1
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Kauffmann PJ, Walker NL, Gupta V, Dick JE. Triple-Barrel Ultramicroelectrodes for Multipurpose, Submilliliter Electroanalysis. Anal Chem 2023; 95:8411-8416. [PMID: 37218147 PMCID: PMC10911394 DOI: 10.1021/acs.analchem.3c00735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Here, we have developed and applied a triple-barrel microelectrode. This device incorporates a platinum disk working electrode, a platinum disk counter electrode, and a low-leakage Ag/AgCl reference electrode into a small probe. We demonstrate that the incorporated low-leakage reference electrode shows similar voltammetry, potentiometry, and drift when compared to a commercial reference electrode in bulk solution. We also demonstrate the versatility of such a small three-channel system via voltammetry in nanoliter droplets and through electroanalysis of captured aerosols. Finally, we demonstrate the probe's potential utility in single-cell electroanalysis by making measurements within salmon eggs.
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Affiliation(s)
- Philip J Kauffmann
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Nicole L Walker
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Vanshika Gupta
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Jeffrey E Dick
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
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2
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Wang X, Wang Z, Yu C, Ge Z, Yang W. Advances in precise single-cell capture for analysis and biological applications. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2022; 14:3047-3063. [PMID: 35946358 DOI: 10.1039/d2ay00625a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Cells are the basic structural and functional units of living organisms. However, conventional cell analysis only averages millions of cell populations, and some important information is lost. It is essential to quantitatively characterize the physiology and pathology of single-cell activities. Precise single-cell capture is an extremely challenging task during cell sample preparation. In this review, we summarize the category of technologies to capture single cells precisely with a focus on the latest development in the last five years. Each technology has its own set of benefits and specific challenges, which provide opportunities for researchers in different fields. Accordingly, we introduce the applications of captured single cells in cancer diagnosis, analysis of metabolism and secretion, and disease treatment. Finally, some perspectives are provided on the current development trends, future research directions, and challenges of single-cell capture.
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Affiliation(s)
- Xiaowen Wang
- School of Electromechanical and Automotive Engineering, Yantai University, Yantai 264005, China.
| | - Zhen Wang
- School of Electromechanical and Automotive Engineering, Yantai University, Yantai 264005, China.
| | - Chang Yu
- College of Computer Science, Chongqing University, Chongqing 400000, China
| | - Zhixing Ge
- State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016, China.
| | - Wenguang Yang
- School of Electromechanical and Automotive Engineering, Yantai University, Yantai 264005, China.
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3
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Gallion LA, Wang Y, Massaro A, Yao M, Petersen BV, Zhang Q, Huang W, Carr AJ, Zhang Q, Allbritton NL. "Fix and Click" for Assay of Sphingolipid Signaling in Single Primary Human Intestinal Epithelial Cells. Anal Chem 2022; 94:1594-1600. [PMID: 35020354 PMCID: PMC8931668 DOI: 10.1021/acs.analchem.1c03503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Capillary electrophoresis with fluorescence detection (CE-F) is a powerful method to measure enzyme activation in single cells. However, cellular enzymatic assays used in CE-F routinely utilize reporter substrates that possess a bulky fluorophore that may impact enzyme kinetics. To address these challenges, we describe a "fix and click" method utilizing an alkyne-terminated enzyme activation reporter, aldehyde-based fixation, and a click chemistry reaction to attach a fluorophore prior to analysis by single-cell CE-F. The "fix and click" strategy was utilized to investigate sphingolipid signaling in both immortalized cell lines and primary human colonic epithelial cells. When the sphingosine alkyne reporter was loaded into cells, this reporter was metabolized to ceramide (31.6 ± 3.3% peak area) without the production of sphingosine-1-phosphate. In contrast, when the reporter sphingosine fluorescein was introduced into cells, sphingosine fluorescein was converted to sphingosine-1-phosphate and downstream products (32.8 ± 5.7% peak area) without the formation of ceramide. Sphingolipid metabolism was measured in single cells from both differentiated and stem/proliferative human colonic epithelium using "fix and click" paired with CE-F to highlight the diversity of sphingosine metabolism in single cells from primary human colonic epithelium. This novel method will find widespread utility for the performance of single-cell enzyme assays by virtue of its ability to temporally and spatially separate cellular reactions with alkyne-terminated reporters, followed by the assay of enzyme activation at a later time and place.
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Affiliation(s)
- Luke A. Gallion
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina, 27514, United States of America,Department of Bioengineering, University of Washington, Seattle, Washington, 98105, United States of America
| | - Yuli Wang
- Department of Bioengineering, University of Washington, Seattle, Washington, 98105, United States of America
| | - Angelo Massaro
- Department of Bioengineering, University of Washington, Seattle, Washington, 98105, United States of America
| | - Ming Yao
- Department of Bioengineering, University of Washington, Seattle, Washington, 98105, United States of America
| | - Brae V. Petersen
- Department of Bioengineering, University of Washington, Seattle, Washington, 98105, United States of America
| | - Quanzheng Zhang
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, Chapel Hill, North Carolina, 27514, United States of America
| | - Weigang Huang
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, Chapel Hill, North Carolina, 27514, United States of America
| | - Adam J. Carr
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, Chapel Hill, North Carolina, 27514, United States of America
| | - Qisheng Zhang
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, Chapel Hill, North Carolina, 27514, United States of America
| | - Nancy L. Allbritton
- Department of Bioengineering, University of Washington, Seattle, Washington, 98105, United States of America,Correspondence: Nancy L. Allbritton, Department of Bioengineering, University of Washington, Seattle, Washington, 98105, United States of America;
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4
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Gopal A, Herr AE. Segmentation-based analysis of single-cell immunoblots. Electrophoresis 2021; 42:2070-2080. [PMID: 34357587 PMCID: PMC8526408 DOI: 10.1002/elps.202100144] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Revised: 07/06/2021] [Accepted: 07/27/2021] [Indexed: 11/11/2022]
Abstract
From genomics to transcriptomics to proteomics, microfluidic tools underpin recent advances in single-cell biology. Detection of specific proteoforms-with single-cell resolution-presents challenges in detection specificity and sensitivity. Miniaturization of protein immunoblots to single-cell resolution mitigates these challenges. For example, in microfluidic western blotting, protein targets are separated by electrophoresis and subsequently detected using fluorescently labeled antibody probes. To quantify the expression level of each protein target, the fluorescent protein bands are fit to Gaussians; yet, this method is difficult to use with noisy, low-abundance, or low-SNR protein bands, and with significant band skew or dispersion. In this study, we investigate segmentation-based approaches to robustly quantify protein bands from single-cell protein immunoblots. As compared to a Gaussian fitting pipeline, the segmentation pipeline detects >1.5× more protein bands for downstream quantification as well as more of the low-abundance protein bands (i.e., with SNR ∼3). Utilizing deep learning-based segmentation approaches increases the recovery of low-SNR protein bands by an additional 50%. However, we find that segmentation-based approaches are less robust at quantifying poorly resolved protein bands (separation resolution, Rs < 0.6). With burgeoning needs for more single-cell protein analysis tools, we see microfluidic separations as benefitting substantially from segmentation-based analysis approaches.
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Affiliation(s)
- Anjali Gopal
- Department of Bioengineering, University of California, Berkeley, CA, USA
- UC Berkeley/UCSF Graduate Program in Bioengineering, University of California, Berkeley, CA, USA
| | - Amy E. Herr
- Department of Bioengineering, University of California, Berkeley, CA, USA
- UC Berkeley/UCSF Graduate Program in Bioengineering, University of California, Berkeley, CA, USA
- Chan Zuckerberg BioHub, San Francisco, CA, USA
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5
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Kumar R, Guttman A, Rathore AS. Applications of capillary electrophoresis for biopharmaceutical product characterization. Electrophoresis 2021; 43:143-166. [PMID: 34591322 DOI: 10.1002/elps.202100182] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 09/07/2021] [Accepted: 09/23/2021] [Indexed: 12/16/2022]
Abstract
Capillary electrophoresis (CE), after being introduced several decades ago, has carved out a niche for itself in the field of analytical characterization of biopharmaceutical products. It does not only offer fast separation, high resolution in miniaturized format, but equally importantly represents an orthogonal separation mechanism to high-performance liquid chromatography. Therefore, it is not surprising that CE-based methods can be found in all major pharmacopoeias and are recommended for the analysis of biopharmaceutical products during process development, characterization, quality control, and release testing. Different separation formats of CE, such as capillary gel electrophoresis, capillary isoelectric focusing, and capillary zone electrophoresis are widely used for size and charge heterogeneity characterization as well as purity and stability testing of therapeutic proteins. Hyphenation of CE with MS is emerging as a promising bioanalytical tool to assess the primary structure of therapeutic proteins along with any impurities. In this review, we confer the latest developments in capillary electrophoresis, used for the characterization of critical quality attributes of biopharmaceutical products covering the past 6 years (2015-2021). Monoclonal antibodies, due to their significant share in the market, have been given prioritized coverage.
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Affiliation(s)
- Ramesh Kumar
- Department of Chemical Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India
| | - Andras Guttman
- Horváth Csaba Memorial Laboratories of Bioseparation Sciences, Research Center for Molecular Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,Translational Glycomics Group, Research Institute of Biomolecular and Chemical Engineering, University of Pannonia, Veszprem, Hungary
| | - Anurag S Rathore
- Department of Chemical Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India
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6
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Vlassakis J, Hansen LL, Higuchi-Sanabria R, Zhou Y, Tsui CK, Dillin A, Huang H, Herr AE. Measuring expression heterogeneity of single-cell cytoskeletal protein complexes. Nat Commun 2021; 12:4969. [PMID: 34404787 PMCID: PMC8371148 DOI: 10.1038/s41467-021-25212-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 07/23/2021] [Indexed: 02/07/2023] Open
Abstract
Multimeric cytoskeletal protein complexes orchestrate normal cellular function. However, protein-complex distributions in stressed, heterogeneous cell populations remain unknown. Cell staining and proximity-based methods have limited selectivity and/or sensitivity for endogenous multimeric protein-complex quantification from single cells. We introduce micro-arrayed, differential detergent fractionation to simultaneously detect protein complexes in hundreds of individual cells. Fractionation occurs by 60 s size-exclusion electrophoresis with protein complex-stabilizing buffer that minimizes depolymerization. Proteins are measured with a ~5-hour immunoassay. Co-detection of cytoskeletal protein complexes in U2OS cells treated with filamentous actin (F-actin) destabilizing Latrunculin A detects a unique subpopulation (~2%) exhibiting downregulated F-actin, but upregulated microtubules. Thus, some cells may upregulate other cytoskeletal complexes to counteract the stress of Latrunculin A treatment. We also sought to understand the effect of non-chemical stress on cellular heterogeneity of F-actin. We find heat shock may dysregulate filamentous and globular actin correlation. In this work, our assay overcomes selectivity limitations to biochemically quantify single-cell protein complexes perturbed with diverse stimuli.
