1
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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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2
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Anttila MM, Vickerman BM, Wang Q, Lawrence DS, Allbritton NL. Photoactivatable Reporter to Perform Multiplexed and Temporally Controlled Measurements of Kinase and Protease Activity in Single Cells. Anal Chem 2021; 93:16664-16672. [PMID: 34865468 PMCID: PMC8753264 DOI: 10.1021/acs.analchem.1c04225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Peptide bioreporters were developed to perform multiplexed measurements of the activation of epidermal growth factor receptor kinase (EGFR), Akt kinase (Akt/protein kinase B), and proteases/peptidases in single cells. The performance characteristics of the three reporters were assessed by measuring the reporter's proteolytic stability, kinetic constants for EGFR and Akt, and dephosphorylation rate. The reporter displaying optimal performance was composed of 6-carboxyfluorescein (6-FAM) on the peptide N-terminus, an Akt substrate sequence employing a threonine phosphorylation site for Akt, followed by a tri-D arginine linker, and finally an EGFR substrate sequence bearing a phosphatase-resistant 7-(S)-hydroxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (L-htc) residue as the EGFR phosphorylation site. Importantly, use of a single electrophoretic condition separated the mono- and diphosphorylated products as well as proteolytic forms permitting the quantitation of multiple enzyme activities simultaneously using a single reporter. Because the Akt and EGFR substrates were linked, a known ratio (EGFR/Akt) of the reporter was loaded into cells. A photoactivatable version of the reporter was synthesized by adding two 4,5-dimethoxy-2-nitrobenzyl (DMNB) moieties to mask the EGFR and Akt phosphorylation sites. The DMNB moieties were readily photocleaved following exposure to 360 nm light, unmasking the phosphorylation sites on the reporter. The new photoactivatable reporter permitted multiplexed measurements of kinase signaling and proteolytic degradation in single cells in a temporally controlled manner. This work will facilitate the development of a new generation of multiplexed activity-based reporters capable of light-initiated measurement of enzymatic activity in single cells.
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Affiliation(s)
- Matthew M. Anttila
- Department of Chemistry, Chapel Hill, North Carolina 27599
- The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
- Department of Bioengineering, University of Washington, Seattle, Washington, 98125
| | - Brianna M. Vickerman
- Department of Chemistry, Chapel Hill, North Carolina 27599
- The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Qunzhao Wang
- Division of Chemical Biology and Medicinal Chemistry UNC Eshelman School of Pharmacy, Chapel Hill, North Carolina 27599
- The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - David S. Lawrence
- Department of Chemistry, Chapel Hill, North Carolina 27599
- Division of Chemical Biology and Medicinal Chemistry UNC Eshelman School of Pharmacy, Chapel Hill, North Carolina 27599
- Department of Pharmacology, School of Medicine, Chapel Hill, North Carolina 27599
- The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Nancy L. Allbritton
- Department of Bioengineering, University of Washington, Seattle, Washington, 98125
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3
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Lamanna J, Scott EY, Edwards HS, Chamberlain MD, Dryden MDM, Peng J, Mair B, Lee A, Chan C, Sklavounos AA, Heffernan A, Abbas F, Lam C, Olson ME, Moffat J, Wheeler AR. Digital microfluidic isolation of single cells for -Omics. Nat Commun 2020; 11:5632. [PMID: 33177493 PMCID: PMC7658233 DOI: 10.1038/s41467-020-19394-5] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 10/02/2020] [Indexed: 11/28/2022] Open
Abstract
We introduce Digital microfluidic Isolation of Single Cells for -Omics (DISCO), a platform that allows users to select particular cells of interest from a limited initial sample size and connects single-cell sequencing data to their immunofluorescence-based phenotypes. Specifically, DISCO combines digital microfluidics, laser cell lysis, and artificial intelligence-driven image processing to collect the contents of single cells from heterogeneous populations, followed by analysis of single-cell genomes and transcriptomes by next-generation sequencing, and proteomes by nanoflow liquid chromatography and tandem mass spectrometry. The results described herein confirm the utility of DISCO for sequencing at levels that are equivalent to or enhanced relative to the state of the art, capable of identifying features at the level of single nucleotide variations. The unique levels of selectivity, context, and accountability of DISCO suggest potential utility for deep analysis of any rare cell population with contextual dependencies. Multi-Omic approaches are a powerful way for obtaining in-depth understanding of a cell’s state. Here the authors present DISCO, combining digital microfluidics, laser cell lysis, and artificial intelligence-driven image processing to analyze single-cell genomes, transcriptomes and proteomes in a mixed population.
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Affiliation(s)
- Julian Lamanna
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada.,Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, M5S 3E1, Canada
| | - Erica Y Scott
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada.,Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, M5S 3E1, Canada
| | - Harrison S Edwards
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, M5S 3E1, Canada.,Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, ON, M5S 3G9, Canada
| | - M Dean Chamberlain
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada.,Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, M5S 3E1, Canada
| | - Michael D M Dryden
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada
| | - Jiaxi Peng
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada
| | - Barbara Mair
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, M5S 3E1, Canada
| | - Adam Lee
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, ON, M5S 3G9, Canada
| | - Calvin Chan
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada
| | - Alexandros A Sklavounos
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada.,Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, M5S 3E1, Canada
| | - Austin Heffernan
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, M5S 3E1, Canada
| | - Farhana Abbas
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada.,Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, M5S 3E1, Canada
| | - Charis Lam
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada
| | - Maxwell E Olson
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada
| | - Jason Moffat
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, M5S 3E1, Canada.,Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, ON, M5S 3G9, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON, M5S 3H6, Canada
| | - Aaron R Wheeler
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada. .,Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, M5S 3E1, Canada. .,Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, ON, M5S 3G9, Canada.
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4
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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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5
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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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6
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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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7
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Gazor M, Ashraf Talesh SS, Hosseini SN, Javidanbardan A, Khatami M. High recovery of intracellular recombinant HBsAg from Pichia pastoris
via continuous pulsed laser cell disruption system optimized by response surface methodology. Biotechnol Appl Biochem 2018; 66:91-100. [DOI: 10.1002/bab.1701] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Accepted: 10/08/2018] [Indexed: 11/05/2022]
Affiliation(s)
- Maryam Gazor
- Production and Research Complex, Department of Recombinant Products; Pasteur Institute of Iran; Tehran Iran
- Department of Chemical Engineering, Faculty of Engineering; University of Guilan; Rasht Iran
| | | | - Seyed Nezamedin Hosseini
- Production and Research Complex, Department of Recombinant Products; Pasteur Institute of Iran; Tehran Iran
- Viral Vaccines Research Center; Pasteur Institute of Iran; Tehran Iran
| | - Amin Javidanbardan
- Production and Research Complex, Department of Recombinant Products; Pasteur Institute of Iran; Tehran Iran
| | - Maryam Khatami
- Production and Research Complex, Department of Recombinant Products; Pasteur Institute of Iran; Tehran Iran
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8
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Khan M, Mao S, Li W, Lin J. Microfluidic Devices in the Fast‐Growing Domain of Single‐Cell Analysis. Chemistry 2018; 24:15398-15420. [DOI: 10.1002/chem.201800305] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Indexed: 12/19/2022]
Affiliation(s)
- Mashooq Khan
- Department of Chemistry, Beijing Key Laboratory of Microanalytical Methods and Instrumentation, MOE Key Laboratory of Bioorganic Phosphorus Chemistry, & Chemical Biology Tsinghua University Beijing 100084 China
| | - Sifeng Mao
- Department of Chemistry, Beijing Key Laboratory of Microanalytical Methods and Instrumentation, MOE Key Laboratory of Bioorganic Phosphorus Chemistry, & Chemical Biology Tsinghua University Beijing 100084 China
| | - Weiwei Li
- Department of Chemistry, Beijing Key Laboratory of Microanalytical Methods and Instrumentation, MOE Key Laboratory of Bioorganic Phosphorus Chemistry, & Chemical Biology Tsinghua University Beijing 100084 China
| | - Jin‐Ming Lin
- Department of Chemistry, Beijing Key Laboratory of Microanalytical Methods and Instrumentation, MOE Key Laboratory of Bioorganic Phosphorus Chemistry, & Chemical Biology Tsinghua University Beijing 100084 China
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9
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Zhang W, Li N, Zeng H, Nakajima H, Lin JM, Uchiyama K. Inkjet Printing Based Separation of Mammalian Cells by Capillary Electrophoresis. Anal Chem 2017; 89:8674-8677. [DOI: 10.1021/acs.analchem.7b02624] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Weifei Zhang
- Department of Applied
Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, Minamiohsawa, Hachioji, Tokyo 192-0397, Japan
| | - Nan Li
- Department
of Chemistry, Beijing Key Laboratory of Microanalytical Methods and
Instrumentation, The Key Laboratory of Bioorganic Phosphorus Chemistry
and Chemical Biology, Tsinghua University, Beijing 100084, China
| | - Hulie Zeng
- Department of Applied
Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, Minamiohsawa, Hachioji, Tokyo 192-0397, Japan
| | - Hizuru Nakajima
- Department of Applied
Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, Minamiohsawa, Hachioji, Tokyo 192-0397, Japan
| | - Jin-Ming Lin
- Department
of Chemistry, Beijing Key Laboratory of Microanalytical Methods and
Instrumentation, The Key Laboratory of Bioorganic Phosphorus Chemistry
and Chemical Biology, Tsinghua University, Beijing 100084, China
| | - Katsumi Uchiyama
- Department of Applied
Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, Minamiohsawa, Hachioji, Tokyo 192-0397, Japan
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10
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Lajoinie G, De Cock I, Coussios CC, Lentacker I, Le Gac S, Stride E, Versluis M. In vitro methods to study bubble-cell interactions: Fundamentals and therapeutic applications. BIOMICROFLUIDICS 2016; 10:011501. [PMID: 26865903 PMCID: PMC4733084 DOI: 10.1063/1.4940429] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 01/05/2016] [Indexed: 05/08/2023]
Abstract
Besides their use as contrast agents for ultrasound imaging, microbubbles are increasingly studied for a wide range of therapeutic applications. In particular, their ability to enhance the uptake of drugs through the permeabilization of tissues and cell membranes shows great promise. In order to fully understand the numerous paths by which bubbles can interact with cells and the even larger number of possible biological responses from the cells, thorough and extensive work is necessary. In this review, we consider the range of experimental techniques implemented in in vitro studies with the aim of elucidating these microbubble-cell interactions. First of all, the variety of cell types and cell models available are discussed, emphasizing the need for more and more complex models replicating in vivo conditions together with experimental challenges associated with this increased complexity. Second, the different types of stabilized microbubbles and more recently developed droplets and particles are presented, followed by their acoustic or optical excitation methods. Finally, the techniques exploited to study the microbubble-cell interactions are reviewed. These techniques operate over a wide range of timescales, or even off-line, revealing particular aspects or subsequent effects of these interactions. Therefore, knowledge obtained from several techniques must be combined to elucidate the underlying processes.
