微流体芯片ICPMS进样
Summary
我们提出了一个离散的微滴样品引入系统，用于电感耦合等离子体质谱法（ICPMS）。它是基于一种廉价和一次性的微流体芯片，其生成高度单分散的液滴中的40-60微米的尺寸范围的频率范围从90至7000赫兹上。
Abstract
该协议将讨论一种一次性的低成本微流体芯片作为样品引入系统，用于电感耦合等离子体质谱法（ICPMS）的制造和使用。该芯片生产的全氟（PFH）单分散水样滴。大小，并且将水的液滴的频率可以在40至60微米的范围内和从90到7000赫兹，而变化分别。液滴从芯片喷出PFH的第二流动和喷射期间保持不变。一个定制的脱溶剂系统中删除PFH和运输液滴入ICPMS。这里，具有窄强度分布非常稳定的信号，可测，显示了液滴的单分散性。我们表明，引入系统可用于定量确定在单个牛红细胞的铁。在未来，引进设备的能力可以容易地通过的额外的微流体模块一体化延长。
Introduction
液体样品通过电感耦合等离子体质谱法（ICPMS）元素分析通常进行了使用喷雾器结合雾化室作为介绍系统1。在这个样品引入系统的样品通过喷雾器喷洒以产生多分散的气溶胶。下游雾化室是用来过滤掉大滴。这种方法是用高样品消耗（>0.3毫升分钟-1）2和一个不完整的检体搬送相关联。因而，变得不切实际的应用场合只微升的样品体积是可用的，如在生物，法医，毒理学和临床研究3。为了降低样品的消耗，喷雾器具有较小尺寸的喷嘴被开发3。但是，减小喷嘴尺寸增大堵塞时的未消化生物流体或浓盐溶液的样品必须被分析3的风险。
<p class="“jove_content”">一种不同的方法进行样品引入提出了Olesik 等。4。笔者注入液体到ICPMS在单分散的离散微滴，这是由压电电驱动微泵产生的形式。尽管这个系统并没有得到广泛的应用，它启动了离散液滴引入ICPMS概念的进一步发展。今天，压电电驱动分配系统，它可以在30，50，70和100微米的大小，并在100-2,000赫兹频率产生液滴，就可以买到。液滴可以被输送到ICPMS与接近100％的效率5。这些微滴分配器已申请了定量测定单个纳米颗粒5,6，以及表征个体生物细胞7。基于热喷墨技术8类似的系统，生物样品9的分析测试。虽然阿瓦伊拉布勒单个液滴引入系统是非常有效的，可用于小样品体积，并有望用于纳米颗粒和细胞的分析中，它们有若干限制。对于一个固定的喷嘴尺寸，液滴尺寸可以仅稍微被改变（除非自定义设置用于10）。液体（pH值，盐含量）的物理性质的变化可以改变墨滴的特性（尺寸，注射速度）。此外，这些设备是相当昂贵的，易发生堵塞，并且难以清洁。另一种方法，以产生液滴已知在微流体液滴11的字段。近年来液滴微流控已获得的（生物）化学反应12-15和单细胞研究16,17兴趣。此外，这种技术应用于用于引入在电喷雾质谱18,19的样品和用于制备样品中的基质辅助激光解吸/ ionizatioñ质谱20,21。
最近，我们推出了基于微流体系统中ICPMS 22样品引入。我们引入系统的关键组成部分是辅助液体的液滴喷射（拉德）芯片。这个芯片包括完全的聚（二甲基硅氧烷）（PDMS）。在第一沟道结流动聚焦用于生成的水溶液样品溶液（ 图1）的单分散的液滴。为了这个目的和不混溶的载相全氟己烷（PFH）高挥发性（58-60℃，23沸点）时（ 图1）。这些PFH属性使稳定液滴的产生和快速去除载波相位。变化的样品液体影响本产生方法少的特性，相对于其他液滴发生器。液滴尺寸是可调节的在很宽的范围内，通过改变水相和PFH的流速。在下游secondarÝ结，更PFH被添加以增加流动速度，以至少1m秒-1。在此速度下，液体可以从在稳定和直喷射的芯片（ 图1），而不破坏液滴（ 图1插图）喷射。这双结设计让控制飞机的稳定性独立液滴产生。液滴被输送到ICPMS用定制的运输系统。该系统包括一个下降管和膜desolvator除去PFH。水性液滴的干燥残基被随后电离的等离子体质谱的血浆和质量检测器测量离子。芯片的前部是筒状，以确保与液滴运输系统的紧密连接。水性样品中PFH液滴的喷射是有利的，因为与喷嘴接触得以避免。这大大降低了喷嘴堵塞的危险性，用细胞悬浮液，或共同工作时这可能是一个问题ncentrated盐溶液。在拉德芯片，由PDMS制成软光刻，价格便宜（2材料成本大约为每块芯片），一次性的，容易修改。与仅需要少量的手工工作的制造组合每个实验可以用一个新的芯片来执行。因此，一个费力的清扫不需要和交叉污染最小化。
这里，拉德芯片通过软光刻和其ICPMS应用的制作进行说明。与一种水溶液和细胞悬浮液的测量实例。
Protocol
1. SU-8主控制作（图2） 注：在一个干净的房间，以防止由于灰尘颗粒缺陷执行的SU-8母模的制造。都需要的制造中，一个晶片与微流体特征和一个没有两个晶片。 准备主模具的微流控芯片。首先施加粘合层的硅晶片。 脱水的硅晶片在200℃下10分钟。向下冷却晶片至RT，并用下面的协议将其加载到一个旋涂器和旋涂用的SU-8 2002。 分配约3ml抗蚀到晶片上。 …
Representative Results
所提出的系统可用于测量小体积的溶液或含有细胞或纳米颗粒悬浮液。单细胞的标准溶液和表征测量的实例如下所示。更多的例子可在Verboket 等 22中找到。 典型的溶液中的单个液滴的信号是一个非常短的事件。它通常持续数100微秒26。同这里使用的ICPMS（停留时间10毫秒）这样的短的信号不能被暂时解决。 图7a和图7b示出的?…
Discussion
虽然芯片的制造中是非常可靠的存在需要特别注意的制造过程中的一些关键点。首先，在组装过程中的清洁是非常重要的，以防止该芯片受到灰尘的污染。灰尘可阻断通道，并防止了稳定的液滴的产生。其次，它是特别重要的是，尖端被切割垂直于喷嘴通道。切口的角度强烈影响的喷射角度。如果液体被喷射在一个角度上，会引起喷射的液滴的损失。
当构建设置确保它是稳?…
Divulgazioni
The authors have nothing to disclose.
Acknowledgements
This work was supported by the European Research Council (ERC Starting Grant nμLIPIDS, No. 203428) and ETH Zurich (project number: ETH-49 12-2). The authors of this manuscript would like to thank Bodo Hattendorf for help with the ICP-MS and F. Kurth for cell counting. The authors also would like to thank Christoph Bärtschi and Roland Mäder for their support with building the mechanical setup. The clean room facility FIRST at ETH Zurich is acknowledged for support in microfabrication.
