This project was supported by grants NIH NIGMS 8P41 GM103540-28 and P50-GM076516

1. Preparación de muestras <ol><li> Mantener células CHOK1 en matraces de cultivo de tejido utilizando DMEM suplementado con suero bovino fetal al 10% y 100 UI / ml de penicilina 50 g / ml de estreptomicina. Se incuban las células en una incubadora humidificado 5% de CO 2 a 37 ° C. </li><li> Cosecha y luego placa células CHOK1 sobre un diámetro micro-bien 14 mm con un espesor de 0,16 mm superficie. Se siembran las células de la densidad óptima para la imagen, en torno al 60-70% de confluencia. </li><li> Se incuban las células durante la noche a 37 ° C, 5% de CO 2. Lavar las células tres veces en HBSS (Hank Buffered Saline Solution), e incubar las células en una solución que contiene 50 nM de DND26 Lysotracker verde y 150 nM de verde rastreador de la tubulina. Se incuban las células durante 1 hora a 37 ° C. Paso opcional: Antes de la incubación, realizar una tinción adicional con un colorante de tinción de la matriz mitocondrial (25 nM). </li><li> Lavar las células tres veces en HBSS para eliminar cualquier colorante no unido. Añadir medio de cultivo DMEM fresco antes de la imagción de las células. </li></ol> 2. Microscopio Configuraciones El microscopio para el rastreo de partículas se describe en el protocolo de vídeo está montado en el bastidor de un microscopio invertido comercialmente disponible (Figura 4). Sin embargo módulos comerciales para el rastreo de partículas orbital 3D ya están disponibles. <ol><li> Use un II coherente Camaleón-Ultra Ti: Sa femtosegundo fuente de luz de excitación láser, con una longitud de onda sintonizable rango de salida entre 690 nm-1040 nm. </li><li> Asegúrese de que el rayo láser está alineado en el puerto trasero del microscopio utilizando espejos IR-revestido. El rayo láser se atenúa usando una placa de media onda giratoria seguido por un polarizador lineal calcita. Atenuar el haz de manera que la potencia media en la muestra es entre 0.5 y 2 mW. NOTA: El rayo láser se refleja por un par de espejos accionados por motor galvanómetro que permiten el control de la posición y trayectoria del haz enfocado en el plano de la muestra. En unaconfiguración típica del haz de láser colimado que sale de los espejos de galvanómetro se expande (10X) que pasa a través de un expansor de haz, antes de entrar en la parte trasera del objetivo del microscopio después de la reflexión en espejo dicroico pase corto. </li><li> Recoger la luz de fluorescencia de la muestra mediante la colocación de un objetivo de alta abertura numérica agua (60X, NA 1.2) en la trayectoria de la luz. Elegir un cubo de filtro de fluorescencia de acuerdo con las longitudes de onda de emisión deseados en uno o dos de configuración de canal. Emplear filtros de paso de banda de emisión para seleccionar aún más la gama espectral de la fluorescencia emitida. </li><li> Colocar la muestra en una platina motorizada, y ajustar la multa movimiento del objetivo del microscopio utilizando un piezo-controlador objetivo. </li><li> Dirija la luz del cubo de filtro en tubos fotomultiplicadores donde se discrimina la señal y la envía a un I / O tarjeta de adquisición de datos digital. NOTA: El ordenador genera formas de onda son la salida analógica de la tarjeta de E / S y son Provided a los escáneres de control de la electrónica. La entrada de conteo de fotones de los fotomultiplicadores y la señal de salida a los escáneres se mide y se controla a través de la tarjeta de E / S por el Laboratorio de software de fluorescencia Dynamics SimFCS. </li></ol> 3. Imaging <ol><li> Coloque las células en el escenario y enfocar con iluminación de luz transmitida. </li><li> Cambiar a formación de imágenes de exploración de trama para identificar las células que han incorporado el colorante y para visualizar los microtúbulos subyacentes. Identificar la zona inicial donde el movimiento de la vesícula está presente. </li><li> Una vez que una vesícula aislado se identificó, establecer los siguientes parámetros para el seguimiento orbital: <ol><li> Seleccione el radio de la órbita para definir el tamaño de la exploración circular de acuerdo con el tamaño de la partícula siendo rastreado. Para un emisor de punto, establecer el radio de la órbita igual a la cintura de la función de dispersión del punto (PSF) de la viga de excitación para maximizar la sensibilidad y la respuesta. </li><li> Ajuste el axialdistanciarse para definir la distancia entre las dos órbitas que se realizan para localizar la posición de la partícula a lo largo de la dirección axial. Establezca la distancia axial a 1,5-3 veces la cintura PSF. </li><li> Definir el tiempo de permanencia en función del brillo de la partícula para establecer el tiempo dedicado a cada punto de la órbita, que también determinará el tipo de foto-blanqueo. Utilice un tiempo de espera entre 10 a 100 microsegundos. </li><li> Establecer el número de puntos en cada órbita a 64 o 128 para producir períodos orbitales en el orden de 4-32 ms y proporcionar una alta resolución temporal para determinar la posición de la partícula. </li></ol></li><li> Cambie la señal DC compensar envía a los espejos con el fin de centrar el haz sobre la partícula a través de la interfaz gráfica de usuario a través de una selección cursor en la imagen raster-escaneada. </li><li> Comience seguimiento al cambiar el modo de microscopio de raster de imágenes para la exploración orbital. </li><li> Active la recogida de opiniones y datos. </li></ol> 4. TrajectAnálisis ory <ol><li> Utilice el software para visualizar la fluorescencia recogida en cada punto a lo largo de la órbita y en cada punto en la forma de una &quot;alfombra intensidad&quot; tiempo. La intensidad de recogida a lo largo de la alfombra proporciona información sobre la interacción de la partícula con otros objetos brillantes. Utilice el software para visualizar tanto la información de trayectoria (es decir, el desplazamiento de CC en el tiempo de la x, y y los escáneres de la -piezo z), así como la intensidad de fluorescencia obtenida de la tubo fotomultiplicador con el tiempo en forma de series de tiempo. </li><li> Utilice la representación de series de tiempo y la información &#39;alfombra intensidad &quot;para seleccionar sólo una región de interés en la trayectoria. </li><li> Utilice el software para mostrar una proyección 2D de la parte seleccionada de la trayectoria de la partícula. Seleccione los controles apropiados para el código de color de acuerdo a la trayectoria de la intensidad de fluorescencia de las partículas. </li><li> Seleccione la opción para mostrar la partículo trayectoria en 3D, y código de color de acuerdo a la intensidad de fluorescencia. Girar la trayectoria en 3D utilizando los controles para visualizar las características del movimiento lisosoma a lo largo de los microtúbulos. </li></ol>