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Affiliation(s)
- Guillaume Lajoinie
- Physics of Fluids Group, MESA+ Institute for Nanotechnology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente , Enschede, The Netherlands
| | - Ine De Cock
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent Research Group on Nanomedicines, Faculty of Pharmaceutical Sciences, Ghent University , Ghent, Belgium
| | | | - Ine Lentacker
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent Research Group on Nanomedicines, Faculty of Pharmaceutical Sciences, Ghent University , Ghent, Belgium
| | - Séverine Le Gac
- MESA+ Institute for Nanotechnology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente , Enschede, The Netherlands
| | - Eleanor Stride
- Institute of Biomedical Engineering, University of Oxford , Oxford, United Kingdom
| | - Michel Versluis
- Physics of Fluids Group, MESA+ Institute for Nanotechnology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente , Enschede, The Netherlands
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11
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Mainz ER, Dobes NC, Allbritton NL. Pronase E-Based Generation of Fluorescent Peptide Fragments: Tracking Intracellular Peptide Fate in Single Cells. Anal Chem 2015; 87:7987-95. [PMID: 26171808 PMCID: PMC6026012 DOI: 10.1021/acs.analchem.5b01929] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The ability to track intracellular peptide proteolysis at the single cell level is of growing interest, particularly as short peptide sequences continue to play important roles as biosensors, therapeutics, and endogenous participants in antigen processing and intracellular signaling. We describe a rapid and inexpensive methodology to generate fluorescent peptide fragments from a parent sequence with diverse chemical properties, including aliphatic, nonpolar, basic, acidic, and non-native amino acids. Four peptide sequences with existing biochemical applications were fragmented using incubation with Pronase E and/or formic acid, and in each case a complete set of fluorescent fragments was generated for use as proteolysis standards in chemical cytometry. Fragment formation and identity was monitored with capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) and matrix assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-MS) to confirm the presence of all sequences and yield fragmentation profiles across Pronase E concentrations which can readily be used by others. As a pilot study, Pronase E-generated standards from an Abl kinase sensor and an ovalbumin antigenic peptide were then employed to identify proteolysis products arising from the metabolism of these sequences in single cells. The Abl kinase sensor fragmented at 4.2 ± 4.8 zmol μM(-1) s(-1) and the majority of cells possessed similar fragment identities. In contrast, an ovalbumin epitope peptide was degraded at 8.9 ± 0.1 zmol μM(-1) s(-1), but with differential fragment formation between individual cells. Overall, Pronase E-generated peptide standards were a rapid and efficient method to identify proteolysis products from cells.
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Affiliation(s)
- Emilie R. Mainz
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Nicholas C. Dobes
- Department of Chemistry, University of North Carolina, 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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12
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Gross BC, Anderson KB, Meisel JE, McNitt MI, Spence DM. Polymer Coatings in 3D-Printed Fluidic Device Channels for Improved Cellular Adherence Prior to Electrical Lysis. Anal Chem 2015; 87:6335-41. [PMID: 25973637 DOI: 10.1021/acs.analchem.5b01202] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
This paper describes the design and fabrication of a polyjet-based three-dimensional (3D)-printed fluidic device where poly(dimethylsiloxane) (PDMS) or polystyrene (PS) were used to coat the sides of a fluidic channel within the device to promote adhesion of an immobilized cell layer. The device was designed using computer-aided design software and converted into an .STL file prior to printing. The rigid, transparent material used in the printing process provides an optically transparent path to visualize endothelial cell adherence and supports integration of removable electrodes for electrical cell lysis in a specified portion of the channel (1 mm width × 0.8 mm height × 2 mm length). Through manipulation of channel geometry, a low-voltage power source (500 V max) was used to selectively lyse adhered endothelial cells in a tapered region of the channel. Cell viability was maintained on the device over a 5 day period (98% viable), though cell coverage decreased after day 4 with static media delivery. Optimal lysis potentials were obtained for the two fabricated device geometries, and selective cell clearance was achieved with cell lysis efficiencies of 94 and 96%. The bottleneck of unknown surface properties from proprietary resin use in fabricating 3D-printed materials is overcome through techniques to incorporate PDMS and PS.
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Affiliation(s)
- Bethany C Gross
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48823, United States
| | - Kari B Anderson
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48823, United States
| | - Jayda E Meisel
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48823, United States
| | - Megan I McNitt
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48823, United States
| | - Dana M Spence
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48823, United States
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13
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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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14
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Hydrodynamic determinants of cell necrosis and molecular delivery produced by pulsed laser microbeam irradiation of adherent cells. Biophys J 2014; 105:2221-31. [PMID: 24209868 DOI: 10.1016/j.bpj.2013.09.027] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 08/28/2013] [Accepted: 09/12/2013] [Indexed: 12/11/2022] Open
Abstract
Time-resolved imaging, fluorescence microscopy, and hydrodynamic modeling were used to examine cell lysis and molecular delivery produced by picosecond and nanosecond pulsed laser microbeam irradiation in adherent cell cultures. Pulsed laser microbeam radiation at λ = 532 nm was delivered to confluent monolayers of PtK2 cells via a 40×, 0.8 NA microscope objective. Using laser microbeam pulse durations of 180-1100 ps and pulse energies of 0.5-10.5 μJ, we examined the resulting plasma formation and cavitation bubble dynamics that lead to laser-induced cell lysis, necrosis, and molecular delivery. The cavitation bubble dynamics are imaged at times of 0.5 ns to 50 μs after the pulsed laser microbeam irradiation, and fluorescence assays assess the resulting cell viability and molecular delivery of 3 kDa dextran molecules. Reductions in both the threshold laser microbeam pulse energy for plasma formation and the cavitation bubble energy are observed with decreasing pulse duration. These energy reductions provide for increased precision of laser-based cellular manipulation including cell lysis, cell necrosis, and molecular delivery. Hydrodynamic analysis reveals critical values for the shear-stress impulse generated by the cavitation bubble dynamics governs the location and spatial extent of cell necrosis and molecular delivery independent of pulse duration and pulse energy. Specifically, cellular exposure to a shear-stress impulse J≳0.1 Pa s ensures cell lysis or necrosis, whereas exposures in the range of 0.035≲J≲0.1 Pa s preserve cell viability while also enabling molecular delivery of 3 kDa dextran. Exposure to shear-stress impulses of J≲0.035 Pa s leaves the cells unaffected. Hydrodynamic analysis of these data, combined with data from studies of 6 ns microbeam irradiation, demonstrates the primacy of shear-stress impulse in determining cellular outcome resulting from pulsed laser microbeam irradiation spanning a nearly two-orders-of-magnitude range of pulse energy and pulse duration. These results provide a mechanistic foundation and design strategy applicable to a broad range of laser-based cellular manipulation procedures.
