Synthesis and characterization of Gd3+- and Tb3+-doped iron oxide nanoparticles for possible endoradiotherapy and hyperthermia

A large range of nanoscale superparamagnetic materials has been under scrutiny from the point of view of their potential theranostic, multimodal applications. In this paper we have investigated the effect of replacing Fe3+ cations with Gd3+ and Tb3+ in the core of the superparamagnetic iron oxide nanoparticles in search for the optimum level of magnetic core doping with these lanthanides. We have found that the presence of Gd3+ and Tb3+ up to 2.5% at. does not alter significantly the crystallographic structure of such nanoferrites and does not compromise the magnetic properties of doped nanoparticles. The doping level, though relatively small, exceeds the levels of currently used radiopharmaceuticals, where only few radionuclides can be incorporated in a single radiotherapeutic molecule. This new type of multifunctional nanoparticles can be used not only as drug carriers or in magnetic hyperthermia, but also in the so-called endoradiotherapy. The latter feature can be easily implemented upon the replacement of “cold” ions of Tb3+ and Gd3+ in the superparamagnetic core with their isotopes emitting soft β− radiation suitable for the internal radiotherapy, localized directly within the tumor. Therefore, these nanoparticles can be used simultaneously in targeted drug delivery, hyperthermia and radiotherapy.