Geometric effects in gas vesicle buckling under ultrasound
Acoustic reporter genes based on gas vesicles (GVs) have enabled the use of ultrasound to noninvasively visualize cellular function in vivo. The specific detection of GV signals relative to background acoustic scattering in tissues is facilitated 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 inverse cubic relation to the threshold buckling pressure, whereas length has no substantial effect. To complement these simulations, 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 fundamental 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.
Additional InformationThe authors are grateful to Ngozi A. Eze for the helpful editorial comments. The authors are also grateful to Dr. Di Wu for insightful discussions and input. This research was supported by the National Institutes of Health grant R01-EB018975. Related research in the Shapiro lab is supported by the Packard Foundation, The Pew Charitable Trusts, and the Chan Zuckerberg Initiative. Cryo-EM was performed at the Beckman Institute Resource Center for Transmission Electron Microscopy at Caltech. M.G.S. is an investigator of the Howard Hughes Medical Institute (HHMI). This article is subject to HHMI's Open Access to Publications policy. HHMI Investigators have previously granted a nonexclusive CC BY 4.0 license to the public and a sublicensable license to HHMI in their research articles. Pursuant to those licenses, the author-accepted manuscript of this article can be made freely available under a CC BY 4.0 license immediately upon publication.
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© 2022 Biophysical Society. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
H.S., Y.Y., P.D., and M.G.S. conceived and designed the study and wrote and edited the manuscript. H.S. and E.M. developed the computational models, performed the simulations, and analyzed the simulation data. Y.Y., P.D., Z.J., and D.M. conducted in vitro experiments and analyzed the experimental data. N.N.N. was involved in planning experiments and data analysis. M.G.S., M.O., and G.J.J. supervised the research. All authors read, edited, and confirmed the content of the manuscript.