Los autores desean agradecer a Chris Morrow para la asistencia técnica. La financiación fue proporcionada por NIH SBIR (R43) conceder 1R43GM101859-01 (MPI) GRANT10940803.

1. Preparación de células Cultura <ol><li> Almacene las poblaciones de células NIH/3T3 en nitrógeno líquido hasta que esté listo para su uso. </li><li> Preparar los medios de comunicación completa para células NIH/3T3 utilizando medio de Eagle modificado de Dulbecco (DMEM) suplementado con suero bovino fetal al 10%, tampón HEPES 10 mM, 50 unidades / ml de penicilina, y 50 mg / ml de estreptomicina. </li><li> Descongelar las células durante 2-3 minutos en un baño de agua con agitación a 37 ° C. </li><li> Resuspender las células en 5 ml de medio completo y se centrifuga a 1500 xg durante 3 min. </li><li> Eliminar el sobrenadante de células sin alterar el sedimento celular. </li><li> Resuspender las células en 5 ml de los medios de comunicación y contar las células usando un hemocitómetro. <ol><li> Retire 10 l de la suspensión celular y colocar en un tubo de microcentrífuga de 0,5 ml. </li><li> Añadir 10 l de azul de tripano a la suspensión celular y se agita con la punta de la pipeta. </li><li> Pipetear 10 l de las células teñidas en una cámara de hemocitómetro. </li><li> Contar las células en un hemocitómetro a 10xmagnificación. <ol><li> Contar las células vivas (pequeñas bolas blancas) para 4 de los 9 cuadrados grandes. Sólo contar las células vivas que no aparecen de color azul oscuro de la mancha azul de tripano. </li><li> Calcular el número medio de células por cuadrado grande, lo que resulta en el número de células x 10 4 células / ml en la suspensión original de células. </li><li> Se siembran las células a una densidad de 1 x 10 5 células / ml con un total de 5 ml en cada matraz T25. </li></ol></li><li> Cultivar las células a entre 70% y 80% de confluencia antes de los experimentos iniciales. Actualizar medios cada 2-3 días o cuando sea necesario. </li></ol></li></ol> 2. Preparación de la superficie de impresión <ol><li> Marcar un rectángulo con el marcador en la parte inferior de una cultura-tratada de tejido de poliestireno (TCTPS) 12 placa así el tamaño de la cabeza de impresión (7 mm x 19 mm). </li><li> Añadir 50 l de suero fetal bovino en el área rectangular y se extendió por toda la región, con la punta. </li><li> Deje la placa de Petrien una estéril bioseguridad capó O / N para que el lugar de suero se seque por completo. Estas placas deben estar preparados no más de 2 días antes de su uso. </li></ol> 3. Impresión Sumergido <ol><li> Enjuague el cabezal de impresión con agua destilada. <ol><li> Llene un 60 mm placa de Petri con agua destilada y acoplar el cabezal de impresión en la superficie. </li><li> El flujo de agua destilada a través de cada una de las líneas durante 2 minutos a 150 l / min utilizando una bomba neumática. </li><li> Deseche el agua de la placa de Petri y llenarlo con agua limpia. </li><li> Mueva el cabezal de impresión hacia arriba y hacia abajo en el agua 3 veces. </li></ol></li><li> Acople el centro de la cabeza de impresión sobre el lugar de suero recubierto en la placa de pre-preparado 12. </li><li> Cebe el cabezal de impresión con medios completos pre-calentado, 300 l por canal. </li><li> Imprimir células suspendidas a una concentración de 50.000 células / ml sobre la superficie y 60 l / min, 100 l por canal. </li><li> Coloque el cabezal de impresión, izquierdo atracado en contra de lasuperficie, y el colector en una incubadora de cultivo celular establece en 5% de CO 2 y 37 ° C durante 2 h. </li><li> Después de la incubación de 2 horas, retire el cabezal de impresión y coloque la tapa en la placa de cultivo. El momento en el que el cabezal de impresión elimina se considera el punto de tiempo 0 h. </li></ol> 4. Cultivo Celular Estándar <ol><li> Añadir 1 ml de medio de pre-calentado a una de la placa TCTPS 12 pocillos sin suero manchado preparado en el paso 2. </li><li> Tomar 1 ml de la suspensión celular restante de la etapa 2 y la pipeta en un solo pocillo de una TCTPS placa de 12 pocillos. Esto producirá un cultivo que contiene 50.000 células en el plato. </li><li> Coloque la placa de cultivo de células en una incubadora a 37 ° C durante 2 h. </li><li> Después de la incubación de 2 horas comenzar el tiempo; para mantener la coherencia entre las muestras impresas y de siembra, esto se considera el punto de tiempo 0 h. </li></ol> 5. Visualización Cultura <ol><li> Después de 0, 2, 24, y 48 células toman horas de cada uno de los dos métodos described arriba y la imagen usando un microscopio invertido estándar. <ol><li> Teñir las células con yoduro de propidio, una mancha fluorescente de color rojo que sólo se incorpora en el núcleo de las células muertas. <ol><li> Enjuague suavemente las células 3 veces con 1 ml de PBS con calcio y magnesio (PBS + +) para eliminar los residuos. </li><li> Añadir 1 ml de pre-calentado PBS + + para cada recipiente de cultivo. </li><li> Añadir 1 l de solución de yoduro de propidio de stock (1 mg / ml) a cada recipiente de cultivo. </li><li> Se incuban las células teñidas con yoduro de propidio a 37 ° C durante 10 min. </li></ol></li><li> Imagen de las células utilizando un microscopio invertido a 10x y 40x. </li></ol></li><li> Deseche las células en un contenedor de residuos sanitarios apropiados. </li></ol>

