1
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Rupp BT, Cook CD, Purcell EA, Pop M, Radomski AE, Mesyngier N, Bailey RC, Nagrath S. CellMag-CARWash: A High Throughput Droplet Microfluidic Device for Live Cell Isolation and Single Cell Applications. Adv Biol (Weinh) 2024; 8:e2400066. [PMID: 38741244 DOI: 10.1002/adbi.202400066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Indexed: 05/16/2024]
Abstract
The recent push toward understanding an individual cell's behavior and identifying cellular heterogeneity has created an unmet need for technologies that can probe live cells at the single-cell level. Cells within a population are known to exhibit heterogeneous responses to environmental cues. These differences can lead to varied cellular states, behavior, and responses to therapeutics. Techniques are needed that are not only capable of processing and analyzing cellular populations at the single cell level, but also have the ability to isolate specific cell populations from a complex sample at high throughputs. The new CellMag-Coalesce-Attract-Resegment Wash (CellMag-CARWash) system combines positive magnetic selection with droplet microfluidic devices to isolate cells of interest from a mixture with >93% purity and incorporate treatments within individual droplets to observe single cell biological responses. This workflow is shown to be capable of probing the single cell extracellular vesicle (EV) secretion of MCF7 GFP cells. This article reports the first measurement of β-Estradiol's effect on EV secretion from MCF7 cells at the single cell level. Single cell processing revealed that MCF7 GFP cells possess a heterogeneous response to β-Estradiol stimulation with a 1.8-fold increase relative to the control.
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Affiliation(s)
- Brittany T Rupp
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Claire D Cook
- Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Emma A Purcell
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Matei Pop
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, 48109, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Abigail E Radomski
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Nicolas Mesyngier
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Ryan C Bailey
- Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Sunitha Nagrath
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, 48109, USA
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, 48109, USA
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2
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Krishnamurthy A, Anand RK. Electrokinetic Desalting and Salting of Water-in-Oil Droplets. Anal Chem 2024; 96:9876-9884. [PMID: 38842795 DOI: 10.1021/acs.analchem.4c00534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2024]
Abstract
Droplet-based microfluidic platforms demand modifications to the droplet composition to facilitate reactions and analyses. However, limited techniques exist to modify the droplet contents post their generation. Here, ion transport across two ion-exchange membranes possessing distinct selectivity is employed to introduce ions into (salt) or extract ions from (desalt) water-in-oil droplets. The ion concentration distribution and transport mechanisms are visualized using a precipitation reaction and a charged fluorescent tracer. Furthermore, current measurements reveal characteristic regimes in desalting and salting modes and demonstrate that the rates of ion transport linearly correlate with applied voltage and the ionic strength of the droplets. Importantly, up to 98% desalting efficiency is achieved. This technique advances droplet-based sample preparation through the straightforward manipulation of droplet contents.
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Affiliation(s)
- Aparna Krishnamurthy
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, 2415 Osborn Drive, Ames, Iowa 50011, United States
| | - Robbyn K Anand
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, 2415 Osborn Drive, Ames, Iowa 50011, United States
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3
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Ahmadi F, Tran H, Letourneau N, Little SR, Fortin A, Moraitis AN, Shih SCC. An Automated Single-Cell Droplet-Digital Microfluidic Platform for Monoclonal Antibody Discovery. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2308950. [PMID: 38441226 DOI: 10.1002/smll.202308950] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 01/30/2024] [Indexed: 06/27/2024]
Abstract
Monoclonal antibody (mAb) discovery plays a prominent role in diagnostic and therapeutic applications. Droplet microfluidics has become a standard technology for high-throughput screening of antibody-producing cells due to high droplet single-cell confinement frequency and rapid analysis and sorting of the cells of interest with their secreted mAbs. In this work, a new method is described for on-demand co-encapsulation of cells that eliminates the difficulties associated with washing in between consecutive steps inside the droplets and enables the washing and addition of fresh media. The new platform identifies hybridoma cells that are expressing antibodies of interest using antibody-characterization assays to find the best-performing or rare-cell antibody candidates.
