The passive electrical properties of biological systems: their significance in physiology, biophysics and biotechnology

Pethig, Ronald; Kell, Douglas B.

doi:10.1088/0031-9155/32/8/001

Cited by 734 publications

(459 citation statements)

References 175 publications

(95 reference statements)

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“…The cytoplasm will exhibit dispersions related to the presence of small bodies ͑e.g., mitochondria, protein structures͒ and solvated proteins, amino acids, and other biopolymers. 21,22 Such dielectric dispersions, when incorporated into the multishell model, introduce relatively small modifications to the overall DEP spectrum and can slightly influence the high-frequency DEP cross-over frequency f hxo . 23 Particles generally carry a net charge associated with the presence of charged polymers and/or ionizable acidic and basic groups on their surfaces.…”

Section: ͑15͒mentioning

confidence: 99%

Review Article—Dielectrophoresis: Status of the theory, technology, and applications

2010

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A review is presented of the present status of the theory, the developed technology and the current applications of dielectrophoresis ͑DEP͒. Over the past 10 years around 2000 publications have addressed these three aspects, and current trends suggest that the theory and technology have matured sufficiently for most effort to now be directed towards applying DEP to unmet needs in such areas as biosensors, cell therapeutics, drug discovery, medical diagnostics, microfluidics, nanoassembly, and particle filtration. The dipole approximation to describe the DEP force acting on a particle subjected to a nonuniform electric field has evolved to include multipole contributions, the perturbing effects arising from interactions with other cells and boundary surfaces, and the influence of electrical double-layer polarizations that must be considered for nanoparticles. Theoretical modelling of the electric field gradients generated by different electrode designs has also reached an advanced state. Advances in the technology include the development of sophisticated electrode designs, along with the introduction of new materials ͑e.g., silicone polymers, dry film resist͒ and methods for fabricating the electrodes and microfluidics of DEP devices ͑photo and electron beam lithography, laser ablation, thin film techniques, CMOS technology͒. Around three-quarters of the 300 or so scientific publications now being published each year on DEP are directed towards practical applications, and this is matched with an increasing number of patent applications. A summary of the US patents granted since January 2005 is given, along with an outline of the small number of perceived industrial applications ͑e.g., mineral separation, micropolishing, manipulation and dispensing of fluid droplets, manipulation and assembly of micro components͒. The technology has also advanced sufficiently for DEP to be used as a tool to manipulate nanoparticles ͑e.g., carbon nanotubes, nano wires, gold and metal oxide nanoparticles͒ for the fabrication of devices and sensors. Most efforts are now being directed towards biomedical applications, such as the spatial manipulation and selective separation/enrichment of target cells or bacteria, high-throughput molecular screening, biosensors, immunoassays, and the artificial engineering of three-dimensional cell constructs. DEP is able to manipulate and sort cells without the need for biochemical labels or other bioengineered tags, and without contact to any surfaces. This opens up potentially important applications of DEP as a tool to address an unmet need in stem cell research and therapy.

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Section: ͑15͒mentioning

confidence: 99%

Review Article—Dielectrophoresis: Status of the theory, technology, and applications

2010

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“…The detailed mathematical description of DS has been discussed in the literature and in textbooks [Arnold, 2001, Coster et al, 1996, Davey et al, 1993a, Davey et al, 1993b, Marszalek et al, 1990, Pethig and Kell, 1987, Barsoukov and Macdonald, 2005]. An overview is given below.…”

Section: Mathematical Description Of Dielectric Spectroscopymentioning

confidence: 99%

Process control in cell culture technology using dielectric spectroscopy

Justice¹,

Brix

Freimark³

et al. 2011

Biotechnology Advances

107

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“…[33][34][35][36] The permittivity of a cell suspension can be easily measured because a characteristic fall in permittivity, the b-dispersion (Figure 1), occurs with increasing frequency. The b-dispersion is caused by the polarization of cell membranes.…”

Section: Theoretical Backgroundmentioning

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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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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The passive electrical properties of biological systems: their significance in physiology, biophysics and biotechnology

Cited by 734 publications

References 175 publications

Review Article—Dielectrophoresis: Status of the theory, technology, and applications

Review Article—Dielectrophoresis: Status of the theory, technology, and applications

Process control in cell culture technology using dielectric spectroscopy

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

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