This study was supported by a Singapore National Research Foundation (NRF) Grant NRF2012NRF-POC001-043.

1. Fabrication du masque <ol><li> Nettoyer une tranche 4 &quot;de verre avec une solution piranha (H 2 SO 4 / H 2 O 2 à 2: 1) pendant 20 min à 120 ° C par immersion dans une cuve en quartz. </li><li> Déposer une couche de chrome / or (30 nm de Cr / Au de 1 um) sur la couche de la plaquette de verre en utilisant un faisceau d&#39;électrons évaporateur 7 (figure 1A). <ol><li> Placez les tranches dans un évaporateur à faisceau électronique. Une fois que le vide atteint 5 x 10 -6 Torr, allumer la source de haute tension (10 kV). Contrôler l&#39;épaisseur par le panneau de contrôle du moniteur. </li><li> Pré-propre chaque matériau pendant 30 secondes à l&#39;aide du canon à faisceau d&#39;électrons, en maintenant l&#39;obturateur &quot;OFF&quot; (afin d&#39;éviter le dépôt sur les plaquettes). </li></ol></li><li> Générer une couche Cr / Au résine photosensible de masquage pour gravure humide profonde du verre. <ol><li> Appliquer une résine photosensible épaisse 2 pm par filage 5 ml de la solution pendant 30 secondes à 3000 tours par minute en utilisant un système de couchage spin-pulvérisation.Précuisson de la résine photosensible sur une plaque chauffante à 100 ° C pendant 1,5 min. </li><li> Exposer et faire cuire dur la résine photosensible à 120 ° C pendant 30 min sur une plaque chauffante. Il est essentiel de produire une surface hydrophobe et une forte adhérence de la résine photosensible sur la couche de métal. Motif de la couche de Cr / Au utilisant Cr et Au décapants à travers la résine photosensible masque 8,9. </li></ol></li><li> Pour la protection de la surface de verre non à motifs, lier temporairement la plaquette de verre à une plaquette de silicium factice. 9 <ol><li> Placer la plaque de verre sur une plaque chaude à 110 ° C et faire fondre la cire sur le côté opposé de la plaque de verre (d&#39;une manière telle que toute la surface de la plaquette est recouverte avec de la cire). </li><li> Placez une tranche de silicium mannequin en contact avec la plaquette de verre et appuyez sur pour enlever la cire excès. Afin d&#39;éviter de renverser de la cire, placez un papier tissu de salle blanche sur la plaque chauffante. </li></ol></li><li> Effectuer une gravure isotrope de la lentille au moyen d&#39;acide fluorhydrique optimisé (49% v / v)et de l&#39;acide chlorhydrique (37% v / v) de solution (dans un rapport volumétrique de 10: 1). avec un agitateur magnétique pendant 10 min 8,5 Présence du HCl est essentiel pour parvenir à une bonne qualité de surface des lentilles produites de. <ol><li> Assurez-vous que la vitesse de gravure est de 7 pm / min; en utilisant un volume total de 200 ml de solution de gravure. Effectuer gravure dans un récipient en plastique et de prendre les précautions de sécurité pour cette étape de traitement. </li><li> Nettoyez la galette dans la (DI) de l&#39;eau déminéralisée d&#39;un rinçage et un séchage supplémentaire à la température ambiante. </li></ol></li><li> Après l&#39;achèvement du procédé, de séparer la tranche de verre à partir de la tranche de silicium factice et réchauffer la cire en utilisant une plaque chaude à 100 ° C pendant 15 s. Comme la cire fond à cette température, détacher la tranche de verre à partir de la tranche de silicium factice. </li><li> Retirer le reste de la cire, la résine photosensible et le surplomb Cr / Au couches sur les bords de la lentille en utilisant ultrasonication pendant 1 heure en utilisant du N-méthyl-2-pyrrolidone comme solvant à 80 ° C dans une cuve à ultrasons.