<ol>
	<li>So, P. T., Dong, C. Y., Masters, B. R., Berland, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two+photon+excitation+fluorescence+microscopy.">Two photon excitation fluorescence microscopy.</a> Annu Rev Biomed Eng. 2, 399-429 (2000).</li><li>Dupont, A., Lamb, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoscale+three+dimensional+single+particle+tracking.">Nanoscale three dimensional single particle tracking.</a> Nanoscale. 3, 4532-4541 (2011).</li><li>Estrada, L. C., Gratton, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D+nanometer+images+of+biological+fibers+by+directed+motion+of+gold+nanoparticles.">3D nanometer images of biological fibers by directed motion of gold nanoparticles.</a> Nano Lett. 11, 4656-4660 (2011).</li><li>Kis-Petikova, K., Gratton, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Distance+measurement+by+circular+scanning+of+the+excitation+beam+in+the+two+photon+microscope.">Distance measurement by circular scanning of the excitation beam in the two photon microscope.</a> Microscopy Research and Technique. 63, 34-49 (2004).</li><li>Levi, V., Ruan, Q., Gratton, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3+D+particle+tracking+in+a+two+photon+microscope+application+to+the+study+of+molecular+dynamics+in+cells.">3 D particle tracking in a two photon microscope application to the study of molecular dynamics in cells.</a> Biophys J. 88, 2919-2928 (2005).</li><li>Lund, F. W., Wustner, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+comparison+of+single+particle+tracking+and+temporal+image+correlation+spectroscopy+for+quantitative+analysis+of+endosome+motility.">A comparison of single particle tracking and temporal image correlation spectroscopy for quantitative analysis of endosome motility.</a> Journal of Microscopy. 252, 169-188 (2013).</li><li>Nath, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spreading+of+Neurodegenerative+Pathology+via+Neuron+to+Neuron+Transmission+of+beta+Amyloid.">Spreading of Neurodegenerative Pathology via Neuron to Neuron Transmission of beta Amyloid.</a> Journal of Neuroscience. 32, 8767-8777 (2012).</li><li>Balint, S., Vilanova, I. V., Alvarez, A. S., Lakadamyali, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlative+live+cell+and+superresolution+microscopy+reveals+cargo+transport+dynamics+at+microtubule+intersections.">Correlative live cell and superresolution microscopy reveals cargo transport dynamics at microtubule intersections.</a> Proceedings of the National Academy of Sciences of the United States of America. 110, 3375-3380 (2013).</li><li>Huotari, J., Helenius, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endosome+maturation.">Endosome maturation.</a> Embo Journal. 30, 3481-3500 (2011).</li><li>Ragan, T., So, P. T., Kwon, H. S., Gratton, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D+particle+tracking+on+the+two+photon+microscope.">3D particle tracking on the two photon microscope.</a> Multiphoton Microscopy in the Biomedical Sciences. 2, 247-258 (2001).</li><li>Konig, K., So, P. T. C., Mantulin, W. W., Gratton, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+response+to+near-infrared+femtosecond+laser+pulses+in+two+photon+microscopes.">Cellular response to near-infrared femtosecond laser pulses in two photon microscopes.</a> Optics Letters. 22, 135-136 (1997).</li><li>Caviston, J. P., Holzbaur, E. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microtubule+motors+at+the+intersection+of+trafficking+and+transport.">Microtubule motors at the intersection of trafficking and transport.</a> Trends Cell Biol. 16, 530-537 (2006).</li><li>Cardarelli, F., Lanzano, L., Gratton, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Capturing+directed+molecular+motion+in+the+nuclear+pore+complex+of+live+cells.">Capturing directed molecular motion in the nuclear pore complex of live cells.</a> Proceedings of the National Academy of Sciences of the United States of America. 109, 9863-9868 (2012).</li></ol>

