sides of the circle (Figure 1a).</li>
	<li>To prepare the PMMA mold for casting the PDMS cover, assemble the three pieces of PMMA components from steps 3.2-3.3 (Figure 1b) using double-sided tape.</li>
	<li>Laser-cut a 2 mm-thick PMMA plate with double-sided tape into a 5 cm x 5 cm piece with a 3 x 3 array of 8.5 mm x 8.5 mm hollow rectangles. Cut another 5 cm x 5 cm piece with a 3 x 3 array of 4-mm hollow circles. Laser-cut a 1 mm-thick PMMA plate without double-sided tape into a 5 cm x 5 cm PMMA bottom plate.</li>
	<li>Prepare the PMMA mold for casting the PDMS plug by assembling the three pieces of PMMA components from step 3.5 (Figure 1c) using double-sided tape.</li>
	<li>Prepare the PDMS cover and PDMS plug by properly mixing 30 g of PDMS elastomer and 3 g of PDMS curing agent; degas the mixture under a vacuum chamber for 1 h.</li>
	<li>Cast 1.8-2.0 g of the mixture into the PMMA mold for the PDMS cover and use the appropriate amount to fill each cavity of the PMMA mold for the PDMS plug. Cast 10 g of uncured PDMS mixture in a blank 10-cm plastic plate. Put these molds in a vacuum chamber to degas for 30 min.</li>
	<li>Cure the PDMS for 2 h at 80 &#176;C. After cooling down the cured PDMS on the mold, detach the PDMS covers and the PDMS plugs from the PMMA molds.</li>
	<li>Punch two holes with diameters of about 3 mm at the ends of flow channels of the PDMS covers.</li>
	<li>Cut the PDMS sheet molded from the 10-cm plastic plate into many 1 cm x 1 cm cubes and punch a 3-mm hole in each PDMS cube. Glue two uncured 1 cm x 1 cm PDMS cubes onto the openings of the PDMS cover (to serve as medium reservoirs and to aid in the curing process of the gradient circular hydrogel patterns) and cure for 1 h at 80 &#176;C.</li>
	<li>Bond the PDMS covers with the two PDMS reservoirs onto a TMSPMA-coated slide by pre-treating the bonding side of the PDMS cover and the TMSPMA-coated slide under an oxygen plasma machine (30 W RF power (high mode) and 600 mTorr compressed air) or a high-frequency electronic corona generator (115 V, 50/60 Hz, 0.35 A) for 90 s of O2 plasma treatment.</li>
	<li>Contact the plasma-treated surface of the PDMS covers and the TMSPMA slide and press them closely for permanent bonding through the formation of an Si-O-Si bond. 
	NOTE: Placing the chip in an oven at 80 &#176;C for 1 h can further enhance the bonding strength.</li>
	<li>After cooling, immerse the chips in 95% ethanol for 15 min and air dry. Then, sterilize the chips under UV irradiation for 1 h and store them in a box wrapped in aluminum foil in the laminar hood.</li>
</ol>
4. Static Gradient Strain on the Cell-laden Hydrogel
<ol>
	<li>Print and cut a piece of photomask, 25 mm x 37.5 mm in size, by printing the layout in Figure 2b on a transparent film. Adjust the printed size of Figure 2b to match the dimension in Figure 2a.</li>
	<li>Prepare 100 mL of DMEM medium with 10% FBS, 1% Pen-Strep, and 250 mL of DPBS in a 37 &#176;C water bath to use as the cell culture medium.</li>
	<li>Weigh 25 mg of freeze-dried GelMA into 0.3 mL of prewarmed (37 &#176;C) cell culture medium in a 1.5-mL black microcentrifuge tube. Put the microcentrifuge tube on a laboratory stirrer/hot plate until the GelMA dissolves in the medium.</li>
	<li>Weigh 50 mg of photoinitiator into 1 ml of DPBS in a microcentrifuge tube and place it in an 80 &#176;C oven for 15 min or until the photoinitiator has dissolved.</li>
	<li>Take 25 &#181;L of the 10% photoinitiator from step 4.4 and add it to the microcentrifuge tube from step 4.3. Pipette several times to mix well.</li>
	<li>Count 3 x 106 NIH 3T3 cells using an automated cell counter. Centrifuge the suspension at 200 x g for 5 min, discard the supernatant, and re-suspend the cells in 175 &#181;L of cell culture medium.</li>
	<li>Add the cell solution from step 4.6 to the microcentrifuge tube from step 4.5 to get a prepolymer cell solution of 5% GelMA, 0.5% photoinitiator, and ~6 x 106 3T3 cells/mL. After mixing, load 100 &#181;L of cell prepolymer in a 100-&#181;L micro syringe.</li>
	<li>Manually align (see Figure 3a) a piece of the photomask onto the bottom slide of the sterilized gradient strain chip and simply fix the position using a small drop of DI water in between. Connect the 100-&#181;L micro-syringe loaded with prepolymer cell solution to the inlet of the chip.</li>
	<li>Place (see Figure 3b) 50 &#181;L of prepolymer cell solution in the flow channel using the micro-syringe and then plug the outlet using a PDMS plug. Inject an extra 40 &#181;L of solution to create a convex bulge in the circular PDMS membrane.</li>
	<li>Move the chip with the photomask (bottom), micro-syringe (inlet), and PDMS plug (outlet) from step 4.9 under a UV lamp (365 nm, 9 mW/cm2) and expose it for 30 - 45 s to crosslink the concentric circular hydrogel in the fluidic chamber.</li>
	<li>Remove the PDMS plug and the micro-syringe to release the liquid pressure (see Figure 3c). Use a 1-mL syringe loaded with prewarmed DPBS to wash out uncrosslinked resins 3 times by flushing from the inlet to the outlet.</li>
	<li>Fill the flow channel with about 100 &#181;L of cell culture medium.</li>
	<li>Place the chip in a sterilized culture dish and culture in a 5% CO2 atmosphere at 37 &#176;C for a week. Refresh the medium every day.</li>
	<li>Take images of three chips on day 0 after 4 h of incubation, as a control group, and three chips on day 3, as the experimental set, using a microscope with a 20X objective. Measure the line width of each hydrogel from line 1 to line 12 using software (e.g., ImageJ) to calculate the compress strains ( Figure 4). 
	NOTE: The elongation percentage is calculated by dividing the value of the line width difference between 40 &#181;L and 0 &#181;L by the line width at 40 &#181;L.</li>
</ol>
5. Cell Staining for Alignment Analysis
<ol>
	<li>Use a syringe to inject 4% paraformaldehyde (PFA) in DPBS at RT into the flow chip for 15 min for the fixation of the cell-laden hydrogel. 
	NOTE: Caution. PFA is toxic and should be handled with care.</li>
	<li>Replace the solution with 0.5% cell membrane permeating solution in DPBS for 10 min to permeabilize the cell membrane at RT.</li>
	<li>PBS wash the samples 3 times with 5- to 10-min interval between washes (using a loaded syringe, as in step 5.1).</li>
	<li>Load 1% BSA solution into the fluidic channel for 45-60 min at RT (using a loaded syringe through the inlet port).</li>
	<li>Add 1.5 mL of methanol into the vial with Alexa Fluor 488 phalloidin to yield a final concentration of 6.6 &#181;M stock solution.</li>
	<li>Take 5 &#181;L of Alexa Fluor 488 phalloidin from step 5.5 and dilute it in 200 &#181;L of DPBS with 0.1% BSA to form a final concentration of 0.165 &#181;M Alexa Fluor 488 phalloidin.</li>
	<li>Add 200 &#181;L of the mixture solution to the fluidic channel using a micropipette and incubate the chip at 37 &#176;C for 45 - 60 min for actin staining. PBS wash (as above) the samples 3 times.</li>
	<li>Prepare 1 &#181;g/mL DAPI in PBS, flow it through the chip, and stain cell nuclei at 37 &#176;C for 5 min.</li>
	<li>Pipette DPBS into the fluidic channel to wash out the staining solution and refill the fluidic chamber with PBS solution to take images with a fluorescence microscope.</li>
	<li>Capture the fluorescent images of the 3T3 cells in the hydrogels using an inverted fluorescence microscope under 40X magnification with a CCD detector and filter sets of ex/em at 488/520 nm and 358/461 nm for Alexa Fluor 488 phalloidin (actin) and DAPI (nucleus), respectively.</li>
</ol>

