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Finite difference time domain (FDTD) simulation played a key role in the development of a unique exposure system that provides online monitoring of nonthermal radio frequency (RF) effects on catecholamine release from cultured adrenal medullary chromaffin cells, a well-characterized in vitro model of neural-type cells. While RF effects on cultured cells have been studied in the past, the new exposure system is believed to be the first that provides online monitoring of bioactive molecules secreted from cells – in this case, catecholamines. This is accomplished by placing the cells within a cell perfusion apparatus inside a waveguide. Continuous superfusion of the cells, where the perfusate that exits the cell perfusion chamber reaches an electrochemical detector, allows for both basal and stimulated catecholamine release to be assessed during RF exposure of the cells. A critical aspect of these experiments is the need to ensure maximum and consistent electromagnetic field exposure and specific absorption rate (SAR) for the cells within the waveguide. To achieve this goal, FDTD electromagnetic simulation software was used both to optimize the design of the waveguide-based exposure system and to characterize fully the electromagnetic fields during exposure of the cells to RF fields in the 0.75 to 1 GHz frequency range.

Biological Effects Of RF exposure – Thermal Versus Nonthermal

Many of the in vivo and in vitro biological effects of RF exposure that have been reported in the literature can be explained by tissue heating. On the other hand, some effects have been observed in the absence of heating, suggesting that RF fields can also cause effects by nonthermal mechanisms. For example, there may be RF electromagnetic field interactions with specific cellular membrane constituents, such as neurotransmitter receptors and ion channels. Investigating this intriguing possibility is at the forefront of efforts directed at developing novel bioelectromagnetic technologies.

Providing Online Measurement

Studies in which cultured cells are exposed to RF radiation to examine how a particular biological response is affected by the exposure typically employ offline measurement of the biological response being examined. This situation makes it difficult to determine the point at which changes occur, and in general reduces the amount of information that could be obtained from each experiment.

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•Technical Article: Simulation Aids First Online Monitoring Of RF Effects On Neuroendocrine Cells