Este trabalho é apoiado pela National Science Foundation FIBR (NSF EF-0623664) e IDBR (NSF DBI-0754570). Este trabalho foi parcialmente financiado por fundos da National Science Foundation Grant FIBR 0623664 administrado pelo Centro de Biophotonics, uma Ciência NSF e Centro de Tecnologia, gerido pela Universidade da Califórnia, em Davis, nos termos do Acordo de Cooperação PHY 0120999. A pesquisa de Lisa Lapidus, Ph.D. é apoiado em parte por um Prémio Carreira na Interface Científica do Fundo de Bem-vindo Burroughs.

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	<li>Eaton, W. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+kinetics+and+mechanisms+in+protein+folding.">Fast kinetics and mechanisms in protein folding.</a> Annual Review of Biophysics and Biomolecular Structure. 29, 327-359 (2000).</li><li>Hertzog, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Femtomole+mixer+for+microsecond+kinetic+studies+of+protein+folding.">Femtomole mixer for microsecond kinetic studies of protein folding.</a> Analytical Chemistry. 76, 7169-7178 (2004).</li><li>Hertzog, D. E., Ivorra, B., Mohammadi, B., Bakajin, O., Santiago, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimization+of+a+microfluidic+mixer+for+studying+protein+folding+kinetics.">Optimization of a microfluidic mixer for studying protein folding kinetics.</a> Analytical Chemistry. 78, 4299-4306 (2006).</li><li>Yao, S., Bakajin, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improvements+in+Mixing+Time+and+Mixing+Uniformity+in+Devices+Designed+for+Studies+of+Protein+Folding+Kinetics.">Improvements in Mixing Time and Mixing Uniformity in Devices Designed for Studies of Protein Folding Kinetics.</a> Analytical Chemistry. 79, 5753-5759 (2007).</li><li>Lapidus, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+Hydrophobic+Collapse+and+Early+Folding+Steps+Observed+in+a+Microfluidic+Mixer.">Protein Hydrophobic Collapse and Early Folding Steps Observed in a Microfluidic Mixer.</a> Biophysical Journal. 93, 218-224 (2007).</li><li>Bilsel, O., Kayatekin, C., Wallace, L. A., Matthews, C. 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+microchannel+solution+mixer+for+studying+microsecond+protein+folding+reactions.">A microchannel solution mixer for studying microsecond protein folding reactions.</a> Review of Scientific Instruments. 76, (2005).</li><li>Chan, C. -. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Submillisecond+protein+folding+kinetics+studied+by+ultrarapid+mixing.">Submillisecond protein folding kinetics studied by ultrarapid mixing.</a> PNAS. 94, 1779-1784 (1997).</li><li>Shastry, M. C. R., Luck, S. D., Roder, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+continuous-flow+capillary+mixing+method+to+monitor+reactions+on+the+microsecond+time+scale.">A continuous-flow capillary mixing method to monitor reactions on the microsecond time scale.</a> Biophysical Journal. 74, 2714-2721 (1998).</li><li>Pollack, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compactness+of+the+denatured+state+of+a+fast-folding+protein+measured+by+submillisecond+small-angle+x-ray+scattering.">Compactness of the denatured state of a fast-folding protein measured by submillisecond small-angle x-ray scattering.</a> Proceedings of the National Academy of Sciences of the United States of America. 96, 10115-10117 (1999).</li><li>Takahashi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Folding+of+cytochrome+c+initiated+by+submillisecond+mixing.">Folding of cytochrome c initiated by submillisecond mixing.</a> Nature Structural Molecular Biology. 4, 44-50 (1997).</li><li>Knight, J. B., Vishwanath, A., Brody, J. P., Austin, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrodynamic+focusing+on+a+silicon+chip:+Mixing+nanoliters+in+microseconds.">Hydrodynamic focusing on a silicon chip: Mixing nanoliters in microseconds.</a> Physical Review Letters. 80, 3863-3866 (1998).</li><li>DeCamp, S. J., Naganathan, A. N., Waldauer, S. A., Bakajin, O., Lapidus, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+Observation+of+Downhill+Folding+of+lambda-Repressor+in+a+Microfluidic+Mixer.">Direct Observation of Downhill Folding of lambda-Repressor in a Microfluidic Mixer.</a> Biophysical Journal. 97, 1772-1777 (2009).</li><li>Waldauer, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ruggedness+in+the+folding+landscape+of+protein+L.">Ruggedness in the folding landscape of protein L.</a> Hfsp Journal. 2, 388-395 (2008).</li><li>Shastry, M. C. R., Roder, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+for+barrier-limited+protein+folding+kinetics+on+the+microsecond+time+scale.">Evidence for barrier-limited protein folding kinetics on the microsecond time scale.</a> Nature Structural Biology. 5, 385-392 (1998).</li><li>Uzawa, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Collapse+and+search+dynamics+of+apomyoglobin+folding+revealed+by+submillisecond+observations+of+alpha-helical+content+and+compactness.">Collapse and search dynamics of apomyoglobin folding revealed by submillisecond observations of alpha-helical content and compactness.</a> Proceedings of the National Academy of Sciences of the United States of America. 101, 1171-1176 (2004).</li><li>Zhu, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+of+Multiple+Folding+Pathways+for+the+Villin+Headpiece+Subdomain.">Evidence of Multiple Folding Pathways for the Villin Headpiece Subdomain.</a> The Journal of Physical Chemistry B. 115, 12632-12637 (2011).</li></ol>

