Iron oxide core oil-in-water nanoemulsion as tracer for atherosclerosis MPI and MRI imaging

Purpose: For early atherosclerosis imaging, magnetic oil-in-water nanoemulsion (NE) decorated with atheroma specific monoclonal antibody was designed for Magnetic Particle Imaging (MPI) and Magnetic Resonance Imaging (MRI). MPI is an emerging technique based on direct mapping of superparamagnetic nanoparticles which may advantageously complement MRI. Methods: NE oily droplets were loaded with superparamagnetic iron oxide nanoparticles of 7, 11 and 18 nm and biofunctionalized with atheroma specific scFv-Fc TEG4-2C antibody. Results: Inclusion of nanoparticles inside NE did not change the hydrodynamic diameter of the oil droplets, close to 180 nm, nor the polydispersity. The droplets were negatively charged (zeta=-30 mV). In vitro MPI signal was assessed by Magnetic Particle Spectroscopy (MPS). NE displayed MRI and MPS signals confirming its potential as new contrast agent. NE MPS signal increase with NPs size close to the gold standard (Resovist). In MRI, NE displayed R-2* transversal relaxivity of 45.45, 96.04 and 218.81 mM(-1) s(-1) for 7, 11 and 18 nm respectively. NE selectively bind atheroma plaque both in vitro and ex vivo in animal models of atherosclerosis. Conclusion: Magnetic NE showed reasonable MRI/MPS signals and a significant labelling of the atheroma plaque. These preliminary results support that NE platform could selectively image atherosclerosis.