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Affiliation(s)
- Fatemeh Ahmadi
- Department of Electrical and Computer Engineering, Concordia University, 1455 de Maisonneuve Blvd. West, Montréal, Québec, H3G 1M8, Canada
- Centre for Applied Synthetic Biology, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, H4B 1R6, Canada
| | - Hao Tran
- Department of Electrical and Computer Engineering, Concordia University, 1455 de Maisonneuve Blvd. West, Montréal, Québec, H3G 1M8, Canada
| | - Natasha Letourneau
- Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, H4B 1R6, Canada
| | - Samuel R Little
- Department of Electrical and Computer Engineering, Concordia University, 1455 de Maisonneuve Blvd. West, Montréal, Québec, H3G 1M8, Canada
- Centre for Applied Synthetic Biology, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, H4B 1R6, Canada
| | - Annie Fortin
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, H4P 2R2, Canada
| | - Anna N Moraitis
- Human Health Therapeutics Research Centre, National Research Council Canada, Montréal, Québec, H4P 2R2, Canada
| | - Steve C C Shih
- Department of Electrical and Computer Engineering, Concordia University, 1455 de Maisonneuve Blvd. West, Montréal, Québec, H3G 1M8, Canada
- Centre for Applied Synthetic Biology, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, H4B 1R6, Canada
- Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, H4B 1R6, Canada
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4
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Siedlik MJ, Issadore D. Pico-washing: simultaneous liquid addition and removal for continuous-flow washing of microdroplets. MICROSYSTEMS & NANOENGINEERING 2022; 8:46. [PMID: 35498338 PMCID: PMC9050730 DOI: 10.1038/s41378-022-00381-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 02/02/2022] [Accepted: 03/07/2022] [Indexed: 05/19/2023]
Abstract
Droplet microfluidics is based on a toolbox of several established unit operations, including droplet generation, incubation, mixing, pico-injection, and sorting. In the last two decades, the development of droplet microfluidic systems, which incorporate these multiple unit operations into a workflow, has demonstrated unique capabilities in fields ranging from single-cell transcriptomic analyses to materials optimization. One unit operation that is sorely underdeveloped in droplet microfluidics is washing, exchange of the fluid in a droplet with a different fluid. Here, we demonstrate what we name the "pico-washer," a unit operation capable of simultaneously adding fluid to and removing fluid from droplets in flow while requiring only a small footprint on a microfluidic chip. We describe the fabrication strategy, device architecture, and process parameters required for stable operation of this technology, which is capable of operating with kHz droplet throughput. Furthermore, we provide an image processing workflow to characterize the washing process with microsecond and micrometer resolution. Finally, we demonstrate the potential for integrated droplet workflows by arranging two of these unit operations in series with a droplet generator, describe a design rule for stable operation of the pico-washer when integrated into a system, and validate this design rule experimentally. We anticipate that this technology will contribute to continued development of the droplet microfluidics toolbox and the realization of novel droplet-based, multistep biological and chemical assays.
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Affiliation(s)
- Michael J. Siedlik
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104 United States
| | - David Issadore
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104 United States
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA 19104 United States
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5
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Shi X, Tan W, Lu Y, Cao W, Zhu G. A needle tip CCEA microfluidic device based on enhanced Dean flow for cell washing. MICROSYSTEMS & NANOENGINEERING 2021; 7:81. [PMID: 34721889 PMCID: PMC8519928 DOI: 10.1038/s41378-021-00311-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 09/01/2021] [Accepted: 09/03/2021] [Indexed: 06/13/2023]
Abstract
Particle/cell washing is an essential technique in biological and clinical manipulations. Herein, we propose a novel circular contraction-expansion array (CCEA) microdevice. It can be directly connected to a needle tip without connection tubes. Its small size and centrosymmetric structure are beneficial to low sample consumption, high connection stability, and a wide application range. Computational fluid dynamics (CFD) simulation results show that the CCEA structure can produce a stronger Dean flow and lead to faster particle/cell focusing than the circle structure and CEA structure with the same length. Experimentally, an optimal flow rate ratio of 1:3 and an optimal total flow rate of 120 μL/min were found to ensure a stable fluid distribution. Under these conditions, rapid focusing of 10-20 μm particles with high efficiencies was achieved. Compared with a normal CEA device using tubes, the particle loss rate could be reduced from 64 to 7% when washing 500 μL of a rare sample. Cell suspensions with concentrations from 3 × 105/mL to 1 × 103/mL were tested. The high cell collection efficiency (>85% for three cell lines) and stable waste removal efficiency (>80%) reflected the universality of the CCEA microfluidic device. After the washing, the cell activities of H1299 cells and MCF-7 cells were calculated to be 93.8 and 97.5%, respectively. This needle-tip CCEA microfluidic device showed potential in basic medical research and clinical diagnosis.
