Geometric Effects in Gas Vesicle Buckling under Ultrasound

Acoustic reporter genes based on gas vesicles (GVs) have enabled the use of ultrasound to noninvasively visu-alize cellular function in vivo. The specific detection of GV signals relative to background acoustic scattering in tissues is facil-itated by nonlinear ultrasound imaging techniques taking advantage of the sonomechanical buckling of GVs. However, the effect of geometry on the buckling behavior of GVs under exposure to ultrasound has not been studied. To understand such geometric effects, we developed computational models of GVs of various lengths and diameters and used finite element simulations to predict their threshold buckling pressures and postbuckling deformations. We demonstrated that the GV diameter has an in-verse cubic relation to the threshold buckling pressure, whereas length has no substantial effect. To complement these simu-lations, we experimentally probed the effect of geometry on the mechanical properties of GVs and the corresponding nonlinear ultrasound signals. The results of these experiments corroborate our computational predictions. This study provides funda-mental insights into how geometry affects the sonomechanical properties of GVs, which, in turn, can inform further engineering of these nanostructures for high-contrast, nonlinear ultrasound imaging.