Kind gift of THP-1 cells from Dr. Mark Chong and assistance in microfabrication from Dr. Yuejun Kang and Dr. Nishanth V. Menon (School of Chemical and Biomedical Engineering, Nanyang Technological University) were greatly acknowledged. This project was funded by NTU-Northwestern Institute of Nanomedicine (Nanyang Technological University). H.W.H. was supported by Lee Kong Chian School of Medicine (LKCMedicine) postdoctoral fellowship.

1. Nanopartículas (NPs) Rotulagem de células-tronco mesenquimais e monócitos <ol><li> as células estaminais mesenquimais Cultura (MSCs) em meio de Eagle modificado por Dulbecco (DMEM) suplementado com 10% de soro fetal de bovino (SFB) e antibióticos para ≥80% de confluência antes da marcação. Do mesmo modo, a cultura de células THP-1 (ATCC) em Roswell Park Memorial Institute (RPMI) 1640 suplementado com FBS a 10% para uma densidade de ~ 10 6 células / ml. </li><li> NPs de carga de sílica (~ 500 mm) com uma solução de corante calceina (200 ^ M) usando agitação durante a noite. Fabricar AM PLGA-calceína (CAM), utilizando um protocolo descrito anteriormente. 22 <ol><li> Dissolve-se 250 ug CAM e 100 mg de PLGA (50:50) em clorofórmio a 4 ° C. </li><li> Gerar NPs de emulsão única usando um homogeneizador de alta velocidade (13.600 xg, 60 seg) à temperatura ambiente. Evapora-se o clorofórmio em uma capa química (≥3 h) antes da recolha através de centrifugação (3400 xg durante 5 min), lavagem (disti duplasencheram água), a secagem por congelação e armazenamento em -20 ° C. </li></ol></li><li> Incubar CAM-PLGA PN (1 mg) ou nanopartículas de sílica calceina (150 ug) em solução a 0,01% de poli-L-lisina (PLL) à temperatura ambiente durante 15 - 20 min. </li><li> Centrifugar a 3.400 xg durante 5 min para remover o excesso de sobrenadante PLL antes de ressuspensão em 1 ml de NPs de respectivo meio de cultura. </li><li> Incubar os PN com células (MSCs ou THP-1, ~ 1 - 2 x 10 6 células no total) durante aproximadamente 24 horas (0,1 mg mL-1 · concentração rotulagem). </li><li> Dissociar e colheita das MSCs marcadas aderentes utilizando 2 ml de tripsina a 0,25% (5 min, 37 ° C) e diluiu-se com 6 ml de DMEM. Girar as células AT (1000 x g, 4 minutos) e ressuspender a uma concentração de 10 junho 05-10 células / ml para o processamento de microfluidos. Utilização de células THP-1 marcadas (10 junho 05-10 células / ml) directamente para a purificação de microfluidos. </li></ol> 2. Preparação Dispositivo de microfluidos <ol><li> fabricação de dispositivos <ol><li> Fabricar o dispositivo microfluídico espiral (500 mm (w) × 115 mm (h)) com polidimetilsiloxano (PDMS) a partir de um kit comercial utilizando etapas padrão litografia macia. 23 </li><li> Misture 30 g de pré-polímero de base e 3 g agente de cura completamente em um barco de pesagem. De gás-se a mistura num excicador durante 60 minutos para remover quaisquer bolhas de ar. </li><li> Verter a mistura de PDMS sobre o molde mestre de bolacha de silicone modelado com o design do canal espiral cuidadosamente a uma altura de aproximadamente 5 - 10 mm. </li><li> De gás-se a mistura no vácuo exsicador durante 60 minutos novamente para remover quaisquer bolhas de ar. Repetir o processo até que todas as bolhas são eliminados. </li><li> Curar a mistura PDMS num forno de 80 ° C durante 2 horas até que o PDMS está definido. Assegurar a bolacha não é inclinado durante a cura ter uma altura constante dispositivo. </li><li> Cortar o dispositivo espiral PDMS utilizando um bisturi e retire cuidadosamente a laje de PDMS do molde mestre. </li><li> Trim as bordas do dispositivo com um bisturi para assegurar a superfície lisa para a colagem. </li><li> Perfurar dois buracos (1,5 mm) para as entradas e dois orifícios (1,5 mm) para as saídas no dispositivo de PDMS utilizando um perfurador de biópsia de 1,5 mm. </li><li> Lavar o dispositivo com isopropanol (IPA) para remover todos os detritos e secar o dispositivo num forno de 80 ° C durante 5 min. </li><li> Limpar