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Rapid Single-cell Measurement of Transient Transmembrane Water Flow under Osmotic Gradient
Hong Jiang1, Jinnawat Jongkhumkrong2, Y J Chao1
1Department of Mechanical Engineering, University of South Carolina, Columbia, SC, 29208, USA.
The Journal of Membrane Biology
|February 25, 2026
Summary
Researchers developed a new optical method, Flow-Induced Fluorescence Increase Velocimetry (FIFIV), to measure water transport through aquaporins (AQPs) in single cells. This technique offers high sensitivity for studying AQP regulation in various conditions.
Area of Science:
- Biophysics
- Cell Biology
- Optical Imaging
Background:
- Aquaporins (AQPs) facilitate water transport across cell membranes.
- Understanding AQP gating and regulation is crucial but limited by current measurement techniques.
- Existing methods lack the spatiotemporal resolution and sensitivity for real-time water flow analysis.
Purpose of the Study:
- To introduce a novel optical technique for direct, real-time monitoring of transmembrane water flow.
- To enable sensitive measurement of water transport through individual aquaporins in single cells.
- To provide a new tool for investigating aquaporin gating and regulatory mechanisms.
Main Methods:
- Development of Flow-Induced Fluorescence Increase Velocimetry (FIFIV) based on Laser-Induced Fluorescence Photobleaching Anemometry (LIFPA).
- Utilizing fluorescent dyes to label cytoplasm in single adherent MDA-MB-231 breast cancer cells.
- Applying localized hypotonic stimulation to induce osmotic pressure gradients and measure cytoplasmic flow.
Main Results:
- Demonstrated detection of extremely low transmembrane water flow (approx. 1 μm/s) in real-time.
- Achieved single-cell sensitivity and temporal resolution comparable to electrophysiological ion flux measurements.
- Successfully circumvented limitations of traditional volume-based osmotic permeability assays.
Conclusions:
- FIFIV offers a novel optical approach for probing water-flow-induced intracellular dynamics.
- The technique provides a foundation for future studies on aquaporin regulation and gating.
- Potential applications in physiopathological research and drug discovery for aquaporin-related conditions.
