Several studies show that the combination of high-Z nanoparticles and external radiotherapy leads to an increased radiation effect in tumoral cells without increasing the patient dose. The objective of this work is to develop simulation tools that allow a better understanding of radiobiology results obtained in cell irradiation studies in the presence of multi-functional nanoparticles. In these proceedings we summarize the methodology that is being developed to make realistic simulations of the irradiation of monolayer and spheroid human glioblastomas multiforme cell cultures, taking into consideration different concentrations of the gold nanoparticles. Based on these simulations, microdosimetric dose distributions will be obtained as well as the temporal distribution of G-values yields for different reactive oxygen species. The microdosimetric distributions in cells will be used to predict cell survival fractions, using mathematical models of the biological effects of radiation. The results obtained in the simulations will be compared with the biological in vitro and in vivo experimental results.