Investigation of the extent of DNA damage under proton irradiation in the presence of various nanoparticles of Au, Gd and I, using Geant4-DNA toolkit

Radiation therapy is one of the most effective methods in the treatment of cancer. The use of protons and light ions in radiation therapy is developing due to the different physical interactions with the photons and the application of concentrated doses in the Bragg region. However, new methods to increase the efficiency of treatment have always been considered. One is addition of nanoparticles of high-Z materials to the tissue, which while increasing the effective atomic number of the tissue, increases the effective dose during radiation therapy and causes more damage to the DNA. In this study, using the Geant4-DNA toolkit, we defined B-DNA as PDB format in the geometry. DNA damages after proton interactions in the energy range of 0.1 to 20 MeV were calculated. The number and efficiency of single-strand breaks (SSB) and double-strand breaks (DSB) have been calculated by considering direct and indirect interactions with / without the presence of nanoparticles. By comparison, it was found that the obtained results without nanoparticles are well consistent with previous studies. The results of this study show an increase of up to 15% for single-strand damage and up to 80% for double-strand breaks in the presence of gold nanoparticles. Also, the amount of DNA damage in the presence of iodine and gadolinium nanoparticles was reduced by 7% and 13% compared to gold, respectively. The results of this study show that nanoparticles can be used to improve the effectiveness of radiation therapy.