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15
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Proctor A, Herrera-Loeza SG, Wang Q, Lawrence DS, Yeh JJ, Allbritton NL. Measurement of protein kinase B activity in single primary human pancreatic cancer cells. Anal Chem 2014; 86:4573-80. [PMID: 24716819 PMCID: PMC4018172 DOI: 10.1021/ac500616q] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 04/09/2014] [Indexed: 02/06/2023]
Abstract
An optimized peptide substrate was used to measure protein kinase B (PKB) activity in single cells. The peptide substrate was introduced into single cells, and capillary electrophoresis was used to separate and quantify nonphosphorylated and phosphorylated peptide. The system was validated in three model pancreatic cancer cell lines before being applied to primary cells from human pancreatic adenocarcinomas propagated in nude mice. As measured by phosphorylation of peptide substrate, each tumor cell line exhibited statistically different median levels of PKB activity (65%, 21%, and 4% phosphorylation in PANC-1 (human pancreatic carcinoma), CFPAC-1 (human metastatic ductal pancreatic adenocarcinoma), and HPAF-II cells (human pancreatic adenocarcinoma), respectively) with CFPAC-1 cells demonstrating two populations of cells or bimodal behavior in PKB activation levels. The primary cells exhibited highly variable PKB activity at the single cell level, with some cells displaying little to no activity and others possessing very high levels of activity. This system also enabled simultaneous characterization of peptidase action in single cells by measuring the amount of cleaved peptide substrate in each cell. The tumor cell lines displayed degradation rates statistically similar to one another (0.02, 0.06, and 0.1 zmol pg(-1) s(-1), for PANC-1, CFPAC-1, and HPAF-II cells, respectively) while the degradation rate in primary cells was 10-fold slower. The peptide cleavage sites also varied between tissue-cultured and primary cells, with 5- and 8-residue fragments formed in tumor cell lines and only the 8-residue fragment formed in primary cells. These results demonstrate the ability of chemical cytometry to identify important differences in enzymatic behavior between primary cells and tissue-cultured cell lines.
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Affiliation(s)
- Angela Proctor
- Department
of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - S. Gabriela Herrera-Loeza
- Lineberger
Comprehensive Cancer Center, University
of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, United States
| | - Qunzhao Wang
- Department
of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - David S. Lawrence
- Department
of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, United States
- Division
of Chemical Biology and Medicinal Chemistry, School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Jen Jen Yeh
- Departments
of Surgery and Pharmacology, University
of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Nancy L. Allbritton
- Department
of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, United States
- Department
of Biomedical Engineering, University of
North Carolina, Chapel Hill, North Carolina 27599, United States and North Carolina State University, Raleigh, North Carolina 27695, United States
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16
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Nan L, Jiang Z, Wei X. Emerging microfluidic devices for cell lysis: a review. LAB ON A CHIP 2014; 14:1060-73. [PMID: 24480982 DOI: 10.1039/c3lc51133b] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Intracellular components containing information about genetic and disease characteristics are key substances to clinical diagnostics. Cell lysis is therefore a crucial step for efficient extraction and the subsequent analysis of intracellular components. With the advent of advanced manufacturing techniques, a number of micro systems have been proposed and applied for manipulating cells on chips. In this paper, we review emerging microfluidic devices for cell lysis. Different lysis mechanisms and related techniques are compared. The technical details, advantages, and limitations of various microfluidic devices are discussed.
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Affiliation(s)
- Lang Nan
- State Key Laboratory for Manufacturing Systems Engineering, Xi'An Jiaotong University, 28 Xianning West Road, 710049, Xi'An, China.
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17
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Electrophoretically mediated microanalysis for in-capillaryelectrical cell lysis and fast enzyme quantification by capillary electrophoresis. Anal Bioanal Chem 2013; 405:9159-67. [DOI: 10.1007/s00216-013-7332-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 08/23/2013] [Accepted: 08/29/2013] [Indexed: 01/29/2023]
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18
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Yang S, Proctor A, Cline LL, Houston KM, Waters ML, Allbritton NL. β-Turn sequences promote stability of peptide substrates for kinases within the cytosolic environment. Analyst 2013; 138:4305-11. [PMID: 23785707 DOI: 10.1039/c3an00874f] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A strategy was developed to extend the lifetime of an peptide-based substrate for Abl kinase in the cytosolic environment. Small β-turn structures were added to the peptide's N-terminus to block entry into peptidase catalytic sites. The influence of the size of the β-turn and two covalent cross-linking strategies on the rate of hydrolysis was assessed. The most peptidase-resistant substrate was degraded at a rate of 0.6 pmol mg(-1) s(-1) and possessed a half-life of 20.3 ± 1.7 min in a Baf/BCR-ABL cytosolic lysate, representing 16- and 40-fold improvements, respectively, over that of a control peptide lacking the β-turn structure. Furthermore, the kcat/KM value of this peptide was 432 μM(-1) min(-1), a 1.25× increase over the unmodified control, verifying that the added β-turn did not hinder the substrate properties of the peptide. This improved peptide was microinjected into single Baf/BCR-ABL cells and substrate phosphorylation measured. Zero to forty percent of the peptide was phosphorylated in the single cells. In contrast, when the control peptide without a β-turn was loaded into cells, the peptide was too rapidly degraded to detect phosphorylation. This work demonstrates that small β-turn structures can render peptides more resistant to hydrolysis while retaining substrate efficacy and shows that these stabilized peptides have the potential to be of high utility in single-cell enzyme assays.
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Affiliation(s)
- Shan Yang
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
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19
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Phillips RM, Bair E, Lawrence DS, Sims CE, Allbritton NL. Measurement of protein tyrosine phosphatase activity in single cells by capillary electrophoresis. Anal Chem 2013; 85:6136-42. [PMID: 23682679 DOI: 10.1021/ac401106e] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A fluorescent peptide substrate was used to measure dephosphorylation by protein tyrosine phosphatases (PTP) in cell lysates and single cells and to investigate the effect of environmental toxins on PTP activity in these systems. Dephosphorylation of the substrate by PTPN1 and PTPN2 obeyed Michaelis-Menten kinetics, with KM values of 770 ± 250 and 290 ± 54 nM, respectively. Dose-response curves and IC50 values were determined for the inhibition of these two enzymes by the environmental toxins Zn(2+) and 1,2-naphthoquinone, as well as pervanadate. In A431 cell lysates, the reporter was a poor substrate for peptidases (degradation rate of 100 ± 8.2 fmol min(-1) mg(-1)) but an excellent substrate for phosphatases (dephosphorylation rate of 1.4 ± 0.3 nmol min(-1) mg(-1)). Zn(2+), 1,2-naphthoquinone, and pervanadate inhibited dephosphorylation of the reporter in cell lysates with IC50 values of 470 nM, 35 μM, and 100 nM, respectively. Dephosphorylation of the reporter, following loading into living single cells, occurred at rates of at least 2 pmol min(-1) mg(-1). When single cells were exposed to 1,2-naphthoquinone (50 μM), Zn(2+) (100 μM), and pervandate (1 mM), dephosphorylation was inhibited with median values and first and third quartile values of 41 (Q1 = 0%, Q3 = 96%), 50 (Q1 = 46%, Q3 = 74%), and 53% (Q1 = 36%, Q3 = 77%), respectively, demonstrating both the impact of these toxic exposures on cell signaling and the heterogeneity of response between cells. This approach will provide a valuable tool for the study of PTP dynamics, particularly in small, heterogeneous populations such as human biopsy specimens.
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Affiliation(s)
- Ryan M Phillips
- Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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20
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Dickinson AJ, Armistead PM, Allbritton NL. Automated capillary electrophoresis system for fast single-cell analysis. Anal Chem 2013; 85:4797-804. [PMID: 23527995 DOI: 10.1021/ac4005887] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Capillary electrophoresis (CE) is a promising technique for single-cell analysis, but its use in biological studies has been limited by low throughput. This paper presents an automated platform employing microfabricated cell traps and a three-channel system for rapid buffer exchange for fast single-cell CE. Cells loaded with fluorescein and Oregon green were analyzed at a throughput of 3.5 cells/min with a resolution of 2.3 ± 0.6 for the fluorescein and Oregon green. Cellular protein kinase B (PKB) activity, as measured by immunofluorescence staining of phospho-PKB, was not altered, suggesting that this stress-activated kinase was not upregulated during the CE experiments and that basal cell physiology was not perturbed prior to cell lysis. The activity of sphingosine kinase (SK), which is often upregulated in cancer, was measured in leukemic cells by loading a sphingosine-fluorescein substrate into cells. Sphingosine fluorescein (SF), sphingosine-1-phosphate fluorescein (S1PF), and a third fluorescent species were identified in single cells. A single-cell throughput of 2.1 cells/min was achieved for 219 total cells. Eighty-eight percent of cells possessed upregulated SK activity, although subpopulations of cells with markedly different SK activity relative to that of the population average were readily identified. This system was capable of stable and reproducible separations of biological compounds in hundreds of adherent and nonadherent cells, enabling measurements of previously uncharacterized biological phenomena.