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Los autores no tienen nada que revelar.

En este papel, Divulgamos sobre un enfoque simple para comparar comportamiento de alineación de celda después de hidrogel forma orientación y tramo extensible. Una membrana PDMS flexible crea una curvatura en forma de cúpula para generar diferentes alturas de hidrogeles circulares concéntricos. Después de soltar la presión, la membrana PDMS automáticamente aplica fuerza a los hidrogeles micro-patrón para formar el gradiente tensión/alargamiento, con un máximo en el centro y un mínimo en el límite exterior. Como la formación de la cepa gradiente está diseñada por la flexible membrana PDMS y la manipulación de la viruta fluídica, hay varios parámetros importantes que deben ser atendidos: membrana (i) un control preciso del grosor de los PDMS es crucial para ajustar el valor del gradiente de tensión. Si la membrana es demasiado gruesa, incluso el volumen de inyección máxima de prepolímero de celular no será capaz de generar una adecuada curva convexa en la membrana PDMS para la reticulación de altura gradiente de hidrogeles cargados de celular. Por el contrario, una muy delgada membrana PDMS puede aplicar suficiente fuerza a los hidrogeles. Compruebe que el peso de PDMS no curada en el molde de la cubierta PDMS es alrededor de 1.6-2.0 g por chip. (ii) prevención de la contaminación es muy importante durante el manejo de la reticulación del hidrogel celulares cargados en el chip fluídico. Antes de la célula de cultivo en la incubadora, bien lavado con PBS esterilizada en el canal fluídico y utilizando el 75% etanol para limpiar la superficie de la viruta puede ayudar a evitar el problema de la contaminación. (iii) la concentración de fotoiniciador y la dosis de exposición Ultravioleta deben ser cuidadosamente controlada y en la gama de ~0.1% - 2% (0.5% se recomienda). Reticulación en el hidrogel y la sobredosificación de la irradiación UV resultará en viabilidad celular baja. (iv) el ancho de línea del hidrogel con motivos no debe ser demasiado grande. De lo contrario, la tasa de reemplazo de nutrientes en los hidrogeles gruesas no será capaz de apoyar la proliferación celular. Por lo general, se recomienda menos de 300 μm. Se puede variar el espacio entre dos círculos de hidrogel, y se recomienda un ciclo de deber del 50%. (v) mientras que lavar o volver a llenar el canal de flujo con la solución, debe evitarse la formación de burbujas. Pipeteando suavemente la solución en el chip puede ayudar a quitar las burbujas.
El concepto de cepa gradiente generado por la curvatura deformación de PDMS puede actualizarse más a la aplicación de cepas gradiente dinámicas y puede ser integrado con el estímulo bioquímico, que puede beneficiar a muchos estudios sobre la regeneración de tejido funcional. El módulo de inyección fluídica simple con un enchufe de PDMS puede reemplazarse por cualquier sistema neumático avanzado para extendido control experimental. El molde PMMA también puede ser sustituido por un molde recientemente SU-8 o un molde del silicio a granel-grabado al agua fuerte.
Este chip de gradiente de tensión con un hidrogel circular cargados de celular puede generar estática fuerza de compresión sobre el hidrogel 3D sin máquinas mecánicas o eléctricas externas. Por lo tanto, proporciona una plataforma de cribado rápido para investigar comportamientos de la célula en una serie de condiciones de tensión, sin el riesgo de problemas de contaminación causados por la operación de máquinas externas. Sin embargo, estimulación de tensión controlada por el tiempo no es factible porque la membrana PDMS genera cepas hasta la degradación de la hidrogel.

