Theranostic Gold Nanoclusters for NIR-II Imaging and Photodynamic Therapy

Fluorescence imaging in the second near-infrared window(NIR-II, 1000―1700 nm) has demonstrated tremendous promise for biomedical applications, with its extraordinarily high resolution and deep tissue penetration. Ultrasmall gold nanoclusters(AuNCs) have shown unique features for NIR-II imaging, such as photostability and biocompatibility, as compared to organic NIR-II molecules or other inorganic NIR-II nanoparticles. Here, we report the first-in-class protein-capped ultrasmall AuNCs(BSA-AuNCs, BSA=bovine serum albumin) for simultaneous NIR-II imaging and photodynamic therapy. The BSA-AuNCs show a uniform size, high quantum yield and excellent photostability, display a high accumulation and long retention in 4T1 tumor, and are used for clear imaging of blood vessels and lymph nodes. Moreover, laser irradiation of these AuNCs can rapidly trigger ROS generation, leading to effective inhibition of tumor cell growth in vitro and in vivo. This study demonstrates the feasibility of a protein-capped ultrasmall AuNCs platform for theranostic applications by combining NIR-II imaging and photodynamic cancer therapy.