Não temos nada a divulgar.

A mistura rápida tem sido uma meta de desenvolvimento para o campo de enovelamento de proteínas por muitos anos porque ele tem sido reconhecido que os processos moleculares de biomoléculas ocorrem em escalas de tempo que variam de picosegundos de segundos. Convencionais stopped-flow misturadores têm tempos mortos de 1-5 ms, que é limitada principalmente pela turbulência. Turbulentos misturadores de fluxo contínuo com tempos de mistura de 30-300 mS têm sido desenvolvidos nos últimos 15 anos por um pequeno número de grupos, mas geralmente exigem altas taxas de fluxo para atingir estes tempos de mistura e, portanto, usar um monte de amostra 6-8. Este protocolo descreve o uso de microfluídicos fichas de mistura para alcançar uma rápida diluição no regime de fluxo laminar. Existem múltiplas vantagens para trabalhar dentro deste regime, mas um um primário é a capacidade para simular todo o processo de mistura com elevada precisão, que permite uma para modificar a resposta de mistura. T-misturadores desenvolvidos por outros grupos com geom simplesetries demonstraram tempos de mistura de 100-200 mS que foram principalmente limitada pelo tamanho da canais 9-10. Por dimensionar o tamanho dos canais a 10 uM Cavaleiro reduziu o tempo de mistura a ~ 10 microsiemens 11. Yao e Bakajin mostraram que pequenas mudanças na geometria poderia levar a melhorias significativas no tempo de mistura 4. No entanto, que o trabalho mostrou que a aceleração da mistura pode também conduzir a fases mais lentas também. O desenho utilizado neste trabalho 12-13 é um compromisso entre os dois melhores modelos em referência 4 para minimizar o mais lento de decaimento exponencial na concentração de desnaturante e também para fazer a característica mais reprodutível em condicionamento DRIE. Tem havido alguma controvérsia no campo de ultra-rápida misturados durante a definição do tempo de mistura. É importante reconhecer a diferença entre &quot;tempo de mistura&quot; e &quot;tempo morto&quot;. O tempo morto é definido num misturador turbulento como o tempo durante o qual uma MEDIÇÃOt não pode ser feita, e pode de facto ser significativamente mais longo do que o tempo real de mistura. É tipicamente determinada por fazer várias medições de uma reacção bimolecular pseudo-primeira ordem (tais como supressão da fluorescência de triptofano por N bromosuccinate) a várias concentrações. Os decai observados exponenciais estão equipados para convergir em um único valor assumido como sendo t = 0 S e que o tempo entre o ponto eo primeiro ponto medido é o tempo morto. Para misturadores de fluxo laminar, as medições podem ser feitas durante o processo de mistura para que não haja tempo morto, apenas um tempo de mistura. O tempo de mistura é simplesmente o tempo de combinar duas soluções até uniformidade suficiente é atingido. Nós previamente definido o tempo de mistura para ser um tempo 90/10, o tempo para a concentração de desnaturante para diminuir de 90% a 10% do valor não misturado. No entanto, a forma da curva de mistura não é perfeitamente simétrica com a cauda do decaimento tendo um pequeno componente exponencial. Além disso, dobrar a proteína tem umaltamente dependência não-linear da concentração de desnaturante de modo que a dobragem pode, muitas vezes mesmo se iniciar o desnaturante só é reduzido por duas vezes. Portanto, temos, mais recentemente, o tempo de mistura definido como o tempo para reduzir a concentração de desnaturante de 80%. Certamente outras definições podem ser usados, dependendo dos requisitos da experiência. A utilização deste misturador para estudar enrolamento de proteínas tem consistentemente revelou resultados surpreendentes. Folding de citocromo c e apomyoglobin têm sido estudadas para ter várias etapas de dobramento e os resultados iniciais com misturadores de fluxo contínuo mostrou queda para ocorrer no ~ 100 mS prazo 10,14-15. Os nossos medições com este misturador mostrou que haja pelo menos 2 passos nesta escala de tempo, uma muito rápida, provavelmente não específica colapso, (como medido por Trp mudança de fluorescência espectral) dentro do tempo de mistura do misturador seguido por uma fase mais lenta (como medido pela têmpera do total de emissão Trp), que é provável que o first formação da estrutura nativa 5. Observamos, também, um processo de 50 mS no domínio da proteína L B1, derrubando a interpretação convencional que essa proteína é uma pasta 2-estado 13. Uma vantagem deste misturador rápido é que ele pode sondar a dobragem dos mais rápidos proteínas de dobragem que geralmente têm sido apenas mensurável por nanossegundos T salto-instrumentos. T-salto tipicamente requer a observação de dobragem / desdobramento relaxamento perto da temperatura de fusão da proteína e, portanto, nunca se segue a dobra de toda a população. Com esta mesa vimos a dobra de γ-repressor (λ 6-86) com ambos emissão total Trp e mudança espectral e encontraram evidências de que a proteína tem nenhuma barreira para dobrar sob fortes condições dobráveis ​​que não eram acessíveis a T anteriores -pular medições 12. Finalmente, medimos o dobramento da headpiece vilina HP-35, um dos tele mais rápidos pastas ainda medidos e verificou que a taxa de dobragem medido após a mistura é de ~ 5 vezes mais lento do que medido por T-jump sob as mesmas condições de 16. Isto sugere que a cinética de dobragem depende das condições de partida, a capotagem um pressuposto importante no campo.

