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Continuous differential impedance spectroscopy of single cells.

Malleo D, Nevill JT, Lee LP, Morgan H - Microfluid Nanofluidics (2009)

Bottom Line: Measurements are accomplished by recording the current from two closely-situated electrode pairs, one empty (reference) and one containing a cell.We demonstrate time-dependent measurement of single cell impedance produced in response to dynamic chemical perturbations.ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10404-009-0534-2) contains supplementary material, which is available to authorized users.

View Article: PubMed Central - PubMed

ABSTRACT
A device for continuous differential impedance analysis of single cells held by a hydrodynamic cell trapping is presented. Measurements are accomplished by recording the current from two closely-situated electrode pairs, one empty (reference) and one containing a cell. We demonstrate time-dependent measurement of single cell impedance produced in response to dynamic chemical perturbations. First, the system is used to assay the response of HeLa cells to the effects of the surfactant Tween, which reduces the impedance of the trapped cells in a concentration dependent way and is interpreted as gradual lysis of the cell membrane. Second, the effects of the bacterial pore-forming toxin, Streptolysin-O are measured: a transient exponential decay in the impedance is recorded as the cell membrane becomes increasingly permeable. The decay time constant is inversely proportional to toxin concentration (482, 150, and 30 s for 0.1, 1, and 10 kU/ml, respectively). ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10404-009-0534-2) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus

I Outline of the Finite Element Model (FEM) of a single cell in a trap site: A two-dimensional model, which exploits the axial symmetry of the system, is meshed with 60,000 elements. The boundary conditions are indicated in the diagram. The medium surrounding the cell is ε = 78, σ = 1.6 S/m, the SU8 trap is ε = 5, σ = 0 S/m). The cytoplasm has permittivity ε = 70, and conductivity σ = 1.6 S/m, with membrane ε = 9, σ = 1 × 10−8 S/m and thickness = 5 nm. II Containment of current flux within su8 structures. Electrical potential and current density (streamlines) as for two-dimensional axi-symmetrical models of a cell immobilized between an electrode on the bottom and a large electrode on the top, with and without the SU8 structure. With the SU8 the current flux is well confined to the cell, therefore improving the sensitivity. (a) At frequencies below 10 kHz the electric potential drops across the ionic double layer. (b) Up to 100 kHz, the cell membrane effectively shields the cell from the electric field, so that the behavior is dominated by cell size and membrane properties. (c–d) Above 1 MHz the cell membrane is shunted and the impedance is dominated by the cell cytoplasm
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Fig3: I Outline of the Finite Element Model (FEM) of a single cell in a trap site: A two-dimensional model, which exploits the axial symmetry of the system, is meshed with 60,000 elements. The boundary conditions are indicated in the diagram. The medium surrounding the cell is ε = 78, σ = 1.6 S/m, the SU8 trap is ε = 5, σ = 0 S/m). The cytoplasm has permittivity ε = 70, and conductivity σ = 1.6 S/m, with membrane ε = 9, σ = 1 × 10−8 S/m and thickness = 5 nm. II Containment of current flux within su8 structures. Electrical potential and current density (streamlines) as for two-dimensional axi-symmetrical models of a cell immobilized between an electrode on the bottom and a large electrode on the top, with and without the SU8 structure. With the SU8 the current flux is well confined to the cell, therefore improving the sensitivity. (a) At frequencies below 10 kHz the electric potential drops across the ionic double layer. (b) Up to 100 kHz, the cell membrane effectively shields the cell from the electric field, so that the behavior is dominated by cell size and membrane properties. (c–d) Above 1 MHz the cell membrane is shunted and the impedance is dominated by the cell cytoplasm

