The understanding of energy deposition at the cellular level when X-rays interact with the cell in the presence of exogenous atoms of medium or high atomic numbers remains incomplete, particularly when relating the physical X-ray dose deposited to the biological effects as a function of X-ray photon energy. Starting in 2006 we focused on the effect of kilovoltage X-rays on glioma cells in the presence of bismuth (Z=83). It appeared that bismuth could have a radioprotective effect, particularly following cell survival experiments with F98 cells preincubated with AguIX® nanoparticles containing an equal number of gadolinium and bismuth atoms. We thus turned to the use of nanoparticles containing a high Z element (gadolinium, gold, bismuth) coupled to a medium Z element, more specifically copper ions. The purpose of the copper is to stimulate the formation of free radicals, and possibly increase the chemical toxicity through a change in valence of the copper ions induced by the secondary electrons produced following the irradiation of the heavy element. This work is on hold since the previously used irradiator is now out of commission. Further work on the dual nature of bismuth, radiosensibilizing/radioprotective, depending on the base compound used (which is backed by a recent publication) would be of fundamental interest