Os autores gostariam de agradecer ao Conselho de Ciências Naturais e Pesquisa de Engenharia do Canadá, Canadá programa de Cátedras de Pesquisa, Institutos Canadenses de Pesquisa em Saúde, e Ontário Ministério da Investigação e da Inovação através de seu Programa de investigadores em início Prêmio de apoio financeiro.

1. Fotolitografia para Master Mold Fabricação <ol><li> Banho de 3 cm da bolacha de silício em acetona durante 30 segundos e em seguida com metanol, durante 30 seg. Enxágüe com dH 2 0 água por 5 min. </li><li> Seque a superfície do wafer com uma pistola de ar N2. Aquece-se a bolacha em uma chapa quente a 140 ° C durante 2 min. </li><li> Plasma oxidar a superfície da bolacha de silício (1 min, 50 W). </li><li> A superfície da bolacha de spin-revestimento com 3 ml SU-8 100 fotossensível (40 seg; 1.750 rpm). </li><li> Pré-coze a pastilha revestida sobre uma placa quente a 65 ° C durante 10 min, depois rampa a temperatura até 95 ° C ao longo de 2 min. Manter essa configuração para uma 1 hora adicional. </li><li> Alinhar um photomask contendo o projeto do canal desejado. Expor a resistir a 550-600 mJ / cm 2 de luz UV (350-400 nm). Máscaras podem ser projetados em AutoCAD e impresso em uma transparência com impressão de alta resolução. </li><li> Pós-cozer a bolacha sobre uma placa quente a 65 ° C durante 1 min e 95 ° C durante 10 min, rampa tele temperatura como antes. </li><li> Mergulhe o wafer em SU-8 solução reveladora por 10-15 min. Verifique para a conclusão do desenvolvimento de lavagem com isopropanol. Se um precipitado branco aparece, continuar a desenvolver. O molde mestre é mostrado na Figura 2A. </li></ol> 2. Litografia suave para Fabricação de microcanais <ol><li> Misture 35 ml polidimetilsiloxano (PDMS), base de elastômero com 3,5 ml de agente de cura PDMS. </li><li> Coloque o molde mestre fabricado (padrão para cima) e uma pastilha de silício em branco em placas de Petri forradas com papel alumínio. </li><li> Verter 20 mL de pré-polímero de PDMS no prato molde mestre e 15 ml no segundo prato. Eliminar bolsões de ar sob os wafers pressionando suavemente sobre eles com um aplicador de madeira descartáveis. </li><li> Cubra ambos os pratos e reserve um dia para curar. Alternativamente, para a cura mais rápida, remover as bolhas de ar do PDMS usando um desgaseificador a vácuo e depois deixam-se os pratos em uma placa quente a 80 ° C durante 2hr. </li><li> Retire o papel alumínio e retire o PDMS das bolachas. </li><li> Utilizar a Harris Uni-Core (2,5 mm) para perfurar aberturas de acesso de fluidos em ambas as extremidades do canal. Corte o canal e branco PDMS em tiras de tamanho similar. </li><li> Carregar o canal, a tira de placa de PDMS e uma lâmina de vidro (75 x 25 mm 2) no plasma de um oxidante, provavelmente localizado numa sala limpa. Expor a plasma de oxigênio por 40 segundos a 40 W de potência. </li><li> Furar a peça de canal e lâmina de vidro para os lados opostos da tira de placa. Retiradas para 2 horas para completar a ligação. </li><li> Coloque a montagem sobre uma placa quente a 120 ° C. Anexar tubos de plástico (diâmetro interno de 1/32 &quot;, o diâmetro exterior de 3/32&quot;), cada um, pelo menos, 6 cm de comprimento, com os reservatórios perfurados que utilizam pré-polímero de PDMS. Apor um conector de plástico fluídico para um ou ambos os tubos para permitir a ligação da seringa, ou utilizar acessórios disponíveis comercialmente. </li><li> Permitir que o PDMS proteger a tubulação para curar. Insira 3 &quot;comprimentos de calibre 22 fio de cobre isolado em each reservatório, entre o tubo de entrada e o canal, e seguro, com pré-polímero de PDMS. O produto final é mostrado na Figura 2B. </li></ol> 3. Electrotaxis Experiment <ol><li> Coloque a microcanais na fase (de preferência XY-móvel) de um microscópio com uma câmara montada ligada a um monitor (Figura 1). </li><li> Ligue a fonte de alimentação ou fios de saída do amplificador para os eletrodos do microcanais. Uma simples fonte de alimentação DC é suficiente que apenas um sinal de corrente contínua for desejado, mas de um amplificador conectado a um gerador de funções permite a aplicação de sinais AC e DC pulsada bem. </li><li> Aplica o tubo de saída do microcanal para uma seringa descartável. Imergir a boca do tubo de entrada em M9 tampão fisiológico e suavemente aspirar o líquido para dentro do canal por aplicação de uma pressão negativa no interior da seringa (quer manualmente ou utilizando uma bomba de seringa). Quando os tubos de entrada e de saída são ambas cheias com M9, desligar a seringa from o tubo. Nivelar os dois tubos para a mesma altura para impedir o fluxo de acionamento hidrostático. </li><li> Aplicar uma tensão de CC para o canal e garantir que a resistência (R = V / I) é de cerca de 0,6 mohms (para uma redução de 50 mm de comprimento, 0,3 milímetros de largura e -0,1 mm de profundidade microcanal). </li><li> Se estiver satisfeito com a integridade do canal, siga os passos acima para carregar os vermes de uma suspensão diluída para o canal. </li><li> Retirar a seringa e hidrostática manipular o fluxo ajustando altura relativa dos tubos. É este método para colocar um sem-fim no centro do canal e, em seguida, colocar ambos os tubos no mesmo plano de elevação. </li><li> Definir o fornecimento de energia para a tensão apropriada: 4-12 V / cm, para os animais fase L3, 4-10 V / cm, e para L4s 2-4 V / cm, para os adultos jovens. Ative o sinal elétrico e permitir que 1 min de pré-exposição para o worm para se aclimatar ao campo. O worm deve começar a se mover em direção ao cátodo. Quando o minuto passou, usar a câmera para começar a gravar. </li><li> Para AC e pulsoexperimentos d CC, o campo elétrico resposta máxima pode ser adotada a partir do ciclo do sinal acima e freqüência e duty pode ser modulada como desejado 7, 8. </li><li> Quando o experimento for concluído, remova todo o líquido (e vermes) do canal, lave-o com dH 2 0, e deixar o dispositivo em uma placa quente a 125 ° C para secar. </li><li> Extrair dados locomotores de vídeos gravados manualmente usando NIH ImageJ ( <a href="http://rsbweb.nih.gov/ij/" target="_blank">http://rsbweb.nih.gov/ij/</a> ) ou software de monitoramento verme baseada em MATLAB personalizado. </li></ol>

