The vibration behavior of submicron gas vesicles in response to acoustic excitation as determined via laser doppler vibrometry

Abstract

Gas vesicles (GVs) are remarkably stable nano-sized gas-filled protein shells proven effective in ultrasonic imaging. The many potential benefits of GVs arise from their strong gas equilibrium at a submicron size as produced by bacteria or algae, producing significant contrast in ultrasound imaging. The actual vibration behavior of GVs, including buckling and collapse, is poorly understood since the GVs are too small for observation methods of sufficient speed to produce details of the GV deformation during exposure to ultrasound. Traditional optical or acoustic microscopy methods are, in any case, not useful, and ex-situtransmission electron microscopy produces useful images but without sufficient time resolution. We propose to instead use laser Doppler vibrometry (LDV) to observe the vibration behavior of GVs. Employing interferometry, LDV offers a far better spatiotemporal resolution. While the typical GV is smaller than 1 μm, an agglomeration of GVs may be used with the LDV to produce a measurable displacement response from a controlled, acoustically delivered pressure. In this talk, we report the fundamental and first harmonic resonance frequencies of GVs and vibration to buckling and collapse at the clinically relevant frequency of 6.5 MHz. We also compare these results with predictions from classic theories of bubble and particle oscillations and finite difference-based computations.