Synthesis and Characterization of Tb-Doped Nanoferrites

Tb3+-substituted superparamagnetic iron-oxide-based nanoparticles (NPs) that can be promising for possible multimodal drug carrier and radiotherapy are presented. These NPs were obtained using a reverse micelle template method with controlled micelle size. The atomic ratio of Tb/Fe ions was found to be very close to that expected from the stoichiometry of the reagents used. Aqueous suspensions of Tb-doped nanoferrites are emissive with emission peaks characteristic for the Tb3+ dopant. Time-resolved fluorescence decay data revealed two populations occupying inequivalent matrix sites. Above 80 K the Tb-doped nanoferrites were superparamagnetic, which is a prerequisite for their use as carriers in magnetic-field-driven targeted therapies. The incorporation of up to 15 at.% of Tb3+ in their core resulted in a decrease of magnetization. Nevertheless, this magnetization appears to be sufficient for their use as carriers in an external magnetic field, and, of equal importance, stable isotope 159Tb3+ could be replaced by radioactive 161Tb3+, yielding multimodal NPs, suitable for conjugated therapies such as radiotherapy and magnetothermal therapy, as well as targeted drug delivery.