BPS2026 – Live-cell compatible expansion via hydrogels on a tensile iris-stretcher

Mechanical forces are critical regulators of cell behavior, yet current methods to stretch or compress live cells remain limited. Uniaxial and biaxial stretch chambers, as well as flexible culture plates, have little ability to adjust strain direction or apply larger strain magnitudes, above those which are physiologically relevant. The directional and range limitations restrict investigations regarding cell behavior in dynamically changing mechanical environments. To overcome these limitations, we develop and used a tensile-force iris-expansion device coupled with a highly-stretchable double network alginate-acrylamide hydrogel that supports live-cell growth. Designed for tensile expansion microscopy (tensile ExM), the iris-device enables 1) continuous, stepwise, and reversible modulation of global strain in the xy-plane, providing precise temporal control over substrate deformation, 2) maintains cell viability, and 3) allows real-time monitoring of higher spatial resolution and dynamic live cell processes on an optical microscope. The iris expansion device has further been outfitted with strain gauges along the nine stretcher arms to quantify the applied forces. We demonstrate the utility of the iris device through HeLa cells cultured on top of the hydrogel and apply controlled stepwise expansion and contractions. Internal fluorescent reporters for microtubules, cellular membrane, and cytosol revealed reproducible cellular responses to dynamic tensile stress both at physiological (10–20% periodic strain at 1 Hz over hours) and extreme tensile ExM (1000% single step strain within 1 s) ranges. Beyond proof-of-concept, our iris-expansion device provides a versatile and accessible tool within the mechanobiology field for probing and imaging cell behavior under various mechanical cues.