Neuropeptide Y Y1 receptor-mediated biodegradable photoluminescent nanobubbles as ultrasound contrast agents for targeted breast cancer imaging.

Targeted molecular imaging has attracted great attention in cancer diagnosis and treatment. However, most clinically used ultrasound contrast agents (UCAs) are non-targeted microbubbles seldom used for cancer imaging. Here, we fabricated fluorescent nanobubbles (NBs) by encapsulation of liquid tetradecafluorohexane (C6F14) within biodegradable photoluminescent polymers (BPLPs) through an emulsion-evaporation process and conjugation of PNBL-NPY ligand for specific targeting of Y1 receptors overexpressed in breast tumors. The developed PNBL-NPY modified NBs were uniform in size with good dispersibility and photostability, presenting good ultrasound enhancement. Further, in vitro and in vivo results indicated that the fabricated NBs exhibit high affinity and specificity to Y1 receptor-overexpressing breast cancer cells and tumors with minimal toxicity and damage to organs. Our developed PNBL-NPY-modified NBs are novel targeted UCAs for safe, efficient and specific targeted breast cancer imaging, and may provide a new nanoplatform for early cancer diagnosis and treatment in the future.