Ultrasmall Cu_2-xS nanodots for highly efficient photoacoustic imaging-guided photothermal therapy

Monodisperse, ultrasmall (<5 nm) Cu_2-xS nanodots (u-Cu_2-xS NDs) with significantly strong near-infrared absorption and conversion are successfully demonstrated for effective deep-tissue photoacoustic imaging-guided photothermal therapy both in vitro and in vivo. Owing to ultrasmall nanoparticle size and high water dispersibility as well as long stability, such nanodots possess a prolonged circulation in blood and good passive accumulation within tumors through the enhanced permeability and retention effect. These u-Cu_2-xS NDs have negligible side effects to both blood and normal tissues according to in vivo toxicity evaluations for up to 3 months, showing excellent hemo/histocompatibility. Furthermore, these u-Cu_2-xS NDs can be thoroughly cleared through feces and urine within 5 days, showing high biosafety for further potential clinical translation. This novel photoacoustic imaging-guided photothermal therapy based on u-Cu_2-xS NDs composed of a single component shows great prospects as a multifunctional nanoplatform with integration and multifunction for cancer diagnosis and therapy.