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Affiliation(s)
- Alexandra J Dickinson
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, United States
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21
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Xu W, Allbritton N, Lawrence DS. SRC kinase regulation in progressively invasive cancer. PLoS One 2012; 7:e48867. [PMID: 23145001 PMCID: PMC3492248 DOI: 10.1371/journal.pone.0048867] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 10/01/2012] [Indexed: 11/18/2022] Open
Abstract
Metastatic progression is a multistep process that involves tumor growth and survival, motility and invasion, and subsequent proliferation in an inappropriate environment. The Src protein tyrosine kinase has been implicated in many of the biochemical pathways that drive these behaviors. Although Src itself is only rarely mutated in human tumors, its aberrant activity has been noted in various cancers and suggested to serve as a barometer of metastatic potential. With these features in mind, we examined Src kinase regulation at the structural, enzymatic, and expression levels as a function of progressively invasive prostate cancer cell lines. Surprisingly, both total Src content and kinase activity decrease with increasing cell line aggressiveness, an observation that appears to be inconsistent with the well-documented role of Src in the signaling pathways that drive growth and invasion. However, we do observe a direct correlation between Src kinase specific activity (total Src kinase activity/total Src content) and metastatic aggressiveness, possibly suggesting that in highly aggressive cell lines, key signaling enzymes are globally recruited to drive the cancerous phenotype. In addition, although the expected enhanced phosphorylation of Src at Tyr-416 (activation site) is present in the most aggressive prostate cancer cell lines, unexpectedly high phosphorylation levels at the Tyr-527 inhibitory site are observed as well. The latter, rather than representative of inhibited enzyme, is more indicative of primed Src responsive to local phosphorylated binding partners.
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Affiliation(s)
- Weichen Xu
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Nancy Allbritton
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Department of Biomedical Engineering, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Department of Pharmacology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - David S. Lawrence
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Department of Pharmacology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- * E-mail:
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22
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Proctor A, Wang Q, Lawrence DS, Allbritton NL. Development of a peptidase-resistant substrate for single-cell measurement of protein kinase B activation. Anal Chem 2012; 84:7195-202. [PMID: 22881604 PMCID: PMC3428732 DOI: 10.1021/ac301489d] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
An iterative design strategy using three criteria was utilized to develop a peptidase-resistant substrate peptide for protein kinase B. Libraries of peptides possessing non-native amino acids were screened for time to 50% phosphorylation, degradation half-life within a lysate, and appearance of a dominant fragment. The lead peptide possessed a half-life of 92 ± 7 and 16 ± 2 min in HeLa and LNCaP cytosolic lysates, respectively, representing a 4.6- and 2.7-fold lifetime improvement over that of the starting peptide. The redesigned peptide possessed a 4.5-fold improvement in phosphorylation efficiency compared to the starting peptide. The same peptide fragments were formed when the lead peptide was incubated in a lysate or loaded into single cells although the fragments formed in significantly different ratios suggesting that distinct peptidases metabolized the peptide in the two preparations. The rate of peptide degradation and phosphorylation was on average 0.1 ± 0.2 zmol pg(-1) s(-1) and 0.04 ± 0.08 zmol pg(-1) s(-1), respectively, for single LNCaP cells loaded with 4 ± 8 μM of peptide. Peptidase-resistant kinase substrates should find widespread utility in both lysate-based and single-cell assays of kinase activity.
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Affiliation(s)
- Angela Proctor
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Qunzhao Wang
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
| | - David S. Lawrence
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
- Division of Chemical Biology and Medicinal Chemistry, School of Pharmacy, 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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23
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Proctor A, Wang Q, Lawrence DS, Allbritton NL. Metabolism of peptide reporters in cell lysates and single cells. Analyst 2012; 137:3028-38. [PMID: 22314840 PMCID: PMC3697743 DOI: 10.1039/c2an16162a] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The stability of an Abl kinase substrate peptide in a cytosolic lysate and in single cells was characterized. In the cytosolic lysate, the starting peptide was metabolized at an average initial rate of 1.7 ± 0.3 zmol pg(-1) s(-1) with a t(1/2) of 1.3 min. Five different fragments formed over time; however, a dominant cleavage site was identified. Multiple rational design cycles were utilized to develop a lead peptide with a phenylalanine and alanine replaced by an (N-methyl)phenylalanine and isoleucine, respectively, to attain cytosolic peptidase resistance while maintaining Abl substrate efficacy. This lead peptide possessed a 15-fold greater lifetime in the cytosolic lysate while attaining a 7-fold improvement in k(cat) as an Abl kinase substrate compared to the starting peptide. However, when loaded into single cells, the starting peptide and lead peptide possessed nearly identical degradation rates and an altered pattern of fragmentation relative to that in cell lysates. Preferential accumulation of a fragment with cleavage at an Ala-Ala bond in single cells suggested that dissimilar peptidases act on the peptides in the lysate versus single cells. A design strategy for peptide stabilization, analogous to that demonstrated for the lysate, should be effective for stabilization in single cells.
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Affiliation(s)
- Angela Proctor
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
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24
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Lee SS, Horvath P, Pelet S, Hegemann B, Lee LP, Peter M. Quantitative and dynamic assay of single cell chemotaxis. Integr Biol (Camb) 2012; 4:381-90. [PMID: 22230969 DOI: 10.1039/c2ib00144f] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We have developed a single-cell assay platform that allows quantitative analysis of single cell chemotaxis by dynamic morphogenetic gradients, subcellular microscopic imaging and automated image analysis, and have applied these to measure cellular polarization of budding yeast. The computer-controlled microfluidic device regulates the gradient profile at any given time, and allows quantitative monitoring of cell morphology and the localization and expression of specific marker proteins during the dynamic polarization process. With this integrated experimental system, we compare the polarized signaling response of wild-type and far1-H7 mutant cells, which express a truncated Far1 protein unable to interact with Cdc24. Our results confirm that Far1 functions as an adaptor that recruits polarity establishment proteins to the site of extracellular signaling. Moreover, by changing the gradient profile and estimating the number of bound surface receptors, we quantitatively address why surprisingly small differences in pheromone concentration across yeast cells can be amplified into a robust polarity axis. This integrated single cell experimental platform thus opens the possibility to quantitatively investigate the molecular regulatory mechanism of chemotaxis in yeast, which serves as a paradigm to understand the fundamental processes involved in cancer metastasis, angiogenesis and axon generation.
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Affiliation(s)
- Sung Sik Lee
- Institute of Biochemistry, ETH Zurich, Zurich, CH 8093, Switzerland
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25
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Abstract
Electroporation is a powerful technique to increase the permeability of cell membranes and subsequently introduce foreign materials into cells. Pores are created in the cell membrane upon application of an electric field (kV/cm). Most applications employ bulk electroporation, at the scale of 1 mL of cells (ca. one million cells). However, recent progresses have shown the interest to miniaturize the technique to a single cell. Single cell electroporation is achieved either using microelectrodes which are placed in close vicinity to one cell, or in a microfluidic format. We focus here on this second approach, where individual cells are trapped in micrometer-size structures within a microchip, exposed in situ to a high electric field and loaded with either a dye (proof-of-principle experiments) or a plasmid. Specifically, we present one device that includes an array of independent electroporation sites for customized and successive poration of nine cells. The different steps of the single cell electroporation protocol are detailed including cell sample preparation, cell trapping, actual cell poration and on-chip detection of pore formation. Electroporation is illustrated here with the transport of dyes through the plasma membrane, the transfection of cells with GFP-encoding plasmids, and the study of the ERK1 signaling pathway using a GFP-ERK1 protein construct expressed by the cells after their transfection with the corresponding plasmid. This last example highlights the power of microfluidics with the implementation of various steps of a process (cell poration, culture, imaging) performed at the single cell level, on a single device.
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Affiliation(s)
- Séverine Le Gac
- BIOS the Lab-on-a-Chip Group, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands.
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26
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Brown RB, Hewel JA, Emili A, Audet J. Identification of enzyme-converted peptide products from single cells using capillary electrophoresis and liquid chromatography-mass spectrometry. Methods Mol Biol 2012; 853:17-28. [PMID: 22323137 DOI: 10.1007/978-1-61779-567-1_3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Single-cell analysis using chemical methods, otherwise known as chemical cytometry, promises to provide significant leaps in understanding signaling processes which result in cellular behavior. Sensitive methods for chemical cytometry such as capillary electrophoresis can detect and quantify multiple targets; however, conclusive identification of detected analytes is required for useful data to be obtained. Here, we demonstrate a method for determining the identity of enzyme-converted peptide products from single cells using a combination of capillary electrophoresis and liquid chromatography-mass spectrometry (LC-MS).
