Synergistic effects of MnCO3@Te and X-Ray on killing breast cancer cells. Without X-Ray irradiation, cell viabilities of MDA-MB-M231 and 4T1 cells treated with different concentrations of MnCO3@Te (a), MnCO3 (b) and TeNDs (c). With different dosage of X-Ray irradiation, cell viabilities of MDA-MB-M231 (d) and 4T1 cells (g) treated with different concentrations of MnCO3@Te (calculated by Te). IC50 value of MnCO3 and MnCO3@Te (calculated by Mn) with or without X-Ray on MDA-MB-M231 cells (e) and 4T1 cells (f) after 72 h-incubation. Isobologram analysis of the synergistic antitumor effects of MnCO3@Te combined with X-Ray in MDA-MB-M231 (f) and 4T1 (i) cells. (j–k) Representative photographs of stained colonies of MDA-MB-M231 cells treated with PBS, PBS + X-Ray, TeNDs, TeNDs + X-Ray, MnCO3, MnCO3+X-Ray, MnCO3@Te and MnCO3@Te + X-Ray after 7 days.