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

AgS nanoparticles are increasingly important in biomedicine, such as in cancer imaging. However, there has been only limited success in the exploration of theranostic AgS nanoparticles for photoinduced cancer imaging and simultaneous therapy. Here we report size-dependent AgS 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 AgS 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, AgS 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 AgS nanodots for cancer theranostics.