<table border="1"><tbody><tr><td> Nome do reagente </td><td> Companhia </td><td> Número de catálogo </td><td> Comentários </td></tr><tr><td> AZ P4110 Photoresist </td><td> Materiais AZ eletrônicos </td><td></td><td></td></tr><tr><td> AZ 400 Desenvolvedor K </td><td> Materiais AZ eletrônicos </td><td></td><td></td></tr><tr><td> Baker PRS 2000 Stripper fotorresiste </td><td> Performance Materials Avantor </td><td></td><td></td></tr><tr><td> AquaBond </td><td> AquaBond Technologies </td><td> AquaBond 55 </td><td></td></tr><tr><td> 500 wafer de cobertura mM </td><td> SENSOR Prep Serviços </td><td></td><td> Ø: 100 mm ± 0,5 mm Espessura: 0,5 mm ± 0,025 milímetros Tolerâncias padrão (exceto quando indicado) Revestimento de superfície: SI: 4-8a; SII: 8-12a Flats: Um primária de DST-SEMI; Um Scribe Limpa e polida, os dois lados </td></tr><tr><td> 170 wafer de cobertura mM </td><td> SENSOR Prep Serviços </td><td> 7980 Wafers 2G </td><td> Ø: 100 mm ± 0,5 mm Espessura: 0,17 mm ± 0,025 milímetros Tolerâncias padrão (exceto quando indicado) Revestimento de superfície: SI: 4-8a; SII: 8-12a Flats: Um primária de DST-SEMI; Um Scribe Limpa e polida, os dois lados </td></tr><tr><td> Etcher iônica reativa profunda para os óxidos </td><td> ULVAC </td><td> ULVAC NL-6000 </td><td></td></tr><tr><td> Argon Laser Ion </td><td> Cambridge Laser Laboratories </td><td> Lexel 95-SHG </td><td> lambda = 258 nm </td></tr><tr><td> Argon Laser Ion </td><td> Melles Griot </td><td></td><td> lambda = 488 nm </td></tr><tr><td> Microscópio </td><td> Olimpo </td><td> IX-51</td><td></td></tr><tr><td> Objetiva do microscópio </td><td> Thor Labs </td><td> RLO LMU-UVB 40X-0.5 NA </td><td> lambda = 258 nm </td></tr><tr><td> Objetiva do microscópio </td><td> Olimpo </td><td> UPLSAPO 60XW 1,2 NA </td><td> lambda = 488 nm </td></tr><tr><td> Nanopositioner </td><td> Mad City Labs </td><td> Nano-LP100 </td><td></td></tr><tr><td> Estágio Tradução Motorizada </td><td> Semprex Corp </td><td> KL-12-6436 Series </td><td></td></tr><tr><td> GaAsP Photon Contador </td><td> Hamamatsu </td><td> H7421-40 </td><td></td></tr><tr><td> Monochrometer </td><td> Horiba Instruments Inc </td><td> MicroHR </td><td></td></tr><tr><td> CCD da câmera </td><td> Andor Tecnologia </td><td> idus 420A-BU </td><td></td></tr><tr><td> Cloridrato de guanidina (GuHCl) </td><td> Sigma-Aldrich </td><td&gt; G4505 </td><td></td></tr></tbody></table>

microfluidic mixers for studying protein folding