a superfície inferior do dispositivo de PDMS (com características de canal) usando fita adesiva. </li><li> um lado limpo de uma lâmina de vidro (2 &quot;por 3&quot;) usando fita adesiva. </li><li> Com cuidado, coloque e expor as superfícies limpas do dispositivo PDMS e lâmina de vidro na câmara de um aspirador de plasma e submetê-las a vácuo durante 60 segundos. Em seguida, ligue a corrente de plasma para o máximo e reduzir a pressão da câmara até que a câmara se transforma na cor rosa. <ol><li> Expor as superfícies a plasma de ar durante 60 segundos. O plasma cria espécies reactivas sobre as superfícies expostas dos PDMS e vidros, que permite a ligação apertada quando posta em físicocontato al. Desligue a alimentação de plasma e liberar a pressão do limpador de plasma para recuperar o dispositivo e vidro slide. </li></ol></li><li> Unir o dispositivo de PDMS e lâmina de vidro em conjunto, pressionando as superfícies expostas ao plasma firmemente e assegurar que não há bolhas estão presos entre as duas superfícies. </li><li> Aquecer o dispositivo ligado usando uma chapa quente fixada em 80 ° C durante 2 h para reforçar a ligação. </li></ol></li><li> Operação dispositivo <ol><li> Cortar duas peças de tubagem (1,52 mm de diâmetro externo) de ~ 15 - 20 cm para as seringas de entrada e anexar uma ponta de seringa (calibre 23) sobre uma extremidade de cada tubo. </li><li> Cortar duas peças de tubagem (1,52 mm de diâmetro externo) de ~ 5 - 10 cm para as tomadas e para prender os orifícios de saída do dispositivo de PDMS. </li><li> Antes da amostra de funcionamento, o dispositivo manualmente privilegiada com uma seringa contendo 70% de etanol, até que flui para fora do tubo de saída. Permitir que a sente de etanol durante 30 segundos a 1 min para esterilizar o dispositivo. </li><li> Carregar 30 ml de filtrou(0,2 uM de poro) tampão de bainha (fosfato-salino tamponado (PBS) com 0,1% de albumina de soro bovino (BSA)) para a seringa de 60 ml e fixar a seringa numa bomba de seringa. Definir a bomba para as configurações corretas (tamanho Seringa: 60 ml, Volume: 60.000 ul). Nota: A adição de BSA para PBS é minimizar ligação à célula-célula e a ligação não específica entre as células e o dispositivo de PDMS. </li><li> Carga 3 ml de células marcadas para a seringa de 3 ml e fixar a seringa numa bomba de seringa separada. Definir a bomba para as configurações corretas (tamanho Seringa: 3 ml, Volume: 3,000 L). </li><li> Verifique se não há bolhas de ar presas nas seringas para assegurar um fluxo estável. Remover quaisquer bolhas de ar por ejecção de suavemente algumas gotas de líquido para fora do bocal. </li><li> Ligue as pontas de seringa de entrada e tubulação para as seringas, e inseri-los nas respectivas entradas do dispositivo (bainha e de entrada da amostra). Certifique-se que não há bolhas ao longo da tubulação. </li><li> Montar os dispositivos em um invertidoEd microscópio de contraste de fase para imagens em tempo real durante o processo de separação de células. </li><li> Garantir um pequeno copo de resíduos e dois tubos de 15 ml perto do dispositivo no palco microscópio usando adesivos. </li><li> Coloque os tubos de saída para o copo de resíduos. </li><li> Definir a razão de escoamento para a amostra para tampão de bainha a 1:10 e comece a ambas as bombas de seringa para iniciar o processo de triagem (Exemplo: 120 ul / min durante seringa amostra e 1200 ul / min durante seringa bainha; velocidade de fluxo do canal ~ 0,38 m / seg ). </li><li> Executar o dispositivo durante 1,5 min para a taxa de fluxo para estabilizar. Isso pode ser confirmado pela presença de células inercial focadas próximo da parede interior do canal sob o brilhante-campo com contraste de fase com uma câmera de alta velocidade (~ 5.000 - 10.000 quadros por segundo (fps), tempo de exposição: 10-50 ms). </li><li> Posicione os tubos de saída em diferentes tubos para recolher os eluentes da tomada celular e saída de resíduos. </li></ol></li></ol>