The authors have nothing to disclose.

A pesar de los enormes progresos de las técnicas de microscopía de fluorescencia y instrumentaciones de los últimos años, logrando trayectorias de las partículas fluorescentes en tres dimensiones con una alta resolución temporal se ha mantenido un reto en el campo. Si de alta resolución temporal se ha logrado partículas de rastreo en dos dimensiones, la extensión a la dirección axial típicamente trae una drástica reducción en la respuesta de frecuencia del sistema 10. ...

Un gran número de enfoques han sido desarrollados hasta la fecha para realizar un seguimiento de partículas fluorescentes en tres dimensiones usando un microscopio. La mayoría de los enfoques se basan en el uso de cámaras rápidas, ideal para realizar un seguimiento en dos dimensiones, por lo general combinados con modificaciones personalizadas de la óptica de emisión del microscopio para lograr el seguimiento en la dirección axial. Microscopios de barrido láser confocal (ya sea o dos fotones) convencionalmente puede rastrear una partícula fluorescente mediante la realización de una secuencia temporal de z-pilas, aunque este proceso es típicamente mucho tiempo, y produce resolución de tiempo razonable (10 Hz) sólo si la partícula está realizando un seguimiento es mantenido en el centro de una pequeña región de formación de imágenes de trama por un mecanismo de retroalimentación activo 2. La idea de quedarse atrapado en la partícula es la base del método de seguimiento orbital. En lugar de una trama escanear una órbita circular que se realiza alrededor de la partícula fluorescente. La intensidad de la fluorescencia a lo largola órbita localiza con precisión la posición de la partícula 4. La posición localizada de la partícula puede entonces ser utilizada para accionar los escáneres de microscopio y re-centro de la órbita en la posición de la partícula. Los escáneres galvanómetro del microscopio son impulsados ​​por una tensión analógica. El componente de AC de este voltaje permite realizar una órbita con el haz de láser enfocado, es decir, un seno y una onda de coseno aplicado a los espejos de exploración X e Y permitirá la realización de una órbita circular. El desplazamiento de la señal de DC facilita el cambio de la posición del centro de la órbita. Una vez que un período de órbita y se determina la forma de onda para la señal de CA está configurado, el sistema de retroalimentación necesita actualizar sólo el componente DC de la señal. Un software capaz de leer la señal fluorescente obtenida de los detectores se requiere para el control de los escáneres y los detectores, para calcular la posición de la partícula y actualizar el DC fueraestablecer. Para una evaluación exitosa imágenes de una cuidadosa selección de los parámetros de órbita (tamaño y calendario) que se requiere y estos parámetros tienen que ser ajustado en base a las características de las partículas fluorescentes que es necesario realizar un seguimiento. Los fundamentos físicos y matemáticos de la técnica se han descrito en el pasado de 4,5 tanto para aplicaciones 2D y 3D. En este protocolo se describen brevemente los principales componentes de hardware de la configuración, y con más detalle la elección de los parámetros y de la preparación de la muestra necesario para un experimento típico permitiéndonos tras el desplazamiento de un lisosoma en una alta resolución temporal dentro de una célula viva.