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Los autores son los empleados y accionistas de Wasatch Microfluídica que produce reactivos y / o instrumentos utilizados en este manuscrito.

La tecnología de impresión 3D de microfluidos se describe aquí es el único capaz de microfluidically matrices de impresión de las células en un líquido lleno de bien, es decir, una superficie sumergida. Por la impresión sobre superficies sumergidas, de células microarrays se pueden producir que mantienen el fenotipo celular fisiológicamente relevante de las células, así como la capacidad de multiplexar las células en el fondo de un solo pozo Figura 4. Los resultados de este estudio...

Los avances recientes en la industria farmacéutica han conducido a un mayor interés en el uso de microarrays de celulares en el proceso de descubrimiento de fármacos para la detección de drogas y análisis cytotoxicological 1,2,3. El desarrollo de los ensayos in vitro de alto rendimiento y los métodos de detección utilizando microarrays de células facilitaría el desarrollo rápido y rentable de los candidatos de la droga, así como en el avance de la comprensión fundamental de la célula de 1,4. El enfoque tradicional para el cribado con células utiliza plataformas de placa de pocillos convencionales; Sin embargo este enfoque es limitado debido al alto costo, rendimiento limitado, y la capacidad limitada para obtener información cuantitativa sobre la función celular 1,5. Debido a estas limitaciones, la investigación en las tecnologías de microarrays celular está creciendo para la caracterización molecular biológica, la ingeniería de tejidos, y la detección de drogas 1,6. Las ventajas de los microarrays de celulares incluyen el uso de la muestra más pequeña, efectos mínimos deheterogeneidad fenotipo celular enmascarar la información, y lo más importante la capacidad de automatizar los ensayos para más aplicaciones de alto rendimiento 1,7,8. La industria farmacéutica utiliza actualmente ensayos de cribado basados ​​en células de alto rendimiento con cultivos monocapa de células 2D para la detección de drogas en placas de pocillos de microtitulación 9. Células de multiplexación en pocillos de placas de microtitulación ofrece el potencial para un mayor rendimiento con opciones de experimentación únicas. Además, las tecnologías actuales para microarrays de celulares permiten que las células se sequen que podría alterar dramáticamente el fenotipo de las células in vivo a partir de 10,11. Con el fin de superar estos problemas, el ACFM se ha diseñado y se muestra en la Figura 1. El diseño de los fluidos MFCA 3D permite a la punta del cabezal de impresión en la Figura 1 para ser rebajado en un baño y se comprime contra una superficie para formar un sello. La punta de silicona suave de la cabeza de impresión se comporta como unjunta y forma un sello reversible. La tecnología ACFM es adecuado de forma única para interactuar con las superficies sumergidas, que se requiere para ambos cultivos celulares y sistemas de corte de tejido, y es difícil o imposible con la mayoría de otros enfoques. Alfileres o impresión por chorro de tinta no va a funcionar, y los dispositivos de microfluidos en 2D no son adecuados para la deposición o la interconexión con grandes conjuntos de puntos discretos. Además, por la miniaturización y la localización de la experimento - el microarray celular - la ACFM supera los principales problemas asociados con ensayos de cribado basados ​​en células de alto rendimiento. El CFM utiliza redes de canal 3D para pequeñas muestras de fluido de volumen de ciclo más de los lugares críticos microscópicos en una superficie de 12,13. Al imprimir con flujo, biomoléculas, células, y otros reactivos se mantienen en un medio líquido durante todo el proceso de impresión, lo que permite la impresión de biomoléculas y células sensibles y sin exposición al aire, lo que dificulta las técnicas de impresión celda actual. También es posible imprimir directamente de material en bruto como hibridoma o sobrenadantes cumpliendo con un mecanismo de captura sobre la superficie de la matriz. El objetivo de este manuscrito es explicar en detalle la impresión sumergida de dos tipos de células sobre una superficie.