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Os autores não têm nada para revelar.

A tecnologia de purificação de célula DFF aqui descrita permite a separação rápida e contínua de células marcadas de um modo de elevado rendimento. Esta abordagem é ideal para a separação do volume da amostra ou grande processamento de amostras alta concentração de células, e é melhor do que a filtração à base de membrana convencional, que é propenso ao entupimento após uso prolongado. Da mesma forma, a separação magnética baseados em afinidade requer passos adicionais de rotulagem de células que...

Engenharia células, carregado por agente micro / nanopartículas (NPs) é um método livre de integração, e versátil simples, genômica para melhorar a capacidade bioimaging e aumentar / complementar suas propriedades terapêuticas nativas em medicina regenerativa. 1-3 modificações celulares são alcançados por rotular o membrana plasmática ou citoplasma com um excesso de concentração de NPs carregado por agente para saturar os locais de ligação. No entanto, uma grande desvantagem deste método é a de quantidades significativas de partículas não ligadas que permanece em solução depois de processos de rotulagem de células, que podem potencialmente confundir identificação precisa das células de engenharia de partículas ou complicam resultados terapêuticos 4,5. Além disso, a exposição aos PN contendo transformador agentes (fatores de crescimento, corticosteróides, etc.) em excessivamente alta concentração pode causar citotoxicidade ea exposição mal direcionada pode induzir consequências indesejadas sobre as células não-alvo. Mesmo os transportadores em partículas que compreendem of materiais &quot;biocompatíveis&quot; [por exemplo, poli (ácido co-glicólico), PLGA] pode incitar respostas celulares imunes potentes, em determinadas condições, assim. 6 Este é especialmente perigosa em indivíduos com imunidade diminuída (por exemplo, artrite reumatóide), susceptível de atrasos depuração sistémica de nanopartículas. 7 Assim, a remoção eficiente de partículas livres, antes da introdução das células de engenharia de partículas é de grande importância para minimizar o perfil de toxicidade e reduzir a exposição a partículas carregadas mal dirigido por agente in vivo. centrifugação em gradiente convencional é muitas vezes usado para separar as células manipuladas de partículas livres, mas é trabalhoso e operado em modo de lote. Além disso, tensões de cisalhamento experimentado pelas células durante a centrifugação de alta velocidade e os elementos constituintes do meio de gradiente de densidade pode comprometer a integridade celular e / ou o comportamento das células influência. 8 microfluídica é uma alternativa atraente, com sevtecnologias de separação rais, incluindo deslocamento lateral determinista (DLD) 9, dieletrophoresis 10,11 e acoustophoresis 12 desenvolvido para a separação de partículas pequenas e aplicações de troca de tampão. No entanto, estes métodos sofrem de baixa taxa de transferência (1-10 ul · min - 1) e são propensos a problemas de entupimento. separações activa, tais como os métodos baseados em dieletroforese também requerem diferenças em fenótipos celulares dieletroforética intrínsecas ou passos adicionais de rotulagem de células para conseguir a separação. Uma abordagem mais promissora envolve microfluídica inercial - a migração lateral de partículas ou células através agiliza a concentrar-se em posições distintas devido a forças de sustentação dominantes (F L) com alto número de Reynolds (Re) 13 Devido às suas condições de alto fluxo e resolução de tamanho superior. , tem sido frequentemente explorados para aplicações de câmbio baseada em tamanho separação de células 14,15 e tampão. 16-18 However, desempenho troca de tampão continua pobre com uma solução contaminante ~10-30% como as células separadas geralmente permanecem perto da fronteira entre soluções originais e novas tampão. 16-18 Mais importante ainda, a distribuição do tamanho das células-alvo deve ser semelhante para alcançar inercial uma focagem precisa e a separação a partir da solução tampão original, que constitui um problema especialmente no processamento de tipos heterogéneos de tamanho de células, tais como células estaminais mesenquimais (MSCs). 19 Temos desenvolvido anteriormente uma nova técnica célula microfluídica inercial de classificação denominado Dean Fluxo Fracionamento (DFF) para isolar células tumorais circulantes (CTCs) 20 e bactérias 21 do sangue total usando a 2 de entrada, dispositivo de microcanal espiral 2-outlet. Neste protocolo de vídeo, iremos descrever o processo de rotulagem de células THP-1 (linha celular de leucemia aguda monocítica humana) monocíticas suspensão (~ 15? M) e MSC (10-30 um) com calceina-lNPs oaded, seguido de fabricação e operação do microdispositivo espiral DFF para a recuperação eficiente de células marcadas e remoção de NPs de não ligados. 22 Esta estratégia de purificação de um só passo permite uma recuperação contínua de suspensão rotulado e as células aderentes em suspensão numa solução tampão fresco sem centrifugação. Além disso, ele pode processar até 10 milhões de células · ml -1, uma densidade de células susceptíveis de aplicações de medicina regenerativa.