O processo pelo qual um dobras de proteínas em sua conformação nativa é altamente relevante para a biologia e saúde humana mas ainda pouco compreendido. Uma razão para isso é que a dobragem tem lugar durante um vasta gama de escalas de tempo, a partir de nanosegundos em segundos ou mais, dependendo da proteína 1. Convencionais stopped-flow misturadores têm permitido a medição da cinética de dobragem a partir de cerca de 1 ms. Recentemente, desenvolvemos um misturador de microfluídica que dilui desnaturante ~ 100 vezes em ~ 8 mS 2. Ao contrário de um misturador de stopped-flow, este misturador opera no regime de fluxo laminar em que a turbulência não ocorre. A ausência de turbulência permite simulação numérica precisa de todos os fluxos dentro do misturador com excelente concordância para experimentar 3-4. O fluxo laminar é conseguida por números de Reynolds Re ≤ 100. Para soluções aquosas, isto requer geometrias escala mícron. Nós usamos um substrato duro, tal como silício ou sili fundidaca, para fazer canais iM 5-10 de largura e 10 uM de profundidade (ver Figura 1). As menores dimensões, na entrada para a região de mistura, são da ordem de 1 mícron de tamanho. O chip é selado com um fino ou de vidro de sílica fundida lamela para o acesso óptico. Típicos totais taxas de fluxo linear são ~ 1 m / s, Re rendendo ~ 10, mas o consumo de proteínas é apenas ~ 0,5 nL / s ou 1,8 uL / hr. A concentração de proteína depende do método de detecção: Para triptofano fluorescência a concentração típica é de 100 uM (para 1 Trp / proteína) e para FRET a concentração típica é de ~ 100 nM. O processo de dobragem é iniciada por diluição rápida de desnaturante a partir de 6 M a 0,06 M de hidrocloreto de guanidina. A proteína em desnaturante alta flui para baixo de um canal central e está reuniu-se em ambos os lados na região de mistura por tampão sem desnaturante movendo ~ 100 vezes mais rápido (ver Figura 2). Esta geometria faz com que a constrição do fluxo rápido de proteína em uma estreitajet ~ 100 nm de largura. A difusão das moléculas de luz desnaturantes é muito rápida, enquanto que a difusão das moléculas de proteína pesados ​​é muito mais lenta, difundindo menos do que 1 mícron de 1 ms. A diferença de difusão constante do desnaturante e os resultados de proteína em diluição rápida do desnaturante a partir do fluxo de proteínas, reduzindo a concentração eficaz do desnaturante em torno da proteína. O jacto de proteína flui a uma taxa constante para baixo o canal de observação e de fluorescência da proteína durante a dobragem pode ser observada usando um microscópio confocal de varredura 5.