<table border="0" cellpadding="0" cellspacing="0" width="525">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:197px;">Name</td>
			<td style="width:160px;">Company</td>
			<td style="width:168px;">Model</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Lysotracker DND 26</td>
			<td>Life technologies</td>
			<td>L-7526</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">tubuline tracker Green</td>
			<td>Life technologies</td>
			<td>T34075</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Mitotracker RED</td>
			<td>Life technologies</td>
			<td>M7512</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Coherent Chamelon- ultra II TI</td>
			<td>Coherent</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Calcite polarize</td>
			<td>Melles Griot Glan&#160;</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Galvanometer-motor mirror</td>
			<td>Cambridge technologies</td>
			<td>M 6350</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Dichroic mirror</td>
			<td>Chroma technologies</td>
			<td>700 DCSPXR</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Motorized stage</td>
			<td>ASI</td>
			<td>MS2000</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Piezo&#160;</td>
			<td>PI</td>
			<td>P721-LLQ</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Photomultiplier tube</td>
			<td>Hamamatsu</td>
			<td>H7422P-40</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Data acquisition card</td>
			<td>IO tech</td>
			<td>PCI 1128-4000</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Imaging software</td>
			<td>LFD</td>
			<td>Global for images-SimFCS</td>
		</tr>
	</tbody>
</table>

3d orbital tracking in a modified two-photon microscope: an application to the tracking of intracellular vesicles

El objetivo de este protocolo de vídeo es discutir cómo realizar y analizar un tridimensional fluorescente orbital experimento de rastreo de partículas usando un microscopio de dos fotones modificado 1. A diferencia de los enfoques convencionales de exploración de trama (o campo amplio basado en una pila de marcos), el seguimiento orbital 3D permite localizar y seguir con una alta resolución espacial (10 exactitud nm) y la resolución temporal (respuesta de frecuencia 50 Hz) el desplazamiento de 3D una partícula fluorescente pasar longitud escalas de cientos de micras 2. El método se basa en un algoritmo de realimentación que controla el hardware de una de dos fotones microscopio de barrido láser con el fin de realizar una órbita circular alrededor del objeto a ser rastreados: el mecanismo de retroalimentación mantendrá el objeto fluorescente en el centro mediante el control del desplazamiento de el haz de exploración 3-5. Para demostrar las ventajas de esta técnica, hemos seguido un orgánulo de movimiento rápido, el lisosoma, dentro de alcelular iving 6,7. Las células se cultivaron de acuerdo a protocolos estándar, y se tiñeron usando un colorante comercialmente lisosoma. Se discute brevemente la configuración de hardware y con más detalle el software de control, para llevar a cabo un experimento de seguimiento orbital 3D dentro de las células vivas. Se discuten en detalle los parámetros requeridos con el fin de controlar el microscopio de exploración y permitir el movimiento de la viga en una órbita cerrada alrededor de la partícula. Concluimos demostrando cómo este método puede ser usado efectivamente para seguir el movimiento rápido de un lisosoma marcado a lo largo de los microtúbulos en 3D dentro de una célula viva. Los lisosomas pueden moverse con velocidades en el intervalo de 0,4-0,5 m / seg, típicamente presentan un movimiento dirigido a lo largo de la red de microtúbulos 8.

De acuerdo con este protocolo de seguimiento de una sola partícula 3D rápido puede llevar a cabo dentro de las células vivas con un microscopio de dos fotones modificado para seguir el desplazamiento de los lisosomas marcados con fluorescencia. El experimento llevado a cabo consiste en el seguimiento de un lisosoma aislado en movimiento dentro de la célula después del proceso de maduración endosoma 9. Los lisosomas se tiñeron utilizando un tinte verde fluorescente y se excita a 930 nm de excitación qu...

Watch this Scientific Journal Video about 3D Orbital Tracking in a Modified Two-photon Microscope: An Application to the Tracking of Intracellular Vesicles at JoVE.com

3D Orbital Tracking in a Modified Two-photon Microscope: An Application to the Tracking of Intracellular Vesicles

In this video protocol we track - at high speed and in three dimensions - fluorescently labeled lysosomes within living cells, using the orbital tracking method in a modified two-photon microscope.

Rastreo Orbital 3D en un microscopio de dos fotones Modificado: una aplicación para el Seguimiento de vesículas intracelulares

The objective of this video protocol is to discuss how to perform and analyze a three-dimensional fluorescent orbital particle tracking experiment using a ...

3d-orbital-tracking-modified-two-photon-microscope-an-application-to

Research

JoVE Journal

Bioengineering

10.2K vistas.  University of California, Irvine. In this video protocol we track - at high speed and in three dimensions - fluorescently labeled lysosomes within living cells, using the orbital tracking method in a modified two-photon microscope. 

