Les auteurs tiennent à remercier Chris Morrow pour l&#39;assistance technique. Le financement a été fourni par le NIH SBIR (R43) accordent 1R43GM101859-01 (MPI) GRANT10940803.

1. Culture cellulaire Préparation <ol><li> Stocker les stocks de cellules NIH/3T3 dans l&#39;azote liquide jusqu&#39;à utilisation. </li><li> Préparer un milieu complet pour cellules NIH/3T3 à l&#39;aide du milieu Eagle modifié par Dulbecco (DMEM) supplémenté avec 10% de sérum bovin fœtal, 10 mM de tampon HEPES, 50 unités / ml de pénicilline, et 50 pg / ml de streptomycine. </li><li> Décongeler les cellules pour 2-3 min dans un bain d&#39;eau sous agitation à 37 ° C. </li><li> Resuspendre les cellules dans 5 ml de milieu complet et centrifuger à 1500 g pendant 3 min. </li><li> Retirer le surnageant de cellule, sans perturber le culot cellulaire. </li><li> Remettre en suspension les cellules dans 5 ml de milieu et compter les cellules en utilisant un hématimètre. <ol><li> Retirer 10 pi de la suspension cellulaire et le placer dans un tube à centrifuger de 0,5 ml. </li><li> Ajouter 10 ul de bleu trypan à la suspension de cellules et les mélanger avec le bout de la pipette. </li><li> Introduire à la pipette 10 ul de cellules colorées dans une chambre d&#39;hémocytomètre. </li><li> Compter les cellules en hématimètre à 10xgrossissement. <ol><li> Compter les cellules vivantes (petites boules blanches) pour 4 des 9 grands carrés. Compter que les cellules vivantes qui ne semblent pas bleu foncé de la tache bleu Trypan. </li><li> Calculer le nombre moyen de cellules par grande place, résultant du nombre de cellules x 10 4 cellules / ml dans la suspension de cellules d&#39;origine. </li><li> cellules de semences à une densité de 1 x 10 5 cellules / ml avec un total de 5 ml dans chaque flacon T25. </li></ol></li><li> Culture de cellules à entre 70% et 80% de confluence avant commençant expériences. Actualiser les médias tous les 2-3 jours ou au besoin. </li></ol></li></ol> 2. Impression Préparation de la surface <ol><li> Marquer un rectangle avec le marqueur sur le fond d&#39;une culture traitée du tissu polystyrène (TCTPS) 12 de la plaque ainsi la taille de la tête d&#39;impression (7 mm x 19 mm). </li><li> Ajouter 50 ul de sérum de veau foetal dans la zone rectangulaire et l&#39;étaler sur toute la région de la pointe. </li><li> Laissez la boîte de Pétridans un stérile biosécurité capot O / N pour permettre au lieu de sérum sécher complètement. Ces plaques doivent être préparés à pas plus de 2 jours avant l&#39;utilisation. </li></ol> 3. Impression immergé <ol><li> Rincer la tête d&#39;impression avec de l&#39;eau distillée. <ol><li> Remplissez une boîte de Pétri de 60 mm avec de l&#39;eau distillée et ancrer la tête d&#39;impression sur la surface. </li><li> Couler de l&#39;eau distillée à travers chacune des lignes pendant 2 minutes à 150 pl / min en utilisant une pompe pneumatique. </li><li> Jeter l&#39;eau de la boîte de Pétri et le remplir avec de l&#39;eau propre. </li><li> Déplacez la tête d&#39;impression de haut en bas dans l&#39;eau 3 fois. </li></ol></li><li> Ancrer le centre de la tête d&#39;impression sur la place de sérum revêtue de la plaque 12 et pré-établi. </li><li> Amorcer le tête d&#39;impression avec les médias complets pré-chauffées, 300 pl par canal. </li><li> Imprimer des cellules en suspension à une concentration de 50 000 cellules / ml sur la surface et 60 ul / min, 100 ul par canal. </li><li> Placez la tête d&#39;impression, à gauche amarré contre lasurface, et le collecteur dans un incubateur de culture cellulaire défini à 5% de CO 2 et 37 ° C pendant 2 heures. </li><li> Après l&#39;incubation de 2 heures, retirer la tête d&#39;impression et placez le couvercle sur la boîte de culture. Le moment où la tête d&#39;impression retirée est considéré comme le point de temps 0 h. </li></ol> 4. Portable standard Culture <ol><li> Ajouter 1 ml de milieu préchauffées à une de la plaque TCTPS 12 puits de sérum repéré préparé à l&#39;étape 2. </li><li> Prélever 1 ml de la suspension cellulaire restant de l&#39;étape 2 à la pipette dans un seul puits d&#39;une 12 bien TCTPS plaque. Ceci va produire une culture contenant 50 000 cellules dans le plat. </li><li> Placer la plaque de culture de cellules dans un incubateur à 37 ° C pendant 2 heures. </li><li> Après l&#39;incubation de 2 h commencer le chronométrage; la cohérence entre les échantillons imprimés et semis, cela est considéré comme le point de temps 0 h. </li></ol> 5. Culture Visualisation <ol><li> Après 0, 2, 24, et 48 h cellules de prendre de chacune des deux méthodes described ci-dessus et de l&#39;image en utilisant un microscope inversé standard. <ol><li> Colorer les cellules en utilisant l&#39;iodure de propidium, un colorant fluorescent rouge qui est seulement incorporée dans le noyau des cellules mortes. <ol><li> Rincer délicatement les cellules 3 fois avec 1 ml de tampon phosphate salin avec le calcium et le magnésium (PBS + +) pour enlever les débris. </li><li> Ajouter 1 ml de PBS + + préchauffée à chaque récipient de culture. </li><li> Ajouter 1 ul d&#39;une solution d&#39;iodure de propidium stock (1 mg / ml) pour chaque récipient de culture. </li><li> Incuber les cellules colorées avec de l&#39;iodure de propidium à 37 ° C pendant 10 min. </li></ol></li><li> L&#39;image des cellules en utilisant un microscope inversé à 10x et 40x. </li></ol></li><li> Jeter les cellules dans un container prévu appropriée. </li></ol>