<ol>
	<li>Kuwahara, T., Koyama, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Familial+Parkinson+mutant+&#945;-synuclein+causes+dopamine+neuron+dysfunction+in+transgenic+Caenorhabditis+elegans.">Familial Parkinson mutant &#945;-synuclein causes dopamine neuron dysfunction in transgenic Caenorhabditis elegans.</a> J. Biol. Chem. 281 (1), 334-340 (2006).</li><li>Kuwahara, T., Koyama, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+systematic+RNAi+screen+reveals+involvement+of+endocytic+pathway+in+neuronal+dysfunction+in+a-synuclein+transgenic.">A systematic RNAi screen reveals involvement of endocytic pathway in neuronal dysfunction in a-synuclein transgenic.</a> 17 (19), 2997-3009 (2008).</li><li>Su, L. J., Auluck, P. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compounds+from+an+unbiased+chemical+screen+reverse+both+ER-to-Golgi+trafficking+defects+and+mitochondrial+dysfunction+in+Parkinson's+disease+models.">Compounds from an unbiased chemical screen reverse both ER-to-Golgi trafficking defects and mitochondrial dysfunction in Parkinson's disease models.</a> Dis. Model Mech. 3 (3-4), 194-208 (2010).</li><li>Rezai, P., Siddiqui, A., Selvaganapathy, P. R., Gupta, B. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrotaxis+of+Caenorhabditis+elegans+in+a+microfluidic+environment.">Electrotaxis of Caenorhabditis elegans in a microfluidic environment.</a> Lab Chip. 10 (2), 220-226 (2010).</li><li>Salam, S., Ansari, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+microfluidics+set+up+to+study+neuronal+degeneration+and+identification+of+neuroprotective+compounds+in+C.+elegans.">A microfluidics set up to study neuronal degeneration and identification of neuroprotective compounds in C. elegans.</a> , (2013).</li><li>Rezai, P., Salam, S., Selvaganapathy, P. R., Gupta, B. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrical+sorting+of+Caenorhabditis+elegans.">Electrical sorting of Caenorhabditis elegans.</a> Lab Chip. 12 (10), 1831-1840 (2012).</li><li>Rezai, P., Salam, S., Selvaganapathy, P. R., Gupta, B. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+pulse+direct+current+signals+on+electrotactic+movement+of+nematodes+Caenorhabditis+elegans+and+Caenorhabditis+briggsae.">Effect of pulse direct current signals on electrotactic movement of nematodes Caenorhabditis elegans and Caenorhabditis briggsae.</a> Biomicrofluidics. 5 (4), 044116 (2011).</li><li>Rezai, P., Siddiqui, A., Selvaganapathy, P. R., Gupta, B. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Behavior+of+Caenorhabditis+elegans+in+alternating+electric+field+and+its+application+to+their+localization+and+control.">Behavior of Caenorhabditis elegans in alternating electric field and its application to their localization and control.</a> Appl. Phys. Lett. 96 (15), 153702 (2010).</li><li>van Ham, T. J., Thijssen, K. L., Breitling, R., Hofstra, R. M., Plasterk, R. H., Nollen, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=C.+elegans+model+identifies+genetic+modifiers+of+alpha-synuclein+inclusion+formation+during+aging.">C. elegans model identifies genetic modifiers of alpha-synuclein inclusion formation during aging.</a> PLoS Genet. 4, e1000027 (2008).</li><li>Brenner, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+genetics+of+Caenorhabditis+elegans.">The genetics of Caenorhabditis elegans.</a> Genetics. 77 (1), 71-94 (1974).</li><li>Gabel, C. V., Gabel, H., Pavlichin, D., Kao, A., Clark, D. A., Samuel, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+circuits+mediate+electrosensory+behavior+in+Caenorhabditis+elegans.">Neural circuits mediate electrosensory behavior in Caenorhabditis elegans.</a> J. Neurosci. 27 (28), 7586-7596 (2007).</li><li>Chuang, H. -. S., Raizen, D. M., Lamb, A., Dabbish, N., Bau, H. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dielectrophoresis+of+Caenorhabditis+elegans.">Dielectrophoresis of Caenorhabditis elegans.</a> Lab Chip. 11 (4), 599-604 (2011).</li><li>Cronin, C. J., Mendel, J. E., Mukhtar, S., Kim, Y. -. M., Stirbl, R. C., Bruck, J., Sternberg, P. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+automated+system+for+measuring+parameters+of+nematode+sinusoidal+movement.">An automated system for measuring parameters of nematode sinusoidal movement.</a> BMC Genet. 6, 5 (2005).</li><li>Mani&#232;re, X., Lebois, F., Matic, I., Ladoux, B., Meglio, J. -. M. D. i., Hersen, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Running+worms:+C.+elegans+self-sorting+by+electrotaxis.">Running worms: C. elegans self-sorting by electrotaxis.</a> PLoS One. 6 (2), e16637 (2011).</li></ol>