Video: 3D Orbital Tracking in a Modified Two-photon Microscope: An Application to the Tracking of Intracellular Vesicles

Tracking Hypoxic Signaling within Encapsulated Cell Aggregates

In Diabetes mellitus type 1, autoimmune destruction of the pancreatic &beta;-cells results in loss of insulin production and potentially lethal hyperglycemia. As an alternative treatment option to exogenous insulin injection, transplantation of functional pancreatic tissue has been explored1,2. This approach offers the promise of a more natural, long-term restoration of normoglycemia. Protection of the donor tissue from the host's immune system is required to prevent rejection and encapsulation is a method used to help achieve this aim.
Biologically-derived materials, such as alginate3 and agarose4, have been the traditional choice for capsule construction but may induce inflammation or fibrotic overgrowth5 which can impede nutrient and oxygen transport. Alternatively, synthetic poly(ethylene glycol) (PEG)-based hydrogels are non-degrading, easily functionalized, available at high purity, have controllable pore size, and are extremely biocompatible,6,7,8. As an additional benefit, PEG hydrogels may be formed rapidly in a simple photo-crosslinking reaction that does not require application of non-physiological temperatures6,7. Such a procedure is described here. In the crosslinking reaction, UV degradation of the photoinitiator, 1-[4-(2-Hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (Irgacure 2959), produces free radicals which attack the vinyl carbon-carbon double bonds of dimethacrylated PEG (PEGDM) inducing crosslinking at the chain ends. Crosslinking can be achieved within 10 minutes. PEG hydrogels constructed in such a manner have been shown to favorably support cells7,9, and the low photoinitiator concentration and brief exposure to UV irradiation is not detrimental to viability and function of the encapsulated tissue10. While we methacrylate our PEG with the method described below, PEGDM can also be directly purchased from vendors such as Sigma.
An inherent consequence of encapsulation is isolation of the cells from a vascular network. Supply of nutrients, notably oxygen, is therefore reduced and limited by diffusion. This reduced oxygen availability may especially impact &beta;-cells whose insulin secretory function is highly dependent on oxygen11-13. Capsule composition and geometry will also impact diffusion rates and lengths for oxygen. Therefore, we also describe a technique for identifying hypoxic cells within our PEG capsules. Infection of the cells with a recombinant adenovirus allows for a fluorescent signal to be produced when intracellular hypoxia-inducible factor (HIF) pathways are activated14. As HIFs are the primary regulators of the transcriptional response to hypoxia, they represent an ideal target marker for detection of hypoxic signaling15. This approach allows for easy and rapid detection of hypoxic cells. Briefly, the adenovirus has the sequence for a red fluorescent protein (Ds Red DR from Clontech) under the control of a hypoxia-responsive element (HRE) trimer. Stabilization of HIF-1 by low oxygen conditions will drive transcription of the fluorescent protein (Figure 1). Additional details on the construction of this virus have been published previously15. The virus is stored in 10% glycerol at -80&deg; C as many 150 &mu;L aliquots in 1.5 mL centrifuge tubes at a concentration of 3.4 x 1010 pfu/mL. 
Previous studies in our lab have shown that MIN6 cells encapsulated as aggregates maintain their viability throughout 4 weeks of culture in 20% oxygen. MIN6 aggregates cultured at 2 or 1% oxygen showed both signs of necrotic cells (still about 85-90% viable) by staining with ethidium bromide as well as morphological changes relative to cells in 20% oxygen. The smooth spherical shape of the aggregates displayed at 20% was lost and aggregates appeared more like disorganized groups of cells. While the low oxygen stress does not cause a pronounced drop in viability, it is clearly impacting MIN6 aggregation and function as measured by glucose-stimulated insulin secretion15. Western blot analysis of encapsulated cells in 20% and 1% oxygen also showed a significant increase in HIF-1&alpha; for cells cultured in the low oxygen conditions which correlates with the expression of the DsRed DR protein.

A method for photo-encapsulation of cells in a crosslinked PEG hydrogel is described. Hypoxic signaling within encapsulated murine insulinoma (MIN6) aggregates is tracked using a fluorescent marker system. This system allows serial examination of cells within a hydrogel scaffold and correlation of hypoxic signaling with changes in cell phenotype.

Seguimiento de señalización dentro de los agregados de células hipóxicas encapsulado

In Diabetes mellitus type 1, autoimmune destruction of the pancreatic &beta;-cells results in loss of insulin production and potentially lethal ...

Investigación

Bioingeniería

Longitudinal Measurement of Extracellular Matrix Rigidity in 3D Tumor Models Using Particle-tracking Microrheology

The mechanical microenvironment has been shown to act as a crucial regulator of tumor growth behavior and signaling, which is itself remodeled and modified as part of a set of complex, two-way mechanosensitive interactions. While the development of biologically-relevant 3D tumor models have facilitated mechanistic studies on the impact of matrix rheology on tumor growth, the inverse problem of mapping changes in the mechanical environment induced by tumors remains challenging. Here, we describe the implementation of particle-tracking microrheology (PTM) in conjunction with 3D models of pancreatic cancer as part of a robust and viable approach for longitudinally monitoring physical changes in the tumor microenvironment, in situ. The methodology described here integrates a system of preparing in vitro 3D models embedded in a model extracellular matrix (ECM) scaffold of Type I collagen with fluorescently labeled probes uniformly distributed for position- and time-dependent microrheology measurements throughout the specimen. In vitro tumors are plated and probed in parallel conditions using multiwell imaging plates. Drawing on established methods, videos of tracer probe movements are transformed via the Generalized Stokes Einstein Relation (GSER) to report the complex frequency-dependent viscoelastic shear modulus, G*(&#969;). Because this approach is imaging-based, mechanical characterization is also mapped onto large transmitted-light spatial fields to simultaneously report qualitative changes in 3D tumor size and phenotype. Representative results showing contrasting mechanical response in sub-regions associated with localized invasion-induced matrix degradation as well as system calibration, validation data are presented. Undesirable outcomes from common experimental errors and troubleshooting of these issues are also presented. The 96-well 3D culture plating format implemented in this protocol is conducive to correlation of microrheology measurements with therapeutic screening assays or molecular imaging to gain new insights into impact of treatments or biochemical stimuli on the mechanical microenvironment.