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Affiliation(s)
- Robert B Brown
- Institute of Biomaterials and Biomedical Engineering (IBBME), University of Toronto, Toronto, ON, Canada
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27
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Grohman JK, Kottegoda S, Gorelick RJ, Allbritton NL, Weeks KM. Femtomole SHAPE reveals regulatory structures in the authentic XMRV RNA genome. J Am Chem Soc 2011; 133:20326-34. [PMID: 22126209 PMCID: PMC3241870 DOI: 10.1021/ja2070945] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Higher-order structure influences critical functions in nearly all noncoding and coding RNAs. Most single-nucleotide resolution RNA structure determination technologies cannot be used to analyze RNA from scarce biological samples, like viral genomes. To make quantitative RNA structure analysis applicable to a much wider array of RNA structure-function problems, we developed and applied high-sensitivity selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) to structural analysis of authentic genomic RNA of the xenotropic murine leukemia virus-related virus (XMRV). For analysis of fluorescently labeled cDNAs generated in high-sensitivity SHAPE experiments, we developed a two-color capillary electrophoresis approach with zeptomole molecular detection limits and subfemtomole sensitivity for complete SHAPE experiments involving hundreds of individual RNA structure measurements. High-sensitivity SHAPE data correlated closely (R = 0.89) with data obtained by conventional capillary electrophoresis. Using high-sensitivity SHAPE, we determined the dimeric structure of the XMRV packaging domain, examined dynamic interactions between the packaging domain RNA and viral nucleocapsid protein inside virion particles, and identified the packaging signal for this virus. Despite extensive sequence differences between XMRV and the intensively studied Moloney murine leukemia virus, architectures of the regulatory domains are similar and reveal common principles of gammaretrovirus RNA genome packaging.
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Affiliation(s)
- Jacob K. Grohman
- Department of Chemistry, University of North Carolina, Chapel Hill 27599-3290
| | - Sumith Kottegoda
- Department of Chemistry, University of North Carolina, Chapel Hill 27599-3290
| | - Robert J. Gorelick
- AIDS and Cancer Virus Program, Science Applications International Corporation-Frederick, Inc., National Cancer Institute-Frederick, Frederick, MD 21702-1201
| | - Nancy L. Allbritton
- Department of Chemistry, University of North Carolina, Chapel Hill 27599-3290
- Department of Biomedical Engineering, University of North Carolina, Chapel Hill, NC 27599 and North Carolina State University, Raleigh, NC 27695
| | - Kevin M. Weeks
- Department of Chemistry, University of North Carolina, Chapel Hill 27599-3290
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28
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Hargis AD, Alarie JP, Ramsey J. Characterization of cell lysis events on a microfluidic device for high-throughput single cell analysis. Electrophoresis 2011; 32:3172-9. [PMID: 22025127 PMCID: PMC3517164 DOI: 10.1002/elps.201100229] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 08/03/2011] [Accepted: 08/05/2011] [Indexed: 11/09/2022]
Abstract
A microfluidic device capable of rapidly analyzing cells in a high-throughput manner using electrical cell lysis is further characterized. In the experiments performed, cell lysis events were studied using an electron multiplying charge coupled device camera with high frame rate (>100 fps) data collection. It was found that, with this microfluidic design, the path that a cell follows through the electric field affects the amount of lysate injected into the analysis channel. Elimination of variable flow paths through the electric field was achieved by coating the analysis channel with a polyamine compound to reverse the electroosmotic flow (EOF). EOF reversal forced the cells to take the same path through the electric field. The improved control of the cell trajectory will reduce device-imposed bias on the analysis and maximizes the amount of lysate injected into the analysis channel for each cell, resulting in improved analyte detection capabilities.
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Affiliation(s)
- Amy D Hargis
- Department of Chemistry, Chapman Hall Room 251, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3216
| | - JP Alarie
- Department of Chemistry, Chapman Hall Room 251, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3216
| | - J.M. Ramsey
- Department of Chemistry, Chapman Hall Room 251, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3216
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29
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Wu T, Mohanty S, Gomez-Godinez V, Shi LZ, Liaw LH, Miotke J, Meyer RL, Berns MW. Neuronal growth cones respond to laser-induced axonal damage. J R Soc Interface 2011; 9:535-47. [PMID: 21831892 DOI: 10.1098/rsif.2011.0351] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Although it is well known that damage to neurons results in release of substances that inhibit axonal growth, release of chemical signals from damaged axons that attract axon growth cones has not been observed. In this study, a 532 nm 12 ns laser was focused to a diffraction-limited spot to produce site-specific damage to single goldfish axons in vitro. The axons underwent a localized decrease in thickness ('thinning') within seconds. Analysis by fluorescence and transmission electron microscopy indicated that there was no gross rupture of the cell membrane. Mitochondrial transport along the axonal cytoskeleton immediately stopped at the damage site, but recovered over several minutes. Within seconds of damage nearby growth cones extended filopodia towards the injury and were often observed to contact the damaged site. Turning of the growth cone towards the injured axon also was observed. Repair of the laser-induced damage was evidenced by recovery of the axon thickness as well as restoration of mitochondrial movement. We describe a new process of growth cone response to damaged axons. This has been possible through the interface of optics (laser subcellular surgery), fluorescence and electron microscopy, and a goldfish retinal ganglion cell culture model.
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Affiliation(s)
- Tao Wu
- Beckman Laser Institute and Medical Clinic, University of California, Irvine, CA 92617, USA.
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30
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Pedersen BW, Sinks LE, Breitenbach T, Schack NB, Vinogradov SA, Ogilby PR. Single cell responses to spatially controlled photosensitized production of extracellular singlet oxygen. Photochem Photobiol 2011; 87:1077-91. [PMID: 21668871 DOI: 10.1111/j.1751-1097.2011.00951.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The response of individual HeLa cells to extracellularly produced singlet oxygen was examined. The spatial domain of singlet oxygen production was controlled using the combination of a membrane-impermeable Pd porphyrin-dendrimer, which served as a photosensitizer, and a focused laser, which served to localize the sensitized production of singlet oxygen. Cells in close proximity to the domain of singlet oxygen production showed morphological changes commonly associated with necrotic cell death. The elapsed postirradiation "waiting period" before necrosis became apparent depended on: (1) the distance between the cell membrane and the domain irradiated, (2) the incident laser fluence and, as such, the initial concentration of singlet oxygen produced and (3) the lifetime of singlet oxygen. The data imply that singlet oxygen plays a key role in this process of light-induced cell death. The approach of using extracellularly generated singlet oxygen to induce cell death can provide a solution to a problem that often limits mechanistic studies of intracellularly photosensitized cell death: it can be difficult to quantify the effective light dose, and hence singlet oxygen concentration, when using an intracellular photosensitizer.
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Affiliation(s)
- Brian W Pedersen
- Department of Chemistry, Center for Oxygen Microscopy and Imaging, Aarhus University, Århus, Denmark
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31
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Phillips KS, Lai HH, Johnson E, Sims CE, Allbritton NL. Continuous analysis of dye-loaded, single cells on a microfluidic chip. LAB ON A CHIP 2011; 11:1333-41. [PMID: 21327264 PMCID: PMC3462073 DOI: 10.1039/c0lc00370k] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Continuous analysis of two dyes loaded into single mammalian cells using laser-based lysis combined with electrophoretic separation was developed and characterized on microfluidic chips. The devices employed hydrodynamic flow to transport cells to a junction where they were mechanically lysed by a laser-generated cavitation bubble. An electric field then attracted the analyte into a separation channel while the membranous remnants passed through the intersection towards a waste reservoir. Phosphatidylcholine (PC)-supported bilayer membrane coatings (SBMs) provided a weakly negatively charged surface and prevented cell fouling from interfering with device performance. Cell lysis using a picosecond-pulsed laser on-chip did not interfere with concurrent electrophoretic separations. The effect of device parameters on performance was evaluated. A ratio of 2 : 1 was found to be optimal for the focusing-channel : flow-channel width and 3 : 1 for the flow-channel : separation-channel width. Migration times decreased with increased electric field strengths up to 333 V cm(-1), at which point the field strength was sufficient to move unlysed cells and cellular debris into the electrophoretic channel. The migration time and full width half-maximum (FWHM) of the peaks were independent of cell velocity for velocities between 0.03 and 0.3 mm s(-1). Separation performance was independent of the exact lysis location when lysis was performed near the outlet of the focusing channel. The migration time for cell-derived fluorescein and fluorescein carboxylate was reproducible with <10% RSD. Automated cell detection and lysis were required to reduce peak FWHM variability to 30% RSD. A maximum throughput of 30 cells min(-1) was achieved. Device stability was demonstrated by analyzing 600 single cells over a 2 h time span.