<table border="0" cellpadding="0" cellspacing="0" width="781">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:780px;">Cell lines &#38; Media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Mesenchymal Stem Cells (MSCs)</td>
			<td style="width:127px;">Lonza</td>
			<td style="width:119px;">PT-2501</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Dulbecco&#8217;s modified Eagle&#8217;s medium (DMEM)</td>
			<td style="width:127px;">Lonza</td>
			<td style="width:119px;">12-614F</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Fetal Bovine Serum (FBS)</td>
			<td style="width:127px;">Gibco</td>
			<td style="width:119px;">10270-106</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">THP-1 monocyte cells (THP-1)</td>
			<td style="width:127px;">ATCC</td>
			<td style="width:119px;">TIB-202</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Roswell Park Memorial Institute (RPMI) 1640 media</td>
			<td style="width:127px;">Lonza</td>
			<td style="width:119px;">12-702F</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Name</td>
			<td style="width:127px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td>Comments/Description</td>
		</tr>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:780px;">Reagents &#38; Materials</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">0.01% poly-L-lysine (PLL)</td>
			<td style="width:127px;">Sigma-Aldrich</td>
			<td style="width:119px;">P8920</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">3 mL Syringe</td>
			<td style="width:127px;">BD</td>
			<td style="width:119px;">302113</td>
			<td>Syringe 3ml Luer-Lock</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">60 ml Syringe</td>
			<td style="width:127px;">BD</td>
			<td style="width:119px;">309653</td>
			<td>Syringe 60ml Luer-Lock</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Bovine Serum Albumin (BSA)</td>
			<td style="width:127px;">Biowest</td>
			<td style="width:119px;">P6154-100GR</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Calcein, AM (CAM)</td>
			<td style="width:127px;">Life Technologies</td>
			<td style="width:119px;">C1430</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Calcein</td>
			<td style="width:127px;">Sigma-Aldrich</td>
			<td style="width:119px;">C0875</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Isopropanol</td>
			<td style="width:127px;">Fisher Chemical</td>
			<td style="width:119px;">#P/7507/17</td>
			<td>HPLC Grade 2.5 L</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Phosphate-Buffered Saline (PBS)</td>
			<td style="width:127px;">Lonza</td>
			<td style="width:119px;">17-516Q/12</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Plain Microscope Slides</td>
			<td style="width:127px;">Fisher Scientific</td>
			<td style="width:119px;">FIS#12-550D</td>
			<td>75 X 25 X 1 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Polydimethylsiloxane (PDMS)</td>
			<td style="width:127px;">Dow Corning</td>
			<td style="width:119px;">SYLGARD&#174; 184</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Scotch tape</td>
			<td style="width:127px;">3M</td>
			<td style="width:119px;">21200702044</td>
			<td>18mm x 25m</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Silica NPs (&#8764;200 &#956;m)</td>
			<td style="width:127px;">Sigma-Aldrich</td>
			<td style="width:119px;">748161</td>
			<td>Pore size 4 nm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Syringe Tip</td>
			<td style="width:127px;">JEC Technology</td>
			<td style="width:119px;">7018302</td>
			<td style="width:167px;">23GA .013 X .25</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Trypsin-EDTA (0.25%)</td>
			<td style="width:127px;">Life Technologies</td>
			<td style="width:119px;">25200-056</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Tygon Tubing</td>
			<td style="width:127px;">Spectra-Teknik</td>
			<td style="width:119px;">06419-01</td>
			<td>.02X.06&#34; 100</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:368px;">Name</td>
			<td style="width:127px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td>Comments/Description</td>
		</tr>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:780px;">Equipment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Biopsy punch</td>
			<td style="width:127px;">Harris Uni-Core</td>
			<td>69036-15</td>
			<td>1.50 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Dessicator</td>
			<td style="width:127px;">Scienceware</td>
			<td style="width:119px;">111/4 IN OD</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">High-speed Camera</td>
			<td style="width:127px;">Phantom&#160;</td>
			<td style="width:119px;">V9.1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Inverted phase-contrast microscope&#160;</td>
			<td style="width:127px;">Nikon</td>
			<td>Eclipse Ti</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Plasma cleaner</td>
			<td style="width:127px;">Harrick Plasma</td>
			<td style="width:119px;">PDC-002</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Syringe Pump</td>
			<td style="width:127px;">Chemyx</td>
			<td style="width:119px;">CX Fusion 200</td>
			<td></td>
		</tr>
	</tbody>
</table>

microfluidic buffer exchange for interference-free micro/nanoparticle cell engineering