Particle-tracking microrheology can be used to non-destructively quantify and spatially map changes in extracellular matrix mechanical properties in 3D tumor models.

Medida longitudinal de la matriz extracelular Rigidez en modelos de tumores en 3D utilizando partículas de seguimiento Microrheology

The mechanical microenvironment has been shown to act as a crucial regulator of tumor growth behavior and signaling, which is itself remodeled and ...

In Situ Mapping of the Mechanical Properties of Biofilms by Particle-tracking Microrheology

Bacterial cells are able to form surface-attached biofilm communities known as biofilms by encasing themselves in extracellular polymeric substances (EPS). The EPS serves as a physical and protective scaffold that houses the bacterial cells and consists of a variety of materials that includes proteins, exopolysaccharides and DNA. The composition of the EPS may change, which remodels the mechanic properties of the biofilm to further develop or support alternative biofilm structures, such as streamers, as a response to environmental cues. Despite this, there are little quantitative descriptions on how EPS components contribute to the mechanical properties and function of biofilms. Rheology, the study of the flow of matter, is of particular relevance to biofilms as many biofilms grow in flow conditions and are constantly exposed to shear stress. It also provides measurement and insight on the spreading of the biofilm on a surface. Here, particle-tracking microrheology is used to examine the viscoelasticity and effective crosslinking roles of different matrix components in various parts of the biofilm during development. This approach allows researchers to measure mechanic properties of biofilms at the micro-scale, which might provide useful information for controlling and engineering biofilms.

In Situ Mapping of the Mechanical Properties of Biofilms by Particle-tracking Microrheology

Particle-tracking microrheology investigates the viscoelasticity of materials. Here, the technique is used to determine the viscoelasticity, creep compliance and effective crosslinking roles of different matrix components of a bacterial biofilm. The matrix consists of polymeric substances secreted by the bacteria and its components determine biofilm structure and mechanical properties.

En Mapping in situ de las propiedades mecánicas de biopelículas por partículas de seguimiento Microrheology

Bacterial cells are able to form surface-attached biofilm communities known as biofilms by encasing themselves in extracellular polymeric substances ...

Microfluidic Platform with Multiplexed Electronic Detection for Spatial Tracking of Particles

Microfluidic processing of biological samples typically involves differential manipulations of suspended particles under various force fields in order to spatially fractionate the sample based on a biological property of interest. For the resultant spatial distribution to be used as the assay readout, microfluidic devices are often subjected to microscopic analysis requiring complex instrumentation with higher cost and reduced portability. To address this limitation, we have developed an integrated electronic sensing technology for multiplexed detection of particles at different locations on a microfluidic chip. Our technology, called Microfluidic CODES, combines Resistive Pulse Sensing with Code Division Multiple Access to compress 2D spatial information into a 1D electrical signal. In this paper, we present a practical demonstration of the Microfluidic CODES technology to detect and size cultured cancer cells distributed over multiple microfluidic channels. As validated by the high-speed microscopy, our technology can accurately analyze dense cell populations all electronically without the need for an external instrument. As such, the Microfluidic CODES can potentially enable low-cost integrated lab-on-a-chip devices that are well suited for the point-of-care testing of biological samples.

We demonstrate a microfluidic platform with an integrated surface electrode network that combines resistive pulse sensing (RPS) with code division multiple access (CDMA), to multiplex detection and sizing of particles in multiple microfluidic channels.

Plataforma de microfluidos con multiplexado de detección electrónica para el seguimiento espacial de las partículas

Microfluidic processing of biological samples typically involves differential manipulations of suspended particles under various force fields in order to ...