Materials
| Name of Reagent/ Equipment | Company | Catalog Number | Comments/Description |
| Silicon wafer 100 mm | Si-Mat (Kaufering, Germany) | n. a. | |
| SU-8 2002 | Microchem Corp. (Massachusetts, U.S.A.) | n.a. | |
| SU-8 2050 | Microchem Corp. (Massachusetts, U.S.A.) | n.a. | |
| Acetone | Merk VWR (Darmstadt, Germany) | 100014 | |
| MR-developer 600 | Microresist Technology GmbH (Berlin, Germany) | n. a. | |
| Isopropanol | Merk VWR (Darmstadt, Germany) | 109634 | |
| 1H,1H,2H,2H-perfluorodecyltrichlorosilane | ABCR-Chemicals (Karlsruhe, Germany) | AB111155 | |
| Sylgard 184 silicone elastomer kit (PDMS) | Dow Corning (Michigan, U.S.A.) | 39100000 | |
| Perfluorohexane 99% | Sigma-Aldrich (Missouri, U.S.A.) | 281042 | |
| FC-40 | ABCR-Chemicals (Karlsruhe, Germany) | AB103511 | |
| Phosphate-buffered saline | Life Technologies (Paisley, U.K.) | 10010-015 | |
| Red blood cells in phosphate-buffered saline | Rockland Immunochemicals Inc. (Pennsylvania, U.S.A.) | R400-0100 | |
| Single-element standard solutions Na, Fe | Inorganic Ventures (Virginia, U.S.A.) | n. a. | |
| Multielement standard solution | Merck Millipore (Massachusetts, U.S.A.) | IV | |
| Nitric acid | Sub-boiled | n. a. | |
| Ultrahigh-purity water | Merck Millipore (Massachusetts, U.S.A.) | n. a. | |
| Name of Equipment | |||
| Hot plate HP 160 III BM | Sawatec (Sax, Switzerland) | n. a. | used for wafer preparation |
| Spin modules SM 180 BM | Sawatec (Sax, Switzerland) | n. a. | used for wafer preparation |
| MA-6 mask aligner | Süss MicroTec (Garching, Germany) | n. a. | |
| High resolution film photomask | Microlitho (Essex, U.K.) | n. a. | |
| Step profiler Dektak XT advanced | Bruker (Massachusetts, U.S.A.) | n. a. | |
| Hot plate MR 3002 | Heidolph (Schwabach, Germany) | n. a. | used for replica molding |
| 1.5 mm biopsy puncher | Miltex (Pennsylvania, U.S.A.) | 33-31AA/33-31A | |
| Spin coater WS-400 BZ-6NPP/LITE | Laurell (Pennsylvania, U.S.A.) | n. a. | used for adhesive bonding |
| Syringe pump neMESYS | Cetoni (Korbussen, Germany) | n. a. | |
| 1 mL syringe | Codan (Lensahn, Germany) | 62.1002 | |
| 5 mL syringe | B. Braun (Melsungen, Germany) | 4606051V | |
| PTFE tubing | PKM SA (Lyss, Switzerland) | PTFE-AWG-TFT20.N | |
| Quadrupole-based ICPMS ELAN6000 | PerkinElmer (Massachusetts, U.S.A.) | n. a. | |
| Membrane desolvator CETAC6000AT+ | CETAC Technologies (Nebraska, U.S.A.) | n. a. | only the desolvator unit is used |
| High speed camera Miro M110 | Vision Research (New Jersey, U.S.A.) | n. a. | |
| Data analysis program Origin pro | OriginLab Corp. (Massachusetts, U.S.A.) | version 8.6 | |
| Microscope | Olympus (Tokyo, Japan) | IX71 |
Riferimenti
- Todoli, J. -. L., Mermet, J. -. M. . Liquid sample introduction in ICP spectrometry: A Practical Guide. , 10-1016 (2008).
