Los autores desean agradecer el apoyo de los consejos de investigación y las subvenciones siguientes: EPSRC, HFSP, Fundación Nacional de Investigación de Corea (número de concesión R11-2009-044-1002-0K20904000004-09A050000410).

<ol>
	<li>Whitesides, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+origins+and+the+future+of+microfluidics.">The origins and the future of microfluidics.</a> Nature. 442, 368-368 (2006).</li><li>Zheng, B., Angew, I. s. m. a. g. i. l. o. v., F, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Microfluidic+Approach+for+Screening+Submicroliter+Volumes+against+Multiple+Reagents+by+Using+Preformed+Arrays+of+Nanoliter+Plugs+in+a+Three-Phase+Liquid/Liquid/Gas+Flow.">A Microfluidic Approach for Screening Submicroliter Volumes against Multiple Reagents by Using Preformed Arrays of Nanoliter Plugs in a Three-Phase Liquid/Liquid/Gas Flow.</a> Chem. Int. Ed. 44, 2520-2520 (2005).</li><li>Huebner, A., Sharma, S., Srisa-Art, M., Hollfelder, F., Edel, J. B., Demello, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microdroplets:+A+sea+of+applications.">Microdroplets: A sea of applications.</a> Lab on a Chip. 8, 1244-1244 (2008).</li><li>deMello, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+and+detection+of+chemical+reactions+in+microfluidic+systems.">Control and detection of chemical reactions in microfluidic systems.</a> Nature. 442, 394-394 (2006).</li><li>Thorsen, T., Roberts, R. W., Arnold, F. H., Quake, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+pattern+formation+in+a+vesicle-generating+microfluidic+device.">Dynamic pattern formation in a vesicle-generating microfluidic device.</a> Phys. Rev. Lett. 86, 4163-4163 (2001).</li><li>Anna, S. L., Bontoux, N., Stone, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formation+of+dispersions+using+"flow+focusing"+in+microchannels.">Formation of dispersions using "flow focusing" in microchannels.</a> Appl. Phys. Lett. 82, 364-364 (2003).</li><li>Casadevall i Solvas, X., Srisa-Art, M., deMello, A. J., Edel, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mapping+of+Fluidic+Mixing+in+Microdroplets+with+1+&#x03BC;s+Time+Resolution+Using+Fluorescence+Lifetime+Imaging.">Mapping of Fluidic Mixing in Microdroplets with 1 &#x03BC;s Time Resolution Using Fluorescence Lifetime Imaging.</a> Anal. Chem. 82, 3950-3950 (2010).</li><li>Robinson, T. A., Schaerli, Y., Wootton, R., Hollfelder, F., Dunsby, C., Baldwin, G., Neil, M., French, P., deMello, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Removal+of+background+signals+from+fluorescence+thermometry+measurements+in+PDMS+microchannels+using+fluorescence+lifetime+imaging.">Removal of background signals from fluorescence thermometry measurements in PDMS microchannels using fluorescence lifetime imaging.</a> Lab. Chip. 9, 3437-3441 (2009).</li><li>Huebner, A., Srisa-Art, M., Holt, D., Abell, C., Hollfelder, F., deMello, A. J., Edel, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+detection+of+protein+expression+in+single+cells+using+droplet+microfluidics.">Quantitative detection of protein expression in single cells using droplet microfluidics.</a> Chem. Commun. 1218, (2007).</li><li>Edel, J. B., Eid, J. S., Meller, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accurate+single+molecule+FRET+efficiency+determination+for+surface+immobilized+DNA+using+maximum+likelihood+calculated+lifetimes.">Accurate single molecule FRET efficiency determination for surface immobilized DNA using maximum likelihood calculated lifetimes.</a> J. Phys. Chem. B. 73, 2986-2990 (2007).</li></ol>