Assembly and Tracking of Microbial Community Development within a Microwell Array Platform

The development of microbial communities depends on a combination of complex deterministic and stochastic factors that can dramatically alter the spatial distribution and activities of community members. We have developed a microwell array platform that can be used to rapidly assemble and track thousands of bacterial communities in parallel. This protocol highlights the utility of the platform and describes its use for optically monitoring the development of simple, two-member communities within an ensemble of arrays within the platform. This demonstration uses two mutants of Pseudomonas aeruginosa, part of a series of mutants developed to study Type VI secretion pathogenicity. Chromosomal inserts of either mCherry or GFP genes facilitate the constitutive expression of fluorescent proteins with distinct emission wavelengths that can be used to monitor community member abundance and location within each microwell. This protocol describes a detailed method for assembling mixtures of bacteria into the wells of the array and using time-lapse fluorescence imaging and quantitative image analysis to measure the relative growth of each member population over time. The seeding and assembly of the microwell platform, the imaging procedures necessary for the quantitative analysis of microbial communities within the array, and the methods that can be used to reveal interactions between microbial species area all discussed.

The development of microbial communities depends on a combination of factors, including environmental architecture, member abundance, traits, and interactions. This protocol describes a synthetic, microfabricated environment for the simultaneous tracking of thousands of communities contained in femtoliter wells, where key factors such as niche size and confinement can be approximated.

Montaje y Seguimiento de Desarrollo Comunitario Microbiano dentro de una Plataforma de Matriz de Micropedulos

The development of microbial communities depends on a combination of complex deterministic and stochastic factors that can dramatically alter the spatial ...

A Protocol for Real-time 3D Single Particle Tracking

Real-time three-dimensional single particle tracking (RT-3D-SPT) has the potential to shed light on fast, 3D processes in cellular systems. Although various RT-3D-SPT methods have been put forward in recent years, tracking high speed 3D diffusing particles at low photon count rates remains a challenge. Moreover, RT-3D-SPT setups are generally complex and difficult to implement, limiting their widespread application to biological problems. This protocol presents a RT-3D-SPT system named 3D Dynamic Photon Localization Tracking (3D-DyPLoT), which can track particles with high diffusive speed (up to 20 &#181;m2/s) at low photon count rates (down to 10 kHz). 3D-DyPLoT employs a 2D electro-optic deflector (2D-EOD) and a tunable acoustic gradient (TAG) lens to drive a single focused laser spot dynamically in 3D. Combined with an optimized position estimation algorithm, 3D-DyPLoT can lock onto single particles with high tracking speed and high localization precision. Owing to the single excitation and single detection path layout, 3D-DyPLoT is robust and easy to set up. This protocol discusses how to build 3D-DyPLoT step by step. First, the optical layout is described. Next, the system is calibrated and optimized by raster scanning a 190 nm fluorescent bead with the piezoelectric nanopositioner. Finally, to demonstrate real-time 3D tracking ability, 110 nm fluorescent beads are tracked in water.

This protocol details the construction and operation of a real-time 3D single particle tracking microscope capable of tracking nanoscale fluorescent probes at high diffusive speeds and low photon count rates.

Un protocolo para el seguimiento en tiempo real 3D sola partícula

Real-time three-dimensional single particle tracking (RT-3D-SPT) has the potential to shed light on fast, 3D processes in cellular systems. Although ...

An Orbital Shaking Culture of Mammalian Cells in O-shaped Vessels to Produce Uniform Aggregates

Suspension cultures of mammalian cell aggregates are required for various applications in medical and biotechnological fields. The disposable bag-based method is one of the simplest techniques for the mass production of cellular aggregates, but it does not protect the cultures against over-aggregation, which occurs when they gather at the bottom center of the culture vessel. To solve this problem, we developed an O-shaped dish and an O-shaped bag, neither of which contains a central region. Aggregates grown in either O-shaped culture vessel were noticeably more uniform in size than aggregates grown in conventional vessels. Histological analyses showed that aggregates in conventional culture dishes contained necrotic cores most likely caused by a poor oxygen supply. In contrast, aggregates that were grown in the O-shaped bag, even those with similar diameters to aggregates in conventional culture dishes, did not show necrotic cores. These results suggest that the O-shaped bag provides sufficient oxygen to the aggregates due to the oxygen permeability of the bag material. We, therefore, propose that this novel gas-permeable O-shaped culture bag is suitable for the mass production of uniform aggregates that are necessary in various biotechnological fields.

Here we present a protocol for using O-shaped vessels, specialized for suspension cultures of cellular aggregates, with orbital shaking. The HEK293 cells grown in this bag form more homogeneous aggregates than those grown in conventional culture vessels.

Un Orbital agitación cultivo de células mamíferas en vasos en forma de O para producir agregados uniforme

Suspension cultures of mammalian cell aggregates are required for various applications in medical and biotechnological fields. The disposable bag-based ...