<table border="0" cellpadding="0" cellspacing="0" width="571">
	<tbody>
		<tr height="63">
			<td height="63" style="height:63px;width:215px;">Continuous Flow Microspotter</td>
			<td style="width:71px;">Wasatch Microfluidics</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">NIH/3T3 cells</td>
			<td style="width:71px;">ATCC</td>
			<td style="width:119px;">CRL-1658</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Dubbleco&#39;s Modified Eagle Medium</td>
			<td style="width:71px;">Invitrogen</td>
			<td style="width:119px;">11965-092</td>
			<td>base media for cells</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">HEPES buffer</td>
			<td style="width:71px;">Invitrogen</td>
			<td style="width:119px;">15630-080</td>
			<td>cell media additive (control pH)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Sodium pyruvate</td>
			<td style="width:71px;">Invitrogen</td>
			<td style="width:119px;">11360-070</td>
			<td>cell media additive</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Penicillin-Streptomycin&#160;</td>
			<td style="width:71px;">Invitrogen</td>
			<td style="width:119px;"></td>
			<td>cell media additive</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Trypan blue</td>
			<td style="width:71px;">Invitrogen</td>
			<td style="width:119px;">15250-061</td>
			<td>stain cell sfor counting</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Haemocytometer</td>
			<td style="width:71px;">Fisher</td>
			<td align="right" style="width:119px;">267110</td>
			<td>cell chamber to count cells</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Nikon Eclipse TS100</td>
			<td style="width:71px;">Nikon</td>
			<td style="width:119px;"></td>
			<td>Used to check on cells</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Nikon Eclipse TE2000-U</td>
			<td style="width:71px;">Nikon</td>
			<td style="width:119px;"></td>
			<td>Used for collecting images</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Phosphate Buffered Saline (with calcium and magnesium)</td>
			<td style="width:71px;">Invitrogen</td>
			<td style="width:119px;">14040-133</td>
			<td>rinsing cells before passaging and before staining with PI</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">TrypLE Express&#160;</td>
			<td style="width:71px;">Invitrogen</td>
			<td style="width:119px;">A12177-01</td>
			<td>used to remove cells from surface</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;"></td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

the submerged printing of cells onto a modified surface using a continuous flow microspotter

The printing of cells for microarray applications possesses significant challenges including the problem of maintaining physiologically relevant cell phenotype after printing, poor organization and distribution of desired cells, and the inability to deliver drugs and/or nutrients to targeted areas in the array. Our 3D microfluidic printing technology is uniquely capable of sealing and printing arrays of cells onto submerged surfaces in an automated and multiplexed manner. The design of the microfluidic cell array (MFCA) 3D fluidics enables the printhead tip to be lowered into a liquid-filled well or dish and compressed against a surface to form a seal. The soft silicone tip of the printhead behaves like a gasket and is able to form a reversible seal by applying pressure or backing away. Other cells printing technologies such as pin or ink-jet printers are unable to print in submerged applications. Submerged surface printing is essential to maintain phenotypes of cells and to monitor these cells on a surface without disturbing the material surface characteristics. By printing onto submerged surfaces, cell microarrays are produced that allow for drug screening and cytotoxicity assessment in a multitude of areas including cancer, diabetes, inflammation, infections, and cardiovascular disease.

