Track analysis of a synchrotron X‐ray photoelectric nanoradiator by in situ fluorescence imaging of reactive oxygen species: comparative study of gold and iron oxide nanoparticles

The emission of fluorescent X‐rays and low‐energy electrons by mid‐/high‐Z nanoparticles upon irradiation with either X‐ray photons or high‐energy ion beams is referred to as the nanoradiator effect (NRE). A track analysis of NRE was performed using reactive oxygen species (ROS) gels, to which macrophages containing gold nanoparticles (AuNPs) were attached, together with single‐cell irradiation of the intracellular nanoparticles from a microbeam of synchrotron X‐rays, and the range and distribution of OH and O2 produced were compared with those of the Fe‐nanoradiator by magnetite nanoparticles (FeONP, Fe3O4). The Au‐nanoradiator generated ROS fluorescence to a greater depth and wider angle with respect to the incident X‐rays than that of the Fe‐nanoradiator. The ROS‐oxidant fluorescence intensity ratios of OH to O2 were different for the AuNPs and FeONPs, reflecting different relative yields of electrons and fluorescent X‐rays from NRE. In the region immediately (