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Affiliation(s)
- Julea Vlassakis
- Department of Bioengineering, University of California Berkeley, Berkeley, CA, USA
| | - Louise L Hansen
- Department of Bioengineering, University of California Berkeley, Berkeley, CA, USA
| | - Ryo Higuchi-Sanabria
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, USA
| | - Yun Zhou
- Division of Biostatistics, University of California Berkeley, Berkeley, CA, USA
| | - C Kimberly Tsui
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, USA
| | - Andrew Dillin
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, USA
- Howard Hughes Medical Institute, University of California Berkeley, Berkeley, CA, USA
| | - Haiyan Huang
- Department of Statistics, University of California Berkeley, Berkeley, CA, USA
- Center for Computational Biology, University of California Berkeley, Berkeley, CA, USA
| | - Amy E Herr
- Department of Bioengineering, University of California Berkeley, Berkeley, CA, USA.
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7
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Cho SY, Gong X, Koman VB, Kuehne M, Moon SJ, Son M, Lew TTS, Gordiichuk P, Jin X, Sikes HD, Strano MS. Cellular lensing and near infrared fluorescent nanosensor arrays to enable chemical efflux cytometry. Nat Commun 2021; 12:3079. [PMID: 34035262 PMCID: PMC8149711 DOI: 10.1038/s41467-021-23416-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 04/20/2021] [Indexed: 02/07/2023] Open
Abstract
Nanosensors have proven to be powerful tools to monitor single cells, achieving spatiotemporal precision even at molecular level. However, there has not been way of extending this approach to statistically relevant numbers of living cells. Herein, we design and fabricate nanosensor array in microfluidics that addresses this limitation, creating a Nanosensor Chemical Cytometry (NCC). nIR fluorescent carbon nanotube array is integrated along microfluidic channel through which flowing cells is guided. We can utilize the flowing cell itself as highly informative Gaussian lenses projecting nIR profiles and extract rich information. This unique biophotonic waveguide allows for quantified cross-correlation of biomolecular information with various physical properties and creates label-free chemical cytometer for cellular heterogeneity measurement. As an example, the NCC can profile the immune heterogeneities of human monocyte populations at attomolar sensitivity in completely non-destructive and real-time manner with rate of ~600 cells/hr, highest range demonstrated to date for state-of-the-art chemical cytometry.
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Affiliation(s)
- Soo-Yeon Cho
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Xun Gong
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Volodymyr B Koman
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Matthias Kuehne
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Sun Jin Moon
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Manki Son
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Tedrick Thomas Salim Lew
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Pavlo Gordiichuk
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Xiaojia Jin
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Hadley D Sikes
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Michael S Strano
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
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8
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Gao T, Gao X, Xu C, Wang M, Chen M, Wang J, Ma F, Yu P, Mao L. Label-Free Resistance Cytometry at the Orifice of a Nanopipette. Anal Chem 2021; 93:2942-2949. [PMID: 33502179 DOI: 10.1021/acs.analchem.0c04585] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Development of new principles and techniques at the single-cell level is significantly important since cells as basic units of living organisms always bear large heterogeneity. Herein, we demonstrate a new electrochemical principle for single-cell analysis based on an ion current blockage at the orifice of a nanopipette, defined as resistance cytometry. The amplitude and the frequency of ion current transients show strong dependence on the size and the concentration of cells, which could be used for in situ cell sizing and counting. This technique shows good ability to detect the size change of RBCs under stimulations of different pH and osmotic pressure values. More importantly, the as-presented resistance cytometry can distinguish lymphoma blood cells from normal blood cells for patient blood samples. The as-presented resistance cytometry is label-free, non-invasive, and non-destructive, which not only opens new opportunities for single-cell analysis but also provides a new platform for cell-related medical diagnostic technologies.
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Affiliation(s)
- Tienan Gao
- Research Center for Analytical Sciences, Department of Chemistry, College of Sciences, Northeastern University, Box 332, Shenyang 110819, China.,Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiangyi Gao
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Cong Xu
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Menglin Wang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing 100191, China
| | - Mingli Chen
- Research Center for Analytical Sciences, Department of Chemistry, College of Sciences, Northeastern University, Box 332, Shenyang 110819, China
| | - Jianhua Wang
- Research Center for Analytical Sciences, Department of Chemistry, College of Sciences, Northeastern University, Box 332, Shenyang 110819, China
| | - Furong Ma
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing 100191, China
| | - Ping Yu
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lanqun Mao
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,College of Chemistry, Beijing Normal University, Beijing 100875, China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
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9
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Grist SM, Mourdoukoutas AP, Herr AE. 3D projection electrophoresis for single-cell immunoblotting. Nat Commun 2020; 11:6237. [PMID: 33277486 PMCID: PMC7718224 DOI: 10.1038/s41467-020-19738-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 10/20/2020] [Indexed: 12/21/2022] Open
Abstract
Immunoassays and mass spectrometry are powerful single-cell protein analysis tools; however, interfacing and throughput bottlenecks remain. Here, we introduce three-dimensional single-cell immunoblots to detect both cytosolic and nuclear proteins. The 3D microfluidic device is a photoactive polyacrylamide gel with a microwell array-patterned face (xy) for cell isolation and lysis. Single-cell lysate in each microwell is “electrophoretically projected” into the 3rd dimension (z-axis), separated by size, and photo-captured in the gel for immunoprobing and confocal/light-sheet imaging. Design and analysis are informed by the physics of 3D diffusion. Electrophoresis throughput is > 2.5 cells/s (70× faster than published serial sampling), with 25 immunoblots/mm2 device area (>10× increase over previous immunoblots). The 3D microdevice design synchronizes analyses of hundreds of cells, compared to status quo serial analyses that impart hours-long delay between the first and last cells. Here, we introduce projection electrophoresis to augment the heavily genomic and transcriptomic single-cell atlases with protein-level profiling. Single-cell immunoblotting previously separated proteins on a polyacrylamide slab in the xy direction and was limited by throughput and sample consumption. Here the authors adapt the system to separate proteins in the z direction, allowing for closer spacing of sample wells and improved sample consumption.
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Affiliation(s)
- Samantha M Grist
- Department of Bioengineering, University of California, Berkeley, USA
| | - Andoni P Mourdoukoutas
- Department of Bioengineering, University of California, Berkeley, USA.,UC Berkeley - UCSF Graduate Program in Bioengineering, Berkeley, USA
| | - Amy E Herr
- Department of Bioengineering, University of California, Berkeley, USA. .,UC Berkeley - UCSF Graduate Program in Bioengineering, Berkeley, USA. .,Chan Zuckerberg Biohub, San Francisco, CA, USA.
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10
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McCormick HK, Dick JE. Nanoelectrochemical quantification of single-cell metabolism. Anal Bioanal Chem 2020; 413:17-24. [PMID: 32915282 DOI: 10.1007/s00216-020-02899-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 08/10/2020] [Accepted: 08/18/2020] [Indexed: 12/12/2022]
Abstract
At the most fundamental level, the behavior of tissue is governed by the activity of its single cells. A detailed examination of single-cell biology is necessary in order to gain a deeper understanding of disease progression. While single-cell genomics and transcriptomics are mature due to robust amplification strategies, the metabolome is difficult to quantify. Nanoelectrochemical techniques stand poised to quantify single-cell metabolism as a result of the fabrication of nanoelectrodes, which allow one to make intracellular electrochemical measurements. This article is concerned with intracellular nanoelectrochemistry, focusing on the sensitive and selective quantification of various metabolites within a single, living cell. We will review the strong literature behind this field, discuss the potential deleterious effects of passing charge inside cells, and provide future outlooks for this promising avenue of inquiry. We also present a mathematical relationship based on Faraday's Law and bulk electrolysis theory to examine the consumption of analyte within a cell due to passing charge at the nanotip.Graphical abstract.
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Affiliation(s)
- Hadley K McCormick
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Jeffrey E Dick
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA. .,Lineberger Comprehensive Cancer Center, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
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11
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Yao HW, Guo XF, Wang H. Simultaneous Quantitation of Intra- and Extracellular Nitric Oxide in Single Macrophage RAW 264.7 Cells by Capillary Electrophoresis with Laser-Induced Fluorescence Detection. Anal Chem 2020; 92:11904-11911. [DOI: 10.1021/acs.analchem.0c02283] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Hui-Wen Yao
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China
- School of Pharmacy, Hubei University of Chinese Medicine, Wuhan 430065, China
| | - Xiao-Feng Guo
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China
| | - Hong Wang
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China
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12
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Identification of intracellular cadmium transformation in HepG2 and MCF-7 cells. Talanta 2020; 218:121065. [PMID: 32797863 DOI: 10.1016/j.talanta.2020.121065] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Revised: 04/17/2020] [Accepted: 04/19/2020] [Indexed: 01/14/2023]
Abstract
It is of significance to elucidate or understand the intracellular transformation & migration behaviors of heavy metals in specific cells. Herein, we report the fast and efficient separation of cadmium-metallothioneins (Cd-MTs) and Cd2+in cell lysate by a short column capillary electrophoresis (SC-CE), followed by coupling with inductively coupled plasma mass spectrometry (ICP-MS) to facilitate the speciation of intracellular cadmium species. The incorporation of sodium dodecyl sulfate (SDS) in running buffer significantly reduces the peak width of Cd2+from 170 s to 26 s in the electrophoretogram, causing a 5.3-fold improvement on the sensitivity. Linear ranges of 0.5-50 mg L-1,0.056-5.6 mg L-1 and 0.1-10 mg L-1 are achieved for MTs, Cd-MTs (Cd) and Cd2+, respectively, along with detection limits of 0.013 mg L-1 for Cd-MTs (Cd) and 0.020 mg L-1 for Cd2+. The transformation of cadmium in HepG2 and MCF-7 cells is evaluated after their incubation with Cd2+ reinforced culture medium. Intracellular free Cd2+ cation and Cd-MTs are identified, along with Cd2+ transformation to Cd-glutathione (GSH) adduct/complex, as further demonstrated by ESI-MS.