Las células NIH/3T3 línea celular de fibroblastos se imprimieron o sembradas en una superficie sumergida. Las células fueron cultivadas a una densidad de 5 X 10 4 células por ml. Se sembraron las células usando técnicas de cultivo celular tradicionales. Las células se imprimieron utilizando un gran formato, cabezal de impresión de células de doce flujo donde los canales son más grandes (~ 500 micras) que el CFM utilizado para las proteínas y otras biomoléculas. Las células se sembraron impresos o...

Watch this Scientific Journal Video about The Submerged Printing of Cells onto a Modified Surface Using a Continuous Flow Microspotter at JoVE.com

The Submerged Printing of Cells onto a Modified Surface Using a Continuous Flow Microspotter

This 3D microfluidic printing technology prints arrays of cells onto submerged surfaces. We describe how arrays of cells are delivered microfluidically in 3D flow cells onto submerged surfaces. By printing onto submerged surfaces, cell microarrays were produced that allow for drug screening and cytotoxicity assessment in a multitude of areas.

La impresión Sumergido de células sobre una superficie modificada utilizando un flujo continuo Microspotter

The printing of cells for microarray applications possesses significant challenges including the problem of maintaining physiologically relevant cell ...

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JoVE Journal

Bioengineering

8.6K vistas.  Wasatch Microfluidics. This 3D microfluidic printing technology prints arrays of cells onto submerged surfaces. We describe how arrays of cells are delivered microfluidically in 3D flow cells onto submerged surfaces. By printing onto submerged surfaces, cell microarrays were produced that allow for drug screening and cytotoxicity assessment in a multitude of areas.

Video: The Submerged Printing of Cells onto a Modified Surface Using a Continuous Flow Microspotter

Planar and Three-Dimensional Printing of Conductive Inks

Printed electronics rely on low-cost, large-area fabrication routes to create flexible or multidimensional electronic, optoelectronic, and biomedical devices1-3. In this paper, we focus on one- (1D), two- (2D), and three-dimensional (3D) printing of conductive metallic inks in the form of flexible, stretchable, and spanning microelectrodes.
Direct-write assembly4,5 is a 1-to-3D printing technique that enables the fabrication of features ranging from simple lines to complex structures by the deposition of concentrated inks through fine nozzles (~0.1 - 250 &mu;m). This printing method consists of a computer-controlled 3-axis translation stage, an ink reservoir and nozzle, and 10x telescopic lens for visualization. Unlike inkjet printing, a droplet-based process, direct-write assembly involves the extrusion of ink filaments either in- or out-of-plane. The printed filaments typically conform to the nozzle size. Hence, microscale features (&lt; 1 &mu;m) can be patterned and assembled into larger arrays and multidimensional architectures.
In this paper, we first synthesize a highly concentrated silver nanoparticle ink for planar and 3D printing via direct-write assembly. Next, a standard protocol for printing microelectrodes in multidimensional motifs is demonstrated. Finally, applications of printed microelectrodes for electrically small antennas, solar cells, and light-emitting diodes are highlighted.

Planar and three-dimensional printing of conductive metallic inks is described. Our approach provides new avenues for fabricating printed electronic, optoelectronic, and biomedical devices in unusual layouts at the microscale.

Impresión plana y tridimensional de tintas conductoras

Printed electronics rely on low-cost, large-area fabrication routes to create flexible or multidimensional electronic, optoelectronic, and biomedical ...

Investigación

Bioingeniería

Parallel-plate Flow Chamber and Continuous Flow Circuit to Evaluate Endothelial Progenitor Cells under Laminar Flow Shear Stress