Hemos descrito la fabricación de un dispositivo de microfluidos, un montaje experimental y los protocolos asociados para la formación de microgotas y la encapsulación del reactivo y de detección óptica de las gotas de procesado. Los dos ejemplos seleccionados (la detección de células individuales en gotas y el mapeo de los procesos de mezcla dentro de las gotas de fluido) representan las aplicaciones más comunes que se están investigando con la microfluídica gota. Como los experimentos presentados ilustran el uso de plataformas de microfluidos gota presentan ciertas características atractivas, tales como un alto rendimiento, el confinamiento cuasi-perfecta, alta reproducibilidad ... La gran cantidad de información producida y la alta velocidad a la que se proyecta esta información que se genera, sin embargo, requieren el uso de métodos de detección rápida con una resolución espacio-temporal de alta si la ventaja es que se derivan de estas plataformas en miniatura. En este caso se demuestra que esto esposible con alta precisión las técnicas espectroscópicas fluorescentes. En particular, la técnica de detección FLIM (que hace uso de un láser pulsado con períodos de repetición a intervalos de un ns pocos) pone de manifiesto la capacidad de obtener información muy rápidamente a partir de las gotas que fluyen rápidamente (de alrededor de 200 por segundo). En este caso, la resolución temporal de los eventos detectados fue de tan sólo 1 ms. En cuanto a los límites en el tamaño de la gota y la concentración, el uso de lentes de mayor apertura numérica y mayor potencia láser fácilmente permitir la detección de concentraciones nM en gotas tan pequeñas como 5 micras (las limitaciones en el tamaño de la gota impuestas por las resoluciones de la fotolitografía proceso de fabricación y de la etapa de posicionamiento de sub-micras). Gotas de microfluidos son candidatos ideales para llevar a cabo experimentos a gran escala de pequeños importes de los reactivos, hasta un solo objetivo / evento. Las limitaciones actuales de esta tecnología incluyen la dificultad para generar droplets de una gran variedad (decenas o cientos) de distinta procedencia en una forma de alto rendimiento. Además, la dificultad para seleccionar y manipular cada sola gota generada impone severas limitaciones a la aplicación práctica de estas técnicas. Por lo tanto, estos temas están en el centro de importantes esfuerzos de investigación destinados a desarrollar las soluciones tecnológicas necesarias que permitan a las plataformas de microfluidos gota para convertirse en un método estándar de referencia de investigación y análisis de aplicaciones de alto rendimiento.

<table border="1"><tbody><tr><td> Nombre del reactivo </td><td> Tipo </td><td> Empresa </td><td> Número de catálogo </td></tr><tr><td> Fluoresceína 5-isotiocianato (FITC) </td><td> Reactivo </td><td> Sigma-Aldrich </td><td> F3651 </td></tr><tr><td> Estreptavidina-Alexa Fluor 488 </td><td> Reactivo </td><td> Las sondas moleculares </td><td> S11223 </td></tr><tr><td> Perfluorodecalina </td><td> Reactivo </td><td> Sigma-Aldrich </td><td> P9900 </td></tr><tr><td> 1H, 1H, 2H, 2H-perfluorooctanol </td><td> Reactivo </td><td> Sigma-Aldrich </td><td> 370533 </td></tr><tr><td> Sylgard 184 kit de silicona de elastómero </td><td> Reactivo </td><td> Premier Farnell Reino Unido LTD </td><td> 1673921 </td></tr><tr><td> auramina-O </td><td> Reactivo </td><td> Sigma-Aldrich </td><td> 861030 </td></tr><tr><td> 485 nm láser pulsado de diodo </td><td> Equipo </td><td> PicoQuant </td><td> LDH-PC-485 </td></tr><tr><td> TCSPC tarjeta </td><td> Equipo </td><td> PicoQuant </td><td> TimeHarp 100 </td></tr><tr><td> espejo dicroico </td><td> Equipo </td><td> Chroma Technology Corp. </td><td> z488rdc, </td></tr><tr><td> Microscopio objetivo </td><td> Equipo </td><td> Olimpo </td><td> UPLSAPO 60XW </td></tr><tr><td> Fotodiodo de avalancha </td><td> Equipo </td><td> AQR-141, EG &amp; G, Perkin-Elmer). </td><td> AQR-141 </td></tr><tr><td> DMEM </td><td> Reactivo </td><td> Invitrogen </td><td> ABCD1234 </td></tr><tr><td> SYTO9 </td><td> Reactivo </td><td> Invitrogen </td><td> S34854 </td></tr><tr><td> Yoduro de propidio </td><td> Reactivo </td><td> Invitrogen </td><td> P3566 </td></tr><tr><td> Escherichia coli cepa top 10 </td><td> Las células </td><td> Invitrogen </td><td> C4040-10 </td></tr></tbody></table>