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13
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Moully EH, Berns EJ, Mrksich M. Label-Free Assay of Protein Tyrosine Phosphatase Activity in Single Cells. Anal Chem 2019; 91:13206-13212. [PMID: 31536703 PMCID: PMC6889211 DOI: 10.1021/acs.analchem.9b03640] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Populations of cells exhibit variations in biochemical activity, resulting from many factors including random stochastic variability in protein production, metabolic and cell-cycle states, regulatory mechanisms, and external signaling. The development of methods for the analysis of single cells has allowed for the measurement and understanding of this inherent heterogeneity, yet methods for measuring protein activities on the single-cell scale lag behind their genetic analysis counterparts and typically report on expression rather than activity. This paper presents an approach to measure protein tyrosine phosphatase (PTP) activity in individual cells using self-assembled monolayers for matrix-assisted laser desorption/ionization mass spectrometry. Using flow cytometry, individual cells are first sorted into a well plate containing lysis buffer and a phosphopeptide substrate. After lysis and incubation-during which the PTP enzymes act on the peptide substrate-the reaction substrate and product are immobilized onto arrays of self-assembled monolayers, which are then analyzed using mass spectrometry. PTP activities from thousands of individual cells were measured and their distributions analyzed. This work demonstrates a general method for measuring enzyme activities in lysates derived from individual cells and will contribute to the understanding of cellular heterogeneity in a variety of contexts.
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Affiliation(s)
- Elamar Hakim Moully
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
| | - Eric J. Berns
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Milan Mrksich
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, USA
- Department of Cell & Developmental Biology, Northwestern University, Chicago, Illinois 60611, USA
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14
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Chen P, Chen D, Li S, Ou X, Liu BF. Microfluidics towards single cell resolution protein analysis. Trends Analyt Chem 2019. [DOI: 10.1016/j.trac.2019.06.022] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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15
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Abraham DH, Anttila MM, Gallion LA, Petersen BV, Proctor A, Allbritton NL. Design of an automated capillary electrophoresis platform for single-cell analysis. Methods Enzymol 2019; 628:191-221. [PMID: 31668230 DOI: 10.1016/bs.mie.2019.06.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Single-cell analysis of cellular contents by highly sensitive analytical instruments is known as chemical cytometry. A chemical cytometer typically samples one cell at a time, quantifies the cellular contents of interest, and then processes and reports that data. Automation adds the potential to perform this entire sequence of events with minimal intervention, increasing throughput and repeatability. In this chapter, we discuss the design considerations for an automated capillary electrophoresis-based instrument for assay of enzymatic activity within single cells. We describe the key requirements of the microscope base and capillary electrophoresis platforms. We also provide detailed protocols and schematic designs of our cell isolation, lysis, sampling, and detection strategies. Additionally, we describe our signal processing and instrument automation workflows. The described automated system has demonstrated single-cell throughput at rates above 100cells/h and analyte limits of detection as low as 10-20mol.
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Affiliation(s)
- David H Abraham
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States
| | - Matthew M Anttila
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States
| | - Luke A Gallion
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States
| | - Brae V Petersen
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States
| | - Angela Proctor
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States
| | - Nancy L Allbritton
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States; Joint Department of Biomedical Engineering, University of North Carolina, Chapel and North Carolina State University, Raleigh, NC, USA.
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16
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Neumann EK, Do TD, Comi TJ, Sweedler JV. Exploring the Fundamental Structures of Life: Non-Targeted, Chemical Analysis of Single Cells and Subcellular Structures. Angew Chem Int Ed Engl 2019; 58:9348-9364. [PMID: 30500998 PMCID: PMC6542728 DOI: 10.1002/anie.201811951] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Indexed: 01/14/2023]
Abstract
Cells are a basic functional and structural unit of living organisms. Both unicellular communities and multicellular species produce an astonishing chemical diversity, enabling a wide range of divergent functions, yet each cell shares numerous aspects that are common to all living organisms. While there are many approaches for studying this chemical diversity, only a few are non-targeted and capable of analyzing hundreds of different chemicals at cellular resolution. Here, we review the non-targeted approaches used to perform comprehensive chemical analyses, provide chemical imaging information, or obtain high-throughput single-cell profiling data. Single-cell measurement capabilities are rapidly increasing in terms of throughput, limits of detection, and completeness of the chemical analyses; these improvements enable their application to understand ever more complex physiological phenomena, such as learning, memory, and behavior.
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Affiliation(s)
- Elizabeth K. Neumann
- Department of Chemistry and the Beckman Institute for Advanced Science and Technology, 405 N. Mathews Avenue, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Thanh D. Do
- Department of Chemistry, 1420 Circle Drive, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Troy J. Comi
- Department of Chemistry and the Beckman Institute for Advanced Science and Technology, 405 N. Mathews Avenue, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Jonathan V. Sweedler
- Department of Chemistry and the Beckman Institute for Advanced Science and Technology, 405 N. Mathews Avenue, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
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17
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Yin L, Zhang Z, Liu Y, Gao Y, Gu J. Recent advances in single-cell analysis by mass spectrometry. Analyst 2019; 144:824-845. [PMID: 30334031 DOI: 10.1039/c8an01190g] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cells are the most basic structural units that play vital roles in the functioning of living organisms. Analysis of the chemical composition and content of a single cell plays a vital role in ensuring precise investigations of cellular metabolism, and is a crucial aspect of lipidomic and proteomic studies. In addition, structural knowledge provides a better understanding of cell behavior as well as the cellular and subcellular mechanisms. However, single-cell analysis can be very challenging due to the very small size of each cell as well as the large variety and extremely low concentrations of substances found in individual cells. On account of its high sensitivity and selectivity, mass spectrometry holds great promise as an effective technique for single-cell analysis. Numerous mass spectrometric techniques have been developed to elucidate the molecular profiles at the cellular level, including electrospray ionization mass spectrometry (ESI-MS), secondary ion mass spectrometry (SIMS), laser-based mass spectrometry and inductively coupled plasma mass spectrometry (ICP-MS). In this review, the recent advances in single-cell analysis by mass spectrometry are summarized. The strategies of different ionization modes to achieve single-cell analysis are classified and discussed in detail.
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Affiliation(s)
- Lei Yin
- Research Institute of Translational Medicine, The First Hospital of Jilin University, Jilin University, Dongminzhu Street, Changchun 130061, PR China.
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18
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Neumann EK, Do TD, Comi TJ, Sweedler JV. Erforschung der fundamentalen Strukturen des Lebens: Nicht zielgerichtete chemische Analyse von Einzelzellen und subzellulären Strukturen. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201811951] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Elizabeth K. Neumann
- Department of Chemistry and the Beckman Institute for Advanced Science and TechnologyUniversity of Illinois at Urbana-Champaign 405 N. Mathews Avenue Urbana IL 61801 USA
| | - Thanh D. Do
- Department of ChemistryUniversity of Tennessee 1420 Circle Drive Knoxville TN 37996 USA
| | - Troy J. Comi
- Department of Chemistry and the Beckman Institute for Advanced Science and TechnologyUniversity of Illinois at Urbana-Champaign 405 N. Mathews Avenue Urbana IL 61801 USA
| | - Jonathan V. Sweedler
- Department of Chemistry and the Beckman Institute for Advanced Science and TechnologyUniversity of Illinois at Urbana-Champaign 405 N. Mathews Avenue Urbana IL 61801 USA
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19
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Yi X, Verbeke EJ, Chang Y, Dickinson DJ, Taylor DW. Electron microscopy snapshots of single particles from single cells. J Biol Chem 2018; 294:1602-1608. [PMID: 30541924 PMCID: PMC6364765 DOI: 10.1074/jbc.ra118.006686] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Revised: 12/07/2018] [Indexed: 12/15/2022] Open
Abstract
Cryo-electron microscopy (cryo-EM) has become an indispensable tool for structural studies of biological macromolecules. Two additional predominant methods are available for studying the architectures of multiprotein complexes: 1) single-particle analysis of purified samples and 2) tomography of whole cells or cell sections. The former can produce high-resolution structures but is limited to highly purified samples, whereas the latter can capture proteins in their native state but has a low signal-to-noise ratio and yields lower-resolution structures. Here, we present a simple, adaptable method combining microfluidic single-cell extraction with single-particle analysis by EM to characterize protein complexes from individual Caenorhabditis elegans embryos. Using this approach, we uncover 3D structures of ribosomes directly from single embryo extracts. Moreover, we investigated structural dynamics during development by counting the number of ribosomes per polysome in early and late embryos. This approach has significant potential applications for counting protein complexes and studying protein architectures from single cells in developmental, evolutionary, and disease contexts.
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Affiliation(s)
- Xiunan Yi
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas 78712; Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, Texas 78712; Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78712
| | - Eric J Verbeke
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas 78712; Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, Texas 78712; Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78712
| | - Yiran Chang
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas 78712; Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, Texas 78712; Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78712
| | - Daniel J Dickinson
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas 78712; Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, Texas 78712; Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78712.
| | - David W Taylor
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas 78712; Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, Texas 78712; Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78712; LIVESTRONG Cancer Institute, Dell Medical School, Austin, Texas 78712.
