Direct Observation and Measurement of Membrane Tension in Xenopus laevis Animal Cap Explants Using the Mechanosensitive Dye, Flipper-TR.

Mechanical forces play a critical role in shaping tissue architecture and influencing cell behavior during development and disease. Plasma membrane tension acts as a key mechanosensitive parameter, linking external forces to intracellular signaling through mechanotransduction. While traditional methods for measuring membrane tension, such as atomic force microscopy and optical tweezers, are invasive and challenging to apply to whole tissues, the mechanosensitive dye Flipper-TR offers a nondestructive optical approach to measure membrane tension using Fluorescence Lifetime Imaging Microscopy (FLIM). Here, we describe a protocol for measuring membrane tension in Xenopus laevis animal cap explants, extending Flipper-TR applications from cultured cells to intact embryonic tissues. The staining and imaging workflow is optimized to minimize phototoxicity and address challenges such as fluorescence polarization. Additionally, we detail an image processing pipeline to extract fluorescence lifetime data and infer membrane tension at cellular and tissue scales. This approach enables direct visualization of membrane tension dynamics in live tissues, providing a powerful tool for mechanobiology studies.