células de engenharia com micro ativo-ingrediente-carregado / nanopartículas (NPs) está se tornando um método cada vez mais popular para melhorar as propriedades terapêuticas nativos, permitem imagiologia bio e controlar fenótipo celular. Um problema crítico é ainda tratado de forma inadequada ao número significativo de partículas que permanecem não ligados após a marcação de células que não podem ser facilmente removidas por centrifugação convencional. Isto leva a um aumento do ruído de fundo de imagem bio e pode conferir efeitos de transformação em células não alvo vizinhos. Neste protocolo, apresentamos uma estratégia inercial baseada em microfluidics tampão de câmbio denominado como Dean Fluxo Fracionamento (DFF) para separar eficientemente células marcadas de NPs livres de uma forma de alto rendimento. O microdispositivo espiral desenvolvido facilita a recolha contínua (&gt; recuperação de células de 90%) das células purificadas (THP-1 e MSCs) suspensas em solução tampão nova, ao conseguir% depleção de corante fluorescente não ligado ou NPs tingem-carregado (sil&gt; 95ica ou PLGA). Este único passo, estratégia de purificação de células à base de tamanho permite que o rendimento de processamento de alta celular (10 6 células / min) e é altamente útil para a purificação de células de grande volume de células micro / nanopartículas projetada para alcançar uma aplicação clínica livre de interferências.

Após a marcação das células com bio-imagem NPs carregado agente durante a noite, as células marcadas (que contém partículas livres) são colhidos e purificados por DFF espiral microdispositivo para remover NPs livres num processo de etapa (Figura 1A). O 2-entrada, microcanal espiral 2-outlet foi concebido pelo software de engenharia e microfabricados usando SU-8 fotorresiste. A bolacha de silício modelado é depois utilizado como um molde para moldagem por PDMS r...

Watch this Scientific Journal Video about Microfluidic Buffer Exchange for Interference-free Micro/Nanoparticle Cell Engineering at JoVE.com

Microfluidic Buffer Exchange for Interference-free Micro/Nanoparticle Cell Engineering

Este protocolo descreve o uso de uma estratégia de troca de tampão à base de microfluidos inercial para purificar as células manipuladas micro / nanopartículas com depleção eficaz de partículas não ligadas.

Microfluídico troca de tampão para Micro / nanopartículas celular Engenharia sem interferências

Engineering cells with active-ingredient-loaded micro/nanoparticles (NPs) is becoming an increasingly popular method to enhance native therapeutic ...

microfluidic-buffer-exchange-for-interference-free-micronanoparticle

Research

JoVE Journal

Bioengineering

9.0K visualizações.  Nanyang Technological University.  Este protocolo descreve o uso de uma estratégia de troca de tampão à base de microfluidos inercial para purificar as células manipuladas micro / nanopartículas com depleção eficaz de partículas não ligadas. 

Vídeo: Microfluidic Buffer Exchange for Interference-free Micro/Nanoparticle Cell Engineering

Site-specific Bacterial Chromosome Engineering: &#934;C31 Integrase Mediated Cassette Exchange (IMCE)

The bacterial chromosome may be used to stably maintain foreign DNA in the mega-base range1. Integration into the chromosome circumvents issues such as plasmid replication, plasmid stability, plasmid incompatibility, and plasmid copy number variance. This method uses the site-specific integrase from the Streptomyces phage (&Phi;) C312,3. The &Phi;C31 integrase catalyzes a direct recombination between two specific DNA sites: attB and attP (34 and 39 bp, respectively)4. This recombination is stable and does not revert5. A "landing pad" (LP) sequence consisting of a spectinomycin- resistance gene, aadA (SpR), and the E. coli &szlig;-glucuronidase gene (uidA) flanked by attP sites has been integrated into the chromosomes of Sinorhizobium meliloti, Ochrobactrum anthropi, and Agrobacterium tumefaciens in an intergenic region, the ampC locus, and the tetA locus, respectively. S. meliloti is used in this protocol. Mobilizable donor vectors containing attB sites flanking a stuffer red fluorescent protein (rfp) gene and an antibiotic resistance gene have also been constructed. In this example the gentamicin resistant plasmid pJH110 is used. The rfp gene6 may be replaced with a desired construct using SphI and PstI. Alternatively a synthetic construct flanked by attB sites may be sub-cloned into a mobilizable vector such as pK19mob7. The expression of the &Phi;C31 integrase gene (cloned from pHS628) is driven by the lac promoter, on a mobilizable broad host range plasmid pRK78139.
A tetraparental mating protocol is used to transfer the donor cassette into the LP strain thereby replacing the markers in the LP sequence with the donor cassette. These cells are trans-integrants. Trans-integrants are formed with a typical efficiency of 0.5%. Trans-integrants are typically found within the first 500-1,000 colonies screened by antibiotic sensitivity or blue-white screening using 5-bromo-4-chloro-3-indolyl-beta-D-glucuronic acid (X-gluc). This protocol contains the mating and selection procedures for creating and isolating trans-integrants.