Servir como un material del bloque que imita un microambiente nativo, un hidrogel que contiene la matriz extracelular (ECM) puede reconstruir biomiméticos tejido andamios para apoyar el crecimiento de la célula. Poseer las funciones de un tejido, alineación de celda organizado es un requisito esencial. Varios 2D (es decir, las células cultivadas en una superficie) y 3D (es decir, las células encapsuladas en un hidrogel) alineaciones de celda se han obtenido por cultivo o encapsular las células o en substratos flexibles con micro- o nano-patrones1. Alineación 3D celular en microarquitectura es más atractiva, como el microambiente está más cercano del tejido propio constructo2,3,4. Un enfoque común para la alineación celular 3D es la localización geométrica de hidrogel forma2,3. Debido al espacio restringido para la proliferación celular en la dirección de eje corto, células objetivo alinear a lo largo de la dirección de eje largo en un hidrogel de micro-patrón. Otro enfoque es aplicar stretch extensible a los hidrogeles para lograr alineación de celdas paralela a la dirección de estiramiento4,5.
Estimulación biofísica en hidrogeles de ECM, como la tensión compresiva o un campo eléctrico, puede regular funciones celulares para la integración adecuada del tejido, proliferación y diferenciación1,2,3. Mucha investigación se ha realizado para investigar el comportamiento celular mediante la aplicación de una condición de tensión a la vez utilizando múltiples control mecánico unidades4,6,7,8,9. Por ejemplo, el uso de motores paso a paso mecánica apretado o estirado en un hidrogel de colágeno de células encapsuladas 3D ha sido un común enfoque7,10. Sin embargo, dicho equipo de control requiere un espacio extra y enfrenta el problema de la contaminación en la incubadora9,7,11,12. Además, el instrumento grande no puede dar un ambiente de control preciso para proporcionar alta reproducibilidad13.
Teniendo en cuenta que hidrogeles cargados de celular se emplean generalmente en la escala micro para aplicaciones biomédicas, es ventajoso combinar técnicas de MEMS para generar un rango de tensión/estiramiento del estímulo a investigar simultáneamente el comportamiento celular en 3D biomiméticos construcciones en vitro2,14,15,16,17,18. Por ejemplo, usando la presión del gas a deformar la membrana PDMS en chips de microfluídica puede dar lugar a varias cepas, conduce la diferenciación celular a diferentes linajes9,16. Sin embargo, hay muchos desafíos técnicos, tales como procesos de fabricación de chips complicados en un cuarto limpio y la integración de software control de motores, bombas, válvulas y gases comprimidos.
En este trabajo, demostramos un enfoque simple para obtener un chip de microfluidos gradiente de tensión estática autosostenible mediante el empleo de un patrón de hidrogel circulares concéntricos y una membrana flexible de PDMS. A diferencia de la mayoría de los enfoques existentes, nuestra plataforma es un dispositivo miniatura portátil y desechable que puede ser fabricado fuera de un salón amarillo y que posee uno mismo-generar tensiones degradadas concéntricos hidrogeles encapsulado en celular, sin equipos mecánicos externos durante la incubación. Comportamientos de células de fibroblastos 3T3 influenciado por una combinación de forma de hidrogel y una variedad de señales de orientación elástico resistencia a la tracción fueron demostrados durante la observación de la alineación celular dentro de entornos 3D ECM-mimético en el chip de gradiente de presión durante 3 días.

<table border="0" cellpadding="0" cellspacing="0" width="1383">
	<tbody>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">1.5-mL black microcentrifuge tube</td>
			<td style="width:225px;">Argos Technologies&#160;</td>
			<td style="width:156px;">03-391-161</td>
			<td style="width:665px;">This one can be replaced with a neutral color of 1.5-mL tube covered with aluminun foil</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">10X DPBS</td>
			<td style="width:225px;">Sigma-Aldrich</td>
			<td style="width:156px;">56064C</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Alexa Fluor 488 phalloidin&#160;</td>
			<td style="width:225px;">Invitrogen</td>
			<td style="width:156px;">A12379&#160;</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">BSA</td>
			<td style="width:225px;">Sigma</td>
			<td style="width:156px;">A1595</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Calcein</td>
			<td style="width:225px;">Molecular Probe</td>
			<td style="width:156px;">C1430</td>
			<td style="width:665px;">For labeling viable cells</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">CCD</td>
			<td style="width:225px;">PCO. Imaging</td>
			<td style="width:156px;">Pixelfly qe</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Cell membrane permeating solution</td>
			<td style="width:225px;">Sigma-Aldrich</td>
			<td style="width:156px;">X100</td>
			<td style="width:665px;">0.5% Triton X-100 for permeating cell membrane</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">DAPI</td>
			<td style="width:225px;">Sigma-Aldrich</td>
			<td style="width:156px;">D8417</td>
			<td style="width:665px;">Cell nucleus staining</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Dialysis membrane</td>
			<td style="width:225px;">Sigma-Aldrich</td>
			<td style="width:156px;">D9527</td>
			<td style="width:665px;">Molecular weight cut-off = 14,000</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">DMEM</td>
			<td style="width:225px;">Gibco</td>
			<td style="width:156px;">11995-065</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Double-side tape</td>
			<td style="width:225px;">3M</td>
			<td style="width:156px;">8003</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">FBS</td>
			<td style="width:225px;">Hyclone</td>
			<td style="width:156px;">SH30071.03</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Gelatin</td>
			<td style="width:225px;">Sigma-Aldrich</td>
			<td style="width:156px;">G2500</td>
			<td style="width:665px;">gel strength 300, type A, from porcine skin</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">High frequency electronic corona generator</td>
			<td style="width:225px;">Electro-technic products</td>
			<td style="width:156px;">MODEL BD-20</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Methacrylic Anhydride</td>
			<td style="width:225px;">Sigma-Aldrich</td>
			<td style="width:156px;">276685</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Micro syringe</td>
			<td style="width:225px;">Hamilton</td>
			<td style="width:156px;">80501</td>
			<td style="width:665px;">50 &#956;L&#160;</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Microscope</td>
			<td style="width:225px;">Olympus</td>
			<td style="width:156px;">IX71</td>
			<td style="width:665px;">Include two filter sets: LF405/LP-B-000 and LF488/LP-C-000 from Semrock</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Oxygen plasma machine</td>
			<td style="width:225px;">Harrick plasma</td>
			<td style="width:156px;">PDC-001</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Paraformaldehyde</td>
			<td style="width:225px;">Sigma-Aldrich</td>
			<td style="width:156px;">P6148</td>
			<td style="width:665px;">For fixing cell</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">PDMS</td>
			<td style="width:225px;">DOW CORNING</td>
			<td style="width:156px;">Sylgard 184</td>
			<td style="width:665px;">Mixture for PDMS chip cast-molding fabrication</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Pen-Strep</td>
			<td style="width:225px;">Gibco</td>
			<td style="width:156px;">10378-016</td>
			<td style="width:665px;">penicillin/streptomycin</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Photoinitiator</td>
			<td style="width:225px;">CIBA</td>
			<td style="width:156px;">Irgacure 2959</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Propidium iodide</td>
			<td style="width:225px;">Sigma-Aldrich</td>
			<td style="width:156px;">P4170</td>
			<td style="width:665px;">For labeling dead cells</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Sterile Filtration cup</td>
			<td style="width:225px;">Millipore</td>
			<td style="width:156px;">SCGPT05RE</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">TMSPMA</td>
			<td style="width:225px;">Sigma-Aldrich</td>
			<td style="width:156px;">440159</td>
			<td style="width:665px;">For hydrogel immobilization</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Ultrasonicator</td>
			<td style="width:225px;">Delta</td>
			<td style="width:156px;">D150H</td>
			<td style="width:665px;">150W, 43kHz</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">UV light</td>
			<td style="width:225px;">DAIHAN</td>
			<td style="width:156px;">WUV-L10</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">Freeze Dryer</td>
			<td style="width:225px;">FIRSTEK</td>
			<td style="width:156px;">150311025</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">NIH3T3(fibroblast)</td>
			<td style="width:225px;">Food Industry Research and Development Institute(FIRDI)</td>
			<td style="width:156px;">08C0011</td>
			<td style="width:665px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:337px;">MOXI Z Mini Automated Cell Counter</td>
			<td style="width:225px;">ORFLO</td>
			<td style="width:156px;">MXZ001</td>
			<td style="width:665px;"></td>
		</tr>
	</tbody>
</table>

