Perfluorocarbon Nanodroplets with Deep Tumor Penetration and Controlled Drug Delivery for Ultrasound/Fluorescence Imaging Guided Breast Cancer Therapy.

Some impediments, including insufficient drug release, poor tumor penetration, and lack of real-time imaging guidance, still limited the therapeutic efficiency of nanotechnology-based drug delivery systems. Here, light-responsive perfluoropentane (PFP) based nanodroplets as doxorubicin (DOX) nanocarriers that could achieve deep tumor delivery under multimodal imaging guidance were developed. Triggered by laser irradiation, the liquid PFP with low boiling point could go through small-to-big size change and liquid-to-gas phase transformation. At the same time, the accompanied cavitation effect led to not only the disruption of dense extracellular matrix for deep penetration but also the disruption of endo-/lysosome for nucleus delivery of released DOX. Furthermore, different from many imaging approaches which were always "on", only upon laser stimulation could the nanodroplets act as ultrasound/fluorescence probes due to the echogenic PFP bubbles and the recovered fluorescence of DOX itself after released from nanodroplets, which was highly desirable to indicate the DOX state in real time. Therefore, such PFP nanodroplets with phase/size tunable properties enable site-specific drug delivery efficiently and exhibit their potent in cancer theranostics.