笔者想感谢自然科学和工程研究理事会，加拿大，加拿大研究主席，加拿大卫生研究院，安大略省研究与创新部通过他们的早期研究者奖计划提供财政支持。

1。主模具制造的光刻<ol><li>沐浴3英寸硅晶片，在丙酮中30秒，然后用甲醇，持续30秒。 DH 2 0水冲洗5分钟。 </li><li>用氮气吹尘枪，晶圆表面干燥。晶片在140℃的热板上加热2分钟。 </li><li>等离子氧化在硅晶片的表面上（1分钟，50瓦）。 </li><li>旋涂晶圆的表面有3毫升SU-8 40秒100的光致抗蚀剂（1750转）。 </li><li>的热板上预烘焙涂布的晶片在65℃下进行10分钟，然后坡道温度95℃2分钟。保持此设置为1小时。 </li><li>将含有所需的信道设计的光掩模。揭露抵抗550-600兆焦耳/厘米2的紫外光（350-400纳米）。光掩膜的设计可以在AutoCAD上的透明度和打印用的高分辨率印刷。 </li><li>晶片的热板上烘烤后，在65℃1分钟，95℃下10分钟，升温吨他前的温度。 </li><li>晶圆浸泡在SU-8显影液10-15分钟。开发完成后用异丙醇冲洗检查。如果出现白色沉淀物，继续发展。 图2A所示的母模。 </li></ol> 2。软光刻技术微通道的制备<ol><li> PDMS固化剂用3.5毫升，混合35毫升的聚二甲基硅氧烷（PDMS）弹性体基地。 </li><li>将制作母模（图案朝上）和一个空白硅片到培养皿内衬铝箔。 </li><li>进入到第二盘的模具师傅菜和15毫升，倒入20毫升PDMS预聚物。用一次性木制涂药轻轻按下消除气泡下方的晶圆。 </li><li>既包括菜肴和预留一天治愈。另外，对于固化速度更快，使用的真空脱气装置从PDMS去除气泡，然后离开，在80℃的热板上的菜2小时。 </li><li>移除箔和从晶片剥离的PDMS。 </li><li>使用哈里斯统一核（2.5毫米），以冲头的流体的通道两端的接入端口。切通道和空白PDMS成同样大小的条。 </li><li>加载通道，空白的硅橡胶条和玻璃载片（75×25毫米2）成等离子体氧化剂，有可能设在洁净室中。暴露于氧等离子体，持续40秒，在40 W功率。 </li><li>棒的通道片和玻璃载片空白带的相对两侧。预留2小时来完成粘合。 </li><li>将组件上的热板上在120℃下将塑料管（内径1/32“，外直径为3/32”），每一个至少6英寸长，冲压水库使用PDMS的预聚物。贴上流体的塑料连接器连接到一个或两个管子允许注射器附件，或使用市售配件。 </li><li>允许的PDMS固定管治愈。插入3“长度的22轨距绝缘的铜线到EACħ水库，入口管和通道之间，并与PDMS的预聚物的安全。 图2B中所示的成品。 </li></ol> 3。 Electrotaxis实验<ol><li>将微流路连接的监视器（ 图1）的安装的摄像机的显微镜上的阶段（优选为XY-可动）。 </li><li>连接电源或放大器的输出线连接到微通道的电极。一个简单的直流稳压电源是足够的，如果是理想的，但只有一个DC信号的放大器连接到一个函数发生器的脉冲直流信号和交流信号，以及允许应用程序。 </li><li>将微通道的输出管一次性注射器。淹没口的入口管M9的生理缓冲液中，并轻轻地向往液体通过施加在注射器内形成负压（手动或使用注射泵）进入通道。当入口和出口管都充满了M9，断开的注射器fROM管。双侧输卵管级到相同的高度，以防​​止水压驱动的流动。 </li><li>施加直流电压的信道和，确保电阻（R = V / I）大约是0.6MΩ（5​​0毫米长，0.3毫米宽，0.1毫米深的微流路）。 </li><li>如果满意通道的完整性，按照上面的步骤，从稀释悬浮液进入通道加载蠕虫。 </li><li>拔下注射器和水压操作流程，通过调整管的相对高度。使用此方法蠕虫放置在中心的通道，然后在同一高度，奠定两个管平。 </li><li>设置适当的电压电源：4-12 V / cm的L3级动物，4-10 V / cm的L4S和2-4 V / cm的青壮年。激活的电信号，并允许蜗杆以适应字段的预曝光1分钟。该蠕虫病毒开始向阴极移动。当一分钟后，可以使用相机开始记录。 </li><li>对于交流和脉冲字直流实验的最大响应电场，可以采用从上述频率和占空比的信号进行调制，然后随意7，8。 </li><li>实验结束时，从通道中移除所有液体（和蠕虫），用dH 2 O漂洗，将本装置的热板上，在125℃下干燥。 </li><li>运动器官提取数据从录制的视频使用NIH ImageJ的（ <a href="http://rsbweb.nih.gov/ij/" target="_blank">http://rsbweb.nih.gov/ij/</a> ）的或定制的基于MATLAB的蠕虫跟踪软件。 </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>

