Rare earth doped gadolinium oxide nanoprobes as MRI-FI dual mode contrast agents: implications for developing theranostics

Magnetic-based theranostic nanoparticle (MBTN) systems containing magnetic nanoparticles (MNPs) are emerging as useful tools for diagnostic imaging, therapeutic targeting and treating various complex diseases including cancer. MBTN systems are particularly gaining popularity because of their unique ability to be used in magnetic resonance imaging (MRI), magnetic targeting, hyperthermia, and controlled drug release. Further, expanding research on nanomaterials also has triggered development of multiple molecular imaging (or multi-modal contrast) nanoprobes as a new approach in the biomedical/diagnostic imaging. Intensive research driven in this direction has revealed fluorescent magnetic nanoparticles as brilliant MRI-FI (Magnetic Resonance Imaging-Fluorescence Imaging) dual mode contrast agents (CAs). Various research groups have developed rare earth-doped gadolinium oxide (Gd₂O₃) nanoparticles (NPs) as MRI-FI dual mode CAs due to high magnetic relaxivity of host Gd³⁺ ions and the attractive optical properties of dopant ions, all arising from their 4f electrons. However, owing to large surface to volume ratio and high surface hydrophobicity, gadolinium based nanomaterials are reported to suffer metal-ion accumulation and biocompatibility issues along with other potential health risks. The present study involves polyols approach to synthesise Gadolinium based nanoparticles doped with Europium and Terbium (Eu_x:Gd_2-xO₃ and Tb_x:Gd_2-xO₃) with doping concentrations varying from 0.5 to 10 M %, to investigate their efficacy as MRI-FI agent