The Prospects of Metal Oxide Nanoradiosensitizers: The Effect of the Elemental Composition of Particles and Characteristics of Radiation Sources on Enhancement of the Adsorbed Dose

Abstract

Nanoparticles with a high atomic number are of interest as radiosensitizers for radiation therapy of cancer. A variety of nanoparticles and radiation sources makes the challenge of selecting their optimal combinations to achieve maximum irradiation efficacy relevant. In this work, we calculated the values of the dose enhancement factors of elemental compositions of metal oxide nanoparticles (Al2O3, TiO2, MnO2, Fe2O3 and Fe3O4, NiO, GeO2, ZrO2, CeO2, Gd2O3, Tm2O3, HfO2, Ta2O5, and Bi2O3), as well as GeO2 and HfO2 doped with the rare-earth elements lanthanum or ytterbium in combination with monochromatic photons (1–500 keV) and X-ray radiation corresponding to the radiation of kilovoltage X-ray therapy machines. At a nanoparticle concentration of 10 mg/mL, the maximum values of the dose enhancement factors were from 1.03 to 2.55 for monochromatic radiation and from 1.01 to 2.33 for the studied X-ray spectra. Doping GeO2 with 20% lanthanum or ytterbium led to an increase in the maximum value of dose enhancement factors by ~10%. Doping HfO2 did not lead to significant changes in the value of dose-enhancement factors. Thus, all studied elemental compositions of nanoparticles, with the exception of Al2O3 (a dose enhancement factor ~1.02), are promising for application in kilovoltage X-ray radiotherapy. At the same time, the complex dependence of dose enhancement factors on the spectral composition of X-ray radiation requires detailed studies of the impact of irradiation conditions on the magnitude of the radiomodifying effect of nanoparticles.