Biogenic Gas Vesicles for Ultrasound Imaging and Targeted Therapeutics.

Ultrasound is not only the most widely used medical imaging mode for diagnostics owing to its real-time, non-radiation, portable and low-cost merits, but also a promising targeted drug/gene delivery technique by producing a series of powerful bioeffects. The development of micron-sized or nanometer-sized ultrasound agents or delivery carriers further makes ultrasound a distinctive modality in accurate diagnosis and effective treatment. In this review, we introduce one kind of unique biogenic gas-filled protein nanostructures called gas vesicles, which present some unique characteristics beyond the conventional microbubbles. Gas vesicles can not only serve as ultrasound contrast agent with innovative imaging methods such as cross-amplitude modulation harmonic imaging, but also can further be adjusted and optimized via genetic engineered techniques. Moreover, they could not only serve as acoustic gene reporters, acoustic biosensors to monitor the cell metabolism, but also serve as cavitation nuclei and drug carrier for therapeutic purpose. We focus on the latest development and applications in the area of ultrasound imaging and targeted therapeutics, and also give a brief introduction to the corresponding mechanisms. In summary, these biogenic gas vesicles show some advantages over conventional MBs that deserve making more efforts to promote their development.