A tecnologia de ensaio electrotaxis microfluídicos foi apresentado para a patente nos Estados Unidos da América e Canadá.

Aproveitando-se do fenômeno comportamental descrita pela primeira vez por Gabel e colegas e com base no trabalho de manipulação dieletroforética de Chuang e colegas 11,12, nosso ensaio electrotaxis baseado em microfluídica fornece um método fácil, robusto e sensível para investigar a atividade neuronal em vermes usando o movimento como uma saída. A análise dos parâmetros de movimento permite a comparação quantitativa entre os diferentes genótipos. A precisão de fabrico de microcanais e aplicaç...

<table border="1">
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		<tr>
			<td>Name of the reagent</td>
			<td>Company</td>
			<td>Catalogue number</td>
			<td>Comments (optional)</td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>CALEDON Labs</td>
			<td>1200-1-30</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>CALEDON Labs</td>
			<td>6700-1-30</td>
			<td>&nbsp;</td>
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			<td>Isopropanol</td>
			<td>CALEDON Labs</td>
			<td>8600-1-40</td>
			<td>&nbsp;</td>
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			<td>SU-8</td>
			<td>Microchem Corp.</td>
			<td>Y131273</td>
			<td>SU-8 100</td>
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			<td>SU-8 Developer</td>
			<td>Microchem Corp.</td>
			<td>Y020100</td>
			<td>&nbsp;</td>
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			<td>92x16 mm Petri dish</td>
			<td>Sarstedt</td>
			<td>82.1473.001</td>
			<td>&nbsp;</td>
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		<tr>
			<td>Sylgard 184 Silicone Elastomer Kit</td>
			<td>Dow Corning</td>
			<td>&nbsp;</td>
			<td>Contains elastomer base and curing agent</td>
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			<td>Function generator</td>
			<td>Tektronix Inc.</td>
			<td>&nbsp;</td>
			<td>Model AFG3022B</td>
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			<td>Amplifier</td>
			<td>Trek Inc.</td>
			<td>&nbsp;</td>
			<td>Model 2210-CE</td>
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			<td>Syringe pump</td>
			<td>Harvard Apparatus</td>
			<td>70-4506</td>
			<td>Model 11 ELITE</td>
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			<td>Hot plate</td>
			<td>Fisher Scientific</td>
			<td>11675916Q</td>
			<td>Model HP131725Q</td>
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</table>

microfluidic-based electrotaxis for on-demand quantitative analysis of caenorhabditis elegans' locomotion