gradient strain chip for stimulating cellular behaviors in cell-laden hydrogel

Orientación artificial para alineación celular es un tema candente en el campo de la ingeniería de tejidos. La mayoría de la investigación anterior ha investigado solo alineación celular inducida por la cepa en un hidrogel cargadas de célula mediante complejos procesos experimentales y sistemas de control de masas, que se asocian generalmente a problemas de contaminación. Así, en este artículo, proponemos un enfoque simple para construir una gradiente tensión estática usando un chip neumático con una cubierta plástica de PDMS y un sustrato de vidrio transparente UV para la estimulación del comportamiento celular en un hidrogel 3D. Prepolímero de células foto-patternable sobrecarga en la cámara de neumático puede generar una membrana PDMS curva convexa en la cubierta. Después de la reticulación UV, a través de un micropattern circular concéntrica bajo la membrana PDMS curvada y tampón de lavado, un microambiente para la investigación de la célula comportamientos bajo una variedad de cepas degradadas es uno establecido en un único chip fluídico, sin instrumentos externos. Células NIH3T3 fueron demostradas después de observar el cambio en la tendencia de alineación celular bajo dirección de geometría, en cooperación con el estímulo de la cepa, que varió de 15-65% de los hidrogeles. Después de una incubación de 3 días, la geometría de hidrogel había dominado la alineación celular bajo tensión compresiva baja, donde las células alineación a lo largo de la dirección de alargamiento de hidrogel bajo alta tensión a la compresión. Entre éstos, las células demostraron alineación al azar debido a la disipación de la radical orientación de elongación de hidrogel y la orientación de la geometría del hidrogel con dibujos.