Conducting Multiple Imaging Modes with One Fluorescence Microscope

Fluorescence microscopy is a powerful tool to detect biological molecules in situ and monitor their dynamics and interactions in real-time. In addition to conventional epi-fluorescence microscopy, various imaging techniques have been developed to achieve specific experimental goals. Some of the widely used techniques include single-molecule fluorescence resonance energy transfer (smFRET), which can report conformational changes and molecular interactions with angstrom resolution, and single-molecule detection-based super-resolution (SR) imaging, which can enhance the spatial resolution approximately ten&#160;to twentyfold compared to diffraction-limited microscopy. Here we present a customer-designed integrated system, which merges multiple imaging methods in one microscope, including conventional epi-fluorescent imaging, single-molecule detection-based SR imaging, and multi-color single-molecule detection, including smFRET imaging. Different imaging methods can be achieved easily and reproducibly by switching optical elements. This set-up is easy to adopt by any research laboratory in biological sciences with a need for routine and diverse imaging experiments at a reduced cost and space relative to building separate microscopes for individual purposes.

Here we present a practical guide of building an integrated microscopy system, which merges conventional epi-fluorescent imaging, single-molecule detection-based super-resolution imaging, and multi-color single-molecule detection, including single-molecule fluorescence resonance energy transfer imaging, into one set-up in a cost-efficient way.

Realización de múltiples modos de la proyección de imagen con un microscopio de fluorescencia

Fluorescence microscopy is a powerful tool to detect biological molecules in situ and monitor their dynamics and interactions in real-time. In addition to ...

Transplantation of a 3D Bioprinted Patch in a Murine Model of Myocardial Infarction

Testing regenerative properties of 3D bioprinted cardiac patches in vivo using murine models of heart failure via permanent left anterior descending (LAD) ligation is a challenging procedure and has a high mortality rate due to its nature. We developed a method to consistently transplant bioprinted patches of cells and hydrogels onto the epicardium of an infarcted mouse heart to test their regenerative properties in a robust and feasible way. First, a deeply anesthetized mouse is carefully intubated and ventilated. Following left lateral thoracotomy (surgical opening of the chest), the exposed LAD is permanently ligated and the bioprinted patch transplanted onto the epicardium. The mouse quickly recovers from the procedure after chest closure. The advantages of this robust and quick approach include a predicted 28-day mortality rate of up to 30% (lower than the 44% reported by other studies using a similar model of permanent LAD ligation in mice). Moreover, the approach described in this protocol is versatile and could be adapted to test bioprinted patches using different cell types or hydrogels where high numbers of animals are needed to optimally power studies. Overall, we present this as an advantageous approach which may change preclinical testing in future studies for the field of cardiac regeneration and tissue engineering.

This protocol aims to transplant a 3D bioprinted patch onto the epicardium of infarcted mice modeling heart failure. It includes details regarding anesthesia, the surgical chest opening, permanent ligation of the left anterior descending (LAD) coronary artery and application of a bioprinted patch onto the infarcted area of the heart.

Trasplante de un parche bioimpreso 3D en un modelo murino de infarto de miocardio

Testing regenerative properties of 3D bioprinted cardiac patches in vivo using murine models of heart failure via permanent left anterior descending (LAD) ...

Segmenting Growth of Endothelial Cells in 6-Well Plates on an Orbital Shaker for Mechanobiological Studies

Shear stress imposed on the arterial wall by the flow of blood affects endothelial cell morphology and function. Low magnitude, oscillatory and multidirectional shear stresses have all been postulated to stimulate a pro-atherosclerotic phenotype in endothelial cells, whereas high magnitude and unidirectional or uniaxial shear are thought to promote endothelial homeostasis. These hypotheses require further investigation, but traditional in vitro techniques have limitations, and are particularly poor at imposing multidirectional shear stresses on cells. 
One method that is gaining increasing use is to culture endothelial cells in standard multi-well plates on the platform of an orbital shaker; in this simple, low-cost, high-throughput and chronic method, the swirling medium produces different patterns and magnitudes of shear, including multidirectional shear, in different parts of the well. However, it has a significant limitation: cells in one region, exposed to one type of flow, may release mediators into the medium that affect cells in other parts of the well, exposed to different flows, hence distorting the apparent relation between flow and phenotype. 
Here we present an easy and affordable modification of the method that allows cells to be exposed only to specific shear stress characteristics. Cell seeding is restricted to a defined region of the well by coating the region of interest with fibronectin, followed by passivation using passivating solution. Subsequently, the plates can be swirled on the shaker, resulting in exposure of cells to well-defined shear profiles such as low magnitude multidirectional shear or high magnitude uniaxial shear, depending on their location. As before, the use of standard cell-culture plasticware allows straightforward further analysis of the cells. The modification has already allowed the demonstration of soluble mediators, released from endothelium under defined shear stress characteristics, that affect cells located elsewhere in the well.

This protocol describes a coating method to restrict endothelial cell growth to a specific region of a 6-well plate for shear stress application using the orbital shaker model.