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Affiliation(s)
- K. Scott Phillips
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Hsuan Hong Lai
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Emily Johnson
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Christopher E. Sims
- Department of Chemistry, 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. Fax: +1 919 843 7825
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32
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Jiang D, Sims CE, Allbritton NL. Single-cell analysis of phosphoinositide 3-kinase and phosphatase and tensin homolog activation. Faraday Discuss 2011; 149:187-200; discussion 227-45. [PMID: 21221426 DOI: 10.1039/c005362g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
A single-cell assay was developed to measure the activation of phosphoinositide 3-kinase (PI3K) using microanalytical chemical separations and a fluorescently labeled lipid substrate. Phosphatidyl-inositol 4,5 bisphosphate labeled on its acyl chain with Bodipy fluorescein (Bodipy Fl PIP(2)) was utilized as a substrate for both in vitro and cell-based assays. Detection limits for the substrate and product of the PI3K reaction were 10 to 20 zeptomol. In vitro assays with PI3K with and without pharmacologic inhibitors demonstrated that Bodipy Fl PIP(2) was converted to phosphatidyl-inositol 3,4,5 trisphosphate (Bodipy Fl PIP(3)). Bodipy Fl PIP(3) could be back converted to Bodipy Fl PIP(2) by the phosphatase PTEN. When Bodipy Fl PIP(2) was added to a cell lysate, 1.4 fmol of the Bodipy Fl PIP(3) were produced per ng of protein in the cytoplasmic extract in 10 min. Addition of Bodipy Fl PIP(3) to a cell lysate yielded 3 fmol of Bodipy Fl PIP(2) per ng of protein in 8 min. Both Bodipy Fl PIP(2) and Bodipy Fl PIP(3) were measureable in single cells and the two species could be inter-converted. Under the appropriate conditions, a fluorescent diacylglycerol was also detected in single cells. When the FcepsilonR 1 receptor on the cells loaded with the fluorescent lipid was cross-linked, the amount of Bodipy Fl PIP(3) generated per cell increased 4-fold over that of unstimulated cells. This production of Bodipy Fl PIP(3) was blocked by wortmannin. Chemical cytometry utilizing the fluorescent lipids will be of value in understanding lipid metabolism at the single-cell level.
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Affiliation(s)
- Dechen Jiang
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
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33
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Quinto-Su PA, Kuss C, Preiser PR, Ohl CD. Red blood cell rheology using single controlled laser-induced cavitation bubbles. LAB ON A CHIP 2011; 11:672-8. [PMID: 21183972 DOI: 10.1039/c0lc00182a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The deformability of red blood cells (RBCs) is an important property that allows the cells to squeeze through small capillary vessels and can be used as an indicator for disease. We present a microfluidic based technique to quantify the deformability of RBCs by stretching a collection of RBCs on a timescale of tens of microseconds in a microfluidic chamber. This confinement constrains the motion of the cell to the imaging plane of the microscope during a transient cavitation bubble event generated with a focused and pulsed laser. We record and analyze the shape recovery of the cells with a high-speed camera and obtain a power law in time, consistent with other dynamic rheological results of RBCs. The extracted exponents are used to characterize the elastic properties of the cells. We obtain statistically significant differences of the exponents between populations of untreated RBCs and RBCs treated with two different reagents: neuraminidase reduces the cell rigidity, while wheat germ agglutinin stiffens the cell confirming previous experiments. This cavitation based technique is a candidate for high-throughput screening of elastic cell properties because many cells can be probed simultaneously in situ, thus with no pre-treatment.
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Affiliation(s)
- Pedro A Quinto-Su
- Nanyang Technological University, School of Physical and Mathematical Sciences, Department of Physics and Applied Physics, Singapore.
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34
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Jiang D, Sims CE, Allbritton NL. Microelectrophoresis platform for fast serial analysis of single cells. Electrophoresis 2010; 31:2558-65. [PMID: 20603824 DOI: 10.1002/elps.201000054] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
A capillary-based microelectrophoresis platform for fast serial analysis of single cells is described. In this system, the capillary remains fixed and a two-channel flow system is used to rapidly switch the buffer surrounding the capillary inlet from a physiological buffer to an electrophoretic buffer. Single cells are retained in the physiologic buffer channel utilizing an array of cell microwells patterned into the channel floor. The defined addresses of the cells on the array enable the sequential delivery of individual cells to the inlet of the capillary, where a focused laser pulse lyses the cell. The cell chamber is moved along a preordained route so that the inlet of the capillary is located in the electrophoresis buffer for separation and the physiological buffer during cell sampling. The throughput of the current system is limited by peak overlap between successive samples. Key characterizations of this system including the fluid flow rates, the cell array dimensions, and laser energies were performed. To demonstrate this system, 28 cells loaded with Oregon green and fluorescein were serially analyzed in under 16 min, a rate of 1.8 cells/min.
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Affiliation(s)
- Dechen Jiang
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, USA
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35
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Chiu DT. Interfacing droplet microfluidics with chemical separation for cellular analysis. Anal Bioanal Chem 2010; 397:3179-83. [DOI: 10.1007/s00216-010-3686-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Accepted: 03/17/2010] [Indexed: 11/28/2022]
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36
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Brown RB, Hewel JA, Emili A, Audet J. Single amino acid resolution of proteolytic fragments generated in individual cells. Cytometry A 2010; 77:347-55. [DOI: 10.1002/cyto.a.20880] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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37
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Agarwal A, Wang M, Olofsson J, Orwar O, Weber SG. Control of the release of freely diffusing molecules in single-cell electroporation. Anal Chem 2009; 81:8001-8. [PMID: 19731948 PMCID: PMC2938737 DOI: 10.1021/ac9010292] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Single-cell electroporation using an electrolyte-filled capillary is an emerging technique for transient pore formation in adherent cells. Because adherent cells do not have a simple and consistent shape and because the electric field emanating from the tip of the capillary is inhomogeneous, the Schwan equation based on spherical cells in homogeneous electrical fields does not apply. We sought to determine experimental and cell parameters that influence the outcome of a single-cell electroporation experiment. A549 cells were exposed to the thiol-reactive dye Thioglo-1, leading to green fluorescence from intracellular thiol adducts. Electroporation causes a decrease with time of the intracellular fluorescence intensity of Thioglo-1-loaded cells from diffusive loss of thiol adducts. The transient curves thus obtained are well-described by a simple model originally developed by Puc et al. We find that the final fluorescence following electroporation is related to the capillary tip-to-cell distance and cell size (specifically, 2(A/pi)(1/2) where A is the area of the cell's image in pixels. This quantity is the diameter if the image is a circle). In separate experiments, the relationship obtained can be used to control the final fluorescence following electroporation by adjusting the tip-to-cell distance based on cell size. The relationship was applied successfully to A549 as well as DU 145 and PC-3 cells. Finally, F-tests show that the variability in the final fluorescence (following electroporation) is decreased when the tip-to-cell distance is controlled according to the derived relationship in comparison to experiments in which the tip-cell distance is a constant irrespective of cell size.
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Affiliation(s)
| | | | | | | | - Stephen G. Weber
- Corresponding author. Phone: +1(412)624-8520. Fax: +1(412)624-1668.
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38
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Yu L, Mohanty S, Zhang J, Genc S, Kim MK, Berns MW, Chen Z. Digital holographic microscopy for quantitative cell dynamic evaluation during laser microsurgery. OPTICS EXPRESS 2009; 17:12031-8. [PMID: 19582118 PMCID: PMC2860952 DOI: 10.1364/oe.17.012031] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Digital holographic microscopy allows determination of dynamic changes in the optical thickness profile of a transparent object with sub-wavelength accuracy. Here, we report a quantitative phase laser microsurgery system for evaluation of cellular/ sub-cellular dynamic changes during laser micro-dissection. The proposed method takes advantage of the precise optical manipulation by the laser microbeam and quantitative phase imaging by digital holographic microscopy with high spatial and temporal resolution. This system will permit quantitative evaluation of the damage and/or the repair of the cell or cell organelles in real time.
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Affiliation(s)
- Lingfeng Yu
- Beckman Laser Institute, University of California, Irvine, Irvine, CA 92617, USA.
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39
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Chiu DT, Lorenz RM. Chemistry and biology in femtoliter and picoliter volume droplets. Acc Chem Res 2009; 42:649-58. [PMID: 19260732 DOI: 10.1021/ar8002464] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The basic unit of any biological system is the cell, and malfunctions at the single-cell level can result in devastating diseases; in cancer metastasis, for example, a single cell seeds the formation of a distant tumor. Although tiny, a cell is a highly heterogeneous and compartmentalized structure: proteins, lipids, RNA, and small-molecule metabolites constantly traffic among intracellular organelles. Gaining detailed information about the spatiotemporal distribution of these biomolecules is crucial to our understanding of cellular function and dysfunction. To access this information, we need sensitive tools that are capable of extracting comprehensive biochemical information from single cells and subcellular organelles. In this Account, we outline our approach and highlight our progress toward mapping the spatiotemporal organization of information flow in single cells. Our technique is centered on the use of femtoliter- and picoliter-sized droplets as nanolabs for manipulating single cells and subcellular compartments. We have developed a single-cell nanosurgical technique for isolating select subcellular structures from live cells, a capability that is needed for the high-resolution manipulation and chemical analysis of single cells. Our microfluidic approaches for generating single femtoliter-sized droplets on demand include both pressure and electric field methods; we have also explored a design for the on-demand generation of multiple aqueous droplets to increase throughput. Droplet formation is only the first step in a sequence that requires manipulation, fusion, transport, and analysis. Optical approaches provide the most convenient and precise control over the formed droplets with our technology platform; we describe aqueous droplet manipulation with optical vortex traps, which enable the remarkable ability to dynamically "tune" the concentration of the contents. Integration of thermoelectric manipulations with these techniques affords further control. The amount of chemical information that can be gleaned from single cells and organelles is critically dependent on the methods available for analyzing droplet contents. We describe three techniques we have developed: (i) droplet encapsulation, rapid cell lysis, and fluorescence-based single-cell assays, (ii) physical sizing of the subcellular organelles and nanoparticles in droplets, and (iii) capillary electrophoresis (CE) analysis of droplet contents. For biological studies, we are working to integrate the different components of our technology into a robust, automated device; we are also addressing an anticipated need for higher throughput. With progress in these areas, we hope to cement our technique as a new tool for studying single cells and organelles with unprecedented molecular detail.
