Magnetoluminescent agents for dual MRI and time-gated fluorescence imaging

The synthesis and properties of two luminescent iron oxide nanoparticles for dual imaging by MRI and time-gated confocal microscopy are presented. These magnetoplasmonic agents consist of macrocyclic terbium complexes conjugated onto magnetite nanoparticles by a polyethylene glycol linker. Two macrocyclic terbium complexes were investigated: Tb-DOTAm-(Phen) ₃ and Tb-DOTAm-(acetylene) ₃. Both complexes display the characteristic long luminescence lifetimes of lanthanides (0.8 ms and 1.3 ms, respectively), rendering them ideal for time-gated luminescence spectroscopy and confocal imaging - a feature currently unexplored in multimodal imaging agents. Additionally, the 5 ± 1 nm magnetite nanoparticles, with their permeable PEG coating and stable dopamide anchor, render the two constructs efficient MRI contrast agents with longitudinal (r ₁) and transverse (r ₂) relaxivities of 9.8 mM ^-1 _Fe s ^-1 and 98 mM ^-1 _Fe s ^-1 at 60 MHz and 37 °C. The synthesis and characterization of Fe ₃O ₄@Tb-DOTAm-(acetylene) ₃ and Fe ₃O ₄@Tb-DOTAm-(Phen) ₃, two magnetoluminescent agents for dual imaging by MRI and confocal imaging are presented. The nanoparticles are characterized by high transverse and longitudinal relaxivities and long luminescence lifetimes ideal for time-gated spectroscopy.