This present study aims to use gold as agent for cancer photo-thermal therapy depending on its optical properties of absorption of light and generation heat due to of local plasmon resonance. In this study we used gold Nano sphere with three different diameters 31 nm, 36 nm and 79 nm which its peak wavelength absorbance at range 532 nm, 535 nm and 546 nm respectively. Then in vitro prepare MDA-MB-231 tumor cell line for exposure to 450nm continuous wavelength laser for 1 minutes with different powers in this procedure MDA-MB-231 cultured divided into 4 groups, group1 incubated with media only and didn’t exposure to laser group2 incubated with media only and exposure to laser group 3 incubated with Nano gold and didn’t exposure to laser group 4 incubated with Nano gold and exposure to laser. Our results show that it could use Nano gold without cause cytotoxicity to cells and it could use as a good agent for cancer photo-thermal therapy

Gold Nano-sphere, Photo thermal therapy (PPT), Cytotoxicity, Surface Plasmon Resonance (SPR