Phase-shifted paclitaxel-loaded multifunctional contrast agent for US/MR imaging and synergistic hyperthermal/chemotherapy of metastasis in lymph nodes.

The existing approaches used to detect a tumor-induced sentinel lymph node and treat metastasis have limitations. In this study, by encapsulating perfluoropentane (PFP), magnetic iron oxide nanoparticles (Fe 3 O 4 ) and the chemotherapy drug paclitaxel (PTX), we fabricated novel polymer nanoparticles (NPNs) that can effectively absorb heat after irradiation by near-infrared irradiation (NIR), thereby synergistically enhancing tumor therapy via a phase-shift thermoelastic expansion effect. These NPNs can be used for dual-modal ultrasound (US) and magnetic resonance (MR) imaging and to treat metastasis in lymph nodes under NIR irradiation-triggered drug delivery. The enhancement of US/MR imaging proved effective in vitro and in vivo , and NIR irradiation proved valid, promoting PTX release at the target site. A lower proliferation index and density and a higher tumor cell apoptotic index in the histopathology results confirmed the effectiveness of NPN chemotherapy for lymph nodes.