fluorescence detection methods for microfluidic droplet platforms

El desarrollo de plataformas de microfluidos para la realización de la química y la biología ha sido en gran parte impulsado por una serie de beneficios potenciales que acompañan a la miniaturización del sistema. Las ventajas incluyen la capacidad de procesar de manera eficiente a la nano-femoto litros el volumen de la muestra, la integración fácil de los componentes funcionales, una predisposición intrínseca a gran escala de multiplexación, el rendimiento analítico mejorado, un mejor control y reducción de huellas instrumentales 1. En los últimos años un gran interés se ha centrado en el desarrollo de la gota basado (o flujo segmentado) los sistemas de microfluidos y su potencial como plataformas de alto rendimiento de la experimentación. 2-4 Aquí el agua en aceite se hacen para formar de forma espontánea en los canales de microfluidos como resultado de la inestabilidad capilar entre las dos fases inmiscibles. Es importante destacar que las microgotas de volúmenes definidos con precisión y las composiciones se pueden generar en las frecuenciasde varios kHz. Además, mediante la encapsulación de los reactivos de interés dentro de compartimentos estancos separados por una fase continua inmiscible, tanto de la muestra transversal de conversación y de dispersión (difusión y Taylor base) puede ser eliminado, lo que conduce a un mínimo la contaminación cruzada y la capacidad de tiempo de los procesos analíticos con gran precisión. Además, dado que no hay contacto entre el contenido de las gotas y las paredes del canal (que se han humedecido por la fase continua) la absorción y la pérdida de reactivos en las paredes del canal se previene. Una vez que las gotas de este tipo se han generado y procesado, es necesario extraer la información analítica necesaria. En este sentido, el método de detección de elección debe ser rápida, proporciona alta sensibilidad y bajos límites de detección, se aplica a una variedad de especies moleculares, que no destructivo y ser capaz de integrarse con dispositivos de microfluidos de una manera fácil. Para satisfacer esta necesidad hemos desarrollado comouite de herramientas experimentales y protocolos que permiten la extracción de grandes cantidades de información fotofísicos de entornos de pequeño volumen, y son aplicables al análisis de una amplia gama de parámetros físicos, químicos y biológicos. Aquí dos ejemplos de estos métodos se presentan y se aplica a la detección de células individuales y el mapeo de los procesos de mezcla dentro de las gotas de volumen picolitros. Se describe el proceso experimental completo, incluyendo la fabricación de chips de microfluidos, la configuración óptica y el proceso de generación y detección de gota.

Watch this Scientific Journal Video about Fluorescence detection methods for microfluidic droplet platforms at JoVE.com

Fluorescence detection methods for microfluidic droplet platforms

Gota de plataformas basadas en microfluidos son candidatos prometedores para la experimentación de alto rendimiento, ya que son capaces de generar picolitros, la auto-compartimentado barcos bajo costo en las tasas de kHz. Mediante la integración con rápido, sensible y de alta resolución espectroscópica métodos de fluorescencia, la gran cantidad de información generada dentro de estos sistemas se puede extraer de manera eficiente, aprovechar y utilizar.

Métodos de detección de fluorescencia para las plataformas de las gotas de microfluidos

The development of microfluidic platforms for performing chemistry and biology has in large part been driven by a range of potential benefits that ...

fluorescence-detection-methods-for-microfluidic-droplet-platforms

Research

JoVE Journal

Bioengineering

21.9K vistas.  Imperial College London. Gota de plataformas basadas en microfluidos son candidatos prometedores para la experimentación de alto rendimiento, ya que son capaces de generar picolitros, la auto-compartimentado barcos bajo costo en las tasas de kHz. Mediante la integración con rápido, sensible y de alta resolución espectroscópica métodos de fluorescencia, la gran cantidad de información generada dentro de estos sistemas se puede extraer de manera eficiente, aprovechar y utilizar.