Watch this Scientific Journal Video about Microfluidic Mixers for Studying Protein Folding at JoVE.com

Microfluidic Mixers for Studying Protein Folding

Neste trabalho, explicar a fabricação ea utilização de um misturador microfluídico capaz de mistura de duas soluções em ~ 8 mS. Nós também demonstrar a utilização destes misturadores com detecção de fluorescência utilizando espectroscopia de UV e de transferência de energia de ressonância de fluorescência (FRET).

Misturadores microfluídicos para Estudar o dobramento de proteínas

The process by which a protein folds into its native conformation is highly relevant to biology and human health yet still poorly understood. One reason ...

microfluidic-mixers-for-studying-protein-folding

Research

JoVE Journal

Bioengineering

15.0K visualizações.  Michigan State University. Neste trabalho, explicar a fabricação ea utilização de um misturador microfluídico capaz de mistura de duas soluções em ~ 8 mS. Nós também demonstrar a utilização destes misturadores com detecção de fluorescência utilizando espectroscopia de UV e de transferência de energia de ressonância de fluorescência (FRET).

Vídeo: Microfluidic Mixers for Studying Protein Folding

A Microfluidic-based Hydrodynamic Trap for Single Particles

The ability to confine and manipulate single particles in free solution is a key enabling technology for fundamental and applied science. Methods for particle trapping based on optical, magnetic, electrokinetic, and acoustic techniques have led to major advancements in physics and biology ranging from the molecular to cellular level. In this article, we introduce a new microfluidic-based technique for particle trapping and manipulation based solely on hydrodynamic fluid flow. Using this method, we demonstrate trapping of micro- and nano-scale particles in aqueous solutions for long time scales. The hydrodynamic trap consists of an integrated microfluidic device with a cross-slot channel geometry where two opposing laminar streams converge, thereby generating a planar extensional flow with a fluid stagnation point (zero-velocity point). In this device, particles are confined at the trap center by active control of the flow field to maintain particle position at the fluid stagnation point. In this manner, particles are effectively trapped in free solution using a feedback control algorithm implemented with a custom-built LabVIEW code. The control algorithm consists of image acquisition for a particle in the microfluidic device, followed by particle tracking, determination of particle centroid position, and active adjustment of fluid flow by regulating the pressure applied to an on-chip pneumatic valve using a pressure regulator. In this way, the on-chip dynamic metering valve functions to regulate the relative flow rates in the outlet channels, thereby enabling fine-scale control of stagnation point position and particle trapping. The microfluidic-based hydrodynamic trap exhibits several advantages as a method for particle trapping. Hydrodynamic trapping is possible for any arbitrary particle without specific requirements on the physical or chemical properties of the trapped object. In addition, hydrodynamic trapping enables confinement of a "single" target object in concentrated or crowded particle suspensions, which is difficult using alternative force field-based trapping methods. The hydrodynamic trap is user-friendly, straightforward to implement and may be added to existing microfluidic devices to facilitate trapping and long-time analysis of particles. Overall, the hydrodynamic trap is a new platform for confinement, micromanipulation, and observation of particles without surface immobilization and eliminates the need for potentially perturbative optical, magnetic, and electric fields in the free-solution trapping of small particles.

In this article, we present a microfluidic-based method for particle confinement based on hydrodynamic flow. We demonstrate stable particle trapping at a fluid stagnation point using a feedback control mechanism, thereby enabling confinement and micromanipulation of arbitrary particles in an integrated microdevice.