A quick and efficient method to integrate foreign DNA of interest into pre-made acceptor strains, termed landing pad strains, is described. The method allows site-specific integration of a DNA cassette into the engineered landing pad locus of a given strain, through conjugation and expression of the &#934;C31 integrase.

Site-specific Engenharia cromossomo bacteriano: ΦC31 Integrase Mediated Cassette Exchange (IMCE)

The bacterial chromosome may be used to stably maintain foreign DNA in the mega-base range1. Integration into the chromosome circumvents issues such as ...

Bioengenharia

Microfluidic Mixers for Studying Protein Folding

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 for this is that folding takes place over a wide range of timescales, from nanoseconds to seconds or longer, depending on the protein1. Conventional stopped-flow mixers have allowed measurement of folding kinetics starting at about 1 ms. We have recently developed a microfluidic mixer that dilutes denaturant ~100-fold in ~8 &mu;s2. Unlike a stopped-flow mixer, this mixer operates in the laminar flow regime in which turbulence does not occur. The absence of turbulence allows precise numeric simulation of all flows within the mixer with excellent agreement to experiment3-4.
Laminar flow is achieved for Reynolds numbers Re &le;100. For aqueous solutions, this requires micron scale geometries. We use a hard substrate, such as silicon or fused silica, to make channels 5-10 &mu;m wide and 10 &mu;m deep (See Figure 1). The smallest dimensions, at the entrance to the mixing region, are on the order of 1 &mu;m in size. The chip is sealed with a thin glass or fused silica coverslip for optical access. Typical total linear flow rates are ~1 m/s, yielding Re~10, but the protein consumption is only ~0.5 nL/s or 1.8 &mu;L/hr. Protein concentration depends on the detection method: For tryptophan fluorescence the typical concentration is 100 &mu;M (for 1 Trp/protein) and for FRET the typical concentration is ~100 nM.
The folding process is initiated by rapid dilution of denaturant from 6 M to 0.06 M guanidine hydrochloride. The protein in high denaturant flows down a central channel and is met on either side at the mixing region by buffer without denaturant moving ~100 times faster (see Figure 2). This geometry causes rapid constriction of the protein flow into a narrow jet ~100 nm wide. Diffusion of the light denaturant molecules is very rapid, while diffusion of the heavy protein molecules is much slower, diffusing less than 1 &mu;m in 1 ms. The difference in diffusion constant of the denaturant and the protein results in rapid dilution of the denaturant from the protein stream, reducing the effective concentration of the denaturant around the protein. The protein jet flows at a constant rate down the observation channel and fluorescence of the protein during folding can be observed using a scanning confocal microscope5.

In this work we explain the fabrication and use of a microfluidic mixer capable of mixing two solutions in ~8 &mu;s. We also demonstrate the use of these mixers with spectroscopic detection using UV fluorescence and fluorescence resonance energy transfer (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 ...

Systematic Analysis of In Vitro Cell Rolling Using a Multi-well Plate Microfluidic System

A major challenge for cell-based therapy is the inability to systemically target a large quantity of viable cells with high efficiency to tissues of interest following intravenous or intraarterial infusion. Consequently, increasing cell homing is currently studied as a strategy to improve cell therapy. Cell rolling on the vascular endothelium is an important step in the process of cell homing and can be probed in-vitro using a parallel plate flow chamber (PPFC). However, this is an extremely tedious, low throughput assay, with poorly controlled flow conditions. Instead, we used a multi-well plate microfluidic system that enables study of cellular rolling properties in a higher throughput under precisely controlled, physiologically relevant shear flow1,2. In this paper, we show how the rolling properties of HL-60 (human promyelocytic leukemia) cells on P- and E-selectin-coated surfaces as well as on cell monolayer-coated surfaces can be readily examined. To better simulate inflammatory conditions, the microfluidic channel surface was coated with endothelial cells (ECs), which were then activated with tumor necrosis factor-&#945; (TNF-&#945;), significantly increasing interactions with HL-60 cells under dynamic conditions. The enhanced throughput and integrated multi-parameter software analysis platform, that permits rapid analysis of parameters such as rolling velocities and rolling path, are important advantages for assessing cell rolling properties in-vitro. Allowing rapid and accurate analysis of engineering approaches designed to impact cell rolling and homing, this platform may help advance exogenous cell-based therapy.

Systematic Analysis of In Vitro Cell Rolling Using a Multi-well Plate Microfluidic System

This study used a multi-well plate microfluidic system, significantly increasing throughput of cell rolling studies under physiologically relevant shear flow. Given the importance of cell rolling in the multi-step cell homing cascade and the importance of cell homing following systemic delivery of exogenous populations of cells in patients, this system offers potential as a screening platform to improve cell-based therapy.