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Affiliation(s)
- Daniel T. Chiu
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700
| | - Robert M. Lorenz
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700
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40
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Abstract
Owing to the small quantities of analytes and small volumes involved in single-cell analysis techniques, manipulation strategies must be chosen carefully. The lysis of single cells for downstream chemical analysis in capillaries and lab-on-a-chip devices can be achieved by optical, acoustic, mechanical, electrical or chemical means, each having their respective strengths and weaknesses. Selection of the most appropriate lysis method will depend on the particulars of the downstream cell lysate processing. Ultrafast lysis techniques such as the use of highly focused laser pulses or pulses of high voltage are suitable for applications requiring high temporal resolution. Other factors, such as whether the cells are adherent or in suspension and whether the proteins to be collected are desired to be native or denatured, will determine the suitability of detergent-based lysis methods. Therefore, careful selection of the proper lysis technique is essential for gathering accurate data from single cells.
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Affiliation(s)
- Robert B Brown
- Institute of Biomaterials and Biomedical Engineering (IBBME), University of Toronto, 164 College Street, Room 407, Toronto, Ontario, Canada
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41
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Lai HH, Quinto-Su PA, Sims CE, Bachman M, Li GP, Venugopalan V, Allbritton NL. Characterization and use of laser-based lysis for cell analysis on-chip. J R Soc Interface 2008; 5 Suppl 2:S113-21. [PMID: 18583277 DOI: 10.1098/rsif.2008.0177.focus] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We demonstrate the use of a pulsed laser microbeam for cell lysis followed by electrophoretic separation of cellular analytes in a microfluidic device. The influence of pulse energy and laser focal point within the microchannel on the threshold for plasma formation was measured. The thickness of the poly(dimethylsiloxane) (PDMS) layer through which the beam travelled was a critical determinant of the threshold energy. An effective optical path length, Leff, for the laser beam can be used to predict the threshold for optical breakdown at different microchannel locations. A key benefit of laser-based cell lysis is the very limited zone (less than 5 microm) of lysis. A second asset is the rapid cell lysis times (approx. microseconds). These features enable two analytes, fluorescein and Oregon Green, from a cell to be electrophoretically separated in the channel in which cell lysis occurred. The resolution and efficiency of the separation of the cellular analytes are similar to those of standards demonstrating the feasibility of using a pulsed laser microbeam in single-cell analysis.
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Affiliation(s)
- Hsuan-Hong Lai
- Department of Electrical Engineering and Computer Science, University of California, Irvine, CA 92697, USA
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42
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Mohanty SK, Mohanty KS, Berns MW. Manipulation of mammalian cells using a single-fiber optical microbeam. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:054049. [PMID: 19021429 PMCID: PMC4034744 DOI: 10.1117/1.2983663] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The short working distance of microscope objectives has severely restricted the application of optical micromanipulation techniques at larger depths. We show the first use of fiber-optic tweezers toward controlled guidance of neuronal growth cones and stretching of neurons. Further, by mode locking, the fiber-optic tweezers beam was converted to fiber-optic scissors, enabling dissection of neuronal processes and thus allowing study of the subsequent response of neurons to localized injury. At high average powers, lysis of a three-dimensionally trapped cell was accomplished.
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Affiliation(s)
- Samarendra K Mohanty
- University of California-Irvine, Beckman Laser Institute, Irvine, California 92612, USA.
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43
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Yu L, Mohanty S, Liu G, Genc S, Chen Z, Berns MW. Quantitative phase evaluation of dynamic changes on cell membrane during laser microsurgery. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:050508. [PMID: 19021378 PMCID: PMC3380242 DOI: 10.1117/1.2997375] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The ability to inject exogenous material as well as to alter subcellular structures in a minimally invasive manner using a laser microbeam has been useful for cell biologists to study the structure-function relationship in complex biological systems. We describe a quantitative phase laser microsurgery system, which takes advantage of the combination of laser microirradiation and short-coherence interference microscopy. Using this method, quantitative phase images and the dynamic changes of phase during the process of laser microsurgery of red blood cells (RBCs) can be evaluated in real time. This system would enable absolute quantitation of localized alteration/damage to transparent phase objects, such as the cell membrane or intracellular structures, being exposed to the laser microbeam. Such quantitation was not possible using conventional phase-contrast microscopy.
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44
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Otieno AC, Mwongela SM. Capillary electrophoresis-based methods for the determination of lipids--a review. Anal Chim Acta 2008; 624:163-74. [PMID: 18706322 DOI: 10.1016/j.aca.2008.06.026] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2008] [Revised: 06/12/2008] [Accepted: 06/17/2008] [Indexed: 01/08/2023]
Abstract
Capillary electrophoresis (CE) is a high-resolution technique for the separation of complex biological and chemical mixtures. CE continues to emerge as a powerful tool in the determination of lipids. Here we review the analytical potential of CE for the determination of a wide range of lipids. The different classes of lipids are introduced, and the different modes of CE and optimization methods for the separation of lipids are described. The advantages and disadvantages of the different modes of CE compared to traditional methods like gas chromatography (GC) and liquid chromatography (LC) in the determination of lipids are discussed. Finally, the potential of CE in the determination of lipids in the future is illustrated.
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Affiliation(s)
- Anthony C Otieno
- Department of Chemistry, Kent State University, Kent, OH 44242, USA
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45
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Kottegoda S, Aoto PC, Sims CE, Allbritton NL. Biarsenical-tetracysteine motif as a fluorescent tag for detection in capillary electrophoresis. Anal Chem 2008; 80:5358-66. [PMID: 18522433 DOI: 10.1021/ac8003242] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Biarsenical dyes complexed to tetracysteine motifs have proven to be highly useful fluorescent dyes in labeling specific cellular proteins for microscopic imaging. Their many advantages include membrane permeability, relatively small size, stoichiometric labeling, high affinity, and an assortment of excitation/emission wavelengths. The goal of the current study was to determine whether the biarsenical labeling scheme could be extended to fluorescent detection of analytes in capillary electrophoresis. Recombinant protein or synthesized peptides containing the optimized tetracysteine motif "-C-C-P-G-C-C-" were labeled with biarsenical dyes and then analyzed by micellar electrokinetic capillary chromatography (MEKC). The biarsenical-tetracysteine complex was stable and remained fluorescent under standard MEKC conditions for peptide and protein separations. The detection limit following electrophoresis in a capillary was less than 3 x 10(-20) mol with a simple laser-induced fluorescence system. A mixture of multiple biarsenical-labeled peptides and a protein were easily resolved. Demonstrating that the label did not interfere with bioactivity, a peptide-based enzyme substrate conjugated to the tetracysteine motif and labeled with a biarsenical dye retained its ability to be phosphorylated by the parent kinase. The feasibility of using this label for chemical cytometry experiments was shown by intracellular labeling and subsequent analysis of a recombinant protein possessing the tetracysteine motif expressed in living cells. The extension of the biarsenical-tetracysteine tag to fluorescent labeling of peptides and proteins in chemical separations is a valuable addition to biochemical and cell-based investigations.
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Affiliation(s)
- Sumith Kottegoda
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA
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46
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Marc PJ, Sims CE, Bachman M, Li GP, Allbritton NL. Fast-lysis cell traps for chemical cytometry. LAB ON A CHIP 2008; 8:710-6. [PMID: 18432340 PMCID: PMC2605510 DOI: 10.1039/b719301g] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Electrically addressable cell traps were integrated with capillary electrophoresis for the analysis of the contents of single adherent cells. Electrodes composed of indium tin oxide were patterned on a glass surface followed by formation of topographical cell traps using 1002F photoresist. Single cells trapped in the holes could be lysed in less than 66 ms by applying a brief electric field (10 ms) across the electrode beneath the cell and the ground electrode placed in the aqueous media above the cell traps. The gas formed during cell lysis remained localized within the cavity formed by the 1002F photoresist. The retention of the gas in the cell trap enabled the cell traps to be coupled to an overlying capillary without blockage of the capillary. Single cells cultured in the traps were loaded with fluorescein and Oregon Green and then electrically lysed. By simultaneous application of an electric field to the capillary, the cell's contents were loaded into the capillary and electrophoretically separated. Orgeon Green and fluorescein from a single cell were fully resolved in less than two minutes. The use of a single patterned electrode beneath the 1002F cell trap yielded a simple easily fabricated design that was robust when immersed in aqueous solutions. Moreover, the design can easily be scaled up to create arrays of adherent cells for serial analyses using a single capillary or for parallel analysis by mating to an array of capillaries. Enhancing the rate of analysis of single adherent cells would enable a greater understanding of cellular physiology.