A Armadilha hidrodinâmica microfluídicos baseados em partículas individuais

The ability to confine and manipulate single particles in free solution is a key enabling technology for fundamental and applied science.  Methods for ...

Bioengenharia

Thermodynamics of Membrane Protein Folding Measured by Fluorescence Spectroscopy

Membrane protein folding is an emerging topic with both fundamental and health-related significance. The abundance of membrane proteins in cells underlies the need for comprehensive study of the folding of this ubiquitous family of proteins. Additionally, advances in our ability to characterize diseases associated with misfolded proteins have motivated significant experimental and theoretical efforts in the field of protein folding. Rapid progress in this important field is unfortunately hindered by the inherent challenges associated with membrane proteins and the complexity of the folding mechanism. Here, we outline an experimental procedure for measuring the thermodynamic property of the Gibbs free energy of unfolding in the absence of denaturant, &Delta;G&deg;H2O, for a representative integral membrane protein from E. coli. This protocol focuses on the application of fluorescence spectroscopy to determine equilibrium populations of folded and unfolded states as a function of denaturant concentration. Experimental considerations for the preparation of synthetic lipid vesicles as well as key steps in the data analysis procedure are highlighted. This technique is versatile and may be pursued with different types of denaturant, including temperature and pH, as well as in various folding environments of lipids and micelles. The current protocol is one that can be generalized to any membrane or soluble protein that meets the set of criteria discussed below.

This video article details the experimental procedure for obtaining the Gibbs free energy of membrane protein folding by tryptophan fluorescence.

Termodinâmica de enovelamento de proteínas de membrana Medido por espectroscopia de fluorescência

Membrane protein folding is an emerging topic with both fundamental and health-related significance.  The abundance of membrane proteins in cells ...

Fluorescence detection methods for microfluidic droplet platforms

The development of microfluidic platforms for performing chemistry and biology has in large part been driven by a range of potential benefits that accompany system miniaturisation. Advantages include the ability to efficiently process nano- to femoto- liter volumes of sample, facile integration of functional components, an intrinsic predisposition towards large-scale multiplexing, enhanced analytical throughput, improved control and reduced instrumental footprints.1
In recent years much interest has focussed on the development of droplet-based (or segmented flow) microfluidic systems and their potential as platforms in high-throughput experimentation.2-4 Here water-in-oil emulsions are made to spontaneously form in microfluidic channels as a result of capillary instabilities between the two immiscible phases. Importantly, microdroplets of precisely defined volumes and compositions can be generated at frequencies of several kHz. Furthermore, by encapsulating reagents of interest within isolated compartments separated by a continuous immiscible phase, both sample cross-talk and dispersion (diffusion- and Taylor-based) can be eliminated, which leads to minimal cross-contamination and the ability to time analytical processes with great accuracy. Additionally, since there is no contact between the contents of the droplets and the channel walls (which are wetted by the continuous phase) absorption and loss of reagents on the channel walls is prevented.
Once droplets of this kind have been generated and processed, it is necessary to extract the required analytical information. In this respect the detection method of choice should be rapid, provide high-sensitivity and low limits of detection, be applicable to a range of molecular species, be non-destructive and be able to be integrated with microfluidic devices in a facile manner. To address this need we have developed a suite of experimental tools and protocols that enable the extraction of large amounts of photophysical information from small-volume environments, and are applicable to the analysis of a wide range of physical, chemical and biological parameters. Herein two examples of these methods are presented and applied to the detection of single cells and the mapping of mixing processes inside picoliter-volume droplets. We report the entire experimental process including microfluidic chip fabrication, the optical setup and the process of droplet generation and detection.

Droplet-based microfluidic platforms are promising candidates for high throughput experimentation since they are able to generate picoliter, self-compartmentalized vessels inexpensively at kHz rates. Through integration with fast, sensitive and high resolution fluorescence spectroscopic methods, the large amounts of information generated within these systems can be efficiently extracted, harnessed and utilized.

