Dielectric Response of Single Cells to Applied Stress
Dielectric spectroscopy has become important as a new label-free and non-invasive modality for investigating biological phenomena at the cellular and molecular level. The approach is amenable to implementation in an all-electronic microfluidic platform and is thus a viable avenue towards simple portable diagnostic instrumentation. Of interest in many applications is knowledge of a cell’s electrophysiology change on very short to very long time scales when different stressors are applied. Also of importance is how physiological changes (influx/efflux of molecules, cytosol ionic concentration or membrane morphology) are related to the measured dielectric response of the cell. In this talk we discuss biosensing techniques that can provide detailed wideband dielectric characterization of single cells over varying time scales. In particular we describe an in-flow dielectrophoresis cytometry approach for rapidly monitoring the dynamic dielectric change of single cells. The approach employs a microfluidic device capable of simultaneous microwave detection and dielectrophoresis actuation as well as electric field exposure of cells. We will focus on the time-dependent response of cells under stress due to nutrient deprivation, drugs and exposure to high intensity pulsed electric fields. The correlation between the dielectric response and cell membrane impedance, cytosol conductivity and effective complex permittivity and the time constants of their changes will be discussed.