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Les auteurs sont des employés et actionnaires de Wasatch microfluidique qui produit des réactifs et / ou des instruments utilisés dans ce manuscrit.

La technologie d&#39;impression 3D microfluidique décrit ici est le seul à pouvoir impression microfluidically réseaux de cellules dans un liquide bien remplie, c&#39;est à dire une surface immergée. En imprimant sur ​​les surfaces immergées, puces à cellules peuvent être produites qui maintiennent le phénotype cellulaire physiologiquement pertinente de cellules ainsi que la possibilité de multiplexer les cellules dans le fond d&#39;un puits unique figure 4. Les résultats de cett...

Les progrès récents dans l&#39;industrie pharmaceutique ont conduit à un intérêt accru pour l&#39;aide puces cellulaires dans le processus de découverte de médicaments pour le dépistage des drogues et de l&#39;analyse cytotoxicological 1,2,3. Le développement de tests in vitro à haut débit et les méthodes de dépistage à l&#39;aide de puces à cellules devrait faciliter le développement rapide et rentable de candidats-médicaments ainsi que l&#39;avance la compréhension fondamentale de la cellule 1,4. L&#39;approche traditionnelle de dépistage avec des cellules utilise des plates-formes et de plaques conventionnelles; Cependant cette approche est limitée en raison du coût élevé, le débit limité, et la capacité limitée d&#39;informations quantitatives sur la fonction des cellules 1,5. En raison de ces limitations, la recherche dans les technologies de puces à ADN cellulaire est en plein essor pour la caractérisation moléculaire biologique, l&#39;ingénierie tissulaire, et le dépistage de drogue 1,6. Les avantages de puces cellulaires comprennent l&#39;utilisation réduite de l&#39;échantillon, des effets minimes dephénotype cellulaire hétérogénéité masquage des informations, et surtout la possibilité d&#39;automatiser des tests pour d&#39;autres applications à haut débit 1,7,8. L&#39;industrie pharmaceutique utilise actuellement à haut débit des essais de criblage à base de cellules avec 2D cultures monocouches de cellules pour le criblage de médicaments dans des plaques de microtitration 9. Cellules de multiplexage dans les puits de plaques de microtitration offre la possibilité pour un débit plus élevé avec des options d&#39;expérimentation uniques. En outre, les technologies actuelles de microarrays cellulaires permettent de sécher les cellules, qui pourrait modifier radicalement le phénotype des cellules in vivo à partir de 10,11. Afin de surmonter ces problèmes, le MFCA a été conçu et est représenté sur la figure 1. La conception de la fluidique MFCA 3D permet à la pointe de la tête d&#39;impression sur la figure 1 pour être descendu dans un bain et comprimé contre une surface pour former un joint. La pointe en silicone souple de la tête d&#39;impression se comporte comme unjoint d&#39;étanchéité et forme un joint réversible. La technologie MFCA est particulièrement bien adapté pour l&#39;interface avec les surfaces immergées, qui est nécessaire à la fois pour les cultures de cellules et des systèmes de découpe du tissu, et il est difficile, voire impossible, avec la plupart des autres approches. Pins ou l&#39;impression à jet d&#39;encre ne fonctionnera pas, et des dispositifs microfluidiques 2D ne sont pas adaptés pour le dépôt ou l&#39;interfaçage avec les grands réseaux de points discrets. En outre, par la miniaturisation et la localisation de l&#39;expérience - la puce à ADN cellulaire - la MFCA surmonte les problèmes majeurs associés à haut débit avec des essais de criblage à base de cellules. Le CFM utilise des réseaux de canaux 3D à vélo de petits échantillons de fluide de volume sur les emplacements ponctuels microscopiques sur