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20
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Wu H, Zhu J, Huang Y, Wu D, Sun J. Microfluidic-Based Single-Cell Study: Current Status and Future Perspective. Molecules 2018; 23:E2347. [PMID: 30217082 PMCID: PMC6225124 DOI: 10.3390/molecules23092347] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Revised: 09/05/2018] [Accepted: 09/09/2018] [Indexed: 01/29/2023] Open
Abstract
Investigation of cell behavior under different environments and manual operations can give information in specific cellular processes. Among all cell-based analysis, single-cell study occupies a peculiar position, while it can avoid the interaction effect within cell groups and provide more precise information. Microfluidic devices have played an increasingly important role in the field of single-cell study owing to their advantages: high efficiency, easy operation, and low cost. In this review, the applications of polymer-based microfluidics on cell manipulation, cell treatment, and cell analysis at single-cell level are detailed summarized. Moreover, three mainly types of manufacturing methods, i.e., replication, photodefining, and soft lithography methods for polymer-based microfluidics are also discussed.
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Affiliation(s)
- Haiwa Wu
- Department of Pathology, College of Medicine, The Ohio State University, Columbus, OH 43210, USA.
| | - Jing Zhu
- Department of Pharmaceutics, College of Pharmacy, The Ohio State University, Columbus, OH 43210, USA.
| | - Yao Huang
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
| | - Daming Wu
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
- State Key Laboratory of Organic-Inorganic Composites, Beijing 100029, China.
| | - Jingyao Sun
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
- Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH 43210, USA.
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21
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Mainz ER, Wang Q, Lawrence DS, Allbritton NL. An Integrated Chemical Cytometry Method: Shining a Light on Akt Activity in Single Cells. Angew Chem Int Ed Engl 2018; 55:13095-13098. [PMID: 27647713 DOI: 10.1002/anie.201606914] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2016] [Revised: 08/20/2016] [Indexed: 12/17/2022]
Abstract
Tools to evaluate oncogenic kinase activity in small clinical samples have the power to guide precision medicine in oncology. Existing platforms have demonstrated impressive insights into the activity of protein kinases, but these technologies are unsuitable for the study of kinase behavior in large numbers of primary human cells. To address these limitations, we developed an integrated analysis system that utilizes a light-programmable, cell-permeable reporter deliverable simultaneously to many cells. The reporter's ability to act as a substrate for Akt, a key oncogenic kinase, was masked by a 2-4,5-dimethoxy 2-nitrobenzyl (DMNB) moiety. Upon exposure to ultraviolet light and release of the masking moiety, the substrate sequence enabled programmable reaction times within the cell cytoplasm. When coupled to automated single-cell capillary electrophoresis, statistically significant numbers of primary human cells were readily evaluated for Akt activity.
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Affiliation(s)
- Emilie R Mainz
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Qunzhao Wang
- Department of Chemistry, Division of Chemical Biology and Medicinal Chemistry and Department of Pharmacology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - David S Lawrence
- Department of Chemistry, Division of Chemical Biology and Medicinal Chemistry and Department of Pharmacology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Nancy L Allbritton
- Department of Chemistry and Pharmacology, University of North Carolina, Chapel Hill, NC, 27599, USA. .,Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill and Raleigh, NC, USA.
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22
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Vickerman BM, Anttila MM, Petersen BV, Allbritton NL, Lawrence DS. Design and Application of Sensors for Chemical Cytometry. ACS Chem Biol 2018; 13:1741-1751. [PMID: 29376326 DOI: 10.1021/acschembio.7b01009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The bulk cell population response to a stimulus, be it a growth factor or a cytotoxic agent, neglects the cell-to-cell variability that can serve as a friend or as a foe in human biology. Biochemical variations among closely related cells furnish the basis for the adaptability of the immune system but also act as the root cause of resistance to chemotherapy by tumors. Consequently, the ability to probe for the presence of key biochemical variables at the single-cell level is now recognized to be of significant biological and biomedical impact. Chemical cytometry has emerged as an ultrasensitive single-cell platform with the flexibility to measure an array of cellular components, ranging from metabolite concentrations to enzyme activities. We briefly review the various chemical cytometry strategies, including recent advances in reporter design, probe and metabolite separation, and detection instrumentation. We also describe strategies for improving intracellular delivery, biochemical specificity, metabolic stability, and detection sensitivity of probes. Recent applications of these strategies to small molecules, lipids, proteins, and other analytes are discussed. Finally, we assess the current scope and limitations of chemical cytometry and discuss areas for future development to meet the needs of single-cell research.
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Affiliation(s)
- Brianna M. Vickerman
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Matthew M. Anttila
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Brae V. Petersen
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Nancy L. Allbritton
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
- Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, and North Carolina State University,
Raleigh, North Carolina 27695, United States
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - David S. Lawrence
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
- Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
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23
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Murphy TW, Zhang Q, Naler LB, Ma S, Lu C. Recent advances in the use of microfluidic technologies for single cell analysis. Analyst 2017; 143:60-80. [PMID: 29170786 PMCID: PMC5839671 DOI: 10.1039/c7an01346a] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The inherent heterogeneity in cell populations has become of great interest and importance as analytical techniques have improved over the past decades. With the advent of personalized medicine, understanding the impact of this heterogeneity has become an important challenge for the research community. Many different microfluidic approaches with varying levels of throughput and resolution exist to study single cell activity. In this review, we take a broad view of the recent microfluidic developments in single cell analysis based on microwell, microchamber, and droplet platforms. We cover physical, chemical, and molecular biology approaches for cellular and molecular analysis including newly emerging genome-wide analysis.
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Affiliation(s)
- Travis W Murphy
- Department of Chemical Engineering, Virginia Tech, Blacksburg, VA 24061, USA.
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24
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Vlassakis J, Herr AE. Joule Heating-Induced Dispersion in Open Microfluidic Electrophoretic Cytometry. Anal Chem 2017; 89:12787-12796. [PMID: 29110464 DOI: 10.1021/acs.analchem.7b03096] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
While protein electrophoresis conducted in capillaries and microchannels offers high-resolution separations, such formats can be cumbersome to parallelize for single-cell analysis. One approach for realizing large numbers of concurrent separations is open microfluidics (i.e., no microchannels). In an open microfluidic device adapted for single-cell electrophoresis, we perform 100s to 1000s of simultaneous separations of endogenous proteins. The microscope slide-sized device contains cells isolated in microwells located in a ∼40 μm polyacrylamide gel. The gel supports protein electrophoresis after concurrent in situ chemical lysis of each isolated cell. During electrophoresis, Joule (or resistive) heating degrades separation performance. Joule heating effects are expected to be acute in open microfluidic devices, where a single, high-conductivity buffer expedites the transition from cell lysis to protein electrophoresis. Here, we test three key assertions. First, Joule heating substantially impacts analytical sensitivity due to diffusive losses of protein out of the open microfluidic electrophoretic (EP) cytometry device. Second, increased analyte diffusivity due to autothermal runaway Joule heating is a dominant mechanism that reduces separation resolution in EP cytometry. Finally, buffer exchange reduces diffusive losses and band broadening, even when handling single-cell lysate protein concentrations in an open device. We develop numerical simulations of Joule heating-enhanced diffusion during electrophoresis and observe ∼50% protein loss out of the gel, which is reduced using the buffer exchange. Informed by analytical model predictions of separation resolution (with Joule heating), we empirically demonstrate nearly fully resolved separations of proteins with molecular mass differences of just 4 kDa or 12% (GAPDH, 36 kDa; PS6, 32 kDa) in each of 129 single cells. The attained separation performance with buffer exchange is relevant to detection of currently unmeasurable protein isoforms responsible for cancer progression.
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Affiliation(s)
- Julea Vlassakis
- Department of Bioengineering and ‡The UC Berkeley/UCSF Graduate Program in Bioengineering, University of California Berkeley , Berkeley, California 94720, United States
| | - Amy E Herr
- Department of Bioengineering and ‡The UC Berkeley/UCSF Graduate Program in Bioengineering, University of California Berkeley , Berkeley, California 94720, United States
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25
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Lu Y, Yang L, Wei W, Shi Q. Microchip-based single-cell functional proteomics for biomedical applications. LAB ON A CHIP 2017; 17:1250-1263. [PMID: 28280819 PMCID: PMC5459479 DOI: 10.1039/c7lc00037e] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Cellular heterogeneity has been widely recognized but only recently have single cell tools become available that allow characterizing heterogeneity at the genomic and proteomic levels. We review the technological advances in microchip-based toolkits for single-cell functional proteomics. Each of these tools has distinct advantages and limitations, and a few have advanced toward being applied to address biological or clinical problems that traditional population-based methods fail to address. High-throughput single-cell proteomic assays generate high-dimensional data sets that contain new information and thus require developing new analytical frameworks to extract new biology. In this review article, we highlight a few biological and clinical applications in which microchip-based single-cell proteomic tools provide unique advantages. The examples include resolving functional heterogeneity and dynamics of immune cells, dissecting cell-cell interaction by creating a well-controlled on-chip microenvironment, capturing high-resolution snapshots of immune system functions in patients for better immunotherapy and elucidating phosphoprotein signaling networks in cancer cells for guiding effective molecularly targeted therapies.
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Affiliation(s)
- Yao Lu
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
| | - Liu Yang
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, Shanghai, China.
| | - Wei Wei
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA. and Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Qihui Shi
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, Shanghai, China.
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26
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Yamauchi KA, Herr AE. Subcellular western blotting of single cells. MICROSYSTEMS & NANOENGINEERING 2017; 3:16079. [PMID: 29333327 PMCID: PMC5764185 DOI: 10.1038/micronano.2016.79] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Although immunoassays are the de facto standard for determining subcellular protein localization in individual cells, antibody probe cross-reactivity and fixation artifacts remain confounding factors. To enhance selectivity while providing single-cell resolution, we introduce a subcellular western blotting technique capable of separately assaying proteins in the 14 pL cytoplasm and 2 pL nucleus of individual cells. To confer precision fluidic control, we describe a passive multilayer microdevice that leverages the rapid transport times afforded by miniaturization. After isolating single cells in microwells, we apply single-cell differential detergent fractionation to lyse and western blot the cytoplasmic lysate, whereas the nucleus remains intact in the microwell. Subsequently, we lyse the intact nucleus and western blot the nuclear lysate. To index each protein analysis to the originating subcellular compartment, we utilize bi-directional electrophoresis, a multidimensional separation that assays the lysate from each compartment in a distinct region of the separation axis. Single-cell bi-directional electrophoresis eliminates the need for semi-subjective image segmentation algorithms required in immunocytochemistry. The subcellular, single-cell western blot is demonstrated for six targets per cell, and successfully localizes spliceosome-associated proteins solubilized from large protein and RNA complexes, even for closely sized proteins (a 7 kDa difference). Measurement of NF-κB translocation dynamics in unfixed cells at 15-min intervals demonstrates reduced technical variance compared with immunofluorescence. This chemical cytometry assay directly measures the nucleocytoplasmic protein distribution in individual unfixed cells, thus providing insight into protein signaling in heterogeneous cell populations.
