Microwave Devices for Biosensors and Single Cell Dielectric Spectroscopy

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Studying the physiology of biological cells and monitoring their response to different stimuli or drugs is essential in bioprocess and biomedical research. Many currently used instruments for cellular analysis utilize chemical markers, sophisticated equipment and time-consuming preparation techniques. Microfluidic devices employing dielectric analysis are a promising alternative as they are label-free, can be miniaturized and use nanoliter fluid volumes. The objectives of the proposed research program is to develop microfluidics devices integrated with microwave dielectric sensors and actuators for in-flow single cell analysis, use these to study cell response to different types of stress, develop new cell dielectric models, and relate cell dielectric properties to physiology. Tissues, cells and other biomedia have unique dielectric properties that can be used to provide a wealth of information, such as a cell's growth phase, whether it is healthy or cancerous, or if drug-induced changes have occurred. Most current methods for measuring single cell dielectric properties employ impedance or dielectrophoresis at low frequencies using only one or two frequencies. Much additional information can be gained by measuring the complete spectrum and extending this to microwave frequencies, a regime where fields can penetrate the cell interior and the polarizability of large molecules can be detected. Dielectric spectroscopy of single cells is extremely difficult due to their small size. We will explore new microwave dielectrophoresis sensing techniques to measure single cells over a wide frequency spectrum and use this to develop multi-parameter cell dielectric models. Microfliudic devices will be used to study cell response to starvation, heat shock and microwave electroporation (EP). Detection of starvation-induced apoptosis is important in biopharmaceutical bioprocessing and biomedical research. Dielectric changes to cells under starvation will be related to cell physiology and the developed cell models will be used to understand bulk-suspension dielectric measurements. Heat shock and exposure to high-intensity electric fields (inducing EP) can permanently or temporarily permeabilize cell membranes. This is employed for transfection, enhancing drug uptake in cancer therapy, inducing apoptosis, or in the extreme case, lysis. Microfluidic devices will be developed to apply and simultaneously measure the dielectric changes to cells associated with these two stressors. Of particular interest is CW microwave EP, where we will explore use of low-intensity fields to induce EP effects. The outcomes of the research will be new microfluidic single cell dielectric spectroscopy tools integrated with stimulus capabilities, providing new non-invasive label-free single cell analysis instruments. The research program will provide both theoretical and experimental training to highly qualified personnel in an interdisciplinary environment.