Phase-change contrast agents (PCCAs), which normally consist of nano/microscale droplets of liquid perfluorocarbons (PFCs) in an encapsulating shell, can be triggered to undergo a phase transition to the highly-echogenic gaseous state upon the input of sufficient acoustic energy. As a result of the subsequent volumetric expansion, a number of unique applications have emerged that are not possible with traditional ultrasound microbubble contrast agents. Although many studies have explored the therapeutic aspects of the PCCA platform, few have examined the potential of PCCAs for molecular imaging purposes. In this study, we demonstrate a PCCA-based platform for molecular imaging using αvβ3-targeted nanoscale PCCAs composed of low-boiling-point PFCs. In-vitro, nanoscale PCCAs adhered to target cells, could be activated and imaged with a clinical ultrasound system and produced a six-fold increase in image contrast compared to non-targeted control PCCAs and a greater than fifty-fold increase over baseline. Data suggest that low-boiling-point nanoscale PCCAs could enable future ultrasound-based molecular imaging techniques in both the vascular and extravascular space
