Monte Carlo-based numerical assessment of metal and metal oxide nanoparticle parameters on cellular dose enhancement in proton therapy

Abstract

Proton therapy is an effective cancer treatment due to its precise dose distribution and the presence of the Bragg peak. The incorporation of high-Z nanoparticles has emerged as a promising strategy to further enhance local dose deposition in tumor cells. This study aims to evaluate the dose enhancement effect of metal and metal oxide nanoparticles in cellular environments under proton irradiation. Monte Carlo simulations were performed using the GEANT4 toolkit with the GEANT4-DNA extension to model proton interactions at the microscopic scale. The influence of nanoparticle material (gold, iron oxide, and hafnium oxide), concentration (10-90 mg.ml-1), and size (5-25 nm) on the dose enhancement ratio in the nucleus and cytoplasm of a single cell was investigated. Results show that the dose enhancement ratio (DER) increased linearly with nanoparticle concentration, while increasing nanoparticle size caused a nonlinear decrease in the DER. Among the studied nanoparticles, gold nanoparticles showed the highest dose enhancement due to their higher atomic number and density. Nanoparticle type, size, and concentration are critical factors for maximizing dose enhancement in proton therapy, with gold nanoparticles offering the greatest potential to increase therapeutic efficacy.