Further, the antitumor effect of EH@Ag2S was evaluated in vitro. EH@Ag2S cytotoxicity was investigated by standard cell counting kit-8 (CCK-8) assay. The toxicity of nano-system was first investigated, for MC38 cells and HEK-293T cells, EH@Ag2S had no obvious toxicity in the absence of US irradiation for a further 24 h incubation (Fig. ). In the presence of US irradiation with a power density of 1.0 W cm -2 , the increase of EH@Ag2S concentration produced more significant toxicity to MC38 cells. When the concentration of EH@Ag2S was 50 µg mL -1 , nearly 83% of the MC38 cells were dead (Fig. ). Further, eight controls were established: (1) PBS +US,