Studying the Impact of Microsystems on Cell Physiology

Microfluidics and related microtechnologies have led to the development of many new assay platforms for interrogating cells. Each of these platforms subjects cell to various stresses, but the effects of these platform stresses on cell physiology have not been systematically examined. For instance, we and others have developed many technologies for manipulating cells with electric fields via dielectrophoresis (DEP). Although researchers have studied the gross effects of DEP on cell viability and growth, little is known about how electric fields couple through intracellular signaling pathways to alter cell physiology. Electric fields used for DEP can not only stress cells via temperatures rise due to Joule heating of the culture media or via reactive species formed at the electrode-electrolyte interface, but can also potentially directly interact with cells (e.g., via voltage-gated ion channels). Consequently, it is imperative that we understand the effects of DEP manipulation on cell physiology to determine whether DEP manipulation itself can alter particular phenotypes of interest and confound downstream biological assays. To this end, we have developed a microfabricated, high-content screening platform that can apply a large number of different electrical stimuli to cells and then monitor the molecular effects of those stimuli using automated fluorescence microscopy.

The platform consists of three components: (1) a stress-reporter cell line that reports on activation of the cell’s stress response pathway (via GFP under the control of a heat shock element promoter) and constitutively expresses dsRed to cell identification; (2) a microfluidic platform consisting of fifteen independently addressable chambers allowing application (via computer) of a number of different stimulus conditions to cells; (3) automated microscopy and algorithms to quantify stress response at a single-cell level across each stimulus condition.

With this system, we have been able to create comprehensive maps linking field exposure to stress response. These maps will provide researchers with guidelines for designing DEP-based microsystems. We also note that because the stress response pathway responds to a number of different stressors, our reporter cell line has the potential to be used to ascertain stress in many types of microfluidic systems.