Video: Fluorescence detection methods for microfluidic droplet platforms

Microfabricated Platforms for Mechanically Dynamic Cell Culture

The ability to systematically probe in vitro cellular response to combinations of mechanobiological stimuli for tissue engineering, drug discovery or fundamental cell biology studies is limited by current bioreactor technologies, which cannot simultaneously apply a variety of mechanical stimuli to cultured cells. In order to address this issue, we have developed a series of microfabricated platforms designed to screen for the effects of mechanical stimuli in a high-throughput format. In this protocol, we demonstrate the fabrication of a microactuator array of vertically displaced posts on which the technology is based, and further demonstrate how this base technology can be modified to conduct high-throughput mechanically dynamic cell culture in both two-dimensional and three-dimensional culture paradigms.

In this protocol, we demonstrate the fabrication of a microactuator array of vertically displaced posts on which the technology is based, and how this base technology can be modified to conduct high-throughput mechanically dynamic cell culture in both two-dimensional and three-dimensional culture paradigms.

Plataformas microfabricated para el cultivo celular mecánico dinámico

The ability to systematically probe in vitro cellular response to combinations of mechanobiological stimuli for tissue engineering, drug discovery or ...

Investigación

Bioingeniería

High Throughput Microfluidic Rapid and Low Cost Prototyping Packaging Methods

In this work, 3 different packaging and assembly techniques are presented. They can be classified into two categories: one-time use and reusable packaging techniques.
The one-time use packaging technique employs UV-based and temperature curing epoxies to connect microtubes to access holes, wire-bonding for integrated circuit connections, and silver epoxy for electrical connections. This method is based on a robust assembly technique that can support relatively high pressure close to 1 psi and does not need any support to strengthen the microfluidic architecture.
Reusable packaging techniques consist of PDMS-based microtube interconnectors and anisotropic adhesive films for electrical connections. These devices are more sensitive and fragile. Consequently, Plexiglas support is added to the microfluidic structure to improve the electrical contact when anisotropic adhesive films are used, and also to strengthen the microfluidic architecture. In addition, a micromanipulator is needed to maintain tubes while using a thin PDMS layer to connect them to the access holes. Different PDMS layer thicknesses, ranging from 0.45-3 mm, are tested to compare the best adherence versus injection rates. Applied injection rates are varied from 50-300 &#956;l/hr for 0.45-3 mm PDMS layers, respectively. These techniques are mainly applicable for low-pressure applications. However, they can be extended for high-pressure ones through plasma-oxygen process to permanently seal the PDMS to glass substrates. The main advantage of this technique, besides the fact that it is reusable, consists of keeping the device observable when the microchannel length is very short (in the range of 3 mm or lower).

In this article we describe different techniques for microfluidic rapid prototyping platforms. The proposed techniques are based on ultraviolet (UV) sensitive and temperature curing epoxies, polydimethylsiloxane (PDMS) based tubing, wire-bonding, and anisotropic adhesive films. The assembling procedures presented are developed for both one-time use devices as well as reusable microfluidic systems.

In this work, 3 different packaging and assembly techniques are presented. They can be classified into two categories: one-time use and reusable packaging ...

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

The objective of this video protocol is to discuss how to perform and analyze a three-dimensional fluorescent orbital particle tracking experiment using a modified two-photon microscope1. As opposed to conventional approaches (raster scan or wide field based on a stack of frames), the 3D orbital tracking allows to localize and follow with a high spatial (10 nm accuracy) and temporal resolution (50 Hz frequency response) the 3D displacement of a moving fluorescent particle on length-scales of hundreds of microns2. The method is based on a feedback algorithm that controls the hardware of a two-photon laser scanning microscope in order to perform a circular orbit around the object to be tracked: the feedback mechanism will maintain the fluorescent object in the center by controlling the displacement of the scanning beam3-5. To demonstrate the advantages of this technique, we followed a fast moving organelle, the lysosome, within a living cell6,7. Cells were plated according to standard protocols, and stained using a commercially lysosome dye. We discuss briefly the hardware configuration and in more detail the control software, to perform a 3D orbital tracking experiment inside living cells. We discuss in detail the parameters required in order to control the scanning microscope and enable the motion of the beam in a closed orbit around the particle. We conclude by demonstrating how this method can be effectively used to track the fast motion of a labeled lysosome along microtubules in 3D within a live cell. Lysosomes can move with speeds in the range of 0.4-0.5 &#181;m/sec, typically displaying a directed motion along the microtubule network8.