Para comparar las variaciones mecánicas entre cada hidrogel circular en el chip de estimulación completa tensión degradado, medimos el ancho de línea de cada hidrogel circular en dos de las virutas del mismo, con los volúmenes de inyección de 0 μL (figura 4a) y 40 μl (Figura 4b), respectivamente. El alargamiento porcentual en cada círculo se calcularon dividiendo el alargamiento en el chip 40 μl inyectado por las anchuras de línea de los hidrogeles correspondientes en el chip 0 μl inyectado (figura 4C). El hidrogel es un material incompresible, por lo que la tensión vertical de contratación será equivalente a la tensión de elongación lateral. Por lo tanto, el alargamiento porcentual en el chip con el volumen de inyección 40 μl muestra elongación de 15-65%, que puede convertirse en la cepa a la compresión (véase la archivo adicional 1).
Tinción fluorescente de los núcleos celulares y F-actina con DAPI y phalloidin, respectivamente, se realizó para analizar la alineación celular. La tinción DAPI proporcionaron datos sobre orientación nuclear, y la tinción phalloidin fue aplicada para evaluar la difusión de la célula. Figura 5a -c muestra el alineamiento de celda en el chip de gradiente de tensión. En la línea 1, las células 3T3 alinean a lo largo de la dirección radial. En hidrogel 7, las células alineación al azar, y las células alineación a lo largo de la dirección circular en la línea 12. Según el fluorescente coloración de imágenes, se descubrió un cambio de 90 ° desde el ángulo de alineación de la célula de las células 3T3 en la línea 1 (hidrogel máxima elongación en la dirección radial) en el ángulo de alineación de las celdas con la alineación de eje largo de la línea 12 (menor alargamiento de hidrogel en la dirección radial).
En la anterior investigación2,9, células en hidrogeles con dibujos de línea 200 μm pretenden alinear a lo largo de la dirección de eje largo de la hidrogel. Sin embargo, en este estudio, se observó que el tramo alargado en los hidrogeles de 200 μm en la dirección del eje corto proporcionado otro factor para afectar y dominan la alineación celular controlando el porcentaje de la tensión sobre el hidrogel. Para la cepa de 65% de la línea 1, la alineación radical demostró que el tramo de alargamiento del hidrogel domina la alineación de la celda. Para la cepa de 15% en la línea 12, la alineación circular demostró que el efecto de eje largo había dominado la alineación de la celda. Para la cepa de 40% en hidrogel 7, las células alinean al azar debido a la neutralización de los efectos de dirección y tensión de geometría.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/53715/53715fig1.jpg"> 
Figura 1 . Molde madre de PMMA para PDMS y enchufe fabricación. (a) los componentes separados del molde PMMA, incluyendo una placa inferior, marco límite y un canal de flujo. Después del montaje con cinta de doble cara, (b) el molde de la madre PMMA para la hoja de flujo está formado. (c) molde otro PMMA está montado para el PDMS del enchufe. El número rojo representa la profundidad. (unidad: mm) <a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53715/53715fig1large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/53715/53715fig2.jpg"> 
Figura 2 . Diseño plástico de la fotomáscara para el celular cargado hidrogel Micropattern. Hay dos aberturas con forma de triángulo (2 mm en la línea de fondo y 6,5 mm de altura) conecta a los canales de flujo para suministro de medio de cultivo celular fresco. (a) el plástico photomask está etiquetado con la dimensión. El período de los círculos concéntricos es de 400 nm y el ciclo de trabajo es 50%. El diámetro del centro del círculo es 2 mm. (b) la distribución del photomask, sin etiquetas para impresión láser sobre una capa de plástico transparente. <a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53715/53715fig2large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/53715/53715fig3.jpg"> 
Figura 3. Procesos de fabricación de la gradiente de tensión hidrogel cargadas de celulares a lo largo de la dirección Radial en un Chip fluídico PDMS. (a) un photomask plástico es alineado y pegado bajo el chip con un canal neumático cubierto de TMSPMA. Una micro jeringa con solución de prepolímero de la célula es insertada en la entrada del chip y se utiliza para inyectar aproximadamente 50 μL para llenar el canal de flujo. (b) la salida del canal de flujo se cierra con el PDMS enchufe y se inyecta un adicional 40 μl de solución de prepolímero de la célula. El fondo de cristal es UV-patrón de 30 s para fabricar el hidrogel circular concéntrico en el chip de flujo. (c) se libera la presión del líquido en el canal de flujo desconectando la corriente y la mezcla de las Naciones Unidas-reticulación es lavar con DPBS. (d) un chip con cepa gradiente estático aplica concéntricos hidrogeles cargados de células que están listos para el cultivo de células. Durante el proceso de reticulación UV, se forma (e) una altura gradiente discontinua de hidrogel a lo largo del radio. (f) después de desconectar la toma de corriente, la membrana PDMS se convierte en plana y se aplica tensión de gradiente en los hidrogeles encapsulado en celular. <a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53715/53715fig3large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/53715/53715fig4.jpg"> 
Figura 4. El gradiente de alargamiento de hidrogel puro. El ancho de la línea de alargamiento y porcentaje de hidrogel puro sin encapsulación de la célula en el gradiente de tensión chip el día 3 con el (a) 0 μL (grupo control) y volúmenes de inyección 40 μl (b) . (c) el porcentaje de elongación se calcula dividiendo el valor de la diferencia de anchura de línea entre 40 μl y 0 μL por el ancho de línea de 40 μl. <a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53715/53715fig4large.jpg" target="_blank">haga clic aquí para ver una versión más grande de esta figura.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/53715/53715fig5.jpg"> 
Figura 5 . Imágenes de actina-núcleo mancha fluorescentes del encapsulado de células 3T3 en las fichas degradado el día 3. La dirección de alineación celular en (- c) línea 1, línea 7 del (d-f) y (g-i) 12 revelan radiales, alineación al azar y alineación circular, respectivamente. Los colores verdes y azules muestran las manchas de la actinia y el núcleo, respectivamente. La línea blanca punteada representa el límite del hidrogel. Barra de escala: 200 μm. <a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53715/53715fig5large.jpg" target="_blank">haga clic aquí para ver una versión más grande de esta figura.</a>
Figura 1 complementaria. Cálculo de la curvatura en forma de cúpula PDMS. H (x): la curva convexa de PDMS; H0: la diferencia de altura máxima entre la cúpula PDMS antes y después de la deformación; r: el radio de la cúpula; V: el volumen de inyección excesiva de la región de azul, que causa la deformación de PDMS como una cúpula. Para detalles véase la archivo adicional 1 . <a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53715/Supplementary_Figure_1.tif" target="_blank">Haga clic aquí para descargar esta figura.</a>
Archivo complementario 1. <a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53715/Supplementary_File_1-SI.docx" target="_blank">Haga clic aquí para descargar este archivo.</a>

Watch this Scientific Journal Video about Gradient Strain Chip for Stimulating Cellular Behaviors in Cell-laden Hydrogel at JoVE.com

Gradient Strain Chip for Stimulating Cellular Behaviors in Cell-laden Hydrogel

Este artículo presenta un enfoque simple para proporcionar cepas estática gradiente discontinua en un hidrogel celular cargado concéntrico regular alineación de celda para ingeniería de tejidos.

Gradiente de tensión Chip para estimulantes comportamientos celulares en hidrogel cargadas de celulares

Artificial guidance for cellular alignment is a hot topic in the field of tissue engineering. Most of the previous research has investigated single ...

gradient-strain-chip-for-stimulating-cellular-behaviors-cell-laden

Nanyang Technological University

Research

JoVE Journal

Bioengineering

7.8K vistas.  National Tsing Hua University. Este artículo presenta un enfoque simple para proporcionar cepas estática gradiente discontinua en un hidrogel celular cargado concéntrico regular alineación de celda para ingeniería de tejidos.

