Electrial biosensing - real-time impedance measurements across cells grown on surface electrodes for the study of cell migration and behavior
Live/dead staining showing viable cells grown on surface electrode.
Bright-field images of MCF-7 (transfected with vector, ZEB1, or ZEB2) cells grown electrodes for an in situ wound healing assay study.
Real-time impedance (resistance component shown here) measurement across cells as they recover into a full monolayer after generating a wound.
Timelapse image showing cell monolayer recovery following in situ formation of a "wound" by lethal electroporation.
Cancer cells originating from the epithelium evolve into invasive and metastatic cells through the acquisition of genetic mutations that lead to a highly motile mesenchymal phenotype. The ZEB family of transcription factors potentially plays a key role in regulating migration of MCF-7 breast cancer cells through the repression of cell-cell adhesion junction protein, E-cadherin. Although the migration potential of cells can be assessed with a "wound healing" assay, reproducibility is limited by semi-quantitative image analysis of the wound closure and variability in the mechanically disrupted area in the cell monolayer. Electrical Cell-substrate Impedance Sensing (ECIS) provides an improvement over traditional wound healing assay by providing real-time, noninvasive measurement of in vitro cell behavior as well as reproducible electrical wounding of the cell monolayer. A 1 µA, 4kHz AC current applied across single surface electrodes (250-µm diameter) provided monitoring capability as MCF-7 cells, transfected to over-express ZEB1, ZEB2 or vector, attach and spread on the substrate. The same surface electrode is also used to lethally electroporate cells in the current path by permanently damaging plasma membranes directly above the surface electrode, clearing a well-defined circular area 250 µm in diameter. Based on measured resistance values at 1 kHz, the time to recovery for MCF-7+ZEB1, MCF-7+ZEB2, and MCF-7+vector cells was 9, 10, and 12 hrs, respectively. The ECIS results agreed with traditional, image-based evaluations from scratch-based wound healing assays (migration rate: 10.2 µm/hr (MCF-7+ZEB1), 9.0 µm/hr (MCF-7+ZEB2), and 7.9 µm/hr (MCF-7+vector)). Taken together, the data indicates that ZEB family of proteins play a positive role in inducing MCF-7 cell migration and that ECIS provides a robust and reproducible method for assessing the migration potential of cells.