Mentions: Finite element analysis simulations were performed in COMSOL Multiphysics v3.4 and MATLAB v7.5. A summary of the geometry and boundary conditions is given in Fig. 3I. The cell sits in PBS (permittivity ε = 78, conductivity σ = 1.6 S/m); the electrical properties of the SU8 trap are ε = 5, σ = 0 S/m, and the cell in the trap was modeled using a combination of the Maxwell’s mixture formula and a single-shelled model for cells. Briefly, according to the MMF:1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \varepsilon_{\text{trap}}^{*} = \varepsilon_{m}^{*} {\frac{{1 + 2\Upphi f_{\text{cm}} }}{{1 - \Upphi f_{\text{cm}} }}} $$\end{document}where2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ f_{\text{cm}} = {\frac{{\varepsilon_{\text{cell}}^{*} - \varepsilon_{m}^{*} }}{{\varepsilon_{\text{cell}}^{*} + 2\varepsilon_{m}^{*} }}} $$\end{document}Φ is the volume fraction (ratio of the cell volume to the detection volume), and in turn, the cell complex permittivity is defined as3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \varepsilon_{\text{cell}}^{*} = \varepsilon_{\text{mem}}^{*} {\frac{{v^{3} + 2{\frac{{\varepsilon_{\text{int}}^{*} - \varepsilon_{\text{mem}}^{*} }}{{\varepsilon_{\text{int}}^{*} + 2\varepsilon_{\text{mem}}^{*} }}}}}{{v^{3} + {\frac{{\varepsilon_{\text{int}}^{*} - \varepsilon_{\text{mem}}^{*} }}{{\varepsilon_{\text{int}}^{*} + 2\varepsilon_{\text{mem}}^{*} }}}}}} $$\end{document}where4\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ v = {\frac{{R_{\text{cell}} + d_{\text{mem}} }}{{R_{\text{cell}} }}} $$\end{document}The notation ε* is used to indicate complex permittivity, which can be expressed in terms of permittivity and conductivity:5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \varepsilon^{*} = \, \left( {\varepsilon_{0} \varepsilon_{r} - {\frac{j\sigma }{\omega }}} \right) $$\end{document}Fig. 3


Continuous differential impedance spectroscopy of single cells.

Malleo D, Nevill JT, Lee LP, Morgan H - Microfluid Nanofluidics (2009)

I Outline of the Finite Element Model (FEM) of a single cell in a trap site: A two-dimensional model, which exploits the axial symmetry of the system, is meshed with 60,000 elements. The boundary conditions are indicated in the diagram. The medium surrounding the cell is ε = 78, σ = 1.6 S/m, the SU8 trap is ε = 5, σ = 0 S/m). The cytoplasm has permittivity ε = 70, and conductivity σ = 1.6 S/m, with membrane ε = 9, σ = 1 × 10−8 S/m and thickness = 5 nm. II Containment of current flux within su8 structures. Electrical potential and current density (streamlines) as for two-dimensional axi-symmetrical models of a cell immobilized between an electrode on the bottom and a large electrode on the top, with and without the SU8 structure. With the SU8 the current flux is well confined to the cell, therefore improving the sensitivity. (a) At frequencies below 10 kHz the electric potential drops across the ionic double layer. (b) Up to 100 kHz, the cell membrane effectively shields the cell from the electric field, so that the behavior is dominated by cell size and membrane properties. (c–d) Above 1 MHz the cell membrane is shunted and the impedance is dominated by the cell cytoplasm
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Related In: Results  -  Collection