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Affiliation(s)
- Xin Shi
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300350 China
| | - Wei Tan
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300350 China
| | - Yuwen Lu
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300350 China
| | - Wenfeng Cao
- Tianjin Tumor Hospital, Tianjin Medical University, Tianjin, 300070 China
| | - Guorui Zhu
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300350 China
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6
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Shi N, Mohibullah M, Easley CJ. Active Flow Control and Dynamic Analysis in Droplet Microfluidics. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2021; 14:133-153. [PMID: 33979546 PMCID: PMC8956363 DOI: 10.1146/annurev-anchem-122120-042627] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Droplet-based microfluidics has emerged as an important subfield within the microfluidic and general analytical communities. Indeed, several unique applications such as digital assay readout and single-cell sequencing now have commercial systems based on droplet microfluidics. Yet there remains room for this research area to grow. To date, most analytical readouts are optical in nature, relatively few studies have integrated sample preparation, and passive means for droplet formation and manipulation have dominated the field. Analytical scientists continue to expand capabilities by developing droplet-compatible method adaptations, for example, by interfacing to mass spectrometers or automating droplet sampling for temporally resolved analysis. In this review, we highlight recently developed fluidic control techniques and unique integrations of analytical methodology with droplet microfluidics-focusing on automation and the connections to analog/digital domains-and we conclude by offering a perspective on current challenges and future applications.
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Affiliation(s)
- Nan Shi
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, USA;
| | - Md Mohibullah
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, USA;
| | - Christopher J Easley
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, USA;
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7
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Wetzler-Quevedo SP, Meyerhoff ME, Bailey RC. Characterization of the impact of mixing and droplet volumes on the behavior of microfluidic ion-selective droptodes. Analyst 2021; 146:5095-5101. [PMID: 34259243 DOI: 10.1039/d1an00733e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Droplet microfluidic optodes, or "droptodes", have emerged as a powerful technology for rapid detection of small ions in complex matrices. While using segmented aqueous phases provides the benefits of sample isolation, the influence of the liquid nature of the oil carrier phase has not yet been explored. In this paper, we examine the influence of microfluidic parameters on droptode efficiency, using potassium-sensitive droptodes as a model system. We found that while changing flow rates on device does not change droptode performance, both channel geometry and droplet size significantly impact droptode efficiency. Specifically, enhanced mixing of the droplets leads to faster equilibration on device and lowers limits of detection by about one order of magnitude. We also found that increasing the size of the sample droplet, at the expense of the size of the oil carrier/sensing phase, leads to higher sensitivity in the linear region of the droptode. These easily manipulated properties will allow one device to potentially be adapted for several different applications, based upon the type and concentration range of measurement required.
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8
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Payne EM, Holland-Moritz DA, Sun S, Kennedy RT. High-throughput screening by droplet microfluidics: perspective into key challenges and future prospects. LAB ON A CHIP 2020; 20:2247-2262. [PMID: 32500896 DOI: 10.1039/d0lc00347f] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
In two decades of development, impressive strides have been made for automating basic laboratory operations in droplet-based microfluidics, allowing the emergence of a new form of high-throughput screening and experimentation in nanoliter to femtoliter volumes. Despite advancements in droplet storage, manipulation, and analysis, the field has not yet been widely adapted for many high-throughput screening (HTS) applications. Broad adoption and commercial development of these techniques require robust implementation of strategies for the stable storage, chemical containment, generation of libraries, sample tracking, and chemical analysis of these small samples. We discuss these challenges for implementing droplet HTS and highlight key strategies that have begun to address these concerns. Recent advances in the field leave us optimistic about the future prospects of this rapidly developing technology.
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Affiliation(s)
- Emory M Payne
- Department of Chemistry, University of Michigan, Ann Arbor, MI, USA.
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9
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Programmable µChopper Device with On-Chip Droplet Mergers for Continuous Assay Calibration. MICROMACHINES 2020; 11:mi11060620. [PMID: 32630555 PMCID: PMC7344876 DOI: 10.3390/mi11060620] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 06/18/2020] [Accepted: 06/22/2020] [Indexed: 12/21/2022]
Abstract
While droplet-based microfluidics is a powerful technique with transformative applications, most devices are passively operated and thus have limited real-time control over droplet contents. In this report, an automated droplet-based microfluidic device with pneumatic pumps and salt water electrodes was developed to generate and coalesce up to six aqueous-in-oil droplets (2.77 nL each). Custom control software combined six droplets drawn from any of four inlet reservoirs. Using our μChopper method for lock-in fluorescence detection, we first accomplished continuous linear calibration and quantified an unknown sample. Analyte-independent signal drifts and even an abrupt decrease in excitation light intensity were corrected in real-time. The system was then validated with homogeneous insulin immunoassays that showed a nonlinear response. On-chip droplet merging with antibody-oligonucleotide (Ab-oligo) probes, insulin standards, and buffer permitted the real-time calibration and correction of large signal drifts. Full calibrations (LODconc = 2 ng mL−1 = 300 pM; LODamt = 5 amol) required <1 min with merely 13.85 nL of Ab-oligo reagents, giving cost-savings 160-fold over the standard well-plate format while also automating the workflow. This proof-of-concept device—effectively a microfluidic digital-to-analog converter—is readily scalable to more droplets, and it is well-suited for the real-time automation of bioassays that call for expensive reagents.