- Sutton, K. L., B’Hymer, C., Caruso, J. A. Ultraviolet absorbance and inductively coupled plasma mass spectrometric detection for capillary electrophoresis – A comparison of detection modes and interface designs. J. Anal. At. Spectrom. 13 (9), 885-891 (1998).
- Todoli, J. -. L., Mermet, J. -. M. Sample introduction systems for the analysis of liquid microsamples by ICP-AES and ICP-MS. Spectrochim. Acta, Part B. 61 (3), 239-283 (2006).
- Olesik, J. W., Hobbs, S. E. Monodisperse dried microparticulate injector – A new tool for studying fundamental processes in inductively-coupled plasma. Anal. Chem. 66 (20), 3371-3378 (1994).
- Gschwind, S., Hagendorfer, H., Frick, D. A., Günther, D. Mass quantification of nanoparticles by single droplet calibration using inductively coupled plasma mass spectrometry. Anal. Chem. 85 (12), 5875-5883 (2013).
- Garcia, C. C., Murtazin, A., Groh, S., Horvatic, V., Niemax, K. Characterization of single Au and SiO2 nano- and microparticles by ICP-OES using monodisperse droplets of standard solutions for calibration. J. Anal. At. Spectrom. 25 (5), 645-653 (2010).
- Shigeta, K., et al. Sample introduction of single selenized yeast cells (Saccharomyces cerevisiae) by micro droplet generation into an ICP-sector field mass spectrometer for label-free detection of trace elements. J. Anal. At. Spectrom. 28 (5), 637-645 (2013).
- Orlandini v. Niessen, J. O., Schaper, J. N., Petersen, J. H., Bings, N. H. Development and characterization of a thermal inkjet-based aerosol generator for micro-volume sample introduction in analytical atomic spectrometry. J. Anal. At. Spectrom. 26 (9), 1781-1789 (2011).
- Orlandini v. Niessen, J. O., Petersen, J. H., Schaper, J. N., Bings, N. H. Comparison of novel and conventional calibration techniques for the analysis of urine samples using plasma source mass spectrometry combined with a new dual-drop-on-demand aerosol generator. J. Anal. At. Spectrom. 27 (8), 1234-1244 (2012).
- Shigeta, K., et al. Application of a micro-droplet generator for an ICP-sector field mass spectrometer – optimization and analytical characterization. J. Anal. At. Spectrom. 28 (5), 646-656 (2013).
- Teh, S. -. Y., Lin, R., Hung, L. -. H., Lee, A. P. Droplet microfluidics. Lab on a Chip. 8 (2), 198-220 (2008).
- Zheng, B., Tice, J. D., Ismagilov, R. F. Formation of arrayed droplets by soft lithography and two-phase fluid flow, and application in protein crystallization. Adv. Mater. 16 (15), 1365-1368 (2004).
- Theberge, A. B., et al. Microfluidic platform for combinatorial synthesis in picolitre droplets. Lab Chip. 12 (7), 1320-1326 (2012).
- Li, L., et al. Nanoliter microfluidic hybrid method for simultaneous screening and optimization validated with crystallization of membrane proteins. Proc. Natl. Acad. Sci. U. S. A. 103 (51), 19243-19248 (2006).
- Zhang, Q., Liu, X., Liu, D., Gai, H. Ultra-small droplet generation via volatile component evaporation. Lab Chip. 14 (8), 1395-1400 (2014).
