Biodegradable Bi 2 O 2 Se Quantum Dots for Photoacoustic Imaging‐Guided Cancer Photothermal Therapy

As new 2D layered nanomaterials, Bi2O2Se nanoplates have unique semiconducting properties that can benefit biomedical applications. Herein, a facile top-down approach for the synthesis of Bi2O2Se quantum dots (QDs) in a solution is described. The Bi2O2Se QDs with a size of 3.8 nm and thickness of 1.9 nm exhibit a high photothermal conversion coefficient of 35.7% and good photothermal stability. In vitro and in vivo assessments demonstrate that the Bi2O2Se QDs possess excellent photoacoustic (PA) performance and photothermal therapy (PTT) efficiency. After systemic administration, the Bi2O2Se QDs accumulate passively in tumors enabling efficient PA imaging of the entire tumors to facilitate imaging-guided PTT without obvious toxicity. Furthermore, the Bi2O2Se QDs which exhibit degradability in aqueous media not only have sufficient stability during in vivo circulation to perform the designed therapeutic functions, but also can be discharged harmlessly from the body afterward. The results reveal the great potential of Bi2O2Se QDs as a biodegradable multifunctional agent in medical applications.