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Affiliation(s)
- Kevin A. Yamauchi
- Department of Bioengineering, University of California, Berkeley, CA 94720, USA
- The UC Berkeley—UCSF Graduate Program in Bioengineering, University of California, Berkeley, CA 94720, USA
- ()
| | - Amy E. Herr
- Department of Bioengineering, University of California, Berkeley, CA 94720, USA
- The UC Berkeley—UCSF Graduate Program in Bioengineering, University of California, Berkeley, CA 94720, USA
- ()
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27
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Mainz ER, Wang Q, Lawrence DS, Allbritton NL. An Integrated Chemical Cytometry Method: Shining a Light on Akt Activity in Single Cells. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201606914] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Emilie R. Mainz
- Department of Chemistry; University of North Carolina; Chapel Hill NC 27599 USA
| | - Qunzhao Wang
- Department of Chemistry; Division of Chemical Biology and Medicinal Chemistry and Department of Pharmacology; University of North Carolina; Chapel Hill NC 27599 USA
| | - David S. Lawrence
- Department of Chemistry; Division of Chemical Biology and Medicinal Chemistry and Department of Pharmacology; University of North Carolina; Chapel Hill NC 27599 USA
| | - Nancy L. Allbritton
- Department of Chemistry and Pharmacology; University of North Carolina; Chapel Hill NC 27599 USA
- Joint Department of Biomedical Engineering; University of North Carolina and North Carolina State University; Chapel Hill and Raleigh NC USA
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28
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Jang LW, Razu ME, Jensen EC, Jiao H, Kim J. A fully automated microfluidic micellar electrokinetic chromatography analyzer for organic compound detection. LAB ON A CHIP 2016; 16:3558-3564. [PMID: 27507322 DOI: 10.1039/c6lc00790b] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
An integrated microfluidic chemical analyzer utilizing micellar electrokinetic chromatography (MEKC) is developed using a pneumatically actuated Lifting-Gate microvalve array and a capillary zone electrophoresis (CZE) chip. Each of the necessary liquid handling processes such as metering, mixing, transferring, and washing steps are performed autonomously by the microvalve array. In addition, a method is presented for automated washing of the high resistance CZE channel for device reuse and periodic automated in situ analyses. To demonstrate the functionality of this MEKC platform, amino acids and thiols are labeled and efficiently separated via a fully automated program. Reproducibility of the automated programs for sample labeling and periodic in situ MEKC analysis was tested and found to be equivalent to conventional sample processing techniques for capillary electrophoresis analysis. This platform enables simple, portable, and automated chemical compound analysis which can be used in challenging environments.
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Affiliation(s)
- Lee-Woon Jang
- Department of Mechanical Engineering, Texas Tech University, Lubbock, TX79409, USA.
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29
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Mainz ER, Serafin DS, Nguyen TT, Tarrant TK, Sims CE, Allbritton NL. Single Cell Chemical Cytometry of Akt Activity in Rheumatoid Arthritis and Normal Fibroblast-like Synoviocytes in Response to Tumor Necrosis Factor α. Anal Chem 2016; 88:7786-92. [PMID: 27391352 PMCID: PMC6040665 DOI: 10.1021/acs.analchem.6b01801] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The etiology of rheumatoid arthritis (RA) is poorly understood, and 30% of patients are unresponsive to established treatments targeting tumor necrosis factor α (TNFα). Akt kinase is implicated in TNFα signaling and may act as a barometer of patient responses to biologic therapies. Fluorescent peptide sensors and chemical cytometry were employed to directly measure Akt activity as well as proteolytic activity in individual fibroblast-like synoviocytes (FLS) from RA and normal subjects. The specificity of the peptide reporter was evaluated and shown to be a valid measure of Akt activity in single cells. The effect of TNFα treatment on Akt activity was highly heterogeneous between normal and RA subjects, which was not observable in bulk analyses. In 2 RA subjects, a bimodal distribution of Akt activity was observed, primarily due to a subpopulation (21.7%: RA Subject 5; 23.8%: RA Subject 6) of cells in which >60% of the reporter was phosphorylated. These subjects also possessed statistically elevated proteolytic cleavage of the reporter relative to normal subjects, suggesting heterogeneity in Akt and protease activity that may play a role in the RA-affected joint. We expect that chemical cytometry studies pairing peptide reporters with capillary electrophoresis will provide valuable data regarding aberrant kinase activity from small samples of clinical interest.
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Affiliation(s)
- Emilie R. Mainz
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - D. Stephen Serafin
- Thurston Arthritis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, USA
| | - Tuong T. Nguyen
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Teresa K. Tarrant
- Thurston Arthritis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, USA
- Department of Medicine, Division of Rheumatology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina, 27599, USA
| | - Christopher E. Sims
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
- Department of Medicine, Division of Rheumatology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina, 27599, USA
| | - Nancy L. Allbritton
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
- Department of Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina 27599, USA and North Carolina State University, Raleigh, North Carolina 27695, US
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30
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Abstract
Digital PCR (dPCR) is an emerging technology for genetic analysis and clinical diagnostics. To facilitate the widespread application of dPCR, here we developed a new micropatterned superporous absorbent array chip (μSAAC) which consists of an array of microwells packed with highly porous agarose microbeads. The packed beads construct a hierarchically porous microgel which confers superior water adsorption capacity to enable spontaneous filling of PDMS microwells for fluid compartmentalization without the need of sophisticated microfluidic equipment and operation expertise. Using large λ-DNA as the model template, we validated the μSAAC for stochastic partitioning and quantitative digital detection of DNA molecules. Furthermore, as a proof-of-concept, we conducted dPCR detection and single-molecule sequencing of a mutation prevalent in blood cancer, the chromosomal translocation t(14;18), demonstrating the feasibility of the μSAAC for analysis of disease-associated mutations. These experiments were carried out using the standard molecular biology techniques and instruments. Because of its low cost, ease of fabrication, and equipment-free liquid partitioning, the μSAAC is readily adaptable to general lab settings, which could significantly facilitate the widespread application of dPCR technology in basic research and clinical practice.
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Affiliation(s)
- Yazhen Wang
- Department of Chemistry, University of Kansas, Lawrence, KS 66045, USA.
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31
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Li X, Zhao S, Hu H, Liu YM. A microchip electrophoresis-mass spectrometric platform with double cell lysis nano-electrodes for automated single cell analysis. J Chromatogr A 2016; 1451:156-163. [PMID: 27207575 DOI: 10.1016/j.chroma.2016.05.015] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2016] [Revised: 05/01/2016] [Accepted: 05/04/2016] [Indexed: 01/11/2023]
Abstract
Capillary electrophoresis-based single cell analysis has become an essential approach in researches at the cellular level. However, automation of single cell analysis has been a challenge due to the difficulty to control the number of cells injected and the irreproducibility associated with cell aggregation. Herein we report the development of a new microfluidic platform deploying the double nano-electrode cell lysis technique for automated analysis of single cells with mass spectrometric detection. The proposed microfluidic chip features integration of a cell-sized high voltage zone for quick single cell lysis, a microfluidic channel for electrophoretic separation, and a nanoelectrospray emitter for ionization in MS detection. Built upon this platform, a microchip electrophoresis-mass spectrometric method (MCE-MS) has been developed for automated single cell analysis. In the method, cell introduction, cell lysis, and MCE-MS separation are computer controlled and integrated as a cycle into consecutive assays. Analysis of large numbers of individual PC-12 neuronal cells (both intact and exposed to 25mM KCl) was carried out to determine intracellular levels of dopamine (DA) and glutamic acid (Glu). It was found that DA content in PC-12 cells was higher than Glu content, and both varied from cell to cell. The ratio of intracellular DA to Glu was 4.20±0.8 (n=150). Interestingly, the ratio drastically decreased to 0.38±0.20 (n=150) after the cells are exposed to 25mM KCl for 8min, suggesting the cells released DA promptly and heavily while they released Glu at a much slower pace in response to KCl-induced depolarization. These results indicate that the proposed MCE-MS analytical platform may have a great potential in researches at the cellular level.
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Affiliation(s)
- Xiangtang Li
- Department of Chemistry and Biochemistry, Jackson State University, 1400 Lynch St., Jackson, MS, 39217, United States
| | - Shulin Zhao
- College of Chemistry and Chemical Engineering, Guangxi Normal University, Guilin, 51004, China
| | - Hankun Hu
- Wuhan University Zhongnan Hospital, Wuhan 430071, China; Wuhan Yaogu Bio-tech, Wuhan 430075, China
| | - Yi-Ming Liu
- Department of Chemistry and Biochemistry, Jackson State University, 1400 Lynch St., Jackson, MS, 39217, United States; Wuhan Yaogu Bio-tech, Wuhan 430075, China.
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32
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Rahmanian N, Bozorgmehr M, Torabi M, Akbari A, Zarnani AH. Cell separation: Potentials and pitfalls. Prep Biochem Biotechnol 2016; 47:38-51. [PMID: 27045194 DOI: 10.1080/10826068.2016.1163579] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cell separation techniques play an indispensable part in numerous basic biological studies and even clinical settings. Although various cell isolation methods with diverse applications have been devised so far, not all of them have been able to gain widespread popularity among researchers and clinicians. There is not a single method known to be advantageous over all cell isolation techniques, and in fact, it is the researcher's aim in performing a study that determines the most suitable method. A perfect method for one study might not be necessarily a proper choice for another and likewise, expensive and complex isolation methods might not always be the best choices. There are several criteria such as cell purity, viability, activation status, and frequency that need to be given serious thought before selecting an isolation technique. Moreover, time and cost are two of the key elements that should be taken into consideration before implementing a project. Hence, here we provide a succinct description of six more popular cell separation methods with respect to their principles, advantages, and disadvantages as well as their most common applications. We further provide several key features of each technique so that it helps the researchers to take the first step toward opting for the best method that fits well into their projects.
