Gold nanoparticles (GNPs) due to high atomic number are applied in combination with radiation to obtain dose enhancement in tumors. Lymphoma is the most common malignant orbital tumor in adults that represents good prognosis with radiation. The main purpose of this work is to evaluate cytotoxicity potential and dose enhancing effects of different concentrations of GNPs under cobalt-60 on Burkitt's lymphoma cell line (Ramos) in vitro.

At first, the dose enhancement effects of GNPs on Burkitt's lymphoma were examined using the Monte Carlo simulation technique. Dose enhancement factor (DEF) which is defined as the ratio of the dose in a particular region of a tissue when GNPs are present to the same factor in the absence of such substances were calculated and compared for different concentrations. Cultivated Ramos cells were incubated with different concentrations of GNPs (200, 150, 100, 50 and 25µg/µl) of 50 nm in diameters in conjunction with cobalt-60. Ramos cells incubated without GNPs were used as controls. Viability of the cells was measured 24h, 72h and 1 week after irradiation using standard colorimetric MTT assay.

Compared to controls, the results indicated that with increasing concentration of GNPs a significant decrease of viability and growth rate of Ramos cell was observed. Subsequently, MTT assay demonstrated that irradiation of Ramos cells with GNPs resulted in enhanced radiation sensitivity with increasing concentration of GNPs.

These findings revealed that both cytotoxicity and radiation sensitivity of Ramos cells are significantly increased with increasing concentration of GNPs. It can be proposed that if an orbital lymphoma is loaded with these nanoparticles of proper concentration, a higher absorption dose of radiation by the tumor may occur in a short duration. The results of our study suggest the clinical potential of GNPs for improvement of ocular lymphoma radiotherapy.