Mitochondria-Targeted and Ultrasound-Activated Nanodroplets for Enhanced Deep-Penetration Sonodynamic Cancer Therapy

Sonodynamic therapy (SDT), a promising alternative for cancer therapy, utilizes a sonosensitizer combined with ultrasound (US) irradiation to damage tumor cells/tissues for therapeutic purposes. The ability of sonosensitizers to specifically accumulate in tumor cells/tissues could greatly influence their therapeutic efficiency. In this work, we report the use of US-activated sonosensitizer (IR780)-based nanodroplets (IR780-NDs) for SDT, which provide numerous benefits for killing cancer cells compared with traditional methods. For instance, IR780-NDs showed effective surface-to-core diffusion both in vitro and in vivo. In the presence of US, the acoustic droplet vaporization (ADV) effect significantly assisted the conveyance of IR780-NDs from the circulatory system to tumor regions, and the acoustic wave force also increased the penetration depth within tumor tissues. Furthermore, IR780-NDs possesses mitochondrial targeting capabilities, which improves the precision and accuracy of SDT delivery. During the in vitro assessment, the overproduction of reactive oxygen species (ROS) was observed following mitochondrial targeting, which rendered cancer cells more susceptible to ROS-induced apoptosis. Additionally, IR780-ND is a suitable candidate for photoacoustic and fluorescence imaging and can also enhance US imaging because of the ADV-generated bubbles, which provides the potential for SDT guidance and monitoring. Therefore, with combined modalities, IR780-NDs can be a promising theranostics nanoplatform for cancer therapy.