</li><li> Créer un moule PDMS réplique des microlentilles fabriquées sur les photomasques 11. </li><li> Caractériser les dimensions de photomasques (longueur et largeur) et le moule microlentilles PDMS (profondeur et le diamètre) des répliques en utilisant un microscope électronique à balayage et stéréomicroscope respectivement. 12-14 </li></ol> 2. Arbres MN Fabrication <ol><li> Créer une cavité de 2,5 cm x 0,9 cm à l&#39;aide des lames de verre montées de part et d&#39;autre d&#39;un verre. Le nombre des lames de verre empilées part et d&#39;autre détermine la hauteur de la cavité dite épaisseur d&#39;espacement (figure 1B). </li><li> Fixer chaque couche de la lame de verre par application d&#39;une mince couche de la solution de prépolymère contenant du poly (éthylène glycol) diacrylate (PEGDA, MW = 258 Da) avec 0,5% en poids / poids de 2-hydroxy-2-méthyl-propiophénone (HMP) sur la lame de verre suivie d&#39;une irradiation de la lumière mis en place avec l&#39;ultraviolet de haute intensité (UV) pendant 2 secondes. </li><li> Placez le Photomask (fabriqué précédemment) avec les surfaces de Cr / Au revêtus face à l&#39;intérieur de la cavité. Faire en sorte que les côtés des parois de la cavité ne sont pas obscurcir la lentilles noyées dans le photomasque. </li><li> Remplir la cavité avec la solution de prépolymère jusqu&#39;à ce que la surface revêtue Cr / Au est en contact avec la solution sans bulles visibles. </li><li> Irradier la configuration à haute intensité de la lumière UV d&#39;une intensité souhaitée pendant 1 s à une distance de 3,5 cm de la source UV en utilisant la station de séchage UV avec une gamme de filtre UV de 320-500 nm. Utilisez un adaptateur collimateur avec la sonde de la lumière UV. </li><li> Mesurer l&#39;intensité de la lumière UV utilisée en utilisant un radiomètre. </li><li> Suite à l&#39;exposition aux UV, retirer le photomasque avec le tableau de MNs. Verser la solution de prépolymère en excès qui est polymérisé pas dans le processus de retour dans son emballage d&#39;origine pour une réutilisation. </li><li> Quantifier le diamètre des MNs l&#39;aide d&#39;un microscope stéréoscopique selon les instructions du fabricant longueur ni les pourboires. </li></ol><pclass = &quot;jove_title&quot;&gt; 3. MN Fabrication Sauvegarde de la Couche <ol><li> Avec une pince, placer les MNs (fabriqué précédemment) fixé sur le photomasque dans un puits d&#39;une plaque à 24 puits comme indiqué dans la Figure 1C. </li><li> Ajouter un volume donné (300 - 400 pi) de la solution de prépolymère dans le puits jusqu&#39;à ce que les aiguilles sont immergées à une hauteur désirée. Ce volume détermine l&#39;épaisseur de la couche de support qui en résulte. </li><li> Irradier la configuration de lumière de haute intensité UV (15,1 W / cm 2), à une distance de 10,5 cm de la source d&#39;UV pour une durée de 1 sec. </li><li> Séparer la couche de support sur le tableau MN du photomasque utilisant une lame tranchante. </li><li> Quantifier le diamètre longueur, le diamètre et la base pointe des MNs avec la couche de support en utilisant un stéréomicroscope selon les instructions du fabricant. </li></ol>

