The dielectric properties of biological cells at radiofrequencies: applications in biotechnology

Markx, Gerard H.; Davey, Christopher L.

doi:10.1016/s0141-0229(99)00008-3

Cited by 283 publications

(193 citation statements)

References 84 publications

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“…Hydrated ions try to move in the direction of the electrical field and they transfer energy by this movement (Nyfors and Vainikainen 1989;Ohlsson 1989). Polarization can be due to various effects ranging from charge accumulation at the surfaces between materials with different electrical properties (interfacial polarization) to dipole orientation and other effects (Markx and Davey 1999).…”

Section: Polarization Of Dielectricsmentioning

confidence: 99%

Measurement techniques and application of electrical properties for nondestructive quality evaluation of foods—a review

et al. 2011

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Non-destructive systems are recent trends for quality evaluation of fruits and vegetables. Information on post-harvest variations in electrical properties is needed to develop new instruments for this purpose. Electrical properties are finding increasing application in agriculture and food processing industries. Knowledge of dielectric properties of foods as a function of moisture content and temperature is essential in the design and control of drying systems. As simple, rapid and non-destructive measuring techniques, dielectric spectroscopy provides information about the dielectric response of materials to electromagnetic field. Electrical properties of agricultural materials have been of interest for many years. The interest in dielectric properties of materials has historically been associated with the design of electrical equipment. This review paper covers theoretical aspects of different electrical properties, their measurement techniques, applications of dielectric properties in agriculture/food processing sector and potential applications of thermal imaging (TI) for quality and safety assessment in food processing. The values of dielectric properties of a number of products including food grains, fruits and vegetables, and meat and meat products are presented in table form. This comprehensive coverage will be useful for academic, scientific and industrial community in treating and applying the facts in developing/testing new processes and products based on electromagnetic energy application.Keywords Electrical properties . Non-destructive . Measuring techniques . Dielectric constant . Loss factor . Thermal imaging technique . Food quality evaluationThe material investigation and moisture measurement using electromagnetic waves in wide spectrum serve for quality control and improvement in many branches like industry, forest and wood-working industry, civil engineering, agriculture, commerce and also foods e.g. for quality evaluation of meat, fruits, coffee etc (Hlavacova 2003; Venkatesh and Raghavan 2004). Non-destructive evaluation of quality based on constituents of fruits and vegetables has been successfully used (Chen et al. 1999;Jha et al. 2001;Kawano 1998). Electrical characteristics of agricultural materials have been of interest for many years (Nelson 2006) and are utilized in many areas of human activities. Techniques for non-destructive determination of quality and related characteristics of agricultural products are helpful to producers, handlers and processors . Permittivity and moisture can be closely correlated when water content is high. Knowledge of dielectric properties in partially frozen material is critical in determining the rates and uniformity of heating in microwave thawing. Electrical properties are important in processing foods with pulsed electric fields, ohmic heating, induction heating, radio frequency, and microwave heating. These properties are also useful in the detection of processing conditions or the quality of foods (Barbosa-Canovas et al. 2006). Considering ...

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Section: Polarization Of Dielectricsmentioning

confidence: 99%

Measurement techniques and application of electrical properties for nondestructive quality evaluation of foods—a review

et al. 2011

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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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“…A body of literature exists that has both measured and modelled the electrical changes in cells and tissue both in vivo and in vitro, as well as provided correlations between electrical properties and cell types; this work has been summarized previously [6][7][8][9][10][11] . From an electrical perspective, a cell can be represented as an ion-rich conductive centre (cytoplasm) embedded in an ion-rich conductive medium (extracellular fluid), separated by a relatively non-conductive barrier (cell membrane).…”

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Impedance sensing device enables early detection of pressure ulcers in vivo

et al. 2015

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When pressure is applied to a localized area of the body for an extended time, the resulting loss of blood flow and subsequent reperfusion to the tissue causes cell death and a pressure ulcer develops. Preventing pressure ulcers is challenging because the combination of pressure and time that results in tissue damage varies widely between patients, and the underlying damage is often severe by the time a surface wound becomes visible. Currently, no method exists to detect early tissue damage and enable intervention. Here we demonstrate a flexible, electronic device that non-invasively maps pressure-induced tissue damage, even when such damage cannot be visually observed. Using impedance spectroscopy across flexible electrode arrays in vivo on a rat model, we find that impedance is robustly correlated with tissue health across multiple animals and wound types. Our results demonstrate the feasibility of an automated, non-invasive 'smart bandage' for early detection of pressure ulcers.

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The dielectric properties of biological cells at radiofrequencies: applications in biotechnology

Cited by 283 publications

References 84 publications

Measurement techniques and application of electrical properties for nondestructive quality evaluation of foods—a review

Measurement techniques and application of electrical properties for nondestructive quality evaluation of foods—a review

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

Impedance sensing device enables early detection of pressure ulcers in vivo

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