The overall goal of this method is to describe a technique to subject adherent cells to laminar flow conditions and evaluate their response to well quantifiable fluid shear stresses1.
Our flow chamber design and flow circuit (Fig. 1) contains a transparent viewing region that enables testing of cell adhesion and imaging of cell morphology immediately before flow (Fig. 11A, B), at various time points during flow (Fig. 11C), and after flow (Fig. 11D). These experiments are illustrated with human umbilical cord blood-derived endothelial progenitor cells (EPCs) and porcine EPCs2,3.
This method is also applicable to other adherent cell types, e.g. smooth muscle cells (SMCs) or fibroblasts.
The chamber and all parts of the circuit are easily sterilized with steam autoclaving. In contrast to other chambers, e.g. microfluidic chambers, large numbers of cells (&gt; 1 million depending on cell size) can be recovered after the flow experiment under sterile conditions for cell culture or other experiments, e.g. DNA or RNA extraction, or immunohistochemistry (Fig. 11E), or scanning electron microscopy5. The shear stress can be adjusted by varying the flow rate of the perfusate, the fluid viscosity, or the channel height and width. The latter can reduce fluid volume or cell needs while ensuring that one-dimensional flow is maintained. It is not necessary to measure chamber height between experiments, since the chamber height does not depend on the use of gaskets, which greatly increases the ease of multiple experiments. Furthermore, the circuit design easily enables the collection of perfusate samples for analysis and/or quantification of metabolites secreted by cells under fluid shear stress exposure, e.g. nitric oxide (Fig. 12)6.

We are describing a method to subject adherent cells to laminar flow shear stress in a sterile continuous flow circuit. The cells' adhesion, morphology can be studied through the transparent chamber, samples obtained from the circuit for metabolite analysis and cells harvested after shear exposure for future experiments or culture.

De placas paralelas de flujo y la Cámara de circuito de flujo continuo para evaluar las células progenitoras endoteliales bajo una tensión cortante de flujo laminar

The overall goal of this method is to describe a technique to subject adherent cells to laminar flow conditions and evaluate their response to well ...

Automated Robotic Dispensing Technique for Surface Guidance and Bioprinting of Cells

This manuscript describes the introduction of cell guidance features followed by the direct delivery of cells to these features in a hydrogel bioink using an automated robotic dispensing system. The particular bioink was selected as it allows cells to sediment towards and sense the features. The dispensing system bioprints viable cells in hydrogel bioinks using a backpressure assisted print head. However, by replacing the print head with a sharpened stylus or scalpel, the dispensing system can also be employed to create topographical cues through surface etching. The stylus movement can be programmed in steps of 10 &#181;m in the X, Y and Z directions. The patterned grooves were able to orientate mesenchymal stem cells, influencing them to adopt an elongated morphology in alignment with the grooves&#39; direction. The patterning could be designed using plotting software in straight lines, concentric circles, and sinusoidal waves. In a subsequent procedure, fibroblasts and mesenchymal stem cells were suspended in a 2% gelatin bioink, for bioprinting in a backpressure driven extrusion printhead. The cell bearing bioink was then printed using the same programmed coordinates used for the etching. The bioprinted cells were able to sense and react to the etched features as demonstrated by their elongated orientation along the direction of the etched grooves.

This protocol describes a bioprinting methodology using an automated robotic depositing system that incorporates etched topographical guidance cues with the precision deposition of a cell bearing hydrogel bioink. The printed cells are directly delivered to the etched features and are able to sense and orientate with them.

Técnica robótica automatizada de dispensación de Orientación de la superficie de las células y Bioprinting

This manuscript describes the introduction of cell guidance features followed by the direct delivery of cells to these features in a hydrogel bioink using ...

Gene Expression Analysis of Endothelial Cells Exposed to Shear Stress Using Multiple Parallel-plate Flow Chambers

We describe a workflow for the analysis of gene expression from endothelial cells subject to a steady laminar flow using multiple monitored parallel-plate flow chambers. Endothelial cells form the inner cellular lining of blood vessels and are chronically exposed to the frictional force of blood flow called shear stress. Under physiological conditions, endothelial cells function in the presence of various shear stress conditions. Thus, the application of shear stress conditions in in vitro models can provide greater insight into endothelial responses in vivo. The parallel-plate flow chamber previously published by Lane et al.9 is adapted to study endothelial gene regulation in the presence and absence of steady (non-pulsatile) laminar flow. Key adaptations in the set-up for laminar flow as presented here include a large, dedicated environment to house concurrent flow circuits, the monitoring of flow rates in real-time, and the inclusion of an exogenous reference RNA for the normalization of quantitative real-time PCR data. To assess multiple treatments/conditions with the application of shear stress, multiple flow circuits and pumps are used simultaneously within the same heated and humidified incubator. The flow rate of each flow circuit is measured continuously in real-time to standardize shear stress conditions throughout the experiments. Because these experiments have multiple conditions, we also use an exogenous reference RNA that is spiked-in at the time of RNA extraction for the normalization of RNA extraction and first-strand cDNA synthesis efficiencies. These steps minimize the variability between samples. This strategy is employed in our pipeline for the gene expression analysis with shear stress experiments using the parallel-plate flow chamber, but parts of this strategy, such as the exogenous reference RNA spike-in, can easily and cost-effectively be used for other applications.