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The authors declare no conflict of Interest.

Le protocole décrit ci-dessus pour la fabrication de la matrice MNs a été présenté pour la fabrication de la matrice de MNs ~ 1 cm 2. Les réseaux peuvent être mis à l&#39;échelle par la création d&#39;une cavité de grande taille et en utilisant un photomasque plus grande. L&#39;augmentation de la taille de la cavité peut être créée par l&#39;augmentation de la largeur entre les entretoises de chaque côté. Bien que chaque étape pour fabriquer les tableaux de Mn dans le protocole était import...

Administration transdermique de médicament offre une approche alternative intéressante pour l&#39;administration de médicaments, en particulier pour les biomolécules, qui sont presque exclusivement administrés par injections hypodermiques. Cependant, la peau, en particulier la couche supérieure (la couche cornée), est une formidable barrière empêchant molécules exogènes de pénétrer dans le corps humain. Récemment, des dispositifs MN ont émergé comme des outils permettant de livrer des médicaments à travers la peau. Les dispositifs de MN créer des pores temporaires à l&#39;intérieur de la couche cornée pour permettre le passage de molécules de médicament d&#39;atteindre l&#39;activité physiologique désirée avec une meilleure observance des patients et la commodité 1-3. Diverses méthodes de fabrication ont été adoptées pour fabriquer des polymères MNs 4. Cependant, ils impliquent généralement des processus étape complexes et multiples nécessitant des temps longs et / ou des températures élevées pour fabriquer des réseaux MNS. 4 Pour simplifier le processus de fabrication, un processus libre de moule en une seule étape à l&#39;aideun photomasque a été développé récemment 5,6. Cependant, avec cette méthode, fabriqué MNs avaient pointes d&#39;aiguilles émoussées, comme aucun mécanisme n&#39;a été mis en place pour modifier le chemin ultraviolet (UV) impliqués dans la photolithographie. Dans cette étude, des microlentilles intégrées dans le photomasque ont été proposées pour définir la géométrie des MNs. Le protocole de fabriquer des masques constitués de microlentilles embarqués et ensuite mn fabrication avec des conseils pointus en utilisant le photomasque sont signalés.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Poly(ethylene glycol) diacrylate (PEGDA Mn=258)</td>
			<td>SIGMA&#160;</td>
			<td>475629-500ML</td>
			<td></td>
		</tr>
		<tr>
			<td>2-hydroxy-2-methyl-propiophenone (HMP)</td>
			<td>SIGMA&#160;</td>
			<td>405655-50ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine collagen type 1, FITC conjugate&#160;</td>
			<td>SIGMA&#160;</td>
			<td>C4361</td>
			<td></td>
		</tr>
		<tr>
			<td>UV curing station&#160;&#160;&#160;</td>
			<td>EXFO Photonic Solutions Inc., Canada</td>
			<td>OmniCure S200-XL</td>
			<td></td>
		</tr>
		<tr>
			<td>Collimating Adaptor&#160;</td>
			<td>EXFO Photonic Solutions Inc., Canada</td>
			<td>EXFO 810-00042</td>
			<td></td>
		</tr>
		<tr>
			<td>24-well plate</td>
			<td>Thermo Fisher Scientific, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Nikon SMZ 1500 stereomicroscope&#160;</td>
			<td>Nikon, Japan</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dillon GL-500 digital force gauge&#160;</td>
			<td>Dillon, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>A-1R confocal microscope&#160;</td>
			<td>Nikon, Japan</td>
			<td></td>
			<td></td>
		</tr>
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			<td></td>
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</table>

polymeric microneedle array fabrication by photolithography

Ce manuscrit décrit la fabrication de micro-aiguilles polymère (MN) tableaux par photolithographie. Elle implique un processus libre de moule simple en utilisant un photomasque constitué de micro-lentilles embarqués. Micro-lentilles embarqués ont influencé la géométrie MN (netteté). Tableaux MN robustes avec des diamètres de pointe allant de 41,5 ± 8,4 um um et 71,6 um ± 13,7 pm, avec deux longueurs différentes (1 336 um ± 193 um et 957 um ± 171 um) ont été fabriqués. Ces tableaux de MN peuvent fournir des applications potentielles dans la livraison d&#39;agents thérapeutiques moléculaire et macromoléculaire bas à travers la peau.

La géométrie des MNs peut être significativement affectée par les caractéristiques de photomasques et microlentille embarqués. Le degré de réfraction affecte le trajet de transmission des rayons UV, qui ont influencé la géométrie de MN (figure 2A). Chaque microlentille a été trouvé pour avoir un diamètre de 350 um, 130 um aplatis une surface convexe, et une profondeur de 62,3 um (figure 2B-D). En utilisant le théorème de Pythagore, le rayon de courbure de la première s...

Watch this Scientific Journal Video about Polymeric Microneedle Array Fabrication by Photolithography at JoVE.com

Polymeric Microneedle Array Fabrication by Photolithography

Here, we present a protocol describing a mold-free fabrication process of the polymeric microneedles by photolithography.

Polymère Microneedle tableau Fabrication par photolithographie

This manuscript describes the fabrication of polymeric microneedle (MN) arrays by photolithography. It involves a simple mold-free process by using a ...