Os nemátodo Caenorhabditis elegans é um organismo modelo versátil para a investigação biomédica devido à sua conservação dos genes e vias relacionadas com a doença, bem como a sua facilidade de cultivo. Vários C. elegans modelos da doença têm sido relatados, incluindo desordens neurodegenerativas tais como a doença de Parkinson (PD), que envolve a degeneração de dopaminérgica (DA) neurónios 1. Ambos os transgenes e produtos químicos neurotóxicos têm sido utilizados para induzir a neurodegeneração promotor e consequentes defeitos de circulação em vermes, permitindo investigações sobre a base da neurodegeneração e telas para os genes e compostos neuroprotectores 2,3. Telas em eucariotos mais baixas, como C. elegans proporcionar um meio eficiente e econômico para identificar os compostos e os genes que afetam a sinalização neuronal. Telas convencionais normalmente são realizados manualmente e marcado por inspeção visual e, conseqüentemente, eles são tempo-consuming e propenso a erros humanos. Além disso, a maior enfoque na análise nível celular, ignorando a locomoção, que é um parâmetro muito importante para desordens de movimento. Desenvolvemos um novo sistema de rastreio de microfluidos (Figura 1), que controla e quantifica C. locomoção elegans &#39;usando estímulos campo elétrico no interior de microcanais. Mostrámos que um campo de corrente contínua (DC) pode induzir robustamente on-demand locomoção para o cátodo (&quot;electrotaxis&quot;) 4. Invertendo a polaridade do campo faz com que o worm para reverter rapidamente a sua direção. Também mostrámos que os defeitos em neurónios sensoriais e outros dopaminérgicos alterar a resposta de natação 5. Portanto, anormalidades na sinalização neuronal pode ser determinada utilizando a locomoção como uma leitura. A resposta de movimento podem ser quantificados com precisão, utilizando uma gama de parâmetros, tais como velocidade de natação, corpo frequência de flexão e do tempo de reversão. <p class = &quot;jove_content&quot;&gt; O trabalho revelou que a resposta electrotactic varia com a idade. Especificamente, os jovens respondem a uma menor variedade de campos elétricos e se mover mais rápido em comparação com larvas de 4. Estes resultados levaram-nos a projetar um novo dispositivo micro para classificar passivamente vermes por idade e fenótipo 6. Também testamos a resposta de vermes para pulsado DC e alternada campos de corrente elétrica (AC). DC campos pulsados ​​de vários ciclos electrotaxis efetivamente gerados, tanto C. elegans e seu primo C. briggsae 7. Numa outra experiência, os campos AC simétricas, com frequências que vão de 1 Hz a 3 kHz vermes imobilizada no interior do canal 8. Implementação do campo elétrico em um ambiente de microfluídica permite a execução rápida e automatizada do ensaio electrotaxis. Esta abordagem promete facilitar telas genéticas e químicas de alto rendimento para os fatoresafetando a função neuronal e viabilidade.

Um vídeo representante electrotaxis um nematóide adulto jovem do tipo selvagem e sua posição e saídas de velocidade a partir do software de rastreamento verme são mostrados na Suplementar Video 1 e Figura 3. O próprio software de análise de movimento não reconhece a direção da polaridade do campo eo tempo de inversão de polaridade, mas sim, esta informação deve ser obtido a partir da fonte de vídeo. Isso pode ser feito usando um taco de áudio ou visual no vídeo ou escre...

Watch this Scientific Journal Video about Microfluidic-based Electrotaxis for On-demand Quantitative Analysis of Caenorhabditis elegans' Locomotion at JoVE.com

Microfluidic-based Electrotaxis for On-demand Quantitative Analysis of Caenorhabditis elegans&#039; Locomotion

Um método de micro-electro-fluídico semi-automatizado para induzir a demanda de locomoção em<em&gt; Caenorhabditis elegans</em&gt; É descrito. Este método baseia-se no fenómeno neurophysiologic de vermes respondem a campos eléctricos ligeiros (&quot;electrotaxis&quot;) no interior de canais microfluidicos. Microfluidic electrotaxis serve como um baixo custo, e escalável técnica rápida, sensível, para triagem de fatores que afetam a saúde neuronal.