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Fig3: I Outline of the Finite Element Model (FEM) of a single cell in a trap site: A two-dimensional model, which exploits the axial symmetry of the system, is meshed with 60,000 elements. The boundary conditions are indicated in the diagram. The medium surrounding the cell is ε = 78, σ = 1.6 S/m, the SU8 trap is ε = 5, σ = 0 S/m). The cytoplasm has permittivity ε = 70, and conductivity σ = 1.6 S/m, with membrane ε = 9, σ = 1 × 10−8 S/m and thickness = 5 nm. II Containment of current flux within su8 structures. Electrical potential and current density (streamlines) as for two-dimensional axi-symmetrical models of a cell immobilized between an electrode on the bottom and a large electrode on the top, with and without the SU8 structure. With the SU8 the current flux is well confined to the cell, therefore improving the sensitivity. (a) At frequencies below 10 kHz the electric potential drops across the ionic double layer. (b) Up to 100 kHz, the cell membrane effectively shields the cell from the electric field, so that the behavior is dominated by cell size and membrane properties. (c–d) Above 1 MHz the cell membrane is shunted and the impedance is dominated by the cell cytoplasm
Mentions: Finite element analysis simulations were performed in COMSOL Multiphysics v3.4 and MATLAB v7.5. A summary of the geometry and boundary conditions is given in Fig. 3I. The cell sits in PBS (permittivity ε = 78, conductivity σ = 1.6 S/m); the electrical properties of the SU8 trap are ε = 5, σ = 0 S/m, and the cell in the trap was modeled using a combination of the Maxwell’s mixture formula and a single-shelled model for cells. Briefly, according to the MMF:1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \varepsilon_{\text{trap}}^{*} = \varepsilon_{m}^{*} {\frac{{1 + 2\Upphi f_{\text{cm}} }}{{1 - \Upphi f_{\text{cm}} }}} $$\end{document}where2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ f_{\text{cm}} = {\frac{{\varepsilon_{\text{cell}}^{*} - \varepsilon_{m}^{*} }}{{\varepsilon_{\text{cell}}^{*} + 2\varepsilon_{m}^{*} }}} $$\end{document}Φ is the volume fraction (ratio of the cell volume to the detection volume), and in turn, the cell complex permittivity is defined as3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \varepsilon_{\text{cell}}^{*} = \varepsilon_{\text{mem}}^{*} {\frac{{v^{3} + 2{\frac{{\varepsilon_{\text{int}}^{*} - \varepsilon_{\text{mem}}^{*} }}{{\varepsilon_{\text{int}}^{*} + 2\varepsilon_{\text{mem}}^{*} }}}}}{{v^{3} + {\frac{{\varepsilon_{\text{int}}^{*} - \varepsilon_{\text{mem}}^{*} }}{{\varepsilon_{\text{int}}^{*} + 2\varepsilon_{\text{mem}}^{*} }}}}}} $$\end{document}where4\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ v = {\frac{{R_{\text{cell}} + d_{\text{mem}} }}{{R_{\text{cell}} }}} $$\end{document}The notation ε* is used to indicate complex permittivity, which can be expressed in terms of permittivity and conductivity:5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \varepsilon^{*} = \, \left( {\varepsilon_{0} \varepsilon_{r} - {\frac{j\sigma }{\omega }}} \right) $$\end{document}Fig. 3

Bottom Line: Measurements are accomplished by recording the current from two closely-situated electrode pairs, one empty (reference) and one containing a cell.We demonstrate time-dependent measurement of single cell impedance produced in response to dynamic chemical perturbations.ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10404-009-0534-2) contains supplementary material, which is available to authorized users.

View Article: PubMed Central - PubMed

ABSTRACT
A device for continuous differential impedance analysis of single cells held by a hydrodynamic cell trapping is presented. Measurements are accomplished by recording the current from two closely-situated electrode pairs, one empty (reference) and one containing a cell. We demonstrate time-dependent measurement of single cell impedance produced in response to dynamic chemical perturbations. First, the system is used to assay the response of HeLa cells to the effects of the surfactant Tween, which reduces the impedance of the trapped cells in a concentration dependent way and is interpreted as gradual lysis of the cell membrane. Second, the effects of the bacterial pore-forming toxin, Streptolysin-O are measured: a transient exponential decay in the impedance is recorded as the cell membrane becomes increasingly permeable. The decay time constant is inversely proportional to toxin concentration (482, 150, and 30 s for 0.1, 1, and 10 kU/ml, respectively). ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10404-009-0534-2) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus