The results further identified M1 polarization from 8.41% in the control group to 39.22% after NZCB NPs + US treatment of B16 tumor cells (Additional file 1: Fig. S24), indicating the enhanced M1 polarization of the macrophages stimulated by the SPDT-enabled cell-killing effect synergized with the enhanced STING activity contributed by the released Zn2+ and the agonist CDN [33, 34]. This evidence concerns the gene STING1 and neoplasm.