Electrotaxis baseados em microfluídica para análise quantitativa On-demand de<em&gt; Caenorhabditis elegans</em&gt; &#39;Locomotion

The nematode Caenorhabditis elegans is a versatile model organism for biomedical research because of its conservation of disease-related genes and ...

microfluidic-based-electrotaxis-for-on-demand-quantitative-analysis

Research

JoVE Journal

Bioengineering

Microfluidic-based Electrotaxis for On-demand Quantitative Analysis of Caenorhabditis elegans' Locomotion

9.7K visualizações.  McMaster University. Um método de micro-electro-fluídico semi-automatizado para induzir a demanda de locomoção em Caenorhabditis elegans É descrito. Este método baseia-se no fenómeno neurophysiologic de vermes respondem a campos eléctricos ligeiros ("electrotaxis") no interior de canais microfluidicos. Microfluidic electrotaxis serve como um baixo custo, e escalável técnica rápida, sensível, para triagem de fatores que afetam a saúde neuronal.

Vídeo: Microfluidic-based Electrotaxis for On-demand Quantitative Analysis of Caenorhabditis elegans' Locomotion

Improved Visualization and Quantitative Analysis of Drug Effects Using Micropatterned Cells

To date, most HCA (High Content Analysis) studies are carried out with adherent cell lines grown on a homogenous substrate in tissue-culture treated micro-plates. Under these conditions, cells spread and divide in all directions resulting in an inherent variability in cell shape, morphology and behavior. The high cell-to-cell variance of the overall population impedes the success of HCA, especially for drug development. The ability of micropatterns to normalize the shape and internal polarity of every individual cell provides a tremendous opportunity for solving this critical bottleneck 1-2.
To facilitate access and use of the micropatterning technology, CYTOO has developed a range of ready to use micropatterns, available in coverslip and microwell formats. In this video article, we provide detailed protocols of all the procedures from cell seeding on CYTOOchip micropatterns, drug treatment, fixation and staining to automated acquisition, automated image processing and final data analysis. With this example, we illustrate how micropatterns can facilitate cell-based assays. Alterations of the cell cytoskeleton are difficult to quantify in cells cultured on homogenous substrates, but culturing cells on micropatterns results in a reproducible organization of the actin meshwork due to systematic positioning of the cell adhesion contacts in every cell. Such normalization of the intracellular architecture allows quantification of even small effects on the actin cytoskeleton as demonstrated in these set of protocols using blebbistatin, an inhibitor of the actin-myosin interaction.

Adhesive micropatterns that normalize cellular architecture can be used to increase sensitivity in the detection of drug effects, improve reproducibility and simplify automated image acquisition and analysis. Such technology will benefit drug/siRNA screening assays, performed on conventional cell culture supports and consequently suffering from excessive cell-to-cell variability.

Visualização melhorada e Análise Quantitativa dos Efeitos de Drogas Usando Células micropatterned

To date, most HCA (High Content Analysis) studies are carried out with adherent cell lines grown on a homogenous substrate in tissue-culture treated ...

Bioengenharia

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 ...

Quantitative Locomotion Study of Freely Swimming Micro-organisms Using Laser Diffraction

Soil and aquatic microscopic organisms live and behave in a complex three-dimensional environment. Most studies of microscopic organism behavior, in contrast, have been conducted using microscope-based approaches, which limit the movement and behavior to a narrow, nearly two-dimensional focal field.1 We present a novel analytical approach that provides real-time analysis of freely swimming C. elegans in a cuvette without dependence on microscope-based equipment. This approach consists of tracking the temporal periodicity of diffraction patterns generated by directing laser light through the cuvette. We measure oscillation frequencies for freely swimming nematodes.
Analysis of the far-field diffraction patterns reveals clues about the waveforms of the nematodes. Diffraction is the process of light bending around an object. In this case light is diffracted by the organisms. The light waves interfere and can form a diffraction pattern. A far-field, or Fraunhofer, diffraction pattern is formed if the screen-to-object distance is much larger than the diffracting object. In this case, the diffraction pattern can be calculated (modeled) using a Fourier transform.2
C. elegans are free-living soil-dwelling nematodes that navigate in three dimensions. They move both on a solid matrix like soil or agar in a sinusoidal locomotory pattern called crawling and in liquid in a different pattern called swimming.3 The roles played by sensory information provided by mechanosensory, chemosensory, and thermosensory cells that govern plastic changes in locomotory patterns and switches in patterns are only beginning to be elucidated.4 We describe an optical approach to measuring nematode locomotion in three dimensions that does not require a microscope and will enable us to begin to explore the complexities of nematode locomotion under different conditions.

