Acoustic characterization of nano gas vesicles

Due to the lack of a proper contrast agent, the scope of molecular ultrasound imaging is restricted within blood vessels. Recently reported biogenic nano gas vesicle (NGV), 400nm by 100nm rod shape nano-bubbles encapsulated by a bilayer protein shell, may extend molecular ultrasound imaging capability and find substantial values in therapy. In this study, we investigated the fundamental acoustic characteristics, including attenuation and non-linear property of NGV. Resonance frequency was obtained by measuring the attenuation coefficient of NGV using pulse-echo system and found to be at high frequency region greater than 80MHz. By testing the non-linear property of NGV, it shows significant second harmonic frequency when sonicated by 40MHz ultrasound signal. The stability is well enhanced without significant broken for more than 6 hrs. With the advantage of nanometer size, good ultrasonic contrast and enhanced stability, it is believed to perform extravascular molecular imaging with ultrasound modality.