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Affiliation(s)
- Narges Rahmanian
- a Department of Molecular Medicine, School of Advanced Technologies in Medicine , Tehran University of Medical Sciences , Tehran , Iran
| | - Mohmood Bozorgmehr
- b Oncopathology Research Center , Iran University of Medical Sciences , Tehran , Iran
| | - Monir Torabi
- c Department of Pathology, Shariati Hospital , Tehran University of Medical Sciences , Tehran , Iran
| | - Abolfazl Akbari
- d Colorectal Research Center , Iran University of Medical Sciences , Tehran , Iran
| | - Amir-Hassan Zarnani
- e Department of Immunology , School of Public Health, Tehran University of Medical Sciences , Tehran , Iran.,f Immunology Research Center , Iran University of Medical Sciences , Tehran , Iran
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33
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Single cell multiplexed assay for proteolytic activity using droplet microfluidics. Biosens Bioelectron 2016; 81:408-414. [PMID: 26995287 DOI: 10.1016/j.bios.2016.03.002] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Revised: 02/24/2016] [Accepted: 03/02/2016] [Indexed: 11/21/2022]
Abstract
Cellular enzymes interact in a post-translationally regulated fashion to govern individual cell behaviors, yet current platform technologies are limited in their ability to measure multiple enzyme activities simultaneously in single cells. Here, we developed multi-color Förster resonance energy transfer (FRET)-based enzymatic substrates and use them in a microfluidics platform to simultaneously measure multiple specific protease activities from water-in-oil droplets that contain single cells. By integrating the microfluidic platform with a computational analytical method, Proteolytic Activity Matrix Analysis (PrAMA), we are able to infer six different protease activity signals from individual cells in a high throughput manner (~100 cells/experimental run). We characterized protease activity profiles at single cell resolution for several cancer cell lines including breast cancer cell line MDA-MB-231, lung cancer cell line PC-9, and leukemia cell line K-562 using both live-cell and in-situ cell lysis assay formats, with special focus on metalloproteinases important in metastasis. The ability to measure multiple proteases secreted from or expressed in individual cells allows us to characterize cell heterogeneity and has potential applications including systems biology, pharmacology, cancer diagnosis and stem cell biology.
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34
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Zigoneanu IG, Sims CE, Allbritton NL. Separation of peptide fragments of a protein kinase C substrate fused to a β-hairpin by capillary electrophoresis. Anal Bioanal Chem 2015; 407:8999-9008. [PMID: 26427499 PMCID: PMC4662605 DOI: 10.1007/s00216-015-9065-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 09/14/2015] [Accepted: 09/17/2015] [Indexed: 01/23/2023]
Abstract
Synthetic peptides incorporating well-folded β-hairpin peptides possess advantages in a variety of cell biology applications by virtue of increased resistance to proteolytic degradation. In this study, the WKpG β-hairpin peptide fused to a protein kinase C (PKC) substrate was synthesized, and capillary-electrophoretic separation conditions for this peptide and its proteolytic fragments were developed. Fragments of WKpG-PKC were generated by enzymatic treatment with trypsin and Pronase E to produce standards for identification of degradation fragments in a cellular lysate. A simple buffer system of 250 mM H3PO4, pH 1.5 enabled separation of WKpG-PKC and its fragments by capillary electrophoresis in less than 16 min. Using a cellular lysate produced from Ba/F3 cells, the β-hairpin-conjugated substrate and its PKCα-phosphorylated product could be detected and separated from peptidase-generated fragments produced in a cell lysate. The method has potential application for identification and quantification of WKpG-PKC and its fragments in complex biological systems when the peptide is used as a reporter to assay PKC activity.
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Affiliation(s)
- Imola G Zigoneanu
- Department of Biomedical Engineering, University of North Carolina, Chapel Hill, NC, 27599, USA
- North Carolina State University, Raleigh, NC, 27695, USA
| | - Christopher E Sims
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Nancy L Allbritton
- Department of Biomedical Engineering, University of North Carolina, Chapel Hill, NC, 27599, USA.
- North Carolina State University, Raleigh, NC, 27695, USA.
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, 27599, USA.
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35
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Nehmé R, Morin P. Advances in capillary electrophoresis for miniaturizing assays on kinase enzymes for drug discovery. Electrophoresis 2015; 36:2768-2797. [DOI: 10.1002/elps.201500239] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 07/02/2015] [Accepted: 07/14/2015] [Indexed: 11/10/2022]
Affiliation(s)
- Reine Nehmé
- Institut de Chimie Organique et Analytique (ICOA); Université d'Orléans - CNRS; UMR 7311 Orléans France
| | - Philippe Morin
- Institut de Chimie Organique et Analytique (ICOA); Université d'Orléans - CNRS; UMR 7311 Orléans France
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36
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37
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Dickinson AJ, Meyer M, Pawlak EA, Gomez S, Jaspers I, Allbritton NL. Analysis of sphingosine kinase activity in single natural killer cells from peripheral blood. Integr Biol (Camb) 2015; 7:392-401. [PMID: 25786072 PMCID: PMC4566154 DOI: 10.1039/c5ib00007f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Sphingosine-1-phosphate (S1P), a lipid second messenger formed upon phosphorylation of sphingosine by sphingosine kinase (SK), plays a crucial role in natural killer (NK) cell proliferation, migration, and cytotoxicity. Dysregulation of the S1P pathway has been linked to a number of immune system disorders and therapeutic manipulation of the pathway has been proposed as a method of disease intervention. However, peripheral blood NK cells, as identified by surface markers (CD56(+)CD45(+)CD3(-)CD16) consist of a highly diverse population with distinct phenotypes and functions and it is unknown whether the S1P pathway is similarly diverse across peripheral blood NK cells. In this work, we measured the phosphorylation of sphingosine-fluorescein (SF) and subsequent metabolism of S1P fluorescein (S1PF) to form hexadecanoic acid fluorescein (HAF) in 111 single NK cells obtained from the peripheral blood of four healthy human subjects. The percentage of SF converted to S1PF or HAF was highly variable amongst the cells ranging from 0% to 100% (S1PF) and 0% to 97% (HAF). Subpopulations of cells with varying levels of S1PF formation and metabolism were readily identified. Across all subjects, the average percentage of SF converted to S1PF or HAF was 37 ± 36% and 12 ± 19%, respectively. NK cell metabolism of SF by the different subjects was also distinct with hierarchical clustering suggesting two possible phenotypes: low (<20%) or high (>50%) producers of S1PF. The heterogeneity of SK and downstream enzyme activity in NK cells may enable NK cells to respond effectively to a diverse array of pathogens as well as incipient tumor cells. NK cells from two subjects were also loaded with S1PF to assess the activity of S1P phosphatase (S1PP), which converts S1P to sphingosine. No NK cells (n = 41) formed sphingosine, suggesting that S1PP was minimally active in peripheral blood NK cells. In contrast to the SK activity, S1PP activity was homogeneous across the peripheral blood NK cells, suggesting a bias in the SK pathway towards proliferation and migration, activities supported by S1P.
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Affiliation(s)
| | - Megan Meyer
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Erica A. Pawlak
- Center for Environmental Medicine, Asthma, and Lung Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Shawn Gomez
- Department of Biomedical Engineering, University of North Carolina, Chapel Hill, NC 27599, USA and North Carolina State University, Raleigh, NC 27695, USA
| | - Ilona Jaspers
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27599, USA
- Center for Environmental Medicine, Asthma, and Lung Biology, University of North Carolina, Chapel Hill, NC 27599, USA
- Department of Pediatrics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Nancy L. Allbritton
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
- Department of Biomedical Engineering, University of North Carolina, Chapel Hill, NC 27599, USA and North Carolina State University, Raleigh, NC 27695, USA
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38
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Shehaj L, Lazo de la Vega L, Kovarik ML. Microfluidic Chemical Cytometry for Enzyme Assays of Single Cells. Methods Mol Biol 2015; 1346:221-38. [PMID: 26542725 DOI: 10.1007/978-1-4939-2987-0_15] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Cellular heterogeneity occurs, and should be probed, at multiple levels of cellular structure and physiology from the genome to enzyme activity. In particular, single-cell measures of protein levels are complemented by single-cell measurements of the activity of these proteins. Microfluidic assays of enzyme activity at the single-cell level combine moderate to high throughput with low dead volumes and the potential for automation. Herein, we describe the steps required to fabricate and operate a microfluidic device for chemical cytometry of fluorescent or fluorogenic reporters of enzyme activity in individual cells.
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Affiliation(s)
- Livia Shehaj
- Department of Chemistry, Trinity College, 300 Summit Street, Hartford, CT, 06106, USA
| | | | - Michelle L Kovarik
- Department of Chemistry, Trinity College, 300 Summit Street, Hartford, CT, 06106, USA.