Microscopic organisms like the free-swimming nematode C. elegans, live and behave in a complex three-dimensional environment. We report on a novel approach that provides analysis of C. elegans using diffraction patterns. This approach consists of tracking the temporal periodicity of diffraction patterns generated by directing laser light through a cuvette.

Estudo quantitativo de locomoção livremente Natação Micro-organismos Usando Difração Laser

Soil and aquatic microscopic organisms live and behave in a complex three-dimensional environment. Most studies of microscopic organism behavior, in ...

Quantitative FRET (F&#246;rster Resonance Energy Transfer) Analysis for SENP1 Protease Kinetics Determination

Reversible posttranslational modifications of proteins with ubiquitin or ubiquitin-like proteins (Ubls) are widely used to dynamically regulate protein activity and have diverse roles in many biological processes. For example, SUMO covalently modifies a large number or proteins with important roles in many cellular processes, including cell-cycle regulation, cell survival and death, DNA damage response, and stress response 1-5. SENP, as SUMO-specific protease, functions as an endopeptidase in the maturation of SUMO precursors or as an isopeptidase to remove SUMO from its target proteins and refresh the SUMOylation cycle 1,3,6,7.
The catalytic efficiency or specificity of an enzyme is best characterized by the ratio of the kinetic constants, kcat/KM. In several studies, the kinetic parameters of SUMO-SENP pairs have been determined by various methods, including polyacrylamide gel-based western-blot, radioactive-labeled substrate, fluorescent compound or protein labeled substrate 8-13. However, the polyacrylamide-gel-based techniques, which used the "native" proteins but are laborious and technically demanding, that do not readily lend themselves to detailed quantitative analysis. The obtained kcat/KM from studies using tetrapeptides or proteins with an ACC (7-amino-4-carbamoylmetylcoumarin) or AMC (7-amino-4-methylcoumarin) fluorophore were either up to two orders of magnitude lower than the natural substrates or cannot clearly differentiate the iso- and endopeptidase activities of SENPs.
Recently, FRET-based protease assays were used to study the deubiquitinating enzymes (DUBs) or SENPs with the FRET pair of cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) 9,10,14,15. The ratio of acceptor emission to donor emission was used as the quantitative parameter for FRET signal monitor for protease activity determination. However, this method ignored signal cross-contaminations at the acceptor and donor emission wavelengths by acceptor and donor self-fluorescence and thus was not accurate.
We developed a novel highly sensitive and quantitative FRET-based protease assay for determining the kinetic parameters of pre-SUMO1 maturation by SENP1. An engineered FRET pair CyPet and YPet with significantly improved FRET efficiency and fluorescence quantum yield, were used to generate the CyPet-(pre-SUMO1)-YPet substrate 16. We differentiated and quantified absolute fluorescence signals contributed by the donor and acceptor and FRET at the acceptor and emission wavelengths, respectively. The value of kcat/KM was obtained as (3.2 &plusmn; 0.55) x107 M-1s-1 of SENP1 toward pre-SUMO1, which is in agreement with general enzymatic kinetic parameters. Therefore, this methodology is valid and can be used as a general approach to characterize other proteases as well.

Quantitative FRET F&amp;#246;rster Resonance Energy Transfer Analysis for SENP1 Protease Kinetics Determination

A novel method involving quantitative analysis of FRET (F&ouml;rster Resonance Energy Transfer) signals is described for studying enzyme kinetics. KM and kcat were obtained for the hydrolysis of the catalytic domain of SENP1 (SUMO/Sentrin specific protease 1) to pre-SUMO1 (Small Ubiquitin-like MOdifier). The general principles of this quantitative-FRET-based protease kinetic study can be applied to other proteases.

Quantitativa FRET (Förster Resonance Energy Transfer) Análise para SENP1 Determinação Cinética Protease

Reversible posttranslational modifications of proteins with ubiquitin or ubiquitin-like proteins (Ubls) are widely used to dynamically regulate protein ...

