Microwave dielectric spectroscopy as an analytic technique of electroporated cells
Résumé
Microwave dielectric spectroscopy is under development for decades. It consists incharacterizing whether solid, liquid or gaseous materials with their dielectric properties in this specificfrequency range. The technique is intrinsically non-destructive, rapid and without requiring a directcontact with the sample under test, which made it particularly attractive for its exploitation in manyapplicative domains, such as the detection of pipeline in the soil, coal in canalizations, as well asmoisture sensing in agriculture areas, wood industry or for food quality assessments (1)-(3). However,based on cumbersome microwave equipment, microwave dielectric spectroscopy has been for longlimited to macroscale developments.With the advent of the micro and nanotechnologies, new applicative opportunities haveopened up in chemistry, biology and medicine notably. Due to the resonant frequency of the watermolecules in the microwave band, the technique is particularly sensitive to biological materials, whichnaturally exhibit a high-water content. Combined with the use and the manipulation of small liquidvolumes, this sensing technique has been successfully developed for molecular and cellular analysis(4)-(5). The technique has been applied to tissues, cells suspensions and down to individual cellsanalysis. It was also demonstrated for cell quantification, identification and the monitoring of biologicalprocesses, while cells were maintained in their traditional environment, their culture medium.Attractively for cellular investigations, the sensing technique is also non-invasive and label free. Andmore interestingly, due to the employed high frequency range, the electromagnetic fields may bypassthe capacitive cytoplasmic membrane and penetrate inside the cells, revealing quantitativeinformation related to the intracellular dielectric activity. This spectroscopic method consequentlyappears suitable to analyze internal variations of cells, which notably involve water moleculesinteraction modifications.To verify such an ability, different physical or chemical stimuli applied on various cell lines havebeen investigated. Among them is the application of millisecond pulsed electric fields at differentintensity levels on cell suspensions. Impact of such fields on the dielectric responses will be presentedat the single cell level, highlighting the characterization possibility of the microwave dielectricspectroscopy compare to a traditional gold standard technique.
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