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10
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Wuethrich A, Rajkumar AR, Shanmugasundaram KB, Reza KK, Dey S, Howard CB, Sina AAI, Trau M. Single droplet detection of immune checkpoints on a multiplexed electrohydrodynamic biosensor. Analyst 2019; 144:6914-6921. [PMID: 31657376 DOI: 10.1039/c9an01450k] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Monitoring soluble immune checkpoints in circulating fluids has the potential for minimally-invasive diagnostics and personalised therapy in precision medicine. Yet, the sensitive detection of multiple immune checkpoints from small volumes of liquid biopsy samples is challenging. In this study, we develop a multiplexed immune checkpoint biosensor (MICB) for parallel detection of soluble immune checkpoints PD-1, PD-L1, and LAG-3. MICB integrates a microfluidic sandwich immunoassay using engineered single chain variable fragments and alternating current electrohydrodynamic in situ nanofluidic mixing for promoting biosensor-target interaction and reducing non-specific non-target binding. MICB provides advantages of simultaneous analysis of up to 28 samples in <2 h, requires as little as a single sample drop (i.e., 20 μL) per target immune checkpoint, and applies high-affinity yeast cell-derived single chain variable fragments as a cost-effective alternative to monoclonal antibodies. We investigate the assay performance of MICB and demonstrate its capability for accurate immune checkpoint detection in simulated patient serum samples at clinically-relevant levels. MICB provides a dynamic range of 5 to 200 pg mL-1 for PD-1 and PD-L1, and 50 to 1000 pg mL-1 for LAG-3 with a coefficient of variation <13.8%. Sensitive immune checkpoint detection was achieved with limits of detection values of 5 pg mL-1 for PD-1, 5 pg mL-1 for PD-L1, and 50 pg mL-1 for LAG-3. The multiplexing capability, sensitivity, and relative assay simplicity of MICB make it capable of serving as a bioanalytical tool for immune checkpoint therapy monitoring.
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Affiliation(s)
- Alain Wuethrich
- Centre for Personalized Nanomedicine, Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, Brisbane, QLD 4072, Australia.
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11
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Liu Z, Fornell A, Barbe L, Hjort K, Tenje M. On-chip background dilution in droplets with high particle recovery using acoustophoresis. BIOMICROFLUIDICS 2019; 13:064123. [PMID: 31832121 PMCID: PMC6897560 DOI: 10.1063/1.5129256] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 11/19/2019] [Indexed: 05/02/2023]
Abstract
Droplet microfluidics has shown great potential for on-chip biological and chemical assays. However, fluid exchange in droplet microfluidics with high particle recovery is still a major bottleneck. Here, using acoustophoresis, we present for the first time a label-free method to achieve continuous background dilution in droplets containing cells with high sample recovery. The system comprises droplet generation, acoustic focusing, droplet splitting, picoinjection, and serpentine mixing on the same chip. The capacities of the picoinjection and the droplet split to dilute the background fluorescent signal in the droplets have been characterized. The sample recovery at different droplet split ratios has also been characterized. The results show a maximum of 4.3-fold background dilution with 87.7% particle recovery. We also demonstrated that the system can be used to dilute background fluorescent signal in droplets containing either polystyrene particles or endothelial cells.
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Affiliation(s)
| | | | | | - Klas Hjort
- Department of Engineering Sciences, Uppsala University, 75271 Uppsala, Sweden
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12
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Zhukov DV, Khorosheva EM, Khazaei T, Du W, Selck DA, Shishkin AA, Ismagilov RF. Microfluidic SlipChip device for multistep multiplexed biochemistry on a nanoliter scale. LAB ON A CHIP 2019; 19:3200-3211. [PMID: 31441477 DOI: 10.1039/c9lc00541b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We have developed a multistep microfluidic device that expands the current SlipChip capabilities by enabling multiple steps of droplet merging and multiplexing. Harnessing the interfacial energy between carrier and sample phases, this manually operated device accurately meters nanoliter volumes of reagents and transfers them into on-device reaction wells. Judiciously shaped microfeatures and surface-energy traps merge droplets in a parallel fashion. Wells can be tuned for different volumetric capacities and reagent types, including for pre-spotted reagents that allow for unique identification of original well contents even after their contents are pooled. We demonstrate the functionality of the multistep SlipChip by performing RNA transcript barcoding on-device for synthetic spiked-in standards and for biologically derived samples. This technology is a good candidate for a wide range of biological applications that require multiplexing of multistep reactions in nanoliter volumes, including single-cell analyses.
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Affiliation(s)
- Dmitriy V Zhukov
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA.
| | - Eugenia M Khorosheva
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA.
| | - Tahmineh Khazaei
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA
| | - Wenbin Du
- Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, USA
| | - David A Selck
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA.
| | - Alexander A Shishkin
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA
| | - Rustem F Ismagilov
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA. and Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA
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