Video: Gradient Strain Chip for Stimulating Cellular Behaviors in Cell-laden Hydrogel

Encapsulation of Cardiomyocytes in a Fibrin Hydrogel for Cardiac Tissue Engineering

Culturing cells in a three dimensional hydrogel environment is an important technique for developing constructs for tissue engineering as well as studying cellular responses under various culture conditions in vitro. The three dimensional environment more closely mimics what the cells observe in vivo due to the application of mechanical and chemical stimuli in all dimensions 1. Three-dimensional hydrogels can either be made from synthetic polymers such as PEG-DA 2 and PLGA 3 or a number of naturally occurring proteins such as collagen 4, hyaluronic acid 5 or fibrin 6,7. Hydrogels created from fibrin, a naturally occurring blood clotting protein, can polymerize to form a mesh that is part of the body's natural wound healing processes 8. Fibrin is cell-degradable and potentially autologous 9, making it an ideal temporary scaffold for tissue engineering.
Here we describe in detail the isolation of neonatal cardiomyocytes from three day old rat pups and the preparation of the cells for encapsulation in fibrin hydrogel constructs for tissue engineering. Neonatal myocytes are a common cell source used for in vitro studies in cardiac tissue formation and engineering 4. Fibrin gel is created by mixing fibrinogen with the enzyme thrombin. Thrombin cleaves fibrinopeptides FpA and FpB from fibrinogen, revealing binding sites that interact with other monomers 10. These interactions cause the monomers to self-assemble into fibers that form the hydrogel mesh. Because the timing of this enzymatic reaction can be adjusted by altering the ratio of thrombin to fibrinogen, or the ratio of calcium to thrombin, one can injection mold constructs with a number of different geometries 11,12. Further we can generate alignment of the resulting tissue by how we constrain the gel during culture 13.
After culturing the engineered cardiac tissue constructs for two weeks under static conditions, the cardiac cells have begun to remodel the construct and can generate a contraction force under electrical pacing conditions 6. As part of this protocol, we also describe methods for analyzing the tissue engineered myocardium after the culture period including functional analysis of the active force generated by the cardiac muscle construct upon electrical stimulation, as well as methods for determining final cell viability (Live-Dead assay) and immunohistological staining to examine the expression and morphology of typical proteins important for contraction (Myosin Heavy Chain or MHC) and cellular coupling (Connexin 43 or Cx43) between myocytes.

We describe the isolation of neonatal cardiomyocytes and the preparation of the cells for encapsulation in fibrin hydrogel constructs for tissue engineering. We describe methods for analyzing the tissue engineered myocardium after the culture period including active force generated upon electrical stimulation and cell viability and immunohistological staining.

La encapsulación de los cardiomiocitos en un hidrogel de fibrina para ingeniería de tejidos cardíacos

Culturing cells in a three dimensional hydrogel environment is an important technique for developing constructs for tissue engineering as well as studying ...

Investigación

Bioingeniería

Cellular Lipid Extraction for Targeted Stable Isotope Dilution Liquid Chromatography-Mass Spectrometry Analysis

The metabolism of fatty acids, such as arachidonic acid (AA) and linoleic acid (LA), results in the formation of oxidized bioactive lipids, including numerous stereoisomers1,2. These metabolites can be formed from free or esterified fatty acids. Many of these oxidized metabolites have biological activity and have been implicated in various diseases including cardiovascular and neurodegenerative diseases, asthma, and cancer3-7. Oxidized bioactive lipids can be formed enzymatically or by reactive oxygen species (ROS). Enzymes that metabolize fatty acids include cyclooxygenase (COX), lipoxygenase (LO), and cytochromes P450 (CYPs)1,8. Enzymatic metabolism results in enantioselective formation whereas ROS oxidation results in the racemic formation of products.
While this protocol focuses primarily on the analysis of AA- and some LA-derived bioactive metabolites; it could be easily applied to metabolites of other fatty acids. Bioactive lipids are extracted from cell lysate or media using liquid-liquid (l-l) extraction. At the beginning of the l-l extraction process, stable isotope internal standards are added to account for errors during sample preparation. Stable isotope dilution (SID) also accounts for any differences, such as ion suppression, that metabolites may experience during the mass spectrometry (MS) analysis9. After the extraction, derivatization with an electron capture (EC) reagent, pentafluorylbenzyl bromide (PFB) is employed to increase detection sensitivity10,11. Multiple reaction monitoring (MRM) is used to increase the selectivity of the MS analysis. Before MS analysis, lipids are separated using chiral normal phase high performance liquid chromatography (HPLC). The HPLC conditions are optimized to separate the enantiomers and various stereoisomers of the monitored lipids12. This specific LC-MS method monitors prostaglandins (PGs), isoprostanes (isoPs), hydroxyeicosatetraenoic acids (HETEs), hydroxyoctadecadienoic acids (HODEs), oxoeicosatetraenoic acids (oxoETEs) and oxooctadecadienoic acids (oxoODEs); however, the HPLC and MS parameters can be optimized to include any fatty acid metabolites13.
Most of the currently available bioanalytical methods do not take into account the separate quantification of enantiomers. This is extremely important when trying to deduce whether or not the metabolites were formed enzymatically or by ROS. Additionally, the ratios of the enantiomers may provide evidence for a specific enzymatic pathway of formation. The use of SID allows for accurate quantification of metabolites and accounts for any sample loss during preparation as well as the differences experienced during ionization. Using the PFB electron capture reagent increases the sensitivity of detection by two orders of magnitude over conventional APCI methods. Overall, this method, SID-LC-EC-atmospheric pressure chemical ionization APCI-MRM/MS, is one of the most sensitive, selective, and accurate methods of quantification for bioactive lipids.

This protocol will demonstrate the extraction and analysis of free and esterified bioactive fatty acids from cells. Fatty acids are accurately quantified using stable isotope dilution, chiral liquid chromatography, electron capture atmospheric chemical ionization multiple reaction monitoring mass spectrometry (SID-LC-ECAPCI-MRM/MS).

Extracción de los lípidos celulares orientadas por dilución de isótopos estables análisis de espectrometría de cromatografía de líquidos-Mass

The metabolism of fatty acids, such as arachidonic acid (AA) and linoleic acid (LA), results in the formation of oxidized bioactive lipids, including ...

