a Sensitization ability of AuNPs (5 nM) under various doses of X-ray on B16 and HepG2 cell lines, measured by MTT assay. *p < 0.05, **p < 0.01, statistically significance between IR and IR+Au treatment on B16 cells; #
p< 0.05, ##
p < 0.01, statistically significance between IR and IR+Au treatment on HepG2 cells. b Cytotoxicity of AuNPs at different concentrations on B16 and HepG2 cell lines, measured by MTT assay. Combination effect of AuNPs (5 nM) and DOX (20 nM for B16 and 200 nM for HepG2) under various doses of X-ray on B16 cells (c) and HepG2 cells (d), measured by MTT assay. *p < 0.05, **p < 0.01, statistically significance between sole (Au or DOX) treatment and combination treatment under radiation. Surviving fraction of B16 cells (e) and HepG2 cells (f) incubated with AuNPs (5 nM) or DOX (20 nM for B16 and 200 nM for HepG2) or both, under various doses of X-ray, measured by colony formation assay. “IR” was for groups with irradiation only. “IR + Au” was for groups incubated with AuNPs before irradiation. “IR + DOX” was for groups incubated with DOX before irradiation. “IR + Au + DOX” was for groups incubated with AuNPs and DOX before irradiation.