Análise sistemática de<em&gt; In Vitro</em&gt; Célula de rolamento usando um sistema microfluídicos Multi-bem placa

A major challenge for cell-based therapy is the inability to systemically target a large quantity of viable cells with high efficiency to tissues of ...

Cell Squeezing as a Robust, Microfluidic Intracellular Delivery Platform

Rapid mechanical deformation of cells has emerged as a promising, vector-free method for intracellular delivery of macromolecules and nanomaterials. This technology has shown potential in addressing previously challenging applications; including, delivery to primary immune cells, cell reprogramming, carbon nanotube, and quantum dot delivery. This vector-free microfluidic platform relies on mechanical disruption of the cell membrane to facilitate cytosolic delivery of the target material. Herein, we describe the detailed method of use for these microfluidic devices including, device assembly, cell preparation, and system operation. This delivery approach requires a brief optimization of device type and operating conditions for previously unreported applications. The provided instructions are generalizable to most cell types and delivery materials as this system does not require specialized buffers or chemical modification/conjugation steps. This work also provides recommendations on how to improve device performance and trouble-shoot potential issues related to clogging, low delivery efficiencies, and cell viability.

Rapid mechanical deformation of cells has emerged as a promising, vector-free method for intracellular delivery of macromolecules and nanomaterials. This protocol provides detailed steps on how to use the system for a broad range of applications.

Espremendo celular como uma plataforma de entrega intracelular Robust Microfluidic

Rapid mechanical deformation of cells has emerged as a promising, vector-free method for intracellular delivery of macromolecules and nanomaterials. This ...

A Microfluidic Technique to Probe Cell Deformability

Here we detail the design, fabrication, and use of a microfluidic device to evaluate the deformability of a large number of individual cells in an efficient manner. Typically, data for ~102 cells can be acquired within a 1 hr experiment. An automated image analysis program enables efficient post-experiment analysis of image data, enabling processing to be complete within a few hours. Our device geometry is unique in that cells must deform through a series of micron-scale constrictions, thereby enabling the initial deformation and time-dependent relaxation of individual cells to be assayed. The applicability of this method to human promyelocytic leukemia (HL-60) cells is demonstrated. Driving cells to deform through micron-scale constrictions using pressure-driven flow, we observe that human promyelocytic (HL-60) cells momentarily occlude the first constriction for a median time of 9.3 msec before passaging more quickly through the subsequent constrictions with a median transit time of 4.0 msec per constriction. By contrast, all-trans retinoic acid-treated (neutrophil-type) HL-60 cells occlude the first constriction for only 4.3 msec before passaging through the subsequent constrictions with a median transit time of 3.3 msec. This method can provide insight into the viscoelastic nature of cells, and ultimately reveal the molecular origins of this behavior.

We demonstrate a microfluidics-based assay to measure the timescale for cells to transit through a sequence of micron-scale constrictions.

A técnica de microfluídica para sondar Deformabilidade celular

Here we detail the design, fabrication, and use of a microfluidic device to evaluate the deformability of a large number of individual cells in an ...

Controlled Microfluidic Environment for Dynamic Investigation of Red Blood Cell Aggregation

Blood, as a non-Newtonian biofluid, represents the focus of numerous studies in the hemorheology field. Blood constituents include red blood cells, white blood cells and platelets that are suspended in blood plasma. Due to the abundance of the RBCs (40% to 45% of the blood volume), their behavior dictates the rheological behavior of blood especially in the microcirculation. At very low shear rates, RBCs are seen to assemble and form entities called aggregates, which causes the non-Newtonian behavior of blood. It is important to understand the conditions of the aggregates formation to comprehend the blood rheology in microcirculation. The protocol described here details the experimental procedure to determine quantitatively the RBC aggregates in microcirculation under constant shear rate, based on image processing. For this purpose, RBC-suspensions are tested and analyzed in 120 x 60 &#181;m poly-dimethyl-siloxane (PDMS) microchannels. The RBC-suspensions are entrained using a second fluid in order to obtain a linear velocity profile within the blood layer and thus achieve a wide range of constant shear rates. The shear rate is determined using a micro Particle Image Velocimetry (&#181;PIV) system, while RBC aggregates are visualized using a high speed camera. The videos captured of the RBC aggregates are analyzed using image processing techniques in order to determine the aggregate sizes based on the images intensities.

The protocol described details an experimental procedure to quantify Red Blood Cell (RBC) aggregates under a controlled and constant shear rate, based on image processing techniques. The goal of this protocol is to relate RBC aggregate sizes to the corresponding shear rate in a controlled microfluidic environment.

