Size-Dependent Ag2S Nanodots for Second Near-Infrared Fluorescence/Photoacoustics Imaging and Simultaneous Photothermal Therapy.

Ag2S nanoparticles are increasingly important in biomedicine, such as in cancer imaging. However, there has been only limited success in the exploration of theranostic Ag2S nanoparticles for photoinduced cancer imaging and simultaneous therapy. Here we report size-dependent Ag2S nanodots (NDs) with well-defined nanostructure as a theranostic agent for multimodal imaging and simultaneous photothermal therapy. The NDs are precisely synthesized through carefully controlled growth of Ag2S in hollow human serum albumin nanocages. These NDs produce effective fluorescence in second near-infrared (NIR-II) region, distinct photoacoustic intensity, and good photothermal conversion in a size-dependent manner under light irradiation, thereby generating sufficient in vivo fluorescence and photoacoustic signals as well as potent hyperthermia at tumors. Moreover, Ag2S NDs possess ideal resistance to photobleaching, effective cellular uptake, preferable tumor accumulation, and in vivo elimination, thus facilitating NIR-II fluorescence/photoacoustics imaging with both ultrasensitivity and microscopic spatial resolution and simultaneous photothermal tumor ablation. These findings provide insight into the clinical potential of Ag2S nanodots for cancer theranostics.