微electrotaxis检测技术已申请专利，在美国的美国和加拿大。

趁着加贝尔和他的同事和建设的介电电泳操纵工作的庄和他的同事11,12首次描述的行为现象，我们基于微electrotaxis检测提供了一个简单，强大而灵敏的方法来探测蠕虫使用运动神经元活动一个输出端。运动参数的分析，可以定量比较不同基因型之间。微通道制造和施加电场的精确度提供一个可控的环境和沟通的途径与蜗杆的运动控制。不同的电信号波形具有不同的行为在蜗轮的反射，并已...

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

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

线虫是一种多用途的生物医学研究的模式生物，因为其养护与疾病相关的基因和途径以及其易于栽培。几个C.线虫病模型已被报道，包括神经退行性疾病，如帕金森氏病（PD），这涉及多巴胺能（DA）神经元的变性。两种转基因和神经毒性的化学物质已被用于诱导DA神经退行性疾病和随之而来的运动在蠕虫的缺陷，允许调查的基础的神经退行性疾病和神经保护作用的基因和化合物2,3的屏幕。 在低等真核生物如C屏幕线虫提供高效和经济的手段来影响神经信号化合物的鉴定和基因。传统的屏幕通常手动进行，并取得通过目测，因此，它们是时间的利弊uming和容易出现人为错误。此外，大多数细胞水平分析的焦点，而忽略运动，这是一个特别重要的参数为运动障碍。 我们已经开发了一种新的微流体筛选系统（ 图1），控制和量化C.使用微通道内的电场刺激线虫的运动。我们已经表明，一个直流（DC）字段鲁棒可以诱导按需向阴极运动（“electrotaxis”）4。倒车领域的极性，导致蠕虫迅速扭转方向。我们还表明，多巴胺和其他感觉神经元中的缺陷，改变游泳响应5。因此，在神经元的信号的异常可以使用作为一个读出的运动来确定。采用了一系列的参数，如游泳速度快，身体弯曲次数及拨回时间可以精确量化的运动响应。 4。这些发现使我们能够设计一个新的微流体装置，被动蠕虫排序按年龄和表型6。 我们还测试蠕虫脉冲直流和交流电（AC）的电场响应。各种占空比的脉冲直流领域的有效生成两个C. electrotaxis 线虫和其表弟C. briggsae 7。在另一项实验中，对称的AC字段从1 Hz到3千赫的频率范围固定的通道8内的蠕虫。 执行的微流体环境中的电场使快速和自动地执行的electrotaxis检测。这种方法有望促进高通量遗传因素和化学屏幕影响神经细胞的功能和活力。

有代表性的野生型的年轻成年线虫的的electrotaxis和它的位置和速度输出蠕虫跟踪软件视频补充视频1和图3所示。运动分析软件本身不识别方向的场极性和极性反转的时间，而是必须获得这个信息从源视频。这可以通过使用在视频或音频或视频提示，写下的实验条件和操作。 从野生型（N2）和转基因动物中的一组（NL5901）electrotaxis高速数据将显示在<stron...

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

一个半自动化的微型电流体的方法诱导点播运动<em&gt;线虫</em&gt;进行说明。此方法是基于响应微流体通道内的温和的电场（“electrotaxis）蠕虫的神经生理现象。微流控electrotaxis供​​应快速，灵敏，低成本，可扩展的技术因素，影响神经细胞的健康屏幕。

基于微流体Electrotaxis的，为按需定量分析<em&gt;线虫</em&gt;&#39;LOCOMOTION的

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 次观看.  McMaster University. 一个半自动化的微型电流体的方法诱导点播运动线虫进行说明。此方法是基于响应微流体通道内的温和的电场（“electrotaxis）蠕虫的神经生理现象。微流控electrotaxis供​​应快速，灵敏，低成本，可扩展的技术因素，影响神经细胞的健康屏幕。

视频: 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.

改进的可视化和定量分析，药物使用Micropatterned细胞的影响

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

科研

生物工程

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.

一个单粒子为基础的微流控液力陷阱

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.

使用激光衍射自由游泳微生物的定量步态研究

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.

定量荧光共振能量转移（福斯特共振能量转移）SENP1蛋白酶的动力学测定分析

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.

腺苷酸环化酶的药物引起的过敏性：含量简化和小型化的小分子和siRNA筛选应用

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.

微流体为基础的电化学生物芯片的无标记的DNA杂交分析

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.

使用多通道双电场微流控芯片肺癌细胞Electrotaxis研究

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.

使用多色荧光检测液滴微流控光纤

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.

大鼠牵张成骨的高效可再生性协议

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.

秀丽线虫纵向成像的微流控平台

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