Ambiente Microfluidic controlada de Investigação dinâmico de Agregação Glóbulo Vermelho

Blood, as a non-Newtonian biofluid, represents the focus of numerous studies in the hemorheology field. Blood constituents include red blood cells, white ...

Using Adhesive Patterning to Construct 3D Paper Microfluidic Devices

We demonstrate the use of patterned aerosol adhesives to construct both planar and nonplanar 3D paper microfluidic devices. By spraying an aerosol adhesive through a metal stencil, the overall amount of adhesive used in assembling paper microfluidic devices can be significantly reduced. We show on a simple 4-layer planar paper microfluidic device that the optimal adhesive application technique and device construction style depends heavily on desired performance characteristics. By moderately increasing the overall area of a device, it is possible to dramatically decrease the wicking time and increase device success rates while also reducing the amount of adhesive required to keep the device together. Such adhesive application also causes the adhesive to form semi-permanent bonds instead of permanent bonds between paper layers, enabling single-use devices to be non-destructively disassembled after use. Nonplanar 3D origami devices also benefit from the semi-permanent bonds during folding, as it reduces the likelihood that unrelated faces may accidently stick together. Like planar devices, nonplanar structures see reduced wicking times with patterned adhesive application vs uniformly applied adhesive.

We demonstrate the use of patterned aerosol adhesives to construct 3D paper microfluidic devices. This method of adhesive application forms semi-permanent bonds between layers, enabling single-use devices to be non-destructively disassembled after use and to ease folding complex nonplanar structures.

Usando Adhesive Padronização Construir 3D de papel microfluídicos

We demonstrate the use of patterned aerosol adhesives to construct both planar and nonplanar 3D paper microfluidic devices. By spraying an aerosol ...

A Microfluidic Platform for High-throughput Single-cell Isolation and Culture

Studying the heterogeneity of single cells is crucial for many biological questions, but is technically difficult. Thus, there is a need for a simple, yet high-throughput, method to perform single-cell culture experiments. Here, we report a microfluidic chip-based strategy for high-efficiency single-cell isolation (~77%) and demonstrate its capability of performing long-term single-cell culture (up to 7 d) and cellular heterogeneity analysis using clonogenic assay. These applications were demonstrated with KT98 mouse neural stem cells, and A549 and MDA-MB-435 human cancer cells. High single-cell isolation efficiency and long-term culture capability are achieved by using different sizes of microwells on the top and bottom of the microfluidic channel. The small microwell array is designed for precisely isolating single-cells, and the large microwell array is used for single-cell clonal culture in the microfluidic chip. This microfluidic platform constitutes an attractive approach for single-cell culture applications, due to its flexibility of adjustable cell culture spaces for different culture strategies, without decreasing isolation efficiency.

Here, we present a protocol for isolating and culturing single cells with a microfluidic platform, which utilizes a new microwell design concept to allow for high-efficiency single cell isolation and long-term clonal culture.

Uma plataforma microfluídica para a isolação de alta taxa de transferência de célula única e Cultura

Studying the heterogeneity of single cells is crucial for many biological questions, but is technically difficult. Thus, there is a need for a simple, yet ...

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 ...

Microfluidic Bioprinting for Engineering Vascularized Tissues and Organoids

Engineering vascularized tissue constructs and organoids has been historically challenging. Here we describe a novel method based on microfluidic bioprinting to generate a scaffold with multilayer interlacing hydrogel microfibers. To achieve smooth bioprinting, a core-sheath microfluidic printhead containing a composite bioink formulation extruded from the core flow and the crosslinking solution carried by the sheath flow, was designed and fitted onto the bioprinter. By blending gelatin methacryloyl (GelMA) with alginate, a polysaccharide that undergoes instantaneous ionic crosslinking in the presence of select divalent ions, followed by a secondary photocrosslinking of the GelMA component to achieve permanent stabilization, a microfibrous scaffold could be obtained using this bioprinting strategy. Importantly, the endothelial cells encapsulated inside the bioprinted microfibers can form the lumen-like structures resembling the vasculature over the course of culture for 16 days. The endothelialized microfibrous scaffold may be further used as a vascular bed to construct a vascularized tissue through subsequent seeding of the secondary cell type into the interstitial space of the microfibers. Microfluidic bioprinting provides a generalized strategy in convenient engineering of vascularized tissues at high fidelity.

We provide a generalized protocol based on a microfluidic bioprinting strategy for engineering a microfibrous vascular bed, where a secondary cell type could be further seeded into the interstitial space of this microfibrous structure to generate vascularized tissues and organoids.

Microfluídico troca de tampão para Micro / nanopartículas celular Engenharia sem interferências

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