Engineering of two-in-one Fe@Eu nanoparticles through hydrothermal synthesis: bimetallic hybrids for theranostic applications

This study focuses on the synthesis of bimetallic Fe@Eu hybrid nanoparticles (NPs), combining structural and morphological characterization with an in vitro biological evaluation. By merging the superparamagnetic behavior of iron oxide nanoparticles (IONPs) with the distinctive optical properties of europium, these hybrid NPs emerge as strong candidates for a range of biomedical applications, particularly in cancer imaging and therapy. Magnetic IONPs were synthesized via co-precipitation and surface-modified with citrate to enhance colloidal stability. Europium was then introduced at varying Fe : Eu molar ratios (1 : 3, 1 : 1, and 1 : 0.25). Structural and morphological characterization confirmed the successful fabrication of the hybrids. DLS analysis demonstrated the excellent colloidal stability required for biomedical deployment. FT-IR, pXRD, and XPS verified the formation of magnetite and the successful incorporation of europium, which appeared as europium hydroxide nanorods. TEM elemental mapping further confirmed the co-existence of iron and europium within the same nanostructures. PL measurements revealed dual fluorescence capabilities, corroborated by widefield optical fluorescence microscopy, reinforcing their potential in multimodal imaging. In vitro studies showed efficient cellular internalization with minimal cytotoxicity. Mechanistic insights pointed to mild cell cycle disruption, moderate ROS generation, and apoptosis induction as part of the NPs’ biological activity.