Cytotoxicity of AuPt NCs against (a) FHC, (b) HCT116, (c) SW480, and (d) SW620 cells after 3, 18, and 24 h of incubation: data were considered significant when * p < 0.05 versus control. The concentrations of HCT116, SW480, and SW620 cells considered optimal were marked in red.