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

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

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

From Fast Fluorescence Imaging to Molecular Diffusion Law on Live Cell Membranes in a Commercial Microscope

It has become increasingly evident that the spatial distribution and the motion of membrane components like lipids and proteins are key factors in the regulation of many cellular functions. However, due to the fast dynamics and the tiny structures involved, a very high spatio-temporal resolution is required to catch the real behavior of molecules. Here we present the experimental protocol for studying the dynamics of fluorescently-labeled plasma-membrane proteins and lipids in live cells with high spatiotemporal resolution. Notably, this approach doesn&#8217;t need to track each molecule, but it calculates population behavior using all molecules in a given region of the membrane. The starting point is a fast imaging of a given region on the membrane. Afterwards, a complete spatio-temporal autocorrelation function is calculated correlating acquired images at increasing time delays, for example each 2, 3, n repetitions. It is possible to demonstrate that the width of the peak of the spatial autocorrelation function increases at increasing time delay as a function of particle movement due to diffusion. Therefore, fitting of the series of autocorrelation functions enables to extract the actual protein mean square displacement from imaging (iMSD), here presented in the form of apparent diffusivity vs average displacement. This yields a quantitative view of the average dynamics of single molecules with nanometer accuracy. By using a GFP-tagged variant of the Transferrin Receptor (TfR) and an ATTO488 labeled 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphoethanolamine (PPE) it is possible to observe the spatiotemporal regulation of protein and lipid diffusion on &#181;m-sized membrane regions in the micro-to-milli-second time range.

Spatial distribution and temporal dynamics of plasma membrane proteins and lipids is a hot topic in biology. Here this issue is addressed by a spatio-temporal image fluctuation analysis that provides conceptually the same physical quantities of single particle tracking, but it uses small molecular labels and standard microscopy setups.

De Fluorescencia Fast Imaging a la Ley de Difusión Molecular en membranas de células vivas en un microscopio Comercial

It has become increasingly evident that the spatial distribution and the motion of membrane components like lipids and proteins are key factors in the ...

Fluorescence Recovery after Merging a Droplet to Measure the Two-dimensional Diffusion of a Phospholipid Monolayer

We introduce a new method to measure the lateral diffusivity of a surfactant monolayer at the fluid-fluid interface, called fluorescence recovery after merging (FRAM). FRAM adopts the same principles as the fluorescence recovery after photobleaching (FRAP) technique, especially for measuring fluorescence recovery after bleaching a specific area, but FRAM uses a drop coalescence instead of photobleaching dye molecules to induce a chemical potential gradient of dye molecules. Our technique has several advantages over FRAP: it only requires a fluorescence microscope rather than a confocal microscope equipped with high power lasers; it is essentially free from the selection of fluorescence dyes; and it has far more freedom to define the measured diffusion area. Furthermore, FRAM potentially provides a route for studying the mixing or inter-diffusion of two different surfactants, when the monolayers at a surface of droplet and at a flat air/water interface are prepared with different species, independently.

We present a new technique to measure the lateral diffusion of a surface active species at the fluid-fluid interface by merging a droplet monolayer onto a flat monolayer.

La recuperación de fluorescencia después de combinar una gotita de medir la difusión de dos dimensiones de un fosfolípido monocapa

We introduce a new method to measure the lateral diffusivity of a surfactant monolayer at the fluid-fluid interface, called fluorescence recovery after ...