- Baret, J. C., Beck, Y., Billas-Massobrio, I., Moras, D., Griffiths, A. D. Quantitative cell-based reporter gene assays using droplet-based microfluidics. Chem. Biol. 17 (5), 528-536 (2010).
- Brouzes, E., et al. Droplet microfluidic technology for single-cell high-throughput screening. Proc. Natl. Acad. Sci. U. S. A. 106 (34), 14195-14200 (2009).
- Pei, J., Li, Q., Lee, M. S., Valaskovic, G. A., Kennedy, R. T. Analysis of samples stored as individual plugs in a capillary by electrospray ionization mass spectrometry. Anal. Chem. 81 (15), 6558-6561 (2009).
- Kelly, R. T., Page, J. S., Marginean, I., Tang, K., Smith, R. D. Dilution-free analysis from picoliter droplets by nano-electrospray ionization mass spectrometry. Angew. Chem., Int. Ed. 48 (37), 6832-6835 (2009).
- Küster, S. K., et al. Interfacing droplet microfluidics with matrix-assisted laser desorption/ionization mass spectrometry: label-free content analysis of single droplets. Anal. Chem. 85 (3), 1285-1289 (2013).
- Pabst, M., Jefimovs, K., Zenobi, R., Dittrich, P. S. High-Resolution Droplet-Based Fractionation of Nano-LC Separations onto Microarrays for MALDI-MS Analysis. Analytical Chemistry. 86 (10), 4848-4855 (2014).
- Verboket, P. E., Borovinskaya, O., Meyer, N., Günther, D., Dittrich, P. S. A New Microfluidics-Based Droplet Dispenser for ICPMS. Analytical Chemistry. 86 (12), 6012-6018 (2014).
- Ammerman, C. N., You, S. M. Determination of the boiling enhancement mechanism caused by surfactant addition to water. J. Heat Transfer. 118 (2), 429-435 (1996).
- Samel, B., Chowdhury, M. K., Stemme, G. The fabrication of microfluidic structures by means of full-wafer adhesive bonding using a poly(dimethylsiloxane) catalyst. J Micromech Microeng. 17 (8), 1710-1714 (2007).
- Basu, A. S. Droplet morphometry and velocimetry (DMV): a video processing software for time-resolved, label-free tracking of droplet parameters. Lab Chip. 13 (10), 1892-1901 (2013).
- Dziewatkoski, M. P., Daniels, L. B., Olesik, J. W. Time-resolved inductively coupled plasma mass spectrometry measurements with individual, monodisperse drop sample introduction. Anal. Chem. 68 (7), 1101-1109 (1996).
- Abate, A. R., Hung, T., Mary, P., Agresti, J. J., Weitz, D. A. High-throughput injection with microfluidics using picoinjectors. Proc. Natl. Acad. Sci. U. S. A. 107 (45), 19163-19166 (2010).
- Bremond, N., Thiam, A. R., Bibette, J. Decompressing emulsion droplets favors coalescence. Phys. Rev. Lett. 100 (2), 024501 (2008).
- Niu, X., Gulati, S., Edel, J. B., deMello, A. J. Pillar-induced droplet merging in microfluidic circuits. Lab Chip. 8 (11), 1837-1841 (2008).
- Song, H., Ismagilov, R. F. Millisecond kinetics on a microfluidic chip using nanoliters of reagents. J. Am. Chem. Soc. 125 (47), 14613-14619 (2003).
- Song, H., Chen, D. L., Ismagilov, R. F. Reactions in droplets in microflulidic channels. Angew. Chem., Int. Ed. 45 (44), 7336-7356 (2006).
- Lombardi, D., Dittrich, P. S. Droplet microfluidics with magnetic beads: a new tool to investigate drug-protein interactions. Anal. Bioanal. Chem. 399 (1), 347-352 (2011).
- Edgar, J. S., et al. Compartmentalization of chemically separated components into droplets. Angew. Chem., Int. Ed. 48 (15), 2719-2722 (2009).
- Edgar, J. S., et al. Capillary electrophoresis separation in the presence of an immiscible boundary for droplet analysis. Anal. Chem. 78 (19), 6948-6954 (2006).
- Baret, J. C., et al. Fluorescence-activated droplet sorting (FADS): efficient microfluidic cell sorting based on enzymatic activity. Lab Chip. 9 (13), 1850-1858 (2009).
- Agresti, J. J., et al. Ultrahigh-throughput screening in drop-based microfluidics for directed evolution. Proc. Natl. Acad. Sci. U. S. A. 107 (9), 4004-4009 (2010).
Citazione di questo articolo
Verboket, P. E., Borovinskaya, O., Meyer, N., Günther, D., Dittrich, P. S. A Microfluidic Chip for ICPMS Sample Introduction. J. Vis. Exp. (97), e52525, doi:10.3791/52525 (2015).