Drug-induced Sensitization of Adenylyl Cyclase: Assay Streamlining and Miniaturization for Small Molecule and siRNA Screening Applications

Sensitization of adenylyl cyclase (AC) signaling has been implicated in a variety of neuropsychiatric and neurologic disorders including substance abuse and Parkinson&#39;s disease. Acute activation of G&#945;i/o-linked receptors inhibits AC activity, whereas persistent activation of these receptors results in heterologous sensitization of AC and increased levels of intracellular cAMP. Previous studies have demonstrated that this enhancement of AC responsiveness is observed both in vitro and in vivo following the chronic activation of several types of G&#945;i/o-linked receptors including D2 dopamine and &#956; opioid receptors. Although heterologous sensitization of AC was first reported four decades ago, the mechanism(s) that underlie this phenomenon remain largely unknown. The lack of mechanistic data presumably reflects the complexity involved with this adaptive response, suggesting that nonbiased approaches could aid in identifying the molecular pathways involved in heterologous sensitization of AC. Previous studies have implicated kinase and Gb&#947; signaling as overlapping components that regulate the heterologous sensitization of AC. To identify unique and additional overlapping targets associated with sensitization of AC, the development and validation of a scalable cAMP sensitization assay is required for greater throughput. Previous approaches to study sensitization are generally cumbersome involving continuous cell culture maintenance as well as a complex methodology for measuring cAMP accumulation that involves multiple wash steps. Thus, the development of a robust cell-based assay that can be used for high throughput screening (HTS) in a 384&#160;well format would facilitate future studies. Using two D2 dopamine receptor cellular models (i.e.&#160;CHO-D2L and HEK-AC6/D2L), we have converted our 48-well sensitization assay (&#62;20 steps 4-5 days) to a five-step, single day assay in 384-well format. This new format is amenable to small molecule screening, and we demonstrate that this assay design can also be readily used for reverse transfection of siRNA in anticipation of targeted siRNA library screening.

Persistent activation of inhibitory G protein-coupled receptors results in sensitization of adenylyl cyclase signaling. To identify the essential molecular pathways, nonbiased approaches are necessary; however, this strategy requires the development of a scalable cell-based cAMP sensitization assay. Herein, we describe a sensitization assay for small molecule and siRNA screening.

Induzida por drogas Sensibilização de adenililciclase: Racionalização Ensaio e miniaturização para pequenas moléculas e siRNA Triagem Applications

Sensitization of adenylyl cyclase (AC) signaling has been implicated in a variety of neuropsychiatric and neurologic disorders including substance abuse ...

A Microfluidic-based Electrochemical Biochip for Label-free DNA Hybridization Analysis

Miniaturization of analytical benchtop procedures into the micro-scale provides significant advantages in regards to reaction time, cost, and integration of pre-processing steps. Utilizing these devices towards the analysis of DNA hybridization events is important because it offers a technology for real time assessment of biomarkers at the point-of-care for various diseases. However, when the device footprint decreases the dominance of various physical phenomena increases. These phenomena influence the fabrication precision and operation reliability of the device. Therefore, there is a great need to accurately fabricate and operate these devices in a reproducible manner in order to improve the overall performance. Here, we describe the protocols and the methods used for the fabrication and the operation of a microfluidic-based electrochemical biochip for accurate analysis of DNA hybridization events. The biochip is composed of two parts: a microfluidic chip with three parallel micro-channels made of polydimethylsiloxane (PDMS), and a 3 x 3 arrayed electrochemical micro-chip. The DNA hybridization events are detected using electrochemical impedance spectroscopy (EIS) analysis. The EIS analysis enables monitoring variations of the properties of the electrochemical system that are dominant at these length scales. With the ability to monitor changes of both charge transfer and diffusional resistance with the biosensor, we demonstrate the selectivity to complementary ssDNA targets, a calculated detection limit of 3.8 nM, and a 13% cross-reactivity with other non-complementary ssDNA following 20 min&#160;of incubation. This methodology can improve the performance of miniaturized devices by elucidating on the behavior of diffusion at the micro-scale regime and by enabling the study of DNA hybridization events.

We present a microfluidic-based electrochemical biochip for DNA hybridization detection. Following ssDNA probe functionalization, the specificity, sensitivity, and detection limit are studied with complementary and non-complementary ssDNA targets. Results illustrate the influence of the DNA hybridization events on the electrochemical system, with a detection limit of 3.8 nM.

A Biochip eletroquímica microfluídica à base de Análise de hibridação DNA livre-Label

Miniaturization of analytical benchtop procedures into the micro-scale provides significant advantages in regards to reaction time, cost, and integration ...

Electrotaxis Studies of Lung Cancer Cells using a Multichannel Dual-electric-field Microfluidic Chip

The behavior of directional cell migration under a direct current electric-field (dcEF) is referred to as electrotaxis. The significant role of physiological dcEF in guiding cell movement during embryo development, cell differentiation, and wound healing has been demonstrated in many studies. By applying microfluidic chips to an electrotaxis assay, the investigation process is shortened and experimental errors are minimized. In recent years, microfluidic devices made of polymeric substances (e.g., polymethylmethacrylate, PMMA, or acrylic) or polydimethylsiloxane (PDMS) have been widely used in studying the responses of cells to electrical stimulation. However, unlike the numerous steps required to fabricate a PDMS device, the simple and rapid construction of the acrylic micro&#64258;uidic chip makes it suitable for both device prototyping and production. Yet none of the reported devices facilitate the efficient study of the simultaneous chemical and dcEF effects on cells. In this report, we describe our design and fabrication of an acrylic-based multichannel dual-electric-field (MDF) chip to investigate the concurrent effect of chemical and electrical stimulation on lung cancer cells. The MDF chip provides eight combinations of electrical/chemical stimulations in a single test. The chip not only greatly shortens the required experimental time but also increases accuracy in electrotaxis studies.

Many microfluidic devices have been developed for use in the study of electrotaxis. Yet, none of these chips allows the efficient study of the simultaneous chemical and electric-field (EF) effects on cells. We developed a polymethylmethacrylate-based device that offers better-controlled coexisting EF and chemical stimulation for use in electrotaxis research.

Electrotaxis Estudos de pulmão células de câncer usando um Multichannel Dual-elétrico-campo Microfluidic Chip

The behavior of directional cell migration under a direct current electric-field (dcEF) is referred to as electrotaxis. The significant role of ...

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 detecção de fluorescência para Gota microfluídica Utilizando 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 ...

An Efficient and Reproducible Protocol for Distraction Osteogenesis in a Rat Model Leading to a Functional Regenerated Femur

This protocol describes the use of a newly developed external fixator for distraction osteogenesis in a rat femoral model. Distraction osteogenesis (DO) is a surgical technique leading to bone regeneration after an osteotomy. The osteotomized extremities are moved away from each other by gradual distraction to reach the desired elongation. This procedure is widely used in humans for lower and upper limb lengthening, treatment after a bone nonunion, or the regeneration of a bone defect following surgery for bone tumor excision, as well as in maxillofacial reconstruction. Only a few studies clearly demonstrate the efficiency of their protocol in obtaining a functional regenerated bone, i.e., bone that will support physiological weight-bearing without fracture after removal of the external fixator. Moreover, protocols for DO vary and reproducibility is limited by lack of information, making comparison between studies difficult. The aim of this study was to develop a reproducible protocol comprising an appropriate external fixator design for rat limb lengthening, with a detailed surgical technique that permits physiological weight-bearing by the animal after removal of the external fixator.

This study describes a reproducible and detailed protocol using a newly developed external fixator for distraction osteogenesis (DO) in a femoral rat model which permits physiological weight-bearing by the animal after removal of the external fixator.

Um protocolo eficiente e reprodutível para distração osteogênese em um modelo de rato, levando a um fêmur regenerada funcional

This protocol describes the use of a newly developed external fixator for distraction osteogenesis in a rat femoral model. Distraction osteogenesis (DO) ...

A Microfluidic Platform for Longitudinal Imaging in Caenorhabditis elegans

In the last decade, microfluidic techniques have been applied to study small animals, including the nematode Caenorhabditis elegans, and have proved useful as a convenient live imaging platform providing capabilities for precise control of experimental conditions in real time. In this article, we demonstrate live imaging of individual worms employing WormSpa, a previously-published custom microfluidic device. In the device, multiple worms are individually confined to separate chambers, allowing multiplexed longitudinal surveillance of various biological processes. To illustrate the capability, we performed proof-of-principle experiments in which worms were infected in the device with pathogenic bacteria, and the dynamics of expression of immune response genes and egg laying were monitored continuously in individual animals. The simple design and operation of this device make it suitable for users with no previous experience with microfluidic-based experiments. We propose that this approach will be useful for many researchers interested in longitudinal observations of biological processes under well-defined conditions.

A Microfluidic Platform for Longitudinal Imaging in Caenorhabditis elegans

In this article, we demonstrate live imaging of individual worms employing a custom microfluidic device. In the device, multiple worms are individually confined to separate chambers, allowing multiplexed longitudinal surveillance of various biological processes.

Uma plataforma Microfluidic para Imaging Longitudinal em Caenorhabditis elegans

In the last decade, microfluidic techniques have been applied to study small animals, including the nematode Caenorhabditis elegans, and have proved ...