1P-426 : pH-activatable bubble-generating nanoparticles for ultrasound imaging and tumor therapy

Ultrasound (US) is a real-time and non-invasive imaging modality that is widely available to visualize anatomical structures of tissues and organs. Conventionally, gas-filled microparticles have been used as contrast agents for ultrasound imaging. However, these types of contrast agents have limitations for intravenous applications particularly in tumor imaging due to low permeation to tumor tissues. In this work, we have developed carbon dioxide-generating mineralized nanoparticles that can form nanobubbles for US imaging of tumors. We demonstrated the generation of carbon dioxide bubbles from the calcium carbonate (CaCO3) mineralized nanoparticles in tumoral acidic pH. To demonstrate US imaging of a tumor, we administered an intratumoral injection of the hybrid nanoparticles to tumor-bearing nude mice and compared US images between pre- and post-injection. The tumor volume was also monitored in tumor-bearing nude mice for antitumor efficacy of DOX loaded CaCO3 mineralized hybrid nanoparticles.