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Bioengineering

11.9K vues.  National University of Singapore. Here, we present a protocol describing a mold-free fabrication process of the polymeric microneedles by photolithography. 

Vidéo: Polymeric Microneedle Array Fabrication by Photolithography

Fabrication of Micropatterned Hydrogels for Neural Culture Systems using Dynamic Mask Projection Photolithography

Increasingly, patterned cell culture environments are becoming a relevant technique to study cellular characteristics, and many researchers believe in the need for 3D environments to represent in vitro experiments which better mimic in vivo qualities 1-3. Studies in fields such as cancer research 4, neural engineering 5, cardiac physiology 6, and cell-matrix interaction7,8have shown cell behavior differs substantially between traditional monolayer cultures and 3D constructs.
Hydrogels are used as 3D environments because of their variety, versatility and ability to tailor molecular composition through functionalization 9-12. Numerous techniques exist for creation of constructs as cell-supportive matrices, including electrospinning13, elastomer stamps14, inkjet printing15, additive photopatterning16, static photomask projection-lithography17, and dynamic mask microstereolithography18. Unfortunately, these methods involve multiple production steps and/or equipment not readily adaptable to conventional cell and tissue culture methods. The technique employed in this protocol adapts the latter two methods, using a digital micromirror device (DMD) to create dynamic photomasks for crosslinking geometrically specific poly-(ethylene glycol) (PEG) hydrogels, induced through UV initiated free radical polymerization. The resulting "2.5D" structures provide a constrained 3D environment for neural growth. We employ a dual-hydrogel approach, where PEG serves as a cell-restrictive region supplying structure to an otherwise shapeless but cell-permissive self-assembling gel made from either Puramatrix or agarose. The process is a quick simple one step fabrication which is highly reproducible and easily adapted for use with conventional cell culture methods and substrates.
Whole tissue explants, such as embryonic dorsal root ganglia (DRG), can be incorporated into the dual hydrogel constructs for experimental assays such as neurite outgrowth. Additionally, dissociated cells can be encapsulated in the photocrosslinkable or self polymerizing hydrogel, or selectively adhered to the permeable support membrane using cell-restrictive photopatterning. Using the DMD, we created hydrogel constructs up to ~1mm thick, but thin film (&lt;200 &mu;m) PEG structures were limited by oxygen quenching of the free radical polymerization reaction. We subsequently developed a technique utilizing a layer of oil above the polymerization liquid which allowed thin PEG structure polymerization.
In this protocol, we describe the expeditious creation of 3D hydrogel systems for production of microfabricated neural cell and tissue cultures. The dual hydrogel constructs demonstrated herein represent versatile in vitro models that may prove useful for studies in neuroscience involving cell survival, migration, and/or neurite growth and guidance. Moreover, as the protocol can work for many types of hydrogels and cells, the potential applications are both varied and vast.

Simple techniques are described for the rapid production of microfabricated neural culture systems using a digital micromirror device for dynamic mask projection lithography on regular cell culture substrates. These culture systems may be more representative of natural biological architecture, and the techniques described could be adapted for numerous applications.

Fabrication d&#39;hydrogels pour les systèmes de culture Micropatterned neuronaux utilisant la photolithographie dynamique projection de masque

Increasingly, patterned cell culture environments are becoming a relevant technique to study cellular characteristics, and many researchers believe in the ...

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Bio-ingénierie

Formulation of Diblock Polymeric Nanoparticles through Nanoprecipitation Technique