Here, a workflow for the culture and gene expression analysis of endothelial cells under fluid shear stress is presented. Included is a physical arrangement for simultaneously housing and monitoring multiple flow chambers in a controlled environment and the use of an exogenous reference RNA for quantitative PCR.

Análisis de expresión génica de las células endoteliales expuestas a estrés mediante múltiples cámaras de placas paralelas flujo del esquileo

We describe a workflow for the analysis of gene expression from endothelial cells subject to a steady laminar flow using multiple monitored parallel-plate ...

An Automated Method to Perform The In Vitro Micronucleus Assay using Multispectral Imaging Flow Cytometry

The in vitro micronucleus (MN) assay is often used to evaluate cytotoxicity and genotoxicity but scoring the assay via manual microscopy is laborious and introduces uncertainty in results due to variability between scorers. To remedy this, automated slide-scanning microscopy as well as conventional flow cytometry methods have been introduced in an attempt to remove scorer bias and improve throughput. However, these methods have their own inherent limitations such as inability to visualize the cytoplasm of the cell and the lack of visual MN verification or image data storage with flow cytometry. Multispectral Imaging Flow Cytometry (MIFC) has the potential to overcome these limitations. MIFC combines the high resolution fluorescent imagery of microscopy with the statistical robustness and speed of conventional flow cytometry. In addition, all collected imagery can be stored in dose-specific files. This paper describes the protocol developed to perform a fully automated version of the MN assay on MIFC. Human lymphoblastoid TK6 cells were enlarged using a hypotonic solution (75 mM KCl), fixed with 4% formalin and the nuclear content was stained with Hoechst 33342. All samples were run in suspension on the MIFC, permitting acquisition of high resolution images of all key events required for the assay (e.g. binucleated cells with and without MN as well as mononucleated and polynucleated cells). Images were automatically identified, categorized and enumerated in the MIFC data analysis software, allowing for automated scoring of both cytotoxicity and genotoxicity. Results demonstrate that using MIFC to perform the in vitro MN assay allows statistically significant increases in MN frequency to be detected at several different levels of cytotoxicity when compared to solvent controls following exposure of TK6 cells to Mitomycin C and Colchicine, and that no significant increases in MN frequency are observed following exposure to Mannitol.

The in vitro micronucleus assay is a well-established method for evaluating genotoxicity and cytotoxicity but scoring the assay using manual microscopy is laborious and suffers from subjectivity and inter-scorer variability. This paper describes the protocol developed to perform a fully automated version of the assay using multispectral imaging flow cytometry.

Un método automatizado para realizar el ensayo de micronúcleos In Vitro mediante citometría de flujo de imágenes multiespectral

The in vitro micronucleus (MN) assay is often used to evaluate cytotoxicity and genotoxicity but scoring the assay via manual microscopy is laborious and ...

Continuous Measurement of Biological Noise in Escherichia Coli Using Time-lapse Microscopy

The protocol developed here offers a tool to enable computer tracking of Escherichia coli division and fluorescent levels over several hours. The process starts by screening for colonies that survive on minimal media, assuming that only Escherichia coli harboring the correct plasmid will be able to thrive in the specific conditions. Since the process of building large genetic circuits, requiring the assembly of many DNA parts, is challenging, circuit components are often distributed between multiple plasmids at different copy numbers requiring the use of several antibiotics. Mutations in the plasmid can destroy transcription of the antibiotic resistance genes and interject with resources management in the cell leading to necrosis. The selected colony is set on a glass-bottom Petri dish and a few focus planes are selected for microscopy tracking in both bright field and fluorescent domains. The protocol maintains the image focus for more than 12 hours under initial conditions that cannot be regulated, creating a few difficulties. For example, dead cells start to accumulate in the lenses' field of focus after a few hours of imaging, which causes toxins to buildup and the signal to blur and decay. Depletion of nutrients introduces new metabolic processes and hinder the desired response of the circuit. The experiment's temperature lowers the effectivity of inducers and antibiotics, which can further damage the reliability of the signal. The minimal media gel shrinks and dries, and as a result the optical focus changes over time. We developed this method to overcome these challenges in Escherichia coli, similar to previous works developing analogous methods for other micro-organisms. In addition, this method offers an algorithm to quantify the total stochastic noise in unaltered and altered cells, finding that the results are consistent with flow analyzer predictions as shown by a similar coefficient of variation (CV).

