Electrical Properties of Tissue and Cell Suspensions

Schwan, Herman P.

doi:10.1016/b978-1-4832-3111-2.50008-0

Cited by 1,390 publications

(822 citation statements)

References 102 publications

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“…The equation for f C changes for situations of low cellular viability or high membrane conductivity. 37,38 In this study, this relationship could be neglected for the most important part of our results because viability remained high when important changes in f C occurred.…”

Section: Theoretical Backgroundmentioning

confidence: 95%

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Multifrequency permittivity measurements enable on‐line monitoring of changes in intracellular conductivity due to nutrient limitations during batch cultivations of CHO cells

Ansorge

Esteban

Schmid

2009

Biotechnology Progress

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Lab and pilot scale batch cultivations of a CHO K1/dhfr À host cell line were conducted to evaluate on-line multifrequency permittivity measurements as a process monitoring tool. The b-dispersion parameters such as the characteristic frequency (f C ) and the permittivity increment (De max ) were calculated on-line from the permittivity spectra. The dual-frequency permittivity signal correlated well with the off-line measured biovolume and the viable cell density. A significant drop in permittivity was monitored at the transition from exponential growth to a phase with reduced growth rate. Although not reflected in off-line biovolume measurements, this decrease coincided with a drop in OUR and was probably caused by the depletion of glutamine and a metabolic shift occurring at the same time. Sudden changes in cell density, cell size, viability, capacitance per membrane area (C M ), and effects caused by medium conductivity (r m ) could be excluded as reasons for the decrease in permittivity. After analysis of the process data, a drop in f C as a result of a fall in intracellular conductivity (r i ) was identified as responsible for the observed changes in the dual-frequency permittivity signal. It is hypothesized that the b-dispersion parameter f C is indicative of changes in nutrient availability that have an impact on intracellular conductivity r i . On-line permittivity measurements consequently not only reflect the biovolume but also the physiological state of mammalian cell cultures. These findings should pave the way for a better understanding of the intracellular state of cells and render permittivity measurements an important tool in process development and control.

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Section: Theoretical Backgroundmentioning

confidence: 95%

“…1). 37 A constant De Fogale response can consequently be observed when the cell radius is changing at a constant biovolume. De Fogale is henceforth linear to the biovolume even in the case of cell size changes.…”

Section: Metabolite and Product Analysesmentioning

confidence: 99%

Multifrequency permittivity measurements enable on‐line monitoring of changes in intracellular conductivity due to nutrient limitations during batch cultivations of CHO cells

Ansorge

Esteban

Schmid

2009

Biotechnology Progress

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“…However, EIM is distinctly different since it focuses on measurement of the impedance in relatively restricted regions of muscle (Rutkove et al, 2002), rather than on large areas of the body. In general, bioimpedancebased methods rely on the concept that tissues can be modeled as networks of resistors and capacitors (Schwan, 1957). In the case of EIM, the lipid bilayers of the muscle cell membranes act as the capacitors, the source of the reactance (X) of the network, and the intra-and extracellular fluids act as the resistors, the source of its resistance (R).…”

Section: Introductionmentioning

confidence: 99%

Electrical impedance myography to assess outcome in amyotrophic lateral sclerosis clinical trials

Rutkove

Zhang

Schoenfeld

et al. 2007

Clinical Neurophysiology

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Objective-Standard outcome measures used for amyotrophic lateral sclerosis (ALS) clinical trials, including the ALS Functional Rating Scale-revised (ALSFRS-R), maximal voluntary isometric contraction testing (MVICT), and manual muscle testing (MMT) are limited in their ability to detect subtle disease progression. Electrical impedance myography (EIM) is a new non-invasive technique that provides quantitative data on muscle health by measuring localized tissue impedance. This study investigates whether EIM could provide a new outcome measure for use in ALS clinical trials work.Methods-Fifteen ALS patients underwent repeated EIM measurements of one or more muscles over a period of up to 18 months and the primary outcome variable, θ z-max , measured. The θ z-max megascore was then calculated using the same approach as has been applied in the past for MVICT. This and the MMT data were then used to assess each measure's statistical power to detect a given effect on disease progression in a hypothetical planned clinical therapeutic trial.Results-θ z-max showed a mean decline of about 21% for the test period, averaged across all patients and all tested muscles. The θ z-max megascore had a power of 73% to detect a 10% treatment effect in our planned hypothetical trial, as compared to a 28% power for MMT. These results also compared favorably to historical data for ALSFRS-R and MVICT arm megascore from the trial of celecoxib in ALS, where both measures had only a 23% power to detect the same 10% treatment effect.Conclusions-The θ z-max megascore may provide a powerful new outcome measure for ALS clinical trials.Significance-The application of EIM to future ALS trials may allow for smaller, faster studies with an improved ability to detect subtle treatment effects.

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“…84,85 Early work on cell electrical measurements dates back to the 1910s, [86][87][88] the foundation for interpreting the electrical properties of cells, where the cell is modeled as a spherical cytoplasm surrounded by a thin dielectric membrane. 89,90 Generally, the electrical properties of a plasma membrane are affected by the membrane morphology, lipid bilayer composition and thickness, and embedded proteins. [91][92][93] Electrical properties of the cytoplasm are influenced by the intracellular structures and physiological conditions (e.g., nucleus-to-cytoplasm ratio and ion concentrations inside the cell).…”

Section: Electrical Characterization Techniquesmentioning

confidence: 99%

Recent advances in microfluidic techniques for single-cell biophysical characterization

et al. 2013

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Electrical Properties of Tissue and Cell Suspensions

Cited by 1,390 publications

References 102 publications

Multifrequency permittivity measurements enable on‐line monitoring of changes in intracellular conductivity due to nutrient limitations during batch cultivations of CHO cells

Multifrequency permittivity measurements enable on‐line monitoring of changes in intracellular conductivity due to nutrient limitations during batch cultivations of CHO cells

Electrical impedance myography to assess outcome in amyotrophic lateral sclerosis clinical trials

Recent advances in microfluidic techniques for single-cell biophysical characterization

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