Facile preparation of multifunctional uniform magnetic microspheres for T1-T2 dual modal magnetic resonance and optical imaging

Abstract Molecular imaging is of significant importance for early detection and diagnosis of cancer. Herein, a novel core-shell magnetic microsphere for dual modal magnetic resonance imaging (MRI) and optical imaging was produced by one-pot emulsifier-free emulsion polymerization, which could provide high resolution rate of histologic structure information and realize high sensitive detection at the same time. The synthesized magnetic microspheres composed of cores containing oleic acid (OA) and sodium undecylenate (NaUA) modified Fe 3 O 4 nanoparticles and styrene (St), Glycidyl methacrylate (GMA), and polymerizable lanthanide complexes (Gd(AA) 3 Phen and Eu(AA) 3 Phen) polymerized on the surface for outer shells. Fluorescence spectra show characteristic emission peaks from Eu 3+ at 590 nm and 615 nm and vivid red fluorescence luminescence can be observed by 2-photon confocal scanning laser microscopy (CLSM). In vitro cytotoxicity tests based on the MTT assay demonstrate good cytocompatibility, the composites have longitudinal relaxivity value ( r 1 ) of 8.39 mM −1  s −1 and also have transverse relaxivity value ( r 2 ) of 71.18 mM −1  s −1 at clinical 3.0 T MR scanner. In vitro and in vivo MRI studies exhibit high signal enhancement on both T 1 - and T 2 -weighted MR images. These fascinating multifunctional properties suggest that the polymer microspheres have large clinical potential as multi-modal MRI/optical probes.