Continuous Measurement of Biological Noise in Escherichia Coli Using Time-lapse Microscopy

This work presents a microscopy method that allows live imaging of a single cell of Escherichia coli for analysis and quantification of the stochastic behavior of synthetic gene circuits.

Medición continua del ruido biológico en Escherichia Coli mediante microscopía de lapso de tiempo

The protocol developed here offers a tool to enable computer tracking of Escherichia coli division and fluorescent levels over several hours. The process ...

The Fabrication and Operation of a Continuous Flow, Micro-Electroporation System with Permeabilization Detection

Current therapeutic innovations, such as CAR-T cell therapy, are heavily reliant on viral-mediated gene delivery. Although efficient, this technique is accompanied by high manufacturing costs, which has brought about an interest in using alternative methods for gene delivery. Electroporation is an electro-physical, non-viral approach for the intracellular delivery of genes and other exogenous materials. Upon the application of an electric field, the cell membrane temporarily allows molecular delivery into the cell. Typically, electroporation is performed on the macroscale to process large numbers of cells. However, this approach requires extensive empirical protocol development, which is costly when working with primary and difficult-to-transfect cell types. Lengthy protocol development, coupled with the requirement of large voltages to achieve sufficient electric-field strengths to permeabilize the cells, has led to the development of micro-scale electroporation devices. These micro-electroporation devices are manufactured using common microfabrication techniques and allow for greater experimental control with the potential to maintain high throughput capabilities. This work builds off a microfluidic-electroporation technology capable of detecting the level of cell membrane permeabilization at a single-cell level under continuous flow. However, this technology was limited to 4 cells processed per second, and thus a new approach for increasing the system throughput is proposed and presented here. This new technique, denoted as cell-population-based feedback control, considers the cell permeabilization response to a variety of electroporation pulsing conditions and determines the best-suited electroporation pulse conditions for the cell type under test. A higher-throughput mode is then used, where this 'optimal' pulse is applied to the cell suspension in transit. The steps for fabricating the device, setting up and running the microfluidic experiments, and analyzing the results are presented in detail. Finally, this micro-electroporation technology is demonstrated by delivering a DNA plasmid encoding for green fluorescent protein (GFP) into HEK293 cells.

This protocol describes the microfabrication techniques required to build a lab-on-a-chip, microfluidic electroporation device. The experimental setup performs controlled, single-cell-level transfections in a continuous flow and can be extended to higher throughputs with population-based control. An analysis is provided showcasing the ability to electrically monitor the degree of cell membrane permeabilization in real-time.

La fabricación y operación de un sistema de microelectroporación de flujo continuo con detección de permeabilización

Current therapeutic innovations, such as CAR-T cell therapy, are heavily reliant on viral-mediated gene delivery. Although efficient, this technique is ...

Fabrication of Engineered Vascular Flaps Using 3D Printing Technologies

Engineering implantable, functional, thick tissues requires designing a hierarchical vascular network. 3D bioprinting is a technology used to create tissues by adding layer upon layer of printable biomaterials, termed bioinks, and cells in an orderly and automatic manner, which allows for creating highly intricate structures that traditional tissue engineering techniques cannot achieve. Thus, 3D bioprinting is an appealing in vitro approach to mimic the native vasculature complex structure, ranging from millimetric vessels to microvascular networks. 
Advances in 3D bioprinting in granular hydrogels enabled the high-resolution extrusion of low-viscosity extracellular matrix-based bioinks. This work presents a combined 3D bioprinting and sacrificial mold-based 3D printing approach for fabricating engineered vascularized tissue flaps. 3D bioprinting of endothelial and support cells using recombinant collagen-methacrylate bioink within a gelatin support bath is utilized for the fabrication of a self-assembled capillary network. This printed microvasculature is assembled around a mesoscale vessel-like porous scaffold, fabricated using a sacrificial 3D printed mold, and is seeded with endothelial cells. 
This assembly induces the endothelium of the mesoscale vessel to anastomose with the surrounding capillary network, establishing a hierarchical vascular network within an engineered tissue flap. The engineered flap is then directly implanted by surgical anastomosis to a rat femoral artery using a cuff technique. The described methods can be expanded for the fabrication of various vascularized tissue flaps for use in reconstruction surgery and vascularization studies.