Nanotechnology is a relatively new branch of science that involves harnessing the unique properties of particles that are nanometers in scale (nanoparticles). Nanoparticles can be engineered in a precise fashion where their size, composition and surface chemistry can be carefully controlled. This enables unprecedented freedom to modify some of the fundamental properties of their cargo, such as solubility, diffusivity, biodistribution, release characteristics and immunogenicity. Since their inception, nanoparticles have been utilized in many areas of science and medicine, including drug delivery, imaging, and cell biology1-4. However, it has not been fully utilized outside of "nanotechnology laboratories" due to perceived technical barrier. In this article, we describe a simple method to synthesize a polymer based nanoparticle platform that has a wide range of potential applications. 
The first step is to synthesize a diblock co-polymer that has both a hydrophobic domain and hydrophilic domain. Using PLGA and PEG as model polymers, we described a conjugation reaction using EDC/NHS chemistry5 (Fig 1). We also discuss the polymer purification process. The synthesized diblock co-polymer can self-assemble into nanoparticles in the nanoprecipitation process through hydrophobic-hydrophilic interactions.
The described polymer nanoparticle is very versatile. The hydrophobic core of the nanoparticle can be utilized to carry poorly soluble drugs for drug delivery experiments6. Furthermore, the nanoparticles can overcome the problem of toxic solvents for poorly soluble molecular biology reagents, such as wortmannin, which requires a solvent like DMSO. However, DMSO can be toxic to cells and interfere with the experiment. These poorly soluble drugs and reagents can be effectively delivered using polymer nanoparticles with minimal toxicity. Polymer nanoparticles can also be loaded with fluorescent dye and utilized for intracellular trafficking studies. Lastly, these polymer nanoparticles can be conjugated to targeting ligands through surface PEG. Such targeted nanoparticles can be utilized to label specific epitopes on or in cells7-10.

This article describes a nanoprecipitation method to synthesize polymer-based nanoparticles using diblock co-polymers. We will discuss the synthesis of diblock co-polymers, the nanoprecipitation technique, and potential applications.

Formulation de nanoparticules polymériques dibloc par la technique nanoprécipitation

Nanotechnology is a relatively new branch of science that involves harnessing the unique properties of particles that are nanometers in scale ...

Hollow Microneedle-based Sensor for Multiplexed Transdermal Electrochemical Sensing

The development of a minimally invasive multiplexed monitoring system for rapid analysis of biologically-relevant molecules could offer individuals suffering from chronic medical conditions facile assessment of their immediate physiological state. Furthermore, it could serve as a research tool for analysis of complex, multifactorial medical conditions. In order for such a multianalyte sensor to be realized, it must be minimally invasive, sampling of interstitial fluid must occur without pain or harm to the user, and analysis must be rapid as well as selective.
Initially developed for pain-free drug delivery, microneedles have been used to deliver vaccines and pharmacologic agents (e.g., insulin) through the skin.1-2 Since these devices access the interstitial space, microneedles that are integrated with microelectrodes can be used as transdermal electrochemical sensors. Selective detection of glucose, glutamate, lactate, hydrogen peroxide, and ascorbic acid has been demonstrated using integrated microneedle-electrode devices with carbon fibers, modified carbon pastes, and platinum-coated polymer microneedles serving as transducing elements.3-7,8
This microneedle sensor technology has enabled a novel and sophisticated analytical approach for in situ and simultaneous detection of multiple analytes. Multiplexing offers the possibility of monitoring complex microenvironments, which are otherwise difficult to characterize in a rapid and minimally invasive manner. For example, this technology could be utilized for simultaneous monitoring of extracellular levels of, glucose, lactate and pH,9 which are important metabolic indicators of disease states7,10-14 (e.g., cancer proliferation) and exercise-induced acidosis.15

This article details the construction of a multiplexed microneedle-based sensor. The device is being developed for in situ sampling and electrochemical analysis of multiple analytes in a rapid and selective manner. We envision clinical medicine and biomedical research uses for these microneedle-based sensors.

MICRO-creux à base de capteur pour multiplexée transdermique Sensing électrochimique

The development of a minimally invasive multiplexed monitoring system for rapid analysis of biologically-relevant molecules could offer individuals ...

