Phase-Shifted PFH@PLGA/Fe<sub>3</sub>O<sub>4</sub> Nanocapsules for MRI/US Imaging and Photothermal Therapy with near-Infrared Irradiation

Photothermal therapy (PTT) utilizes photothermal conversion reagents to generate heat energy from absorbed light to effectively treat various malignant diseases. This approach has attracted broad and increasing interest in cancer treatment. Near-infrared (NIR)-induced PTT is particularly attractive because of its minimal absorbance by normal tissue and relatively deep tissue penetration. To improve the efficacy of PTT, we have developed nanocapsules encapsulating superparamagnetic iron oxide (Fe<sub>3</sub>O<sub>4</sub>) as synergistic agents for NIR-induced PTT. In this study, phase-shift and NIR photoabsorbing poly­(lactic-<i>co</i>-glycolic acid) (PLGA) nanocapsules (perfluorohexane (PFH)@PLGA/Fe<sub>3</sub>O<sub>4</sub>) were fabricated for MRI/US dual-modal imaging-guided PTT. The multifunctional nanocapsules can be used not only to increase the local tumor temperature by absorbing the NIR energy but also as bimodal contrast agents for both MRI and US imaging. Such nanocapsules can be converted into microbubbles under NIR irradiation, which produces excellent contrast for US imaging and enhanced cancer ablation. We refer to the nanocapsule phase transition process induced by the infrared lamp as NIR radiation droplet vaporization (NIRDV).