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39
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Liang W, Zhang K, Yang X, Liu L, Yu H, Zhang W. Distinctive translational and self-rotational motion of lymphoma cells in an optically induced non-rotational alternating current electric field. BIOMICROFLUIDICS 2015; 9:014121. [PMID: 25759754 PMCID: PMC4336248 DOI: 10.1063/1.4913365] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Accepted: 02/10/2015] [Indexed: 05/16/2023]
Abstract
In this paper, the translational motion and self-rotational behaviors of the Raji cells, a type of B-cell lymphoma cell, in an optically induced, non-rotational, electric field have been characterized by utilizing a digitally programmable and optically activated microfluidics chip with the assistance of an externally applied AC bias potential. The crossover frequency spectrum of the Raji cells was studied by observing the different linear translation responses of these cells to the positive and negative optically induced dielectrophoresis force generated by a projected light pattern. This digitally projected spot served as the virtual electrode to generate an axisymmetric and non-uniform electric field. Then, the membrane capacitance of the Raji cells could be directly measured. Furthermore, Raji cells under this condition also exhibited a self-rotation behavior. The repeatable and controlled self-rotation speeds of the Raji cells to the externally applied frequency and voltage were systematically investigated and characterized via computer-vision algorithms. The self-rotational speed of the Raji cells reached a maximum value at 60 kHz and demonstrated a quadratic relationship with respect to the applied voltage. Furthermore, optically projected patterns of four orthogonal electrodes were also employed as the virtual electrodes to manipulate the Raji cells. These results demonstrated that Raji cells located at the center of the four electrode pattern could not be self-rotated. Instead any Raji cells that deviated from this center area would also self-rotate. Most importantly, the Raji cells did not exhibit the self-rotational behavior after translating and rotating with respect to the center of any two adjacent electrodes. The spatial distributions of the electric field generated by the optically projected spot and the pattern of four electrodes were also modeled using a finite element numerical simulation. These simulations validated that the electric field distributions were non-uniform and non-rotational. Hence, the non-uniform electric field must play a key role in the self-rotation of the Raji cells. As a whole, this study elucidates an optoelectric-coupled microfluidics-based mechanism for cellular translation and self-rotation that can be used to extract the dielectric properties of the cells without using conventional metal-based microelectrodes. This technique may provide a simpler method for label-free identification of cancerous cells with many associated clinical applications.
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Affiliation(s)
| | - Ke Zhang
- School of Mechanical Engineering, Shenyang Jianzhu University , Shenyang, China
| | - Xieliu Yang
- School of Mechanical Engineering, Shenyang Jianzhu University , Shenyang, China
| | - Lianqing Liu
- State Key Laboratory of Robotics, Shenyang Institute of Automation , Chinese Academy of Sciences, Shenyang, China
| | - Haibo Yu
- State Key Laboratory of Robotics, Shenyang Institute of Automation , Chinese Academy of Sciences, Shenyang, China
| | - Weijing Zhang
- Department of Lymphoma, Affiliated Hospital of Military Medical Academy of Sciences , Beijing, China
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40
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Zhu X, Chen Y. Simultaneous determination of electrophoretic and dielectrophoretic mobilities of human red blood cells. Electrophoresis 2014; 36:1507-13. [PMID: 25363511 DOI: 10.1002/elps.201400344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 10/14/2014] [Accepted: 10/25/2014] [Indexed: 11/07/2022]
Abstract
Electrophoresis and dielectrophoresis of cells can reveal many distinct cellular properties but are often conducted separately. Herein a simultaneous strategy was proposed, and a simple method was established by making cells migrate through a cross channel under a micro video for real-time observation. The experiment can be performed within 0.044-1 s. In combination with digital calculation based on electromagnetic theory, the method was validated to be applicable to the determination of electrophoretic and dielectrophoretic mobilities, μEP and μDEP , of human blood erythrocytes, giving μEP = -(0.87 ± 0.16)× 10(-4) cm(2) ·V(-1) · s(-1) and μDEP = -(4.5 ± 1.3) × 10(-8) cm(4) ·V(-2) ·s(-1) by vector decomposition, or μEP = -(0.89 ± 0.14) × 10(-4) cm(2) ·V(-1) · s(-1) and μDEP = -(4.6 ±1.2) × 10(-8) cm(4) ·V(-2) · s(-1) by least squares fitting, all agreeing with published data. Hydrodynamic and EOFs were eliminated for better measurement. It was found that the location of cells had a serious impact on the measurement precision, and the upstream of the cross channel along the electric field was chosen for precise measurement. The method is also extendable to the study of other cells and particles.
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Affiliation(s)
- Xiuzhen Zhu
- Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Yi Chen
- Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,Beijing National Laboratory for Molecular Science, Beijing, China
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41
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Kovarik ML, Dickinson AJ, Roy P, Poonnen RA, Fine JP, Allbritton NL. Response of single leukemic cells to peptidase inhibitor therapy across time and dose using a microfluidic device. Integr Biol (Camb) 2014; 6:164-74. [PMID: 24413844 DOI: 10.1039/c3ib40249e] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Single-cell methodologies are revealing cellular heterogeneity in numerous biological processes and pathologies. For example, cancer cells are characterized by substantial heterogeneity in basal signaling and in response to perturbations, such as drug treatment. In this work, we examined the response of 678 individual U937 (human acute myeloid leukemia) cells to an aminopeptidase-inhibiting chemotherapeutic drug (Tosedostat) over the course of 95 days. Using a fluorescent reporter peptide and a microfluidic device, we quantified the rate of reporter degradation as a function of dose. While the single-cell measurements reflected ensemble results, they added a layer of detail by revealing unique degradation patterns and outliers within the larger population. Regression modeling of the data allowed us to quantitatively explore the relationships between reporter loading, incubation time, and drug dose on peptidase activity in individual cells. Incubation time was negatively correlated with the number of peptide fragment peaks observed, while peak area (which was proportional to reporter loading) was positively correlated with both the number of fragment peaks observed and the degradation rate. Notably, a statistically significant change in the number of peaks observed was identified as dose increased from 2 to 4 μM. Similarly, a significant difference in degradation rate as a function of reporter loading was observed for doses ≥2 μM compared to the 1 μM dose. These results suggest that additional enzymes may become inhibited at doses >1 μM and >2 μM, demonstrating the utility of single-cell data to yield novel biological hypotheses.
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Affiliation(s)
- Michelle L Kovarik
- Department of Chemistry, CB 3290, University of North Carolina, Chapel Hill, NC 27599, USA
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42
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Dickinson AJ, Hunsucker SA, Armistead PM, Allbritton NL. Single-cell sphingosine kinase activity measurements in primary leukemia. Anal Bioanal Chem 2014; 406:7027-36. [PMID: 24980601 DOI: 10.1007/s00216-014-7974-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2014] [Revised: 06/06/2014] [Accepted: 06/13/2014] [Indexed: 11/30/2022]
Abstract
Sphingosine kinase (SK) is a promising therapeutic target in a number of cancers, including leukemia. Traditionally, SK has been measured in bulk cell lysates, but this technique obscures the cellular heterogeneity present in this pathway. For this reason, SK activity was measured in single cells loaded with a fluorescent sphingosine reporter. An automated capillary electrophoresis (CE) system enabled rapid separation and quantification of the phosphorylated and nonphosphorylated sphingosine reporter in single cells. SK activity was measured in tissue-cultured cells derived from chronic myelogenous leukemia (K562), primary peripheral blood mononuclear cells (PBMCs) from three patients with different forms of leukemia, and enriched leukemic blasts from a patient with acute myeloid leukemia (AML). Significant intercellular heterogeneity existed in terms of the degree of reporter phosphorylation (as much as an order of magnitude difference), the amount of reporter uptake, and the metabolites formed. In K562 cells, the average amount of reporter converted to the phosphorylated form was 39 ± 26% per cell. Of the primary PBMCs analyzed, the average amount of phosphorylated reporter was 16 ± 25%, 11 ± 26%, and 13 ± 23% in a chronic myelogenous leukemia (CML) patient, an AML patient, and a B-cell acute lymphocytic leukemia (B-ALL) patient, respectively. These experiments demonstrated the challenge of studying samples comprised of multiple cell types, with tumor blasts present at 5 to 87% of the cell population. When the leukemic blasts from a fourth patient with AML were enriched to 99% of the cell population, 19 ± 36% of the loaded sphingosine was phosphorylated. Thus, the diversity in SK activity remained even in a nearly pure tumor sample. These enriched AML blasts loaded significantly less reporter (0.12 ± 0.2 amol) relative to that loaded into the PBMCs in the other samples (≥1 amol). The variability in SK signaling may have important implications for SK inhibitors as therapeutics for leukemia and demonstrates the value of single-cell analysis in characterizing the nature of oncogenic signaling in cancer.
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43
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Ramji R, Wang M, Bhagat AAS, Tan Shao Weng D, Thakor NV, Teck Lim C, Chen CH. Single cell kinase signaling assay using pinched flow coupled droplet microfluidics. BIOMICROFLUIDICS 2014; 8:034104. [PMID: 24926389 PMCID: PMC4032411 DOI: 10.1063/1.4878635] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 05/07/2014] [Indexed: 05/10/2023]
Abstract
Droplet-based microfluidics has shown potential in high throughput single cell assays by encapsulating individual cells in water-in-oil emulsions. Ordering cells in a micro-channel is necessary to encapsulate individual cells into droplets further enhancing the assay efficiency. This is typically limited due to the difficulty of preparing high-density cell solutions and maintaining them without cell aggregation in long channels (>5 cm). In this study, we developed a short pinched flow channel (5 mm) to separate cell aggregates and to form a uniform cell distribution in a droplet-generating platform that encapsulated single cells with >55% encapsulation efficiency beating Poisson encapsulation statistics. Using this platform and commercially available Sox substrates (8-hydroxy-5-(N,N-dimethylsulfonamido)-2-methylquinoline), we have demonstrated a high throughput dynamic single cell signaling assay to measure the activity of receptor tyrosine kinases (RTKs) in lung cancer cells triggered by cell surface ligand binding. The phosphorylation of the substrates resulted in fluorescent emission, showing a sigmoidal increase over a 12 h period. The result exhibited a heterogeneous signaling rate in individual cells and showed various levels of drug resistance when treated with the tyrosine kinase inhibitor, gefitinib.