Métodos de detecção de fluorescência para as plataformas de gotículas microfluídicos

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

High-throughput Protein Expression Generator Using a Microfluidic Platform

Rapidly increasing fields, such as systems biology, require the development and implementation of new technologies, enabling high-throughput and high-fidelity measurements of large systems. Microfluidics promises to fulfill many of these requirements, such as performing high-throughput screening experiments on-chip, encompassing biochemical, biophysical, and cell-based assays1. Since the early days of microfluidics devices, this field has drastically evolved, leading to the development of microfluidic large-scale integration2,3. This technology allows for the integration of thousands of micromechanical valves on a single device with a postage-sized footprint (Figure 1). We have developed a high-throughput microfluidic platform for generating in vitro expression of protein arrays (Figure 2) named PING (Protein Interaction Network Generator). These arrays can serve as a template for many experiments such as protein-protein 4, protein-RNA5 or protein-DNA6 interactions.
The device consist of thousands of reaction chambers, which are individually programmed using a microarrayer. Aligning of these printed microarrays to microfluidics devices programs each chamber with a single spot eliminating potential contamination or cross-reactivity Moreover, generating microarrays using standard microarray spotting techniques is also very modular, allowing for the arraying of proteins7, DNA8, small molecules, and even colloidal suspensions. The potential impact of microfluidics on biological sciences is significant. A number of microfluidics based assays have already provided novel insights into the structure and function of biological systems, and the field of microfluidics will continue to impact biology.

We present a microfluidic approach for the expression of protein arrays. The device consists of thousands of reaction chambers controlled by micro-mechanical valves. The microfluidic device is mated to a microarray-printed gene library. These genes are then transcribed and translated on-chip, resulting in a protein array ready for experimental use.

Alto rendimento Gerador Protein Expression Usando uma plataforma microfluídica

Rapidly increasing fields, such as systems biology, require the development and implementation of new technologies, enabling high-throughput and ...

A Microfluidic Device for Studying Multiple Distinct Strains

The study of cell responses to environmental changes poses many experimental challenges: cells need to be imaged under changing conditions, often in a comparative manner. Multiwell plates are routinely used to compare many different strains or cell lines, but allow limited control over the environment dynamics. Microfluidic devices, on the other hand, allow exquisite dynamic control over the surrounding conditions, but it is challenging to image and distinguish more than a few strains in them. Here we describe a method to easily and rapidly manufacture a microfluidic device capable of applying dynamically changing conditions to multiple distinct yeast strains in one channel. The device is designed and manufactured by simple means without the need for soft lithography. It is composed of a Y-shaped flow channel attached to a second layer harboring microwells. The strains are placed in separate microwells, and imaged under the exact same dynamic conditions. We demonstrate the use of the device for measuring protein localization responses to pulses of nutrient changes in different yeast strains.

We present a simple method to produce microfluidic devices capable of applying similar dynamic conditions to multiple distinct strains, without the need for a clean room or soft lithography.

Um dispositivo micro para o Estudo múltiplas linhagens distintas

The study of cell responses to environmental changes poses many experimental challenges: cells need to be imaged under changing conditions, often in a ...

A Microfluidic Chip for ICPMS Sample Introduction

This protocol discusses the fabrication and usage of a disposable low cost microfluidic chip as sample introduction system for inductively coupled plasma mass spectrometry (ICPMS). The chip produces monodisperse aqueous sample droplets in perfluorohexane (PFH). Size and frequency of the aqueous droplets can be varied in the range of 40 to 60 &#181;m and from 90 to 7,000&#160;Hz, respectively. The droplets are ejected from the chip with a second flow of PFH and remain intact during the ejection. A custom-built desolvation system removes the PFH and transports the droplets into the ICPMS. Here, very stable signals with a narrow intensity distribution can be measured, showing the monodispersity of the droplets. We show that the introduction system can be used to quantitatively determine iron in single bovine red blood cells. In the future, the capabilities of the introduction device can easily be extended by the integration of additional microfluidic modules.