A Microfluidic Chip for ICPMS Sample Introduction

This protocol discusses the fabrication and usage of a disposable low cost microfluidic chip as sample introduction system for inductively coupled plasma mass spectrometry (ICPMS). The chip produces monodisperse aqueous sample droplets in perfluorohexane (PFH). Size and frequency of the aqueous droplets can be varied in the range of 40 to 60 &#181;m and from 90 to 7,000&#160;Hz, respectively. The droplets are ejected from the chip with a second flow of PFH and remain intact during the ejection. A custom-built desolvation system removes the PFH and transports the droplets into the ICPMS. Here, very stable signals with a narrow intensity distribution can be measured, showing the monodispersity of the droplets. We show that the introduction system can be used to quantitatively determine iron in single bovine red blood cells. In the future, the capabilities of the introduction device can easily be extended by the integration of additional microfluidic modules.

We present a discrete droplet sample introduction system for inductively coupled plasma mass spectrometry (ICPMS). It is based on a cheap and disposable microfluidic chip that generates highly monodisperse droplets in a size range of 40&#8722;60 &#181;m at frequencies from 90 to 7,000 Hz.

Un chip de microfluidos para ICPMS Introducción Muestra

This protocol discusses the fabrication and usage of a disposable low cost microfluidic chip as sample introduction system for inductively coupled plasma ...

Electrotaxis Studies of Lung Cancer Cells using a Multichannel Dual-electric-field Microfluidic Chip

The behavior of directional cell migration under a direct current electric-field (dcEF) is referred to as electrotaxis. The significant role of physiological dcEF in guiding cell movement during embryo development, cell differentiation, and wound healing has been demonstrated in many studies. By applying microfluidic chips to an electrotaxis assay, the investigation process is shortened and experimental errors are minimized. In recent years, microfluidic devices made of polymeric substances (e.g., polymethylmethacrylate, PMMA, or acrylic) or polydimethylsiloxane (PDMS) have been widely used in studying the responses of cells to electrical stimulation. However, unlike the numerous steps required to fabricate a PDMS device, the simple and rapid construction of the acrylic micro&#64258;uidic chip makes it suitable for both device prototyping and production. Yet none of the reported devices facilitate the efficient study of the simultaneous chemical and dcEF effects on cells. In this report, we describe our design and fabrication of an acrylic-based multichannel dual-electric-field (MDF) chip to investigate the concurrent effect of chemical and electrical stimulation on lung cancer cells. The MDF chip provides eight combinations of electrical/chemical stimulations in a single test. The chip not only greatly shortens the required experimental time but also increases accuracy in electrotaxis studies.

Many microfluidic devices have been developed for use in the study of electrotaxis. Yet, none of these chips allows the efficient study of the simultaneous chemical and electric-field (EF) effects on cells. We developed a polymethylmethacrylate-based device that offers better-controlled coexisting EF and chemical stimulation for use in electrotaxis research.

Estudios electrotaxis de pulmón células de cáncer utilizando un Multicanal Dual-campo eléctrico chip de microfluidos

The behavior of directional cell migration under a direct current electric-field (dcEF) is referred to as electrotaxis. The significant role of ...

Construction of Modular Hydrogel Sheets for Micropatterned Macro-scaled 3D Cellular Architecture

Hydrogels can be patterned at the micro-scale using microfluidic or micropatterning technologies to provide an in vivo-like three-dimensional (3D) tissue geometry. The resulting 3D hydrogel-based cellular constructs have been introduced as an alternative to animal experiments for advanced biological studies, pharmacological assays and organ transplant applications. Although hydrogel-based particles and fibers can be easily fabricated, it is difficult to manipulate them for tissue reconstruction. In this video, we describe a fabrication method for micropatterned alginate hydrogel sheets, together with their assembly to form a macro-scale 3D cell culture system with a controlled cellular microenvironment. Using a mist form of the calcium gelling agent, thin hydrogel sheets are easily generated with a thickness in the range of 100 - 200 &#181;m, and with precise micropatterns. Cells can then be cultured with the geometric guidance of the hydrogel sheets in freestanding conditions. Furthermore, the hydrogel sheets can be readily manipulated using a micropipette with an end-cut tip, and can be assembled into multi-layered structures by stacking them using a patterned polydimethylsiloxane (PDMS) frame. These modular hydrogel sheets, which can be fabricated using a facile process, have potential applications of in vitro drug assays and biological studies, including functional studies of micro- and macrostructure and tissue reconstruction.

We describe the fabrication of micropatterned hydrogel sheets using a simple process, which can be assembled and manipulated in a freestanding form. Using these modular hydrogel sheets, a simple macro-scaled 3D cell culture system can be generated with a controlled cellular microenvironment.

Construcción de Hojas modular de hidrogel para la arquitectura celular 3D a escala macro micropatterned

Hydrogels can be patterned at the micro-scale using microfluidic or micropatterning technologies to provide an in vivo-like three-dimensional (3D) tissue ...

Improved 3D Hydrogel Cultures of Primary Glial Cells for In Vitro Modelling of Neuroinflammation

In the central nervous system, numerous acute injuries and neurodegenerative disorders, as well as implanted devices or biomaterials engineered to enhance function result in the same outcome: excess inflammation leads to gliosis, cytotoxicity, and/or formation of a glial scar that collectively exacerbate injury or prevent healthy recovery. With the intent of creating a system to model glial scar formation and study inflammatory processes, we have generated a 3D cell scaffold capable of housing primary cultured glial cells: microglia that regulate the foreign body response and initiate the inflammatory event, astrocytes that respond to form a fibrous scar, and oligodendrocytes that are typically vulnerable to inflammatory injury. The present work provides a detailed step-by-step method for the fabrication, culture, and microscopic characterization of a hyaluronic acid-based 3D hydrogel scaffold with encapsulated rat brain-derived glial cells. Further, protocols for characterization of cell encapsulation and the hydrogel scaffold by confocal immunofluorescence and scanning electron microscopy are demonstrated, as well as the capacity to modify the scaffold with bioactive substrates, with incorporation of a commercial basal lamina mixture to improved cell integration.

Improved 3D Hydrogel Cultures of Primary Glial Cells for In Vitro Modelling of Neuroinflammation

Herein, we present a protocol for the 3D culture of rat brain-derived glia cells, including astrocytes, microglia, and oligodendrocytes. We demonstrate primary cell culture, methacrylated hyaluronic acid (HAMA) hydrogel synthesis, HAMAphoto-polymerization and cell encapsulation, and sample processing for confocal and scanning electron microscopic imaging.