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Affiliation(s)
- Ramesh Ramji
- Department of Biomedical Engineering, National University of Singapore, Singapore 117575
| | - Ming Wang
- Department of Biomedical Engineering, National University of Singapore, Singapore 117575
| | | | | | - Nitish V Thakor
- Department of Biomedical Engineering, National University of Singapore, Singapore 117575 ; Singapore Institute for Neurotechnology, Singapore 117456
| | - Chwee Teck Lim
- Department of Biomedical Engineering, National University of Singapore, Singapore 117575 ; Department of Mechanical Engineering, National University of Singapore, Singapore 117575
| | - Chia-Hung Chen
- Department of Biomedical Engineering, National University of Singapore, Singapore 117575 ; Singapore Institute for Neurotechnology, Singapore 117456
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44
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Moini M, Martinez B. Ultrafast capillary electrophoresis/mass spectrometry with adjustable porous tip for a rapid analysis of protein digest in about a minute. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2014; 28:305-310. [PMID: 24375882 DOI: 10.1002/rcm.6786] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 11/07/2013] [Accepted: 11/12/2013] [Indexed: 06/03/2023]
Abstract
RATIONALE This paper introduces a novel ultrafast capillary electrophoresis (UFCE) mass spectrometry (MS) method comprised of a short (< 20 cm) and narrow (≤ 5 µm) capillary, with an integrated porous segment at the terminus of the capillary, for sheathless interfacing of CE to MS. The sheathless nature of the interface minimizes dead volume which is particularly important for ultrafast CE because of the small diameters of the capillaries. METHODS The separation voltage across the capillary was set to produce an electric field of ≥1000 V/cm to provide an analysis time of approximately 1 min. For the analysis of peptides and protein digests, a background electrolyte containing 0.1% cationic polymer (polybrene or Poly-E) in 0.1% acetic acid in water was used to prevent analyte-wall interaction. RESULTS Uniquely, the porous tip of the capillary is adjustable. This allows the porous tip to be pulled inside the sheath liquid for sample stacking during injection, or sample focusing in isoelectric focusing (IEF), or, alternatively, pushed outside of the sheath liquid for electrospray ionization (ESI). The adjustable interface preserves electrical conductivity during electrokinetic injection with reverse electro-osmotic flow. Therefore, pre-concentration of analytes at the capillary inlet is achieved without the need to disassemble the interface, improving the throughput. CONCLUSIONS As a proof of concept, the application of UFCE-MS was demonstrated by the analysis of a peptide mixture and a protein digest in ~1 min.
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Affiliation(s)
- Mehdi Moini
- Museum Conservation Institute, Smithsonian Institution, Suitland, MD, USA
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45
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Schrems A, Phillips J, Casey D, Wylie D, Novakova M, Sleytr UB, Klug D, Neil MAA, Schuster B, Ces O. The grab-and-drop protocol: a novel strategy for membrane protein isolation and reconstitution from single cells. Analyst 2014; 139:3296-304. [DOI: 10.1039/c4an00059e] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Samples of cell membrane were non-destructively removed from individual, live cells using optically trapped beads, and deposited into a supported lipid bilayer mounted on an S-layer protein-coated substrate.
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Affiliation(s)
- Angelika Schrems
- Department of Nanobiotechnology
- University of Natural Resources and Life Sciences
- Vienna, 1190 Austria
| | - John Phillips
- The Proxomics Group
- Institute of Chemical Biology
- Imperial College London
- London, SW7 2AZ UK
| | - Duncan Casey
- The Proxomics Group
- Institute of Chemical Biology
- Imperial College London
- London, SW7 2AZ UK
| | - Douglas Wylie
- The Proxomics Group
- Institute of Chemical Biology
- Imperial College London
- London, SW7 2AZ UK
| | - Mira Novakova
- The Proxomics Group
- Institute of Chemical Biology
- Imperial College London
- London, SW7 2AZ UK
| | - Uwe B. Sleytr
- Department of Nanobiotechnology
- University of Natural Resources and Life Sciences
- Vienna, 1190 Austria
| | - David Klug
- The Proxomics Group
- Institute of Chemical Biology
- Imperial College London
- London, SW7 2AZ UK
| | - Mark A. A. Neil
- The Proxomics Group
- Institute of Chemical Biology
- Imperial College London
- London, SW7 2AZ UK
| | - Bernhard Schuster
- Department of Nanobiotechnology
- University of Natural Resources and Life Sciences
- Vienna, 1190 Austria
| | - Oscar Ces
- The Proxomics Group
- Institute of Chemical Biology
- Imperial College London
- London, SW7 2AZ UK
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46
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Wu J, Sandberg M, Weber SG. Integrated electroosmotic perfusion of tissue with online microfluidic analysis to track the metabolism of cystamine, pantethine, and coenzyme A. Anal Chem 2013; 85:12020-7. [PMID: 24215585 DOI: 10.1021/ac403005z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We have developed an approach that integrates electroosmotic perfusion of tissue with a substrate-containing solution and online microfluidic analysis of products, in this case thiols. Using this approach we have tracked the metabolism of cystamine, pantethine and CoA in the extracellular space of organotypic hippocampal slice cultures (OHSCs). Currently, little is known about coenzyme A (CoA) biodegradation and even less is known about the regulation and kinetic characteristics for this sequential multienzyme reaction. We found that the steady state percentage yields of cysteamine from cystamine and pantethine during the transit through OHSCs were 91% ± 4% (SEM) and 0.01%-0.03%, respectively. The large difference in the yields of cysteamine can be used to explain the drugs' different toxicities and clinical effectiveness against cystinosis. The kinetic parameters of the enzyme reaction catalyzed by the ectoenzyme pantetheinase are KM,C/α = 4.4 ± 1.1 mM and Vmax,C = 29 ± 3 nM/s, where α is the percentage yield of pantethine to pantetheine through disulfide exchange. We estimate that the percentage yield of pantethine to pantetheine through disulfide exchange is approximately 0.5%. Based on the formation rate of cysteamine in the OHSCs, we obtained the overall apparent Michaelis constant and maximum reaction rate for sequential, extracellular CoA degradation in an in situ environment, which are K'M = 16 ± 4 μM, V'max = 7.1 ± 0.5 nM/s. Kinetic parameters obtained in situ, although difficult to measure, are better representations of the biochemical flux in the living organism than those from isolated enzymes in vitro.
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Affiliation(s)
- Juanfang Wu
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
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Metto EC, Evans K, Barney P, Culbertson AH, Gunasekara DB, Caruso G, Hulvey MK, da Silva JAF, Lunte SM, Culbertson CT. An integrated microfluidic device for monitoring changes in nitric oxide production in single T-lymphocyte (Jurkat) cells. Anal Chem 2013; 85:10188-95. [PMID: 24010877 PMCID: PMC3951964 DOI: 10.1021/ac401665u] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A considerable amount of attention has been focused on the analysis of single cells in an effort to better understand cell heterogeneity in cancer and neurodegenerative diseases. Although microfluidic devices have several advantages for single cell analysis, few papers have actually demonstrated the ability of these devices to monitor chemical changes in perturbed biological systems. In this paper, a new microfluidic channel manifold is described that integrates cell transport, lysis, injection, electrophoretic separation, and fluorescence detection into a single device, making it possible to analyze individual cells at a rate of 10 cells/min in an automated fashion. The system was employed to measure nitric oxide (NO) production in single T-lymphocytes (Jurkat cells) using a fluorescent marker, 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM DA). The cells were also labeled with 6-carboxyfluorescein diacetate (6-CFDA) as an internal standard. The NO production by control cells was compared to that of cells stimulated using lipopolysaccharide (LPS), which is known to cause the expression of inducible nitric oxide synthase (iNOS) in immune-type cells. Statistical analysis of the resulting electropherograms from a population of cells indicated a 2-fold increase in NO production in the induced cells. These results compare nicely to a recently published bulk cell analysis of NO.
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Affiliation(s)
- Eve C. Metto
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, USA
| | - Karsten Evans
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, USA
| | - Patrick Barney
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, USA
| | - Anne H. Culbertson
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, USA
| | - Dulan B. Gunasekara
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, USA
- Ralph N. Adams Institute for Bioanalytical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047, USA
| | - Giuseppe Caruso
- Ralph N. Adams Institute for Bioanalytical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047, USA
- Department of Chemical Science, Section of Biochemistry and Molecular Biology, The University of Catania, Italy
| | - Matthew K. Hulvey
- Ralph N. Adams Institute for Bioanalytical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047, USA
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas 66047, USA
- Akermin, Inc. St. Louis, Missouri 63132, USA
| | - Jose Alberto Fracassi da Silva
- Ralph N. Adams Institute for Bioanalytical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047, USA
- Institute of Chemistry, State University of Campinas, São Paulo, Brazil
- Instituto Nacional de Ciência e Tecnologia em Bioanalítica, INCTBio
| | - Susan M. Lunte
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, USA
- Ralph N. Adams Institute for Bioanalytical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047, USA
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas 66047, USA
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48
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Becirovic V, Doonan SR, Martin RS. Encapsulation of Fluidic Tubing and Microelectrodes in Microfluidic Devices: Integrating Off-Chip Process and Coupling Conventional Capillary Electrophoresis with Electrochemical Detection. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2013; 5:4220-4229. [PMID: 24159363 PMCID: PMC3804350 DOI: 10.1039/c3ay40809d] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
In this paper, an approach to fabricate epoxy or polystyrene microdevices with encapsulated tubing and electrodes is described. Key features of this approach include a fixed alignment between the fluidic tubing and electrodes, the ability to polish the device when desired, and the low dead volume nature of the fluidic interconnects. It is shown that a variety of tubing can be encapsulated with this approach, including fused silica capillary, polyetheretherketone (PEEK), and perfluoroalkoxy (PFA), with the resulting tubing/microchip interface not leading to significant band broadening or plug dilution. The applicability of the devices with embedded tubing is demonstrated by integrating several off-chip analytical methods to the microchip. This includes droplet transfer, droplet desegmentation, and microchip-based flow injection analysis. Off-chip generated droplets can be transferred to the microchip with minimal coalescence, while flow injection studies showed improved peak shape and sensitivity when compared to the use of fluidic interconnects with an appreciable dead volume. Importantly, it is shown that this low dead volume approach can be extended to also enable the integration of conventional capillary electrophoresis (CE) with electrochemical detection. This is accomplished by embedding fused silica capillary along with palladium (for grounding the electrophoresis voltage) and platinum (for detection) electrodes. With this approach, up to 128,000 theoretical plates for dopamine was possible. In all cases, the tubing and electrodes are housed in a rigid base; this results in extremely robust devices that will be of interest to researchers wanting to develop microchips for use by non-experts.
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Affiliation(s)
| | | | - R. Scott Martin
- Corresponding author: phone: 314-977-2836, fax: 314-977-2521,
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