Biology subjects

Chien, A. J.

Publications and source records attributed to Chien, A. J..

3 recordsLinked to original sources

bioRxiv2026

Membrane-resolved epithelial electrophysiology revealed using extracellular electrochemical impedance spectroscopy (EEIS)

Conventional extracellular epithelial electrophysiology measurements report only bulk transepithelial resistance and capacitance, obscuring the distinct electrical properties of the apical and basolateral membranes. This limitation hinders research of epithelial diseases where dysfunction originates at a specific membrane domain--apical or basolateral--for example in cystic fibrosis or toxin-mediated airway injury. Here we present the extracellular electrochemical impedance spectroscopy (EEIS) technique that extracts membrane-specific electrophysiology by fitting impedance spectra to a two-resistor, two-capacitor (RCRC) model. Using human bronchiolar epithelial monolayers (16HBE), we show a correlation between the electrical time constants of the circuit ({tau}1 = R1 {middle dot} C1,{tau} 2 = R2 {middle dot} C2) and changes in ion permeability of the basolateral and apical membranes. Experimentally, we show that blocking with 5-10 {micro}M GlyH-101 (i.e. decreasing apical membrane permeability), after 10 {micro}M forskolin activation elicits dose dependent{tau} 2 responses that are over 50% larger than{tau} 1and 6-7 minutes faster, whereas 10 {micro}M nystatin (i.e. increasing basolateral membrane permeability) produces{tau} 1 responses 21-25% larger than{tau} 2 and approximately 2 minutes faster. For cystic fibrosis epithelia, we find that elexacaftor/tezacaftor/ivacaftor (ETI) restores the apical membrane electrical response, resulting in a significant 84% higher{tau} 2 than{tau} 1 within the first 10 minutes. It also exhibits a greater than 8 min faster{tau} 2 response relative to{tau} 1 following 10 {micro}M GlyH-101 blocking (i.e., decreasing apical membrane permeability). These results demonstrate that EEIS enables rapid, quantitative, and biologically relevant measurement of apical and basolateral membrane properties in 16HBE epithelia. By providing membrane-specific resolution without the experimental challenges of intracellular electrodes, EEIS establishes a general framework for rapid, membrane-resolved electrophysiology with implications for therapeutic screening.

bioengineering↗

bioRxiv2026

Sub-second Extracellular Impedance Measurement of Epithelial Cell Monolayers using Step Excitations and Time-domain Analysis

Extracellular electrochemical impedance spectroscopy (EIS) is emerging as a powerful technique in in vitro epithelial research, offering quantitative insights into barrier integrity, morphology, and apical-basolateral polarity noninvasively through metrics such as transepithelial electrical resistance (TER/TEER), transepithelial capacitance (TEC), and membrane ratio (), respectively. However, due to the broad range of frequencies probed, EIS typically requires tens of seconds per measurement, limiting its ability to capture more rapid biological phenomena. We present Time-domain Epithelial Impedance Measurement (TEIM), a method for sub-second extracellular impedance measurements of epithelial cell monolayers based on step (Heaviside function) current excitation and time-domain analysis of the voltage transients, without the need for Fourier transforms. We experimentally demonstrate TEIM measuring TER, TEC, , and model-derived impedance spectrum at [~]0.3 s sampling rate, which represents a 100- fold improvement in time resolution compared with traditional EIS. The accuracy and precision of TEIM were benchmarked against EIS on both electrical circuits and epithelial cell monolayers of immortalized Human Bronchial Epithelial (16HBE) and Human Colorectal Adenocarcinoma (Caco-2) (n = 3 for each), and average percent errors for TER, TEC, and ranged from 0.17-3.55%, 1.13-8.96%, and 0.59-26.35%, respectively. Application of TEIM to monitor Caco-2 responses to saponin, a quick-acting pore-forming detergent, revealed smoothly gated double-exponential transient TER and TEC dynamics that were too rapid to be adequately captured previously using EIS. Overall, TEIM enables electrophysiology studies of rapid changes in epithelial cell culture models and possibly more complex in vitro models, holding promise for future applications in areas such as disease modeling, therapeutic development, and beyond.

bioengineering↗

bioRxiv2025

Method for Extracellular Electrochemical Impedance Spectroscopy on Epithelia

Epithelial tissues form barriers to the flow of ions, nutrients, waste products, bacteria, and viruses. The conventional electrophysiology measurement of transepithelial resistance (TER) can quantify epithelial barrier integrity, but does not capture all the electrical behavior of the tissue or provide insight into membrane specific properties. Electrochemical impedance spectroscopy, in addition to measurement of TER, enables measurement of transepithelial capacitance (TEC) and a ratio of electrical time constants for the tissue, which we term membrane ratio. This protocol describes how to perform galvanostatic electrochemical impedance spectroscopy on epithelia using commercially available cell culture inserts and chambers, detailing the apparatus, electrical signal, fitting techniques, and error quantification. The measurement can be performed in approximately one minute using instrumentation capable of galvanostatic sinusoidal signal processing (4 A amplitude, 2 Hz-50 kHz). All fits to the model have less than 10 {Omega} mean absolute error, revealing repeatable values distinct for each cell type. On representative retinal pigment (n=3) and bronchiolar epithelial samples (n=4), we measured TER 500-667 {Omega}.cm2 and 955-1034 {Omega}.cm2, within the expected range, TEC 3.65-4.10 F/cm2 and 1.07-1.10 F/cm2, and membrane ratios 18-22 and 1.9-2.2, respectively.

bioengineering↗