: This work reports the results of the first simultaneous Monte Carlo and experimental investigation of gold nanoparticles radiosensitization within the Choroidal melanoma tumor, during continuous gamma irradiation with a Cobalt source.

Tumor phantom (Choroidal Melanoma) was defined with and without gold nanoparticles (GNPs) in two separated simulations using MCNP5 code. The dose delivered to the tumor in both simulations (with and without GNPs) was calculated and dose enhancement factor was estimated for different concentration of nanoparticles. In the in vitro phase of this study, cultured melanoma cells incubated with and without GNPs were irradiated with a cobalt source which was designed to produce a relatively homogeneous dose distribution in the plane of the cell culture slide. Cell viability was assessed a week after melanoma cells irradiation in the presence and absence of GNPs using MTT assay and the results were compared.

The results of the In Vitro phase of this study showed that after irradiation of melanoma cells in the absence of GNPs, the rate of the dead cells have increased to 10%, while by loading GNPs in the phantom this rate has accumulated to approximately 73%. The Results of the Monte Carlo phase of this work showed that the calculated dose to the tumor in the presence of 600µg GNPs was found to be increased by factor of about 3 in compare with that of in the absence of nanoparticles. Dose enhancement factor of 1.03 in the concentration of 600µg is equal to an increase of about 37.5 KeV in the amount of absorbed energy by the tumor. The comparison between these results and the reports of the experimental study, shows that such an energy change provides a suitable justification for a decrease of 63 percent in the number of the living cells for concentration of 600µg which is irradiated as compared to the irradiated sample in the absence of gold nanoparticles.

MCNP5 simulation of GNPs-loaded tumor radiotherapy has culminated in the same results as our experimental work, which can assure the patients before going under any radiation that the side effects have decreased in a great amount.