Mejora 3D hidrogel culturas de células Glial primarias para In Vitro modelado de neuroinflamación

In the central nervous system, numerous acute injuries and neurodegenerative disorders, as well as implanted devices or biomaterials engineered to enhance ...

Repressing Gene Transcription by Redirecting Cellular Machinery with Chemical Epigenetic Modifiers

Regulation of chromatin compaction is an important process that governs gene expression in higher eukaryotes. Although chromatin compaction and gene expression regulation are commonly disrupted in many diseases, a locus-specific, endogenous, and reversible method to study and control these mechanisms of action has been lacking. To address this issue, we have developed and characterized novel gene-regulating bifunctional molecules. One component of the bifunctional molecule binds to a DNA-protein anchor so that it will be recruited to an allele-specific locus. The other component engages endogenous cellular chromatin-modifying machinery, recruiting these proteins to a gene of interest. These small molecules, called chemical epigenetic modifiers (CEMs), are capable of controlling gene expression and the chromatin environment in a dose-dependent and reversible manner. Here, we detail a CEM approach and its application to decrease gene expression and histone tail acetylation at a Green Fluorescent Protein (GFP) reporter located at the Oct4 locus in mouse embryonic stem cells (mESCs). We characterize the lead CEM (CEM23) using fluorescent microscopy, flow cytometry, and chromatin immunoprecipitation (ChIP), followed by a quantitative polymerase chain reaction (qPCR). While the power of this system is demonstrated at the Oct4 locus, conceptually, the CEM technology is modular and can be applied in other cell types and at other genomic loci.

Regulation of the chromatin environment is an essential process required for proper gene expression. Here, we describe a method for controlling gene expression through the recruitment of chromatin-modifying machinery in a gene-specific and reversible manner.

Reprimiendo la transcripción genética redirigiendo la maquinaria celular con modificadores químicos de epigenéticas

Regulation of chromatin compaction is an important process that governs gene expression in higher eukaryotes. Although chromatin compaction and gene ...

Fabricating a Kidney Cortex Extracellular Matrix-Derived Hydrogel

Extracellular matrix (ECM) provides important biophysical and biochemical cues to maintain tissue homeostasis. Current synthetic hydrogels offer robust mechanical support for in vitro cell culture but lack the necessary protein and ligand composition to elicit physiological behavior from cells. This manuscript describes a fabrication method for a kidney cortex ECM-derived hydrogel with proper mechanical robustness and supportive biochemical composition. The hydrogel is fabricated by mechanically homogenizing and solubilizing decellularized human kidney cortex ECM. The matrix preserves native kidney cortex ECM protein ratios while also enabling gelation to physiological mechanical stiffnesses. The hydrogel serves as a substrate upon which kidney cortex-derived cells can be maintained under physiological conditions. Furthermore, the hydrogel composition can be manipulated to model a diseased environment which enables the future study of kidney diseases.

Here we present a protocol to fabricate a kidney cortex extracellular matrix-derived hydrogel to retain the native kidney extracellular matrix (ECM) structural and biochemical composition. The fabrication process and its applications are described. Finally, a perspective on using this hydrogel to support kidney-specific cellular and tissue regeneration and bioengineering is discussed.

Fabricación de un hidrogel de derivados de matriz extracelular renal corteza

Extracellular matrix (ECM) provides important biophysical and biochemical cues to maintain tissue homeostasis. Current synthetic hydrogels offer robust ...

A Microfluidic Platform for Stimulating Chondrocytes with Dynamic Compression

Mechanical stimuli are known to modulate biological functions of cells and tissues. Recent studies have suggested that compressive stress alters growth plate cartilage architecture and results in growth modulation of long bones of children. To determine the role of compressive stress in bone growth, we created a microfluidic device actuated by pneumatic pressure, to dynamically (or statically) compress growth plate chondrocytes embedded in alginate hydrogel cylinders. In this article, we describe detailed methods for fabricating and characterizing this device. The advantages of our protocol are: 1) Five different magnitudes of compressive stress can be generated on five technical replicates in a single platform, 2) It is easy to visualize cell morphology via a conventional light microscope, 3) Cells can be rapidly isolated from the device after compression to facilitate downstream assays, and 4) The platform can be applied to study mechanobiology of any cell type that can grow in hydrogels.

This article provides detailed methods for fabricating and characterizing a pneumatically actuating microfluidic device for chondrocyte compression.

Una plataforma microfluídica para estimular los condrocitos con compresión dinámica

Mechanical stimuli are known to modulate biological functions of cells and tissues. Recent studies have suggested that compressive stress alters growth ...

Pancreatic Tissue-Derived Extracellular Matrix Bioink for Printing 3D Cell-Laden Pancreatic Tissue Constructs

The transplantation of pancreatic islets is a promising treatment for patients who suffer from type 1 diabetes accompanied by hypoglycemia and secondary complications. However, islet transplantation still has several limitations such as the low viability of transplanted islets due to poor islet engraftment and hostile environments. In addition, the insulin-producing cells differentiated from human pluripotent stem cells have limited ability to secrete sufficient hormones that can regulate the blood glucose level; therefore, improving the maturation by culturing cells with proper microenvironmental cues is strongly required. In this article, we elucidate protocols for preparing a pancreatic tissue-derived decellularized extracellular matrix (pdECM) bioink to provide a beneficial microenvironment that can increase glucose sensitivity of pancreatic islets, followed by describing the processes for generating 3D pancreatic tissue constructs using a microextrusion-based bioprinting technique.

Decellularized extracellular matrix (dECM) can provide suitable microenvironmental cues to recapitulate the inherent functions of target tissues in an engineered construct. This article elucidates the protocols for the decellularization of pancreatic tissue, evaluation of pancreatic tissue-derived dECM bioink, and generation of 3D pancreatic tissue constructs using a bioprinting technique.

Bioink de matriz extracelular derivada del tejido pancreático para imprimir construcciones de tejido pancreático laden de células 3D

The transplantation of pancreatic islets is a promising treatment for patients who suffer from type 1 diabetes accompanied by hypoglycemia and secondary ...