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Affiliation(s)
- Paul J. Marc
- Department of Biomedical Engineering, University of California, Irvine, California, 92697, USA
| | - Christopher E. Sims
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, 27599-3290, USA. E-mail: ; Fax: +1-919-962-2388
| | - Mark Bachman
- Department of Biomedical Engineering, University of California, Irvine, California, 92697, USA
- Department of Electrical Engineering and Computer Science, University of California, Irvine, California, 92697, USA
| | - G. P. Li
- Department of Biomedical Engineering, University of California, Irvine, California, 92697, USA
- Department of Electrical Engineering and Computer Science, University of California, Irvine, California, 92697, USA
| | - Nancy L. Allbritton
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, 27599-3290, USA. E-mail: ; Fax: +1-919-962-2388
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47
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Hellman AN, Rau KR, Yoon HH, Venugopalan V. Biophysical response to pulsed laser microbeam-induced cell lysis and molecular delivery. JOURNAL OF BIOPHOTONICS 2008; 1:24-35. [PMID: 19343632 PMCID: PMC3155384 DOI: 10.1002/jbio.200710010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Cell lysis and molecular delivery in confluent monolayers of PtK(2) cells are achieved by the delivery of 6 ns, lambda = 532 nm laser pulses via a 40x, 0.8 NA microscope objective. With increasing distance from the point of laser focus we find regions of (a) immediate cell lysis; (b) necrotic cells that detach during the fluorescence assays; (c) permeabilized cells sufficient to facilitate the uptake of small (3 kDa) FITC-conjugated Dextran molecules in viable cells; and (d) unaffected, viable cells. The spatial extent of cell lysis, cell detachment, and molecular delivery increased with laser pulse energy. Hydrodynamic analysis from time-resolved imaging studies reveal that the maximum wall shear stress associated with the pulsed laser microbeam-induced cavitation bubble expansion governs the location and spatial extent of each of these regions independent of laser pulse energy. Specifically, cells exposed to maximum wall shear stresses tau(w, max) > 190 +/- 20 kPa are immediately lysed while cells exposed to tau(w, max) > 18 +/- 2 kPa are necrotic and subsequently detach. Cells exposed to tau(w, max) in the range 8-18 kPa are viable and successfully optoporated with 3 kDa Dextran molecules. Cells exposed to tau(w, max) < 8 +/- 1 kPa remain viable without molecular delivery. These findings provide the first direct correlation between pulsed laser microbeam-induced shear stresses and subsequent cellular outcome.
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Affiliation(s)
- Amy N. Hellman
- Dept. of Bioengineering, University of California, San Diego, La Jolla, CA USA 92093-0412
- Dept. of Chemical Engineering & Materials Science, University of California, Irvine, Irvine, CA USA 92697-2575
- Laser Microbeam and Medical Program, Beckman Laser Institute and Medical Clinic, University of California, Irvine, Irvine, CA USA 92612
| | - Kaustubh R. Rau
- Dept. of Chemical Engineering & Materials Science, University of California, Irvine, Irvine, CA USA 92697-2575
- Laser Microbeam and Medical Program, Beckman Laser Institute and Medical Clinic, University of California, Irvine, Irvine, CA USA 92612
- National Centre for Biological Sciences, TATA Institute of Fundamental Research, Bangalore, INDIA
| | - Helen H. Yoon
- Dept. of Chemistry, University of California, Irvine, Irvine, CA
| | - Vasan Venugopalan
- Dept. of Chemical Engineering & Materials Science, University of California, Irvine, Irvine, CA USA 92697-2575
- Laser Microbeam and Medical Program, Beckman Laser Institute and Medical Clinic, University of California, Irvine, Irvine, CA USA 92612
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Quinto-Su PA, Lai HH, Yoon HH, Sims CE, Allbritton NL, Venugopalan V. Examination of laser microbeam cell lysis in a PDMS microfluidic channel using time-resolved imaging. LAB ON A CHIP 2008; 8:408-14. [PMID: 18305858 PMCID: PMC2525503 DOI: 10.1039/b715708h] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
We use time-resolved imaging to examine the lysis dynamics of non-adherent BAF-3 cells within a microfluidic channel produced by the delivery of single highly-focused 540 ps duration laser pulses at lambda = 532 nm. Time-resolved bright-field images reveal that the delivery of the pulsed laser microbeam results in the formation of a laser-induced plasma followed by shock wave emission and cavitation bubble formation. The confinement offered by the microfluidic channel constrains substantially the cavitation bubble expansion and results in significant deformation of the PDMS channel walls. To examine the cell lysis and dispersal of the cellular contents, we acquire time-resolved fluorescence images of the process in which the cells were loaded with a fluorescent dye. These fluorescence images reveal cell lysis to occur on the nanosecond to microsecond time scale by the plasma formation and cavitation bubble dynamics. Moreover, the time-resolved fluorescence images show that while the cellular contents are dispersed by the expansion of the laser-induced cavitation bubble, the flow associated with the bubble collapse subsequently re-localizes the cellular contents to a small region. This capacity of pulsed laser microbeam irradiation to achieve rapid cell lysis in microfluidic channels with minimal dilution of the cellular contents has important implications for their use in lab-on-a-chip applications.
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Affiliation(s)
- Pedro A. Quinto-Su
- Department of Chemical Engineering & Materials Science, University of California, 916 Engineering Tower, Irvine, Irvine, CA, 92697, USA. E-mail: ; Fax: +1 (949) 824-2541; Tel: +1 (949) 824-5802
- Laser Microbeam and Medical Program, Beckman Laser Institute and Medical Clinic, University of California, Irvine, Irvine, CA, 92612, USA
| | - Hsuan-Hong Lai
- Department of Electrical Engineering & Computer Science, University of California, Irvine, Irvine, CA, 92697, USA
| | - Helen H. Yoon
- Department of Chemistry, University of California, Irvine, Irvine, CA, 92697, USA
| | - Christopher E. Sims
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Nancy L. Allbritton
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Vasan Venugopalan
- Department of Chemical Engineering & Materials Science, University of California, 916 Engineering Tower, Irvine, Irvine, CA, 92697, USA. E-mail: ; Fax: +1 (949) 824-2541; Tel: +1 (949) 824-5802
- Laser Microbeam and Medical Program, Beckman Laser Institute and Medical Clinic, University of California, Irvine, Irvine, CA, 92612, USA
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Lee KJ, Mwongela SM, Kottegoda S, Borland L, Nelson AR, Sims CE, Allbritton NL. Determination of sphingosine kinase activity for cellular signaling studies. Anal Chem 2008; 80:1620-7. [PMID: 18197698 DOI: 10.1021/ac702305q] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Regulation of sphingosine and sphingosine-1-phosphate concentrations is of growing interest due to their importance in cellular signal transduction. Furthermore, new pharmaceutical agents moderating the intracellular and extracellular levels of sphingosine metabolites are showing promise in preclinical and clinical trials. In the present work, a quantitative assay relying on capillary electrophoresis with laser-induced fluorescence detection was developed to measure the interconversion of sphingosine and sphingosine-1-phosphate. The assay was demonstrated to be capable of determining the in vitro activity of both kinase and phosphatase using purified enzymes. The KM of sphingosine kinase for its fluorescently labeled substrate was 38 +/- 18 microM with a Vmax of 0.4 +/- 0.2 microM/min and a kcat of 3900 s-1. Pharmacologic inhibition of sphingosine kinase in a concentration-dependent manner was also demonstrated. Moreover, the fluorescent substrate was shown to be readily taken up by mammalian cells making it possible to study the endogenous activity of sphingosine kinase activity in living cells. The method was readily adaptable to the use of either bulk cell lysates or very small numbers of intact cells. This new methodology provides enhancements over standard methods in sensitivity, quantification, and manpower for both in vitro and cell-based assays.
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Affiliation(s)
- Katherine J Lee
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA
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Borland LM, Kottegoda S, Phillips KS, Allbritton NL. Chemical analysis of single cells. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2008; 1:191-227. [PMID: 20636079 DOI: 10.1146/annurev.anchem.1.031207.113100] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Chemical analysis of single cells requires methods for quickly and quantitatively detecting a diverse array of analytes from extremely small volumes (femtoliters to nanoliters) with very high sensitivity and selectivity. Microelectrophoretic separations, using both traditional capillary electrophoresis and emerging microfluidic methods, are well suited for handling the unique size of single cells and limited numbers of intracellular molecules. Numerous analytes, ranging from small molecules such as amino acids and neurotransmitters to large proteins and subcellular organelles, have been quantified in single cells using microelectrophoretic separation techniques. Microseparation techniques, coupled to varying detection schemes including absorbance and fluorescence detection, electrochemical detection, and mass spectrometry, have allowed researchers to examine a number of processes inside single cells. This review also touches on a promising direction in single cell cytometry: the development of microfluidics for integrated cellular manipulation, chemical processing, and separation of cellular contents.
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Affiliation(s)
- Laura M Borland
- Department of Chemistry, University of North Carolina at Chapel Hill, 27599, USA
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