Engineered flaps require an incorporated functional vascular network. In this protocol, we present a method of fabricating a 3D printed tissue flap containing a hierarchical vascular network and its direct microsurgical anastomoses to rat femoral artery.

Fabricación de colgajos vasculares de ingeniería utilizando tecnologías de impresión 3D

Engineering implantable, functional, thick tissues requires designing a hierarchical vascular network. 3D bioprinting is a technology used to create ...

Automation of the Micronucleus Assay Using Imaging Flow Cytometry and Artificial Intelligence

The micronucleus (MN) assay is used worldwide by regulatory bodies to evaluate chemicals for genetic toxicity. The assay can be performed in two ways: by scoring MN in once-divided, cytokinesis-blocked binucleated cells or fully divided mononucleated cells. Historically, light microscopy has been the gold standard method to score the assay, but it is laborious and subjective. Flow cytometry has been used in recent years to score the assay, but is limited by the inability to visually confirm key aspects of cellular imagery. Imaging flow cytometry (IFC) combines high-throughput image capture and automated image analysis, and has been successfully applied to rapidly acquire imagery of and score all key events in the MN assay. Recently, it has been demonstrated that artificial intelligence (AI) methods based on convolutional neural networks can be used to score MN assay data acquired by IFC. This paper describes all steps to use AI software to create a deep learning model to score all key events and to apply this model to automatically score additional data. Results from the AI deep learning model compare well to manual microscopy, therefore enabling fully automated scoring of the MN assay by combining IFC and AI.

The micronucleus (MN) assay is a well-established test for quantifying DNA damage. However, scoring the assay using conventional techniques such as manual microscopy or feature-based image analysis is laborious and challenging. This paper describes the methodology to develop an artificial intelligence model to score the MN assay using imaging flow cytometry data.

Automatización del ensayo de micronúcleos mediante citometría de flujo de imágenes e inteligencia artificial

The micronucleus (MN) assay is used worldwide by regulatory bodies to evaluate chemicals for genetic toxicity. The assay can be performed in two ways: by ...

Caracterización cuantitativa de las propiedades de la biotinta para la impresión DLP continua

Quantitative Characterization of Liquid Photosensitive Bioink Properties for Continuous Digital Light Processing Based Printing

Precise printing fabrication of bioinks is a prerequisite for tissue engineering; the Jacobs working curve is the tool to determine the precise printing parameters of digital light processing (DLP). However, the acquisition of working curves wastes materials and requires high formability of materials, which are not suitable for biomaterials. In addition, the reduction of cell activity due to multiple exposures and the failure of structural formation due to repeated positioning are both unavoidable problems in conventional DLP bioprinting. This work introduces a new method of obtaining the working curve and the improvement process of continuous DLP printing technology based on such a working curve. This method of obtaining the working curve is based on the absorbance and photorheological properties of the biomaterials, which do not depend on the formability of the biomaterials. The continuous DLP printing process, obtained from improving the printing process by analyzing the working curve, increases the printing efficiency more than tenfold and greatly improves the activity and functionality of cells, which is beneficial to the development of tissue engineering.

Autor destacado: Caracterización cuantitativa de las propiedades de la biotinta fotosensible líquida para la impresión basada en el procesamiento digital continuo de la luz  

This study uses temperature and material composition to control the yield stress properties of yield stress fluids. The solid-like state of the ink can protect the printing structure, and the liquid-like state can continuously fill the printing position, realizing the digital light processing 3D printing of extremely soft bioinks.

Caracterización cuantitativa de las propiedades de la biotinta fotosensible líquida para la impresión basada en el procesamiento digital continuo de la luz

Precise printing fabrication of bioinks is a prerequisite for tissue engineering; the Jacobs working curve is the tool to determine the precise printing ...