une surface 12,13. En imprimant avec écoulement, des biomolécules, des cellules, et d&#39;autres réactifs sont maintenus dans un milieu liquide pendant tout le processus d&#39;impression, ce qui permet l&#39;impression des biomolécules et des cellules sensibles sans exposition à l&#39;air, ce qui empêche les techniques d&#39;impression actuelles de la cellule. Il est également possible d&#39;imprimer directement à partir d&#39;un matériau brut comme hybridome ou surnageants fournis il ya un mécanisme de capture sur la surface du tableau. L&#39;objectif de ce manuscrit est d&#39;expliquer en détail l&#39;impression submergé de deux types de cellules sur une surface.

<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.

Les cellules NIH/3T3 de lignées cellulaires de fibroblastes ont été imprimées ou ensemencées sur une surface immergée. Les cellules ont été cultivées à une densité de 5 x 10 4 cellules par ml. Les cellules ont été ensemencées en utilisant des techniques de culture cellulaire classiques. Les cellules ont été imprimées à l&#39;aide d&#39;un grand format, douze flux de tête d&#39;impression de la cellule où les canaux sont plus grands (~ 500 um) de la CFM utilisé pour des protéines et d&#39...

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.

L&#39;impression submergé de cellules sur une surface modifiée à l&#39;aide d&#39;un flux continu 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 vues.  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.

Vidéo: 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.

Impression Planar et en trois dimensions des encres conductrices

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

Recherche

Bio-ingénierie

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.

Chambre de circulation à plaques parallèles et de circuit d&#39;écoulement continu pour évaluer les cellules progénitrices endothéliales en cisaillement du flux laminaire

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.

Automated Robotic Dispensing Technique d&#39;orientation de surface et Bioprinting de cellules

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.

Analyse de l’Expression génique des cellules endothéliales exposées au Stress à l’aide de plusieurs chambres à plaques parallèles flux de cisaillement

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.

Une méthode automatisée pour effectuer l'essai micronutrique in vitro à l'aide de la cytométrie du flux d'imagerie multispectrale

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.

Mesure continue du bruit biologique chez Escherichia Coli à l’aide d’une microscopie en accéléré

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 fabrication et l’exploitation d’un système de micro-électroporation à flux continu avec détection de perméabilisation

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.

Fabrication de volets vasculaires artificiels à l’aide de technologies d’impression 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.

Automatisation du test du micronoyau à l’aide de la cytométrie en flux d’imagerie et de l’intelligence artificielle

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 ...

Caractérisation quantitative des propriétés des bio-encres pour l’impression DLP en continu

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.

Pleins feux sur l’auteur : Caractérisation quantitative des propriétés de bio-encre photosensibles liquides pour l’impression basée sur le traitement numérique continu de la lumière  

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.

Caractérisation quantitative des propriétés de bio-encre photosensible liquide pour l’impression numérique continue basée sur le traitement de la lumière

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