Double-Emulsion Perfluorocarbon Nanodroplets for Ultrasound and Photoacoustic Image-Guided Drug Delivery and Release

Phase-change perfluorocarbon nanodroplets (PFCnDs) have shown potential for controlled, image-guided drug delivery. However, their clinical translation is limited by the poor encapsulation of hydrophilic therapeutics and unintended cargo release during ultrasound (US) or photoacoustic (PA) imaging. In this study, we present the development of double-emulsion perfluorocarbon nanodroplets (dePFCnDs) designed to encapsulate hydrophilic payloads while enabling efficient, real-time, focused ultrasound (FUS) triggered release. Cryo-transmission electron microscopy revealed that the dePFCnDs consist of a hydrophilic inner core surrounded by a perfluorocarbon layer that supports US/PA imaging. Compared to conventional single-emulsion PFCnDs, the double-emulsion structure significantly enhanced the loading efficiency tested using the fluorescent hydrophilic model drug, calcein. Furthermore, improved stability was demonstrated showing minimal calcein leakage under imaging conditions. Release studies demonstrated selective responsiveness of dePFCnDs to FUS stimulation, with negligible response to thermal or laser triggers. Optimizing focused ultrasound parameters further enhances release efficiency, enabling precise spatial and temporal control. In vitro and in vivo experiments confirmed the feasibility of utilizing real-time US/PA tracking of droplet localization, and changes in US/PA signal as a proxy for payload release. This proof-of-concept study demonstrates the potential of dePFCnDs as a hydrophilic therapeutics carrier that provides a robust, safe, and effective platform for ultrasound-mediated, image-guided delivery and release.