Multicolor Fluorescence Detection for Droplet Microfluidics Using Optical Fibers

Fluorescence assays are the most common readouts used in droplet microfluidics due to their bright signals and fast time response. Applications such as multiplex assays, enzyme evolution, and molecular biology enhanced cell sorting require the detection of two or more colors of fluorescence. Standard multicolor detection systems that couple free space lasers to epifluorescence microscopes are bulky, expensive, and difficult to maintain. In this paper, we describe a scheme to perform multicolor detection by exciting discrete regions of a microfluidic channel with lasers coupled to optical fibers. Emitted light is collected by an optical fiber coupled to a single photodetector. Because the excitation occurs at different spatial locations, the identity of emitted light can be encoded as a temporal shift, eliminating the need for more complicated light filtering schemes. The system has been used to detect droplet populations containing four unique combinations of dyes and to detect sub-nanomolar concentrations of fluorescein.

Multicolor fluorescence detection in droplet microfluidics typically involves bulky and complex epifluorescence microscope-based detection systems. Here we describe a compact and modular multicolor detection scheme that utilizes an array of optical fibers to temporally encode multicolor data collected by a single photodetector.

Multicolor detección por fluorescencia de la gotita de microfluídica el uso de fibras ópticas

Fluorescence assays are the most common readouts used in droplet microfluidics due to their bright signals and fast time response. Applications such as ...

Fully Automated Centrifugal Microfluidic Device for Ultrasensitive Protein Detection from Whole Blood

Enzyme-linked immunosorbent assay (ELISA) is a promising method to detect small amount of proteins in biological samples. The devices providing a platform for reduced sample volume and assay time as well as full automation are required for potential use in point-of-care-diagnostics. Recently, we have demonstrated ultrasensitive detection of serum proteins, C-reactive protein (CRP) and cardiac troponin I (cTnI), utilizing a lab-on-a-disc composed of TiO2 nanofibrous (NF) mats. It showed a large dynamic range with femto molar (fM) detection sensitivity, from a small volume of whole blood in 30 min. The device consists of several components for blood separation, metering, mixing, and washing that are automated for improved sensitivity from low sample volumes. Here, in the video demonstration, we show the experimental protocols and know-how for the fabrication of NFs as well as the disc, their integration and the operation in the following order: processes for preparing TiO2 NF mat; transfer-printing of TiO2 NF mat onto the disc; surface modification for immune-reactions, disc assembly and operation; on-disc detection and representative results for immunoassay. Use of this device enables multiplexed analysis with minimal consumption of samples and reagents. Given the advantages, the device should find use in a wide variety of applications, and prove beneficial in facilitating the analysis of low abundant proteins.

This protocol demonstrates how to achieve femto molar detection sensitivity of proteins in 10 &#181;L of whole blood within 30 min. This can be achieved by using electrospun nanofibrous mats integrated in a lab-on-a-disc, which offers high surface area as well as effective mixing and washing for enhanced signal-to-noise ratio.

Totalmente automatizada de dispositivos de microfluidos para centrífuga Ultrasensible detección de proteínas a partir de sangre entera

Enzyme-linked immunosorbent assay (ELISA) is a promising method to detect small amount of proteins in biological samples. The devices providing a platform ...

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.

Múltiples pasos Fotolitografia variable Altura de múltiples capas con válvula dispositivos de microfluidos

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

Microfluidic Platform with Multiplexed Electronic Detection for Spatial Tracking of Particles

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

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

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

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

A Droplet-Based Microfluidic Approach and Microsphere-PCR Amplification for Single-Stranded DNA Amplicons

Droplet-based microfluidics enable the reliable production of homogeneous microspheres in the microfluidic channel, providing controlled size and morphology of the obtained microsphere. A microsphere copolymerized with an acrydite-DNA probe was successfully fabricated. Different methods such as asymmetric PCR, exonuclease digestion, and isolation on streptavidin-coated magnetic beads can be used to synthesize single-stranded DNA (ssDNA). However, these methods cannot efficiently use large amounts of highly purified ssDNA. Here, we describe a microsphere-PCR protocol detailing how ssDNA can be efficiently amplified and separated from dsDNA simply by pipetting from a PCR reaction tube. The amplification of ssDNA can be applied as potential reagents for the DNA microarray and DNA-SELEX (Systematic evolution of ligands by exponential enrichment) processes.

This work provides a method for the fabrication of droplet-based microfluidic platforms and the application of polyacrylamide microspheres for microsphere-PCR amplification. The microsphere-PCR method makes it possible to obtain single-stranded DNA amplicons without separating double-stranded DNA.