Evaluation of Polymeric Gene Delivery Nanoparticles by Nanoparticle Tracking Analysis and High-throughput Flow Cytometry

Non-viral gene delivery using polymeric nanoparticles has emerged as an attractive approach for gene therapy to treat genetic diseases1 and as a technology for regenerative medicine2. Unlike viruses, which have significant safety issues, polymeric nanoparticles can be designed to be non-toxic, non-immunogenic, non-mutagenic, easier to synthesize, chemically versatile, capable of carrying larger nucleic acid cargo and biodegradable and/or environmentally responsive. Cationic polymers self-assemble with negatively charged DNA via electrostatic interaction to form complexes on the order of 100 nm that are commonly termed polymeric nanoparticles. Examples of biomaterials used to form nanoscale polycationic gene delivery nanoparticles include polylysine, polyphosphoesters, poly(amidoamines)s and polyethylenimine (PEI), which is a non-degradable off-the-shelf cationic polymer commonly used for nucleic acid delivery1,3 . Poly(beta-amino ester)s (PBAEs) are a newer class of cationic polymers4 that are hydrolytically degradable5,6 and have been shown to be effective at gene delivery to hard-to-transfect cell types such as human retinal endothelial cells (HRECs)7, mouse mammary epithelial cells8, human brain cancer cells9 and macrovascular (human umbilical vein, HUVECs) endothelial cells10.
A new protocol to characterize polymeric nanoparticles utilizing nanoparticle tracking analysis (NTA) is described. In this approach, both the particle size distribution and the distribution of the number of plasmids per particle are obtained11. In addition, a high-throughput 96-well plate transfection assay for rapid screening of the transfection efficacy of polymeric nanoparticles is presented. In this protocol, poly(beta-amino ester)s (PBAEs) are used as model polymers and human retinal endothelial cells (HRECs) are used as model human cells. This protocol can be easily adapted to evaluate any polymeric nanoparticle and any cell type of interest in a multi-well plate format.

A protocol for nanoparticle tracking analysis (NTA) and high-throughput flow cytometry to evaluate polymeric gene delivery nanoparticles is described. NTA is utilized to characterize the nanoparticle particle size distribution and the plasmid per particle distribution. High-throughput flow cytometry enables quantitative transfection efficacy evaluation for a library of gene delivery biomaterials.

Évaluation de livraison Gene polymère nanoparticules d&#39;analyse de suivi par des nanoparticules et de cytométrie en flux à haut débit

Non-viral gene delivery using polymeric nanoparticles has emerged as an attractive approach for gene therapy to treat genetic diseases1 and as a ...

Microfluidic Fabrication of Polymeric and Biohybrid Fibers with Predesigned Size and Shape

A &#8220;sheath&#8221; fluid passing through a microfluidic channel at low Reynolds number can be directed around another &#8220;core&#8221; stream and used to dictate the shape as well as the diameter of a core stream.&#160;Grooves in the top and bottom of a microfluidic channel were designed to direct the sheath fluid and shape the core fluid.&#160;By matching the viscosity and hydrophilicity of the sheath and core fluids, the interfacial effects are minimized and complex fluid shapes can be formed.&#160;Controlling the relative flow rates of the sheath and core fluids determines the cross-sectional area of the core fluid.&#160;Fibers have been produced with sizes ranging from 300 nm to ~1 mm, and fiber cross-sections can be round, flat, square, or complex as in the case with double anchor fibers. Polymerization of the core fluid downstream from the shaping region solidifies the fibers.&#160;Photoinitiated click chemistries are well suited for rapid polymerization of the core fluid by irradiation with ultraviolet light.&#160;Fibers with a wide variety of shapes have been produced from a list of polymers including liquid crystals, poly(methylmethacrylate), thiol-ene and thiol-yne resins, polyethylene glycol, and hydrogel derivatives. Minimal shear during the shaping process and mild polymerization conditions also makes the fabrication process well suited for encapsulation of cells and other biological components.

Two adjacent fluids passing through a grooved microfluidic channel can be directed to form a sheath around a prepolymer core; thereby&#160;determining both shape and cross-section. Photoinitiated polymerization, such as thiol click chemistry, is well suited for rapidly solidifying the core fluid into a microfiber with predetermined size and shape.

Fabrication microfluidique de fibres polymères et biohybrides avec une taille et une forme redessinées

A &#8220;sheath&#8221; fluid passing through a microfluidic channel at low Reynolds number can be directed around another &#8220;core&#8221; stream and ...