We present a discrete droplet sample introduction system for inductively coupled plasma mass spectrometry (ICPMS). It is based on a cheap and disposable microfluidic chip that generates highly monodisperse droplets in a size range of 40&#8722;60 &#181;m at frequencies from 90 to 7,000 Hz.

Um chip microfluídico para ICPMS Amostra Introdução

This protocol discusses the fabrication and usage of a disposable low cost microfluidic chip as sample introduction system for inductively coupled plasma ...

Studying Protein Function and the Role of Altered Protein Expression by Antibody Interference and Three-dimensional Reconstructions

A strict management of protein expression is not only essential to every organism alive, but also an important strategy to investigate protein functions in cellular models. Therefore, recent research invented different tools to target protein expression in mammalian cell lines or even animal models, including RNA and antibody interference. While the first strategy has gathered much attention during the past two decades, peptides &#160;mediating a translocation of antibody cargos across cellular membranes and into cells, obtained much less interest. In this publication, we provide a detailed protocol how to utilize a peptide carrier named Chariot in human embryonic kidney cells as well as in primary hippocampal neurons to perform antibody interference experiments and further illustrate the application of three-dimensional reconstructions in analyzing protein function. Our findings suggest that Chariot is, probably due to its nuclear localization signal, particularly well-suited to target proteins residing in the soma and the nucleus. Remarkably, when applying Chariot to primary hippocampal cultures, the reagent turned out to be surprisingly well accepted by dissociated neurons.

Controlling protein expression is not only essential to every organism alive, but also an important strategy to investigate protein functions in cellular models. The protocol presented shows the application of antibody interference in mammalian cells including primary hippocampal neurons and demonstrates the use of three-dimensional reconstructions in studying protein function.

Estudar a função da proteína eo papel da expressão proteína alterada pela interferência de anticorpos e reconstruções tridimensionais

A strict management of protein expression is not only essential to every organism alive, but also an important strategy to investigate protein functions ...

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 dispositivo automático centrífugo microfluídicos para a detecção de proteínas Ultrasensitive de Sangue Total

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

Designing Microfluidic Devices for Studying Cellular Responses Under Single or Coexisting Chemical/Electrical/Shear Stress Stimuli

Microfluidic devices are capable of creating a precise and controllable cellular micro-environment of pH, temperature, salt concentration, and other physical or chemical stimuli. They have been commonly used for in vitro cell studies by providing in vivo like surroundings. Especially, how cells response to chemical gradients, electrical fields, and shear stresses has drawn many interests since these phenomena are important in understanding cellular properties and functions. These microfluidic chips can be made of glass substrates, silicon wafers, polydimethylsiloxane (PDMS) polymers, polymethylmethacrylate (PMMA) substrates, or polyethyleneterephthalate (PET) substrates. Out of these materials, PMMA substrates are cheap and can be easily processed using laser ablation and writing. Although a few microfluidic devices have been designed and fabricated for generating multiple, coexisting chemical and electrical stimuli, none of them was considered efficient enough in reducing experimental repeats, particular for screening purposes. In this report, we describe our design and fabrication of two PMMA-based microfluidic chips for investigating cellular responses, in the production of reactive oxygen species and the migration, under single or coexisting chemical/electrical/shear stress stimuli. The first chip generates five relative concentrations of 0, 1/8, 1/2, 7/8, and 1 in the culture regions, together with a shear stress gradient produced inside each of these areas. The second chip generates the same relative concentrations, but with five different electric field strengths created within each culture area. These devices not only provide cells with a precise, controllable micro-environment but also greatly increase the experimental throughput.

Micro-fabricated devices integrated with fluidic components provide an in vitro platform for cell studies mimicking the in vivo micro-environment. We developed polymethylmethacrylate-based microfluidic chips for studying cellular responses under single or coexisting chemical/electrical/shear stress stimuli.

Projetando microfluídicos para Estudar respostas celulares Sob único ou coexistindo Chemical / Elétrica / tensão de cisalhamento Estímulos

Microfluidic devices are capable of creating a precise and controllable cellular micro-environment of pH, temperature, salt concentration, and other ...

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-passo fotolitografia Variável Altura para Valved multicamada microfluídicos Devices

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