Abstract: 

Epithelial tissues serve as critical barriers that regulate the transport of ions, nutrients, waste products, and pathogens. Electrophysiological measurements offer valuable insights into epithelial barrier function by capturing electrical properties linked to permeability—essential for studying both healthy and diseased states, evaluating therapeutic interventions, and ensuring quality control in in vitro models. Transepithelial resistance (TER) is widely used as the gold standard to assess epithelial maturity and barrier integrity; however, TER values reported in the literature often vary significantly, even under similar conditions, and rely on oversimplified assumptions. Electrochemical impedance spectroscopy (EIS/ECIS), though less commonly employed, provides a richer understanding of epithelial transport dynamics, membrane-specific properties, and more precise assessments of membrane integrity. Beyond TER, EIS enables measurement of transepithelial capacitance (TEC) and a novel parameter we define as the membrane ratio—a ratio of electrical time constants reflective of cellular and subcellular dynamics. We apply this technique to investigate rapid immune responses, including changes in permeability and capacitance associated with neutrophil migration under hyperglycemic conditions, as well as immune responses triggered by the bacterial component, lipopolysaccharide (LPS).