Biomembrane Fabrication by the Solvent-assisted Lipid Bilayer (SALB) Method

In order to mimic cell membranes, the supported lipid bilayer (SLB) is an attractive platform which enables in vitro investigation of membrane-related processes while conferring biocompatibility and biofunctionality to solid substrates. The spontaneous adsorption and rupture of phospholipid vesicles is the most commonly used method to form SLBs. However, under physiological conditions, vesicle fusion (VF) is limited to only a subset of lipid compositions and solid supports. Here, we describe a one-step general procedure called the solvent-assisted lipid bilayer (SALB) formation method in order to form SLBs which does not require vesicles. The SALB method involves the deposition of lipid molecules onto a solid surface in the presence of water-miscible organic solvents (e.g., isopropanol) and subsequent solvent-exchange with aqueous buffer solution in order to trigger SLB formation. The continuous solvent exchange step enables application of the method in a flow-through configuration suitable for monitoring bilayer formation and subsequent alterations using a wide range of surface-sensitive biosensors. The SALB method can be used to fabricate SLBs on a wide range of hydrophilic solid surfaces, including those which are intractable to vesicle fusion. In addition, it enables fabrication of SLBs composed of lipid compositions which cannot be prepared using the vesicle fusion method. Herein, we compare results obtained with the SALB and conventional vesicle fusion methods on two illustrative hydrophilic surfaces, silicon dioxide and gold. To optimize the experimental conditions for preparation of high quality bilayers prepared via the SALB method, the effect of various parameters, including the type of organic solvent in the deposition step, the rate of solvent exchange, and the lipid concentration is discussed along with troubleshooting tips. Formation of supported membranes containing high fractions of cholesterol is also demonstrated with the SALB method, highlighting the technical capabilities of the SALB technique for a wide range of membrane configurations.

Biomembrane Fabrication by the Solvent-assisted Lipid Bilayer SALB Method

We present an experimental protocol to form a supported lipid bilayer on solid substrates without using lipid vesicles. We demonstrate a one-step method to form a lipid bilayer on silicon dioxide and gold as well as supported membranes with cholesterol-enriched domain for various biological applications.

Biomembrane Fabrication par le solvant assistée bicouche lipidique (SALB) Méthode

In order to mimic cell membranes, the supported lipid bilayer (SLB) is an attractive platform which enables in vitro investigation of membrane-related ...

Fabricating Superhydrophobic Polymeric Materials for Biomedical Applications

Superhydrophobic materials, with surfaces possessing permanent or metastable non-wetted states, are of interest for a number of biomedical and industrial applications. Here we describe how electrospinning or electrospraying a polymer mixture containing a biodegradable, biocompatible aliphatic polyester (e.g., polycaprolactone and poly(lactide-co-glycolide)), as the major component, doped with a hydrophobic copolymer composed of the polyester and a stearate-modified poly(glycerol carbonate) affords a superhydrophobic biomaterial. The fabrication techniques of electrospinning or electrospraying provide the enhanced surface roughness and porosity on and within the fibers or the particles, respectively. The use of a low surface energy copolymer dopant that blends with the polyester and can be stably electrospun or electrosprayed affords these superhydrophobic materials. Important parameters such as fiber size, copolymer dopant composition and/or concentration, and their effects on wettability are discussed. This combination of polymer chemistry and process engineering affords a versatile approach to develop application-specific materials using scalable techniques, which are likely generalizable to a wider class of polymers for a variety of applications.

Two- and three-dimensional superhydrophobic polymeric materials are prepared by electrospinning or electrospraying biodegradable polymers blended with a lower surface energy polymer of similar composition.

Superhydrophobes fabrication de matériaux polymères pour des applications biomédicales

Superhydrophobic materials, with surfaces possessing permanent or metastable non-wetted states, are of interest for a number of biomedical and industrial ...

Multi-step Variable Height Photolithography for Valved Multilayer Microfluidic Devices

Microfluidic systems have enabled powerful new approaches to high-throughput biochemical and biological analysis. However, there remains a barrier to entry for non-specialists who would benefit greatly from the ability to develop their own microfluidic devices to address research questions. Particularly lacking has been the open dissemination of protocols related to photolithography, a key step in the development of a replica mold for the manufacture of polydimethylsiloxane (PDMS) devices. While the fabrication of single height silicon masters has been explored extensively in literature, fabrication steps for more complicated photolithography features necessary for many interesting device functionalities (such as feature rounding to make valve structures, multi-height single-mold patterning, or high aspect ratio definition) are often not explicitly outlined. 
Here, we provide a complete protocol for making multilayer microfluidic devices with valves and complex multi-height geometries, tunable for any application. These fabrication procedures are presented in the context of a microfluidic hydrogel bead synthesizer and demonstrate the production of droplets containing polyethylene glycol (PEG diacrylate) and a photoinitiator that can be polymerized into solid beads. This protocol and accompanying discussion provide a foundation of design principles and fabrication methods that enables development of a wide variety of microfluidic devices. The details included here should allow non-specialists to design and fabricate novel devices, thereby bringing a host of recently developed technologies to their most exciting applications in biological laboratories.

Multilayer microfluidic devices often involve the fabrication of master molds with complex geometries for functionality. This article presents a complete protocol for multi-step photolithography with valves and variable height features tunable to any application. As a demonstration, we fabricate a microfluidic droplet generator capable of producing hydrogel beads.

Multi-étape Hauteur variable photolithographie pour dispositifs microfluidiques à valve Multilayer

Microfluidic systems have enabled powerful new approaches to high-throughput biochemical and biological analysis. However, there remains a barrier to ...

Fabrication of a Multiplexed Artificial Cellular MicroEnvironment Array

Cellular microenvironments consist of a variety of cues, such as growth factors, extracellular matrices, and intercellular interactions. These cues are well orchestrated and are crucial in regulating cell functions in a living system. Although a number of researchers have attempted to investigate the correlation between environmental factors and desired cellular functions, much remains unknown. This is largely due to the lack of a proper methodology to mimic such environmental cues in vitro, and simultaneously test different environmental cues on cells. Here, we report an integrated platform of microfluidic channels and a nanofiber array, followed by high-content single-cell analysis, to examine stem cell phenotypes altered by distinct environmental factors. To demonstrate the application of this platform, this study focuses on the phenotypes of self-renewing human pluripotent stem cells (hPSCs). Here, we present the preparation procedures for a nanofiber array and the microfluidic structure in the fabrication of a Multiplexed Artificial Cellular MicroEnvironment (MACME) array. Moreover, overall steps of the single-cell profiling, cell staining with multiple fluorescent markers, multiple fluorescence imaging, and statistical analyses, are described.

This article describes the detailed methodology to prepare a Multiplexed Artificial Cellular MicroEnvironment (MACME) array for high-throughput manipulation of physical and chemical cues mimicking in vivo cellular microenvironments and to identify the optimal cellular environment for human pluripotent stem cells (hPSCs) with single-cell profiling.

Fabrication d’un réseau multiplexé microenvironnement cellulaire artificiel

Cellular microenvironments consist of a variety of cues, such as growth factors, extracellular matrices, and intercellular interactions. These cues are ...

Detection of Endotoxin in Nano-formulations Using Limulus Amoebocyte Lysate (LAL) Assays

When present in pharmaceutical products, a Gram-negative bacterial cell wall component endotoxin (often also called lipopolysaccharide) can cause inflammation, fever, hypo- or hypertension, and, in extreme cases, can lead to tissue and organ damage that may become fatal. The amounts of endotoxin in pharmaceutical products, therefore, are strictly regulated. Among the methods available for endotoxin detection and quantification, the Limulus Amoebocyte Lysate (LAL) assay is commonly used worldwide. While any pharmaceutical product can interfere with the LAL assay, nano-formulations represent a particular challenge due to their complexity. The purpose of this paper is to provide a practical guide to researchers inexperienced in estimating endotoxins in engineered nanomaterials and nanoparticle-formulated drugs. Herein, practical recommendations for performing three LAL formats including turbidity, chromogenic and gel-clot assays are discussed. These assays can be used to determine endotoxin contamination in nanotechnology-based drug products, vaccines, and adjuvants.

Detection of Endotoxin in Nano-formulations Using Limulus Amoebocyte Lysate LAL Assays

Detection of endotoxins in engineered nanomaterials represents one of the grand challenges in the field of nanomedicine. Here, we present a case study that describes the framework composed of three different LAL formats to estimate potential endotoxin contamination in nanoparticles.